Sliding mode control of a hydraulic servo system with large frictional torque

Abstract

Precision tracking control for electro-hydraulic servo systems is a critical but difficult issue to be addressed, especially in the situation of large friction torques and low velocities. To address this problem, a novel control scheme is proposed in this paper based on a sliding-mode variable structure controller and a friction observer. The sliding-mode variable structure control law and the sliding-mode friction observer are detailed. The bristle dynamic friction model is adopted to estimate the friction torques and reduce the effects caused by the nonlinear frictions. The proposed control scheme is verified and validated through experimental results. The results show that good position tracking performance with high precision is attained in the presence of dynamic friction even with large friction torques and very low velocities.

A continuous extension of the LuGre friction model with application to the control of a pneumatic servo positioner

“…This fact can be appreciated by means of an example that illustrates the essence of many control algorithms encountered in the specialized literature [4], [8], [14], [18], [19], [20], [21], [24]. It regards the application of a feedback linearization controller to a mechanical system of one degree of freedom driven by an actuator whose internal dynamics cannot be neglected, i. e., the control input u affects the time derivative of the force U instead of the force itself.…”

“…Thus, in many cases, such analyses seem to be incomplete. In [18], for instance, even though the need for an analytic description of the time derivative of the friction force is acknowledged, the methods for dealing with its discontinuity are omitted, whereas in [5] and [19], the matter is not discussed at all. In many other examples [6], [7], [13], [14], [20], [21], the presence of such discontinuitiy causes the stability analyses to be omitted or provided only for restricted cases.…”

Transformer Selection Research Based on Blind Number Theory

“…Overhaul cost. Transformer overhaul technological cost belongs to the annual cycle cost, which is not happen in every year [4]. The frequency of the cost is related to the operating state and running environment of transformer, technological progress speed and operation personnel professional quality, including the overhaul cost and technical renovation costs, whose uncertainty is very strong.…”