Research On Driving Technique Of BLDCM For Virtual Orbit Vehicle

Virtual orbit vehicles combine the advantages of tramcars and buses.On the one hand,they use rubber wheels like cars,and no rails need to be laid;on the other hand,they can be grouped in multiple sections like tramcars and has the same trajectories of group vehicles.Compared with other urban rail transportation methods such as subways or tramcars,virtual orbit tramcars have the advantage of low construction cost,short construction period,low noise,and are not limited by fixed rails and overhead line networks.Provides a brand new solution for modern city transpotation.The virtual orbit vehicle tracking control realizes that the group vehicles run on the same trajectory and is the key technology of the virtual orbit transportation.Based on the project of "virtual orbit transit vehicle drive technology",starting from the perspective of suppressing the torque ripple of the drive motor and the autonomous guided tracking algorithm of the vehicle body,the following work is carried out:The article first introduced the working principle,driving mode and mathematical model of the brushless DC hub motor,and selected the three-phase six-state 120 mode as power drive mode of the motor.The commutation torque ripple calculation method for the motor under different modulation modes was deduced based on the classification principle by using phase modulation or non-commutation modulation at the time of commutation.Based on MATLAB/Simulink,a single brushless DC motor forward/reverse simulation model and a four-motor independent drive control simulation model were built.The system's dynamic and static performance was good.At the same time,the simulation verified the influence of five kinds of modulation methods on motor torque ripple,and the simulation results are consistent with the theoretical analysis.Secondly,by choosing the appropriate coordinate system and generalized coordinates,mathematical description equations of lateral distance deviation,heading angle deviation and vehicle body running speed deviation are established based on the control point model.By using the equivalent generalized mass-oscillator-damping vibration model,an absolute stable error control model that satisfies the tracking condition is derived by using the tracking deviation and the rate of change of the deviation,and the mathematical conditions that should be met when the vehicle is strictly tracked are given.Based on Ackermann's front-wheel differential steering model,the forward and backward reverse differential steering methods with smaller steering radius and higher flexibility were studied,and the control flow for differential steering and tracking realization was designed.Then,a hardware experiment platform for the brushless DC hub motor drive control system based on the DSP+FPGA architecture controller was built.The FPGA,as the main control chip,mainly fulfills the voltage,current,and Hall signal sampling and calculations of control algorithm.The DSP is responsible for implementing data communication between the main control board,the console and the monitoring and debugging interface.Programmed software programs such as PWM generation module,PI adjustment module,speed calculation module and sampling module in FPGA based on Verilog HDL hardware development language.Finally,the open loop and the closed loop experiments were completed by loading the drive control system to the virtual orbit vehicle.The experimental results shows that: The speed response of the control system is rapid,the current response delay is reduced,the closedloop performance is good,and current and torque ripple are small during PWM_ON modulation.It realizes the independent drive control of the four-wheel motor of the virtual orbit vehicle,and has the ability to go straight and can realize differential steering at a certain degree.