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.