Composite nonlinear feedback–based adaptive integral sliding mode control for a servo position control system subject to external disturbance

This paper presents a composite nonlinear feedback–based adaptive integral sliding mode controller with a reaching law (CNF-AISMRL) for fast and accurate control of a servo position control system subject to external disturbance. The proposed controller exploits the advantages of composite nonlinear feedback (CNF) and sliding mode control (SMC) schemes to improve the transient performance and increase the robustness of the closed-loop system. An integral sliding mode combined with a quick reaching law is designed to eliminate the effect of disturbances, which mitigates chattering and achieves finite-time convergence of the sliding mode. An adaptation tuning approach is utilized to deal with unknown but bounded system uncertainties and disturbances. When considering the model uncertainties and disturbances, the stability of the closed-loop system is verified based on the Lyapunov theorem. Numerical simulations are investigated to the effectiveness of the proposed scheme. The transient performance of load disk position to step signal with disturbances using CNF, composite nonlinear feedback based integral sliding mode control (CNF-ISM), and the proposed CNF-AISMRL schemes is given. The simulation results indicate that, without acquiring the knowledge of bounds on system disturbances, the proposed control scheme has superior performance in the presence of time-varying disturbances.

Medical Grabbing Servo System with Friction Compensation Based on the Differential Evolution Algorithm

This paper introduces a pneumatic finger cylinder servo control system for medical grabbing. First, according to the physical structure of the proportional directional valve and the pneumatic cylinder, the state equation of the gas in the servo system was obtained. The Stribeck friction compensation model of a pneumatic finger cylinder controlled by a proportional valve was established and the experimental platform built. To allow the system output to better track the change in the input signal, the flow-gain compensation method was adopted. On this basis, a friction compensation control strategy based on a differential evolution algorithm was proposed and applied to the position control system of a pneumatic finger cylinder. Finally, the strategy was compared with the traditional proportional derivative (PD) strategy and that with friction compensation. The experimental results showed that the position accuracy of the finger cylinder position control system can be improved by using the friction compensation strategy based on the differential evolution algorithm to optimize the PD parameters.

Fuzzy Control of a Servomechanism: Practical Approach using Mamdani and Takagi- Sugeno Controllers

The main objective of this work is to propose two fuzzy controllers: one based on the Mamdani inference method and another controller based on the Takagi- Sugeno inference method, both will be designed for application in a position control system of a servomechanism. Some comparations between the methods mentioned above will be made with regard to the performance of the system in order to identify the advantages of the Takagi- Sugeno method in relation to the Mamdani method in the presence of disturbances and nonlinearities of the system. Some results of simulation and practical application are presented and results obtained showed that controllers based on Takagi- Sugeno method is more efficient than controllers based on Mamdani method for this specific application.

Research on Position Recognition and Control Method of Single-leg Joint of Hydraulic Quadruped Robot

: In order to obtain the precise mathematical model of the position control system of the hydraulic quadruped robot, and to meet the requirements of the system parameters in different stages of motion, this paper studies the position control system of the single-leg joint of the hydraulic quadruped robot: First of all, this paper uses the closed-loop indirect identification method to identify the position of the leg joints of the hydraulic quadruped robot to obtain the mathematical model of the system; And then, the speed PID control algorithm and speed planning algorithm are designed, so that the system can quickly respond to the changes of system input according to the requirements of different speeds; Finally, the joint position control system of the hydraulic quadruped robot is simulated and verified by experiments. Background: The mathematical model of the positioning system of the hydraulic quadruped robot is clear, but the parameters in the model have the characteristics of uncertainty and time-variation. In the joint position control system of a hydraulic quadruped robot, different motion stages have different requirements for system parameters. Objective: The purpose of this study is to obtain the precise mathematical model of the position control system of the hydraulic quadruped robot and to meet the requirements of the system parameters in different stages of motion. Method: This research takes the hydraulic quadruped robot single-leg system as the research object and uses the closed-loop indirect identification method to identify the position of the leg joints of the hydraulic quadruped robot to obtain the mathematical model of the system. Then, the speed PID control method is designed and compared with the ordinary PID control by taking the positioning control accuracy of the robot before touching the ground as a standard to carry out the controlled trial. Results: In this research, the identification method and control algorithm are designed, and finally, the simulation and experimental research are carried out. The results of the simulation and experiment verify the correctness of the identification method and the effectiveness of the control algorithm. Conclusion: First of all, this paper uses the closed-loop indirect identification method to identify the position of the leg joints of the hydraulic quadruped robot to obtain the mathematical model of the system. Then, the speed PID control algorithm and speed planning algorithm are designed so that the system can quickly respond to the changes of system input according to the requirements of different speeds.

Simulation of a Walking Robot-Exoskeleton Movement on a Movable Base

The paper studies the problem of movement of a two-legged walking machine on a movable base. This task is relevant for design rehabilitation and mechanotherapy complexes for people with impaired functions of the musculoskeletal system. Presents a mathematical model that allows obtaining the kinematic and dynamic parameters of the movement of the executive units of the device under study. The paper presents a method for planning the trajectory of exoskeleton links, its algorithmic and software implementation. The paper proposes the structure of the automatic link position control system, which ensures the movement of the executive links along a given trajectory. A mathematical apparatus is proposed for studying the dynamics of the controlled movement of the links of the human-machine system of the exoskeleton. The article presents the results of numerical experiments on the movement of the low-limb exoskeleton leg in the one step mode and analyzes them.