The Development of the Linear Actuator with the Series Elastic System for Robot Linkage Mechanisms

Abstract

This paper discusses the development of electric linear actuators to be used in the link structure of robots. Linkage is used in the parallel mechanism of robots, which can solve the disadvantage of serial mechanisms that cannot share the load with other actuators and have low accuracy. In order for linear actuators to be used in robots (especially walking humanoids), high speed is required, unlike conventional linear actuators that focused on high forces. In addition, the linear actuator should be lightweight to reduce the moment of inertia of the robot. This will reduce the required torque of the motor and reduce the power consumption of the robot. Additionally, the linear actuator should measure the external force so that the robot can perform force control. The Series Elastic Actuator(SEA) is one of the actuators capable of measuring external forces by measuring the amount of change in an elastic object. SEA also prevents high forces and high frequencies from being transmitted into the system through springs. However, this has the disadvantage that the force bandwidth is limited when determining the spring constant. In order to adopt only the advantages of SEA, the developed linear actuator solved this disadvantage by measuring an external force with a current of a motor through a low gear ratio. Therefore, at the end of the developed linear actuator is the Series Elastic System, which serves as a physical filtering function. Finally, experiments will verify the functions of this linear actuator and prove that it is optimized for the linkage mechanism of the robot.