Angular Error Reduction of a Machine Vision System using a Trapezoidal Trajectory Velocity Profile

Abstract

Nowadays laser scanners play an important role in technology and research, when it comes to measure 3D coordinates physically and in real time of any object under observation. Laser scanners have to measure the 3D coordinates of these objects in shortest time and with the smallest measuring error. A novel laser scanner called Technical Vision System (TVS), which uses Dynamic Triangulation and DC motors, was developed and proven to represent a fast and reliable scanning system. Previous research used the step response of the TVS mechanical actuators (DC motors), which can overshoot if certain controller parameters of the closed-loop control are selected. If the overshoot is undesirable, a trade-off must be made between speed and overshoot of the step response. Thereby, present paper describes a new approach to control the actual angular position of the TVS DC motors using a trapezoidal profile for the DC Motor velocity. The DC motors step response is replaced by a trajectory response, which allows the reduction of the relative angular error of the DC motors shaft to a value less than or equal to 0.1 percent. Also, the design of the control system, to implement the trapezoidal trajectory profile for the DC motor velocity in practice, is described in detail.