A non-contact laser speckle sensor for the measurement of robotic tool speed

A non-contact speckle correlation sensor for the measurement of robotic tool speed is described that is capable of measuring the in-plane relative velocities between a robot end-effector and the workplace or other surface. The sensor performance has been assessed in the laboratory with sensor accuracies of +/- 0.01 mm/s over a +/- 70 mm/s velocity range. The effect of misalignment of the sensor on the robot was assessed for variation in both working distance and angular alignment with sensor accuracy maintained to within 0.025 mm/s (< 0.04%) over a working distance variation of +/- 5 mm from the sensor design distance and +/- 0.4 mm/s (0.6%) for a misalignment of 5 degrees. The sensor precision was found to be limited by the peak fitting accuracy used in the signal processing with peak errors of +/- 0.34 mm/s. Finally an example of the sensor's application to robotic manufacturing is presented where the sensor was applied to tool speed measurement for path planning in the wire and arc additive manufacturing process using a KUKA KR150 L110/2 industrial robot.