Linear Servo Research Articles

Bound‐based control design for permanent magnet linear motor servo system with inequality constraints and uncertainties

AbstractThe permanent magnet linear motor (PMLM) systems are widely applied in various engineering fields. However, the state inequality constraints and uncertainties of parameters and unknown external disturbances need to be further explored. In this article, first, a state transformation method is proposed for converting bounded states to unbounded states. As a result, the output state of system is limited within the expected boundary constraint. Then, a new control strategy is constructed. This strategy can ensure that the controlled system with uncertainties is uniformly bounded and uniformly ultimately bounded. Finally, the effectiveness of the controller and the state transformation method are verified through simulation of PMLM system. The inequality constraints of the output state are satisfied, and the system performance is improved.

PLC Programming for Vision Checking System with Linear Servo Motors

PLC programs provide precise control over machinery and industrial processes. They dictate how equipment operates, ensuring tasks are performed accurately and consistently according to predefined parameters. In this project, I create the PLC program for a Mitsubishi PLC and design the HMI screen template using Mitsubishi HMI software for a vision checking system integrated with linear servo motorsTop of Form. In vision checking system with linear servo motors inspects PCBA and wiring using a vision camera moved by a servo gantry system. Safety measures are implemented. The program includes auto, manual, and homing sequences, along with mode selection, error handling, counter, shift, and tower lamp functions. HMI screens are designed to teach machine operation. In auto mode, servos move to positions set in the HMI recipe screen. Manual mode allows servo jogging and movement between positions via the HMI servo screen. Pressing the homing button moves servos to user-set home positions. Safety measures, including light curtains, door switches, and fixture sensors, halt the machine and sound a buzzer in case of errors. Counter and shift programming displays running shift and component counts. Programs are tailored to input/output device operations. Key Words: PLC Programming, HMI Screen designing.

Long-Travel 3-PRR Parallel Platform Based on Biomimetic Variable-Diameter Helical Flexible Hinges.

Technological advancements across various sectors are driving a growing demand for large-scale three-degree-of-freedom micro-nano positioning platforms, with substantial pressure to reduce footprints while enhancing motion range and accuracy. This study proposes a three-prismatic-revolute-revolute (3-PRR) parallel mechanism based on biomimetic variable-diameter helical flexible hinges. The resulting platform achieves high-precision planar motion along the X- and Y-axes, a centimeter-level translation range, and a rotational range of 35° around the Z-axis by integrating six variable-diameter flexible helical hinges that serve as rotational joints when actuated by three miniature linear servo drives. The drives are directly connected to the moving platform, thereby enhancing the compactness of the system. A kinematic model of the motion platform was established, and the accuracy and effectiveness of the forward and inverse kinematic solutions were validated using finite element analysis. Finally, a prototype of the 3-PRR parallel platform was fabricated, and its kinematic performance was experimentally verified visually for improved endpoint displacement detection. The assessment results revealed a maximum displacement error of 9.5% and confirmed that, judging by its favorable workspace-to-footprint ratio, the final system is significantly more compact than those reported in the literature.

Design and Implementation of a Linear Active Disturbance Rejection Control-Based Position Servo Control System of an Electromotive Valve for Exhaust Gas Recirculation.

An exhaust gas recirculation (EGR) valve is used to quickly and dynamically adjust the amount of recirculated exhaust gas, which is critical for improving engine fuel economy and reducing emissions. To address problems relating to the precise positioning of an electromotive (EM) valve under slowly varying plant dynamics and uncertain disturbances, we propose a servo control system design based on linear active disturbance rejection control (LADRC) for the EGR EM valve driven by a limited angle torque motor (LATM). By analyzing the structure of the LATM and the transmission, the dynamic model of the system is derived. In addition, to solve the problems caused by slowly varying plant dynamics and uncertain disturbances, we combine the effects of uncertain model parameters and external disturbances as the total disturbance, which is estimated in real time by an extended state observer (ESO) and then compensated. In addition, accurate angular information is obtained using a non-contact magnetic angle measurement method, and a high-speed digital communication channel is established to help implement a closed-loop position control system with improved responsiveness and accuracy. Simulation and experimental results show that the proposed servo system design can effectively ensure the precision and real-time performance of the EM valve under slowly changing plant dynamics and uncertain disturbances. The proposed servo system design achieves a full-stroke valve control accuracy of better than 0.05 mm and a full-stroke response time of less than 100 ms. The controlled valve also has good robustness under shock-type external disturbances and excellent airflow control capability. The repeatability of the airflow control is generally within 5%, and the standard deviation is less than 0.2 m3/h.

Ripple force compensation based on ILC–ASMC for linear servo system

The ripple force, which displays intricate dynamic characteristics and is fundamentally nonlinear in linear servo systems, poses challenges in modeling and compensation. To achieve superior suppression of the ripple force, this paper proposes a new scheme called the iterative learning control (ILC)–adaptive sliding-mode control (ASMC), which combines ASMC and ILC. Initially, the servo system model is established, followed by an analysis of the ripple force mechanism and obtaining a simplified model. Then, an adaptive sliding-mode structure with a feed-forward component is proposed to enhance the servo dynamic response based on the design of a sliding-mode surface. In addition, a new ripple force compensator based on the ILC is designed, allowing for iterative learning from the previous period to accurately estimate the ripple force online. It is worth noting that the process is divided into the 0th iteration and the ith ( i ≥ 1) iteration to avoid the selection for initial values. The 0th iteration ensures initial system stability and provides the initial iteration values, while subsequent iterations approximate the real ripple force through iterative learning. Importantly, the controller and the compensator are combined through the same sliding-mode surface, obviously simplifying the system structure. Finally, experimental results validate the effectiveness of the proposed scheme.

Three Sliding Probes Placed on Forelimb Skin for Proprioceptive Feedback Differentially yet Complementarily Contribute to Hand Gesture Detection and Object-Size Discrimination

The purpose was to assess the effectiveness of three sliding tactile probes placed on the forelimb skin to provide proprioceptive feedback for the detection of hand gestures and discrimination of object size. Tactile contactors representing the first three fingers were driven along the proximodistal axis by linear servo motors. Twenty healthy subjects were involved in the gesture detection test, with 10 of them also participating in the object-size discrimination task. Motors were controlled by computer in the first four sessions of the gesture detection experiment, while the fifth session utilized a sensorized glove. Both the volar and dorsal sides of the forearm were examined. In the object-size discrimination experiment, the method was exclusively assessed on the volar surface under four distinct feedback conditions, including all fingers and each finger separately. The psychophysical data were further analyzed using a structural equation model (SEM) to evaluate the specific contributions of each individual contactor. Subjects consistently outperformed the chance level in detecting gestures. Performance improved up to the third session, with better results obtained on the volar side. The performances were similar in the fourth and fifth sessions. The just noticeable difference for achieving a 75% discrimination accuracy was found to be 2.90 mm of movement on the skin. SEM analysis indicated that the contactor for the index finger had the lowest importance in gesture detection, while it played a more significant role in object-size discrimination. However, all fingers were found to be significant predictors of subjects' responses in both experiments, except for the thumb, which was deemed insignificant in object-size discrimination. The study highlights the importance of considering the partial contribution of each degree of freedom in a sensory feedback system, especially concerning the task, when designing such systems.

Cross-Coupled Synchronous Control of Dual Linear Motor Servo System Based on Disturbance-Assignment Observer and Iterative Learning Control

Cross-Coupled Synchronous Control of Dual Linear Motor Servo System Based on Disturbance-Assignment Observer and Iterative Learning Control

Optimization and Experiment of Linear Motor Platform Servo Control Algorithm

Optimization and Experiment of Linear Motor Platform Servo Control Algorithm

Dual magnet solenoid actuator: Practical applications

We demonstrate several practical applications of a novel linear solenoid actuator design previously proposed to create a solenoid micropump which can be used in portable microfluidic systems. The proposed solenoid actuator design is extended to a system that can apply a constant force with a longer stroke and apply a higher force. It also demonstrates effective mini-train operation with easy and simple control, a spring-loaded linear servo system that solves the classic non-linear control problem, and droplet dispensing with accurate and fast control, showing its potential as a compact microfluidic solenoid micropump capable of precisely handling small volumes of liquid. Applications to digital microfluidic and flow-focusing microchannel systems have also been successfully demonstrated. We hope that this study will promote the development of various actuators for microfluidics and contribute to the broader application of microfluidics in more fields.

High precision tracking control for linear servo system based on intelligent second-order complementary sliding mode

High precision tracking control for linear servo system based on intelligent second-order complementary sliding mode

Performance Investigation and Improvement of Linear Vernier Permanent Magnet Motor for Servo Application

With its high thrust density and low force ripple, the linear vernier permanent magnet motor (LVPMM) is regarded as a good competitor for linear servo applications. However, typical LVPMMs have shortcomings, such as phase imbalance, a long distributed-winding end, and low power factor. The goal of this work is to present a thorough analysis-based approach for performance enhancement that addresses all three flaws while enhancing the LVPMMs high thrust density advantage. Thanks to the proper slot/pole-pair combination, Halbach array PM, and a special three-modular structure, the proposed LVPMM improves thrust density by 28%, reduces force ripple to 1.2%, increases power factor by over 40%, and nearly eliminates three-phase imbalance when compared with those of a conventional LVPMM. Manufacturing and testing a 2.2 kW/2200 N prototype has confirmed the viability of the theoretical analysis and improvement process.

Integrated thrust ripple identification and compensation for linear servo system using an MP algorithm

Generally there are two methods for the thrust ripple modeling: one is to identify the eigenvalues and the model parameters of thrust ripple sequentially under rigorous operating conditions; another is to treat thrust ripple as a general and inaccurate disturbance. To get rid of the constraints and further enhance the tracking accuracy of the linear servo system, a novel integrated identification and compensation scheme using an improved matching pursuit algorithm is proposed in this paper. First, the dynamics of the linear motor is formulated, and the cause of thrust ripple is analyzed. Then, a time–frequency atomic library of thrust ripple is constructed with the consideration of the frequency characteristics of position command, and meanwhile, the two optimal atoms are obtained successively by maximizing the inner product for the thrust ripple reconstruction. Based on the above, the eigenvalues and model parameters of thrust ripple can be simultaneously identified in an online manner. Finally, the feedforward compensation component is devised by the identification results to suppress thrust ripple. In order to verify the superiority of the proposed scheme, simulations and experiments are conducted compared with the conventional methods.

Design and Control of a Linear Rotary Electro-Hydraulic Servo Drive Unit

In this paper, a new solution for an electro-hydraulic servo drive is proposed, which consists of two electro-hydraulic servo drives: one with a hydraulic cylinder and one with a hydraulic rotary motor. In the proposed drive, the linear actuator is attached to a horizontal base and the hydraulic motor is mounted on the actuator piston rod. Thus, the output signal of the drive is the lifting and lowering of the element suspended on the rope. The paper describes the structure, kinematics, dynamics, and control of a novel electro-hydraulic servo drive. A servo valve and a proportional valve are used to control the flow of the hydraulic cylinder and the hydraulic motor. Special attention is paid to the construction of two actuators in one drive unit. The controller is based on the PLC controller. The measuring system uses laser displacement sensors and an encoder. The results of laboratory investigations are discussed in the paper. The proposed drive contains all of the characteristics of a mechatronic device. The main contribution of this study is the proposal of the controller architecture and the algorithm to control the speed and position when lifting or lowering loads.

An Experimental and Numerical Evaluation of the Aerodynamic Performance of a UAV Propeller Considering Pitch Motion

Considering the vibration generated by a propeller-driven UAV or encountering gust, the propeller will perform a very complex follower motion. A pitch and rotating coupled motion is proposed in the present work that can take more complex unsteady performance of follower force than a regular fixed-point rotating motion. In order to evaluate the unsteady follower force and conduct parametric study, an extensive ground test bench was designed for this purpose where the whole test system was driven by a linear servo actuator and the follower force was measured by a 6-component balance. For CFD simulation, coupled motion in particular needs detailed unsteady aerodynamic model; therefore, a high-fidelity CFD-based study integrated with the overset mesh method was complemented to solve the unsteady fluid of varying conditions. The results suggest that a significant influence on unsteady follower force is observed, and the mean value of in-plane force does not equal to zero during the coupled motion process. Compared with the regular fixed-point rotation of propeller, the fluctuation frequency of follower force in present work couples the rotation and pitch motion frequencies. In addition, the oscillation amplitude of out-plane force and torque is positively related with the pitch frequency, pitch amplitude, and relative length from leading edge of wing to the rotation center. For example, the oscillation amplitude of 1-blade’s out-plane force and torque increases by 57.122% and 66.542% for the 5 Hz-5 deg case compared with the 5 Hz-3 deg case, respectively. However, the torque is not sensitive to frequency of pitch motion. The generally excellent agreement evident between the ground test and numerical simulation results is important as guidance for our future investigation on “dynamic” aerodynamic performance of a propeller-driven UAV.

Deep Reinforcement Learning for the Visual Servoing Control of UAVs with FOV Constraint

Visual servoing is a control method that utilizes image feedback to control robot motion, and it has been widely applied in unmanned aerial vehicle (UAV) motion control. However, due to field-of-view (FOV) constraints, visual servoing still faces challenges, such as easy target loss and low control efficiency. To address these issues, visual servoing control for UAVs based on the deep reinforcement learning (DRL) method is proposed, which dynamically adjusts the servo gain in real time to avoid target loss and improve control efficiency. Firstly, a Markov model of visual servoing control for a UAV under field-of-view constraints is established, which consists ofquintuplet and considers the improvement of the control efficiency. Secondly, an improved deep Q-network (DQN) algorithm with a target network and experience replay is designed to solve the Markov model. In addition, two independent agents are designed to adjust the linear and angular velocity servo gains in order to enhance the control performance, respectively. In the simulation environment, the effectiveness of the proposed method was verified using a monocular camera.

An intelligent fuzzy-particle swarm optimization supervisory-based control of robot manipulator for industrial welding applications

The propensity of manufacturers to produce goods at affordable cost, with more accuracy, and at a faster rate force them to search for novel solutions, such as deploying robots in place of people in a sector that can accommodate their needs. Welding is one of the most crucial processes in the automotive industry. This process is time-consuming, subject to error, and demands skilled professionals. The robotic application can improve this area of production and quality. Other industries, such as painting and material handling, can also profit from the use of robots. This work describes the fuzzy DC linear servo controller, which functions as a robotic arm actuator. Robots have been widely employed in most productive sectors in recent years, including assembly plates, welding, tasks at higher temperatures, etc. Controlling a robot accurately is a difficult undertaking as a robot is very nonlinear with many joints that are often organized and unstructured. To carry out the effective task, an effective PID control based on fuzzy logic has been employed together with the method of Particle Swarm Optimization (PSO) approach for the estimate of the parameter. This offline technique determines the lowest number of optimal robotic arm control parameters. To verify the controller design with computer simulation, a comparative assessment of controllers is given by means of a fuzzy surveillance controller with PSO which improves the parameter gain to provide a rapid climb, a smaller overflow, no steady condition error signal, and effective torque control of the robot arm.

Research on Acceleration Segmented Compensation Strategy for Backlash of CNC Machine Tools

For the problem of backlash in the semi-closed-loop linear feed servo system of CNC machine tools, which seriously affects the accuracy of machine tools, an acceleration segmentation backlash compensation strategy is proposed. In the reverse motion of the servo motor, the servo motor is controlled to compensate for the backlash error during a period of accelerated motion and a period of decelerated motion. Based on the established backlash transmission model, the parameters of the compensated motion process are calculated. In order to ensure accurate and quick compensation of the gap compensation value for the transmission gap, the backpropagation method is used to backpropagate the acceleration calculation based on whether the acceleration process time is an integer multiple of the servo interpolation period. Finally, the feasibility of the method is verified through experiments, and the results show that the method improves the positioning accuracy of machine tools.

Speed Tracking Performance for a Coreless Linear Motor Servo System Based on a Fitted Adaptive Fuzzy Controller

Fuzzy control is widely used in linear motor servo systems. However, simple fuzzy rules reduce the control accuracy of the servo system, while complex fuzzy rules reduce the speed of its decision making. This paper proposes a fitted adaptive fuzzy controller (FAFC) to improve the speed tracking performance of a coreless linear motor servo system. The FAFC took a planned curve as a motion target. The planned curve is compounded by multiple performance curves of fuzzy control under the same given input. These multiple performance curves cover the variation range of motor parameters, which are offline-obtained. The performance of the planned curve is ensured by the multiple offline performance curves. The FAFC only needs simple fuzzy rules to fit the planned curve, and achieves high control accuracy without affecting the decision speed. The experimental results verified the feasibility of an FAFC. This research shows that an FAFC can effectively shorten the online calculation time of complex algorithms and keep the consistency of performance.

Optimization of PI-Cascaded Controller’s Parameters for Linear Servo Mechanism: A Comparative Study of Multiple Algorithms

Optimization of PI-Cascaded Controller’s Parameters for Linear Servo Mechanism: A Comparative Study of Multiple Algorithms

Psychophysical Evaluation of Proprioceptive Feedback Through a Probe Sliding on the Forearm Skin of Healthy Humans.

We have tested the forearm skin of humans as a target organ to deliver proprioceptive feedback via a tactile sensory substitution method. In the proposed method, a contactor probe was actuated by a linear servo motor and moved on the skin in proximo-distal axis depending on the angle of a virtual joint moving on a 180° arc. Twenty healthy subjects were tested to stop the joint at a given target under no-feedback, visual feedback, and tactile (dorsal and volar) feedback conditions. The absolute difference between the target and the response angle was recorded. Tests were repeated 4 times with ~ 1-week intervals. Two joint movement speeds were tested. The subjects performed best with visual feedback, and worst if no feedback was provided. Their performances with tactile feedback were not as good as in the visual feedback condition, but better than in the no-feedback condition. Subjects equally performed with volar and dorsal tactile feedback. The movement speed had no significant effects on tactile feedback. The performance improved with training only in tactile feedback conditions. The proprioceptive information from a motorized prosthesis can be provided through probes moving on the forearm skin, while the efficacy of the feedback may improve with extensive training.