Force and explicit slip sensing for the AMADEUS underwater gripper

The design of the fingertip sensing subsystem constructed for use in a dextrous underwater gripper is presented. Two distinct types of sensor were developed specifically for this application, a force sensor and a slip sensor. The force sensor is used to determine the force exerted by the gripper on the target object, and hence to allow the force loop closure required to carry out dextrous manipulation and to handle delicate marine samples. The function of the slip sensor is to detect the occurrence of slippage between the fingertip and the target, and this information can be used in a variety of ways: for example, providing a warning system to the force control loop or enhancing the gripper's exploratory capabilites in areas of poor visibility. Due to changes in ambient pressure, the force sensor is a simple robust device based on strain gauge technology developed specifically for this application. The sensor is capable of being incorporated on an artificial fingertip mounted at the extremity of the finger of a dextrous gripper. The slip sensor is an extremely small PVDF-based device capable of being shaped to suit the curvature of the fingertip. An analysis of both sensors' operation is presented, along with calibration measurements and results for the first prototypes.