Combining full and semi closed loop synchronous control for dual mechanically coupled ball screw system

The paper presents a synchronous control scheme for a mechanically coupled dual ball screw system applied to wave makers driven by multiple servomotor/ball screw units or machine tools such as those of the gantry type. The hardware system is first established and modelled using a system identification approach. The controller is then designed with pseudo derivative feedback feedforward (PDFF) control. Full and semi-closed-loop controls are analysed and compared in terms of dynamic stiffness, responses and steady-state errors. A hybrid control scheme is then proposed for the investigated system with only one linear scale (i.e., one drive unit is full- and the other semi-closed-loop control). Experiments are conducted to verify the performance by comparing with three conventional synchronous control schemes. The results show that the proposed approach has a much smaller pull-and-drag effect. Also, the positioning accuracy of the system, as well as the synchronous error between the two units is satisfactory.