Development of X-screw: a load-sensitive actuator incorporating a variable transmission

Abstract

This research deals with the development of a load-sensitive continuously variable transmission designed for use as a linear actuator. This mechanism, named X-screw, has several unique features not found in other transmission systems that make it especially suitable for use as a robotic actuator. X-screw has a transmission ratio that automatically changes in response to the load, making it possible to combine relatively high speed motion under low loads with a large maximum load capacity in a much smaller space and with less complexity, than traditional transmission systems. X-screw also has built-in overload protection since it will stop advancing if the load exceeds a certain value although the motor is able to continue to rotate. Furthermore, X-screw can produce arbitrarily slow linear motion from a high speed input, eliminating the need for bulky gear reductions. Experimental tests conducted with a prototype have confirmed the functionality of this system.