Establishment and Verification of Finger Joint Kinematic Model Based on the Combination of Medicine and Engineering
Hand exoskeletons are one of the primary choices for hand rehabilitation training,and their comfort and safety largely depend on their adherence to human finger joint kinematics.In order to establish an accurate finger joint kinematic model,medical images of the finger flexion and extension process are first collected.The analysis of joint motion during the process identified how the finger bones make contact and demonstrated that during joint rotation,the motion of the two finger bones involves both rolling and sliding,thereby proving that finger joint motion is non-fixed center rotation.Next,the"instantaneous center radius method"is proposed to calculate continuous instantaneous center trajectories.Through polar coordinate transformation,continuous instantaneous center trajectory curves for each finger joint are obtained.By using angle acquisition devices that can adapt to changes in the instantaneous center of finger joints,the patterns of joint angle changes are captured.This led to the establishment of a correlation mapping of finger joint movements and an analysis of joint angle and angular velocity characteristics.Finally,by employing equivalent instantaneous centers,the finger joint kinematic model is integrated with engineering applications.A straddle rotating pair that can locate the equivalent instantaneous centers of finger joints is designed and installed on the hand exoskeleton mechanism for kinematic testing and human-machine compatibility testing.The results show that exoskeleton mechanisms conforming to finger joint kinematic characteristics can better replicate the physiological finger movement trajectory,and they apply lower pressure on different segments of the fingers during assistance,thus confirming the effectiveness of the model.
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