Research On BLDC Motor Control System Applied In Electric-Bicycle Based On DSP

Brushless Direct-current Motor (BLDC) has been widely used in many industrial applications due to its advantages such as small size, light weight, high efficiency, low noise and so on. The BLDC not only has a series of AC motor's advantages, such as simple in structure, reliable operation, convenience to maintain, etc, but also has a lot of DC motor's traits of high operating efficiency, no excitation loss, excellent speed adjusting performance, etc. Thus it has been widely used in computer peripherals, office equipment, household appliances, electric vehicles and industrial control. Meanwhile, China has rich rare earth resources. The development of BLDC has a great advantages.There are four main research focus on BLDC:Sine wave control, non-sensor technology, torque ripple suppression, application of advanced control algorithms.In this paper, a study in this direction of the application of advanced control algorithms on a BLDC is develped, aiming at improving the disturbance rejection performance and speed performance of BLDC by using advanced control algorithms.Firstly, the development and research background of BLDC system is introduced. The characteristics and flaws of major BLDC control algorithms are discussed in brief. Then according to the principle of BLDC speed regulation, BLDC's mathematical model is established through theoretical analysis. Then the double closed loop control scheme of BLDC system is discussed.In the following parts, there is a detailed description of the control system's design about BLDC. A scheme of BLDC motor control system with the core of DSP2812 which has advantages of high-speed digital computing performance is built up. Then the hardware and software designs of the system according to the preceding solutions are discussed in detailed. For the hardware part, after a discussion on the whole design, the design of several chief circuits is expounded. For the software part, with the introduction of modularization design concept, some procedure flow charts of main program subroutine are offered and several problems of software realization are investigated.Brushless DC motor in the practical application is subject to various disturbances including the uncertain model parameters, external load disturbance and commutation torque ripple. Two different disturbance observers are introduced to observe the lump disturbances of BLDC system in the paper. Then the estimated value of disturbances is used in the feed-forward compensation. Experimental comparisons with traditional PI show that the compound control method based on disturbance observer has better anti-disturbance performance. The system disturbances can be divided into two types of periodic disturbances and aperiodic disturbances. Extended states observer can only estimate asymptotically constant or slowly-varying disturbances and has poor effects on periodic disturbance suppression. Internal model principle is introduced to observe and suppress periodic disturbances. To the left disturbance which can not be observed, sliding model control is used to suppress.Because of the major of system disturbances have been observed precisely and compensated, the integral sliding model control(ISMC) just needs a small switching gain for disturbance rejection.At last, simulations and experiments both verify the effectiveness of the algorithms proposed.