Tracking Control for High-Performance Motion of a Hydraulic Infinite Linear Actuator

The concept of the hydraulic infinite linear actuator consists of two double-acting cylinders with hydraulically detachable pistons driving a common rod. Alternatingly, one cylinder engages and drives the load, whereas the other retracts; the actuator, thus, works in a kind of rope-climbing motion. The actuator has three degrees of freedom, which are temporarily coupled compared with one in a conventional cylinder. Hence, the actuator is a hybrid system with both continuous and discrete states and control inputs. This paper presents a tracking control problem and a solution for high-performance motion, which is interpreted as utilizing the hardware limits in the sense of velocity, accuracy, smoothness, and usability. The concept is demonstrated by simulation for the case of a rest-to-rest motion, but the intended use cases also include arbitrary trajectories.