Search

In the framework of the ALOHA (Astronomical Light Optical Hybrid Analysis) project, dedicated to high resolution imaging in the L-band using optical fibre and nonlinear optics, we have implemented a servo controlled hectometric outdoor fibre link between two telescopes and the recombination beam facility of the CHARA telescope array. A two-stage servo system using optical fibre modulator, fibre delay line, and a metrology laser at 1064 nm allows to stabilise the optical path difference within 3 nm RMS over a 3000 s record. Using an internal source at 810 nm, the signal-to-noise ratio of the fringe modulation peak is enhanced by a factor better than two when the servo control is switched on. This study can be also considered as a seminal work towards very long base fibre linked telescope arrays and allows to scale the perturbative environment of an outdoor fibre link. [ABSTRACT FROM AUTHOR]

When the wafer dicing saw processes hard and brittle materials, the wear rate of the grinding wheel blade accelerates. To detect blade wear in time, a grinding wheel blade wear detection method based on a fiber optic sensor was proposed. This paper studied the principle of grinding wheel blade wear detection method, detection device, hardware system composition, and detection signal triggering process. To improve the accuracy of blade wear detection, the proportional–integral–derivative + feedforward + notch filter control algorithm was used to improve the dynamic and static response characteristics of the servo control system. This study aimed to analyze the influencing factors of the detection accuracy and efficiency of blade wear by the changing optical fiber power response mode, brightness setpoint, and signal capture detection speed. According to the experimental results, fine mode, 50% brightness setpoint, and signal capture detection speed of 0.4 mm/s were selected as the optimal parameters for blade wear detection. The performance verification experiment of the blade wear detection method was carried out under the optimized parameters. Results revealed that the maximum measurement error of the blade wear detection method was 3.8 μm. Because the measurement error could meet the industrial requirement that the measurement error of grinding wheel blade wear detection of wafer dicing saw was less than 5 μm, this method was feasible. [ABSTRACT FROM AUTHOR]

Precision spraying technologies have been widely applied in modern agriculture, such as profiling, targeting, and variable spraying. But there are still great challenges, in terms of uneven distribution of canopy sap, low sap utilization, high dosage of sap, and serious environmental pollution. Especially, the uneven spraying volume can be found in the cross-sectional shape of the tree canopy caused by the dynamic changes in the spacing between the nozzle and the canopy. It is a high demand for a high effective space area in the spraying volume of liquid. In this study, a novel canopy wrap-around profiling-to-target spraying was proposed to draw on the manual spraying actions, particularly with the nozzle completing dynamic surround profiling of each fruit tree during the advance of the sprayer and targeting the inside of the canopy for spraying. A spraying machine of wind-fed fruit trees consisted of five subsystems: the power platform, profiling-to-target mechanism, wind-fed spraying system, navigation control system, and canopy detection system. There were also environment perception, automatic navigation, and profiling-to-targeting functions. A symmetrical mechanism was also designed with cross-arranged, two-degree-of-freedom, and radial profiling, according to the nozzle motion requirements. The forward motion of the sprayer was combined with the position and attitude adjustment of the nozzle in plane space. Besides, the kinematic model of the nozzles was established to accurately control the lateral and rotational movement position and speed using the two-loop PID controllers. Then, the semicircular and polygon trajectory profiling control of the nozzle was achieved to match the motion speed of the sprayer. At the same time, the nozzle was rotated dynamically to keep the spray aligned with the center of the canopy, in order to reduce the drift of the liquid in the air. After that, trunk identification and localization were proposed using DBSCAN density clustering and 3-point trunk shape fitting, where the planar LIDAR scanned the horizontal plane of trunk height in real time during the operation of the sprayer. The 2-D LiDAR was employed and mounted horizontally on the front of the applicator to scan and identify the tree trunk in advance. The localization of the nearest trunk to the sprayer was sent to the control system in real time, in order to enable the trunk position tracking for the wrap-around profiling control. The results showed that the positioning errors of the longitudinal and lateral trunks were 9.44 and 1.74 cm, respectively. The total control system of the applicator was equipped with an STM32 processor using the FreeRTOS real-time operating system. The dynamic servo profiling control of the nozzle was realized using LiDAR trunk position information via the multi-task distribution and efficient processing of real-time trunk position information sensing, dynamic nozzle profiling trajectory control, data communication, and operation interaction. Finally, the quantitative indexes were taken as the droplet deposition, droplet density, droplet coverage, and median diameter of droplet volume. 10 test points were also arranged in the different areas of the canopy. Furthermore, the six sets of comparison tests were carried out between the wrap-around profiling and fixed-spacing spraying mode. It was found that the average droplet density of the wrap-around spraying mode was 72.2 droplets/cm², the average deposition volume was 1.99 μL/cm², and the droplet coverage rate was 47.5%. More importantly, the droplet deposition and density increased by 36.3%, and 58.3 %, respectively, compared with the fixed-spacing spraying mode. Therefore, a higher liquid utilization rate was achieved during this time. The coefficient of variation of droplet deposition was 27.7% for the wrap-around application, which was 60% lower than that in the fixed-spacing spraying mode. There was a significant improvement in the canopy application uniformity. In summary, the wrap-around profiling spraying mode can be expected to effectively improve the utilization rate and uniformity of precision spraying. [ABSTRACT FROM AUTHOR]

Dual three-phase permanent magnet synchronous motor has been widely used for its reliable performance, high control precision, small output torque ripple and other advantages. In view of the control requirements of high reliability, high precision and small volume of servo motor in aerospace field, this study proposes a servo control algorithm and a specific implementation scheme of dual three-phase permanent magnet synchronous motor based on monolithic FPGA. Based on the hardware platform of Xilinx Kintex7 series XC7 K325 TFFG900 FPGA chip, the vector control algorithm of dual three-phase three-ring permanent magnet synchronous motor based on double DQ coordinate transformation is realized by Verilog hardware description language. In the verification of the experimental platform, the core control indicators of the current loop bandwidth of 600 Hz and the servo position loop bandwidth of 12 Hz have been achieved. [ABSTRACT FROM AUTHOR]

Severe uneven wire tension occurs during super-high-thickness (more than 1000 mm) cutting in high-speed wire electrical discharge machining, resulting in different discharge regularities between electrodes when the wire electrode is in the positive and negative traveling directions. Regarding the specific performance, a certain proportion of no-load pulses will appear between electrodes when the wire electrode is in the positive traveling direction, resulting in the feeding of the machine tool; when the wire electrode is in a negative traveling direction after feeding, a large number of short-circuit pulses will be formed, which seriously affect the continuous and stable feeding and the cutting speed. According to these different regularities, this work proposes the use of different reference objects as the basis of servo feeding in the positive and negative traveling directions. A pulse probability detection servo control method based on the discharge peak current is designed, and different control objects for the positive and negative traveling direction are used as the target probabilities of the proportional integral derivative algorithm. The results of experiments demonstrate that the proposed servo control method can significantly improve the cutting stability and cutting speed for super-high-thickness cutting. When cutting a workpiece with a thickness of 1000 mm, the surface machined by the average voltage detection-based servo method with the fixed threshold and the conventional pulse probability-based servo control method was found to exhibit obvious streaks, and the cutting speed was respectively 53.75 mm2/min and 63.6 mm2/min. Finally, the surface machined by the proposed servo control method was even, and the cutting speed was 77.78 mm2/min, thereby exhibiting an improvement of 44.71% as compared to that of the average voltage detection method with a fixed threshold, and the surface evenness was greatly improved. Thus, the proposed servo control method for super-high- thickness cutting was found to achieve a faster cutting speed and higher surface quality. [ABSTRACT FROM AUTHOR]

This article presents a high performance and low-cost design methodology for the servo control of magnetic drive-trains (MDTs) operating in direct drive mode. For the first time, this article considers using sensitivity peaks to analyze the robustness and stability of MDT control systems. Initially, through analysis of a dynamic model, the key spring characteristic parameters with respect to operating points, are developed. It is also shown that a wider dynamic performance envelope can be achieved by linearizing the MDT model at around 60 $\%$ –80 $\%$ of the maximum coupling torque, as opposed to traditional linearization under zero torque conditions. Subsequently, this article exploits the spring characteristics for a design methodology based on the $\text{H}_\infty$ mixed sensitivity approach to determine suitable control parameters. Following this, the maximum exogenous load-torque disturbance and speed reference that will not induce pole-slipping can be determined. Finally, preferential position reference profiles and optimal gains for position controllers are given to prevent demand-induced speed oscillations. The proposed methodologies are validated through simulation and experimental studies. [ABSTRACT FROM AUTHOR]

The increasing adoption of exotic and hard to cut materials in high-end applications makes electric discharge machining (EDM) process more relevant than ever. In particular, wire EDM variant (WEDM) deserves attention due to its ability to cut the workpiece's surroundings without completely evaporating the unused portion of the rare and expensive exotic materials. However, WEDM is a stochastic process that still lacks complete mathematical models and is driven by a myriad of parameters that will make its control a complex task. In WEDM, whenever the wire is fed too fast, the process will be interrupted not only by short circuits, but the wire electrode is most likely to break, jeopardising process efficiency in many ways. Currently, most of the literature has focused efficiency efforts in proposing a trade-off among parameters without a complete correlation with servo and control strategies. Therefore, this review aims to find and analyse the state-of-the-art approaches for controlling the Wire EDM process. A systematic literature review is conducted to identify and provide an adequate understanding of the best control strategies, fundamental parameters, and role. With no previous studies found, the present review focuses exclusively on servo control. First, it provides a comprehensive literature framework covering four decades, to next glimpse future developments of WEDM control strategies. Potential adoption of the findings can result in a deeper understanding of control variables and a broader and more efficient concept for WEDM servo feed control. • Wire EDM lacks complete mathematical models. • Fuzzy control strategy can deliver adaptive control solution for ill-defined processes. • Integrate vibration within control strategies is a crucial factor to advance in WEDM efficiency. • Current strategies are not suitable for different types of pulse generators. [ABSTRACT FROM AUTHOR]

This paper compares three different position controllers of electrical drives equipped by binomial n th order filters, which are offering filtering properties important in a quantization noise attenuation. To demonstrate their impact, a non-filtered P-PI control is considered, as a reference. The comparative framework includes a filtered P-PI control, a filtered linear pole assignment PD controllers with a disturbance observer (DO) based integral action and its constrained modification. In terms of a total variation, depending on noise and process properties, all filtered controllers are capable to bring down the undue controller activity at the plant input from 10 to more than 100 times. Furthermore, thanks to the applied disturbance observer, the constrained control derived for a double integrator is shown to fully exploit the closed loop capabilities without any trajectory generation, taking into account the control constraints. Thus, the simplified controller design may focus on other important aspects. [ABSTRACT FROM AUTHOR]

To achieve a high performance synchronized motion trajectory tracking of the hydraulic press slider-leveling electrohydraulic control system, an adaptive robust cross-coupling control strategy that incorporates the cross-coupling approach into adaptive robust control (ARC) architecture has been proposed. The primary objective of this study was describe that the nonlinear ARC controller together with a cross-coupling control (CCC) controller was integrated to solve the slider-leveling synchronization control system using four axes. A discontinuous projection-based ARC controller was constructed. A robust control method with dynamic compensation type fast adaptation was introduced to attenuate the effects of parameter estimation errors, unmodeled dynamics and disturbances, and improved the transient tracking performance of the system. The stability of the controller was proven by Lyapunov theory and the trajectory tracking error asymptotically convergences to zero. The simulation of a desired reference trajectory was included. The max tracking error of the proposed ARC controller of single axis was kept within—0.06 mm. The trajectory tracking error asymptotically converges to zero, which guaranteed the system would possess good transient behavior and confirmed the stability performance of the control system. The four axes synchronous errors of reference trajectory with cross-coupling controller indicated the maximum synchronization error of the proposed ARC + CCC controller between axis was within ±0.1 mm. The ARC together with a CCC controller for four hydraulic cylinders used parameter adaptation to obtain estimates of model parameters for reducing the extent of parametric uncertainties, and used a robust control law to attenuate the effects of parameter estimation errors, unmodeled dynamics, and disturbances. This study result shows that the proposed cross-coupling synchronization control scheme, together with the ARC law, provides excellent synchronization motion performance in a control system with four axes. [ABSTRACT FROM AUTHOR]

In this paper, we explore the design and evaluation method of the three-degrees-of-freedom double objective-lenses microsuspension actuators to guide the steps of design, evaluation, measurement and verification of the actuator. Further, we apply a dynamic model of the actuator in time domain and a simplified servo control mathematical model based on the second Lagrange equation. Given that the traditional microsuspension actuator design method is always ambiguous, we propose an design and evaluation method to guide the design process when there are multiple complex parameters. According to the design and evaluation method, the prototype is designed and accomplished, the dynamic characteristics of the prototype are measured, and the control simulation is carried out to verify the double objective-lenses microsuspension actuators could be controlled to compensates micro servo error of optical storage system timely and quickly. Results demonstrate that the design and evaluation method can effectively guide the design process of the microsuspension actuator. Also, the control system based on a lag-lead controller verifies the servo performance of double objective-lenses microsuspension actuator. [Display omitted] • A design and evaluation method of double objective-lenses microsuspension actuators. • A four-degrees-of-freedom dynamic model. • A simplified servo control mathematical model. • Physical prototype experiment and control system simulation. [ABSTRACT FROM AUTHOR]

• We integrate rotation axis calibration and servo control to register point clouds. • We propose the circle of deviation constraint for robust feature matching/rejection. • Alternating optimization divides, linearlizes and accelerates the objective function. • The proposed method outperformed other BA or ICP-based registration methods. A fast and accurate algorithm is presented to register scans from an RGB-D camera, which rotates and scans the entire scene in an automated fashion on a pan-tilt platform. The proposed algorithm, Axis Bound Registration , exploits the movement of the camera that is bound by the two rotation axes of pan-tilt servos, so as to realize fast and accurate registration of acquired point clouds. The rotation parameters, including the rotation axes, pan-tilt transformations and the servo control mechanism, are calibrated beforehand. Subsequently, fast global registration can be performed during online operation with transformation matrices formed by the calibrated rotation axes and angles. In local registration, features are extracted and matched between two scenes. For robust registration, false-positive correspondences are rejected based on the distances of pre-oriented keypoint pairs, namely the circle of deviation constraint. Then, a more accurate registration can be achieved by minimizing the residual distances between correspondence pairs, while estimated transformations are bound to the rotation axes. Results of comparative experiments validate that the proposed method outperforms state-of-the-art algorithms of various approaches based on camera calibration, global registration, and simultaneous-localization-and-mapping in terms of root-mean-square error and computation time. [ABSTRACT FROM AUTHOR]

An infrared image-based feedback control system for intelligent fire monitor was proposed in this paper, whose aims are to realize automatic aiming of the fire site and continuous fire tracking in the process of fire extinguishing through adjusting of the yaw angle of the fire monitor. Firstly, infrared camera was used to capture images of the fire site, and under high temperatures, the fire would be easily observed. An improved adaptive image threshold segmentation scheme was developed for image background segmentation and fire acquisition. The fire region in the captured image was considered as region of interest (ROI) and the geometric center of which was calculated. Due to the special advantageous structural design of the proposed system, the geometric center of ROI representing the actual fire was considered as the direction which the fire monitor should aim at. Furthermore, a fuzzy control scheme simulating the operating mode of firefighters was proposed, and the ROI center position deviation and deviation rate were considered as inputs of the control system. Experimental results show that, after the fire was detected by the system, the fire monitor could be yawed to the direction of the fire within 2000 ms, and the deviation of image position is less than 1.6 pixels. Similarly, the proposed system could be well adapted to the changing position of the fire caused by combustion. And after no more than image iteration of three frames, the controller realizes aiming of the fire by the fire monitor, and the final deviation is less than 0.1 pixels. In general, the proposed infrared image feedback control system for fire horizontal position aiming of intelligent fire monitor has great potential for intelligent fire extinguishing by fire-fighting robots. [ABSTRACT FROM AUTHOR]

This paper proposes a proportional–integral-differential (PID) filter-shaped optimal PI tracker for on-line robust optimal tracking control of a system with unknown disturbances. The proposed optimal PI tracker consists of both a modified state estimator and the newly modified equivalent input disturbance (EID) estimator. The main contributions of this paper are: (1) The conventional EID estimator is significantly modified to improve the tracking performances of a system with unknown disturbances; and (2) The improved EID estimator can be simply regarded as a plug-in component of the compensator, to perform on-line optimal tracking control of square/non-square servo systems with unknown disturbances. [ABSTRACT FROM AUTHOR]

• Electrohydraulic shaking table (EHST) system includes servo and target controller. • The effective frequency bandwidth is extended by new designed servo controller. • An adaptive power level control algorithm is proposed for target control. • Experiment was conducted on a 3-ton EHST system with a 1.2 m × 1.2 m table. • The results show the system can finally match the target within an accuracy of ±3 dB. Active vibration control using electrohydraulic shaking table (EHST) system is widely applied in civil engineering, automotive industry, environmental vibration testing and other situations where large actuating forces are needed. However, the electrohydraulic actuators (actuating systems) often suffer from drawbacks of limited frequency bandwidth, varying system parameters and so forth. In view of the limits mentioned above, this study hopes to seek out proper solutions to minimize the influence from those drawbacks. We first design a full state feedback-feedforward servo controller, which is able to extend the frequency bandwidth of EHST system, by constructing the analytical models of the servo valve and hydraulic cylinder. Numerical simulations show that the proposed servo controller is able to compensate for the attenuation-band of hydraulic cylinder and thus improve the upper frequency limit of the whole system to a degree that is higher than the natural frequency of servo valve. Afterwards, we propose a frequency domain adaptive power level control (APLC) algorithm for solving the problem of parametric variations of EHST system in application of power level control (i.e., simulate vibration based on certain power spectrum). Numerical simulations show that although APLC algorithm is not able to get exactly same spectrum and waveform at every independent trial, the power level of every trail will finally converge to the target power spectrum. Finally, an experimental validation was conducted based on an EHST system with 3 ton maximum force and 1.2 m × 1.2 m horizontal table. The results show that the proposed algorithms have greatly improved the effective bandwidth and the power level of the controlled system response can finally match the target power spectrum within an accuracy of ±3 dB. [ABSTRACT FROM AUTHOR]

This paper presents a detection system which generate an alarm if exist an anomaly state in the stability control system of an aircraft. A servo type controller with integrator for the regulation of the Roll, Pitch and Yaw was designed starting from the lateral longitudinal and dimensional model. The models are excited with steps of random sizes and disturbed with different random signals to generate the database of suitable and non-suitable states. Radial base classifiers were trained and validated for its use in the detection of anomalous behaviors that may occur in the aircraft stability. The accuracy obtained with the classifiers was greater than the 93.33% for all the variables studied, indicating that classification techniques used, offer reliability in the determination of anomalous States in the simulation of the flight of the aircraft and that could be used in reall flights [ABSTRACT FROM AUTHOR]

Rotation modulation can significantly improve the navigation accuracies of an inertial navigation system (INS) and a strap-down configuration dominating in this type of INS. However, this style of construction is not a good scheme since it has no servo loop to counteract a vehicle manoeuvre. This paper proposes a rotary upgrading method for a rotational INS based on an inertially stabilized platform. The servo control loop is reconstructed on a four-gimbal platform, and it has the functions of providing both a level stability relative to the navigation frame and an azimuth rotation at a speed of 1:2°/s. With the platform's rotation, the observability and the convergence speed of the estimation for the initial alignment can be improved, as well as the biases of the gyroscopes and accelerometers be modulated into zero-mean periodic values. An open-loop initial alignment method is designed, and its detailed algorithms are delivered. The experiment result shows that the newly designed rotational INS has reached an accuracy of 0.38 n mile/h (CEP, circular error probable). The feasibility and engineering applicability of the designed scheme have been validated. [ABSTRACT FROM AUTHOR]

In the framework of the ALOHA project (Astronomical Light Optical Hybrid Analysis), devoted to high resolution imaging in the L band, we investigate in this paper the possibility to deploy fibre links between the telescopes of the CHARA Array. As a first step, we set up an outdoor hectometric fibre interferometer to measure the vibration environment at the Mount Wilson Observatory. The optical path difference of this interferometer has been actively stabilised within an accuracy better than 4 nmrms, a stability largely sufficient for any interferometric application. [ABSTRACT FROM AUTHOR]

Highlights • A servo-controlled heliostat has been designed and built for atmospheric studies. • It enables to track the Sun for several hours with a great stability. • The spectrometer can be placed at a long distance from the heliostat (>10 m). • The instrument was validated by recording atmospheric spectra by FTIR spectrometry. Abstract The spectrometry is an important tool for atmospheric studies. In particular, passive spectrometric analysis implies associating a spectrometer with a heliostat. Indeed the heliostat enables to compensate for the Earth rotation relative to the Sun. In this way the sunlight can be collected at any time in order to detect atmospheric gases. Unfortunately, the instruments described in the literature need to be placed close to the spectrometer (< 5 m) that is insufficient for the layout of our laboratory. So a servo-controlled heliostat, which is able to track the Sun with a great stability for several hours and which can be placed at a big distance from the spectrometer (> 10 m), has been designed and built. [ABSTRACT FROM AUTHOR]

To improve the speed and accuracy of the photoelectric tracking and pointing platform stable tracking, we took the three-axis photoelectric tracking platform, of which the coupling among the rings is ignored, as the research object. Considering the effects of various disturbances, the stable tracking double closed-loop servo control system was built for the azimuth, pitch, and roll rings. In the stabilization loop, output-feedback H8 controller based on linear matrix inequality was designed to reduce the effects of model perturbations and uncertainties and to maintain the stability of the platform's inertial space. In the tracking loop, the integral-separation proportional integral derivative (PID) controller was designed to achieve fast and accurate tracking. Smith estimated compensation was adopted to compensate the pure lag caused by video tracking. Finally, the double closedloop servo control system was built to complete the simulation. The simulation results show that the system not only has good robustness under external disturbances, but also completes the attitude tracking quickly and accurately. Besides, the tracking error is |error| < 5·e-4 rad, which meets the tracking accuracy requirements. [ABSTRACT FROM AUTHOR]

High-speed wire electrical discharge machining (WEDM-HS) of materials of super-high thickness (more than 1000 mm) is a challenging problem. First, sufficient energy is required to maintain the inter-electrode normal discharge. Next, there must be adequate inter-electrode dielectric fluid. Third, in order to generate a smooth cut surface, it is necessary to suppress the vibration of the wire electrode to reduce vibration lines on the cutting surface. To better understand these challenges, the energy and the flow of the medium between two electrodes were analyzed, allowing the establishment of a relevant model. The results indicated that for super-highthickness machining, the pulse energy must be adequate to compensate for the energy consumed in the molybdenum wire and inter-electrode working liquid. In addition, the running speed of the wire electrode should be improved to ensure that there is a sufficiently high flow rate of the dielectric fluid. The servo control mode of the existing machine tools and dielectric fluid were improved and then a process experiment was performed. The experimental results show that the process can be carried out efficiently and stably and the workpiece surface can be cut smoothly using the improved working liquid and servo control mode. [ABSTRACT FROM AUTHOR]

Aiming at the problems of low localization rate of hollow glass storage system and the high cost of imported products, the hollow glass storage system was studied, the movement mechanism and electrical control in the process of storage of hollow glass at home and abroad were summarized, an intelligent hollow glass storage system based on servo control, and designs for access and storage mechanism, transportation equipment and the control device of hollow glass intelligent warehousing were and proposed the function modules of the storage system were installed. The overall block diagrams of the equipment in the system, the operation mode, the motion control flow and so on were described in detail. Taking a set of servo control equipment as an example, the software simulation and actual measurement of the precise position were carried out. The results indicate that the system can monitor the motion parameters in real time, and can realize the precise position control function, has high reliability and meets the requirements of precise positioning. [ABSTRACT FROM AUTHOR]

A LabVIEW software platform and simple hardware were used to develop the digital servo principle experiment system in this article. The LabVIEW software was used to design the man-machine interface which was used to describe the experimental curve, control parameters, setting and computing. The sensor signals were collected with the data acquisition card, the PWM control signals were reported, also. Then, a DC motor was controlled by DC motor driving circuit when the control signal was achieved. The electric current and speed signal which were generated by encoder and current sensor were achieved with the sampling card. The load was provided though magnetic powder brake in this experiment system. The DC motor and sensor were used to replace the servo motor,and the LabVIEW software was used to simplify programming in this system. Open loop, closed loop, double closed loop and feed forward control could be realized, different control parameters could be set, also. The real-time experimental curve could be get under all kinds of control mode and parameters at the same time. The servo control principle could be full displayed. The students can fully understand the servo control principle and servo motor control method through this experiment system. [ABSTRACT FROM AUTHOR]

Servo system is widely used in NC machines and its performance directly determines the precision of the machines. In most situations, the control structure for the servo system usually contains a cascaded P-PI feedback controller and a feedforward controller. This paper focuses on the feedforward controller parameters tuning to improve the servo performance. The feedforward controller consists of a model inversion and a parameterized disturbance model. Its parameters are tuned iteratively using the last cycle motion results. This method has the good extrapolation capability to the references and the performance improvement capacity. Moreover, it is easy to implement in real machines due to the simplicity and thus is of interest to control engineers. Experiments are carried out on an industrial prototype system. The results show that the proposed tuning method can improve the servo performance rapidly and the references are not required to keep the same during the tuning process. [ABSTRACT FROM AUTHOR]

Based on sliding mode control theory, in this paper a control method of tension control system in printing machine is presented. Firstly, a sliding mode controller for decreasing steady-state error is designed based on the servo motor model in the tension control system of printing machine, and the simulation verification is carried out in the MATLAB/Simulink. Further the hardware circuit is implemented through the design of operational amplifier to reduce the chattering of the system, and the trapezoidal wave is served as the input signal to reduce the overshoot of printing machine generated at the moment of start and stop, ensuring the smooth start and stop of the system. With the simulation results and the experimental results being consistent, it illustrates the correctness and practicality of the proposed method. [ABSTRACT FROM AUTHOR]

High-precision, stable tracking technology on a mobile platform is a key technology for realizing the integration of airborne search and tracking. In this study, coarse-fine compound technology based on gyrostabilization and miss tracking is applied. First, the working principle of the coarse and fine composite system is analyzed, and then the coarse and fine composite algorithm is modeled. Thereafter, the error of the coarse and fine composite axis is analyzed, and the precision tracking servo control algorithm is designed. Finally, using the model and algorithm designed to control the single reflector and galvanometer, the coarse tracking of the space target and the fine tracking of the source are completed under the condition that the equivalent sine amplitude is 5 deg and the frequency is 0.2 Hz. At the same time, a test system was built for performance verification. The algorithm achieved a coarse-tracking azimuth-axis tracking accuracy [root mean square (RMS)] of 26.3 μrad and a pitch-axis tracking accuracy (RMS) of 28.9 μrad. After composite tracking was switched on, precision tracking azimuth-axis tracking accuracy (RMS) improved to 7.9 μrad and pitch-axis tracking accuracy (RMS) improved to 6.3 μrad, both better than 10 μrad. This study provides new insights into the stability and precision tracking of single cameras on airborne platforms. At the end of this work, the outdoor experiment to verify the influence of random interference on the system performance under given conditions and the subsequent optimization direction of the system are given. [ABSTRACT FROM AUTHOR]

For laser tracker photoelectric tracking servo control system's performance requirements such as high precision，speediness and real-time，the paper analyzed photoelectric tracking servo control system's structure scheme and function，put forward "three-ring feedback + fuzzy correction" control structures of current，speed and position，designed fuzzy PID control algorithm，selected suitable motors， servers， circular grating，DSP and other key components. Through actual prototype's tracking performance test， the system's stochastic dynamic tracking performance was fine，and the maximum angular acceleration could be more than 200 °/s2，angular velocity could be 40°/s，the tracker's speed closed loop bandwidth could be over 23 Hz. Test results showed that the system dynamic tracking performance had meet the requirements of design indexes. [ABSTRACT FROM AUTHOR]

We propose local magnetic actuation (LMA) as an approach to robotic actuation for surgical instruments. An LMA actuation unit consists of a pair of diametrically magnetized single-dipole cylindrical magnets, working as magnetic gears across the abdominal wall. In this study, we developed a dynamic model for an LMA actuation unit by extending the theory proposed for coaxial magnetic gears. The dynamic model was used for closed-loop control, and two alternative strategies—using either the angular velocity at the motor or at the load as feedback parameter—were compared. The amount of mechanical power that can be transferred across the abdominal wall at different intermagnetic distances was also investigated. The proposed dynamic model presented a relative error below 7.5% in estimating the load torque from the system parameters. Both the strategies proposed for closed-loop control were effective in regulating the load speed with a relative error below 2% of the desired steady-state value. However, the load-side closed-loop control approach was more precise and allowed the system to transmit larger values of torque, showing, at the same time, less dependence from the angular velocity. In particular, an average value of 1.5 mN$\cdot$m can be transferred at 7 cm, increasing up to 13.5 mN$\cdot$m as the separation distance is reduced down to 2 cm. Given the constraints in diameter and volume for a surgical instrument, the proposed approach allows for transferring a larger amount of mechanical power than what would be possible to achieve by embedding commercial dc motors. [ABSTRACT FROM PUBLISHER]

Aiming at servo control of high-performance permanent magnet brushless motor, the physical structure, the mathematical model and the principle of permanent magnet brushless motor were researched. After the introductions of the principle of traditional PID controller and the control system of permanent magnet brushless motor, the defects of brushless motor control system based on traditional PID controller were analyzed and summarized, an intelligent control strategy of permanent magnet brushless motor based on Neuron PID was proposed. Firstly, the characteristics of Neuron PID controller were expounded. Then the algorithm of the Neuron PID control system was designed and implemented, the Neuron PID controller was used in control of speed loop of permanent magnet brushless, utilizing the self-learning ability of Neuron PID, control parameters can be trained and adjusted in real time. At last, simulation of permanent magnet brushless motor control system based on traditional PID and Neuron PID were given with Simulink, both the results of simulation were compared. The results indicate that the system can improve the response of speed and the rotational stability of brushless motor. [ABSTRACT FROM AUTHOR]

The stick-slip is one of negative phenomena caused by friction in servo systems. It is a consequence of complicated nonlinear friction characteristics, especially the so-called Stribeck effect. Much research has been done on control algorithms suppressing the stick-slip, but no simple solution has been found. In this work, a new approach is proposed based on genetic programming. The genetic programming is a machine learning technique constructing symbolic representation of programs or expressions by evolutionary process. In this way, the servo control algorithm optimally suppressing the stick-slip is discovered. The GP training is conducted on a simulated servo system, as the experiments would last too long in real-time. The feedback for the control algorithm is based on the sensors of position, velocity and acceleration. Variants with full and reduced sensor sets are considered. Ideal and quantized position measurements are also analyzed. The results reveal that the genetic programming can successfully discover a control algorithm effectively suppressing the stick-slip. However, it is not an easy task and relatively large size of population and a big number of generations are required. Real measurement results in worse control quality. Acceleration feedback has no apparent impact on the algorithms performance, while velocity feedback is important. [ABSTRACT FROM AUTHOR]

• A new multi-function servo control dynamic shear apparatus is developed. • It can perform the servo control in both vertical and horizontal directions. • It can also preform the coupled shear-flow test. In this paper, we report a new multi-function servo control dynamic shear test apparatus, DJZ-500. This apparatus consists of five parts, including power system, loading frame, servo control unit, cooling system and PC console. The normal load and shear load are measured by load cells with an accuracy of 0.1 kN; normal and shear displacement are measured by LVDTs with an accuracy of 0.1 μm. DJZ-500 has the dynamic and static loading modules, which can perform the force and displacement servo control experiments in both vertical and horizontal directions. In addition, the dynamic loading modules can execute the custom waveforms, which can be utilized to investigate the seismic response of rock and soil masses. We presented six sets of representative tests on sands to demonstrate these functions. Moreover, DJZ-500 can also preform the coupled shear-flow test with the pumping system to investigate the flow behavior in sheared rock fractures. This device makes up for the deficiency of the existing equipment, and promotes the study of frictional properties of geomaterials. [ABSTRACT FROM AUTHOR]

Abstract: Frequency modulation spectroscopy (FMS) is most commonly used for trace gas detection, but its sensitivity is usually limited by the background noise attributed to residual amplitude modulation (RAM). In this paper, comprehensive theoretical analyses of FMS with and without RAM are presented. Then the measurements of RAM are experimentally verified utilizing a fiber electro-optic modulator based FMS setup. In order to reduce the RAM, a novel servo control method with its correction signal obtained from a polarization detection scheme was proposed and pure FMS signals of C2H2 gas at wavenumber of 6544.4419cm−1 are obtained. Furtherly, long-term measurements of the dispersion background signal with feedback loop on and off are performed to evaluate the stability of the instrument. Finally, this servo control method is extended into the application of Pound–Drever–Hall frequency stabilization technique to improve the locking accuracy and stability. [Copyright &y& Elsevier]

Abstract: Servos (as commonly used in radio controlled vehicles and small scale robotics) are DC actuators which use a potentiometer to provide built-in feedback to localise an actuator arm. To minimise jerky control movements, many servo controllers include velocity and acceleration control which operate using a defined velocity profile resulting in the Pulse Width Modulation (PWM) control value being changed over time. On power-up the initial position of the servo arm is unknown to external controller—resulting in the arm moving to the starting value at maximum speed (which may be mechanically hazardous). In this paper two different techniques for performing a soft-start for servos are described and evaluated, namely: voltage profiling and intermittent drive. The different techniques are implemented and evaluated using four different servos based on measured velocity profiles, current consumption, and peak torque. [Copyright &y& Elsevier]

In this study, electrochemical machining (ECM), an advanced metal processing method that has not found application in Turkey, has been investigated. A new ECM device was developed by customizing a three-dimensional CNC machine for electro-chemical applications and integrating it with pulsed DC power supply, servo motor control system that provides vertical gap control, electrolyte vacuum, purification and recycle system. Controlled operation of the system within desired limits was achieved by correct design of the cathode tool, effective adjustment of the vertical gap between the anode and the cathode, accurate control of electric current and voltage values, and masking the surface of the electrodes. It was found that keeping the electrolyte concentration constant was necessary for the system stability. [ABSTRACT FROM AUTHOR]

This study presents an adaptive-type controller based on a quantum neural network and investigates its characteristics for control systems. A multi-layer quantum neural network which uses qubit neurons as an information processing unit is utilized to design three types of the adaptive-type quantum-neural-network-based controllers which conduct the learning of the quantum neural network as an online process: a direct controller, a parallel controller and an indirect controller. Computational experiments to control the single-input single-output non-linear discrete-time plant are conducted to evaluate the learning performance and capability of quantum neural controllers. The results of the computational experiments confirm the feasibility and effectiveness of adaptive-type quantum neural controllers. [ABSTRACT FROM AUTHOR]

Stable gaze scanning control technology is the key to realize the integration of stable imaging, search, and tracking on airborne platforms. We investigate the control technology of stable gaze scanning on an airborne platform. The working principle of a stable staring scanning system is analyzed, and a servo system control algorithm is modeled. The position loop, velocity loop, and acceleration loop are designed. A stability model of the space with inclination angle is established. The coordinate transformation relationship between inertial coordinate system and airborne axis coordinate system is obtained. The designed control model and algorithm are used to control the single-lens reflex mirror mounted at an angle of 15 deg for spatial gaze pointing and step scanning. A test system is built for performance verification. Results show that the root-mean-square accuracy of the proposed algorithm is higher than 10 μrad in a dynamic staring step scan with ±30 deg and a step length of 2.16 deg. The single-step time is <52 ms, the stabilization time is >53 ms, and the servo system overshoot is small. The system step accuracy root mean square is better than 52 μrad. These findings confirm the effectiveness of the integrated search and follow technology under an airborne platform. [ABSTRACT FROM AUTHOR]

A double degrees of freedom backstepping control method is proposed for large variation in load, strong disturbing torque due to launching and high tracking accuracy requirement. Control law is designed by deriving iteratively according to the mathematical model of servo system. Degree of freedom factor is used to adjust the control parameters, and the closed-loop controlling system is proved to be stable through Lyapunov function. The simulation study of the position tracking under the conditions of external disturbance and parameter perturbation was carried out, and the constant-velocity and sine-velocity tracking performances were experimentally analyzed. The simulation and experiment results show that the proposed approach can guarantee the response speed and control accuracy and has a strong robustness to the load disturbance and parameter perturbation. [ABSTRACT FROM AUTHOR]

A new procedure for the design of non-linear proportional and rate feedback controllers based on a previously proposed concept is developed. The procedure is to obtain the sinusoidal-input describing function models of the system, followed by determination of the amplitude-dependent rate feedback gains. Then, this amplitude-dependent gain function is inverted to obtain the non-linear function describing a non-linear rate feedback gain. Then, the amplitude-dependent proportional gains that desensitize the overall open-loop system are determined via optimization. Finally, the obtained amplitude-dependent proportional gains are inverted to obtain the actual non-linear function describing the required non-linear behaviour of the proportional gain. Bounded-input–bounded-output stability is demonstrated by successful generation of the closed-loop describing function models, and the procedure is applied to a servo problem; the results are compared with four other non-linear controller design procedures that were reported in the open literature. [ABSTRACT FROM PUBLISHER]

This paper is devoted to the control design and implementation of the dual-stage actuation system with a newly developed microthermal actuator (MTA) as the secondary actuator. The characterization and modeling of this new MTA is presented for controller design. Its performances such as stroke, time constant, and a good linearity are exhibited. The controller design of the MTA-based dual-stage actuation system is then proposed, and aims to push the bandwidth with the MTA. The simulation and the experimental testing have demonstrated the achievable 6-kHz bandwidth with 60-kHz sampling rate, the MTA displacement of 15 nm at 4 kHz, and 0.1-ms seeking time for 40-nm seeking length. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with position control of a single degree of freedom (sdof) manipulator actuated by Pneumatic Artificial Muscle (PAM) actuator. Though the compliance characteristics of these actuators are desirable, their inherent non-linearities due to compressibility of air and non-linear load–contraction characteristics make them difficult to model and design of controller becomes very complex. To overcome this, a novel method is hereby proposed to establish an accurate empirical model for the system. The quasi-static characteristics of the PAM are first modelled followed by the dynamic characteristics through spectral analysis. For cost competitiveness, the present work incorporates inexpensive on–off switching valves operated using a novel model based proportional pressure regulator developed using a modified PWM algorithm. Finally, a conventional PID position controller is extended using the empirical PAM model and an inner pressure regulation loop to achieve trajectory tracking of a sdof manipulator. Results for pressure regulation and position control confirm the effectiveness of the adopted approach in achieving performance comparable to the state-of-the-art results at a reduced control complexity and total set-up cost. [Copyright &y& Elsevier]

Using a parallel hydraulic Stewart-6-DOF platform as a force reflecting haptic master, the force based model is deduced and the general predictive control (GPC) theory is used for the design of the controller to control the 6-DOF parallel hydraulic force reflecting haptic master. The servo control system test bench has been set up by using a piece of the 6-DOF master. The test results show that the control system overcomes the model error and uncertainty and gain better both dynamic and static respondence. It is of certain significance for parallel hydraulic haptic master control system design. [ABSTRACT FROM AUTHOR]

Abstract: Design and implementation of servo controller for a hydraulic servo system with a load of large inertia, low stiffness and multi-stage resonance is considered. To achieve a set of desired requirements, this paper is divided into three parts of work. First, notch filters and peak filters extracted from the general phase stabilized controller are applied in order to restrain the resonance peak of the load. Second, a disturbance observer in the feedback path is used for rejecting low-frequency disturbance and high-frequency noises. Third, as the complete inversion of the closed-loop dynamics at the whole frequency band does not necessarily give the best performance, low-pass filter, proportional derivative (PD) compensation, and lead correction are adopted in the feedforward path. The work proposed here overcomes the challenge of improving amplitude margin and phase margin while eliminating resonance simultaneously. The effectiveness of the combined control is investigated through simulation and experiment results, which show that the control strategies raised here successfully complete resonance rejection and also give ideal performances that meet the indices. [Copyright &y& Elsevier]

Abstract: Pseudo-derivative feedback with feed-forward gain (PDFF) combines the advantages of proportional-integral (PI) and pseudo-derivative feedback (PDF) controllers. However, PDFF responds more slowly to a command than does PI. To increase the speed of response of the PDFF controller, this work presents a PDFF with moving average errors control. A low-pass IIR filter path for errors compensation that accelerates the slow response is added to a PDFF control loop. A fuzzy inferencer is utilized to adjust the feed-forward gain and integral gain of the PDFF controller to allow closed-loop poles of the transfer function to be properly placed to improve load torque disturbance rejection capability. Simulated and experimental results reveal that the response and load disturbance rejection ability of the fuzzy PDFF-IIR controller are better than those of the traditional PDFF controller. [Copyright &y& Elsevier]

Advanced control strategies, such as a model-based control, are essential to improve accuracy of servo hydraulic actuators in structural testing. Such control strategies require a servo-loop, often referred to as an inner-loop, of the actuator to be digitally controlled. To make the best use of digitally controlled inner-loops that have numerous advantages over conventional analog counterparts, a thorough understanding of the actuator inner-loop is needed. This study presents an error analysis of digitally controlled servo hydraulic actuators with a focus on sources and growth of errors in the actuator inner-loop. First, effects of errors such as measurement errors and electrical noises on the performance of servo hydraulic actuators are analytically investigated. Then, using detailed models of those errors and an open-loop servo hydraulic actuator, an extensive numerical simulation is performed to evaluate the effect of errors on the actuator performance. Numerical results show that the displacement measurement error has an undesirable influence on the actuator responses in the high-frequency range. Such responses make it difficult to accurately assess structural and nonstructural systems in the high-frequency range using the hydraulic actuators. In particular, velocity and acceleration responses of the hydraulic actuator are highly sensitive to the displacement measurement error. This investigation provides fundamental knowledge that is required for an effective use of digitally controlled servo hydraulic actuators. [ABSTRACT FROM AUTHOR]

Lateral motion of the magnetic tape in data storage applications misaligns the flexible medium relative to the recording head and reduces the potential for decreasing data track width and spacing, and thereby the achievable data storage density. In order to reduce the effect of misalignment between the tape and the recording head, the head is mounted on a track-following actuator that can compensate for the position error up to a frequency that is governed partly by its mechanical resonances; this bandwidth is typically 1 kHz or less for conventional voice coil-based actuators. This paper introduces the design and implementation of a track-following actuator that is piezo-electrically actuated in order to potentially achieve a significant increase of bandwidth and positioning precision. A proof-of-concept is prototyped and experimental results are presented. An H\infty controller is designed and implemented to compensate for typical disturbances such as periodic runout of packs and rollers, or non-periodic flange impacts. Preliminary closed loop experimental results with an experimental low lateral motion tape path, and conventional servo format and media demonstrate a reduction in positioning error standard deviation to 74.5 nm, with simulations indicating a potential for further improvement to 20.6 nm with the use of improved media and servo format. [ABSTRACT FROM AUTHOR]

The paper proposes a control scheme for detecting and compensating the low-frequency vibrations in hard disk drive systems. A vibration detector is proposed, utilizing the down-sampled position error signal (PES). Due to the performance limitation in loop shaping, attenuating low-frequency vibration is usually penalized by high frequency disturbance amplification. This paper proposes an adaptive scheme to intelligently adjust a vibration reduction factor, such that when vibration level is low, the servo loop maintains its normal operation mode, and little or no compensation is carried out. Experiments on hard disk drives on a vibration shaker validated the effectiveness of the proposed compensation scheme. [ABSTRACT FROM AUTHOR]

Abstract: Rotor position detection is important for motor servo system design. In general, there are two kinds of methods to obtain the position information in real time, sensor or sensorless methods. The sensor methods use position sensors such as optical encoder. This will greatly increase the cost of the system, and the sensor with high precision is difficult to be installed. On the other hand, the sensorless method can reduce the cost, but the reliability and complexity of the algorithm is still the problems. In this paper, a new low-cost integrated position feedback unit, which is composed of the integrated position sensor, signal processing hardware and software, is described. The sensor is easy to manufacture and has better precision with the help of signal processing circuit and software based on DSP. The sensor can obtain absolute rotating angle using inductance detection method, and it is originally designed and used for a 2-phase hybrid stepping motor position servo system. The integrated sensor and the proper control strategy make the system become a low-cost high-performance position servo system. Even though the feedback unit is originally designed for a 2-phase hybrid stepping motor, the same unit also can be used with other types of motors. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the effect of read head profile on the playback signal from data and servo sector in a staggered bit-patterned-media recording system. The scaling of the read head is targeted to achieve better data signal quality while such scaling is shown to have negative effect on the servo signal. A secondary servo burst that uses data samples to generate supplementary PES is then proposed and its feasibility is demonstrated. [ABSTRACT FROM AUTHOR]

In this paper we present the idea of hybrid servo track writing and give a complete description of the developed hybrid servo track writer platform including its main functions and servo mechanism. The major disturbances and noise level in media-level servo track writing are identified based on the position error signal measured on the hybrid servo track writer platform. A dual-stage servo system, which is applicable in servo writing, is proposed and implemented on the experimental platform. With the disturbances and noise models, an advanced loop-shaping scheme based on Kalman-Yakubovic-Popov lemma is used to optimize the controller for the micro-actuator servo loop. The experimental results show that the tracking accuracy can reach 6 nm, which is able to support a track density of more than 400 000 tracks per inch. [ABSTRACT FROM AUTHOR]

Abstract: Digital servo control was introduced in mass production hard disk drives (HDD) in 1986. Since then various kinds of digital control technologies have been applied to HDD servo systems, and the performance has been improved dramatically. A 3.5-in. HDD capacity, which was 251MB in 1988, is 2000,000MB (2.0TB) in 2009. Faster access (high quality motion control), more precise positioning (nanometer scale control), and more robustness against disturbances and plant fluctuations are required to meet the increasing demand for larger capacity and higher performance HDDs. The field of HDD servo technology provides an example of techniques for micro or nanometer accuracy. Although the application aspects may be different in other fields requiring high positioning accuracy, the methods used in HDDs are general enough that they can be transferred. This paper is not intended to act as a review paper, but presents several fundamental ideas of precision positioning servo control, especially ones derived from the history of HDD servo control. [Copyright &y& Elsevier]

This correspondence presents servo and nonlinear model following controls for a class of nonlinear systems using the Takagi-Sugeno fuzzy model-based control approach. First, the construction method of the augmented fuzzy system for continuous-time nonlinear systems is proposed by differentiating the original nonlinear system. Second, the dynamic fuzzy servo controller and the dynamic fuzzy model following controller, which can make outputs of the nonlinear system converge to target points and to outputs of the reference system, respectively, are introduced. Finally, the servo and model following controller design conditions are given in terms of linear matrix inequalities. Design examples illustrate the utility of this approach. [ABSTRACT FROM AUTHOR]