Development of a low-cost underactuated and self-adaptive robotic hand

Emerging commercialised anthropomorphic hand prostheses have two main categories: expensive ones with remarkable functionality afforded by complex control systems, and inherently inexpensive ones with basic gripper-like aptitudes that do not fully fulfil the basic physical and emotional requirements of upper-limb amputees or individuals with upper limb congenital defects. This paper aims to establish a middle ground between these two commercial alternatives by realizing a low-cost and highly functional robotic hand. All five digits of the proposed robotic hand are controlled by a single DC motor. This desirable feature is afforded by the implementation of under-actuation. The under-actuation in the fingers is achieved through four-bar linkages coupling with cartwheel flexure joints, which leads to not only shape adaptation, i.e., the ability to naturally adapt to the form of the article being grasped without the aid of intricate control systems, but also low cost due to the possibility of monolithic fabrication (e.g. 3D printing) and ease of control. The under-actuation in the palm system is implemented via the use of a differential pulley mechanism embedded thereof, which furthermore results in low cost by reducing the number of actuators and simplifying the control system. A simple and easy-to-use control system based on voice commands through a smart phone was also developed. It is envisaged that the proposed design can also be applied in various engineering environments to meet adaptability/underactuation needs.