Motor control device

Abstract

To provide a technique capable of controlling a brushless motor in a spark advance without using a current detection part with high accuracy.SOLUTION: A motor control device according to an embodiment of the present disclosure, comprises: a control part 40; a rotational number detection part 12; a voltage detection part 50; a current detection part 60; and a current determination part 40. A lowest current value that can be used as a motor current value detected by the current detection part is set as a predetermined value. The control part sets a spark advance value for controlling a brushless motor in a spark advance on the basis of a load estimated by a power supply voltage value detected by the voltage detection part, a rotational number detected by the rotational number detection part, and a duty ratio that performs a PWM control of the brushless motor by the control part when the current determination part determines that the motor current value is smaller than a predetermined value, and sets the spark advance value on the basis of the motor current value, the power supply voltage value, the rotational number when the current determination part determines that the motor current value is the predetermined value or larger.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a technique for controlling the rotation of a brushless motor. [Background technology]

[0002] In a brushless motor, advance control is performed to advance the timing of energization of the stator coil in order to suppress vibration and noise. In the technology described in the following Patent Document 1, a drive torque is calculated from a motor current value, a power supply voltage value, and an actual rotation speed of the motor, and a reference rotation speed corresponding to the calculated drive torque is obtained. Then, a lead angle value of the motor is determined based on the difference between the reference rotation speed and the actual rotation speed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-156176 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Patent Document 1, the motor current value is used to determine the lead angle value regardless of the magnitude of the motor current value. However, when the detected current value is small, applying the lower limit of the error range allowed by the current detection unit that detects the current value may cause the positive and negative of the current value to be reversed. Lead angle control cannot be performed based on the detected current value, which may have a reversed positive and negative sign.

[0005] Even when the detected current value is small, the error range needs to be made small in order to prevent the positive and negative signs of the current value from being reversed by applying the lower limit of the error range. However, as a result of detailed consideration by the inventors, it was found that in order to reduce the error range, a current detection section with high detection accuracy is required.

[0006] One aspect of the present disclosure is to provide a technique for controlling the advance angle of a brushless motor without using a highly accurate current detection unit. [Means for solving the problem]

[0007] A motor control device according to one aspect of the present disclosure includes a control unit (40, S404 to S412), a rotation speed detection unit (12), a voltage detection unit (50), a current detection unit (60), and a current determination unit (40, S402).

[0008] The control unit controls the rotation of the brushless motor. The rotation speed detection unit detects the rotation speed of the brushless motor. The voltage detection unit detects the power supply voltage value of the brushless motor. The current detection unit detects the motor current value flowing through the brushless motor. The minimum current value that can be used as the motor current value detected by the current detection unit is set as a predetermined value, and the current determination unit determines whether the motor current value is greater than the predetermined value.

[0009] When the current determination unit determines that the motor current value is smaller than a predetermined value, the control unit sets a lead-angle value for advance-angle control of the brushless motor based on a load estimated from the power supply voltage value detected by the voltage detection unit, the rotation speed detected by the rotation speed detection unit, and the duty ratio with which the control unit PWM controls the brushless motor, and when the current determination unit determines that the motor current value is greater than or equal to the predetermined value, sets a lead-angle value based on the motor current value, the power supply voltage value, and the rotation speed.

[0010] With this configuration, even if the current detection unit is not highly accurate, when the detected motor current value is equal to or greater than a predetermined value, it is equal to or greater than the minimum current value that can be used as the motor current value, so the lead angle value can be set using the motor current value detected by the current detection unit.

[0011] On the other hand, when the motor current value detected by the current detection unit is smaller than the predetermined value, the lead angle value is set without using the motor current value detected by the current detection unit. Therefore, the advance angle of the brushless motor can be controlled without using a highly accurate current detector. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram showing a motor control system. [Diagram 2] FIG. [Diagram 3] 4 is a flowchart showing a motor control process. [Figure 4] FIG. 4 is a characteristic diagram showing PWM duty characteristics at maximum load and at no load. [Diagram 5] FIG. 4 is a characteristic diagram showing advance characteristics at maximum load and at no load. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. [1. Configuration] A brushless motor 2 shown in FIG. 1 is used, for example, as a blower motor for a vehicle air conditioner, and is rotationally driven by three-phase driving power having U-phase, V-phase, and W-phase.

[0014] The motor control device 10 controls the rotation of the brushless motor 2 by controlling the three-phase driving power supplied to the brushless motor 2 . The motor control device 10 includes a Hall IC 12, an inverter 20, a pre-driver 30, a microcomputer 40, a voltage detector 50, and a current detector 60. Note that microcomputer is an abbreviation for microcomputer.

[0015] The Hall IC 12 is installed in the motor control device 10 to detect the magnetic pole position of a rotor (not shown) of the brushless motor 2, i.e., the rotational position of the rotor. The Hall IC 12 includes a Hall element and a circuit for processing the output voltage of the Hall element.

[0016] The inverter 20 is configured, for example, by providing pairs of series circuits of two switching elements provided at both ends of the power supply voltage 6, one for each phase of a three-phase stator coil, that is, U phase, V phase, and W phase. In each pair of two switching elements, a terminal of each phase of the brushless motor 2 is connected to a connection point between the switching elements.

[0017] By changing the on / off combination of the two switching elements in each phase, it is possible to change whether or not a current flows through the coil of that phase, and the direction of the current. The pre-driver 30 generates a drive signal for switching the switching elements of each phase of the inverter 20 based on the duty ratio of the PWM signal representing the speed command value output from the microcomputer 40. Furthermore, the pre-driver 30 advances the output timing of the drive signal based on the advance angle command value output from the microcomputer 40. Hereinafter, the duty ratio of the PWM signal is also referred to as the PWM duty ratio.

[0018] The microcomputer 40 obtains the power supply voltage value of the power supply voltage 6 from the voltage detector 50 , and obtains the motor current value flowing through the brushless motor 2 from the current detector 60 . Furthermore, the microcomputer 40 acquires a detection signal that detects the rotational position of the brushless motor 2 from the Hall IC 12, and calculates the number of rotations of the brushless motor 2 based on the detection signal.

[0019] The microcomputer 40 sets a PWM duty ratio based on a rotation speed instruction transmitted from, for example, the air conditioner ECU 8 and outputs the PWM duty ratio to the pre-driver 30 to control the rotation speed of the brushless motor 2.

[0020] In addition, the microcomputer 40 sets a lead angle instruction value to be output to the pre-driver 30 based on the power supply voltage value of the power supply voltage 6, the motor current value flowing through the brushless motor 2, the rotation speed of the brushless motor 2, the PWM duty ratio to be output to the pre-driver 30, and the like.

[0021] As shown in FIG. 2, the current detector 60 detects the value of the current flowing through the inverter 20, i.e., the value of the motor current flowing through the brushless motor 2, by amplifying the potential difference across the shunt resistor 70 using one differential amplifier 62.

[0022] When the microcomputer 40 determines that an overcurrent is flowing through the brushless motor 2 based on the motor current value detected by the current detector 60, it sets the duty ratio instructed to the pre-driver 30 to 0% and cuts off the power supplied to the brushless motor 2.

[0023] [2. Processing] Next, a motor control process in which the microcomputer 40 controls the rotation of the brushless motor 2 will be described with reference to the flowchart of Fig. 3. The motor control process of Fig. 3 is executed periodically at predetermined time intervals.

[0024] In S400, the microcomputer 40 acquires various information such as the power supply voltage value, the motor current value, and the motor rotation speed of the brushless motor 2. In S402, the microcomputer 40 determines whether the motor current value is equal to or greater than a predetermined value, and switches the following processing.

[0025] Here, if the tolerance of the motor current value detected by the current detector 60 is ±K [A] ​​and the margin for the tolerance is Y times, the predetermined value is calculated by the following formula (1). Note that the margin is a value that is set appropriately depending on the detection accuracy of the current detector 60, and is set to 1 time or more.

[0026] Predetermined value=K[A]×Y (1) For example, if the tolerance is ±1 [A] and the margin is 10 times, the predetermined value is 10 [A]. The predetermined value calculated from equation (1) represents the minimum current value that can be used as the motor current value detected by current detector 60. When the motor current value detected by current detector 60 is a predetermined value, if a margin of Y times is allowed for -K [A], which is the lower limit of the tolerance range of ±K [A], the motor current value becomes 0 [A]. 0 [A] can be used as the motor current value that controls the rotation of brushless motor 2.

[0027] Therefore, when the motor current value is equal to or greater than a predetermined value, even if a margin of Y is allowed for the lower limit of the tolerance range of ±K [A], the detected motor current value will be equal to or greater than 0 [A]. In other words, the positive and negative polarities of the detected motor current value are not reversed, so it can be used as the motor current value for controlling the advance angle of the rotation of the brushless motor 2.

[0028] In contrast, when the motor current value detected by current detector 60 is smaller than the predetermined value, allowing for a margin of Y times -K [A], which is the lower limit of the tolerance range of ±K [A] ​​for the current value, the positive and negative signs of the motor current value may be reversed. A motor current value with a reversed positive and negative sign cannot be used as a motor current value for controlling the advance angle of the rotation of brushless motor 2.

[0029] In order to reduce the predetermined value, it is necessary to reduce the tolerance range or the margin. In order to reduce the tolerance range or the margin, it is necessary to increase the detection accuracy of the current detector 60 by using a plurality of differential amplifiers 62, for example.

[0030] In the determination in S402, the predetermined value when the motor current value increases may be set to be greater than the predetermined value when the motor current value decreases, thereby providing hysteresis. If the determination in S402 is Yes, that is, if the motor current value is equal to or greater than the predetermined value, the process proceeds to S410.

[0031] If the determination in S402 is No, that is, if the motor current value is smaller than the predetermined value, in S404, the microcomputer 40 calculates the converted duty ratio from the power supply voltage value, the PWM duty ratio, and the motor rotation speed without using the motor current value, as follows, based on Fig. 4. Fig. 4 shows the maximum load PWM duty map and the no-load PWM duty map when the power supply voltage is at the maximum voltage, according to the motor rotation speed.

[0032] From FIG. 4, the microcontroller 40 obtains Dmax(N), which is the PWM duty ratio at maximum load when the power supply voltage is at the maximum voltage, and Dmin(N), which is the PWM duty ratio at no load, based on the motor rotation speed N obtained in S400.

[0033] Then, D(N), which is a conversion value of the PWM duty ratio at the current power supply voltage value acquired in S400, is calculated from the following equation (2). D(N) = (power supply voltage value / maximum voltage value) × Dmax(N) (2) Here, since the PWM duty ratio and the load are proportional, in S406 the microcomputer 40 calculates the ratio x [%] of D(N) to Dmax(N) and Dmin(N) from the following equation (3).

[0034] x[%]=((D(N)-Dmin(N)) / (Dmax(N)-Dmin(N)))×100 ···(3) The percentage x [%] in equation (3) indicates the percentage of the current load relative to the maximum load and no load.

[0035] In S408, the microcomputer 40 estimates the current lead angle value from the ratio x [%] calculated by the formula (3) based on FIG. First, the microcomputer 40 obtains the lead angle max(N), which is the lead angle value at the time of maximum load, and the lead angle min(N), which is the lead angle value at no load, based on the motor rotation speed obtained in S400 from Fig. 5. Fig. 5 shows the lead angle map at the maximum load and the lead angle map at no load when the power supply voltage is at the maximum voltage, according to the motor rotation speed.

[0036] Here, since the load and the lead angle value are proportional, the microcomputer 40 estimates the estimated lead angle (N), which is the lead angle value for the current power supply voltage value and motor rotation speed acquired in S400, by calculating using the following equation (4).

[0037] Estimated lead angle (N) = min lead angle (N) + (max lead angle (N) - min lead angle (N)) × x [%] / 100 (4) After execution of S408, the process proceeds to S412.

[0038] In S410, the microcomputer 40 estimates a lead angle value from the lead angle map shown in FIG. 5, based on the power supply voltage value, the motor current value, and the motor rotation speed acquired in S400. First, as described above, the load and the advance angle value are proportional, so x [%] in FIG. 5 is calculated from the following equation (5).

[0039] x [%] = ((Motor current value [A] × Power supply voltage value [V] – No load [W]) / (Maximum load [W] – No load [W])) × 100 (5) Then, based on x [%] calculated using equation (5), the lead angle max(N), which is the lead angle value at maximum load, and the lead angle min(N), which is the lead angle value at no load, the estimated lead angle (N) is calculated and estimated using equation (4), as in S408.

[0040] After execution of S410, the process proceeds to S412. In S412, the microcomputer 40 updates the lead angle value for controlling the pre-driver 30 with the lead angle value estimated in S408 or S410, controls the rotation of the brushless motor 2, and ends this process.

[0041] In the embodiment described above, the microcontroller 40 corresponds to the control unit and the current determination unit, the Hall IC 12 corresponds to the rotation speed detection unit, the voltage detector 50 corresponds to the voltage detection unit, and the current detector 60 corresponds to the current detection unit.

[0042] Moreover, S402 corresponds to the processing of the current determination unit, and S404 to S412 correspond to the processing of the control unit. [3. Effects] According to the embodiment described above, the following effects can be obtained.

[0043] (3a) In this embodiment, when the motor current value detected by the current detector 60 is equal to or greater than a predetermined value, taking into account the tolerance and margin of the current detector 60, the positive and negative polarities of the motor current value are not reversed. Therefore, the lead angle can be set based on the detected motor current value.

[0044] In contrast, when the motor current value is smaller than the predetermined value, taking into account the tolerance and margin of current detector 60, there is a possibility that the positive and negative signs of the motor current value will be reversed. The motor current value with the reversed positive and negative signs cannot be used for lead-angle control of brushless motor 2. In this case, the lead-angle value is set without using the motor current value detected by current detector 60.

[0045] In this way, when the detected motor current value is equal to or greater than a predetermined value, the lead-angle value is set using the motor current value, thereby enabling the lead-angle control of the rotation of brushless motor 2 to be performed by setting the lead-angle value using the detected motor current value without using a high-precision current detector.

[0046] Furthermore, since current detector 60 is originally installed to detect overcurrent and has a simple and inexpensive configuration, it is possible to detect the motor current value and set the lead angle value, thereby controlling the lead angle of brushless motor 2 without using a high-precision current detector.

[0047] (3b) By providing hysteresis by making the specified value when the motor current value increases larger than the specified value when the motor current value decreases, it is possible to prevent the judgment result of S402 from fluctuating when the motor current value fluctuates around the specified value.

[0048] [4. Other embodiments] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0049] (4a) In the above-described embodiment, the predetermined value when the motor current value increases is set to a value greater than the predetermined value when the motor current value decreases to provide hysteresis. However, the predetermined value may be set to a constant value and the judgment in S402 may be performed.

[0050] (4b) The motor controller 10 and techniques described in this disclosure may be implemented by a special purpose computer provided by configuring a processor and memory programmed to perform one or more functions embodied in a computer program.

[0051] Alternatively, the motor controller 10 and techniques described in this disclosure may be implemented in a special purpose computer provided by configuring a processor with one or more special purpose hardware logic circuits.

[0052] Alternatively, the motor controller 10 and techniques described herein may be implemented using one or more special purpose computers configured with a processor and memory programmed to perform one or more functions in combination with a processor configured with one or more hardware logic circuits.

[0053] The computer program may be stored in a computer-readable non-transitory recording medium as instructions executed by a computer. The method for realizing the functions of each unit included in the microcomputer 40 does not necessarily need to include software, and all of the functions may be realized using one or more pieces of hardware.

[0054] (4c) Multiple functions of a single component in the above-described embodiments may be realized by multiple components, and one function of a single component may be realized by multiple components.

[0055] Furthermore, multiple functions possessed by multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Also, part of the configuration of the above-mentioned embodiments may be omitted. Also, at least part of the configuration of the above-mentioned embodiments may be added to or substituted for the configuration of another of the above-mentioned embodiments.

[0056] (4d) In addition to the motor control device 10 described above, the present disclosure can be realized in various forms, such as a motor control system that includes the motor control device 10 as a component, a program for causing a computer to function as the motor control device 10, a non-transient physical recording medium such as a semiconductor memory on which the program is recorded, and a motor control method. [Explanation of symbols]

[0057] 2: brushless motor, 10: motor control device, 12: Hall IC (rotation speed detection unit), 40: microcomputer (control unit, current determination unit), 50: voltage detector (voltage detection unit), 60: current detector (current detection unit)

Claims

1. A control unit (40, S404 to S412) configured to control the rotation of the brushless motor (2); A rotation speed detection unit (12) configured to detect the rotation speed of the brushless motor; A voltage detection unit (50) configured to detect a power supply voltage value of the brushless motor; A current detection unit (60) configured to detect a motor current value flowing through the brushless motor; a current determination unit (40, S402) configured to determine whether a minimum current value that can be used as the motor current value detected by the current detection unit is set as a predetermined value and to determine whether the motor current value is equal to or greater than the predetermined value; Equipped with the control unit is configured to set a lead-angle value for lead-angle control of the brushless motor based on a load estimated from the power supply voltage value detected by the voltage detection unit, the rotation speed detected by the rotation speed detection unit, and a duty ratio for PWM control of the brushless motor by the control unit when the current determination unit determines that the motor current value is smaller than the predetermined value, and to set the lead-angle value based on the motor current value, the power supply voltage value, and the rotation speed when the current determination unit determines that the motor current value is equal to or greater than the predetermined value. Motor control device.

2. 2. The motor control device according to claim 1, the minimum current value is set based on a tolerance of the motor current value detected by the current detection unit and a margin for the tolerance. Motor control device.

3. 3. The motor control device according to claim 2, If the tolerance is ±K [A] ​​and the margin is Y times, the predetermined value is K×Y [A]. Motor control device.

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