Design of a Fast Servo Multi-Element Feed Drive

High precision positioning has become one of the most important features of a precision machine. Such a machine is required to provide versatility, speed and workspace and high precision positioning. Combining coarse (large stroke) and fine (high resolution) drive elements, connected in series, in a multi-element feed drive system provides the capacity of a large workspace with the property of high resolution motion. The performance of the whole system may be improved by adopting the merits of both drive elements to work in a complementary fashion. The multi-element feed drive concept has several applications in manufacturing, robotics and data storage. Fast tool servo in manufacturing is a direct use of the concept and its applications range from the creation of asymmetric surfaces to online chatter suppression. Micro-macro robots are also examples of multi-element feed drive systems that provide advantages when both large work space and accurate end-effector positioning are required. This paper presents an innovative design of a multi-element feed drive system for machine tools. It studies the design methodology and the implementation of the system and investigates several considerations that govern the design process and determine the performance. A multi-element feed drive setup based on a combination of PA and LM was built for experimental testing. Results show that the multi-element feed drive is able to improve the tracking performance as well as the steady state error. It also achieves faster settling time