A modular prosthetic arm with haptic interfacing for transradial/transhumeral amputees.

Abstract

Contemporary upper extremity prosthetics bring a lot of benefit to the amputee community. However, there are still a number of challenges facing the field of upper extremity prosthetics. These challenges include high cost and low functionality. This dissertation looks into a low-cost solution to provide a modular upper extremity prosthetic that will be suitable for both transradial and transhumeral amputees. A novel method of myoelectric control is investigated with the introduction of a haptic user interface which will enhance the functionality of the prosthesis. This approach uses haptic feedback to display information (through the use of haptic displays) about the status of the control of the prosthetic arm. The hand of the prosthetic arm is equipped with tactile sensors. These sensors read grip force, object slip, object temperature and object texture. In a novel approach to haptic feedback, this sensory information is displayed to the user simultaneously through a multi-sensory haptic feedback system. The haptic display uses vibrotactile displays to communicate the information to the user through vibrations. This approach gives the user a more holistic sensory representation. The UKZN Touch Hand was developed at a cost of US$ 1’000 for materials and parts. It is capable of gripping with 19.5 N using a power/cylindrical grip and 3.7 N using a lateral/key grip. It can hold up to 8 kg passively using a hook grip. The hand weighs 540 g including all electronics. It is equipped with pressure, temperature and vibration sensors to sense grip force, object temperature, slippage and texture. A novel simultaneous multi-sensory haptic feedback system was designed, tested on nine test subjects and shown to be a suitable form of feedback using a single vibrotactile display per sensory channel. A novel electromyography control method was developed to allow the amputee to select from a limitless list of pre-set grip types and hand gestures using only two muscles. The Touch Hand was successfully tested on a transradial amputee who used it to perform tasks such as picking up various objects, pouring a bottle of water and drinking from a cup. Future work in this research should investigate alternative haptic feedback communication protocols to optimise the communication of information. Future work should also be done in developing fitting and training software to improve the amputees fitting and learning experience of the control of the prosthetic hand.