the equation of motion of knowable by dc motor: acceleration is proportional to the torque of the motor, and the torque is proportional to the motor current, therefore, to achieve high accuracy, high dynamic performance of motor control, you need to the speed of the motor at the same time, current and position for testing and control. Figure 1 is a brushless dc motor control system block diagram, the system has been set up in the speed regulator and current regulator, and adjust the speed and current of motor, respectively between the cascade connection, the speed regulator output as a current regulator input, then use the output of the current regulator to control the PWM unit.
DSP brushless dc motor entire digital control system for analytical
as shown in figure 1, the system control unit can be divided into two parts: the function of the dotted line frame composed of TMS320LF2407A DSP minimum system implementation, he includes DSP and external storage, others for feedback signal acquisition part. Current feedback signal measured by the hall element, through A/D module F2407 into digital quantity, rotor position signal is used to generate the correct rotor commutator, photoelectric encoder detection and feedback back to the motor rotation direction and Angle DSP system, form A closed loop control. System position given by the upper machine. Three-phase ac input after rectifying, voltage regulator to provide dc power for inverter circuit, inverter circuit of trigger signal provided by the upper machine, the purpose of which is the output of adjustable duty ratio of PWM signal, by adjusting the width of the PWM signal to control the on and off time of power tube, so as to realize control of the brushless motor. Control strategy of
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this system through the three closed loop (The position loop, speed loop and current loop)Structure to realize the servo control of the machine. As shown in figure 2.
DSP brushless dc motor entire digital control system for analytical
when the motor running, the position of a given signal deviation after (Ua and the feedback position signal of the UbPosition loop)PID regulating speed reference Vg, feedback controller according to the measured position information to calculate the current speed & omega; S, brushless motor, Vg and & omega; S PI calculated in DSP (Speed loop)Get the current for A given voltage reference Uig, motor winding current feedback signal after A current sensor detection from A/D into DSP, by transformation from the current primary loop current feedback voltage Uif with Uig Uif PI calculation, get the output of the current regulator to adjust the duty ratio, and control conduction and shut off the power switch tube, so as to realize the brushless dc motor position, speed, current or torque control.
in the three closed loop control system, current loop and speed loop are the inner ring, outer position loop. Current loop is to improve the rapidity of the system, and the effect of current loop internal interference suppression, limit the maximum current guarantee the safe operation of the system, current loop PI regulator. The effect of speed loop is to increase the system ability to resist load disturbance and inhibit speed fluctuation, speed loop PI regulator. The role of the position loop is ensure static precision and dynamic tracking performance of the system. Position loop adopts the integral separation PID control, namely, at the beginning of the track was accused of amount to cancel integral action, make the proportional fast track the change of the deviation, when charged is closer to the new value adding integral action again. This can avoid to overshoot and can shorten the time of the steady state, have the effect of the integral correction. Figure 3 for the step response curve and location tracking results step type.
