A new type of spherical robot based on the concept of changing the barycenter of the system is presented. The robot is consist of a shell and inner driving unit inside. The driving motor can provide the torque to move forward and backward, and the other motor can control the movement of a slider which is used to change the barycenter when turning the direction. The whole system is easy to design and the plate inside can be installed with certain sensor for special tasks. The dynamic model of the robot is introduced. The simulation results which shows the accordance with the experiment is presented.

Based on the analysis of six kinds of working points, the process function of torpedo thermal power propulsion system is solved. The results show that the process transfer function is approximate to inertial link. PI control algorithm is presented and its parameters are deduced. The algorithm can not only control the output variables, but also can monitor the intermediate variable. Closed-loop control system model is established. Variable speed characteristics of torpedo at constant depth and steady speed characteristics in depth-changed process are simulated by MATLAB. Simulation results indicate that the system has satisfactory dynamic performance and the control quality performs well.