The permanent magnet brushless DC motor has a simple structure, no commutation sparks, good speed control performance, reliable operation and no excitation loss, and is therefore being used more and more widely in various fields.
In recent years, due to the development of power electronic technology and control technology, the DSP control technology of brushless DC motors, especially the control technology without position sensors, has rapidly emerged, and has become the block diagram of the starting circuit for the control of brushless DC motors in the future.
The development trend. At present, most of the commonly used position sensorless control is the electromotive force control circuit block diagram. Since the brushless DC motor has no induced electromotive force when it is stationary, this control method cannot achieve self-start. Its startup needs to be designed separately. Some current starting methods compare their advantages and disadvantages and their respective applicable occasions. Based on this, a new control method different from the traditional starting method is proposed and started. The PWM waveform is generated 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 to the brushless DC motor starts to be small and gradually increases, and the brushless DC motor is taken as Permanent-magnet synchronous motors realize variable frequency starting. At the same time, the parameters of the PWM waveform are sent to the comparator for comparison. When the duty cycle of the PWM reaches a certain value, that is, the voltage is large enough and the motor speed reaches a certain speed, a sufficiently large back EMF can be obtained. , You can switch the motor to the running state of the back-EMF control of the brushless DC motor in a timely manner.
In 240, PWM wave is produced by the incident manager, there are 3 kinds of methods to be able to produce PWM wave form, first, the comparator unit of 3 general timers produces 1 independent PWM wave through its own timer, this does not have dead zone Features. The second is that the three compare units of the general-purpose timer 1 or 2 can generate 3 PWM signals and do not have a dead-time function.
This paper uses a third generation method, which generates a pair of PWM signals with programmable dead time and output polarity using each of the three full compare units and general-purpose timer 1, dead-time unit, and output logic unit. As shown in the structure diagram, the PWM signal generated by the CMPr+ is PWM timer using a timer counter to repeat the PWM cycle by using 6 pins PWMy/CMPy. A comparison register is used to store the modulation value, and the timer counter value and the comparison register are continuously Comparing the values, when the two values ​​are equal (matching), the output jumps; when the second match is reached or the end of the timer period is reached, the output generates 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.
(Continued on page 49) The command station (which may be located on the ground or in a ship of fire, etc.) is guided missile flight. The composite lead test is a combination of the aforementioned guidance, remote guidance, and self-guided guidance.
Seek guidance, remote guidance, and composite guidance generally include components or devices such as detection, calculation, guidance, stability, and servo execution control. The above components or devices are not necessarily within the missile, but the actuator is placed inside the missile. The motor is mainly used in the servo execution control device, and different servo motors, position sensing motors, tachogenerators, and speed reducers are used according to different control methods.
1.4.2.2 Missile launcher The missile launcher is mainly a sighting machine except for the launcher. The aiming machine needs to automatically aim at the level and direction of the machine, that is, the height and direction of the direction machine and the fire control are all the same. Both follow the moving system, as shown in Fig. 8.
The mechanical loads of the leveler and the steering wheel are different. The former performs a motor output power higher than the latter. At present, the launching device uses a DC motor with a DC tachometer. The general output power is less than 10 kW and the maximum is less than 100 kW. Take the SA-2 ground-to-air missile launching execution motor as an example. The output power of the high and low machine motor is 3.2. kW, the output power of the direction machine motor is 1.6kW, and both have the same rotation speed.
(To be continued) (Continued from page 30) Symmetrical PWM Waveform Generated by General-purpose Timer In this way, changing the value of the compare register makes the pulse width of the PWM waveform from small to large, and the on-time of the controlled inverter is also from small to large. The equivalent voltage added by the inverter to the stator side of the motor also gradually increases from small to large, achieving a gradual boost of the motor stator.
Then use a register to store the commutation time. When the motor is started, the commutation frequency is very small. Pull the motor down to the synchronous state and adopt an 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 be started with a variable frequency in synchronous operation.
At the same time, using a single comparator to put a value in advance, compared with the value of the comparison register to determine the pulse width, when the two values ​​match, it represents the motor stator voltage reaches a certain value, at this time the motor speed also reached With a certain value, a sufficiently large back EMF can be obtained, and the motor can be switched to the back EMF detection control operation state. Program controlled flow charts are shown.
3 Experimental results Conclusions of the program control flow Among the various starting methods introduced, the third method of starting using the event manager that comes with the DSP chip to achieve an up-clock start, does not increase the peripheral equipment, and can ensure reliable start There is no strict requirement on the commutation time, and it can also be started with a certain load. Compared with other starting methods, it shows better advantages.
JIANGSU PERFECT NEW MATERIAL TECHNOLOGY CO., LTD. , https://www.bffloor.com