Brushless dc motor controller commutation method: hall effect sensor, encoder, or rotating transformer

by:Hoprio     2020-07-21
Brushless dc motor controller (
BLDC motor controller motors) Is a kind of dc power and through external motor controller are adopted in the control of electronic commutation of the motor controller. Before exploring BLDC motor controller feedback option motors, to understand why they are needed is crucial. The BLDC motor controller can be configured for single phase motors, two phase and three phase; One of the most commonly used configuration for three phase. Phase number match the number of stator winding and rotor magnetic pole number according to the different application requirements can be any number. Because of the BLDC motor controller of rotor motors affected by the rotation of the stator poles, so must track the stator magnetic pole position, to effectively drive the three phase motor controller. Therefore, to use motor controller controller in three phase generated on the six steps commutation mode controller. The six step ( Or reverse phase) Mobile electromagnetic fields, which make the rotor shaft moving permanent magnet motor controller. By using the standard brushless dc motor controller commutation sequence, brushless motor controller controller can use high frequency pulse width modulation ( 脉宽调制) Signal, effectively reduce the motor controller under the average voltage, so as to change the motor speed controller. In addition, this setting by a voltage source is used for all kinds of motor controller, greatly improved the design flexibility, even if the rated voltage of the dc voltage source is greatly higher than that of motor controller is no exception. In order to keep the system relative to the brush efficiency advantages, the brushless dc motor controller and the controller needs to be installed between the very strict control circuit. The importance of feedback technology is embodied in here; Controller to maintain precise control of motor controller, it must always be to master the exact position of the stator relative to the rotor. Expectations and actual location any non alignment or phase shift may cause unexpected situation and performance degradation. Controller for brushless dc motor commutator can adopt many ways to achieve this feedback, but the most common way is to use a hall effect sensor, encoder, or rotating transformer. In addition, some applications will also depend on sensorless commutation technology to realize the feedback. Position feedback since the birth of brushless dc motor controller, hall effect sensors has been implementing the reversing the main feedback. Only need three sensors for three-phase control and lower the cost per unit, so simply from the Angle of BOM cost, they are often realize reversing the most economical choice. Motor controller embedded in the stator of hall effect sensor to detect the rotor position, so that you can switch transistor to drive motor controller of three-phase bridge. Three hall effect sensor output generally marked as U, V and W. Although the hall effect sensor can effectively solve the problem of BLDC motor controller motors reversing, but they just met the BLDC system motors needed to half. Although the hall effect sensor can cause the controller to drive the brushless dc motor controller, but unfortunately, the control speed and direction only. In the three-phase motor controller, hall effect sensor can only provide the Angle position within each electric loop. As to an increase in the number of poles, each mechanical rotating electric cycle number increases, and as BLDC use motors become more popular, the demand for precise position sensing is also increasing. In order to ensure the solution sound and complete, BLDC system should provide real-time location information motors, so as to make the controller can not only track speed and direction, can also track travel distance and Angle position. To meet the demand for stricter location information, common solution is to add to the brushless dc motor controller incremental rotary encoder. Usually, besides hall effect sensors, will be in the same add incremental encoder feedback loop control system. The hall effect sensor used for motor controller reversing and encoder are used to more precisely track position, rotation, speed and direction. Because the hall effect sensors in each hall only state change provides a new location information, so its precision reach every power cycle only six state; And for bipolar motor controller, only six state for each machine cycle. And can provide resolution to thousands of PPR ( Turn each pulse number) Millions of incremental encoder, Can decode the four times the number of state changes) Compared to both the necessity is obvious.
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