Adaptive Sliding-Mode Control for Multi-Joint Hydraulic Manipulators
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Solution Overview
Problem
Current multi-joint hydraulic manipulators face challenges with poor control accuracy and susceptibility to shocks or crawling due to the lack of effective control strategies, particularly in harsh environments, and there is a scarcity of multi-axis hydraulic servo controllers compatible with these systems, restricting automation and unmanned operation in conditions like underwater or nuclear radiation settings.
Innovation Solution
A servo control method and system based on adaptive sliding mode control, which involves self-adaptive control of characteristic variables like driving force and length change rate of hydraulic cylinders, effectively addressing nonlinear factors such as hysteresis, leak, and friction to achieve precise position control and coordinated multi-axis motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If independent PID servo control strategy is adopted for each joint, then the control system is simple to implement, but control accuracy deteriorates and shock or crawling occurs
Solution Approach 1:
The patent merges the control of multiple joints into a unified coordinated control system rather than independent PID control for each joint. The sliding mode control algorithm coordinates multiple joints simultaneously, eliminating the accuracy deterioration and shock/crawling issues that arise from independent control while maintaining implementation feasibility through a systematic approach.
Solution Approach 2:
The patent employs adaptive sliding mode control with online parameter adjustment capability. The control parameters are dynamically adapted based on system state and disturbance conditions, allowing the system to maintain high accuracy under varying operating conditions while avoiding the rigid limitations of fixed PID parameters.
2Adaptability or versatility
If master-slave teleoperation or kinematics-based motion control is used, then the manipulator can operate in harsh environments, but control accuracy deteriorates and shock or crawling occurs
Solution Approach 1:
The patent replaces traditional master-slave teleoperation or kinematics-based control with a model-based sliding mode control system. By using a dynamic model of the hydraulic manipulator and applying sliding mode control algorithms, the system achieves precise control in harsh environments without the accuracy deterioration and shock/crawling issues of traditional approaches.
Solution Approach 2:
The patent implements adaptive parameter adjustment in the sliding mode control algorithm, where control parameters are modified in real-time based on system state and environmental conditions. This allows the system to maintain high accuracy across varying harsh environment conditions while eliminating the performance degradation associated with fixed-parameter control methods.
3Device complexity
If conventional servo control is used without considering nonlinear factors, then the control system is simple, but control accuracy deteriorates due to hysteresis, leak, zero-drift of servo valve and friction force of hydraulic cylinder
Solution Approach 1:
The patent implements a feedback mechanism through the sliding mode control algorithm that continuously monitors system state and compensates for nonlinear effects. The controller uses feedback from position, velocity, and acceleration measurements to adjust control signals, thereby compensating for hysteresis, leak, zero-drift of servo valve, and friction force of hydraulic cylinder, achieving high accuracy without excessive complexity.
Solution Approach 2:
The patent employs adaptive parameter adjustment where control parameters are modified in real-time based on detected nonlinear effects. The sliding mode control algorithm dynamically adjusts parameters to compensate for hysteresis, leak, zero-drift, and friction, maintaining high accuracy while managing system complexity through intelligent parameter adaptation rather than complex hardware modifications.
Data Source
AI summary
A servo control method for a multi-joint hydraulic manipulator based on adaptive sliding mode is provided. A motion trajectory of an end of the multi-joint hydraulic manipulator in a workspace is generated, and expected angular displacement, angular velocity and angular acceleration of individual joints are calculated. An actual angular displacement and an actual angular velocity of the individual joints under a current position-pose are calculated. Combined with a dynamic model of the manipulator, a driving force of individual joints is calculated. Based on the expected angular displacement, the actual angular displacement and the driving force, a sliding-mode surface is constructed. The adaptive law is updated to perform adaptive sliding-mode control for the manipulator. A system for implementing the servo control method is also provided.