If the rigidity of a mechanism is stiff enough,the position synchronous error of the two cylinders driving one degree-of-freedom(DOF)of the mechanism may be less than the resolution of position sensors.To handle this synchronization problem this paper proposes a force/position switching scheme,which partitions the two cylinders into a master cylinder and a slave cylinder.The master cylinder is always position tracking controlled by a second-order sliding mode controller and the slave cylinder is integrated with a force tracking controller which is a first order sliding mode controller.When the position tracking error is less than a given value,the slave cylinder switches to be force controlled.Two synchronization control methods are presented based on the switching scheme:the master-master+force/position switching control and the master-slave+force/position switching control.Simulations show that the proposed synchronization control methods can get a better performance compared with two given position-based control methods.
展开▼
