| This study presents the theoretical results and experimental validation of an adjustable stiffness mechanism. The use of redundant actuation is emphasized in the design of a one degree-of-freedom Watt II mechanism capable of independently controlling the effective stiffness without a change in equilibrium position. This approach is in contrast to previous spring mechanism designs unable to actively control the spring rate independent of deflection, and has potential applications in various types of suspension and assembly systems. Results indicate that driving the redundantly actuated, unidirectional, spring mechanism requires attaching two direct brush-type direct current motors on each of the two grounded revolute joints and controlling the torques with corresponding power amplifiers which incorporate current control loops. The effective stiffness of the system is referenced to an output linear displacement slider and is dependent on the redundant actuator torques of the motors. To obtain the motor torques, slider displacement, and the external disturbances acting on the slider, a data acquisition system is integrated to measure the respective values in terms of current and voltage. |
