Sensorless Computer Control of an Underwater DC Manipulator

Virtually all manipulators used on today´s underwater remote operated vehicles (ROV) are controlled manually by human operators. Thus, extensive sensory information about speed, position, and load for the different joints of the actuator is often not needed. Especially the de-manipulators on small- and middle-class ROVs often offer no sensory information at all. Given that we use such a de-manipulator among others in a research project dealing with computer-controlled autonomous underwater manipulation, we needed the speed and position information and an estimation of the force applied by the manipulator, especially of the gripper. As the refit of an existing underwater manipulator with additional sensors is quite challenging and error-prone, we developed a sensorless control for the dc-manipulator based on the back EMF of the actuators.