High Speed Visual Servoing with Ultrasonic Motors

Visual servoing refers to the closed-loop position control of the robot end-effector (Hutchinson et al., 1996) using visual feedback and should be distinguished from vision-based expert systems (Corke and Good, 1996). In this work, we focus our interest on high performance visual servoing. Our goal is to maximize the bandwidth of the visual loop. This means usually, considering the average dynamics of robots, that the use of a high speed camera is necessary. To achieve this goal, the model of the visual loop must be known with a good accuracy. This includes the dynamics of the robot and the dynamics of the vision system. The main objective of this work is to propose a new dynamic model for the vision sensor. The proposed model is validated by experiments. Ultrasonic motors are used in the experiments since they exhibit a very short response time and can be modeled by a simple transfer function, thus simplifying the decoupling between vision and actuation.