The design and control of mechanical switched mode drives
This thesis is concerned with the design, control and performance evaluation of a novel design for mechanical drives. This drive operates in a pulsed manner where energy is extracted from the input, stored and then released to the output. A spring acts as the energy store and brakes and clutches control the extraction and release of energy. By controlling the storage and release of this energy the device's output velocity can be controlled independently of the input velocity and since theoretically there is no energy loss the device operates in an analogous fashion to a variable ratio gearbox. Two design variations are presented. A step-up mechanism that is unidirectional and capable of output velocities greater than the input, and a step-up/stepdown device that has bi-directional output velocity capabilities with no theoretical constraint on the value of output velocity. A prototype drive for each design is evaluated and detailed mathematical models are presented and compared to the prototypes. In addition a detailed design methodology is put forward for step-up/stepdowndevices.