Automobile air conditioner servo motor driving method based on real-time self-calibration

Abstract

The invention discloses an automobile air conditioner servo motor driving method based on real-time self-calibration, and the method comprises the steps: employing a half-bridge driving chip to drive and control a servo motor, and enabling an input end of the half-bridge driving chip to be connected with an upper computer control signal; the output end of the half-bridge driving chip is connected to the servo motor; the half-bridge driving chip comprises a half-bridge structure composed of two MOSFETs, one MOSFET is responsible for providing forward current to the servo motor, the other MOSFET is responsible for providing reverse current to the servo motor, and the on and off of the MOSFETs are controlled through an upper computer control signal to control the forward rotation, reverse rotation and braking of the motor. The method has the advantages that the precision of the motor is controlled as much as possible on the basis of reducing the cost, and the reliability and precision of servo motor control can be improved.

Description

Technical Field

[0001] The invention relates to the field of driving control of a servo motor in an automobile air conditioner, and in particular to a method for driving the servo motor of the automobile air conditioner based on real-time self-calibration. Background Art

[0002] The mode damper, temperature damper, circulation damper, etc. of the car air conditioner need to be driven and controlled by the drive motor. Usually, the drive mode of the servo motor is the PWM (pulse width modulation) duty cycle output adjustment mode. The PWM duty cycle output adjustment mode adjusts the speed and position of the servo motor by changing the duty cycle of the PWM signal.

[0003] During the driving process, the controller generates a PWM signal and inputs it into the driver. The driver controls the current and torque output of the servo motor according to the duty cycle of the PWM signal. The higher the duty cycle, the greater the output current and torque; the lower the duty cycle, the smaller the output current and torque. By continuously adjusting the duty cycle of the PWM signal, precise control of the servo motor speed and position can be achieved.

[0004] In order to meet the comfort requirements of the vehicle passenger compartment, automobile air conditioners usually require 3 to 8 damper motors to switch the blowing direction. Due to the position feedback characteristics of servo motors, there are more applications in automobile air conditioners on the market. In order to achieve precise control accuracy (±0.05V), PWM duty cycle adjustment control with PID adjustment algorithm is usually adopted. Due to the requirements for PWM duty cycle, it is necessary to occupy precious MCU resources. At a time when the integration of automotive electronics is getting higher and higher, this method has caused a considerable burden on the integrated module. In addition, the driver chip that supports PWM duty cycle adjustment is more expensive and requires more MCU resources, which also increases the cost of the whole vehicle. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a car air-conditioning servo motor driving method based on real-time self-calibration, which can control the accuracy of the motor as much as possible on the basis of reducing costs, thereby improving the reliability and accuracy of servo motor control.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a car air-conditioning servo motor driving method based on real-time self-calibration, using a half-bridge driver chip to drive and control the servo motor, the input end of the half-bridge driver chip is connected to the host computer control signal; the output end of the half-bridge driver chip is connected to the servo motor; the half-bridge driver chip includes a half-bridge structure composed of two MOSFETs, one of which is responsible for providing forward current to the servo motor, and the other is responsible for providing reverse current to the servo motor, and the conduction and cutoff of the MOSFET are controlled by the host computer control signal to control the forward rotation, reverse rotation and braking of the motor.

[0007] The real-time position signal of the servo motor is monitored by the position sensor. When the servo motor is position controlled, the inertia offset is used to control the servo motor. When the distance from the target position reaches the inertia offset, the driving motor is stopped, so that the motor reaches the target position through the inertia offset under inertia.

[0008] Each time the motor is controlled, the difference between the actual position and the target position reached by the motor after the motor control is stopped is collected in real time, and the difference is stored as the inertia offset. The next time the motor is driven and controlled, the drive is stopped when the motor is away from the target position by the inertia offset.

[0009] Each time the servo motor is started for control, it is first checked whether there is a stored inertia offset value. If not, the servo motor is directly controlled until a signal of reaching the target position is obtained from the servo motor, and then the control of the servo motor is stopped. In this process, the inertia offset is statistically calculated and stored. If the stored inertia offset is queried, when the motor is controlled, when the distance from the target position reaches the inertia offset, the control of the motor is stopped, and the motor is allowed to stop according to inertia to reach the target position.

[0010] The inertia offset value range is preset. When the last stored inertia offset queried each time exceeds the value range, the default value is used as a temporary inertia offset to control the servo motor. The default value is one of the values ​​within the value range.

[0011] Each time the motor is controlled, the distance between the inertia position where the motor stops due to inertia and the target position is calculated. When the distance is less than the set threshold, it means that the accuracy of the motor early stop control using the inertia offset meets the requirements. Otherwise, it means that the accuracy does not meet the requirements. At this time, the inertia offset calculated in the current servo motor control process is corrected.

[0012] When correcting the inertia offset, first determine whether the servo motor stops when the target position is not reached or when the target position is exceeded. When the target position is not reached, a correction value is added to the inertia offset calculated this time, and the result is stored and called next time. When the target position is exceeded, a correction value is subtracted from the inertia offset calculated this time, and the result is stored and called next time.

[0013] The correction value is a pre-calibrated setting, and its value is smaller than the difference between the maximum and minimum values ​​in the inertia offset value range.

[0014] The servo motor has a built-in position sensor and feeds back the position information value to the host computer in real time. The host computer controls the half-bridge driver chip based on the feedback information.

[0015] The advantages of the present invention are: the accuracy of the motor can be controlled as much as possible on the basis of reducing costs, and the reliability and accuracy of the servo motor control can be improved. Since the half-bridge chip is used for drive control, the cost is lower. In order to improve the accuracy, the inertia offset error calibrated in real time is used to control the motor, which improves the accuracy and enables the user to control the air conditioner damper, while reducing the cost as much as possible, thus reducing costs and increasing efficiency, and reducing the cost of the whole vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The following is a brief description of the contents expressed in the drawings of the present invention and the symbols in the drawings:

[0017] Figure 1 This is a flow chart of the control method of the present invention;

[0018] Figure 2 Schematic diagram of the system architecture involved in the control method of the present invention. DETAILED DESCRIPTION

[0019] The specific implementation of the present invention will be further explained in detail below by describing the optimal embodiment with reference to the accompanying drawings.

[0020] In this embodiment, this scheme adopts two main improvements: the first improvement is to use a half-bridge driver chip to save costs and reduce MCU resources to realize the drive control of the servo motor in the air conditioner. The second aspect is to improve the control accuracy by improving the control strategy to control the action of the motor and improve the control accuracy. The valve stem is summarized as follows: In this scheme, a half-bridge high and low level drive is selected, and self-calibration is used to achieve a more accurate and higher precision stop position of the motor. The working principle of the half-bridge chip is realized by a half-bridge structure composed of two MOSFETs (metal oxide semiconductor field effect transistors). One MOSFET is responsible for providing forward current, and the other is responsible for providing reverse current. By changing the conduction and cutoff of the MOSFET, the power supply of the motor can be controlled, thereby realizing the forward, reverse and braking of the motor. Self-calibration refers to the collection of the motor feedback voltage. When the motor is driven to the target position, the actual position and the target position are compared to calculate the difference. The difference is the advance amount that the motor needs to stop in advance when it is about to reach the target position when the next drive. Thereby improving the accuracy of the motor stopping at the target position. And the selected driver chip only needs to be a SPI-driven half-bridge chip. In this way, the chip can not only be used to drive the servo motor but also can be used for other HSD / LSD controls. This increases the multiple functions of the chip and fully utilizes the resources. The cost of the half-bridge chip is also lower than that of the PWM driver chip.

[0021] like Figure 1 , 2 As shown, a method for driving a servo motor of an automobile air conditioner based on real-time self-calibration adopts a half-bridge driver chip to drive and control the servo motor, and the input end of the half-bridge driver chip is connected to the host computer control signal; the output end of the half-bridge driver chip is connected to the servo motor; the half-bridge driver chip includes a half-bridge structure composed of two MOSFETs, one of which is responsible for providing a forward current to the servo motor, and the other is responsible for providing a reverse current to the servo motor, and the conduction and cutoff of the MOSFET are controlled by the host computer control signal to control the forward rotation, reverse rotation and braking of the motor. Forward rotation controls the MOSFET of the forward current to work, reverse rotation controls the MOSFET of the reverse current to work, and braking controls both MOSFETs to stop working and be in the cutoff state. Since a half-bridge chip with two MOSFETs is used to drive the motor, the cost is low and does not require a large MCU resource, thereby saving costs.

[0022] In order to improve the accuracy of control, the real-time position signal of the servo motor is monitored by a position sensor. When the servo motor is position controlled, the inertia offset is used to control the servo motor to stop driving the motor when the distance from the target position reaches the inertia offset, so that the motor reaches the target position through the inertia offset under inertia. The position sensor can use a Hall sensor or an encoder to obtain the position signal of the motor, and the motor is controlled based on the position signal of the motor. In order to control the motor more accurately, the concept of inertia offset is cited in this scheme.

[0023] like Figure 2 As shown, in this solution, the servo motor is equipped with a position sensor and real-time feedback of the position information value is sent to the host computer, which controls the half-bridge driver chip according to the feedback information. The host computer outputs a control signal to the half-bridge driver chip according to the user's control signal for the damper motor, which is used to drive the working state of the two MOSFETs of the half-bridge driver chip, thereby realizing the control of the forward and reverse rotation and stop of the motor. The host computer is provided with a memory, which is used to store the inertia offset corresponding to the motor calculated by the host computer each time the motor is controlled.

[0024] Inertia offset refers to the position movement data generated by the motor's inertia after the motor's half-bridge driver chip stops outputting the drive signal. Each time the motor is controlled, the difference between the actual position and the target position reached by the motor after the motor control is stopped is collected in real time, and the difference is stored as the inertia offset. The next time the motor is driven and controlled, the drive is stopped when the motor is away from the target position by the inertia offset, and the motor is allowed to move to the target position according to inertia. In this way, the motor can reach the target position more accurately, rather than stopping when it reaches the target position. If it stops when it reaches the target position, the position finally reached by the motor will exceed the target position due to inertia.

[0025] The inertia offset calculated each time is stored in the memory, which is convenient for direct reading and calling when used. Each time the servo motor is started to be controlled, first check whether there is an inertia offset value stored. If not, the servo motor is directly controlled until the signal of reaching the target position is obtained from the servo motor feedback, and then the control of the servo motor is stopped. In this process, the inertia offset is statistically calculated and stored; if the stored inertia offset is queried, when the motor is controlled, when the distance from the target position reaches the inertia offset, the motor is stopped from being controlled, and the motor is allowed to stop according to inertia to reach the target position; in this process, the inertia offset is statistically calculated and the stored inertia offset value is updated. Since the inertia offset is calculated each time the motor is reversed, the inertia offset can be switched in real time, thereby achieving more accurate control.

[0026] In order to avoid the inertia offset error caused by calculation, the inertia offset value range is pre-set. When the last stored inertia offset stored each time is out of the value range, the default value is used as a temporary inertia offset to control the servo motor. The default value is one of the values ​​in the value range, which can be set by calibration. When the inertia offset does not exceed the set value range, the read inertia offset is directly used to control the stop of the motor. The power supply control of the motor is stopped before the motor reaches the set target position, so that it runs to the target position according to inertia. The target position is set by the user and transmitted to the host computer, which drives and controls the half-bridge chip.

[0027] Since calculations can produce errors, each time the motor stops and is in a stationary state, each time the motor is controlled, the distance between the final position where the motor stops due to inertia, that is, the inertia position and the target position set by the user is calculated. This distance is used to evaluate whether there is a large gap between the running position of the motor and the target position. When the distance is less than the set threshold, it means that the accuracy of the motor early stop control using the inertia offset meets the requirements, and the calculated inertia offset is directly stored for the next use. Otherwise, it means that the accuracy does not meet the requirements, and the inertia offset calculated during the current servo motor control process is corrected.

[0028] When correcting the inertia offset, first determine whether the servo motor stops for not reaching the target position or exceeding the target position; when the target position is not reached, a correction value is added to the inertia offset calculated this time, and then stored and called for the next time; when the target position is exceeded, a correction value is subtracted from the inertia offset calculated this time, and then stored and called for the next time. The correction value is a pre-calibrated setting, and its value is less than the difference between the maximum and minimum values ​​in the inertia offset value range. The correction value is used to modify whether each calculated offset is stored in the memory for the next use, which can improve the accuracy of control.

[0029] The strategy of the present invention is based on the half-bridge drive controlled by SPI. Since the damper motor itself has inertia characteristics, when the target position is given, the motor needs a certain amount of time to change its own state, including acceleration, deceleration or stopping. In this process, the difference between the target position and the actual position will appear. This strategy will calculate the inertia offset that exists after the motor executes the forward and reverse instructions to reach the target position each time. The next time the motor is driven, the drive will be stopped when there is still an inertia offset from the target position, so that it will eventually stop at the target position due to inertia. Thereby achieving accurate driving to the target position. The half-bridge driven servo motor plus the self-calibration algorithm can not only achieve extremely small errors in accuracy, but also reduce the cost budget of the driver chip compared to the PWM duty cycle drive, and can also be used as the output of other LSD / HSD to effectively improve resource utilization and avoid resource waste. No matter how many damper motors there are, only a reusable SPI communication bus control is required, which greatly reduces the MCU resource occupation. In the actual environment, when the motor has been used for a long time and has large deviations due to aging, insufficient lubrication, etc., the real-time inertia offset compensation can also ensure that the motor's accuracy can be maintained within ±0.05V at the next action when the deviation occurs in a bad environment.

[0030] Obviously, the specific implementation of the present invention is not limited to the above-mentioned methods. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, they are all within the protection scope of the present invention.

Claims

1. A method for driving a servo motor of an automobile air conditioner based on real-time self-calibration, characterized in that: A half-bridge driver chip is used to drive and control the servo motor, and the input end of the half-bridge driver chip is connected to the host computer control signal; the output end of the half-bridge driver chip is connected to the servo motor; the half-bridge driver chip includes a half-bridge structure composed of two MOSFETs, one of which is responsible for providing forward current to the servo motor, and the other is responsible for providing reverse current to the servo motor. The conduction and cutoff of the MOSFET are controlled by the host computer control signal to control the forward rotation, reverse rotation and braking of the motor.

2. The method for driving an automobile air-conditioning servo motor based on real-time self-calibration according to claim 1, characterized in that: The real-time position signal of the servo motor is monitored by the position sensor. When the servo motor is position controlled, the inertia offset is used to control the servo motor. When the distance from the target position reaches the inertia offset, the driving motor is stopped, so that the motor reaches the target position through the inertia offset under inertia.

3. The method for driving an automobile air-conditioning servo motor based on real-time self-calibration according to claim 2, characterized in that: Each time the motor is controlled, the difference between the actual position and the target position reached by the motor after the motor control is stopped is collected in real time, and the difference is stored as the inertia offset. The next time the motor is driven and controlled, the drive is stopped when the motor is away from the target position by the inertia offset.

4. A method for driving a servo motor of an automobile air conditioner based on real-time self-calibration as claimed in claim 2 or 3, characterized in that: Each time the servo motor is started for control, it is first checked whether there is a stored inertia offset value. If not, the servo motor is directly controlled until a signal of reaching the target position is obtained from the servo motor, and then the control of the servo motor is stopped. In this process, the inertia offset is statistically calculated and stored. If the stored inertia offset is queried, when the motor is controlled, when the distance from the target position reaches the inertia offset, the control of the motor is stopped, and the motor is allowed to stop according to inertia to reach the target position.

5. The method for driving a servo motor of an automobile air conditioner based on real-time self-calibration according to claim 4, characterized in that: The inertia offset value range is preset. When the last stored inertia offset queried each time exceeds the value range, the default value is used as a temporary inertia offset to control the servo motor. The default value is one of the values ​​within the value range.

6. A method for driving a servo motor of an automobile air conditioner based on real-time self-calibration according to any one of claims 1 to 5, characterized in that: Each time the motor is controlled, the distance between the inertia position where the motor stops due to inertia and the target position is calculated. When the distance is less than the set threshold, it means that the accuracy of the motor early stop control using the inertia offset meets the requirements. Otherwise, it means that the accuracy does not meet the requirements. At this time, the inertia offset calculated in the current servo motor control process is corrected.

7. The method for driving a servo motor of an automobile air conditioner based on real-time self-calibration according to claim 6, characterized in that: When correcting the inertia offset, first determine whether the servo motor stops when the target position is not reached or when the target position is exceeded; if the target position is not reached, add a correction value to the inertia offset calculated this time and store it for the next call; When the target position is exceeded, the inertia offset calculated this time is subtracted by a correction value and stored for the next call.

8. The method for driving a servo motor of an automobile air conditioner based on real-time self-calibration according to claim 7, characterized in that: The correction value is a pre-calibrated setting, and its value is smaller than the difference between the maximum and minimum values ​​in the inertia offset value range.

9. A method for driving a servo motor of an automobile air conditioner based on real-time self-calibration according to any one of claims 1 to 8, characterized in that: The servo motor has a built-in position sensor and feeds back the position information value to the host computer in real time. The host computer controls the half-bridge driver chip based on the feedback information.

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