Slippage control for a smart prosthetic hand prototype via modified tactile sensory feedback

The human hand is one of the most complex structures of the human body, having the fingers that possess one of the highest numbers of nerve endings in the body. The hand, with its nerve endings has the capacity for the richest tactile feedback with excellent positioning capabilities. The existing hand control methods used in controlling smart prostheses have many drawbacks and need improvements. This paper proposes a new technique of controlling slippage, which is one of the major drawbacks for a prosthetic hand. A fuzzy logic control algorithm with multiple rules is designed along with a modified tactile sensory system for feedback. The slippage control acts as a complementary control system to the EMG or EEG based position control. A 5 Degrees of Freedom (DOF) hand was used which has one micro servo motor as actuator for each finger. A force sensing resistor is modified and used as a slippage sensor. First we use a reference EMG signal for getting the 5 DOF hand to grip an object, using position control. Then a slip is induced and we see the slippage control strategies work to hold the grasp. The results based on the plain sensory system and the modified system are discussed. Finally the advantages of the entire slippage control system are highlighted.