Abstract— 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