DYNAMIC MODELING OF A ROBOT SENSOR

An inertial sensor to determine the location of rigid objects is described. Designed to be mounted at the wrist of a robot arm, the device is for use in "stack" or "tray" picking as an alternative to "bin" picking. With this method of object acquisition, the objects are arranged in a stack or a tray in a semi-ordered fashion rather than being completely jumbled up as in a bin. The sensor consists of an elastic column and a rigid platform on which the object to be located is held. Static deflections of the column (due to the weight of the object) and natural frequencies of vibration of the sensor are used, respectively, to determine the position and orientation of the object. The theoretical details for obtaining the dynamic model of the sensor are described and simulation results are presented. The dynamic model was used to predict the frequencies of vibration resulting from placing a known object at known locations on the sensor platform. The predicted values were corrected with the help of a limited number of measurements. Practical results obtained with the sensor are presented and discussed.