A system and method for calibrating the magnetic pole position of an electric motor

Abstract

This invention provides a system and method for calibrating the magnetic pole position of a motor. The system includes a motor, a PWM output unit, a rotor position sensor, a computing unit, a position detection unit, and a storage unit. The computing unit is connected to the storage unit, the position detection unit, the motor, and the PWM output unit. Phases A, B, and C of the motor are all connected to the PWM output unit. The position detection unit is connected to the rotor position sensor. This invention automatically calibrates the motor by identifying the deviation between the rotor magnetic pole position and the rotor mechanical position detected by the position sensor. This eliminates the need for precise alignment of the rotor magnetic poles, position sensing components, and sensor chip during the assembly of a DC permanent magnet synchronous motor system, making the DC permanent magnet synchronous motor more flexible and convenient in system assembly and applicable to more application scenarios.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a system and method for calibrating the magnetic pole position of a motor. Background Technology

[0002] In the drive control system of a DC permanent magnet synchronous motor, the controller needs to perform synchronous commutation based on the position of the motor rotor. Correct rotor position detection is crucial for normal motor drive and torque output. In existing applications, a position sensing component is typically installed on the motor rotor, and the sensor chip converts this position signal into an electrical signal output to the motor controller. However, to correctly output the electronic rotor's position signal, the rotor's magnetic poles, the position sensing component, and the sensor chip must be accurately aligned. This assembly process is complex and cumbersome, and the application is inflexible. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a system and method for calibrating the magnetic pole position of a motor.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] This invention provides a system for calibrating the magnetic pole position of a motor, comprising:

[0006] Motor, PWM output unit, rotor position sensor, arithmetic unit, position detection unit, and storage unit;

[0007] The arithmetic unit is connected to the storage unit, the position monitoring unit, the motor, and the PWM output unit, respectively; phases A, B, and C of the motor are all connected to the PWM output unit; and the position detection unit is connected to the rotor position sensor.

[0008] Preferably, the motor is a three-phase DC permanent magnet synchronous motor.

[0009] Preferably, the PWM output unit includes six driving MOSFETs and a pre-drive circuit.

[0010] Preferably, the rotor position sensor is disposed on the rotor of the motor.

[0011] Preferably, the computing unit is a microcontroller with built-in control software.

[0012] In another aspect, the present invention provides a method for calibrating the magnetic pole position of a motor, applied to the above-mentioned system, the method comprising:

[0013] Current is injected into the three-phase coils of the motor through specific drive control to establish a magnetic field aligned with the A-phase coil of the motor;

[0014] Obtain the motor rotor position signal output by the rotor position sensor in the current state, and use the motor rotor position signal as the mechanical zero position;

[0015] The mechanical zero position is used as the offset, and the rotor magnetic pole position signal of the motor is calculated according to the formula Pm=Ps–POS_Z; where Pm is the calibrated rotor magnetic pole position, Ps is the mechanical position output by the rotor position sensor, and POS_Z is the mechanical zero position.

[0016] Preferably, the step of injecting current into the three-phase coils of the motor through specific drive control to establish a magnetic field aligned with the A-phase coil of the motor includes:

[0017] A PWM pulse voltage with a duty cycle of Tn is input to phase A, and PWM pulse voltages with a duty cycle of Ts are input to phases B and C of the motor, respectively; wherein the duty cycles Tn and Ts are different.

[0018] Preferably, the PWM pulse voltage is a pulse waveform that is center-aligned between phase A, phase B, and phase C.

[0019] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0020] This invention provides a system and method for calibrating the magnetic pole position of a motor. The system includes a motor, a PWM output unit, a rotor position sensor, a computing unit, a position detection unit, and a storage unit. The computing unit is connected to the storage unit, the position detection unit, the motor, and the PWM output unit. Phases A, B, and C of the motor are all connected to the PWM output unit. The position detection unit is connected to the rotor position sensor. This invention automatically calibrates the motor by identifying the deviation between the rotor magnetic pole position and the rotor mechanical position detected by the position sensor. This eliminates the need for precise alignment of the rotor magnetic poles, position sensing components, and sensor chip during the assembly of a DC permanent magnet synchronous motor system, making the DC permanent magnet synchronous motor more flexible and convenient in system assembly and applicable to more application scenarios. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The system structure connection diagram provided for the embodiments of the present invention.

[0023] Figure 2 This is a schematic diagram of a PWM waveform provided in an embodiment of the present invention;

[0024] Figure 3 A schematic diagram of coil current provided for an embodiment of the present invention;

[0025] Figure 4 A schematic diagram of the coil magnetic field provided in an embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram of the control flow provided in an embodiment of the present invention.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1-Motor, 2-PWM output unit, 3-Rotor position sensor, 4-Arithmetic unit, 5-Position detection unit, 6-Storage unit. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0031] The terms "first," "second," "third," and "fourth," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, including a series of steps, processes, methods, etc., is not limited to the steps listed, but may optionally include steps not listed, or may optionally include other steps inherent to these processes, methods, products, or devices.

[0032] The purpose of this invention is to provide a system for calibrating the magnetic pole position of a motor. By automatically performing calibration learning through the motor controller, the system achieves automatic adaptation between the motor controller, the motor, and the rotor position sensor, eliminating the need for alignment operations between the motor rotor magnetic poles and the position sensor during assembly.

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Figure 1 The system structure connection diagram provided in the embodiments of the present invention is as follows: Figure 1 As shown, the first aspect of the present invention provides a control system for calibrating the magnetic pole position of a motor, including a position detection unit, a calculation unit, a PWM output unit, and a storage unit.

[0035] The position detection unit processes the signal from the rotor position sensor into a digital signal that can be recognized by the computing unit.

[0036] The PWM output unit outputs PWM drive voltage to the three phases of the motor.

[0037] The storage unit can store and record the mechanical zero position POS_Z of the motor, and can provide it to the computing unit for calculation.

[0038] The aforementioned arithmetic unit can output three-phase PWM control signals of the motor to the PWM output unit to achieve specific drive control.

[0039] The motor is a three-phase DC permanent magnet synchronous motor; the PWM output unit consists of three half-bridge drive circuits, including 6 drive MOSFETs and a pre-drive circuit, which can output three-phase PWM voltage waveforms to the three-phase ports of the motor.

[0040] The rotor position sensor consists of a position sensing component fixed on the motor rotor, which rotates with the motor rotor. The position detection unit detects the rotational position of the sensing component and transmits it to the processing unit via an electrical signal.

[0041] The storage unit can store the rotor position data obtained by the arithmetic unit.

[0042] The arithmetic unit is a microcontroller running control software that controls the switching of the three-phase half-bridge of the PWM output unit to realize the control process of motor magnetic pole position calibration.

[0043] In another aspect, the present invention provides a method for calibrating the magnetic pole position of a motor, applied to the above-mentioned system, the method comprising:

[0044] Current is injected into the three-phase coils of the motor through specific drive control to establish a magnetic field aligned with the A-phase coil of the motor;

[0045] Obtain the motor rotor position signal output by the rotor position sensor in the current state, and use the motor rotor position signal as the mechanical zero position;

[0046] The mechanical zero position is used as the offset, and the rotor magnetic pole position signal of the motor is calculated according to the formula Pm=Ps–POS_Z; where Pm is the calibrated rotor magnetic pole position, Ps is the mechanical position output by the rotor position sensor, and POS_Z is the mechanical zero position.

[0047] The control process in this embodiment is as follows:

[0048] This embodiment is used to identify the deviation between the rotor magnetic pole position of the motor and the rotor mechanical position detected by the position sensor. The process includes:

[0049] Step 1: Inject current into the three-phase coils of the motor through specific drive control to establish a magnetic field aligned with the A-phase coil;

[0050] Step 2: Obtain the motor rotor position signal output by the position sensor in the current state, and use it as the mechanical zero position POS_Z;

[0051] Step 3, zero calibration: According to Formula 1, the physical zero position value POS_Z is used as the offset to calculate the motor rotor magnetic pole position signal Pm.

[0052] Pm = Ps – Pd (Formula 1)

[0053] Pm is the position of the motor rotor magnetic poles, Ps is the mechanical position output by the rotor position sensor, and Pd is the deviation between the rotor mechanical position and the magnetic pole position.

[0054] The calibrated rotor magnetic pole position Pm = Ps – POS_Z (Formula 2).

[0055] Optionally, the specific drive control in this embodiment refers to inputting a PWM pulse voltage with a duty cycle of Tn into phase A, and inputting PWM pulse voltages with a duty cycle of Ts into phases B and C respectively, wherein the duty cycle Tn is not equal to Ts.

[0056] The PWM pulse voltage refers to the center-aligned pulse waveform formed by phases A, B, and C, such as... Figure 2 As shown, Tn can be greater than Ts or less than Ts.

[0057] Under the drive of the aforementioned pulse voltage, the three-phase coils of the motor will generate the following: Figure 3 and Figure 4 The currents shown are such that the currents in phase B and phase C are equal, and Ib equals Ic; thus, a current is generated in the stator windings of the motor as follows: Figure 3 and Figure 4The magnetic field shown has its axis d aligned with the axis a of phase A coil. According to the principle of interaction between magnetic poles: like poles repel each other and unlike poles attract each other. Without external load, the rotor's magnetic poles will rotate to a position aligned with axis A, achieving alignment.

[0058] The current state refers to the state in which the rotor rotates to the alignment state while maintaining the above-mentioned coil drive current.

[0059] The specific control flow of this embodiment is as follows: Figure 5 As shown, it includes:

[0060] Procedure 001: Enable specific drive control and set the duty cycles of the three-phase PWM outputs A, B, and C to 60%, 50%, and 50%, respectively;

[0061] Procedure 002: Read the rotor mechanical position signal Ps from position detection unit 5;

[0062] Process 003: Calculate the rotor speed based on the change in the mechanical position signal Ps;

[0063] Process 004: Identify whether the motor rotor is in an aligned state based on the rotation speed. When the rotor speed is 0, the rotor's magnetic poles are aligned. When the rotor speed is not 0, repeat steps 002 to 004 after a certain delay until the speed reaches 0.

[0064] Procedure 005: Reread the rotor mechanical position signal Ps from position detection unit 5;

[0065] Process 006: Record the new mechanical position signal Ps as POS_Z and store it in storage unit 6;

[0066] Procedure 007: Turn off the three-phase PWM voltage and cancel specific drive control.

[0067] Process 008: Calculate the rotor magnetic pole position, and calibrate the mechanical position signal Ps to zero according to Formula 2 to obtain the accurate magnetic pole position.

[0068] The beneficial effects of this invention are as follows:

[0069] This invention identifies the deviation between the rotor magnetic pole position and the rotor mechanical position detected by the position sensor through the control system and automatically performs calibration. This eliminates the need for accurate alignment of the rotor magnetic poles, position sensing components and sensor chips during the assembly of the DC permanent magnet synchronous motor system, making the DC permanent magnet synchronous motor system assembly scheme more flexible and convenient, and applicable to more application scenarios.

[0070] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the methods disclosed in the embodiments, since they correspond to the systems disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the system section description.

[0071] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for calibrating the magnetic pole position of a motor, characterized in that, A system for calibrating the magnetic pole position of a motor includes: a motor, a PWM output unit, a rotor position sensor, a computing unit, a position detection unit, and a storage unit; wherein the computing unit is connected to the storage unit, the position detection unit, the motor, and the PWM output unit respectively; phases A, B, and C of the motor are all connected to the PWM output unit; and the position detection unit is connected to the rotor position sensor. The method includes: Current is injected into the three-phase coils of the motor through specific drive control to establish a magnetic field aligned with the A-phase coil of the motor; Obtain the motor rotor position signal output by the rotor position sensor in the current state, and use the motor rotor position signal as the mechanical zero position; The mechanical zero position is used as the offset, and the motor rotor magnetic pole position signal is calculated according to the formula Pm=Ps–POS_Z; where Pm is the calibrated rotor magnetic pole position, Ps is the mechanical position output by the rotor position sensor, and POS_Z is the mechanical zero position. Injecting current into the three-phase coils of a motor through specific drive control to establish a magnetic field aligned with the A-phase coil of the motor includes: A PWM pulse voltage with a duty cycle of Tn is input to phase A, and PWM pulse voltages with a duty cycle of Ts are input to phases B and C of the motor, respectively; wherein the duty cycles Tn and Ts are different. The PWM pulse voltage is a pulse waveform that is center-aligned by phases A, B, and C.

2. The method for calibrating the magnetic pole position of a motor according to claim 1, characterized in that, The motor is a three-phase DC permanent magnet synchronous motor.

3. The method for calibrating the magnetic pole position of a motor according to claim 1, characterized in that, The PWM output unit includes 6 driving MOSFETs and a pre-drive circuit.

4. The method for calibrating the magnetic pole position of a motor according to claim 1, characterized in that, The rotor position sensor is mounted on the rotor of the motor.

5. The method for calibrating the magnetic pole position of a motor according to claim 1, characterized in that, The computing unit is a microcontroller with built-in control software.

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