Design and analysis of a cable driven bio-mimic arm

Abstract

The new millennium has seen an exponential increase in the number of robots used across various applications. Apart from the programming required to control any robotic system, the configuration of the manipulator and the selection of joints are also important to achieve a good design. The majority of robots currently in use are serial-configuration with rigid links as it allows easier kinematic control. However, research has shown that robots with parallelconfiguration are viable and have advantages over the serial robots such as higher stiffness and higher loading capacity. In addition, cables provide a good alternative to replace the rigid link systems in driving the robots. Cable-driven parallel robots are light weight and have simple mechanical structure and lower moment of inertia. They are able to achieve larger workspace at higher speeds with lower energy consumption.

Much research has been conducted in the cable-driven parallel mechanisms but few examined the application of universal joints. This project explores the use of cables as the actuating links of parallel robots with universal joints. In particular, a cable-driven bio-mimic arm will be design and developed to replicate the human upper arm motion, comprising the shoulder and elbow joints. The design process, from the conceptual stage to the detailed designs, and the optimization of the joint modules are geared towards achieving this project objective. Various design principles and ergonomic issues are also taken into consideration throughout the design process. The final design, using universal joints for both the shoulder and elbow joint, is able to cover 68.6% of the human arm workspace.

The prototype resembles a human arm and allows motion control of the upper portion of the mechanical arm design by a shoulder module and an elbow module, each consisting of a 4-cable parallel manipulator with a universal joint. Subsequent analysis of the prototype is carried out and documented together with the human representation of the respective poses. The conclusion and recommendations for further developments are also suggested in the report.