Robotics and Automation Expert

Dual Arm Robot Kinematics (page 5)

The compliance criteria describe the robotís ability to perform precision operations under load. They also correspond to the vibratory modes of the robot. Of the compliance criteria, the potential energy partition values, are particularly important. The potential energy partition values measure the distribution of compliance energy and how it changes as the robot moves. An unusually high compliance energy content in any part of the robot indicates a problem with the robotís design. Rapid changes in compliance energy ndicate large local forces, which correspond to large actuator demands and decreased precision. 

The kinetic energy performance criteria address high-level issues represented in relatively simply 
formulations. Large changes in kinetic energy correspond to very large demands on actuator power. Very rapid changes in the kinetic energy represent shocks to the robot. 

Dual-Arm Robot Example 

This example illustrates the application of the motion coordination method described above as applied to the Dual Arm Work Module (DAWM) designed and recently demonstrated at Oak Ridge National Laboratory (Figure 4.). The DAWM is a dual-arm manipulator system designed to perform an extremely wide variety of tasks, thus amortizing development costs. These tasks include disassembly of process equipment, cutting pipes, size reduction of equipment, transport of materials, and decontamination of floors, walls, and remaining equipment. The DAWM has 17 DOF arranged in 2 serial chains each having 8 independent DOF and sharing 1 common center rotational joint. Schilling Titan II manipulators form the last six DOF for each arm. 

The example begins with a reverse position analysis of the Schilling Titan II manipulators. Figure 4. shows a schematic of the Schilling arm. The offset at the wrist prevents the last three joint axes from intersecting at a point (a spherical wrist), thus precluding a reverse position solution that simply decouples the positional and orientational constraints. The following analysis provides a solution involving polynomials of degree 2 of less. 

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