Synthesis of actively adjustable frequency modulators via redundant actuation: the case for a five-bar finger mechanism

A biologically inspired, novel concept for an actively adjustable frequency modulator is presented. The idea of frequency modulation stems from the human body. The human body is known to be able to modulate the spring-like impedance property in a feedforward fashion using antagonistically fighting muscles. Therefore, the motion frequency of the system can be also modulated by employing the information on the inertial property and the spring-like impedance property of the human body. Based on this concept, a methodology for the motion frequency modulation via redundant actuation is investigated. A five-bar finger mechanism driven by redundant actuators is given as an illustrative example. It is shown that the motion frequency as well as the amplitude of oscillation can be actively adjustable during the motion, and that the equilibrium position about which the vibration occurs can also be arbitrarily changed during the motion. Furthermore, using the frequency modulation capability, a point-to-point motion is accomplished by a progressive movement of equilibrium posture, which is termed a virtual trajectory. To show the effectiveness of the proposed algorithms, several simulation results are illustrated.