| Applications for modern industrial robots have generally been limited to low-precision, non-contact tasks, because in practice, it is generally not possible to adequately engineer even a manufacturing environment to a sufficiently high degree of precision such that position control, alone, is adequate. This limitation has severely restricted the range of economically justified industrial robot installations. Cross-coordinated control serves to extend that range by providing a practical, experimentally verified solution to the problem of simultaneously controlling both the motion of and the constraint forces acting upon a robot end-effector, which is in contact with a rigid environment.; More precisely, this work provides a semi-empirical method for the hybrid control of a voltage-controlled industrial robot, such that the geometric constraints are explicitly accounted for. The kinestatic analysis was based on a model of the environment using Ball's reciprocal screws to characterize the nature of the constraints. This approach was chosen so as to ensure that the constraint formulation process was invariant with respect to a change of origin, a change of scale, or a change of basis.; The resulting theoretical development, combined with a laboratory implementation which employed an instrumented, anisotropic, mechanically compliant wrench sensor, resulted in a system that is kinemetically, dynamically and kinestatically stable. Consequently, this approach constitutes a general solution to the problem of performing the commonly encountered industrial tasks which, if automated, would require contact between the robot's end-effector and a rigid environment. Several representative tasks were demonstrated in the laboratory, using a modified, General Electric P60 industrial robot.; The potential for cross-coordinated control to extend the range of economical applications is especially significant, since this method is well suited for implementation as an augmentation, thus permitting the continued use of most existing motion control hardware and software. |
