Fixed-Time Tracking Control for Flexible Joint Manipulator With Prescribed Performance Constraint

Hong-Yu Chen,Jiu-Tai Liu,Xiu-Cheng Dong,Yong Yang

doi:10.1109/access.2021.3095940

Hong-Yu Chen, Jiu-Tai Liu + Show 2 more

Open Access

https://doi.org/10.1109/access.2021.3095940

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Abstract

This paper studies the transient and steady performance constraints on flexible joint manipulator system with exogenous disturbance, and proposes a fixed-time prescribe performance tracking control method based on the singular perturbation model. For the fast subsystem, a subcontroller with superior transient performance is proposed that guarantees the suppression of flexible vibration in fixed-time. The remaining slow subsystem can be linked with rigid methods to achieve output constraints, a type of time-varying error constraint boundary is first constructed, which broadens the initial error constraint boundary of the time-varying tangent barrier Lyapunov function. Then, a slow subcontroller based on a non-singular fast-integration terminal sliding mode is constructed to make any initial tracking error converge in fixed-time. Finally, a nonlinear disturbance observer is used to counteract the exogenous disturbance. The simulation results show that the controller achieves the prescribe performance.

Highlights

The emergence of robots has greatly improved productivity and can replace humans in completing various tasks, has been widely used in various industries such as aerospace, medical equipment, transportation
Based on singular perturbation method, in [4], a saturation function with errorgain matrix is applied in flexible joint manipulator controller with bounded actuator inputs, in addition, the convergence of the fast subsystem is accelerated by a linear filter of the joint elastic torque error
A novel singularity-free fixed-time sliding mode control (SFSMC) for multi-DOFs uncertain robot manipulators was proposed in [20], which inherits the performance of nonsingular terminal sliding mode (NTSM) surfaces and does not require joint acceleration signals

Summary

INTRODUCTION

The emergence of robots has greatly improved productivity and can replace humans in completing various tasks, has been widely used in various industries such as aerospace, medical equipment, transportation. Among the abovementioned so many controllers, no one considers how to quickly suppress the flexibility of the system in the case of large initial elastic torque which caused by the difference between link angle and motor angle In this case, the design of fast subcontroller we designed can still have the specified convergence performance, the settling time is independent of the initial system state and can be set in advance with the design parameters. A novel singularity-free fixed-time sliding mode control (SFSMC) for multi-DOFs uncertain robot manipulators was proposed in [20], which inherits the performance of NTSM surfaces and does not require joint acceleration signals. 2. A new time-varying constraint boundary based on TanBLF is proposed, which cancels the limitation of initial value error while ensuring ideal transient and steady-state performance.

CONVERGENCE REGION OF TAN-BLF

DESIGN OF FIXED-TIME CONTROLLER FOR FAST SUBSYSTEM

DESIGN OF FIXED-TIME COMPOSITE CONTROLLER FOR SLOW SUBSYSTEM

2: Singularity usually occurs in term

SIMULATION STUDIES

CONCLUSION