A Dynamic Model Based Robot Arm Selection Criterion

The selection of robot manipulator architecture, i.e. the determination of link lengths, their relative orientations, types of joints, e.g. revolute or prismatic, etc., has been largely done so far by experience, intuition and at most based on the kinematic considerations like workspace, manipulability, etc. Dynamics is generally ignored at this stage even though it is widely used for control and simulation. This paper attempts to introduce a criterion based on the dynamics of a robot manipulator, namely, simplicity of the associated generalized inertia matrix (GIM). Since the GIM influences both the control and simulation algorithms significantly, its fast computation and / or making its shape diagonal will certainly enhance the speed, precision, and stability of the robots. Two measures of simplicity, the computation complexity of the GIM in terms of floating point operations and the computer CPU time of an algorithm where the GIM appears, e.g., the inverse dynamics algorithm, are used here to evaluate a robot arm. The proposed criterion is illustrated with two -link robot arms with revolute and prismatic joints and compared with the two commonly used criteria, namely, the workspace, and manipulability. Finally, an example is taken to select an arm from the two spatial robot architectures, RTX and Stanford.