Abstract
In general, a robot arm has equal number of actuators to number of its joints, whereas a human extremity has an antagonistic pair of bi-articular muscles acting simultaneously on both joints in addition to the antagonistic mono-articular muscles on each joint. In the present study, mechanical properties of a two-joint robot arm equipped with three pairs of antagonistic Mackibben artificial muscles were examined theoretically and experimentally in terms of control engineering. The results obtained in this study demonstrated that the viscoelastic properties and the output forces developed at the end point of the robot arm were controlled independently in the task coordinate system. This might further suggest that, as to control of trajectory, position and velocity of the end point in the task coordinate system, open loop control instead of feedback control will be available in the muscle coordinate system, but not, in the conventional joint coordinate system.
