Electrical system design of a spherical underwater robot (SUR-II)

This paper presents the electrical design for a spherical underwater robot, SUR-II. The master-slave structure control circuit is designed to realize sensor data collection, control algorithm realization, control command transmission, motor actuation and etc. TMS320F28335 and ATMEGA 2560 are used for master and slave processors respectively. Depth sensor and MEMS IMU are employed to realize closed-loop control. To enhance the accuracy of the sensor data, the noise source for sensors is analyzed, and then the sensor data calibration is carried out. To realize communication exactly between the master processor and slave processor, we define a communication law. Only the direction of thrusters is controlled by servomotors to realize underwater motion. In order to evaluate the response time and availability of the control method and electrical system, the depth control experiment and stability experiment are carried out. In these experiments, PD controller is used to control the servomotors. The experimental results show the robot can realize underwater motion just based on controlling the direction of the thruster. The response time is about 40 seconds in the depth control experiment. Because the water resistance is very small in yaw direction, the response time only 10 seconds in the stability experiment.