Servo Design for a Laser 3D Measurement System

The servo design of a laser 3-D measurement system is discussed in this paper. The laser 3-D measurement system uses two sets of tracking mirrors to reflect laser beams loward a retro reflector attached to the measurement object. The servo system checks the offset of the reflected beam and corrects the mirror orientations so that the laser lights will always follow the measurement point. By applying inverse kinematics to the mirro rotation angles, one can then calculate the position of the target point. The system is a highly nonlinear system. Usual servo design specifications do not apply. In this paper, we derived the relationship between the tracking angle rotations and the measured beam offsets. By including this relationship in our model the H
_∞
optimization technique can by applied for controller synthesis. All the design specifications are then directly implemented. Experiments are performed to verify the results.