Abstract

Background: In order to avoid undesired slide or damage, desired grasping force should be discrepant by the prosthetic hand when grasping soft or hard objects.

Methods: A method was proposed in which a force sensor and an optical encoder are used to estimate the stiffness of the object being grasped. Based on contact-impact force model, a fuzzy logic system for stiffness estimation determined by contact force and the rotating angle of motor is constructed.

Results: In order to avoid undesired deformation, the main controller modifies the PID gains based on the estimated stiffness of the grasped objects.

Conclusion: The experiment results are presented to demonstrate the effectiveness of the proposed method.

Keywords: Prosthetic hands, underactuated mechanism, stiffness estimation, grasping force control, finger mechanism, EMG signal.

Graphical Abstract