Master-Slave Robot Control for Flexible Joints and Time Delays
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Solution Overview
Problem
Master-slave robot systems with flexible joints face challenges in position tracking accuracy and stability due to vibrations, especially with time-varying delays, which affect the control accuracy and system stability.
Innovation Solution
A full-state control method is developed using backstepping techniques and high-dimensional uniform accurate differentiators to design virtual controllers and establish stability criteria, ensuring precise position tracking and global asymptotic stability by compensating for time delays and vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If flexible joints are used in master-slave robot systems, then the system achieves small volume, high flexibility, and wider working space, but vibration occurs that affects control accuracy and system stability
Solution Approach 1:
The backstepping control method designs virtual controllers in advance (first virtual controller for position tracking, second virtual controller for velocity control) before actual execution. This preliminary design of control laws allows the system to proactively compensate for vibrations and time-varying delays, maintaining stability while utilizing flexible joint advantages
Solution Approach 2:
The control system continuously measures position and velocity information of joints and motors in real-time, and uses this feedback to adjust control torques dynamically. The full-state feedback mechanism ensures that vibration effects are continuously counteracted, maintaining system stability despite the inherent flexibility of the joints
2Manufacturing precision
If full-state feedback control with backstepping technique is implemented, then global tracking performance and system robustness are improved, but controller complexity increases
Solution Approach 1:
The control problem is segmented into two independent virtual controllers: the first virtual controller handles position tracking (X*s3), and the second virtual controller handles velocity control (X*s4). This segmentation allows each controller to be designed and tuned independently, reducing overall controller complexity while achieving global tracking performance
Solution Approach 2:
The control approach transitions from traditional single-loop control to a two-dimensional virtual controller structure in the state space. By introducing virtual controllers in different dimensional layers (position layer and velocity layer), the system achieves comprehensive control performance without excessive complexity in any single control loop
3Measurement precision
If high-dimension uniform accurate differentiators are employed, then precise differentiation of virtual controllers is achieved and system convergence is improved, but computational complexity increases
Solution Approach 1:
The patent replaces traditional mechanical differentiation methods with high-dimension uniform accurate differentiators that use uniform approximation theory. This substitution achieves precise differentiation of virtual controllers without requiring complex mechanical sensors or sophisticated signal processing, reducing computational complexity while maintaining high precision
4Manufacturing precision
If time delays are compensated in the control system, then position tracking accuracy is improved, but control system complexity increases
Solution Approach 1:
The control system incorporates time delay compensation into the virtual controller design in advance. By predicting and compensating for communication delays (Tm(t) and Ts(t)) before they affect tracking accuracy, the system maintains precision without requiring complex real-time correction mechanisms
Solution Approach 2:
The virtual controllers serve as intermediary elements that mediate between the master robot commands and slave robot execution. These intermediaries inherently compensate for time delays by designing control laws that account for delay effects, simplifying the overall control system architecture while improving tracking accuracy
Data Source
AI summary
A full-state control method for a master-slave robot system with flexible joints and time-varying delays is provided. In a teleoperation system formed by connecting a master robot and a slave robot through network, a proportional damping controller based on a position error and velocities, and a full-state feedback controller based on backstepping are designed for the master robot and the slave robot, respectively. High-dimension uniform accurate differentiators are designed to realize an exact difference to the virtual controllers. Delay-dependent stability criteria are established by constructing Lyapunov functions. Therefore, the criteria for selecting controller parameters are presented such that the global stability of the master-slave robot system with flexible joints and time-varying delays is realized. For the master-slave robot system with flexible joints, the global precise position tracking performance is realized by adopting a full-state feedback controller based on the backstepping method and the high-dimensional uniform accurate differentiators. Moreover, the global asymptotic convergence of the system is guaranteed and the robustness of the system is improved.