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It is proposed that the coincidence of higher brightness and upward electric current observed by Janvier et al. during a flare indicates electron acceleration by field-parallel potential drops sustained by extremely strong field-aligned currents of order 104 A m−2. A few consequences are discussed here.

This work reports a reversible braking system for micromotors that can be controlled by small temperature changes (≈5 °C). To achieve this, gated‐mesoporous organosilica microparticles are internally loaded with metal catalysts (to form the motor) and the exterior (partially) grafted with thermosensitive bottle‐brush polyphosphazenes to form Janus particles. When placed in an aqueous solution of H2O2 (the fuel), rapid forward propulsion of the motors ensues due to decomposition of the fuel. Conformational changes of the polymers at defined temperatures regulate the bubble formation rate and thus act as brakes with considerable deceleration/acceleration observed. As the components can be easily varied, this represents a versatile, modular platform for the exogenous velocity control of micromotors., A robust and easily tunable micromotor platform is reported, based on Janus gated‐mesoporous organosilica microparticles with reversible, external responsive braking systems using bottle‐brush polyphosphazenes to control acceleration/deceleration by small changes in temperature.

Background COVID-19 transmission rates in South Asia initially were under control when governments implemented health policies aimed at controlling the pandemic such as quarantines, travel bans, and border, business, and school closures. Governments have since relaxed public health restrictions, which resulted in significant outbreaks, shifting the global epicenter of COVID-19 to India. Ongoing systematic public health surveillance of the COVID-19 pandemic is needed to inform disease prevention policy to re-establish control over the pandemic within South Asia. Objective This study aimed to inform public health leaders about the state of the COVID-19 pandemic, how South Asia displays differences within and among countries and other global regions, and where immediate action is needed to control the outbreaks. Methods We extracted COVID-19 data spanning 62 days from public health registries and calculated traditional and enhanced surveillance metrics. We use an empirical difference equation to measure the daily number of cases in South Asia as a function of the prior number of cases, the level of testing, and weekly shifts in variables with a dynamic panel model that was estimated using the generalized method of moments approach by implementing the Arellano–Bond estimator in R. Results Traditional surveillance metrics indicate that South Asian countries have an alarming outbreak, with India leading the region with 310,310 new daily cases in accordance with the 7-day moving average. Enhanced surveillance indicates that while Pakistan and Bangladesh still have a high daily number of new COVID-19 cases (n=4819 and n=3878, respectively), their speed of new infections declined from April 12-25, 2021, from 2.28 to 2.18 and 3.15 to 2.35 daily new infections per 100,000 population, respectively, which suggests that their outbreaks are decreasing and that these countries are headed in the right direction. In contrast, India’s speed of new infections per 100,000 population increased by 52% during the same period from 14.79 to 22.49 new cases per day per 100,000 population, which constitutes an increased outbreak. Conclusions Relaxation of public health restrictions and the spread of novel variants fueled the second wave of the COVID-19 pandemic in South Asia. Public health surveillance indicates that shifts in policy and the spread of new variants correlate with a drastic expansion in the pandemic, requiring immediate action to mitigate the spread of COVID-19. Surveillance is needed to inform leaders whether policies help control the pandemic.

Background The COVID-19 pandemic has placed unprecedented stress on economies, food systems, and health care resources in Latin America and the Caribbean (LAC). Existing surveillance provides a proxy of the COVID-19 caseload and mortalities; however, these measures make it difficult to identify the dynamics of the pandemic and places where outbreaks are likely to occur. Moreover, existing surveillance techniques have failed to measure the dynamics of the pandemic. Objective This study aimed to provide additional surveillance metrics for COVID-19 transmission to track changes in the speed, acceleration, jerk, and persistence in the transmission of the pandemic more accurately than existing metrics. Methods Through a longitudinal trend analysis, we extracted COVID-19 data over 45 days from public health registries. We used an empirical difference equation to monitor the daily number of cases in the LAC as a function of the prior number of cases, the level of testing, and weekly shift variables based on a dynamic panel model that was estimated using the generalized method of moments approach by implementing the Arellano–Bond estimator in R. COVID-19 transmission rates were tracked for the LAC between September 30 and October 6, 2020, and between October 7 and 13, 2020. Results The LAC saw a reduction in the speed, acceleration, and jerk for the week of October 13, 2020, compared to the week of October 6, 2020, accompanied by reductions in new cases and the 7-day moving average. For the week of October 6, 2020, Belize reported the highest acceleration and jerk, at 1.7 and 1.8, respectively, which is particularly concerning, given its high mortality rate. The Bahamas also had a high acceleration at 1.5. In total, 11 countries had a positive acceleration during the week of October 6, 2020, whereas only 6 countries had a positive acceleration for the week of October 13, 2020. The TAC displayed an overall positive trend, with a speed of 10.40, acceleration of 0.27, and jerk of –0.31, all of which decreased in the subsequent week to 9.04, –0.81, and –0.03, respectively. Conclusions Metrics such as new cases, cumulative cases, deaths, and 7-day moving averages provide a static view of the pandemic but fail to identify where and the speed at which SARS-CoV-2 infects new individuals, the rate of acceleration or deceleration of the pandemic, and weekly comparison of the rate of acceleration of the pandemic indicate impending explosive growth or control of the pandemic. Enhanced surveillance will inform policymakers and leaders in the LAC about COVID-19 outbreaks.

A ‘condensate load’ (condensate in % of a totally full cylinder) over 1% accumulated inside the dryer cylinders of a paper machine is likely to produce a drive overload, eventually increasing the acceleration time or even producing an overload trip. This paper proposes and evaluates a confident online condensate estimation algorithm that gives updated information at preset speeds and when the transition to the rimming stage is detected. The experimental evaluation performed on a 500 mm diameter cylinder, with condensate load between 0.5% up to 25%, confirmed the ability of the algorithm to give accurate estimations within 0.5% intervals of condensate loads. The developed algorithm is a useful tool for the operators, allowing them to take the appropriate decisions according to the severity of the condensate accumulation detected.

When humans are about to manipulate an object, our brains use visual cues to recall an internal representation to predict its weight and scale the lifting force accordingly. Such a long-term force profile, formed through repeated experiences with similar objects, has been proposed to improve manipulative performance. Skillful object manipulation is crucial for many animals, particularly those that rely on tools for foraging. However, despite enduring interest in tool use in non-human animals, there has been very little investigation of their ability to form an expectation about an object’s weight. In this study, we tested whether wild chimpanzees use long-term force profiles to anticipate the weight of a nut-cracking hammer from its size. To this end, we conducted a field experiment presenting chimpanzees with natural wooden hammers and artificially hollowed, lighter hammers of the same size and external appearance. We used calibrated videos from camera traps to extract kinematic parameters of lifting movements. We found that, when lacking previous experience, chimpanzees lifted hollowed hammers with a higher acceleration than natural hammers (overshoot effect). After using a hammer to crack open one nut, chimpanzees tuned down the lifting acceleration for the hollowed hammers, but continued lifting natural hammers with the same acceleration. Our results show that chimpanzees anticipate the weight of an object using long-term force profiles and suggest that, similarly to humans, they use internal representations of weight to plan their lifting movements. Electronic supplementary material The online version of this article (10.1007/s10071-017-1144-0) contains supplementary material, which is available to authorized users.

BackgroundOver the past few years, the world has witnessed an unprecedented growth in smartphone use. With sensors such as accelerometers and gyroscopes on board, smartphones have the potential to enhance our understanding of health behavior, in particular physical activity or the lack thereof. However, reliable and valid activity measurement using only a smartphone in situ has not been realized. ObjectiveTo examine the validity of the iPod Touch (Apple, Inc.) and particularly to understand the value of using gyroscopes for classifying types of physical activity, with the goal of creating a measurement and feedback system that easily integrates into individuals’ daily living. MethodsWe collected accelerometer and gyroscope data for 16 participants on 13 activities with an iPod Touch, a device that has essentially the same sensors and computing platform as an iPhone. The 13 activities were sitting, walking, jogging, and going upstairs and downstairs at different paces. We extracted time and frequency features, including mean and variance of acceleration and gyroscope on each axis, vector magnitude of acceleration, and fast Fourier transform magnitude for each axis of acceleration. Different classifiers were compared using the Waikato Environment for Knowledge Analysis (WEKA) toolkit, including C4.5 (J48) decision tree, multilayer perception, naive Bayes, logistic, k-nearest neighbor (kNN), and meta-algorithms such as boosting and bagging. The 10-fold cross-validation protocol was used. ResultsOverall, the kNN classifier achieved the best accuracies: 52.3%–79.4% for up and down stair walking, 91.7% for jogging, 90.1%–94.1% for walking on a level ground, and 100% for sitting. A 2-second sliding window size with a 1-second overlap worked the best. Adding gyroscope measurements proved to be more beneficial than relying solely on accelerometer readings for all activities (with improvement ranging from 3.1% to 13.4%). ConclusionsCommon categories of physical activity and sedentary behavior (walking, jogging, and sitting) can be recognized with high accuracies using both the accelerometer and gyroscope onboard the iPod touch or iPhone. This suggests the potential of developing just-in-time classification and feedback tools on smartphones.

With the rapid development of vehicle information systems, liquid crystal displays (LCDs) have been widely used to enhance information experience. A linear vibration motor is usually placed behind the LCD to provide sufficient haptic feedback. A linear vibration motor with a large permanent magnet causes massive flux leakage around the display. As a result, it may cause unpredictable harm to people with implanted medical devices. Therefore, in this paper, a novel magnetic circuit design of a slim-width type linear vibration motor is introduced to reduce the static magnetic flux leakage. The haptic performance of the slim-width type linear vibration motor was analyzed using the electromagnetic-mechanical coupling method. Three types of experimental results were obtained to verify the analysis results. In conclusion, compared to the prototype motor, the slim-width type linear vibration motor proposed in this paper exhibits significant flux leakage reduction of 94.01% and 96.34% at the measuring positions. Furthermore, the slim-width type linear vibration motor exhibits an acceleration similar to that of the prototype motor.

The recent development in the Slovak economy erased a significant competitive advantage of manufacturing – low labour cost. The paper analyses the driving factors of rising unit labour costs in the manufacturing sector. The paper aims to explain why the unexpectedly rapid loss of traditional competitive advantage took place in the group of V4 countries and why this phenomenon was particularly pronounced in Slovakia. The paper identifies the driving factors that caused a strong increase in labour costs in addition to factors that also caused a slowdown in productivity growth. The decomposition of ULC dynamics has shown that the primary problem in the case of Slovakia is a very significant slowdown in labour productivity growth. Especially, from a marginal perspective, the components of gross value added developed strongly in favour of increasing compensations of employees. The decrease in the working-age population represented a significant driving force of increasing labour cost (wages) along with a halt in productivity growth caused by relatively low investment rate and absence of convergence in capital-to-labour ratio. Such development was identified in all V4 countries; however, the least favourable trend took place in Slovakia.

Investigations of large commercial aircraft impact effect on nuclear power plant (NPP) buildings have been drawing extensive attentions, particularly after the 9/11 event, and this paper aims to numerically assess the damage and vibrations of NPP buildings subjected to aircrafts crash. In Part I of present paper, two shots of reduce-scaled model test of aircraft impact on NPP were conducted based on the large rocket sled loading test platform. In the present part, the numerical simulations of both scaled and prototype aircraft impact on NPP buildings are further performed by adopting the commercial program LS-DYNA. Firstly, the refined finite element (FE) models of both scaled aircraft and NPP models in Part I are established, and the model impact test is numerically simulated. The validities of the adopted numerical algorithm, constitutive model and the corresponding parameters are verified based on the experimental NPP model damages and accelerations. Then, the refined simulations of prototype A380 aircraft impact on a hypothetical NPP building are further carried out. It indicates that the NPP building can totally withstand the impact of A380 at a velocity of 150 m/s, while the accompanied intensive vibrations may still lead to different levels of damage on the nuclear related equipment. Referring to the guideline NEI07-13, a maximum acceleration contour is plotted and the shock damage propagation distances under aircraft impact are assessed, which indicates that the nuclear equipment located within 11.5 m from the impact point may endure malfunction. Finally, by respectively considering the rigid and deformable impacts mainly induced by aircraft engine and fuselage, an improved Riera function is proposed to predict the impact force of aircraft A380.

Due to their high efficiency and low ‎cost, electrostatic electron accelerators with a moderate energy, are used in the industry. In an electrostatic accelerator, the acceleration tube plays the role of dividing ‎the potential of the high-voltage terminal so that it accelerates the beam incrementally in a straight line. In this ‎paper, an acceleration tube for a Dynamitron accelerator with a voltage of 500 kV is designed by CST Studio ‎Suite software. In this design, an electron gun with flat cathode, and a current of 50 mA was used. In order to ‎extract the beam from the electron gun, two filters are used: electrodes and the lens electrode, with voltages of 495 and ‎‎481 kV, respectively; besides for electron acceleration, 13 electrodes with a potential step of 37 kV have been ‎designed. To hold the electrodes and prevent electrical discharges between the electrodes, insulating ‎sheets made of Pyrex are used. At the end of the acceleration tube, a 50mA beam current, a waist radius of less than 0.5 ‎mm, a 73nm radian emittance, and a 0.15μperv beam were obtained. The dimensions of the acceleration tube ‎and the results of investigating the change in the radius of the electrodes, the displacement and deviation of ‎the angles of the first electrode relative to the axis of the acceleration tube are presented in this paper‎.‎

This paper investigates the influence of rotor coaxiality error on spindle accuracy under different operating conditions in the precision hydrostatic spindle with a mid-thrust bearing structure. Firstly, a linearized model of rotor dynamics equation with five degrees-of-freedom is established based on Newton’s law of motion and angular momentum principle. Then, by solving the Reynolds equation and the flow continuity equation using the mathematical perturbation method, the steady and transient pressure distribution functions of the hydrostatic bearings are obtained; subsequently, the stiffness and damping coefficient matrices of the spindle are determined. Furthermore, the linearized stiffness and damping coefficients are substituted into the rotor dynamics equation to obtain the instantaneous acceleration of the rotor, and the motion trajectory of the rotor is solved iteratively by the Euler method. Finally, the paper studies the influences of different rotor coaxiality, rotating speed, cutting load, oil supply pressure, and oil film clearance on dynamic characteristics, amplitude amplification factor, and radial runout of the spindle by computer simulation. The simulation results show that the spindle runout is more sensitive to rotor coaxiality error and oil film clearance.

The present article outlines the core technologies needed to realize the Hyperloop transportation system (HTS). Currently, the HTS vacuum tube train concept is viewed as the fastest way to cross the earth’s surface. However, the concept has not yet been demonstrated for subsonic or near-sonic speeds in large-scale implementations. Among the challenging technical areas are the tube’s depressurization, the capsule’s air resistance, and choked flows occurring around the capsule. There is also a need for effective levitation and propulsion solutions compatible with the velocities being proposed. Moreover, several conflicting objectives have been identified in the HTS design. It is highlighted that the tubes should be wide enough to lower the capsule’s drag forces but that a large-sized tube comes at the expense of higher operational energy costs and infrastructure investments. Another struggle is aiming at a low-cost passive track design and, and at the same time, a lightweight vehicle. One technical path is to turn the whole guideway into an electric propulsor, arriving at a ’lightweight capsule solution’ (LCS). Alternatively, the vehicle could be transformed into a ’modified airplane’ that stores massive amounts of onboard energy, yielding an energy-autonomous ’low infrastructure solution’ (LIS). In a case study, it is shown that even LIS technology is compatible with short-haul flights (1500km) but that it requires an energy reservoir of about 30% of the capsule’s overall mass. Results and discussions presented in this paper are supported by analytical predictions with parameters or input data either supported by referred simulations or experiments. In general, the paper aims to open up the discussion, provide a sufficient understanding of the Hyperloop field’s multidisciplinary aspects, and establish a foundation for further investigations. In the end, new research tasks have been defined, which have the potential to go beyond the state of current knowledge. This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/

There is an increasing demand in real-time imagery applications such as rapid response to disaster rescue and security screening to name a few. The throughput of a radar imaging system is mainly controlled by two parameters; data acquisition time and signal processing time. To minimize the data acquisition time, various methods are being tried and tested by researchers worldwide. Among them is the computational imaging (CI) technique, which relies on using coded apertures to encode the radar back-scattered measurements onto a set of spatio-temporarily incoherent radiation patterns. Such a CI-based imaging approach eliminates the requirement for a raster scan and can substantially simplify the physical hardware architecture. Equally important is the processing time needed to retrieve the scene information from the coded back-scattered measurements. In CI, the simplification in the hardware layer comes at the cost of increased complexity in the signal processing layer due to the indirect mapping and compression of the scene information through the spatio-temporally incoherent transfer function of the coded apertures. To address this particular challenge, this paper presents a hardware-based solution for CI signal processing using a Field Programmable Gate Array (an Xilinx Virtex-7 (XC7VX485T) FPGA chip) architecture. In particular, the proposed method consists of calculating the CI sensing matrix using the FPGA chip and storing it on the FPGA platform for image reconstruction. For the adjoint operation, the calculated sensing matrix is applied on the measured back-scattered waves from the target object. We demonstrate that the FPGA based calculation can reach 21.9 times faster speed than conventional brute-force solutions.

Knocking is an unwanted behavior that is affected by the intake manifold temperature. This paper demonstrates through simulation how nonlinear Model Predictive Control design could be used as a reference governor for the control of the throttle position, with a soft constraint on intake manifold temperature. The implementation is able to suppress the peak temperature during an acceleration by slowing down the pressure build-up. Because of the usually slow dynamics of the temperature sensors, the paper proposes an Extended Kalman Filter implementation that uses a transient detection to decide whether to rely on the sensor feedback or the model.

Due to the absence of power demands and yet effective performances, the semi-active tuned mass dampers (STMDs) have been broadly investigated. However, there is still a gap between the theoretical simulations and practical implementation of controlled tuned mass dampers. Moreover, using displacement and velocity sensors make such control systems less cost-effective, less reliable, and more complex. In this paper, the acceleration-based ground-hook semi-active control (ABGH) was proposed for an electromagnetic regenerative tuned mass damper (ERTMD). In this manner, a prototype of a compact back iron-based ERTMD was manufactured. The concept of a controllable system with switched transistor was utilized for the proposed ERTMD. Comparative simulations between the controlled and passive ERTMD was conducted and then validated by experimental results of the ERTMD prototype implemented in a protected mass test-bench similar to a typical vehicle unsprung mass. This paper concluded that the proposed control policy can be utilized for the ERTMD to increase the regenerative ability of the fabricated ERTMD under random excitations.

The paper presents the results of research consisting in acceleration of a diesel engine powered by diesel and hydrogen. The test stand included a diesel engine 1.3 Multijet, hydrogen cylinders and measuring equipment. Empirical tests included engine testing at idle and at specified speeds on a chassis dynamometer, vehicle acceleration in selected gears from specified initial values of engine revolutions was also tested.. Selected parameters of the diesel fuel combustion and injection process were calculated and analyzed. The paper is a preliminary attempt to determine the possibility of co-power supply to diesel and hydrogen engines.

Over time, the weapons have been based on mechanical energy (bows, catapults) and chemical energy (guns, missiles), however, at the moment, more and more weapons are designed using electromagnetic energy (railgun, coilgun). The focus of this paper is to obtain the desired muzzle velocities of a projectile according to the existent current. In the first part of the paper, the railgun and coilgun design are presented along with their most important advantages. Based on these observations, a new design of an electromagnetic launch system is presented. Next, Maxwell interactive software package was used that applies the finite element method (FEM) to analyze and solve 3D electromagnetic field problems in order to analyze the variation of acceleration force, speed in time. All simulation data shows that this design has a great potential, because of the adaptability to different applications.

K.V. Soshin1,2, D.P. Nikolaev2, S.A. Gladilin2, E.I. Ershov2 1Moscow Institute of Physics and Technology, Dolgoprudny, Russian Federation 2Institute for Information Transmission Problems (Kharkevich Institute), Moscow, Russian Federation E-mails: soshin.kv@phystech.edu, dimonstr@iitp.ru, gladilin@iitp.ru, ershov@iitp.ru. Константин Витальевич Сошин, студент бакалавриата, кафедра проблем передачи информации и анализа данных, Московский физико-технический институт (НИУ) (г. Долгопрудный, Российская Федерация); стажер-исследователь, Институт проблем передачи информации им. А.А. Харкевича (г. Москва, Российская Федерация), soshin.kv@phystech.edu. Дмитрий Петрович Николаев, кандидат физико-математических наук, заместитель директора по научной работе, Институт проблем передачи информации им. А.А. Харкевича (г. Москва, Российская Федерация), dimonstr@iitp.ru. Сергей Александрович Гладилин, кандидат физико-математических наук, старший научный сотрудник, Институт проблем передачи информации им. А.А. Харкевича (г. Москва, Российская Федерация), gladilin@iitp.ru. Егор Иванович Ершов, кандидат физико-математических наук, старший научный сотрудник, Институт проблем передачи информации им. А.А. Харкевича (г. Москва, Российская Федерация), ershov@iitp.ru. In this paper, we propose an algorithm for fast approximate calculation of the sums over arbitrary segments given by a pair of pixels in the image. Using the results of intermediate calculations of the fast Hough transform, the proposed algorithm allows to calculate the sum over arbitrary line segment with a logarithmic complexity depending on the linear size of the original image (also called fast discrete Radon transform or Brady transform). In this approach, the key element of the algorithm is the search for the dyadic straight line passing through two given pixels. We propose an algorithm for solving this problem that does not degrade the general asymptotics. We prove the correctness of the algorithm and describe a generalization of this approach to the three-dimensional case for segments of straight lines and of planes. В работе предложен алгоритм быстрого приближенного вычисления на изображении сумм по произвольным отрезкам, задаваемым парой пикселей. Используя результаты промежуточных вычислений быстрого преобразования Хафа, предложенный алгоритм позволяет рассчитать сумму по произвольному отрезку линии с логарифмической сложностью, зависящей от линейного размера исходного изображения. Предподсчет реализован как модификация алгоритма Брейди быстрой суммации по диадическим аппроксимациям прямых. При таком подходе ключевым элементом алгоритма является поиск диадической прямой, проходящей через два данных пикселя. В работе предложен алгоритм решения этой задачи, не ухудшающий общую асимптотику, для него доказана корректность. Также в работе описывается обобщение этого подхода на трехмерный случай для отрезков и для сегментов плоскостей. The team of authors is grateful to A.P. Terekhin for his help in preparing wonderful illustrations for this paper, as well as to A.V. Savchik for valuable advices on how to simplify the proof of Theorems.

The real-time response and accuracy of the attitude (i.e., roll and pitch) estimation from low-cost inertial measurement unit (IMU) have become the key issues restricting related applications. This paper proposes a robust attitude estimation scheme which can perform well under dynamic conditions. When only accelerometers are used to calculate and correct the attitude, the external acceleration becomes the main source of attitude estimation errors. Moreover, the truncation error in the linearization process of the nonlinear system also affects the attitude estimation. As our first contribution, the external acceleration is modeled as a first-order Gauss Markov model, and its value is calculated under the indirect Kalman filter (IKF) framework. The measurement noise covariance matrix of the IKF is adaptively adjusted to enhance its robustness and reduce the negative impact caused by inaccurate modeling. In the second part of our work, the two-step cascade filter method is used for attitude estimation. The attitude obtained from the gravity field based on the gradient descent (GD) algorithm shows fast response capabilities, and hence, it is embedded as a measurement in the IKF by using the chain-derivation rule. The truncation error introduced into the linearization process of the nonlinear system is effectively avoided. Both simulation and experiments are carried out to verify the feasibility and accuracy of the proposed algorithm. The results show that the approach proposed in this paper can meet the accuracy requirements of consumer products.

In recent years, there has been an increasing interest in hand movements in various application fields. However, the human hand is too dexterous and only has limited space. Developing a proper method to monitor and capture hand motion is meaningful. Conventionally, an optical measurement method is widely used to capture hand gestures. Nevertheless, this method is costly and has the problem of line-of-sight shielding. In this paper, a sensor fusion algorithm is proposed to calculate a more accurate result by calculating acceleration, magnetic field strength, and angular speed from the inertial measurement unit (IMU). The core concept of this algorithm is based on the idea of feedback control. To validate the performance, the active rotary platform is set up to compare the measured results to the references directly. Most of the error results are less than 3°, and the standard deviations are less than 1°. The measurement results ensure the feasibility of the inertial measurement method with the sensor fusion algorithm proposed in this paper.

This paper proposes a phase-derived velocity measurement (PDVM) method for high-speed targets based on wideband direct sampling linear frequency modulated radar. First, a high-speed target echo model considering intrapulse Doppler modulation is developed. Then, a PDVM model considering acceleration is established. The key to realizing PDVM is resolving phase ambiguity. Under low signal-to-noise ratio (SNR) conditions, a joint processing method combining acceleration information and multiframe data to solve phase ambiguity is proposed, which can significantly reduce the SNR requirement for PDVM. In this paper, the small-amplitude micromotion measurement capability of the proposed method is verified by simulation. Moreover, the measured data of a Ku-band ground-based radar are used to verify the applicability of the PDVM method under low SNR conditions and its feasibility to be applied to complex multi-scattering point targets. Both the simulation and experimental results show that the proposed method is suitable for high-speed targets with radial motion, including acceleration and jerk, and that the PDVM precision can reach the order of magnitude of centimeters per second or millimeters per second.

Purpose The purpose of this paper is to present the calibration of a laser welding model suitable for solving problems with input data that are either unknown or known only approximately. Design/methodology/approach The calibration starts from the measured temperature profile of the weld, and the aim is to get a similar profile by the solution of the model. The corresponding procedure is based on replacing the material characteristics that are known only approximately by polynomial or rational functions whose coefficients are determined using a suitable optimization process. The algorithm is supplemented with a simplified model of the keyhole shape. Findings The big advantage of the proposed approach is the velocity of solution of the problem and low consumption of the sources (hardware and software). In comparison with solving the full model of laser welding, the methodology provides results of a still acceptable accuracy by several orders faster. On the other hand, the results also depend on the strategy of selecting the points at which the temperature is verified and on “manual” setting of the deformation parameters. Research limitations/implications Application of the methodology is conditioned by several experiments with the used material (without experiment it is impossible to carry out the calibration and set the shape of the keyhole), while the full model allows it. On the other hand, the full model is not able to predict the errors in the case when some input data is unknown or known only approximately and the results have to be also confirmed experimentally. Practical implications The presented methodology may be used for determining unknown material characteristics and faster modelling of laser welding. Originality/value This paper proposes a novel methodology for evaluation of quality of laser welds in cases of unknown or partially unknown material parameters and substantial acceleration (by 2-3 orders) of the numerical solution of the model of laser welding.

Purpose The purpose of this paper is to improve the positional accuracy, smoothness on motion and productivity of industrial robot through the proposed optimal joint trajectory planning method. Also a new improved algorithm, i.e. non-dominated sorting genetic algorithm-II (NSGA-II) with achievement scalarizing function (ASF) has been proposed to obtain better optimal results compared to previously used optimization methods. Design/methodology/approach The end effector positional errors can be reduced by limiting the uncertainties of dynamic parameter variations like torque rate of joints. The jerk induced in robot joints due to acceleration variations are need to be minimized which otherwise induces vibrations in the manipulator that causes deviation in the encoders. But these lead to a vast increase in total travel time which affects the cost function of trajectory planning. Therefore, these three objectives need to be minimized individually so that an optimal trajectory path can be achieved with minimum positional error. Findings The simulation results have been obtained by running the proposed hybrid NSGA-II with ASF in MATLAB R2017a software. The optimal time intervals have been used to calculate jerk, acceleration and torque values for consecutive points on the trajectory path. From the simulation and experimental results, it can be concluded that the optimization technique could be used effectively for the trajectory planning of six-axis industrial manipulator in the joint space on the basis of minimum time-jerk-torque rate criteria. Originality/value In this paper, a new approach based on hybrid multi-objective optimization technique by combining NSGA-II with ASF has been applied to find the minimal time-jerk- torque rate joint trajectory of a six-axis industrial robot for obtaining higher positional accuracy. The results obtained from the execution of algorithm have been validated through experimentation using Kawasaki RS06L industrial robot for a particular defined path.

This paper focuses on the dynamic stability of spinning missiles equipped with two-loop autopilot considering the seeker disturbance rejection rate parasitical loop (DRRPL) effect induced by attitude disturbance of projectile. The representative mathematical model of spinning missiles in the non-spinning coordinate system is established, and the cross-coupling effect between the pitch and yaw induced by the rotation motion of missile body is analyzed and decoupled. The two-loop acceleration autopilot for each channel is designed with the conventional design method, and the relationship between the autopilot gains and the expected design indexes is deduced. A proportional navigation guidance (PNG) system model with consideration for the seeker DRRPL is further proposed in the form of complex summation. After strict mathematic deduction, the sufficient and necessary condition of the dynamic stability for spinning missiles is obtained. Numerical simulations and discussions under different cases are conducted to demonstrate the validity of stability condition. The results indicate that the stability of a spinning missile is closely related to the amplitude of the seeker DRR, the rolling rate, and the autopilot design indices. The stable region of the autopilot design frequency is obtained by solving the dynamic stability condition. To meet the requirement of stable controlling at a constant spinning rate, it was found to be effective to decrease the amplitude of the seeker DRR for spinning missiles, employ the lead angle decoupling approach to the commands for the servo system, and guarantee that the autopilot design frequency is lower than the critical value. The dynamic stability condition derived in this paper is useful for evaluating the stability of a spinning missile with consideration for the seeker DRRPL, and the conclusions obtained can provide guidance for the autopilot design of spinning missiles.

Vibration and acoustic noise in switched reluctance motor (SRM) drives have been investigated and addressed frequently. However, the focus of most the paper is on vibration of the stator frame due to radial electromagnetic forces acting on the stator teeth. In this paper, a comprehensive vibration analysis for a SRM assembly using finite element (FE) method is conducted, which considers the stator and rotor vibrations due to radial electromagnetic force as well as the effect of mechanical coupling on the vibration between the stator and rotor. First, an experimental modal test was performed to extract modal parameters and to observe the coupling effect. The parameters were then used to adjust and validate the FE model that was used to obtain transfer functions for vibration characterization. Using the frequency domain representation of the radial magnetic force vector and the calculated transfer functions, radial and tangential vibration components have been predicted.

Inerter, which is defined as a two-terminal mechanical element, has the characteristic that the force generated at its two terminals is proportional to the relative acceleration of the two ends. In this paper, a vibration isolator with lateral inerters is proposed and the effect of this geometrical nonlinear inerter on its dynamic performance is investigated. The force of the inerters in the moving direction of the mass and the acceleration term in the dynamic equation are nonlinear. The dynamic response is obtained using the averaging method and further checked by the numerical results, the stability analysis is also considered. The critical surface of the structural parameters which leads to no jump phenomenon and the jump frequencies when jump phenomenon occurs are determined by the Sylvester resultant method. The isolation performance of the lateral inerter-based vibration isolator is evaluated using four performance indexes: maximum dynamic displacement, maximum transmissibility, isolation frequency band and transmissibility in the higher isolation frequency band, and is compared with the parallel and series-connected inerter-based vibration isolators, as well as the linear vibration isolator. The results show that when the force amplitude is small, compared with the linear vibration isolator, the lateral inerter-based vibration isolator proposed in this paper can have a smaller maximum force transmissibility and larger isolation frequency band; the force transmissibility in the higher isolation frequency band is the same, which has the corresponding advantages of the parallel and series-connected inerter-based vibration isolators, respectively.

In classical gun and satellite launching systems, noise, flame, and hazardous gasses occur during the explosion of gunpowder, and it is possible to change the muzzle velocity of projectile only during the production phase. In addition, negative aspects of classical guns include the storage of munitions, their decay in time, high amount of their mass, and their high cost. In this paper, “A New Electromagnetic Coilgun” is designed to allow acceleration of a ferromagnetic projectile with the help of instantaneous alternate current applied on four sequential stator coils without using any mechanical boosters. programmable interface controllers microcontroller software and Delphi software were used to obtain the data from optic systems placed at the beginning of stator coils for gradual velocity measurement of the projectile, to process the same, and to perform triggering checks. Furthermore, such Delphi-based software allowed to improve the muzzle velocity by changing the triggering time for coils and, thus, to optimize the system. This paper is distinguished from other studies in the literature in terms of the software used and the design of accelerating coil. Data communication was ensured through the serial port of the PC during the launching process. The study examined the effects of variables such as the voltage applied on coils, number of turns of the coil, and the number of capacitors on the maximum muzzle velocity that may be obtained through the launcher and these were discussed in detail in the scope of the paper.

In navigation of autonomous underwater vehicles (AUVs), the estimation of position is an important issue, especially, when the sensors such as gyroscopes contain a lot of noise, and the velocity information of Doppler velocity log (DVL) is affected by the motion attitude of the vehicle. In this paper, based on an improved auto regressive (AR) model, a real-time filter is utilized for gyroscope signal de-noising. Meanwhile, according to the characteristics of the AUV, the influence of the vehicle attitude on the DVL velocity measurement error is analyzed and a motion attitude assist (MAA) method based on error model is introduced for enhancing DVL velocity accuracy. In this paper, using the proposed hybrid approach, an inertial navigation system (INS)/DVL integrated navigation system is designed. The proposed approach is evaluated by simulation and experimental test in different acceleration bound, and the existence of the DVL outage for an AUV. The results indicate that the precisions of the velocity and position are improved effectively, especially in complex motion attitude and long sailing conditions.

Position-estimation systems for indoor localization play an important role in everyday life. The global positioning system (GPS) is a popular positioning system, which is mainly efficient for outdoor environments. In indoor scenarios, GPS signal reception is weak. Therefore, achieving good position estimation accuracy is a challenge. To overcome this challenge, it is necessary to utilize other position-estimation systems for indoor localization. However, other existing indoor localization systems, especially based on inertial measurement unit (IMU) sensor data, still face challenges such as accumulated errors from sensors and external magnetic field effects. This paper proposes a position-estimation algorithm that uses the combined features of the accelerometer, magnetometer, and gyroscope data from an IMU sensor for position estimation. In this paper, we first estimate the pitch and roll values based on a fusion of accelerometer and gyroscope sensor values. The estimated pitch values are used for step detection. The step lengths are estimated by using the pitching amplitude. The heading of the pedestrian is estimated by the fusion of magnetometer and gyroscope sensor values. Finally, the position is estimated based on the step length and heading information. The proposed pitch-based step detection algorithm achieves 2.5% error as compared with acceleration-based step detection approaches. The heading estimation proposed in this paper achieves a mean heading error of 4.72° as compared with the azimuth- and magnetometer-based approaches. The experimental results show that the proposed position-estimation algorithm achieves a high position accuracy that significantly outperforms that of conventional estimation methods used for validation in this paper.

The driving conditions of vehicles, such as rapid acceleration, lasting downhill and so on, which demand for drive power, are rapidly increasing. For an electric vehicle driven by in-wheel motor (IWM), the IWM needs to provide greater power to maintain the normal operation of the vehicle. At present, the pursuit of high power density for IWM reduces the volume of motor under the same power. But the loss density is increased correspondingly, which will lead to overheating of IWM. In this paper, a 15-kW IWM drive system is taken as the research object. Based on the establishment of the temperature analysis model, instantaneous thermal characteristics of the IWM drive system are analyzed under the long climbing condition with low-speed and rapid acceleration driving cycles. The results show that the temperature of the stator winding and stator core is relatively high under the two driving cycles. The temperature of the stator winding is always in the highest level, and the maximum all appear on the end winding. The highest temperature of the end winding can reach 229.49 °C under the rapid acceleration driving cycles, which significantly exceeds the limitation for the insulation (155 °C) and will seriously affect the normal operation of the IWM and the vehicle. Therefore, in the follow-up design of cooling system, spray cooling with good local cooling effect can be adopted to focus on the cooling for the end winding. This paper can provide theory for the design of the feasibility thermal cooling solution.

This paper presents a novel method of estimating the altitude of pedestrians who are walking in the indoor environment of a multi-story building. We will show that to achieve pedestrian altitude estimation, a pedestrian only needs to wear a small MEMS-based integrated sensing device consisting of a micro-IMU (i.e., consists of a 3D accelerometer, a 3D gyroscope, and a 3D magnetometer) and a barometer, during indoor activities. High-precision estimates of the pedestrian's position in the vertical direction were obtained by utilizing the acceleration and angular rate data, as well as the height, deduced from barometer data. The inherent drifts of the IMU sensors, which lead to cumulative errors in altitude estimation, were sharply reduced using a complementary filter and an error compensation algorithm. The experimental results demonstrate that this method is effective in reducing estimation errors. When a person walks on stairs with the same step height, the error of the estimated height of each step is within 0.5 cm, and the cumulative height error is about 1.7% over a total height of 2.9 m. This integrated sensing device also exhibits good stability, i.e., three 20-min tests in a 12-h period showed that the cumulative error accounts for about 2% of the total height of 11.23 m. When the stairs have different heights, i.e., heights ranging from 12 to 28 cm, the estimated height error of each step is within 2 cm. With an ability to provide accurate and reliable vertical altitude estimates of pedestrians inside a multi-story building, the sensing device developed through this paper is suitable for use in 3D-space body tracking and pedestrian navigation applications.

This paper investigates the potential use of dielectric laser accelerators (DLAs) for nuclear security applications. For the first time, the LSP code is used to look at this application. LSP is a fast running, parallelized particle-in-cell code that includes space charge effects. The focus of this paper is to ascertain the order of magnitude, amount of charge, that can be driven through the accelerator. From these results, a recommendation on the potential of DLAs for nuclear security applications is given.

2-s2.0-85101300146 This paper presents forced vibration analysis of a simply supported beam made of carbon nanotube-reinforced composite material subjected to a harmonic point load at the midpoint of beam. The composite beam is made of a polymeric matrix and reinforced the single-walled carbon nano-tubes with their various distributions. In the beam kinematics, the first-order shear deformation beam theory was used. The governing equations of problem were derived by using the Lagrange procedure. In the solution of the problem, the Ritz method was used, and algebraic polynomials were employed with the trivial functions for the Ritz method. In the solution of the forced vibration problem, the Newmark average acceleration method was applied in the time history. In the numerical examples, the effects of carbon nanotube volume fraction, aspect ratio, and dynamic parameters on the forced vibration response of carbon nanotube-reinforced composite beams are investigated. In addition, some comparison studies were performed, with special results of published papers to validate the using formulations. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

The position of mechanical arm in people’s life is getting higher and higher. It replaces the function of human arm, moving and moving in space. Generally, the structure is composed of mechanical body, controller, servo mechanism, and sensor, and some specified actions are set to complete according to the actual production requirements. The manipulator has flexible operation, good stability, and high safety, so it is widely used in industrial automation production line. With the development of science and technology, many practical production requirements for the function of the manipulator are more and more refined, especially in the high-end research field. For example, medical devices, automobile manufacturing, deep-sea submarines, and space station maintenance put forward higher requirements for it. In terms of miniaturization and precision, it can meet the needs of scientific research and actual production. But these are inseparable from the motion control system technology. This paper mainly introduces the research of manipulator control system based on AI wearable acceleration sensor, aiming to provide some ideas and directions for the research of wearable manipulator. This paper presents the research method of manipulator control system based on AI wearable acceleration sensor, including the establishment of manipulator kinematics model, common filtering algorithm, and PI algorithm of speed control system. It is used for the research and experiment of manipulator control system based on AI wearable acceleration sensor. The experimental results show that the average matching rate of the manipulator control system based on AI wearable acceleration sensor is as high as 88.89%, and the stability of the feature descriptor is high.

Wearable Coaching System is a multi-sensor device for real-time training coaching. The system comprises of six modules which are shoulder, waist, a pair of wrist and a pair of ankle modules. It is compact, light, comfortable to wear and is suitable for any size of user. It system has five main embedded sensors: heart rate, three-axis acceleration, gyro, temperature and blood oxygen saturation (SpO2) sensor. It operates in streaming mode for real-time data processing using two telecommunication tools: ZigBee and Bluetooth and low energy interface for recording mode is using an internal flash memory. In this paper, a wearable coaching system is designed to help athlete or trainer to perform proper and efficient exercise suitable to one's body needs. It measures the parameter of the body, analyze and provide feedback in a form of an advice. In order to improve the system, arm gesture mode performed by the wrist modules of the system is applied. This mode is to enable user to manage their exercising level to a more appropriate pace, suitable with their individual body by reproducing the feedback. In a supervised coaching training, percentage of heart rate threshold target is increasing, hence, producing a greater performance of training. It is proven in this paper, that wearable coaching system performs an accurate measurement in enhancing sports and coaching training, adding value to novel lifestyle exercising and health monitoring.

In this paper, a novel method for accelerating eddy currents calculation on a cell model using the finite element method (FEM) is presented. Due to the tiny thickness of cell membrane, a full-mesh cell model requires a large number of mesh elements and hence intensive computation resources and long time. In this paper, an acceleration method is proposed to reduce the number of mesh elements and therefore reduce the computing time. It is based on the principle of replacing the thin cell membrane with an equivalent thicker structure. The method can reduce the number of mesh elements to 23% and the computational time to 17%, with an error of less than 1%. The method was verified using 2D and 3D finite element methods and can potentially be extended to other thin shell structures. The simulation results were validated by measurement and analytical results.

In this paper a three-axis capacitor accelerator has been designed, analyzed and optimized using micro-electromechanical systems technology. The accelerometers are generally divided into three categories of single axis, two axes, and three axes in terms of their ability to measure acceleration. In the suggested structure, acceleration measurements are carried out on all three axes simultaneously using a mass and spring system, which makes it possible to achieve a high sensitivity at a low occupancy level without losing other accelerator factors. By taking difference in this structure, it is shown that each axis acceleration has a very low impact on the measured acceleration of the other two axes. If any external factor changes the value of a single capacitor, the original output of the capacitor does not change for detecting acceleration. In other words, the acceleration of any of these three axes, due to its designing features, does not influence the other two axes and the system performance cannot be disrupted by external factors. The other important characteristics of the accelerometers are dynamic range, operating frequency and sensitivity. This study covers a dynamic range up to 1000g and an operating frequency up to 20 kHz. The accelerometer sensitivity is 4fF/g in the z axis direction while it is 9fF/g in the x and y axes directions. In this paper, the simulation of the structure is performed using Intellisuite software. Moreover, a multi-objective genetic optimization algorithm has been used to determine the dimensions of the constituents of the spring and the weight.

The output torque is an important performance indicator of a motor. Due to the special structure of a permanent magnet spherical motor (PMSM), it is difficult to measure its torque. This paper proposes a novel method to measure the output torque of the PMSM. The proposed method uses the microelectromechanical system (MEMS) gyroscope to measure the rotor motion acceleration, which is then used to calculate the output torque based on the rotor dynamics equation. In this paper, we firstly simulate and analyze the output torque of the PMSM. Secondly, we design a torque-measuring device to measure the output torque. Thirdly, we compare and discuss the experimental and simulation results. The comparison results show that the proposed method is feasible.

Radio frequency (RF) power in the ion cyclotron range of frequencies (ICRF) is one of the primary auxiliary heating techniques for Experimental Advanced Superconducting Tokamak (EAST). In this paper, we will present an overview of the main experimental results from recent campaign on EAST. 1) A dedicated experiment for more than 10MW operations has been carried out on EAST. The major aspects linked to the use of the EAST auxiliary heating systems: ICRF,LHCD and NBI are presented with emphasis on ICRF and LH. The challenges for ICRF coupling on EAST will be described at the low densities typically used for long pulse operation with lithium wall conditioning. 2)This paper also summarizes effects of ICRF power on LH coupling and modification of heat loads on EAST. 3) Co-current rotation driven by ICRF are observed in both L-mode and H-mode discharges. Co-current rotation can be generated by ICRF heating in LHCD plasma. Different rotation behavior observed in LHCD discharges. ICRF can also induce counter-current rotation in LHCD L-mode discharges. 4) A high-frequency magnetic probes (HFBs) system has been developed and successfully applied to detect ion cyclotron emission (ICE) in D-NBI injection experiments in the 2018 experimental campaign of EAST. ICE driven by fast D-NBI ions and fusion born ions are observed on EAST.5) In Hydrogen minority in Deuterium plasma, the interaction of fast wave and fast D-NBI ions is detected on EAST. Acceleration of fast D ions is confirmed by increased neutron yield.

Вступ. Обчислювальні алгоритми безплатформних інерційних навігаційних систем (БІНС) можна розділити на навігаційні алгоритми, які перетворюють вихідні сигнали акселерометрів у шукані координати місця розташування об'єкта та алгоритми орієнтації, які перетворюють вихідні сигнали гіроскопів у кути орієнтації рухомого об'єкта [1]. При цьому для вирішення навігаційної задачі необхідно двічі інтегрувати прискорення, а для вирішення завдання орієнтації – інтегрувати диференціальні кінематичні рівняння орієнтації, що зв'язують виміряну кутову швидкість об'єкту з параметрами орієнтації. У роботі йде мова про автономні методи позиціонування на основі інформації про кутову швидкість руху об'єкта без використання інформації про лінійне прискорення, тому далі розглядаються обчислювальні алгоритми орієнтації, що складають найважливішу частину БИНС – безплатформову інерціальну систему орієнтації (БІСО). У статті розглядаються похибки алгоритмів, побудованих на використанні кватерніонних рівнянь орієнтації, при чому у якості основної характеристики точності алгоритмів БІСО прийнято дрейфи цих похибок. Основна частина. Дослідження алгоритмів проводиться шляхом моделювання роботи бортового обчислювача відповідно до розглянутих алгоритмів. Кінцевим результатом комп'ютерного моделювання є встановлення залежності дрейфів похибок чисельного інтегрування рівняння орієнтації від кроку опитування датчиків при різних значеннях частоти і амплітуди кутових коливань основи. Розглянуто чотири однокрокових алгоритми - реверсивний, на основі модифікованого методу Ейлера, побудований методом Пікара двома послідовними наближеннями і авторський на основі комбінування формул перших двох алгоритмів. Досліджено залежності дрейфів похибок від різниці фаз між коливаннями об'єкта навколо двох його ортогональних осей. Показано, що найбільші за величиною дрейфи в усіх випадках спостерігаються при конічному русі об'єкта. Проведено модельні дослідження залежностей амплітудних дрейфів від кроків опитування і частоти коливань у безрозмірній формі. Показано суттєве збільшення точності у нового алгоритму порівняно з усіма іншими розглянутими. Висновки. Точність за дрейфами похибок запропонованого алгоритму в 2600 разів перевищує аналогічну точність використовуваного реверсивного алгоритму. Незначною видозміною формули однокрокового алгоритму вдалося підвищити точність на кілька порядків, практично не змінюючи обсяг обчислень. Отримані результати дозволяють розширити область використання алгоритмів БІСО і прогнозувати їх точність при різних рухах основи. Introduction. Calculative algorithms of Strapdown inertial navigation systems (SINS) can be divided on navigation algorithms, which transform accelerometers output signals into local coordinates and attitude algorithms, which transform gyroscopes output signals into vehicle angular attitude [1]. Wherein, navigation task solution requires double integration of acceleration and attitude task – integration of kinematic attitude equation, related measured object angular velocity with attitude parameters. Paper considered of autonomous position determination methods based on vehicle angular velocity information without acceleration measurement. Thus, attitude algorithms are considered only. Paper researched the errors of algorithm based on quaternion attitude equation, moreover algorithm error drifts were accepted as a main accuracy characteristic The main part. Algorithm researched by imitation modeling of vehicle’s computer with SINS attitude algorithm. The main task of modeling is defining depends between algorithm drift and sensor’s call step in cases of different frequencies and amplitudes of base angular oscillations. It was researched four one-step algorithms: reverse, based on modified Euler method; Picard method with two successive approximations and the new author’s algorithm which combines formulas of first two algorithms. It was studied depends of algorithm drift and faze shift between two orthogonal axes oscillations. It was shown, the biggest drift values are obtained in case of base conning movement. It was made the modeling researches of algorithm drift amplitudes relatively to sensor sample steps and oscillation frequencies in dimensionless form. It was shown, substantial increase new algorithm accuracy compared to other researched. Conclusions. The algorithm drift accuracy of new algorithm in 2600 times exceeds the revers algorithm. Small modification of one-step algorithm allowed increase accuracy in few orders, almost without computing increase. Received results allows to expend attitude algorithms application area and prognose their accuracy with different base movement. Введение. Вычислительные алгоритмы бесплатформенных инерциальных навигационных систем (БИНС) можно разделить на навигационные алгоритмы, которые преобразуют выходные сигналы акселерометров в искомые координаты местоположения объекта, и алгоритмы ориентации, которые преобразуют выходные сигналы гироскопов в углы ориентации подвижного объекта [1]. При этом для решения навигационной задачи необходимо дважды интегрировать ускорение, а для решения задач ориентации – интегрировать дифференциальные кинематические уравнения ориентации, связывающие измеренную угловую скорость объекта с параметрами ориентации. В работе речь идёт об автономных методах определения углового положения объекта на основе информации об угловой скорости его движения, поэтому далее рассматриваются вычислительные алгоритмы ориентации, составляющие важнейшую часть БИНС – бесплатформенную инерциальную систему ориентации (БИСО). В статье рассматриваются погрешности алгоритмов, построенных на использовании кватернионных уравнений ориентации, причём в качестве основной характеристики точности алгоритмов БИСО приняты дрейфы этих погрешностей. Основная часть. Исследование алгоритмов проводится путём моделирования работы бортового вычислителя в соответствии с рассматриваемыми алгоритмами. Конечным результатом компьютерного моделирования является установление зависимости дрейфов погрешностей численного интегрирования уравнения ориентации от шага опроса измерителей при различных значениях частоты и амплитуды угловых колебаний основания. Рассмотрены четыре одношаговых алгоритма – реверсивный, на основе модифицированного метода Эйлера, построенный методом Пикара двумя последовательными приближениями и авторский на основе комбинирования формул первых двух алгоритмов. Изучены зависимости дрейфов погрешностей от сдвигов фаз между колебаниями объекта вокруг двух его ортогональных осей. Показано, что наибольшие по величине дрейфы во всех случаях наблюдаются при коническом движении объекта. Проведены модельные исследования зависимостей амплитудных дрейфов от шагов опроса и частоты колебаний в безразмерной форме. Показано существенное увеличение точности у нового алгоритма по сравнению со всеми другими рассмотренными. Выводы. Точность по дрейфам предложенного алгоритма в 2600 раз превышает аналогичную точность используемого реверсивного алгоритма. Незначительным видоизменением формулы одношагового алгоритма удалось повысить точность на несколько порядков, практически не изменяя объем вычислений. Полученные результаты позволяют расширить область использования алгоритмов БИСО и прогнозировать их точность при различных движениях основания.

Even for modern robot attached gripping solutions, surface-sensitive object handling remains a challenge. A minimal gripping force is required to grip and handle a surface-sensitive object safely. At the same time, this gripping force should not exceed a certain level to avoid damaging the sensitive surface of the object. Because of this, it is necessary to determine the mostly small range of optimal gripping forces to ensure a safe handling. Therefore, this paper describes an approach to evaluate this range of gripping forces for surface-sensitive objects using by means of chocolate covered marshmallows. For this purpose, a test bench with the same characteristics as a planned gripper is developed. Throughout the project, this planned gripper will be controlled with the help of the detected range of gripping forces. In addition to these static measurements, it is planned, that the gripper will calculate the handling speeds, accomplished by a six-axis industrial robot, with its acceleration forces. The achieved results of this paper will be the starting point for the upcoming measurements with the robot. Furthermore, the influence of the temperature on the range of gripping forces was evaluated, to show the relevance of consistent environmental conditions for the handling of surface-sensitive objects.

For the single-rod double-cylinder and double-coil magnetorheological (MR) damper studied in this paper, the damping force model of the damper is established by adopting multidisciplinary domain modeling method bond graph theory. Firstly, combined with the structure of the MR damper, the bond graph model of the MR damper was established, the damping force model of the damper was derived through the bond graph theory, and the influence factors, such as the displacement, velocity, and acceleration of the damper were considered in the model. Based on the simulation of force-displacement and force-velocity characteristics of the damping force carried out by the damper theoretical model under different currents and velocities as well as the comparison with the damper bench test results, it was found that the force-displacement and force-velocity characteristic experiment curves of the damper agreed well with the simulation results. Under different working conditions, the maximum error of damping force of the MR damper was 7.2%. The damping force model of the MR damper studied in this paper was compared with that of the damper without considering the inertia force of MR fluid, and the influence of the inertia force of MR fluid on the damping force of the MR damper was analyzed. The results show that when the frequency of the damper is large, the inertial force of MR fluid has an important influence on the damping force; therefore, considering the inertial force of MR fluid in the model can greatly improve the accuracy of the model. The influence degree of key parameters on the damping force of the MR damper was studied through the theoretical model; such key parameters ranging from large to small were the channel clearance, energizing current, piston diameter, motion velocity, channel length, zero-field viscosity of MR fluid, and nitrogen pressure. This provides a basis for the adjustment of the damping force of the MR damper.

Bearings are an important part of mechanical equipment and it will cause a series of mechanical failures once the malfunction of bearing occurs. Rotor unbalance is the most common type of bearing failure; thus the assessment of bearing rotor unbalance is essential to maintain the normal operation of mechanical. In this paper, a method based on Welch power spectral density estimate (Welch-PSD) and stacked automatic encoder (SAE) is proposed to achieve state assessment of bearing rotor static unbalance by processing the two-way vibration signals collected by the acceleration sensor installed in the vertical and horizontal directions of the bearing. Firstly, the Welch-PSD method is used to decompose the vibration signal to obtain the power spectral density, and the vibration power of the working frequency is taken as the feature. Then, the Stacked Auto-Encoder method is introduced to assessment the bearing rotor unbalance state. This paper designs an experiment of rotor unbalance fault in different degree to verify the accuracy of the designed method. The experimental results show that the Welch-PSD method can accurately extract the rotor unbalance fault feature. In addition, the SAE neural network can apply the fault feature to accurately assessment the bearing rotor unbalance degree.

In this paper, a new optimal guidance law with terminal constraints on miss distance and intercept angle is proposed for a missile with time-varying velocity against a maneuvering target. The proposed optimal guidance law is obtained by solving a linear quadratic optimal control problem. Miss distance and intercept angle costs are weighted by variants of hyperbolic tangent function and energy cost is weighted by a power of time-to-go. The rule for determining a key parameter in the variant of hyperbolic tangent function is studied using the theory of second order differentiation, and its validity is verified by numerical simulation. In the purpose of easy implementation, an analytical solution of the proposed optimal guidance law is derived using assumption of constant velocity when calculating integral of missile's velocity from current time to final time. The significant contribution of this paper lies in that it is the first time a variant of hyperbolic tangent function is developed and employed as weighting coefficients of constraints on miss distance and intercept angle. Therefore, the proposed optimal guidance law can reduce acceleration command at the initial phase and increase missile's terminal velocity. Nonlinear numerical simulations clearly demonstrate effectiveness of the proposed optimal guidance law.

Health monitoring by conventional sensors like accelerometers or strain gauges becomes challenging for large rotating structures due to the issues with feasibility, sensing and data transmission. In addition, acceleration measurements have low capability of presenting very small frequencies, which happen very often for large structures (for instance, frequencies between 0.2 and 0.5 Hz in horizontal-axis wind turbines). By contrast, displacement measurement using stereo vision is rapid, non-contacting and distributed over the structure. The sensors are cheaper and more easily applied to many places on the object to be measured. Horizontal-axis wind turbines are one of the most important large rotating structures and need to be measured and monitored in time to prevent damage and failure, and the blade tip position is one of the key parameters to measure in order to prevent the blade hitting the turbine tower. This paper presents a clearly described and easily applicable procedure for measuring the displacement on the components of a rotating horizontal-axis wind turbine with stereophotogrammetry. Paper markers have been applied on the rotor and tower of a scaled-down horizontal-axis wind turbine model in the workshop and the displacement measurement method has been demonstrated by measuring displacement during operation. The method is mainly developed in two parts: (1) camera calibration and (2) tracking algorithm. We introduce an efficient camera calibration method for measurement in large fields of view, which has always been a challenge. This method is easy and practical and offers better accuracy compared with 2-D traditional camera calibration. The tracking algorithm also works successfully and is able to track the points during rotation within the measurement time. Finally, the accuracy analysis has been conducted and has shown better accuracy of the new calibration method compared with 2-D traditional camera calibration.

Purpose The purpose of this paper is to propose a control algorithm to improve the backdrivability performance of minimally invasive surgical robotic arms, so that precise manual manipulations of robotic arms can be performed in the preoperative operation. Design/methodology/approach First, the flexible-joint dynamic model of the 3-degree of freedom remote center motion (RCM) mechanisms of minimally invasive surgery (MIS) robot is derived and its dynamic parameters and friction parameters are identified. Next, the angular velocities and angular accelerations of joints are estimated in real time by the designed Kalman filter. Finally, a control algorithm based on Kalman filter is proposed to enhance the backdrivability of RCM mechanisms by compensating for the internally generated gravitational, frictional and inertial resistances experienced during the positioning and orientating. Findings The parameter identification for RCM mechanisms can be experimentally evaluated from comparison between the measured torques and the reconstructed torques. The accuracy and convergence of the real-time estimation of angular velocity and acceleration of the joint by the designed Kalman filter can be verified from corresponding simulation experiments. Manual adjustment experiments and animal experiments validate the effectiveness of the proposed backdrivability control algorithm. Research limitations/implications The backdrivability control algorithm presented in this paper is a universal method to enhance the manual operation performance of robots, which can be used not only in the medical robot preoperative manual manipulation but also in robot haptic interaction, industrial robot direct teaching and active rehabilitation training of rehabilitation robot and so on. Originality/value Compared with other backdrivability design methods, the proposed algorithm achieves good backdrivability for RCM mechanisms without using force sensors and accelerometers. In addition, this paper presents a new static friction compensation approach for a joint moving with very low velocity.

Faster trajectory correction and control mechanisms are required to correct the radar handing-over error coupled with homing guidance demands for Missile Interceptors. Solid Divert and Attitude Control System (SDACS), which typically have a very low time constant, is one of the most efficient and accurate way to meet these demands. The SDACS has challenges both with respect to the Hot Gas Valve (HGV) technology as well as actuator requirements. The paper proposes a novel method to simplify the controller design and reduce actuator needs for the rotary hot gas valves based SDACS. The proposed method formalizes a linear Pseudo-control to track the lateral acceleration and attitude correction commands. The pseudo-control requirements are tracked through the HGV rotations. The paper further proposes the normalization of the pseudo-control to make the controller generic making it invariant of the valve size and relative dimensions of the HGV’s static & moving part. The paper also proposes a technique to reduce the number of actuators required for the full SDACS system by use of these near affine pseudo-controls.

This paper presents a release method for micro-objects. To improve position accuracy after release, we propose 3D high-speed end-effector motions. The classical release task focuses on the detachment of a micro-object from an end-effector. The technique utilizes merely the vibration of the end-effector regardless of the pattern of movement. To release different sizes of micro- objects and place them precisely at the desired locations in both air and liquid media, in this paper, we propose high-speed motions by analyzing the adhesion force and movement of micro-objects after separation. To generate high end-effector acceleration, many researchers have applied simple vibration by using an additional actuator. However, in our research, 3D high-speed motion with apt amplitude is accomplished by using only a compact parallel mechanism. To verify the advantages of the proposed motion, we compare five motions, 1D motions (in X-, Y-, and Z-directions) and circular motions (clockwise and counterclockwise directions), by changing the frequency and amplitude of the end-effector. Experiments are conducted with different sizes of microbeads and NIH3T3 cells. From these experiments, we conclude that a counterclockwise circular motion can release the objects precisely in air, while 1D motion in the Y direction and two circular motions can detach the objects at the desired positions after release in a liquid environment.

This paper presents the possibility of suppressing the train-induced vibration on bridges using a linear passive vibration suppression device incorporating inerter. The inerter is a two-terminal mechanical element with the property that the applied force is proportional to the relative acceleration across its terminals. The inerter has been applied to various engineering structures where performance benefits have been identified. However, currently these studies are either limited to simple network configurations with moderate performance improvement, or resulted in complicated configurations with a large number of elements which are impractical for real-life applications. In addition, the potential of using inerter-based absorbers for suppressing the train-induced bridge vibrations has not been taken into consideration. In this paper, a simplified bridge model equipped with a vibration suppression device subjected to series of moving forces is presented. The structure-immittance approach, which can cover all networks with pre-determined numbers of each element type, is adopted for the identification of the optimal absorber configurations. Numerical studies for two bridges, the THSR and the Kum-gang, under three types of railway excitations, the French T.G.V., the German I.C.E. and the Japanese S.K.S. are conducted. It is demonstrated that the overall performance of the bridge can be improved by using the proposed inerter-based configuration. It is also checked that the absorber stroke is much smaller than the inner space of bridge box girder, indicating the practical installation of the absorber. Furthermore, the robustness of the proposed absorber is verified by sensitivity analysis subjected to the change of bridge parameters and the device component values.