High Precision Nonlinear Motion Control of a Hydraulic Orbital Motor-Driven Linear Rack

In this paper, a high precision motion control strategy of a hydraulic orbital motor-driven linear rack is proposed. The reference system is a forest walking machine, which is designed for moving on wet soils. The high-order nonlinear dynamics and uncertain parameters of the cabin movement that is driven by an electro-hydraulic motor system are the control difficulties. The control accuracy is limited by nonlinear friction, unknown disturbance, dead-band of the proportional valve, etc. To deal with these control difficulties, an adaptive robust backstepping controller is designed based on the nonlinear model of a hydraulic motor driving system. The controller consists of two steps: a position tracking step and a motor torque tracking step. In each step, the uncertain parameters are adapted in real-time to achieve effective model compensation and high tracking accuracy. Simulations with comparative control strategies demonstrate that the proposed controller can achieve high control response and robust tracking accuracy in the presence of nonlinear dynamics and uncertain parameters of the orbital motor driving system.