Preliminary Investigation of Spring-Based Gravity Compensation for an Upper Limb Assistive Robot

Upper limb assistive robots have been widely developed due to their ability to aid user movement and reduce caregiver workload. In our previous work, we introduced a wearable end-effector-type upper limb assistive robot, WELiBot. To enhance the robot's portability and reduce the required actuation torque, this work investigates gravity compensation for WELiBot's mechanism using springs. Following the 1-DOF gravity compensation principle, springs were designed for lifting and reaching movement respectively. The effectiveness of this compensation effect was then evaluated by comparing the necessary torque at the actuating joints with and without springs. This work offers insight into gravity compensation for parallel mechanisms and contributes to the future development of WELiBot.