This is a photo of the control circuit board for the ROV dive motor. The dive motor is located in the center near the bottom of the ROV. It is a conventional pulse width modulation control circuit. The mosfet has substantial copper heat-sink surface area attached. This is required due to the high current drawn by the motors when driving a propeller underwater (average 2.5 amps). The rate at which the ROV descends is controlled by a potentiometer located on the surface control panel. In addition, we have successfully prototyped real-time modulation of the pulse width (hence motor speed) by an Analog Devices accelerometer (with op amp stage to amplify and transition between different circuit supply voltages). This design shows very good sensitivity to acceleration in the vertical axis. It will be incorporated to provide increased stability of the platform for the video cameras and FST or future manipulators.
