Control principle and working principle of DC motor
Control principle
Brushless DC brush motor control principle, to let the motor rotation, first control unit must according to Hall sensor induction motor rotor position, and then in accordance with the stator winding decided to open (or close) converter (inverter) in power transistor in order, inverter ah, BH and CH (these are called arm power transistor) and Al, BL and Cl (these are called for under the arm of power transistor), the current sequentially through the motor coil produce along to (or reverse) rotating magnetic field and interacts with the rotor magnet, so you can make the motor clockwise and anti clockwise rotation. When the rotor rotates to the hall sensor sensing the location of another group of signal, the control unit again to open the next group power transistor, motor cycle so can continue to rotate according to the same direction until the control unit decides to motor rotor stop the closure of power transistor (or only under the arm of power transistor); to reverse rotor power transistor is turned on in reverse order.
Basic power transistor driving can be for example as follows: ah, BL, a group of, ah, CL group > BH, CL group > BH, Al group, CH, Al group, CH, BL group, but never Kaicheng ah, Al or BH and BL or CH, Cl. In addition because the switch of the electronic parts. Response time, so power transistor in the closing and opening of the staggered time to be part of the response time is taken into account, otherwise when the upper arm (or under the arm) has not completely closed, lower (or upper arm has been opened, as a result, the upper and lower arm short the power transistor burned.
When the motor rotation, the control unit will be according to the speed driver set speed and add / deceleration rate which consists of command and the hall sensor signal changes to be alignment (or by the software computing) decided to come back by the next group (ah, BL, or ah, Cl, or BH, Cl or...... Switch on, and the length of the conduction time. Is open long enough speed, speed over the short cut, this part of the work to be completed by PWM. PWM is the speed or slow way to decide the motor, how to generate such a PWM is to achieve the core of the more precise speed control.
Control the speed of the high speed must be taken into account in the system of the clock resolution is sufficient to grasp the processing time of software instructions, also for the hall sensor signal changes in the way of data access also affects processor performance and determine the correctness and real-time nature. As for the speed control of the low speed especially low-speed start is because the return of the hall sensor signal changes more slowly, how to capture the signal, the processing time and according to the proper configuration of the characteristics of motor control parameters is very important. Or change the speed of return to the change of encoder for reference, the signal resolution increased in order to get better control. The motor can run smoothly and the response is good, the P.I.D. control can not be ignored or not. Before mentioned brushless DC motor closed loop control, so the feedback signal is tantamount to tell how motor speed range speed control, and this is the error (error). Know the error naturally to compensate for the traditional engineering control such as P.I.D. control. However, control of the state and environment is in fact complex. If you want to control the rugged will have to take into account the factors I'm afraid not traditional engineering control can be mastered, so fuzzy control, expert system and neural network will also be included in the theory become intelligent P.I.D. closed loop control is very important.
Working principle
DC motor inside is fixed on the annular permanent magnet, the current through the coils in the rotor generated ampere force, when the rotor coil and the magnetic field is parallel, and then continue to by the direction of the magnetic field will change, so at this time, at the end of the rotor brush to switching sheets alternately contact and thus on the coil current direction changing, constant Lorentz force generated by the direction, so the motor can keep a direction of rotation.
The principle of the DC electromotive force to the working principle of the DC generator is to the alternating electromotive force induced in the armature coil, by the commutator with brush of the role, so that leads from the brush end.
Direction of induction electromotive force by the right-hand rule to determine (magnetic induction line point to palm, thumb pointing in the direction of movement of the conductor, the other four fingers pointing is the direction of the induced electromotive force in a conductor).
The conductor the direction of force with the left hand dingze sure. The electromagnetic force formed a role on the armature a moment and the moment in the rotating motor said electromagnetic torque and torque direction is clockwise, tried to make the armature counterclockwise rotation. If this electromagnetic torque can overcome the armature resistance torque (such as the friction caused by the friction torque and other load torque), the armature can rotate counterclockwise.
