Design and control of a multi-mode drive system

A structure of a drive system is presented which allows operation in a number of modes, which may be combined in various ways to give optimum performance for a given motion. The drive mode is controlled by a number of clutches and brakes and the drive also includes a spring which can be used to store energy under the control of the clutches. In one operating mode this spring is used to repeatedly transfer packets of energy from the input to the load in such a way that a variable speed ratio is achieved. In a second mode the spring is used to store energy extracted from the load at the end of one operation to be used at the beginning of a subsequent motion. Other modes allow precise position control and load braking. The paper describes the operating modes and control strategies and presents results for a prototype device.