Observer-based Terminal Integral Sliding Mode Control of a Hydraulic Manipulator for Extreme Environment Applications

Increasing the autonomy of the robots used for nuclear decommissioning has been the subject of further research recently. Hydraulic manipulators are valuable assets in the nuclear industry as they are powerful and contain very few electronic components. However, due to the high nonlinearity, designing a precise tracking controller is challenging. In this paper, a novel backstepping terminal integral sliding mode controller supported with an extended state observer (BTISMCESO) is designed to address this issue in the presence of external disturbances and uncertainties. To address the uncertainties in the actuator dynamic and to manage the complexity of the design a virtual control approach relying on the backstepping technique is applied in the proposed method. The lack of pressure sensors in the actuator dynamic is compensated by designing an extended state observer estimating the internal pressure of the piston. The stability of the closed-loop system in the presence of uncertainties is proved analytically using Lyapunov stability theory. An experimentally validated numerical model of the robot is used to evaluate the performance of the closed-loop system despite parametric uncertainties and external disturbances.