Research On Brushless DC Motor Control System Used In Electric Pallet Truck Steering System

The thesis was supported by the project “Development of Control System for Electric PalletTruck Based on CAN Bus”(No.2009C31022), founded by Science and Technology Project ofZhejiang Province. In the project, a brushless DC motor was used as steering motor in the electricpallet truck. And the steering motor control system was carried out in this thesis, where fuzzy PIcontrol strategy, compared with PI control strategy, was applied to motor speed control.At the beginning, background and significance of the research were elaborated anddevelopment of steering system and BLDC motor control system were introduced. Then, the mainresearch work was put forward. Overall scheme of steering motor control system was designed inchapter2. This scheme adopted double-closed-loop, where outer was a speed-loop and inner was acurrent-loop. The speed-loop could reduce load turbulence and make speed stable, meanwhile thecurrent-loop could make current stable and reduce voltage turbulence. The dsPIC30F3010fromMicrochip Technology was chosen as CPU of the control system. Three-phase and Y-connectBLDC motor put whole bridge driving way and PWM speed control strategy to use. The rotorposition which could be used as speed calculation was detected by Hall sensor fixed in motor.Phase current signal was detected by using a sampling resistance. After overall scheme finished, asimulink model of steering motor control system was made based on mathematical model. Thissimulink model contained a fuzzy adaptive PI controller. Simulation analysis was carried out in thelast of chapter3.After completing the above motioned work, the process of designing hardware system andsoftware system was expounded. Beginning with a global analysis, the hardware design includedmotor drive circuit design, phase current detected circuit design and DSC peripheral circuit design.In each design process, the reason for chosen component was explained particularly. Anti-interference measures were also discussed. In software design section, fuzzy PI control strategy inthe software system was devised. Control code of each functional module was introduced,including initialization module, CNInterrupt module for Hall signal processing, speed calculatemodule, speed control module, current control module, etc.At last, experimental research was taken over. The result show that regulation time of speedresponse in fuzzy PI control strategy was0.82s, compared with1.0s in traditional PI controlstrategy, when applied full load and1700rpm reference speed to system. Meanwhile, theovershoot in fuzzy PI control strategy was slighter.