Closed-loop PID Control System Research Articles

Design and implementation of a 2-DOF 5R parallel mechanism with a coaxial-driven layout

In order to expand and improve the reachable workspace of planar parallel manipulators, a 2-DOF 5R parallel mechanism with a coaxial-driven layout is proposed. The configuration analysis and structural design are carried out, and the kinematic model is presented to conduct simulation analysis. The results indicate that the layout with the axes of the two driving devices overlapping has a larger workspace and a more compact structure. Meanwhile, a closed-loop PID control system is established to evaluate the accuracy of the proposed mechanism and analyse the kinematic error under different gain parameters. Simulation results indicate that the kinematic performance of the mechanism has improved. The control system is constructed based on using a motion control card as the primary control component and two servo motors as the drive device. Additionally, gain values are adjusted by the driver to reduce the deviation of the servo motors. Finally, the design of the prototype is deployed, and the experiment proved that the 2-DOF 5R planar parallel mechanism (PPM) with a coaxial-driven layout has the advantages of a large workspace, fast dynamic response, high stiffness, and easy control. The design of the 2-DOF 5R PPM solves the problem of single operation and high repeatability, which is increasingly utilized in the fields of electronics, food, daily chemicals, and pharmaceuticals.

Inertia matching of CNC cycloidal gear form grinding machine servo system

Reasonable ratio between the load inertia and servo motor inertia plays a decisive role for the dynamic performance and stability of the servo system, as well as the machining accuracy of the whole CNC machine. In order to improve the control performance and contour machining accuracy of the servo system of the CNC cycloidal gear form grinding machine, an optimization design method of the inertia matching for the CNC cycloidal gear form grinding machine servo system is proposed. The two-mass servo driving closed-loop PID control system is constructed, the influence of the different inertia ratios on the dynamic performance and contour errors of the servo system are deeply analyzed, and the inertia ratio is optimized to satisfied with the servo system performance requirements. Finally, the feasibility and practicability of the optimization design method of inertia matching are verified through the inertia ratio optimization grinding experiments of the cycloid gear in the CNC gear form grinding machine. This inertia matching optimization design method provides a valuable reference for the further design of CNC machine servo system.

Controlling bending deformation of a shape memory alloy-based soft planar gripper to grip deformable objects

Integrating flexible sensors into a soft finger is a common approach to control the deformation of the finger. However, adding sensors, especially sensors with a degree of stiffness, sacrifices the overall compliance of the finger structure and increases the complexity of fabrication and control. This study provides an alternative approach, without the need for integrated sensors, to control the deformation of a shape memory alloy (SMA)-based soft planar gripper for grasping deformable objects. The gripper consists of one soft finger which is an SMA-based hinge actuator capable of producing hinge-like bending deformation. The soft finger can automatically achieve the desired deformation by introducing a closed-loop PID control system. A camera as a vision sensor, instead of integrated flexible sensors, was used to detect the bending deformation of the soft finger in real-time. With the feedback from the camera, the PID controller was implemented in a microcontroller with designed external circuits, to enable the soft finger to reach any targeted bending angle within its deformation range, according to the size of the manipulated object. As a demonstration, the soft planar grippers with the desired deformation were eventually used to grip deformable objects, including flowers and a panicle. Without the need for material characterization and analytical models, the proposed method can also be extended to other soft planar grippers based on different actuation techniques.

Position and Force Control of a Twisted and Coiled Polymeric Actuator

Twisted and coiled polymer (TCP) actuator has many advantages such as high contraction capability, high work density, low cost materials, and easiness of fabrication, making it promising for applications in biomedical devices, soft robotic, and energy-harvesting equipment. However, convenient and effective control of TCP actuators still remain some challenges. In this paper, we use an accurate strain-temperature and force-temperature model of TCP actuators to design a simple and efficient closed-loop PID control system. The validity of the proposed controllers is investigated through numerical simulations and experiments. The results show good control performance with minimum tracking errors which is less than 3% in our work. Such accuracy is ideal for many engineering fields and robotic designs.

Digital Realization of Retuning Fractional-Order Controllers for an Existing Closed-Loop Control System

In the present paper, the problem of digital implementation of retuning fractional-order (FO) controllers for an unstable plant — a real-life laboratory model of a Magnetic Levitation System (MLS) — is investigated. Retuning control is applied to an existing closed-loop PID control system through the use of a hardware FO controller prototype. An implementation method for the retuning controller is proposed. Three types of hardware-in-the-loop (HIL) experiments are considered. First, the plant is simulated using a suitable dynamic model. Second, the real-life laboratory model of the MLS is controlled. In the third type of experiment, a MATLAB implementation of the retuning controller is evaluated as a benchmark. Three controllers obtained in an earlier work are tested with this setup. Experimental results are compared and discussed.

Control Simulation of Active Magnetic Levitation Closed-loop PID System

To realize “starting breeze, breeze power”, using electromagnetic force to adjust the displacement of the magnetic suspension rotor of the wind turbine. Through the force analysis, the equation of motion of the magnetic suspension rotor is established. Closed loop PID control system is designed to obtain the transfer function of the closed loop system, according to the characteristic equation to determine the range of PID parameters, and then through the MATLAB Simulink simulation gives the specific PID parameters of the stable suspension. In order to lay a theoretical foundation for the stability control of magnetic levitation, a feasible method is provided for finding the PID parameters.

Research on a Long Travel Nanopositioning Air Bearing Stage with the Linear Motors

The objective of this research is to develop a PC-based closed-loop nanopositioning system using the dual-frame two-axis drive single mobile independent framework. The stage body was supported by an air bearing on a granite base to reduce the frictional force. The developed stage was driven by the PC-Based interface of ANCA 5DX CNC controller, for the precision motion control of the linear motors. The laser scales were used as the feedback sensors so that the closed loop control of the developed system was possible. Based on the test results, the designed closed loop nanopositioning system was capable of precision positioning within the travel of 100 mm along X-axis and Y-axis. The Z-direction stage stability of the developed system was 20 nm, the maximum yaw error of the stage moving along X-axis was about 3.77 arc-seconds, and the maximum pitch error of the stage moving along Y-axis was about 1.04 arc-seconds, based on the test results. By utilizing the PC-Based interface of ANCA 5DX CNC controller based closed-loop PID control system, the positioning capability of X-axis and Y-axis was about 20 nm. Performing the circular test with radius of 20 mm, the deviation of circular positioning test was about 223 nm. Based on the tracing speed test results, the standard deviation along X-axis and Y-axis was 5 nm under tracing speed of 0.05 mm/min.

Excitation Liquid-Cooled Retarder Control System Design Based on MC9SXS128

This paper presented a excitation liquid-cooled retarder control system based on a microprocessor MC9SXS128. In order to achieve the constant speed, It used PWM to adjust the output current of excitation liquid-cooled retarder. It analyzed and calculated the inductance value in PWM output circuit and also analyzed the excitation liquid-cooled retarder control systematical mathematical model . It divided the brake stalls based on the current flowing through the field coil. by adding the PID closed-loop control system, the retarder could quickly reach the set speed. It tested the PID control algorithm at the experiments in retarder drum test rig and the results show that the control algorithm has good control performance to meet the application requirements.

Non-linear model-based Control for the Human-inspired Robotic Exoskeleton (HuREx) gait trainer

Abstract A non-linear model-based control system for the Human inspired Robotic Exoskeleton (HuREx) gait trainer was developed. The model used for the controller was derived using a hybrid PMA model and dynamic model of the device. The performance of the control system was compared against a closed-loop PID control system in simulation. The trajectory tracking results show that the model-based control system improved the speed and accuracy of the system as well as being robust against modeling errors and disturbances.

A Specific Methodology of Creep Compensation for Piezoelectric Actuators by Open-Loop Control

Piezoelectric actuators exhibit creep behavior in open-loop operation, which may lead to unaffordable errors in high precision static positioning systems. An inversion-based compensation strategy by open-loop control is presented for reducing creep effect. The approach utilizes a nonlinear viscoelastic model to portray creep phenomenon, which consists of a linear spring, a nonlinear dashpot and a series of nonlinear Voigt elements. It is shown that for the presented creep model the step responses are very similar to the piezoelectric actuators. In order to compensate creep effect, a concept of voltage relaxation in piezoelectric actuators is proposed. And the voltage relaxation model tantamount to the inverse creep model is derived using a PID closed-loop control system. Experimental results prove that, by insertion of voltage relaxation model in open-loop operation, creep effect is attenuated markedly in piezoelectric actuators.

Synchronous Control Technology Research of Hydraulic Lifting System

In conventional “flow control valve and travel switch” control strategy, relative height difference between multiple cylinders only reach accuracy of centimetre grade, which can’t meet synchronous control accuracy requirements of many engineering. In order to improve multiple cylinders synchronous accuracy of the hydraulic lifting system, this paper takes a hydraulic lifting system as basis, which studies PID closed loop control system using electro-hydraulic proportional valve and high-precision displacement accuracy sensor, and the synchronous accuracy of 4 cylinders hydraulic lifting system is improved to millimetre grade.

Coupled Simulation Study on the Working Device of the Excavator Based on VL Motion

On the foundation of analyzing the excavator’s working device structure, this paper built its three-dimensional model in Catia embedded in the VL Motion, created the bodies, defined the joints and corresponding drive interface to produce the multi-body dynamic model. According to the analysis on the hydraulic system of the working device, it built the electro-hydraulic system with the interface of Motion in AMEsim and then performed the coupled simulation between the Motion and AMEsim. Aiming at the working device’s performance defects, such as the worse displacement tracking, the slow respond, it designed the PID closed loop control system to improve the system’s performance. The simulation results show that the working device’s combination performance has been improved greatly, respond speed becomes fast and the ability of displacement tracking is better.

Adaptive Robust Pid Controller Design Based On A Sliding Mode For Uncertain Chaotic Systems

A robust adaptive PID controller design motivated from the sliding mode control is proposed for a class of uncertain chaotic systems in this paper. Three PID control gains, \(K_p, K_i\), and \(K_d\), are adjustable parameters and will be updated online with an adequate adaptation mechanism to minimize a previously designed sliding condition. By introducing a supervisory controller, the stability of the closed-loop PID control system under with the plant uncertainty and external disturbance can be guaranteed. Finally, a well-known Vanderpol oscillator is used as an illustrative to show the efectiveness of the proposed robust a PID controller.

Improvement of the performance of hysteresis compensation in SMA actuators by using inverse Preisach model in closed — loop control system

The aim of this paper is to increase the performance of hysteresis compensation for Shape Memory Alloy (SMA) actuators by using inverse Preisach model in closed — loop control system. This is used to reduce hysteresis effects and improve accuracy for the displacement of SMA actuators. Firstly, hysteresis is identified by numerical Preisach model implementation. The geometrical interpretation from first order transition curves is used for hysteresis modeling. Secondly, the inverse Preisach model is formulated and incorporated in closed-loop PID control system in order to obtain desired current-to-displacement relationship with hysteresis reducing. The experimental results for hysteresis compensation by using this method are also shown in this paper.

Adaptive robust PID controller design based on a sliding mode for uncertain chaotic systems

A robust adaptive PID controller design motivated from the sliding mode control is proposed for a class of uncertain chaotic systems in this paper. Three PID control gains, Kp, Ki, and Kd, are adjustable parameters and will be updated online with an adequate adaptation mechanism to minimize a previously designed sliding condition. By introducing a supervisory controller, the stability of the closed-loop PID control system under with the plant uncertainty and external disturbance can be guaranteed. Finally, a well-known Duffing–Holmes chaotic system is used as an illustrative to show the effectiveness of the proposed robust adaptive PID controller.