Control System Design And Implementation Of Self-balanced Electric Unicycle

In order to address the urban air pollution and traffic congestion, the new green energy vehicles are concerned and approved by more and more people. In this thesis, the self-balanced electric unicycle is studied. This thesis analyzed and discussed the kinertic model of the electric unicycle, attitude algorithm, dynamic self-balancing control algorithm, hub motor torque control strategy and hardware circuit design and software implementation.The physical model of self-balanced electric unicycle is similar to a moving inverted pendulum. Lagrange method is used to establish the mathematical model of self-balanced electric unicycle to study the dynamic characteristics in this thesis. According to the actual operation of the electric unicycle, linearization is made to obtain the state space equation of the electric unicycle in the adjacent area of the equilibrium point. Based on the state space equation, the system stability, controllability and dynamic characteristics are analyzed. According to the actual needs of the electric unicycle and the unicycle dynamic characteristics, this thesis proposes a double loop dynamic balance control algorithm based on pitch angle speed control, which is the inner loop of the controller. In order to improve the control performance, a fuzzy PI controller based on MAMDANI fuzzy model is designed for pitch angle speed control. Attitude control is the outer controller of balance control algorithm. In order to ensure the stability of the system, the pure proportional controller is designed for attitude control. The simulation platform of self-balanced electric unicycle is built to verify the feasibility of the control algorithm in the MATLAB/SIMULINK environment.In order to get better control effect, the accurate attitude information and the stable torque control are needed in the implementation of electric unicycle. This thesis uses gyroscope and accelerometer as the orientation-detecting sensors. The accurate attitude information is obtained through the first-order Kalman filter. The six-step transformation direction method is the traditional control method of hub motor, which causes large torque ripple and high-frequency noise. As the back electromotive waveform of hub motor is nearly sinusoidal, the discrete space vector in the low speed and field oriented control in high speed is proposed on the hub motor. The experiment platform of self-balanced electric unicycle has been built and the hardware and software design of the experimental platform have been deeply introduced. On the experimental platform, the proposed control algorithm has been verified.