Analysis and Design of Manipulators With Decoupled and Configuration-Invariant Inertia Tensors Using Remote Actuation

The dynamics of manipulators with diagonal and/or constant inertia tensors are described by simple differential equations. This feature greatly simplifies the control of high speed manipulators. This paper presents design methods, which incorporate selection of arm structure and link inertial properties, to achieve simplified manipulator dynamics. First the concept of remote actuation is described. A model is then developed in order to analyze the effects of remote actuation on the manipulator kinematics and dynamics. The modeling is based on Kane’s partial rates along with a set notation to concisely express the system’s dynamics. Second, necessary and sufficient conditions for achieving such dynamic properties for open and closed kinematic chain linkages are derived. These techniques are then applied in the design of three degree-of-freedom planar manipulator and the three degree-of-freedom spatial M. I. T direct-drive manipulator. The mass distribution conditions for which the arm inertia tensors are diagonal and configuration-invariant are derived. The resultant dynamic equations of these manipulators are shown to be very simple.