Mechatronic design and optimisation of a low-cost prosthetic hand.

Abstract

The Touch Hand II was developed to improve on the first version, addressing the lack of low cost myoelectric controlled hand prostheses. The improvements included a lower materials cost of $ 635.14, an aesthetically appealing human{like form factor, a reduced total mass of 486 g (including the wrist and electronics), a 211 % increase in grip strength, and a 3.83 times higher allowable palm load with a 1.7 factor of safety. Costs were reduced predominantly due to 3D printing and using sensorless technology, based on speed and torque estimation through brushed dc motor back-emf and current measurements. The compact design was accomplished by using a unique finger actuation and trajectory concept, and integrating a custom PCB. An intuitive command selection protocol was developed with the aid of a GUI. A finite state machine was used to successfully switch between speed and grip force control depending on whether an object was in contact with the fingers during a close/open command. The design has accommodated the future addition of myoelectric control, sensors, and sensory feedback.