Output Feedback Fractional-Order Nonsingular Terminal Sliding Mode Control of Underwater Remotely Operated Vehicles

For the 4-DOF (degrees of freedom) trajectory tracking control problem of underwater remotely operated vehicles (ROVs) in the presence of model uncertainties and external disturbances, a novel output feedback fractional-order nonsingular terminal sliding mode control (FO-NTSMC) technique is introduced in light of the equivalent output injection sliding mode observer (SMO) and TSMC principle and fractional calculus technology. The equivalent output injection SMO is applied to reconstruct the full states in finite time. Meanwhile, the FO-NTSMC algorithm, based on a new proposed fractional-order switching manifold, is designed to stabilize the tracking error to equilibrium points in finite time. The corresponding stability analysis of the closed-loop system is presented using the fractional-order version of the Lyapunov stability theory. Comparative numerical simulation results are presented and analyzed to demonstrate the effectiveness of the proposed method. Finally, it is noteworthy that the proposed output feedback FO-NTSMC technique can be used to control a broad range of nonlinear second-order dynamical systems in finite time

Research on a Nonlinear Robust Adaptive Control Method of the Elbow Joint of a Seven-Function Hydraulic Manipulator Based on Double-Screw-Pair Transmission

A robust adaptive control method with full-state feedback is proposed based on the fact that the elbow joint of a seven-function hydraulic manipulator with double-screw-pair transmission features the following control characteristics: a strongly nonlinear hydraulic system, parameter uncertainties susceptible to temperature and pressure changes of the external environment, and unknown outer disturbances. Combined with the design method of the back-stepping controller, the asymptotic stability of the control system in the presence of disturbances from uncertain systematic parameters and unknown external disturbances was demonstrated using Lyapunov stability theory. Based on the elbow joint of the seven-function master-slave hydraulic manipulator for the 4500 m Deep-Sea Working System as the research subject, a comparative study was conducted using the control method presented in this paper for unknown external disturbances. Simulations and experiments of different unknown outer disturbances showed that (1) the proposed controller could robustly track the desired reference trajectory with satisfactory dynamic performance and steady accuracy and that (2) the modified parameter adaptive laws could also guarantee that the estimated parameters are bounded

Switchmode Hydraulic Power Supply Theory

ABSTRACT Switchmode hydraulic power supply is a new kind of energy-saving pressure converting system, which is originally proposed by the authors. It is mainly applied in multipleactuator hydraulic systems, and installed between hydraulic pump and actuators (one switchmode hydraulic power supply for one actuator). It can provide pressure or flow rate that is adapted to the consumption of each actuator in the system by boosting or bucking the pressure, with low power loss, and conveniently, through high-speed switch valves, just like a hydraulic pressure transformer. There are two basic types of switchmode hydraulic power supply: pressure boost and pressure buck. Their structures and working principles are introduced. The dynamic characteristics of two typical types of switchmode hydraulic power supply, the pressure boost type and the pressure buck type, were analyzed through simulations and experiments. The performances were evaluated, and improvements on the efficiency of switchmode hydraulic power supply were proposed. INTRODUCTION A practical advantage of hydraulic systems is their multipleactuator characteristic, i.e., multiple actuators can be driven simultaneously by a single hydraulic power supply. Currently, there are three kinds of multiple-actuator hydraulic systems in terms of the power supply used, the throttle control systems, the load sensing systems and the secondary regulation systems. To compare the performance of different systems, one can take a three-actuator system as an example. The energy losses of these three kinds of multiple-actuator hydraulic systems are shown i

Nonsingular terminal sliding mode control of underwater remotely operated vehicles

This study investigates the nonsingular terminal sliding mode control (NTSMC) method for the 4-DOF (degrees of freedom) trajectory tracking control problem of underwater remotely operated vehicles (ROVs) in the presence of parametric uncertainties and external disturbances. Two new control algorithms have been developed for ROVs. The first one, combining a nonsingular sliding surface with a fast-TSM-type reaching law, is nonsingular and chattering-free. The second one, introducing adaptive methodology to compensate for the lumped uncertainties, is an improved version of the first algorithm and can be called adaptive NTSMC (ANTSMC). The application of adaptive methodology effectively eases the chattering problem. Meanwhile, it also provides better robustness and higher tracking precision compared with the first algorithm. A corresponding stability analysis is presented using Lyapunov stability theory, and some comparative numerical simulation results are presented to show the effectiveness of the proposed approaches.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author