Energy efficiency and performance optimized control of a hybrid feed drive

Linear motor drives (LMDs) are well known to provide significant advantages in terms of positioning speed and precision over traditional screw drives (SDs), making them better suited for high-speed, high-precision machine tools. However, their use in such machine tools is limited by their tendency to consume a lot of electrical energy and cause thermal issues that help drive up costs. A hybrid feed drive (HFD) has been proposed as a possible solution to this dilemma. The HFD combines LMD and SD actuation to achieve speeds and accuracies similar to LMDs while consuming much less energy. This paper explores control strategies to further improve the performance of the HFD without unduly sacrificing its efficiency. First, it highlights two performance limitations of the controller proposed for the HFD in prior work, namely, imperfect tracking and suboptimal feedback gains. Then it compares two approaches for achieving perfect tracking with regard to performance and energy efficiency. Finally, it presents an approach for optimizing the feedback gains of the HFD to achieve the best positioning performance. Simulations and experiments are used to demonstrate significant gains in precise positioning using the methods proposed in this paper, while maintaining superb energy efficiency relative to an equivalent LMD.