The Multi-Finger Hand Control Scheme Based On Synchronization Concept

The study on the multi-finger hand is one of the important aspects for improving the manipulative capbility and the intelligent levels of the robot system. Moreover, the control is a keystone of the multi-finger hand. Given the specific hardware, the control system determines the manipulative performance of the multi-finger hand. According to the national nature science fund program"Research of the real-time force optimization and independent manipulating control of the multi-finger robot hand"(code: 60675045), this dissertation studies the control scheme of the HIT/DLR multi-finger hand based on synchronization.Because the finger of HIT/DLR hand is actuated by three motors and its base joints which have two freedoms are driven by two motors and transmitted by a symmetrical differential machine, the synchronization among the drivers acts as an important factor affecting the finger's tracking precision. Therefore, in this dissertation, after analyzing kinematics and dynamic of the multi-fingered hand, synchronized control is employed in the finger control scheme to harmonize the drivers. The synchronous errors among drivers are designed according to finger kinematics of desired trajectory. The position synchronized control scheme of the finger is studied, including feedforward of velocity and acceleration, feedback of tracking errors and synchronous errors, and a saturation control. The control scheme is simple and does not require the explicit dynamic modeling parameters. The finger system with the proposed control scheme can be asymptotically stable according to Lyapunov stability analysis. Experiments demonstrate that it attains better tracking precision than conventional non-synchronized control scheme. The system will have less force overshoot and transient time of the impedance control, when applying the position controller or force controller based on synchronization as an inner-loop with better precision.The harmonization among the fingers is an important aspect of the research on multi-finger manipulation. In this dissertation, position synchronized control scheme of multi-finger hand, employing similar structure with position control scheme of the finger, is studied to harmonize the fingers when the operated object moves linearly, based on multi-finger kinematics analysis. Experiments demonstrated that this control scheme could improve the operating precision. In order to maintain the forces among fingers and the object, force synchronous errors are introduced to a parallel loop of the position synchronized control scheme of the multi-finger hand to modify desired position, which could improve the manipulative capability.