Safety Operation of n-DOF Serial Hydraulic Manipulator in Constrained Motion with Consideration of Contact-Loss Fault

Abstract

In consideration of accidental contact-loss due to step-change or accidentally moving out of a constrained framework, this paper focuses on solving this problem during working processes of an n-degree-of-freedom hydraulic manipulator (n-DOF manipulator). In order to overcome this phenomenon, a fault detection methodology-based virtual energy tank is employed with a shaping function to prevent the end-effector from damage or unexpected motion. This technique helps to detect when the contact-loss happens by a virtual energy variable; thus, decoupling a force control regulation. Moreover, a new trajectory for smooth motion after contact-loss detection is also discussed to increase system robustness. Additionally, to enhance tracking performance, adaptive laws are designed to compensate for system uncertainties. Comparative simulations are given on the n-DOF hydraulic manipulator to evaluate effectiveness of the impedance-based energy tank methodology under the sudden step-changed environment. Moreover, influences of control gains and setup energy parameters to the system behaviors when contact-loss happens are remarkably discussed as indispensable criteria for further development. The simulated results certified the superior effectiveness and reliability of the suggested methodology over the conventional impedance control for safe operation.

Nonlinear position control of electro-hydraulic servo system based on lyapunov robust integral backstepping controller

“…The utilization of Electrohydraulic Servo Systems (EHSS) is prevalent in numerous industrial applications and advanced automation systems owing to their exceptional attributes, including positioning capabilities, a highpower ratio, fast and effortless response, rigidity, and the ability to generate substantial force [1]. The application of EHSS has been observed in diverse mechanical systems, including hydraulic robot manipulators, hydraulic presses, load simulators, and active suspension systems for vehicles, and has had a substantial impact on modern position control devices due to its effective positioning capability [2][3][4][5][6][7][8][9][10][11]. However, to achieve accurate positioning in the said applications, a dependable electro-hydraulic actuator is deemed necessary.…”

Adaptive Robust Position Control of Electro-Hydraulic Servo Systems with Large Uncertainties and Disturbances

“…Hydraulic servomechanisms have been broadly employed in various industrial appli cations-e.g., hydraulic robot manipulators [1], hydraulic press [2], load simulators [3], vehicle active suspension systems [4], and so on-due to their superiorities such as a high power-to-weight ratio, fast and smooth response, high stiffness, and ability to generate a tremendous force/torque [5]. However, the inherent highly nonlinear characteristics, parameter variations, modeling uncertainties, and external disturbances of the EHSS are still the major obstacles to achieving high-accuracy tracking performance.…”

“…In another approach to cope with disturbances, some DOB designs based on exact differentiators [29] have been applied in hydraulic systems. For example, a linear disturbance observer (LDOB) [30] for hydraulic rotary actuator (HRA) control systems and nonlinear disturbance observers (NDOBs) [1,31] for hydraulic robot manipulators have been successfully employed to actively reject the influence of the grouped disturbances on the tracking performance. It is noted that the above-mentioned DOB designs require the construction of an observer with a careful tuning process of observer gains to achieve highly efficient disturbance compensation.…”