Search

Permanent magnet synchronous motors (PMSMs) with non-concentric magnetic poles (NCMP) structure are widely used as high-precision servo motors. The current subdomain method mainly equates the NCMP to a rectangular magnet to make each subdomain boundaries of magnet parallel when calculating the magnet eddy current loss (ECL), which results in a lower accuracy of the calculation. This paper divides the NCMP into non-concentric region and concentric region along the radial direction. The non-concentric region is further divided along the circumferential direction, and each divided region has a single thickness. Based on the subdomain method, a novel analytical method of magnet ECL in PMSMs with NCMPs is proposed. Moreover, the 3-D distribution coefficient of ECL in the NCMP is derived by the equivalent impedance method. The effects of eddy current reaction and stator slotting are taken into account to improve the calculation accuracy. Then, through theoretical derivation, the relationship between the minimum magnet loss and the pole parameters is obtained, which provides a reference for the design of NCMPs. Finally, the loss separation experiment is performed on four prototypes with NCMPs. The experimental results, finite element method results and analytical results are compared to verify the correctness of the model.

In dual-motor servo systems, several factors seriously affect the tracking performance especially in high-speed and high-accuracy situations, which include machinery flexibilities, torque disturbance, unmodeled dynamics, and motor parameter differences. Given these factors, this article investigates the command filtered backstepping synchronization control (CFBSC) method for a servo system driven by two motors synchronously. Command filters are used to deal with the virtual control signals in backstepping design process to avoid the computational burden causing by repeated derivatives, and a compensation system is applied to reduce the tracking error. Adaptive control is used to compensate the torque disturbance and unmodeled dynamics. In addition, the speed and torque synchronization control signals are designed to guarantee high synchronization performance. The stability of the dual-motor servo system is proved. And the effectiveness of the proposed controller is validated through experiments.

Orbital debris in Earth orbit poses a threat to the future of spaceflight. To combat this issue, this paper proposes a novel robotic mechanism for non-cooperative capture and active servicing missi...

The sinusoidal encoder is used as an absolute position (velocity) transducer to implement the position (velocity) of actuators in many industrial applications. However, the performance of the position (velocity) can be degraded due to nonideal factors such as differential amplitudes of the encoder signals, offset, and phase shift. To analyze this problem, we formulate the relationship between the coefficients of ideal signals and the nonideal signals characteristic, which is an ellipse formed by plotting the encoder signals versus each other. In this article, we propose a nonideal signal calibration for the imperfect components of existing sinusoidal signals to improve position (velocity) regulation performance. The fictitious cosine function is used to detect the phase shift between the sine and cosine signals, and it can be designed by using the frequency of sinusoidal signals. The proposed method is validated by simulation and experimental implementation, showing noticeable improvement in estimating nonideal signal components, Lissajous error curve, phase distribution, and the position (velocity) error signal. Experimental results show that the proposed method is able to obtain the components of the nonideal signals and the accurate position (velocity) with a small error in real time, while other calibration methods are difficult to apply to fast motion.

This article investigates a class of linear–nonlinear switching active disturbance rejection control (ADRC) to design speed controllers and current controllers for permanent magnet synchronous machine (PMSM) in servo systems, which aims at enhancing the ability of disturbance rejection of speed and current controllers for PMSM. First, the mathematical model of PMSM is introduced. Next, the design of a class of linear–nonlinear switching ADRCs is introduced in details. Then, the stability of linear–nonlinear switching extended state observers (ESOs) is proved by multiple Lyapunov functions. Lastly, the effectiveness of the speed and current controllers based on the linear–nonlinear active disturbance rejection technique is validated by experiments results of a 5.5-kW PMSM platform. Specially, the experiment results of the speed controllers illustrate that the amplitude of speed change of the proposed ADRCs is smaller than that of the linear ADRC (LADRC) when the step load torque disturbance occurs. The proposed ADRCs can overcome the overshoot of speed response caused by improper parameter setting of LADRC. The experiment results of the current controllers show that the proposed LNSADRC type 2 has greater robustness than the other ADRC controllers when $b_{02}$ is not estimated accurately.

This study investigated the performance of an antirolling system based on the Magnus effect at zero speed. The test scheme and control method were designed based on a proportional integration differentiation controller. A scaled ship model equipped with an attitude monitoring and control implementation feedback system was developed. The effects of different swing speeds and angles, cylinder surface shapes, number of effective cylinders, and target ship model rolling angles on the performance of the antirolling system were studied using a shipborne gravity slider and normal transverse regular wave. The Magnus antirolling system exhibited a better swing speed range compared to conventional methods, and its performance improved as the swing angle increased. During the zero-speed antirolling test, the velocity loop control provided a better antiroll damping effect on the ship model than the position loop control, and the bionic cylinder improved the performance more than a smooth cylinder. Moreover, the system retained good antirolling capabilities even in partial failure cases (i.e., operating with fewer cylinders). This study can contribute to the research of ship seakeeping strategies.

Traditional surface permanent magnet synchronous motor (SPMSM) used as a servo motor limits the miniaturization and performance improvement of industrial robot, due to its large overall volume and heavy weight of the rotor. In this article, a novel transverse flux permanent magnet motor with a hybrid stator core and disk-type rotor (HSDR-TFPM) is proposed to adapt to the industrial robot well. Moreover, a better space design by which the usual components used in industrial robot is considered. Considering the computing time and accuracy, an analysis method based on Schwarz–Christoffel mapping is employed to analyze the magnetic field of HSDR-TFPM and conduct research on motor parameters. In order to prevent the axial movement of rotor, the detailed mechanical design is introduced and the strength of motor is analyzed further. In the end, the analysis results and performance of the proposed HSDR-TFPM are validated and compared with a conventional servo SPMSM.

This article details the design, working principles, and testing of a novel position control mechanism for marine operations or inspection in extreme, hostile, or high-speed turbulent environments where unprecedented speed and agility are necessary. The omnidirectional mechanism consists of a set of counter-rotating blades operating at frequencies high enough to dampen vibrational effects on onboard sensors. Each rotor is individually powered to allow for roll control via relative motor effort and attached to a servo-swashplate mechanism, enabling quick and powerful manipulation of fluid flow direction in the hull's coordinate frame without the need to track rotor position. The mechanism inherently severs blade loads from servo torques, putting all load on the main motors and minimizing servo response time, while exploiting consistent blade momentum to minimize the corresponding force response time. A small-scale force-validating model is fabricated and tested for various force and moment commands. Kinematic and hydrodynamic analyses of the hull and surrounding fluid forces during various blade maneuvers are presented, followed by the mechanical design and kinematic analysis of each subsystem in a small scale model. Experimental results of the small-scale model are presented that verify the concepts presented for the larger-scale model. Finally, an open-loop controller is constructed with decoupled parameters for each degree of freedom.

Unmanned Aerial Vehicles (UAVs) have continually proven their effectiveness in various fields. However, UAVs have not yet matured enough to be used for vertical surface maintenance tasks, such as building inspection or cleaning. To mitigate this issue, this letter proposes a novel design for a coaxial hexarotor (Y6) with a tilting mechanism that can morph midair while in a hover, changing the flight stage from a horizontal to a vertical orientation, and vice versa, thus allowing wall-perching and wall-climbing maneuvers. Furthermore, a rotor offset design has been adopted, in which the tilting rotors are offset from the tilting axle by a certain distance. In this configuration, the required distance between the wall and the platform is reduced, improving stability and increasing the opportunity to enhance power efficiency. However, owing to the rotor offset, the servo motor slows down and the tilting angle is one-way constrained. These conditions can cause a critical issue with the conventional control method. To tackle the problem, a novel control method called quasi-decoupling control is proposed. Our proposed method attains promising performance, overcoming the limitations of a servo motor's slow dynamics and angular constraint.

In this article, the issue of position-tracking control of servo system with external disturbance is studied. A novel hybrid second-order sliding-mode control (HSSMC) strategy is proposed. To be specific, first, the uncertainties of motor parameters and load torque are considered as lumped disturbance, and an adaptive extended sliding-mode disturbance observer (AESMDO) is designed in order to estimate the disturbance. Second, a new terminal sliding-mode function is presented, and a super-twisting controller based on AESMDO is designed. In which, a nonlinear switching term is brought to weaken the chattering of the system. Furthermore, the convergence of terminal sliding-mode surface and the stability of controller are proved. Finally, the simulation and experiment are executed to verify the effectiveness of the proposed method.

People taken by upper limb disorders caused by neurological diseases suffer from grip weakening, which affects their quality of life. Researches on soft wearable robotics and advances in sensor technology emerge as promising alternatives to develop assistive and rehabilitative technologies. However, current systems rely on surface electromyography and complex machine learning classifiers to retrieve the user intentions. In addition, the grasp assistance through electromechanical or fluidic actuators is passive and does not contribute to the rehabilitation of upper-limb muscles. Therefore, this paper presents a robotic glove integrated with a force myography sensor. The glove-like orthosis features tendon-driven actuation through servo motors, working as an assistive device for people with hand disabilities. The detection of user intentions employs an optical fiber force myography sensor, simplifying the operation beyond the usual electromyography approach. Moreover, the proposed system applies functional electrical stimulation to activate the grasp collaboratively with the tendon mechanism, providing motion support and assisting rehabilitation.

In this article, an adaptive repetitive learning control (ARLC) scheme is proposed for permanent magnet synchronous motor (PMSM) servo systems with bounded nonparametric uncertainties, which are divided into two separated parts. The periodically nonparametric part is involved in an unknown desired control input, and a fully saturated repetitive learning law with a continuous switching function is developed to ensure that the estimate of the unknown desired control input is continuous and confined with a prespecified region. The nonperiodically nonparametric part is transformed into the parametric form and compensated by designing the adaptive updating laws, such that a prior knowledge on the bounds of uncertainties is not required in the controller design. With the proposed ARLC scheme, a high steady-state tracking accuracy is guaranteed, and comparative experiments are provided to demonstrate the effectiveness and superiority of the proposed method.

This article presents a sensorless machine drive scheme, combining the motion model predictive control (MPC) in the speed loop and the position estimation in the current loop. The current-loop-based position estimation algorithm is to estimate the present rotor position with the phase current information of the previous samples. These methods cannot perform perfectly in the low speed when a heavy load suddenly occurs, as the aggressive motion disturbance can impact the convergence of the low-speed position estimation, or even make divergence and estimation failure. This issue is especially terrible for the surface permanent magnet synchronous machines (SPMSMs), as the magnetic saliency is weak at heavy loads. The target of this article is to solve this issue with respect to the servo system, where the machines need to frequently start and stop with heavy loads, and hence the above risk must be considered. The convex optimization is applied in the position estimation, and the optimization cost value is extended to adjust the injection amplitude and the reference trajectory of the MPC control. With this strategy, the sensorless control can operate with a high stability and accuracy. The scheme is validated in an SPMSM test bench.

The performance of the electromechanical actuator (EMA) in the aircraft braking system suffers from the system’s nonlinear characteristics, whereas the robust control can contribute to the improvement of tracking precision in its servo system. In this article, a chattering suppression fast terminal sliding mode (FTSM) control strategy with an embedded nonlinear disturbance observer (NDO) is proposed for the EMA braking system, which can retain the fast convergence characteristic of the classical FTSM and guarantee the system converges to equilibrium point timely. Moreover, the singularity problem of the classical FTSM control is resolved through the well-designed sliding mode manifold. The NDO is designed to estimate the uncertain factors online, including time-varying parameters, external disturbance, and unmolded dynamics of the EMA system. By applying the compensation terms into the control law, the proposed control strategy can alleviate the chattering problem and improve system stability. To verify the performance of the proposed control strategy for EMA, wheel braking tests are conducted under various conditions regarding the type of runway and failure cases. The results indicate that the proposed control strategy can guarantee the servo performance, the control precision, and the response speed of the EMA servo system.

In this article, a novel multirotor unmanned aerial vehicle (UAV) is proposed for enhanced locomotion and manipulation in unstructured environments. The vehicle has a tilting-rotor architecture. Specifically, two pairs of rotors are mounted on two independently controlled tilting arms placed at two sides of the vehicle, forming an “H” configuration. Such a structure endows the vehicle with more degrees of freedom, improving the maneuverability without sacrificing energy efficiency at the cost of only two additional servos compared to traditional quadcopters. Based on this architecture, a dual-level adaptive robust control is developed to cope with inertial parametric uncertainties and uncertain nonlinearities for accurate motion tracking. To resolve the redundancy in actuation, a thrust force optimization problem minimizing power consumption while achieving the desired body force wrench is formulated and solved precisely and efficiently. With the novel design and control, the proposed aerial vehicle is capable of achieving superior maneuverability, better stability and motion accuracy in the presence of uncertainties, as well as improved power efficiency compared to traditional UAVs when performing dexterous aerial locomotion and manipulation. To demonstrate the advantage of the proposed new UAV design and control in real applications, we conduct four challenging experiments on aerial locomotion and manipulation: circular trajectory tracking, passing through a narrow tunnel, picking up an object from a cluttered shelf, and aerial hole drilling. Experimental results validate the applicability of the proposed innovation.

This work focuses on the implementation and design of a six degree of freedom, 6-DOF control of automatic color sorting and pick and place tasks for a robot arm using wireless controlling interface – Blynk apps. Based on the collaboration between the servo motor and input color sensor, this wireless control of automatic color sorting robot arm provides a powerful wireless control GUI (Graphics User Interface) and to enable the method for manual color sorting mode. The color sorting mode is performed once the mode is turned on by the user. The robot arm able to differentiate the colors of the object (input) and categorize or classify the object to the correct places automatically. It provides a stable, efficient, and precision results without any vibration of control as the main target for this project. In this work, six servo motors were used to realize the real robotic arm for industrial use. Five servos were operated to control the entire robot arm motion including the base, shoulder, and elbow as well as one servo is reserved for the positioning of the end effector. Two input variables namely TSC3200 Color Sensors & HC-SR04 Ultrasonic Sensors were employed as the input for the robot arm. The output variable mainly focused on the servo motor as the links for the robot arm to reposition and change the motion for the entire system.

У статті розглянуто особливості конструкції мобільних роботів-гексаподів. Встановлено, що така мобільна платформа є біонічною системою, яка використовує для пересування шість ніг та імітує своїм зовнішнім виглядом і способом пересування павука. Робот-гексапод має шість рухомих ланок, а для забезпечення його руху достатньо всього лише трьох робочих. Перевагами робота є його висока прохідність на нерівних поверхнях порівняно з колісними платформами. Розроблено лабораторний макет автоматизованої мехатронної системи «робота-гексапода». Було обрано класичну конструктивну реалізацію робота, що передбачає шість кінцівок із трьома ступенями рухомості, які розміщені симетрично по три рухомі ланки з двох сторін робота і приводяться в рух завдяки вісімнадцяти серводвигунам. Розроблено систему керування роботом, яка полягає у плануванні переміщення робота з врахуванням інформації, що надходить з датчиків, які в свою чергу забезпечують загальний зворотний зв’язок, надаючи інформацію про різні параметри зовнішнього середовища. Для здійснення рухів гексапода реалізовано відповідний алгоритм, яким передбачено розподіл на дві групи кінцівок робота та систему дистанційного керування ним. Проведено моделювання переміщення робота за допомогою ROS + Gazebo.

Recently, research on hybrid mobile robots has been attracting considerable interest due to the ability of these systems to perform service tasks in heterogeneous scenarios and irregular terrains. This article proposes a specific hybrid locomotion configuration, which combines legs and Mecanum omniwheels into a six-legged hexapod robot. Theoretical backgrounds and open issues are addressed by considering some challenging problems such as gait planning, modeling omnidirectional motion, and designing control architecture for combining locomotion modes. The article demonstrates suitability, feasibility, and successful performance of the proposed locomotion strategies and presents experimental results and novel scientific contributions regarding the motion of hybrid mobile robots.

Electromechanical actuators (EMA) composed of permanent magnet synchronous motors are extensively employed in aircraft applications. However, several multisource disturbances in EMAs bring barriers to the high-dynamic position servo systems. Most of the existing disturbance rejection methods for EMAs converge exponentially and focus on a constant disturbance. However, practical disturbances, such as load torque, are high-order. To this end, this article puts forward a novel finite-time convergent nonlinear function, enhancing the dynamic tracking performance of the servo systems. Then a novel extended state observer (ESO) is proposed to improve the estimation accuracy of high-order disturbances. The integration of the composite controller and the ESO form the multiple disturbance rejection control method, which achieves error convergence in finite time. Finally, simulation and experimental results are provided to verify the effectiveness of the proposed method.

The Arduino UNO, ultrasonic sensor, servo motor, and Processing as visual software was used to create a low cost ultrasonic radar system that can detect and determine the location of an object, such as obstacles, in a short distance. Objects can be sensed up to 40 cm away from the ultrasonic sensor and the ultrasonic radar's angular rotation can detect objects from 15o to 165o and counterclockwise. The obstacle objects will be displayed in the computer panel by running the visual software. A comparative analysis of the distance error between the radar and the obstacles is used to assess the feasibility of the proposed system. The findings obtained from measurements of the obstacles are tabled to show that the planned design achieved a relatively small error, with 90% as the lowest accuracy.

In this article, recently proposed control methods, suitable for trajectory tracking in fully actuated unmanned aerial vehicles (UAVs), are reviewed and experimentally compared. We specifically focus on multirotor platforms with tiltable propellers, for which the thrust and torque delivered by each rotor can be oriented within the aircraft frame using servo actuators. First, the main assumptions underlying the control design model usually employed in the literature are discussed, pointing out the main limitations. Then, some recent control laws that have been proposed to address the trajectory tracking problem for these platforms are reviewed, placing emphasis on their tracking capabilities as well as on the ease of tuning and implementation. Finally, experimental results obtained by applying three control laws on a tilt-arm quadrotor UAV are shown to evaluate and compare their performance. Two experiments, representative of operating conditions for thrust-vectoring UAVs, have been performed: a set-point tracking with level attitude and a full-pose trajectory tracking task.

Hole drilling and bolt screwing are frequently performed tasks in construction, decoration, and maintenance. Traditionally, sending human workers to perform these tasks in hard-to-reach locations is both dangerous and costly. In this letter, we present an aerial manipulation platform that allows a human user to remotely conduct omnidirectional drilling and screwing. The design of the platform features a quadrotor UAV with each pair of rotors independently tilted by a servo, forming an “H” configuration, on which a 1-DOF manipulator carrying a motorized drill or screw driver is mounted. With such a design, the end-effector can face any direction on the longitudinal plane and exert a big enough contact force for drilling and screwing without the need of changing the vehicle body's orientation. Compared to previous UAVs that can only drill holes vertically into the ground, the proposed design also allows horizonal drilling/screwing into a wall or a cliff, making it suitable for a vast range of real applications. Based on the dynamic equations of the system, a dual-level control law is proposed. The low-level attitude controller uses an adaptive robust control (ARC) to accurately regulate the attitude angles in the presence of force/torque uncertainties that may occur during the drilling and screwing process, while a selective impedance controller is implemented at high level to indirectly control the contact force commanded by the user. In addition, a vision-based real-time target identification and tracking method integrating a YOLO v3 real-time object detector with feature tracking, and morphological operations is developed to identify and track the target point for drilling and screwing specified by the user. Various in-lab experiments on a self-made prototype demonstrate the feasibility and effectiveness of the proposed approach for aerial drilling and screwing.

The bearingless version of the induction motor (IM) has unacceptable performance for high speed or significant power applications. This is due to design challenges that are unique to the bearingless IM, including fundamental topology differences, rotor current induced by the suspension field, and a lack of techniques that can rapidly and accurately model the machine. This article presents a complete investigation into the design topology, modeling, and optimization of bearingless IMs to identify high-efficiency, power-dense designs for a high speed industrial compressor system. Key differences in the design of the bearingless IM from that of the classical line-fed IM are explored and an analytic design approach is proposed. A pole-specific rotor and a combined stator winding are used to improve the machine performance. Computationally efficient finite element modeling techniques are proposed and evaluated based on their ability to accurately calculate bearingless IM design performance metrics. An optimization framework is developed around these advancements using the multiobjective evolutionary algorithm based on decomposition. This article exercises this framework to explore the design space of four different slot-pole combination bearingless IMs for a 50 kW, 30 000 r/min compressor. High performance designs are identified that achieve $>96\%$ efficiency with a torque density competitive with high performance servo motors that use contact bearings.

A foreign fluid that enters the patient can cause some bodily reactions including infection, air embolism and blood clot. Side effects given will be fatal to the body, one of which occurs the blockage of the capillary vessels in the heart that can cause heart attack to stroke. The purpose of this research is to design a tool that can be used to measure maximum pressure as a form of the calibration of the syringe pump and infusion pump. The contribution of this research is that the system can simulate the presence of blockages in fluid flow and detect large pressure values detected by the Under Test Unit (UUT) with a motor peerround system that opens/closes fluid flow. Servo Motor MG966R simulate the presence of blockage with constant motor degree until the alarm UUT reads, then Sensor XGZP6887 detects the pressure generated by the blockage and processed by the microcontroller and displayed on the LCD display of the character. This study resulted in a maximum pressure average value of 7.12 Psi. The results showed that data retrieval had an error value of -0.12. This research can be implemented to perform pressure measurements on the syringe pump or infusion pump.

Resolver, as an electromagnetic sensor, is widely used in different industrial applications such as servo motor feedback applications because of its reliable performance in the presence of undesired external factors in a harsh environment. Among different types of resolvers, variable reluctance (VR) resolvers draw attention due to their robust structure with a winding-less solid rotor and low-cost manufacturing. In this article, analytical modeling based on the magnetic equivalent circuit (MEC) is employed to investigate the output signals of the proposed toroidal winding arrangements for VR resolver with a 5-X rotor. Time-stepping finite element analysis (TSFEA) is used for all the simulations to achieve a satisfactory precision in analyzing the performance of the proposed VR resolver. Eventually, the results of the analytical model and TSFEM are both verified with an experimental test on the prototype resolver.

In this paper, a finite-time control is proposed based on an extended state observer (ESO) for a pneumatic cylinder servo system. First, an ESO is designed to estimate the friction and varying loads using a super-twisting algorithm. Then, a finite-time controller is designed using a power integrator technology to ensure stability and improve control performances of the pneumatic cylinder servo system. Furthermore, both the effectiveness of the proposed ESO and the finite-time convergence of the closed-loop system are accordingly proven. Finally, experimental results demonstrate that both the control precision and the response rapidity are improved by applying the developed techniques.

Fast tool servo systems with high precision and high speed pose significant challenges to servo control at the nano-scale. The saturation of the control actions, time delays and system uncertainties further complicate the control challenges. To address these problems, we propose a Smith predictor based robust anti-windup scheme in this article, such that high performance servo with nano-accuracy can be achieved in the case of saturations, time delays and model uncertainties. According to the input/output based equivalent representation, the saturation nonlinearity is transformed to the dead zone nonlinearity fulfilling a sector condition. Based on the Popov criterion, the stability conditions for the anti-windup compensator are derived, which are further formulated as an H∞ optimization problem with robustness against model uncertainties. The effectiveness of the proposed control architecture is verified through real-time experiments, where excellent servo performance, saturation compensation and robustness are demonstrated, outperforming existing results.

Based on the receding horizon principle, cost function of nonlinear model predictive control (NMPC) becomes an accumulating type to extend prediction horizon. A nonlinear model predictive speed control (NMPSC) with prediction horizon self-tuning method is proposed in this paper, and applied into a permanent magnet synchronous motor (PMSM) rotor position control system with inner-loop of speed. The prediction horizon is improved as a positive integral discrete-time variable which needs to be adjusted according to operating states in each sampling period. Control performances such as rotor position and speed integral of time-weighted absolute value of errors (ITAEs), delay time and calculation burden are compared with the conventional control strategy, and advantages including ITAEs, delay time, weighting factor sensitivities and servo stiffness are obtained. The effectiveness and correctness are verified by simulation and experimental results.

Writing is one of the most important modes of communication that is an essential element in our day to day life, but for some people it is an impossible task due to their disabilities. Drawing an image nowadays is done using various technologies. Computer Numerical Control (CNC) writing machine sketches picture controlled by a computer system. In this work a low-cost CNC based writing machine is designed and fabricated to ease the difficulties. To design this model three axis controlling unit is needed to control X, Y and Z axis position. X and Y axis can be controlled by two stepper motor and Z axis can be controlled by servo motor. The Dual axis writer helps in performing the writing task with the help of a 2-axis setup using lead screws and stepper motors. The stepper motor aids in accurate writing and designing of required shapes and letters. The objective is to design and fabricate a simplistic model of CNC writing machine and to reduce the cost of the machine.

In this paper, we consider the problem of accurate force control using actuated winches, intended for use in real-time hybrid hydrodynamic model testing. The paper is also relevant to other cable-driven parallel robot applications that use force control in an inner control loop. For this problem, conventional strategies typically use actuated winches with torque-controlled servomotors directly connected to the cabled drum. In contrast, we propose using actuated winches with position-controlled servomotors that connect to the cabled drum via a clockspring. The servomotors are position controlled at drive-level and are rapid, accurate, robust, and simple to install. We show how this, combined with an accurate estimate of the clockspring deflection and stiffness, can yield fast and precise force tracking on moving objects. This includes proposing associated feedforward force-controllers that compensates for damping, angle-dependent force variations, delays, and non-constant clockspring characteristics. Extensive experimental testing on a 1 degree of freedom actuated mass-spring system supports the work. This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/

Servo systems driven by a permanent magnet linear synchronous motor (PMLSM) are often affected by uncertain disturbances, such as magnetic resistance, friction, and external disturbances, which increase tracking errors and reduce motion accuracy. Traditional control methods may have difficulty to achieve satisfactory control performance in terms of tracking accuracy and disturbance rejection. In this paper, we propose an internal model control PID method based on a model linear extended state observer, which is termed as IMC-PID-MLESO method. With this method, the nominal model parameters of the PMLSM servo system are obtained via system identification. The model linear extended state observer (MLESO), with known parameter information, is designed to improve the estimation accuracy for the system states and total unknown uncertainties. As the uncertainties are compensated in the feedback control law, the PMLSM servo system model is transformed into a known nominal model. Based on the nominal model, the IMC-PID feedback controller is designed to ensure satisfactory performance on disturbance rejection and tracking error reduction. Simulation and experimental results show that the IMC-PID-MLESO method can effectively improve the position tracking accuracy of the PMLSM servo system and rapidly suppress the system disturbance.

Aiming at object grasping of indoor mobile robots, this paper develops an object localization system based on the fusion of a monocular camera and a two-axis-controlled laser ranging sensor. The system can locate the specified object in space without obtaining the background depth information of the object, which reduces the consumption of computational resources and has a low cost. According to the coordinate mapping of the object in the image, the measurement point of the laser ranging sensor is controlled to coincide with the target point by two servo motors in perpendicular axes. Thus, the spatial location of the target point can be determined from the rotation angles of the cradle head motors and the laser-measured distance together. To accurately control the rotation angles, a compound strategy combining feedback and feedforward is proposed. On the one hand, the feedback of the laser measurement point is introduced in the image coordinate to realize the close-loop control of the measurement point. On the other hand, a feedforward compensator based on disturbance observation is designed to reduce the influence of robot motion. An experimental setup is developed and substantial experiments are implemented to evaluate the performance of the proposed system. The results show that object localization can be effectively achieved with good accuracy and dynamic response.

This paper focuses on the high performance pointing control of tank servo systems with parametric uncertainties and uncertain nonlinearities including nonlinear friction, backlash and structural flexibility. A comprehensive dynamic nonlinear mathematical model of the two-DOF tank servo system is established. Specifically, to accurately describe the nonlinear friction characteristics in actual systems, a continuous friction model is employed. Moreover, a hybrid nonlinear model combining structural flexibility and transmission backlash is constructed to characterize the nonlinear characteristics of the backlash and flexible coupling between the input and output shafts of the drive end for the tank servo system. By using the backstepping method, a nonlinear adaptive robust controller is presented. In the controller, the adaptive law is compounded to dispose of parametric uncertainties and a well-designed continuous nonlinear robust control law is developed for the purpose of coping with unmodeled disturbances. The closed-loop system stability analysis indicates that the presented controller achieves an asymptotic tracking performance with parametric uncertainties and ensures the robustness against unmodeled disturbances theoretically. The effectiveness of the proposed control strategy is verified by a large number of comparative simulation results.

In the context of failure control of servo system driven by twin motors, there are still no available results to compensate unknown actuator failures which seem inevitable in practice by adaptive backstepping technique. Therefore, to rise the reliability of the system, we aim at addressing such a problem by proposing an adaptive robust actuator failure compensation control scheme based on backstepping technique for servo system driven by twin motors. Unlike the traditional backstepping, the estimation of unknown coefficient of intermediate state variable is introduced in coordinate changes. In addition, matching and non-matching uncertainties have been fully considered in the controller design. Simulation results show that the designed controller can ensure the boundedness of all the signals no matter actuator failures occur or not.

The resonant frequency drift caused by the change in mechanical parameters will cause the servo mechanism of CNC machine tools, robots and other equipment to produce mechanical resonance again. To address this problem, we propose a novel identification method of mechanical resonance based on the Fibonacci principle and a novel design method of notch filters based on optimization theory. First, by using a multifrequency sinusoidal signal, we design a fast search algorithm to search for the drift resonance frequency online; then, we optimize the notch filter to achieve fast and real-time resonance suppression by optimization theory. Compared with commonly employed passive resonance suppression methods, the proposed method can rapidly identify the parameters, more accurately suppress the resonance, minimize the phase angle loss and maintain the stability of the system. Finally, we apply the method to a 2-mass system experimental platform. The experimental results show that the proposed method is superior to the conventional passive resonant suppression method under the resonant frequency drift and other states and has strong robust performance.

Triphibious robots can move in more complex environment compared with common mobile robots, which makes the triphibious robots have a wider movement space and better environmental adaptability. This paper proposes an innovative design solution of a triphibious robot with the tilting-rotor structure (TR-TRS), which can change its motion mode to perform smoothly transition between different media, such as land, water, and air. First, the mechanical structure of the triphibious robot is described with design diagrams. Two tilting-rotors are mounted on the left and right side of a quadrotor-like aerial platform, in which four legs with passive wheel are integrated to make the triphibious robot move on land. Tilting-rotor structure is used to change the orientation of the rotors on both sides of the robot’s fuselage, thus, through adjusting the orientation of these two rotors they can drive the triphibious robot to move on land and underwater. Next, according to the mechanical design, the motion modes in different environmental media are given, and the transition methods between different motion modes are explained in detail. Finally, the influence of tilting-rotor structure on the performance of the designed triphibious robot is analyzed and discussed by the results of virtual simulation. The superior performance of tilting-rotor structure in triphibious robots is demonstrated through the comparison of existing robots.

This article introduces a new dual-drive vertical lift servo system with a slipway that can be used to help people or other intelligent equipment complete high-altitude work better on the exterior wall of the high-rise buildings. In order to improve the system motion performance, enhance the robustness against the variation of system parameters and external disturbances, and minimize position error, a control scheme that integrates proportional–integral–derivative (PID) control and fast terminal sliding-mode control (FTSMC) is applied. The combination of the characteristics of both the PID and FTSMC ensures that the vertical lift servo system achieves motion stability, rapid convergence with small steady-state errors, and strong robustness against variation parameters and external disturbances. Potential rotational dynamics around the center of mass and synchronous error that mainly results from varying loads are reduced through the proposed control torque allocation scheme. The performance of the control scheme is investigated through extensive simulations. Moreover, a series of experimental studies demonstrate the effectiveness of the proposed synchronous position control method for the vertical lift system actuated by the two parallel servo drive systems.

Aiming at the challenges of networked visual servo control systems, which rarely consider network communication duration and image processing computational cost simultaneously, we here propose a novel platform for networked inverted pendulum visual servo control using ${H_{\infty } }$ analysis. Unlike most of the existing methods that usually ignore computational costs involved in measuring, actuating, and controlling, we design a novel event-triggered sampling mechanism that applies a new closed-loop strategy to dealing with networked inverted pendulum visual servo systems of multiple time-varying delays and computational errors. Using the Lyapunov stability theory, we prove that the proposed system can achieve stability whilst compromising image-induced computational and network-induced delays and system performance. In the meantime, we use ${H_{\infty }}$ disturbance attenuation level $\gamma $ for evaluating the computational errors, whereas the corresponding ${H_{\infty }}$ controller is implemented. Finally, simulation analysis and experimental results demonstrate the proposed system performance in reducing computational errors whilst maintaining system efficiency and robustness.

To decrease the injury caused by an accidental collision between the hydraulic manipulator and human, a hydraulic rotating angle self-servo compliant robot driver joint is designed. Based on this joint, a variable stiffness passive servo-hydraulic rotary joint is improved. The passive follow-up characteristics of the improved servo-hydraulic rotary joint enable it to enter the low stiffness mode by itself when it encounters collisions beyond the force limit. Combining this characteristic, the research method of the hydraulic mechanical arm flexible configuration is proposed. Firstly, the joint motion mode is defined by the Euler angle, and a variety of configurations conforming to the motion characteristics of the manipulator are determined. Then, the virtual prototype and collision environment are built, and the dynamic characteristics of the end effector of the arm under high and low stiffness are measured. The results show that the flexible configurations with passive follow-up characteristics can significantly suppress the collision force. Finally, the visual method is employed to solve, draw, and compare the workspace of the selected compliant configuration, to obtain the optimal compliant configuration with both flexibility and motion, which provides theoretical guidance for the subsequent design of the compliant manipulator.

In the low speed servo system of single gimbal magnetically suspended control moment gyro (SGMSCMG), the accuracy of rotor position is an important factor which influences the speed accuracy. Linear hall sensors with small volume and high precision are usually adopted to the compact equipment and suitable for SGMSCMG. However, the signals detected by hall sensors contain lots of harmonics and noise which influence the accuracy significantly. For this reason, a novel precise position detection method based on 2-step cascaded Kalman filter with phase compensation scheme is proposed to extract the precise position information from `dirty' signals. The proposed method is advantageous since it is very simple and practical, and the phase compensation scheme can primely compensate the phase delay caused by cascaded Kalman filter. Finally, the experiments are carried out in a 50 Nm SGMSCMG, and the results show that the method can effectively estimate the angular position of the ultra-low speed servo motor, and the position accuracy can be improved by 85.7%.

In this study, it is aimed to determine and reveal a viable two-axis solar monitoring system that produces higher voltage output than a fixed panel. After intensive research, a small-scale solar panel, servo motors, arduino processor as controller, and a two-axis solar tracker using a transmitter wirelessly transmitting voltage feedback were carried out. In addition, a 'Smart House' model that makes our current lives safer and more practical has been investigated. Remote control of the smart home system has been analyzed. For remote control of the smart home model, the IoT (Internet of Things) structure uses the MQTT Protocol, NodeMCU (ESP8266) Control Card and sensors of different features to build this structure. Signals from sensors are directed to MQTT Broker with the help of the NodeMCU (ESP8266) Control Card. Phone control is provided through the mobile app, which is written using QML and C++ languages in the QT Creator IDE.

In this study, a modified complementary sliding mode control (MCSMC) method based on a disturbance force observer with mass identification (DFOB-MI) applicable to the permanent magnet linear synchronous motor is proposed to achieve high-performance servo control fields. MCSMC is an improvement on the complementary sliding mode control (CSMC) method, which incorporates an approach angle into the saturation function. MCSMC allows for asymptotic convergence of the position tracking errors and guarantees the global robustness of the system. In addition, compared to hybrid control strategies combining neural networks with CSMC, the MCSMC method has a simpler structure and faster response. However, in practical applications, the mass variation of the mover has a significant impact on system performance. To achieve better dynamic and static characteristics, a disturbance force observer capable of identifying the mass variation based on model reference adaptive identification theory is proposed. DFOB-MI can identify the mass of the mover and provide information on the disturbance caused by the change of the load. Thus, the compensation current is calculated to reduce the disturbance and realise compensation. The more accurate tracking performance and stronger robustness of the proposed control scheme compared to conventional approaches have been confirmed through comparative experimental studies.

This study aims to design a crane robot that has good performance with good stability, good accuracy in the gripper clamping the object at the point of balance and reach the target location well. The crane controller is installed with US-100 ping sensor and proximity infrared sensor to detect position of object. The robot crane moves on the x , y and z axes or in three dimensions using motors as actuator and it can be adjusted with motor drive. The crane moves on the x and y axes using DC motor and z axis using servo motor. The crane automatically moves when it detects an object. The crane's movement uses the trajectory determination method by maintaining speed. Finally, the average accuracy of the gripper clamping exactly at the midpoint of the object is 93%. The length of the object when it is clamped has an accuracy of 95%. The performance of the crane robot is evaluated to transfer an object to the destination location takes 11 seconds with a track length of 86.055 cm

Several works have addressed the issue of fault tolerance in multirotors in case of a rotor total failure, particularly their ability to keep full independent control of attitude and altitude. It has been proven that to achieve this, a minimum of six rotors is needed. In this article, the performance of several standard and nonstandard hexarotor structures is analyzed, both for a nominal case (without failure) and in the case where one of the actuators is under failure (incapability to exert thrust). The performance is shown in terms of maximum rotational torque and vertical force that the vehicle can exert. The main contribution of this article is the proposal and analysis of converting these vehicles into reconfigurable ones through the addition of a minimum number of servomotors, to deal with failures and to greatly improve the maneuverability under these conditions, in order to identify the reconfigurable structure with the best performance. An experimental demonstration in an outdoor environment is shown for the proposed reconfigurable structure with best performance in case of a full rotor failure.

Dicing of semiconductor chips constitutes an important procedure in the processing of integrated circuits, which poses a high-precision and high-speed stability requirements for dicing saw. In this study, the optimization of motion accuracy and position accuracy of dual-axis dicing saw (DDS) is studied and an overall control scheme of the DDS is designed. A programmable multi-axis controller (PMAC) is selected as the main control module and the servo motor is adopted as the linear axis drive element. The positioning algorithm of servo control system is analyzed. The position deviations are studied under different proportional gains, integral time constants, and speed feedforward gains. The high-precision contact and non-contact positioning method of the machine tool is developed. Positioning error of each linear axis is compensated using positioning error compensation module of PMAC. The dicing test results demonstrate that the improved control system could be used for high-precision and high-speed stability dicing of semiconductor chips.

In this article, a continuous terminal sliding mode control algorithm is proposed for servo motor systems. A novel full-order terminal sliding mode surface is proposed based on the bilimit homogeneous property, such that the sliding motion is finite-time stable independent of the system's initial condition. A new continuous terminal sliding mode control algorithm is proposed to guarantee that the system states reach the sliding surface in finite-time. Not only the robustness is guaranteed by the proposed controller but also the continuity makes the control algorithm more suitable for the servo mechanical systems. Finally, a numerical example is presented to depict the advantages of the proposed control algorithm. An application in the rotary servo system is done to validate the effectiveness of the proposed control strategy.

In this paper, a generalized nonlinear extended state observer is applied to an integral sliding mode (ISM) tracking control method for a pneumatic cylinder servo system with varying loads. The observer is established to estimate the total disturbance and its derivative for the system. An ISM controller is designed to ensure control performances of the system. Both finite-time convergence of the observer and finite-time stabilization of the closed-loop system are realized using Lyapunov’s stability theory. Lastly, experimental results demonstrate that control precision and response rapidity are improved using the proposed method.

Three-dimensionally (3D) maneuverable robotic fish are highly desirable due to their ability to explore and survey the underwater environment. Existing depth control mechanisms are typically focused on using either compressed air or a piston to generate changes in volume. However, this often makes the system bulky and therefore impractical for use in small size underwater robots. In this letter, a small and compact 3D maneuverable robotic fish is developed. Instead of using a compressed air tank, the robot is equipped with an on-board water electrolyzer that generates gases in the required amount, in order to achieve changes in depth. The fabricated robotic fish demonstrates fast diving and rising performance. A servo motor is used to generate asymmetric flapping motion on the caudal fin for two-dimensional (2D) planar motion. A 3D dynamic model is derived for the fabricated robotic fish. This 3D model is then embedded into a relative velocity framework, to develop a guidance and control scheme that enables the robotic fish to maneuver through underwater orifices. These underwater orifices may be either stationary or moving. Simulations are used to demonstrate the efficacy of the developed algorithm.

In this study, an intelligent second-order sliding mode control (SMC) method combining second-order SMC (SOSMC) and recurrent radial basis function neural network (RRBFNN) applicable to the permanent magnet linear synchronous motor (PMLSM) is proposed to achieve high-performance servo control fields. On the basis of a dynamic model of PMLSM and the SMC theory, the chattering problem in SMC is weakened and the tracking accuracy is improved by the design of SOSMC. As for the boundary of the uncertainty factors is difficult to obtain, the optimal performance of SOSMC is hard to achieve, the RRBFNN uncertainty observer is introduced for estimating the value of the uncertainty factors. Owing to the strong learning ability, the network parameters can be trained online. Besides, a robust compensator is developed to suppress the uncertainties such as approximation error, optimal parameter vector and higher Taylor series for further improving the robustness. Moreover, the adaptive learning algorithms are obtained by using the Lyapunov theorem to guarantee the asymptotical stability of the system. The experiments demonstrate that the proposed scheme provides high performance dynamic characteristics and strong robustness to uncertainties.

This paper presents a control strategy for the position and posture control of a planar four-link underactuated manipulator with a passive second link based on a back-propagation neural network (BPNN) model. First, using the differential evolution (DE) optimization algorithm, the target angles of all links are calculated. The third and fourth links are then controlled from their initial angles to zero. Next, the control process is divided into the following two steps: the control objective of the passive link is implemented in the first step, and the control objectives of the active links are implemented in the second step. In the first step, the system is reduced to a planar virtual Pendubot, a BPNN model based on the DE algorithm is trained to obtain the coupling relationship between the links of this Pendubot. This model gives the speed of the first link to move the passive link to approach the target angle. Then, a fuzzy controller is designed to indirectly control the passive link to its target angle. In the second step, the position mode of the servo controller is adopted to control all active links to their target angles. Experimental results verified the effectiveness of the proposed control strategy.