Brushless dc motor control principle, let the motor rotation, the first control department must according to the hall - sensor sensing the position of the motor rotor, and then according to the stator winding decided to open (or closed) inverter (makes) in the order of the power transistor and makes of the AH, BH, CH (these are called upper arm power transistor) and AL, BL, CL (these are called lower arm power transistor), the current flowing through the motor coil in a sequence forward (or backward) a rotating magnetic field, and interact with the rotor magnet, so can make motor chronological/reverse rotation. When motor rotors to hall - the location of the sensor sensing out another set of signals, the control of open again the next set of power transistor, continue to be in the same direction so motor rotation until control department decide to stop the motor rotor close power transistor (or only lower arm power transistor); The reverse of the motor rotor is the reverse of the power transistor.
Basically accident) can be an example of the power transistor is as follows: AH, a set of BL - AH, CL group - a group BH, CL - BH, AL a group - a group CH, AL - CH, a set of BL, but can't open AH, AL or BH, BL or CH, CL. Moreover there is always the response time of the switch because of electronic parts, so the power transistor in closed and open crisscross time will the response time of the parts into consideration, otherwise when the upper arm (or lower arm) has not yet completely closed, under the arm (or upper arm) has been open, as a result, the upper and lower arm short circuit and make the power transistor burn out.
When the motor spins, control department again according to the speed set by the driver and plus/minus the rate of Command (Command) and hall sensor signal - the pace of change compared them again (or by the software arithmetic) to determine by the next set of (AH, AH, CL, BL or BH, CL, or... ) switch guide, and length of lead time. If the speed is not enough, it will be long, and the speed will be shortened. This part of work will be completed by PWM. PWM is the way to decide whether the motor speed is fast or slow, and how to generate such PWM is the core of accurate speed control.
High speed speed control must consider the system CLOCK resolution will be enough to have time on the processing software instructions, the other for hall sensor signal - change the data access mode also affect the processor performance, and determine the accuracy and real-time performance. As to the speed control, especially in low speed starting of low speed because of the back hall - sensor signal changes more slowly, how to capture the signal mode, timing of treatment, according to the motor characteristics appropriate configuration control parameter value is very important. Or the speed return change is referenced by the encoder change to increase the signal resolution in order to get better control. The motor can run smoothly and respond well, and the proper control of P.I.D. can't be ignored. Before, the dc brushless motor is closed loop control, so the back credit number is equal to tell the control motor speed distance of the motor speed. This is the Error. If you know the error, you will have to compensate for it. The traditional engineering control, such as P.I.D. control. But control of the state and the environment is complex and changeable, if you want to control the strong and durable are factors to consider I'm afraid I can not fully grasp the traditional engineering control, fuzzy control, expert system and neural network, so will be included in also become the important theory of intelligent P.I.D. control.
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