A Sensorless Ramp Assist Control Method for a DC Brushed Motor

Abstract

The present invention relates to the technical field of vehicle motor control, and particularly relates to a sensorless ramp assist control method for a DC brushed motor. The specific steps are as follows: when the speed is not greater than 30 km / h, the motor speed is calculated through the first motor model; when the speed is greater than 30 km / h, the motor speed is calculated through the second motor model. After obtaining the motor speed, speed closed-loop and current closed-loop control of the motor are carried out to improve the stability of vehicle parking and the starting efficiency of the vehicle. By using different motor models to calculate the motor speed at different speeds, the present invention can effectively solve the influence of motor temperature rise on the calculation speed of back electromotive force, and can also avoid the problem of inaccurate speed measurement caused by the insignificant disturbance of the carbon brush commutation waveform at low speeds. It is generally applicable to motors of the same specification, and thus better realizes the detection of speed. When parking downhill, the electromagnetic brake can be locked after the motor speed completely stops, which can effectively avoid the wear of the brake caused by the inertia of the motor.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle motor control, and particularly relates to a sensorless ramp assist control method for a DC brushed motor. Background Art

[0002] For the control of traditional DC brushed motors, an encoder is generally used as the speed closed-loop feedback to achieve precise real-time speed and position control. For applications without speed sensors such as encoders, it is necessary to establish a motor model to estimate the current speed of the motor. Currently, it is widely used to estimate the motor speed using the back electromotive force of the motor, that is, to calculate using the following formula:

[0003]

[0004] where E is the back electromotive force of the motor, U is the voltage between two phases of the motor, I is the current flowing through the motor, R is the internal resistance of the motor winding, L is the inductance of the motor winding, represents the differential value of the motor current with respect to time.

[0005] Theoretically, the back electromotive force calculated in this way can represent the speed of the motor. However, during the actual operation of the motor, the temperature rise caused by the motor operation will cause changes in the internal resistance R and inductance L of the motor, resulting in inaccurate calculation of the back electromotive force of the motor. Therefore, temperature compensation is required.

[0006] The inability to accurately detect the speed leads to the inability to achieve good performance when starting on a ramp without slipping, and when going downhill, the motor cannot be completely stopped before locking the brake, and when parking uphill, the brake cannot be locked as soon as the motor stops.

[0007] Therefore, it is necessary to provide a sensorless ramp assist control method for a DC brushed motor to solve the above technical problems. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a sensorless ramp assist control method for a DC brushed motor.

[0009] The sensorless ramp assist control method for a DC brushed motor provided by the present invention specifically includes the following steps:

[0010] When the speed is not greater than 30 km / h, calculate the motor speed through the first motor model; when the speed is greater than 30 km / h, calculate the motor speed through the second motor model;

[0011] After obtaining the motor speed, perform speed closed-loop and current closed-loop control of the motor to improve the stability of vehicle parking and the starting efficiency of the vehicle;

[0012] The first motor model is

[0013] where E is the back electromotive force of the motor, U is the voltage between two phases of the motor, I is the current flowing through the motor, R is the internal resistance of the motor winding, L is the inductance of the motor winding, represents the differential value of the motor current with respect to time.

[0014] Preferably, the specific construction method of the second motor model is as follows:

[0015] S1. Sample the two-phase voltages Va and Vb of the motor, and calculate the speed based on the two-phase voltages Va and Vb to obtain the speed V1;

[0016] S2. Calculate the back electromotive force formula E of the motor according to the formula and calculate based on the back electromotive force formula E to obtain the speed V2;

[0017] S3. Install a speed encoder on the motor, and obtain the actual operating speed V3 of the motor through this encoder;

[0018] S4. Through multiple fittings of the collected corresponding data, the following calculation formula is finally obtained:

[0019] V3 = f(V1, V2);

[0020] S5. According to the above calculation formula, inversely deduce and construct the second motor model.

[0021] Preferably, the specific steps of sampling the two-phase voltages Va and Vb of the motor in S1 and calculating the speed based on the two-phase voltages Va and Vb to obtain the speed V1 are as follows:

[0022] S11. Sample back the two-phase voltages Va and Vb of the motor, and calculate the motor phase voltage Vab = Va - Vb;

[0023] S12. Perform a Fourier transform on Vab to obtain the frequency spectrum data of the motor phase voltage;

[0024] S13. Extract the frequency components from the frequency spectrum data of the motor phase voltage. Among them, the frequency of 14KHZ is the frequency of the motor PWM regulation, and the second frequency peak is the periodic signal caused by the voltage disturbance during the commutation of the motor;

[0025] S14. Calculate the operating speed V1 of the motor according to the periodic signal caused by the voltage disturbance during the commutation of the motor.

[0026] Preferably, the specific steps of performing a Fourier transform on Vab in S12 to obtain the frequency spectrum data of the motor phase voltage are as follows:

[0027] Calculate Vab at a sampling frequency of 1 KHZ and store 1024 consecutive data points simultaneously.

[0028] Perform FFT operation on these 1024 consecutive Vab data points to obtain the spectral data of the Vab data waveform.

[0029] Preferably, in S2, according to the formula The specific steps to calculate the back electromotive force E of the motor and calculate the speed V2 based on the back electromotive force E are as follows:

[0030] S21: Sample the two-phase voltages Va and Vb of the motor and calculate the motor phase voltage Vab = Va - Vb.

[0031] S22: Calculate the back electromotive force of the motor according to the formula where U can be taken as Vab, I is the sampled motor current, R is the internal resistance of the motor, and L is the inductance of the motor coil. Calculate the back electromotive force E of the motor in this way.

[0032] S23: Convert the calculated back electromotive force E of the motor to obtain the speed V2.

[0033] Preferably, the internal resistance R of the motor and the inductance L of the motor coil in the first motor model or S22 can be obtained by referring to the motor manual.

[0034] Preferably, the internal resistance R of the motor and the inductance L of the motor coil in the first motor model or S22 can be obtained by the following method, specifically:

[0035] Lock the electromagnetic brake of the motor and inject two high-frequency pulses into the motor in sequence, namely a pulse with a current of I1 and a time of t1, and a pulse with a current of I2 and a time of t2. Since the motor is locked, the motor cannot move, and the back electromotive force E of the motor is 0. Therefore, it can be obtained that:

[0036]

[0037] U1 and U2 can be obtained by sampling the voltage between the two phases of the motor through the circuit, and the specific values of the internal resistance R of the motor and the inductance L of the motor coil can be calculated through the above formula.

[0038] Compared with the related technology, a brushless DC motor sensorless ramp assist control method provided by the present invention has the following beneficial effects:

[0039] The present invention calculates the operating speed V1 of the motor by using the voltage fluctuation generated when the motor undergoes commutation through carbon brushes. At the same time, it combines the motor speed V2 calculated from the back electromotive force E of the motor, and obtains the actual operating speed V3 of the motor through a speed encoder. Finally, a constant f is obtained by performing multiple fittings on the data, so that the operating speed of the motor can be calculated without a speed encoder. The motor speed calculated by this method can effectively solve the influence of motor temperature rise on the calculation speed of the back electromotive force, and can also avoid the problem of inaccurate speed measurement caused by the fact that when the speed is slow, the waveform disturbance of carbon brush commutation is not obvious. Once the calculation formula is established, it is generally applicable to motors of the same specification, thereby better realizing the detection of speed. When parking downhill, the electromagnetic brake can be locked after the motor speed completely stops, which can effectively avoid the wear of the brake caused by the inertia of the motor. Brief Description of the Drawings

[0040] Figure 1 It is a schematic flow chart of a specific construction method for providing a second motor model according to the present invention. Detailed Embodiments

[0041] In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Generally, the components of the embodiments of the present invention described and illustrated in the drawings here can be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0043] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0044] In the description of the embodiments of the present invention, it should be noted that if terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invention product is usually placed during use. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, if terms such as "first", "second", "third", etc. are used only for distinguishing descriptions, they cannot be understood as indicating or implying relative importance.

[0045] In addition, if terms such as "horizontal", "vertical", "hanging" are used, it does not mean that the component is required to be absolutely horizontal or hanging, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and it does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0046] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "linked" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] The following describes the specific implementation of the present invention in detail with specific embodiments.

[0048] A sensorless ramp assist control method for a DC brushed motor provided by the present invention includes: when the speed is not greater than 30 km / h, calculating the motor speed through a first motor model; when the speed is greater than 30 km / h, calculating the motor speed through a second motor model.

[0049] After obtaining the motor speed, perform speed closed-loop and current closed-loop control of the motor to improve the stability of vehicle parking and the starting efficiency of the vehicle.

[0050] The first motor model is

[0051] where E is the back electromotive force of the motor, U is the voltage between two phases of the motor, I is the current flowing through the motor, R is the internal resistance of the motor winding, L is the inductance of the motor winding, represents the differential value of the motor current with respect to time.

[0052] In the embodiments of the present invention, refer toFigure 1 , the specific measurement method of the second motor model:

[0053] S1. Sample the two-phase voltages Va and Vb of the motor, and calculate the speed based on the two-phase voltages Va and Vb to obtain the speed V1;

[0054] S2. According to the formula calculate the back electromotive force formula E of the motor, and calculate based on the back electromotive force formula E to obtain the speed V2;

[0055] S3. Install a speed encoder on the motor, and obtain the actual operating speed V3 of the motor through this encoder;

[0056] S4. Through multiple fittings of the collected corresponding data, the following calculation formula is finally obtained: V3 = f(V1, V2);

[0057] S5. According to the above calculation formula, inversely deduce and construct the second motor model.

[0058] It should be noted that: the voltage fluctuation generated when the motor undergoes carbon brush commutation is used to calculate the operating speed V1 of the motor. At the same time, the motor speed V2 calculated in combination with the back electromotive force E of the motor is obtained through the speed encoder, and finally the constant f is obtained through multiple fittings of the data. The operating speed of the motor can be calculated without a speed encoder, and the motor speed calculated by this method can effectively solve the influence of motor temperature rise on the calculation speed of the back electromotive force, and can also avoid the problem of inaccurate speed measurement caused by the unclear disturbance of the carbon brush commutation waveform due to slow speed. Once the calculation formula is established, it is generally applicable to motors of the same specification, and thus better realizes the detection of speed. When parking downhill, the electromagnetic brake can be locked after the motor speed completely stops, which can effectively avoid the wear of the brake caused by the inertia of the motor.

[0059] In the embodiment of the present invention, the specific steps of sampling the two-phase voltages Va and Vb of the motor in S1 and calculating the speed based on the two-phase voltages Va and Vb to obtain the speed V1 are as follows:

[0060] S11. Sample back the two-phase voltages Va and Vb of the motor, and calculate the motor phase voltage Vab = Va - Vb;

[0061] S12. Perform Fourier transform on Vab to obtain the frequency spectrum data of the motor phase voltage;

[0062] S13. Extract the frequency components from the frequency spectrum data of the motor phase voltage. Among them, the frequency of 14KHZ is the frequency of the motor PWM regulation, and the second frequency peak is the periodic signal caused by the voltage disturbance during the commutation of the motor;

[0063] S14. Calculate the operating speed V1 of the motor based on the periodic signal caused by the voltage disturbance during motor commutation.

[0064] In the embodiment of the present invention, the specific steps for performing Fourier transform on Vab in S12 to obtain the spectrum data of the motor phase voltage are as follows:

[0065] Calculate Vab at a sampling frequency of 1 KHZ and simultaneously store 1024 consecutive data.

[0066] Perform FFT operation on these 1024 consecutive Vab data to obtain the spectrum data of the Vab data waveform.

[0067] In the embodiment of the present invention, according to the formula The specific steps for calculating the back electromotive force E of the motor and calculating the speed V2 based on the back electromotive force E are as follows:

[0068] S21. Sample the two-phase voltages Va and Vb of the motor and calculate the motor phase voltage Vab = Va - Vb.

[0069] S22. Calculate the back electromotive force of the motor according to the formula where U can take Vab, I is the motor current obtained by sampling, R is the motor internal resistance, and L is the motor coil inductance. Calculate the motor back electromotive force E in this way.

[0070] S23. Convert the calculated motor back electromotive force E to obtain the speed V2.

[0071] In the embodiment of the present invention, the first motor model or the motor internal resistance R and the motor coil inductance L in S22 can be obtained by referring to the motor manual.

[0072] In the embodiment of the present invention, the first motor model or the motor internal resistance R and the motor coil inductance L in S22 can be obtained by the following method, specifically:

[0073] Lock the electromagnetic brake of the motor and inject two high-frequency pulses into the motor in sequence, namely a pulse with a current of I1 and a time of t1, and a pulse with a current of I2 and a time of t2. And because the motor is locked, the motor cannot move, and the motor back electromotive force E = 0. Therefore, it can be obtained that:

[0074]

[0075] U1 and U2 can be obtained by sampling the voltage between the two phases of the motor through the circuit, and the specific values of the motor internal resistance R and the motor coil inductance L are calculated through the above formula.

[0076] The circuits and controls involved in the present invention are all prior arts and will not be elaborated here.

[0077] The above are only embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A sensorless ramp assist control method for a brushless DC motor, characterized in that: include: When the speed is not greater than 30 km / h, the motor speed is calculated by the first motor model; when the speed is greater than 30 km / h, the motor speed is calculated by the second motor model; After obtaining the motor speed, the motor speed closed-loop and current closed-loop control are performed to improve the parking stability and starting efficiency of the vehicle; The first motor model is Among them, E is the back electromotive force of the motor, U is the voltage between the two phases of the motor, I is the current flowing through the motor, R is the internal resistance of the motor winding, L is the inductance of the motor winding, Indicates the differential value of the motor current with respect to time; The specific construction method of the second motor model is as follows: S1, sampling the two-phase voltage Va, Vb of the motor, and calculating the speed according to the two-phase voltage Va, Vb to obtain the speed V1; S2, according to the formula Calculate the back electromotive force formula E of the motor, and calculate according to the back electromotive force formula E to obtain the speed V2; S3, a speed encoder is installed on the motor, and the actual running speed V3 of the motor is obtained through the encoder; S4. By fitting the collected corresponding data multiple times, the following calculation formula is finally obtained: V3=f(V1,V2) S5. According to the above calculation formula, reversely construct the second motor model.

2. The sensorless ramp assist control method of a brushed DC motor according to claim 1, characterized in that: In the S1, the two-phase voltages Va and Vb of the motor are sampled, and the speed is calculated according to the two-phase voltages Va and Vb to obtain the speed V1. The specific steps are: S11, sampling the two-phase voltage Va and Vb of the motor, and calculating the motor phase voltage Vab=Va-Vb; S12, performing Fourier transform on Vab to obtain frequency spectrum data of the motor phase voltage; S13, extracting frequency components from the spectrum data of the motor phase voltage, wherein the frequency of 14KHZ is the frequency of the motor PWM regulation, and the second high frequency point is the periodic signal caused by the voltage disturbance during the motor commutation; S14. Calculate the running speed V1 of the motor according to the periodic signal caused by the voltage disturbance during the motor commutation.

3. The sensorless ramp assist control method of a brushed DC motor according to claim 2, characterized in that: The specific steps of performing Fourier transform on Vab in S12 to obtain the frequency spectrum data of the motor phase voltage are as follows: Calculate Vab according to the sampling frequency of 1KHZ and store 1024 consecutive data at the same time; Perform FFT operation on the continuous 1024 Vab data to obtain the spectrum data of the Vab data waveform.

4. The sensorless ramp assist control method of a brushed DC motor according to claim 3, characterized in that: The S2 is based on the formula The specific steps of calculating the back electromotive force formula E of the motor and calculating according to the back electromotive force formula E to obtain the speed V2 are as follows: S21, sampling the two-phase voltages Va and Vb of the motor, and calculating the motor phase voltage Vab=Va-Vb; S22, according to the formula Calculate the back EMF of the motor, Where U can be Vab, I is the sampled motor current, R is the motor internal resistance, and L is the motor coil inductance. The motor back electromotive force E is calculated in this way; S23, convert the calculated motor back electromotive force E into speed V2.

5. The sensorless ramp assist control method of a brushed DC motor according to claim 4, characterized in that: The motor internal resistance R and the motor coil inductance L in the first motor model or S22 can be obtained by referring to the motor manual.

6. The sensorless ramp assist control method of a DC brushed motor according to claim 4, characterized in that: The motor internal resistance R and the motor coil inductance L in the first motor model or S22 can be obtained by the following method, specifically: By locking the electromagnetic brake of the motor, two high-frequency pulses are injected into the motor in sequence, one with a current of I1 and a time of t1, and one with a current of I2 and a time of t2. Because the motor is locked, the motor cannot move, and the motor back electromotive force E=0, so we can get: U1 and U2 can be obtained by sampling the voltage between the two phases of the motor through the circuit, and the specific values ​​of the motor internal resistance R and the motor coil inductance L can be calculated by the above formula.

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