scholarly journals Integrated Fixed Time Sliding Mode Control for Motion and Vibration of Space Robot with Fully Flexible Base–Link–Joint

2021 ◽  
Vol 11 (24) ◽  
pp. 11685
Author(s):  
Xiaodong Fu ◽  
Haiping Ai ◽  
Li Chen
Keyword(s):  
Sliding Mode Control ◽  
Sliding Mode ◽  
Fixed Time ◽  
Space Robot ◽  
External Interference ◽  
Flexible Links ◽  
Mode Control ◽  
Flexible Base ◽  
Slow Subsystem ◽  
Flexible Vibrations

The dynamic modeling, motion control and flexible vibration active suppression of space robot under the influence of flexible base, flexible link and flexible joint are explored, and motion and vibration integrated fixed-time sliding mode control of fully flexible system is designed. The flexibility of the base and joints are equivalent to the vibration effect of linear springs and torsion springs. The flexible links are regarded as Euler–Bernoulli simply supported beams, which are analyzed by the hypothetical mode method, and the dynamic model of the fully flexible space robot is established by using the Lagrange equation. Then, the singular perturbation theory is used to decompose the model into slow subsystem including rigid motion and the link flexible vibrations, and fast subsystems including the base and the joint flexible vibrations. A fixed time sliding mode control based on hybrid trajectory is designed for the slow subsystem to ensure that the base and joints track the desired trajectory in a limited time while achieving vibration suppression on the flexible links. For the fast subsystem, linear quadratic optimal control is used to suppress the flexible vibration of the base and joints. The simulation results show that the controller proposed in the paper can make the system state converge within a fixed time, is robust to model uncertainty and external interference, and can effectively suppress the flexible vibration of the base, links, and joints.

Trajectory planning and low-chattering fixed-time nonsingular terminal sliding mode control for a dual-arm free-floating space robot

Robotica ◽  
2021 ◽  
pp. 1-21
Author(s):  
Wen Yan ◽  
Yicheng Liu ◽  
Qijie Lan ◽  
Tao Zhang ◽  
Haiyan Tu
Keyword(s):  
Sliding Mode Control ◽  
Trajectory Planning ◽  
Sliding Mode ◽  
Fixed Time ◽  
Planning Method ◽  
Space Robot ◽  
Terminal Sliding Mode Control ◽  
Terminal Sliding Mode ◽  
Mode Control ◽  
Dual Arm

Abstract This paper addresses fixed-time trajectory tracking for a dual-arm free-floating space robot (FFSR) with the large initial errors and bounded uncertainty. A wrist-based trajectory planning method is improved by fixed-time stability to fast eliminate the error caused by singularity. Then, a novel low-chattering and global-nonsingular fixed-time terminal sliding mode control strategy is studied by state approaching angle and switching sliding mode; the practical fixed-reachable Lyapunov stability analysis is presented for a mechanical control system. In the end, the proposed trajectory planning method and controller are combined to improve the tracking accuracy of end-effector to the nanoscale. Simulation results validate the effectiveness of the proposed methodologies.

Robust Fixed-Time Integral Sliding Mode Control of a Nonlinear Hydraulic Turbine Regulating System

2020 ◽  
Vol 15 (3) ◽  
Author(s):  
Sunhua Huang ◽  
Jie Wang
Keyword(s):  
Sliding Mode Control ◽  
Sliding Mode ◽  
Hydraulic Turbine ◽  
Fixed Time ◽  
Convergence Time ◽  
Stable Operation ◽  
Phase System ◽  
Integral Sliding Mode ◽  
Mode Control ◽  
Time Integral

Abstract The hydraulic turbine regulating system (HTRS) plays an important role in the safe and stable operation of hydropower stations. In this paper, a fixed-time integral sliding mode controller (FTISMC) is designed to make the nonlinear HTRS with disturbances stable in a fixed time. The HTRS is a highly complex, strongly coupled, nonlinear nonminimum phase system, which can ensure the frequency and rotor angle of generator stability by adjusting the guide vane opening. In order to decouple the nonlinear HTRS, the input/output feedback linearization is applied to establish the relationship between the control input and the output of the HTRS. Based on sliding mode control (SMC) theory and fixed-time stability theory, FTISMC is proposed to stabilize the HTRS in a fixed time. Compared with the finite time control method (FTCM), the convergence time of nonlinear HTRS under FTISMC is independent of initial conditions and can be exactly estimated. Meanwhile, the integral sliding surface can avoid singularity, thus eliminating the chattering phenomenon. Finally, the numerical simulation is implemented to demonstrate the superior performances of the proposed FTISMC than the existing PID, SMC, and FTMC.

Fixed-time fractional-order sliding mode control for nonlinear power systems

2020 ◽  
Vol 26 (17-18) ◽  
pp. 1425-1434 ◽  
Author(s):  
Sunhua Huang ◽  
Jie Wang
Keyword(s):  
Sliding Mode Control ◽  
Power System ◽  
Fractional Order ◽  
Finite Time ◽  
Control Method ◽  
Sliding Mode ◽  
Fixed Time ◽  
Sliding Mode Controller ◽  
Mode Control ◽  
Time Control

In this study, a fractional-order sliding mode controller is effectively proposed to stabilize a nonlinear power system in a fixed time. State trajectories of a nonlinear power system show nonlinear behaviors on the angle and frequency of the generator, phase angle, and magnitude of the load voltage, which would seriously affect the safe and stable operation of the power grid. Therefore, fractional calculus is applied to design a fractional-order sliding mode controller which can effectively suppress the inherent chattering phenomenon in sliding mode control to make the nonlinear power system converge to the equilibrium point in a fixed time based on the fixed-time stability theory. Compared with the finite-time control method, the convergence time of the proposed fixed-time fractional-order sliding mode controller is not dependent on the initial conditions and can be exactly evaluated, thus overcoming the shortcomings of the finite-time control method. Finally, superior performances of the fractional-order sliding mode controller are effectively verified by comparing with the existing finite-time control methods and integral order sliding mode control through numerical simulations.

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