Bridge arm dead time compensation method and motor output duty cycle capture circuit

Abstract

The application discloses a kind of bridge arm dead time compensation method, comprising: bridge arm dead time acquisition and calibration;Read current capture value;Obtain compensation deviation;Calculate compensation value;Read the duty cycle of each phase captured by MCU, the output of each phase at corresponding K-2 moment on the duty cycle obtained;Judge whether the duty cycle of each phase captured is zero;If it is zero, compensation is not needed;If it is not zero, subtract the PWM capture value of the phase K period from the PWM output value of the phase k-2 period saved, then add the specified compensation calibration correction value, to calculate the dead time compensation value of the phase;The PWM output value of the desired certain phase is added to the compensation deviation of the phase after measurement calibration to obtain the output value after compensation, and the maximum and minimum of the output value after compensation are limited according to the design rule.The present application realizes dead time compensation based on actual duty cycle back sampling to reduce the torque fluctuation of brushless motor, and can meet the torque fluctuation requirement of brushless motor control.

Description

Technical Field

[0001] The present invention relates to the automotive field, and in particular to a bridge arm dead time compensation method for reducing brushless motor torque fluctuations, and a motor output duty cycle capture circuit used in the bridge arm dead time compensation method. Background Art

[0002] The torque fluctuation of the brushless motor comes from the motor body and the electronic drive circuit. The output torque caused by the electronic drive circuit accounts for a non-negligible proportion when the system operates in the high frequency band and has a small torque output. In particular, the electromagnetic torque fluctuation caused by the dead time of the drive circuit bridge arm is an important source of system vibration and noise.

[0003] At present, the commonly used dead-zone compensation method performs indirect compensation based on the current polarity, which may cause erroneous compensation when the current is near the zero crossing point or when the current value is small. In order to reduce the impact of erroneous compensation, the common dead-zone compensation method switches according to the size of the current value. An important adverse effect is that additional fluctuations will be generated when the state switches.

[0004] Therefore, there is an urgent need for a method that can eliminate the influence of the inverter dead time without causing additional torque fluctuations due to misjudgment of current polarity. Summary of the Invention

[0005] The Summary of the Invention introduces a series of simplified concepts, which are simplifications of existing technologies in the field and are further described in detail in the Detailed Description of the Invention. The Summary of the Invention is not intended to define the key features and essential features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0006] The technical problem to be solved by the present invention is to provide a bridge arm dead time compensation method that realizes dead time compensation based on actual duty cycle recovery to reduce the torque fluctuation of the brushless motor and can meet the torque fluctuation requirements of the brushless motor control.

[0007] Furthermore, the present invention provides a motor output duty cycle capture circuit used in the bridge arm dead time compensation method.

[0008] In order to solve the above technical problems, the present invention provides a bridge arm dead time compensation method, comprising the following steps:

[0009] S1, bridge arm dead time acquisition and calibration;

[0010] S2, read the current capture value, read the duty cycle of each phase captured by the MCU, and obtain the duty cycle output value of each phase corresponding to the K-2 cycle;

[0011] S3, obtaining compensation deviation, calculating compensation deviation of each phase in current period K: subtracting PWM capture value of K period from saved PWM output value of k-2 period, and adding corresponding compensation calibration correction value;

[0012] S4, calculating compensation value, calculating PWM output value of each phase after compensation in K period: adding original PWM output value of each phase to compensation deviation of each phase;

[0013] S5, reading each phase duty cycle captured by MCU, and obtaining output of each phase duty cycle at K-2 time;

[0014] S6, judging whether captured each phase duty cycle is zero;

[0015] If it is zero, compensation is not needed;

[0016] If it is not zero, compensation calibration correction value is calculated by subtracting PWM capture value of K period from saved PWM output value of k-2 period of the phase, and adding specified compensation calibration correction value;

[0017] S7, adding PWM output value of a certain phase to measured compensation deviation of the phase to obtain compensated output value, and limiting maximum value and minimum value of compensated output value according to design requirement.

[0018] Optionally, the bridge arm dead time compensation method is further improved, and the method further comprises the following steps:

[0019] S8, recursively saving compensated output value of each phase for subsequent iteration calculation, and completing K period compensation.

[0020] Optionally, the bridge arm dead time compensation method is further improved, and step S1 comprises the following sub-steps:

[0021] S3.1, disconnecting ECU from motor, and connecting external signal source to ECU;

[0022] S3.2, opening electrical isolation switch, and providing multiple specified working conditions to obtain average value of captured value of each phase duty cycle in the same specified time for a specified number of times;

[0023] S3.2, calculating capture circuit deviation value.

[0024] Optionally, the bridge arm dead time compensation method is further improved, and the capture circuit deviation value is calculated by using the following formula (1);

[0025]

[0026] U phase duty cycle in step S3.2 under different specified working conditions

[0027] T Uduty_10act ,T Uduty_30act ,T Uduty_50act ,T Uduty_70act ,T Uduty_90act ;

[0028] V phase duty cycle under different specified working conditions in step S3.2

[0029] T Vduty_10act ,T Vduty_30act ,T Vduty_50act ,T Vduty_70act ,T Vduty_90act ;

[0030] The V-phase duty cycle and the W-phase duty cycle T under different specified working conditions in step S3.2 Wduty_10act ,T Wduty_30act ,T Wduty_50act ,T Wduty_70act ,T Wduty_90act .

[0031] Optionally, the bridge arm dead time compensation method may be further improved, wherein the plurality of specified working conditions include:

[0032] 12V, 20KHz, 10% duty cycle signal;

[0033] 12V, 20KHz, 30% duty cycle signal

[0034] 12V, 20KHz, 50% duty cycle signal;

[0035] 12V, 20KHz, 70% duty cycle signal;

[0036] 12V, 20KHz, 90% duty cycle signal.

[0037] Optionally, the bridge arm dead time compensation method can be further improved, wherein the specified time ranges from 0.5 seconds to 2 seconds, and the specified number of times ranges from 5 to 20 times. Preferably, the specified time is 1 second, and the specified number of times is 10 times.

[0038] To solve the above technical problems, the present invention provides a motor output duty cycle capture circuit, comprising:

[0039] The three-phase acquisition arm has the same structure and is connected to the three phases of the motor. Each phase acquisition arm includes:

[0040] An NMOS, a drain of which is connected to the power supply voltage VCC, a source and a gate of which are connected and connected to the power supply voltage VCC, a first end of the second resistor, a first end of the third resistor, and an input end of the PWM capture module;

[0041] A second resistor, a first end of which is connected to a phase of the motor and to an output end of the standard signal generating circuit through the first resistor, and a second end of which is connected to the power supply voltage VCC;

[0042] The third resistor has a second end connected to the power supply voltage VCC.

[0043] Optionally, the motor output duty cycle capture circuit is further improved, the first resistor and the third resistor of each three-phase collection arm have equal resistance, the second resistor of each three-phase collection arm has equal resistance, and the first resistor is greater than or equal to 2 times the second resistor.

[0044] Optionally, the motor output duty cycle capture circuit is further improved, the first resistor and the third resistor of each three-phase acquisition arm have a resistance range of 80000Ω-120000Ω, and the second resistor of each three-phase acquisition arm has a resistance range of 40000Ω-60000Ω.

[0045] This invention provides a bridge arm dead-time compensation method. This method simply adds a motor output duty cycle capture circuit consisting of conventional resistors and low-current switching transistors to the existing ECU motor drive structure. By improving the accuracy of the current sampling circuit and the motor structure solution compared to existing technologies, this method effectively reduces the hardware cost of the electronic controller and significantly reduces torque ripple, as well as the vibration and noise caused by torque ripple. This method achieves dead-time compensation based on actual duty cycle recovery, thereby reducing brushless motor torque ripple. This method can meet the torque ripple requirements of brushless motor control, significantly improving the user experience and taking product performance to a new level. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The drawings herein are intended to illustrate the general characteristics of methods, structures, and / or materials used in certain exemplary embodiments of the present invention, supplementing the descriptions in the specification. However, the drawings herein are schematic diagrams not drawn to scale and may not accurately reflect the precise structure or performance characteristics of any given embodiment. The drawings herein should not be interpreted as defining or limiting the range of values ​​or properties encompassed by the exemplary embodiments of the present invention. The present invention is further described in detail below in conjunction with the drawings and specific embodiments:

[0047] Figure 1 Figure 2 is a schematic diagram of the duty cycle capture calibration process.

[0048] Figure 2 FIG. 4 is a timing flow chart of duty cycle compensation. FIG. 4 is a timing flow chart of duty cycle compensation.

[0049] Figures 3 to 5 This is a schematic diagram of the dead time compensation for each phase.

[0050] Figure 6 This is the schematic diagram of the ECU motor drive circuit

[0051] Figure 7 It is a schematic diagram of the motor output duty cycle capture circuit of the present invention. DETAILED DESCRIPTION

[0052] The following describes the implementation manner of the present invention through specific specific embodiments. Those skilled in the art can fully understand other advantages and technical effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through different specific implementation manners, and the various details in this specification can also be applied based on different viewpoints, and various modifications or changes can be made without deviating from the overall design concept of the invention. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. The following exemplary embodiments of the present invention can be implemented in a variety of different forms and should not be interpreted as being limited to the specific embodiments described herein. It should be understood that these embodiments are provided to make the disclosure of the present invention thorough and complete, and to fully convey the technical solutions of these exemplary embodiments to those skilled in the art.

[0053] First embodiment;

[0054] The present invention provides a bridge arm dead time compensation method, comprising the following steps:

[0055] S1, bridge arm dead time acquisition and calibration;

[0056] S2, read the current capture value, read the duty cycle of each W phase captured by the MCU, and obtain the duty cycle output value of each phase corresponding to the K-2 period;

[0057] S3, obtain the compensation deviation and calculate the compensation deviation of each phase in the current cycle K: subtract the PWM capture value of the K cycle from the saved PWM output value of the k-2 cycle, and add the corresponding compensation calibration correction value;

[0058] S4, calculating the compensation value, calculating the PWM output value of each phase after K cycle compensation: by adding the compensation deviation of each phase to the original PWM output value of each phase;

[0059] S5, read the duty cycle of each phase captured by the MCU, and obtain the output of each phase at time K-2 corresponding to the duty cycle;

[0060] S6, determining whether the captured duty cycle of each phase is zero;

[0061] If it is zero, it means that there is no dead zone inserted in the current cycle of this phase and no compensation is required;

[0062] If it is not zero, the dead time compensation value of the phase is calculated by subtracting the PWM capture value of the phase K period from the saved PWM output value of the phase k-2 period, and adding the specified compensation calibration correction value;

[0063] S7, adding the measured and calibrated compensation deviation of a phase to the expected PWM output value of a certain phase to obtain a compensated output value, and limiting the maximum and minimum values ​​of the compensated output value according to design requirements.

[0064] Second embodiment;

[0065] refer to Figure 1 、 Figure 2 Combine Figure 3-Figure 5 As shown, the PWM pulse width modulation output of the ECU can only be executed in the next cycle, and the capture can only be achieved after the PWM is completed. The present invention provides a bridge arm dead time compensation method, comprising the following steps:

[0066] S1, bridge arm dead time acquisition and calibration;

[0067] S2, read the current capture value, read the U-phase duty cycle PWMU_CAP[K], V-phase duty cycle PWMV_CAP[K], and W-phase duty cycle PWMW_CAP[K] of the MCU capture module. The duty cycle obtained at this time corresponds to the output of the U-phase duty cycle PWMU[K-2], V-phase duty cycle PWMV[K-2], and W-phase duty cycle PWMW[K-2] at time K-2;

[0068] S3, obtain the compensation deviation and calculate the compensation deviation of the U, V and W phases of the current cycle K: subtract the PWM capture value of the K cycle obtained in the first step from the saved PWM output value of the k-2 cycle, and add the corresponding compensation calibration correction value;

[0069] S4, calculate the compensation value, calculate the U, V and W phase PWM output values ​​after K cycle compensation: This is achieved by adding the U, V and W phase compensation deviations obtained in S3 to the original U, V and W phase PWM output values;

[0070] S5, read the duty cycle of each phase captured by the MCU, and obtain the output of each phase at time K-2 corresponding to the duty cycle;

[0071] S6, determining whether the duty cycle of each phase of the captured period K is zero;

[0072] If the captured U-phase duty cycle PWMU_CAP[K], V-phase duty cycle PWMV_CAP[K], and W-phase duty cycle PWMW_CAP[K] are zero, if PWMU_CAP[K] is zero, it means that there is no switching action in the period, i.e. no insertion of dead time, and no compensation PWMUDuty_DTcom=0 is needed; if PWMV_CAP[K] is zero, it means that there is no switching action in the period, i.e. no insertion of dead time, and no compensation PWMVDuty_DTcom=0 is needed; if PWMW_CAP[K] is zero, it means that there is no switching action in the period, i.e. no insertion of dead time, and no compensation PWMWDuty_DTcom=0 is needed.

[0073] If the captured U-phase duty cycle PWMU_CAP[K] is not zero: subtract the PWM capture value PWMU_CAP[K] of the K period from the saved PWM output value PWMU[K-2] of the k-2 period, and add the corresponding compensation calibration value TUduty_offset_ave, to calculate the U-phase dead time compensation value PWMUDuty_DTcom; if the captured V-phase duty cycle PWMV_CAP[K] is not zero: subtract the PWM capture value PWMV_CAP[K] of the K period from the saved PWM output value PWMV[K-2] of the k-2 period, and add the corresponding compensation calibration value TVduty_offset_ave, to calculate the V-phase dead time compensation value PWMVDuty_DTcom; if the captured W-phase duty cycle PWMW_CAP[K] is not zero: subtract the PWM capture value PWMW_CAP[K] of the K period from the saved PWM output value PWMW[K-2] of the k-2 period, and add the corresponding compensation calibration value TWduty_offset_ave, to calculate the W-phase dead time compensation value PWMWDuty_DTcom.

[0074] S7, add the expected U-phase PWM output value PWMU[K] to the U-phase compensation PWMUDuty_DTcom after measurement and calibration to obtain PWMU_aftercom[K], and limit the maximum and minimum values ​​of PWMU_aftercom[K]. K-period output value after V-phase dead zone compensation: add the expected V-phase PWM output value PWMV[K] to the V-phase compensation PWMVDuty_DTcom after measurement and calibration to obtain PWMV_aftercom[K], and limit the maximum and minimum values ​​of PWMV_aftercom[K]. K-period output value after W-phase dead zone compensation: add the expected W-phase PWM output value PWMW[K] to the V-phase compensation PWMWDuty_DTcom after measurement and calibration to obtain PWMW_aftercom[K], and limit the maximum and minimum values ​​of PWMW_aftercom[K].

[0075] S8, recursively save the compensated output values ​​of each phase for subsequent iterative calculation to complete K-cycle compensation.

[0076] Wherein, step S1 includes the following sub-steps:

[0077] S3.1, disconnect the ECU from the motor and connect the external signal source to the ECU;

[0078] S3.2, open the electrical isolation switch, provide multiple specified working conditions, take the middle specified number of capture values ​​within the same specified time, and average them to obtain the duty cycle of each phase;

[0079] Turn on the electrical isolation switch, pass a 12V, 20KHz, 10% duty cycle signal, test for 0.5 seconds to 2 seconds, take the average of the middle 5 to 20 capture values ​​to get the U phase duty cycle T Uduty_10act ,V phase duty cycle T Vduty_10act ,W phase duty cycle T Wduty_10act ;

[0080] Turn on the electrical isolation switch, pass a 12V, 20KHz, 30% duty cycle signal, test for 0.5 seconds to 2 seconds, take the average of the middle 5 to 20 capture values ​​and calculate T Uduty_30act ,T Vduty_30act ,T Wduty_30act ;

[0081] Turn on the electrical isolation switch, pass a 12V, 20KHz, 50% duty cycle signal, test for 0.5 seconds to 2 seconds, take the average of the middle 5 to 20 capture values ​​and calculate T Uduty_50act ,T Vduty_50act ,T Wduty_50act ;

[0082] Turn on the electrical isolation switch, pass a 12V, 20KHz, 70% duty cycle signal, test for 0.5 seconds to 2 seconds, take the average of the middle 5 to 20 capture values ​​and calculate the T Uduty_70act ,T Vduty_70act ,T Wduty_70act ;

[0083] Turn on the electrical isolation switch, pass a 12V, 20KHz, 90% duty cycle signal, test for 0.5 seconds to 2 seconds, take the average of the middle 5 to 20 capture values ​​and calculate T Uduty_90act ,T Vduty_90act ,T Wduty_90act ;

[0084] S3.2, calculate the capture circuit deviation value. The capture circuit deviation value is calculated using the following formula (1) to obtain the capture circuit deviation value T Uduty_offset_ave ,T Vduty_offset_ave ,T Wduty_offset_ave , used for subsequent dead time calibration;

[0085]

[0086] U phase duty cycle under different specified working conditions in step S3.2

[0087] T Uduty_10act ,T Uduty_30act ,T Uduty_50act ,T Uduty_70act ,T Uduty_90act ;

[0088] V phase duty cycle under different specified working conditions in step S3.2

[0089] T Vduty_10act ,T Vduty_30act ,T Vduty_50act ,T Vduty_70act ,T Vduty_90act ;

[0090] W phase duty cycle under different specified working conditions in step S3.2

[0091] T Wduty_10act ,T Wduty_30act ,T Wduty_50act ,T Wduty_70act ,T Wduty_90act .

[0092] In addition, it should be understood that, although the terms "first," "second," etc. may be used herein to describe different elements, parameters, components, regions, layers, and / or parts, these elements, parameters, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, parameter, component, region, layer, or part from another element, parameter, component, region, layer, or part. Therefore, without departing from the teachings of exemplary embodiments of the present invention, the first element, parameter, component, region, layer, or part discussed below may also be referred to as a second element, parameter, component, region, layer, or part.

[0093] Third embodiment;

[0094] refer to Figure 7 As shown, the present invention provides a motor output duty cycle capture circuit that can be used in the above embodiment, including:

[0095] The three-phase acquisition arm has the same structure and is connected to the three phases of the motor. Each phase acquisition arm includes:

[0096] An NMOS, a drain of which is connected to the power supply voltage VCC, a source of which is connected to the first end of the third resistor and an input end of the PWM capture module, and a gate of which is connected to the first end of the second resistor;

[0097] a second resistor, a first end of which is connected to a phase of the motor and to an output end of the standard signal generating circuit via the first resistor, and a second end of which is connected to the power supply voltage GND;

[0098] a third resistor, a second end of which is connected to the power supply voltage GND;

[0099] The first resistor and the third resistor of each three-phase collection arm have equal resistance values, the second resistor of each three-phase collection arm has equal resistance values, and the first resistor has a resistance value greater than or equal to 2 times the second resistor has a resistance value.

[0100] The resistance parameters are: the first resistor R 1U 、R 1V and R 1W Equal to the third resistor R 3U 、R 3V and R 3W =100000Ω, the second resistor R 2U 、R 2V and R 2W =50000Ω, Figure 7 The motor terminal voltage can be converted into a voltage that can be collected by the MCU: PWMU_Fb, PWMV_Fb, PWMW_Fb.

[0101] According to formula (1), the capture circuit deviation value T is obtained Uduty_offset_ave =300nS,TVduty_offset_ave = 300 nS, T Wduty_offset_ave = 300 nS, for later dead time calibration.

[0102] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0103] The application has been described in detail by specific reference to implementations and embodiments. These particular implementations and embodiments are not intended to limit the scope of the application, which is defined with the following claims. Many variations and modifications of the application can be made without departing from the spirit and scope of the application, and specific reference should not be made to any one of the included examples.

Claims

1. A bridge arm dead time compensation method, characterized in that: The following steps are involved: S1, bridge arm dead time acquisition and calibration; S2, read the current capture value, read the duty cycle of each phase captured by the MCU, and obtain the duty cycle output value of each phase corresponding to the K-2 cycle; S3, obtain the compensation deviation and calculate the compensation deviation of each phase in the current cycle K: subtract the PWM capture value of the K cycle from the saved PWM output value of the k-2 cycle, and add the corresponding compensation calibration correction value, including: S3.1, disconnect the ECU from the motor and connect the external signal source to the ECU; S3.2, open the electrical isolation switch, provide multiple specified working conditions, take the middle specified number of capture values ​​within the same specified time, and average them to obtain the duty cycle of each phase; S3.2, calculate the capture circuit deviation value using the following formula (1); ； U-phase duty cycle TUduty_10act, TUduty_30act, TUduty_50act, TUduty_70act, TUduty_90act under different specified working conditions; V-phase duty cycle TVduty_10act, TVduty_30act, TVduty_50act, TVduty_70act, TVduty_90act under different specified working conditions; W phase duty cycle under different specified working conditions is TWduty_10act, TWduty_30act, TWduty_50act, TWduty_70act, TWduty_90act; S4, calculating the compensation value, calculating the PWM output value of each phase after K cycle compensation: by adding the compensation deviation of each phase to the original PWM output value of each phase; S5, read the duty cycle of each phase captured by the MCU, and output the duty cycle of each phase at the K-2 moment corresponding to the duty cycle obtained; S6, determining whether the captured duty cycle of each phase is zero; If it is zero, no compensation is required; If it is not zero, the dead time compensation value of the phase is calculated by subtracting the PWM capture value of the phase K period from the saved PWM output value of the phase k-2 period, and adding the specified compensation calibration correction value; S7, adding the measured and calibrated compensation deviation of a phase to the expected PWM output value of a certain phase to obtain a compensated output value, and limiting the maximum and minimum values ​​of the compensated output value according to design requirements.

2. The bridge arm dead time compensation method according to claim 1, wherein: The following steps are also included: S8, recursively save the compensated output values ​​of each phase for subsequent iterative calculation to complete K-cycle compensation.

3. The bridge arm dead time compensation method according to claim 1, wherein: The multiple specified working conditions include: 12V, 20KHz, 10% duty cycle signal; 12V, 20KHz, 30% duty cycle signal 12V, 20KHz, 50% duty cycle signal; 12V, 20KHz, 70% duty cycle signal; 12V, 20KHz, 90% duty cycle signal.

4. The bridge arm dead time compensation method according to claim 1, wherein: The range of the specified time is 0.5 seconds to 2 seconds, and the range of the specified number of times is 5 times to 20 times.

5. A motor output duty cycle capture circuit, applying the bridge arm dead time compensation method according to any one of claims 1 to 4, characterized in that: include: The three-phase acquisition arm has the same structure and is connected to the three phases of the motor. Each phase acquisition arm includes: An NMOS, a drain of which is connected to the power supply voltage VCC, a source of which is connected to the first end of the third resistor and an input end of the PWM capture module, and a gate of which is connected to the first end of the second resistor; a second resistor, a first end of which is connected to a phase of the motor and to an output end of the standard signal generating circuit via the first resistor, and a second end of which is connected to the power supply voltage GND; The third resistor has a second end connected to the power supply voltage GND.

6. The motor output duty cycle capture circuit according to claim 5, wherein: The first resistor and the third resistor of each three-phase collection arm have equal resistance values, the second resistor of each three-phase collection arm has equal resistance values, and the first resistor has a resistance value greater than or equal to 2 times the second resistor has a resistance value.

7. The motor output duty cycle capture circuit according to claim 6, wherein: The resistance range of the first resistor and the third resistor of each three-phase collection arm is 80000Ω-120000Ω, and the resistance range of the second resistor of each three-phase collection arm is 40000Ω-60000Ω.

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