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The permanent magnet brushless DC motor has simple structure, no commutation spark, good speed regulation performance, reliable operation and no excitation loss, so it is more and more widely used in various fields.
In recent years, due to the development of power electronics technology and control technology, the DSP control technology of brushless DC motor, especially the control technology without position sensor, has rapidly emerged, and it will become the block diagram of the control circuit of the brushless DC motor control in the future.
The development trend. At present, the commonly used position sensorless control is the dynamic control of the block diagram of the anti-electric starting circuit. Since the brushless DC motor does not induce the electromotive force when it is stationary, this control method cannot realize self-starting, and its starting needs to be separately designed. At present, some popular starting methods are compared with their advantages and disadvantages and their respective applicable occasions. On this basis, a new control method different from the traditional starting method is proposed and started. The PWM waveform is controlled by the DSP to control the inverter, so that the commutation frequency of the inverter is gradually increased from small to large, and the stator voltage of the brushless DC motor starts to be small and gradually increases, and the brushless DC motor is used as the brushless DC motor. The permanent magnet synchronous motor realizes variable frequency starting. At the same time, the parameters of the PWM waveform are sent to the comparator for comparison. When the duty ratio of the PWM reaches a certain value, that is, the voltage is sufficiently large, and the motor speed reaches a certain speed, a sufficiently large back electromotive force can be obtained. Then, the motor can be switched to the operating state of the brushless DC motor back electromotive force control in a timely manner.
In 240, the PWM wave is generated by the event manager. There are three methods to generate the PWM waveform. One is that the comparison unit of the three general-purpose timers generates one independent PWM wave through its own timer. This does not have a dead zone. Features. The second is to use the three comparison units of general-purpose timer 1 or 2 to generate three PWM signals, and does not have the dead zone function.
In this paper, the third generation method is adopted. Each of the three full comparison units and the general-purpose timer 1, the dead-band unit and the output logic unit generate a pair of PWM signals having a programmable dead zone and an output polarity. As shown in the figure, the 6-pin PWMy/CMPy, CMPr+ generates the PWM signal by repeating the PWM period with a timer counter, using a compare register to store the modulation value, and constantly changing the value of the timer counter to the compare register. The values ​​are compared. When the two values ​​are equal (matched), the output jumps; when the second match is reached or the end of the timer period is reached, the output produces another opposite transition, resulting in an output. Pulse, see. Obviously, the transition time of the output signal is determined by the value of the compare register. Changing the value of the compare register changes the width of the pulse.
(Go to page 49) Guided missile flight on the command post (which can be located on the ground or on fire in the water). The composite guide bow test is a guide for the above-mentioned seek guidance, remote guidance and autonomous guidance.
The seek guidance, remote guidance, and composite guidance generally include components or devices such as detection, calculation, guidance, stabilization, and servo execution control. The above components or devices are not necessarily within the missile, but the actuator is placed within the missile. The motor is mainly used in the servo execution control device. Different servo motors, position sensing motors, tachometer generators and reducers are used according to different control methods.
1.4.2.2 Missile launcher The missile launcher is mainly a sighting machine in addition to the launcher. The aiming machine needs to automatically aim at both the high and low machine and the direction, that is, the high and low direction and the aiming of the steering machine and the fire control are the same, and the follow-up system is adopted, as shown in 8.
The mechanical load of the high and low machine and the steering machine are different. The former performs the motor output power and the output power of the motor is larger than the latter. At present, the execution motor for the launching device is also a DC motor with a DC speed measuring machine. The general output power is below 10 kW and the maximum is not more than 100 kW. Take the execution motor of the SA-2 ground-to-air missile launch as an example. The output power of the high and low machine motor is 3.2. kW, the motor output power of the steering machine is 1.6kW, and the two speeds are the same.
(To be continued) (Continued from page 30) The symmetrical PWM waveform generated by the general-purpose timer. Modify the value of the comparison register to make the pulse width of the PWM waveform from small to large, and control the inverter's on-time from small to large. The equivalent voltage applied by the inverter to the stator end of the motor is also gradually increased from small to large, realizing the gradual boosting of the stator of the motor.
Then use a register to store the commutation time, so that the commutation frequency is very small when the motor starts, pull the motor to the synchronous state, and use the open-loop control method to gradually increase the commutation frequency of the motor, that is, change the register. The phase time is gradually reduced, so that the motor can achieve variable frequency starting in synchronous operation.
At the same time, a single comparator is used to pre-set a value, which is compared with the value of the comparison register that determines the pulse width. When the two values ​​match, it represents a certain value reached by the motor stator voltage, and the motor speed also reaches With a certain value, a sufficiently large back electromotive force can be obtained, and the motor can be switched to the back electromotive force detection control operation state. The flow chart of the program control is shown.
3 Experimental results Program control flow conclusion Among the various starting methods introduced, the third research starting method utilizes the event manager built in the DSP chip to achieve the up-conversion start, without adding peripheral equipment, and can ensure reliable starting. There is no strict requirement for the commutation time, and it can also be started with a certain load. Compared with other starting methods, it shows better superiority.
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