Abstract
Most passive gravity balancers require manual adjustment or employ actuators to change its parameters for different payloads. The few balancers passively self-regulate employ regulation at the end-effector. This thesis describes the development and preliminary testing of a fully passive single-degree-of-freedom (DOF) gravity balancing mechanism (GBM) that can detect the weight of the payload and adjusts its parameters automatically. The main novelty of the concept lies in an independent self-regulating mechanism that is mounted onto the proximal link of the GBM. The thesis hypothesizes that this design enables better safety, larger range of motion and loading at intermediate angles. The underlying operation of the GBM is based on two key principles: Simultaneous displacement (an energy-free method of adjustment) and a rack-pinion-spool (RPS) regulation mechanism. To test the hypothesis, the system’s self-regulating capabilities is evaluated based off a series of independent sub-functional experiments that tests its balancing, weight-sensing and regulation capabilities. Pilot experimental data show that the GBM prototype can self-regulate and compensate a range of mass from 1.23kg to 2.43kg with an efficiency of 88.3% to 95.1% with a loading angle of 135°. Additionally, the GBM can achieve a range of motion from 40o to 155.5o with no additional protrusions at the end-effector that may compromise user safety. The applicability of the GBM for robot-human interaction was tested via a single-subject surface electromyography (sEMG) test to compare the reduction in muscular effort with the GBM. Results from the sEMG shows a reduction in muscle activity by 69.4% to 77.8%. These results indicate the proposed design has met its objectives. The manner which the GBM is designed is based on a synthesis of existing GBM approaches using design tools like functional modelling and morph matrix to enhance concept generation. The framework reveals trends and areas for innovation. A matrix of design solutions adopted by previous authors is drafted and serves as a foundation for innovating new GBMs.