A Novel Mechatronic Kit of Variable Stiffness Manipulators – Design and Implementation

In the developing fields of wearable devices, rehabilitation, and humanoid robotics, variable stiffness actuators (VSAs) are attracting increasing attention. VSA can minimize forces that are exerted by shocks, and can be safely interacted with by their users. They can store and release energy as passive elastic elements. The main goal of this work is to design a variable stiffness mechanism with a lightweight articulated robot arm. The proposed variable stiffness mechanism is based on lever kinematics. An RC servo motor is used to manipulate the leverage and to adjust the stiffness of the mechanism to control the position of a robot arm. Two spring elements absorb the output force from the lever. Such a design can reduce the number of sensing elements that are used in the robotic system and the damage force that is caused by unpredictable external forces. The designed articulated robotic arm uses a worm gear with a 1:40 high gear ratio to increase the payload capacity and reduce the weight of the robot arm. The worm gear has a self-locking function, which reduces the sliding step of the stepping motor. The advantages of the design in this study are the retention of the strength and loading capacity of the robot arm. The software package LabVIEW is used to build the control and measurement environment in which several control syntheses are tested. Numerous experimental results confirm that the design is reliable and has a low cost of implementation in a shock test. The novel mechatronic kit is ideally suitable for use in advanced mechatronic courses for university students. The discussion of the broad issues deliberated in this investigation will be applied to various systems that require variable stiffness manipulators.