Modeling and control of a feed drive with multiple mechanically coupled ball screws

This paper presents the modeling and control of a single-axis feed drive that is jointly driven by three ball screw/motor units. These ball screws are bridged by a mechanical coupling, via which a joint thrust can be produced from the three drive units for high-power output (e.g., injection molding machines). Synchronous positioning of these drive units can also be applied to the handling of large workpieces. For such a coupled system, a mathematical model is first derived and constructed using a system identification technique developed in this paper. A control scheme based on the master-slave control is then designed to improve the system performance with the mechanical coupling. To ensure synchronization of the three drive units, a synchronous compensator is also designed using the genetic algorithm. Finally, the performance of the entire control system is experimentally verified.