Motor control device and motor control method

Abstract

To provide a motor control technique capable of calculating a target speed in a required range without adding circuit.SOLUTION: A motor control device comprises: a frequency detection part 10; an upper limit setting part 10; a duty ratio detection part 10; an expression computing part 10; a speed calculation part; and a speed control part 10. The upper limit setting part sets an upper limit of a duty ratio that can detect a pulse width modulation signal on the basis of a frequency detected by the frequency detection part. The expression computing part calculates a correspondence expression that correspondences the duty ratio with a target speed so that a value that is the upper limit or smaller set by the upper limit setting part is corresponded to the maximum value of the target speed of a motor 300. The speed calculation part calculates the target speed corresponded to the duty ratio detected by the duty comparison detection part by using the correspondence expression calculated by the expression calculation part.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to controlling a motor. [Background technology]

[0002] The control device for a brushless blower motor receives a pulse width modulation (PWM) signal from an external device, and controls the rotation speed of the motor based on a target speed corresponding to the duty ratio of the received PWM signal. The frequency of the PWM signal varies depending on the manufacturer of the external device that outputs the PWM signal. When applying the control device to multiple types of external devices, it is necessary to detect the duty ratio of the PWM signal within a specified frequency range.

[0003] Here, the waveform of the PWM signal becomes dull due to the influence of the time constant of the hardware of the input section of the control device. This hardware time constant does not depend on the frequency. Therefore, the higher the frequency of the PWM signal, the lower the detection accuracy of the duty ratio. If the duty ratio is not detected, the target speed corresponding to that duty ratio cannot be calculated. As a result, the control device cannot rotate the motor at that target speed.

[0004] The motor control device described in Patent Document 1 includes a signal input circuit to which a PWM signal for normal operation and a PWM signal for inspection, the PWM signal having a different voltage from that for normal operation, are input. The signal input circuit detects the voltage of the input PWM signal and detects the duty ratio of both the PWM signals for normal operation and the PWM signal for inspection by changing the threshold value for determining High and Low according to the detected voltage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2009-303458 A Summary of the Invention [Problem to be solved by the invention]

[0006] By increasing the number of circuits compared to when detecting the duty ratio of one type of PWM signal, as in the above motor control device, it is possible to detect the duty ratio of each of two or more types of PWM signals with high accuracy. However, adding circuits increases the cost and size of the control device.

[0007] The present disclosure provides a motor control technique that is capable of calculating a target speed in a required range without adding any circuitry. [Means for solving the problem]

[0008] A motor control device according to one aspect of the present disclosure includes a frequency detection unit (10), an upper limit setting unit (10), a duty ratio detection unit (10), an equation calculation unit (10), a speed calculation unit, and a speed control unit (10). The frequency detection unit detects the frequency of an input pulse width modulation signal. The upper limit setting unit sets an upper limit value of a detectable duty ratio of the pulse width modulation signal based on the frequency detected by the frequency detection unit. The duty ratio detection unit detects the duty ratio of the pulse width modulation signal. The equation calculation unit calculates a correspondence equation that associates the duty ratio with the target speed such that a value equal to or less than the upper limit value set by the upper limit setting unit corresponds to a maximum value of the target speed of the motor (300). The speed calculation unit calculates the target speed corresponding to the duty ratio detected by the duty ratio detection unit using the correspondence equation calculated by the equation calculation unit. The speed control unit controls the rotation speed of the motor based on the target speed calculated by the speed calculation unit.

[0009] The motor control device sets an upper limit of the detectable duty ratio based on the frequency of the PWM signal, and associates values ​​below the upper limit with the maximum value of the target rotation speed. Thus, the motor control device can calculate a target rotation speed in a range up to the maximum value according to the detected duty ratio. Therefore, it is possible to calculate a target rotation speed in a required range without adding any circuit to the motor control device.

[0010] A motor control method according to another aspect of the present disclosure includes receiving a pulse-width modulated signal, detecting a frequency of the received pulse-width modulated signal, setting an upper limit for a detectable duty ratio of the pulse-width modulated signal based on the detected frequency, detecting the duty ratio of the received pulse-width modulated signal, calculating a correspondence equation that matches the duty ratio with a target speed such that a value equal to or less than the set upper limit corresponds to a maximum value of a target speed of a motor (300), calculating a target speed that corresponds to the detected duty ratio using the calculated correspondence equation, and controlling a rotational speed of the motor based on the calculated target speed.

[0011] By carrying out the motor control method, the same effects as those of the motor control device can be achieved. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing a schematic configuration of a motor control device according to an embodiment of the present invention; [Diagram 2] FIG. 4 is a diagram illustrating a duty ratio of an input signal according to the embodiment. [Diagram 3] 3 is a diagram showing a high-frequency PWM signal and a low-frequency PWM signal input to the motor control device according to the present embodiment. FIG. [Figure 4] 5 is a diagram showing the correspondence between a detection range of a duty ratio and a target speed according to the embodiment; FIG. [Diagram 5] 5 is a flowchart showing a target speed calculation process according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. <1. Configuration> The configuration of a motor control device 100 according to this embodiment will be described with reference to Fig. 1. The motor control device 100 receives a motor drive signal from an external device 200 and controls the rotation of a motor 300. In this embodiment, the motor 300 is a three-phase brushless motor and is a blower motor for an air conditioner in a vehicle. The motor control device 100 is mounted on a vehicle and controls the rotation of the motor 300. The external device 200 is, for example, an air conditioner electronic control device. The motor drive signal is a pulse width modulation (hereinafter, PWM) signal.

[0014] The motor control device 100 includes an input unit 20 and a micro control unit (hereinafter, MCU) 10. The input unit 20 is connected to an output unit of an external device 200. The output unit of the external device 200 includes a first resistor R1, a second resistor R2, and a switching element SW1.

[0015] The switching element SW1 is a transistor, such as a bipolar transistor or a field effect transistor. In this embodiment, the switching element SW1 is a bipolar transistor, more specifically, an NPN-type bipolar transistor. A motor drive signal, which is a PWM signal, is input to the base of the switching element SW1. When the motor drive signal is High, the switching element SW1 is turned on, and when the motor drive signal is Low, the switching element SW1 is turned off.

[0016] A first end of the first resistor R1 is grounded, and a second end of the first resistor R1 is connected to the emitter of the switching element SW1. A first end of the second resistor R2 is connected to the collector of the switching element SW1. A second end of the second resistor R2 is connected to the input 20.

[0017] The input section 20 includes a power source 21, a capacitor C1, a third resistor R3, a fourth resistor R4, and a fifth resistor R5. A first end of the third resistor R3 is connected to a second end of the second resistor R2. A second end of the third resistor R3 is connected to a first end of the fifth resistor R5. A first end of the fourth resistor R4 is connected to the power source 21, and a second end of the fourth resistor R4 is connected to the second end of the third resistor R3 and the first end of the fifth resistor R5.

[0018] A second terminal of the fifth resistor R5 is connected to the input terminal of the MCU 10. A first terminal of the capacitor C1 is connected to the second terminal of the fifth resistor R5 and the input terminal of the MCU 10. A second terminal of the capacitor C1 is grounded.

[0019] When the switching element SW1 is in the off state, a current flows from the power supply 21 to the fourth resistor R4, the fifth resistor R5, and the capacitor C1, as shown by the solid arrow in Fig. 1. Therefore, when the switching element SW1 is in the off state, in a steady state, the potential of the power supply 21 (for example, 9 to 6 V) is input to the input terminal of the MCU 10.

[0020] When the switching element SW1 is in the on state, the charge stored in the capacitor C1 flows to the fifth resistor R5, the third resistor R3, the second resistor R2, the switching element SW1, and the first resistor R1, as shown by the dashed arrows in Fig. 1. Therefore, when the switching element SW1 is in the on state, in a steady state, the ground potential is input to the input terminal of the MCU 10. Therefore, when the motor drive signal input to the switching element SW1 is High, the input signal input to the MCU 10 becomes Low, and when the motor drive signal is Low, the input signal becomes High.

[0021] The MCU 10 is configured as a system-in-package in which multiple semiconductor chips are integrated into one package. The MCU 10 includes the functions of a Hi / Low determination unit 11, a processing time acquisition unit 13, a duty ratio detection unit 15, a target speed calculation unit 17, and a speed control unit 19. The target speed calculation unit 17 includes the functions of a frequency detection unit, an upper limit setting unit, a lower limit setting unit, an equation calculation unit, and a speed calculation unit of the present disclosure.

[0022] The Hi / Lo determination unit 11 compares the potential of the input signal input to the MCU 10 with a threshold value to determine whether the motor drive signal is High or Low. The processing time acquisition unit 13 acquires the processing time of the MCU 10. In detail, the processing time acquisition unit 13 acquires the time lag from the rising or falling edge of the input signal to when High or Low is read.

[0023] The duty ratio detection unit 15 detects the duty ratio of the motor drive signal based on the input signal determination result by the Hi / Low determination unit 11 and the processing time acquired by the processing time acquisition unit 13. Specifically, as shown in FIG. 2, the duty ratio detection unit 15 calculates the ratio of period T1 to period T2 of the input signal as the duty ratio. Period T2 is the period from the falling edge of the input signal to the next falling edge, i.e., the period of one cycle. Period T1 is the period from the falling edge of the input signal to the next rising edge, i.e., the period when the input signal is Low. Since the High and Low of the input signal are inverted with the High and Low of the motor drive signal, the duty ratio of the motor drive signal is the ratio of period T1 to period T2 of the input signal.

[0024] The target speed calculation unit 17 calculates the target speed based on the duty ratio detected by the duty ratio detection unit 15 and a correspondence equation between the duty ratio and the target speed of the motor 300. The target speed calculation unit 17 calculates a larger target speed as the duty ratio increases.

[0025] The speed control unit 19 generates a command signal for the motor 300 so that the actual rotation speed of the motor 300 becomes the calculated target speed. The speed control unit 19 controls the motor drive circuit based on the generated command signal to control the rotation of the motor 300.

[0026] The motor control device 100 is mounted on various vehicles. That is, the motor control device 100 receives a motor drive signal from an external device 200. The frequency of the motor drive signal output from one external device 200 is constant, but the frequency of the motor drive signal varies depending on the manufacturer of the external device 200. In this embodiment, the external device 200 is an air conditioner electronic control device or the like for vehicles manufactured by various vehicle manufacturers. Therefore, the motor drive signal received by the motor control device 100 can have a wide range of frequencies. Therefore, in order to apply the motor control device 100 to various external devices 200, the motor control device 100 needs to detect the duty ratio of the motor drive signal in a wide frequency range.

[0027] The waveform of the input signal input to the MCU 10 becomes dull depending on the time constant of the hardware of the input unit 20. This time constant does not depend on the frequency of the input signal, i.e., the frequency of the motor drive signal. As shown in FIG. 3, the waveform of both the input signal of the first input frequency and the input signal of the second input frequency becomes dull in the same manner. The first input frequency is a relatively low frequency, and the second input frequency is a relatively high frequency.

[0028] Therefore, the higher the input frequency of the input signal, the less the MCU 10 can detect the duty ratio in the low region and the duty ratio in the high region. In the correspondence equation between the duty ratio and the target speed, if a target speed is assigned to a duty ratio that cannot be detected, the MCU 10 cannot calculate the target speed assigned to the duty ratio that cannot be detected, and therefore cannot rotate the motor 300 at that target speed.

[0029] For example, if the maximum target speed MAX is assigned to a duty ratio higher than the detectable range in the correspondence formula, the target speed calculation unit 17 cannot calculate the maximum target speed MAX, and therefore the MCU 10 cannot rotate the motor 300 at the maximum target speed MAX.

[0030] Therefore, the target speed calculation unit 17 detects the frequency of the input signal, i.e., the frequency of the motor drive signal, and sets a detectable duty ratio range according to the frequency. Then, the target speed calculation unit 17 calculates a correspondence equation that assigns target speeds from a minimum value MIN to a maximum value MAX to the detectable duty ratio range. The target speed calculation unit 17 calculates the target speed based on the calculated correspondence equation and the detected duty ratio.

[0031] In Fig. 4, the first correspondence equation is shown by a dashed line, and the second correspondence equation is shown by a solid line. The first correspondence equation shows the correspondence between the duty ratio and the target speed when the frequency of the input signal is the first input frequency. The second correspondence equation shows the correspondence between the duty ratio and the target speed when the frequency of the input signal is the second input frequency.

[0032] As shown in Fig. 4, since the first input frequency is lower than the second input frequency, the first detection range is wider than the second detection range and includes the second detection range. The first detection range is a range of detectable duty ratios when the frequency of the input signal is the first input frequency. The second detection range is a range of detectable duty ratios when the frequency of the input signal is the second input frequency.

[0033] When the frequency of the input signal is the first input frequency, the target speed calculation unit 17 assigns the maximum value MAX of the target speed to a value U11 that is equal to or less than the upper limit of the first detection range. For example, the value U11 is a value obtained by subtracting a margin (e.g., 0 to several percent) from the upper limit of the first detection range. Furthermore, the target speed calculation unit 17 assigns the minimum value MIN of the target speed to a value L11 that is equal to or greater than the lower limit of the first detection range. For example, the value L11 is a value obtained by adding a margin (e.g., 0 to several percent) to the lower limit of the first detection range. The target speed calculation unit 17 calculates a first correspondence equation so that the maximum value MAX of the target speed corresponds to the value U11, and the minimum value MIN of the target speed corresponds to the value L11.

[0034] When the frequency of the input signal is the second input frequency, the target speed calculation unit 17 assigns the maximum value MAX of the target speed to U21, which is equal to or less than the upper limit of the second detection range. For example, the value U21 is a value obtained by subtracting a margin (for example, 0 to several percent) from the upper limit of the second detection range. Furthermore, the target speed calculation unit 17 assigns the minimum value MIN of the target speed to a value L21, which is equal to or greater than the lower limit of the second detection range. For example, the value L21 is a value obtained by adding a margin (for example, 0 to several percent) to the lower limit of the second detection range. The target speed calculation unit 17 calculates a second correspondence equation so that the maximum value MAX of the target speed corresponds to the value U21, and the minimum value MIN of the target speed corresponds to the value L21.

[0035] When the frequency of the input signal is the first input frequency, the target speed calculation unit 17 calculates the target speed to 0 in response to the duty ratio exceeding the value U11 until the duty ratio becomes equal to or less than the value U12. Then, the target speed calculation unit 17 calculates the target speed based on the first correspondence equation in response to the duty ratio becoming equal to or less than the value U12. The value U12 is several percent lower than the value U11. Also, the target speed calculation unit 17 calculates the target speed to 0 in response to the duty ratio becoming less than the value L11 until the duty ratio becomes equal to or more than the value L12. Then, the target speed calculation unit 17 calculates the target speed based on the first correspondence equation in response to the duty ratio becoming equal to or more than the value L12. The value L12 is several percent higher than the value L11.

[0036] Similarly, when the frequency of the input signal is the second input frequency, the target speed calculation unit 17 calculates the target speed to 0 in response to the duty ratio exceeding the value U21 until the duty ratio becomes equal to or less than the value U22. Then, the target speed calculation unit 17 calculates the target speed based on the second correspondence equation in response to the duty ratio becoming equal to or less than the value U22. The value U22 is several percent lower than the value U21. Also, the target speed calculation unit 17 calculates the target speed to 0 in response to the duty ratio becoming less than the value L21 until the duty ratio becomes equal to or more than the value L22. Then, the target speed calculation unit 17 calculates the target speed based on the second correspondence equation in response to the duty ratio becoming equal to or more than the value L22. The value L22 is several percent higher than the value L21.

[0037] <2. Processing> Next, a target speed calculation process executed by the target speed calculation unit 17 will be described with reference to the flowchart of Fig. 5. The target speed calculation unit 17 repeatedly executes this process at a predetermined cycle.

[0038] In S10, it is determined whether the input frequency of the acquired input signal is within a range of A0 or more and A1 or less. Here, it is determined whether the input frequency is within a normal range. If it is determined that the input frequency is less than A0 or greater than A1, the process proceeds to S20.

[0039] In S20, it is determined that the input frequency is abnormally low or abnormally high. For example, when noise is mixed into the input signal, the input frequency is detected as abnormally low or abnormally high. In this case, the target speed is not calculated and this process is terminated.

[0040] If it is determined in S10 that the input frequency is within the range of A0 or more and A1 or less, the process proceeds to S30. In S30, it is determined whether the input frequency is within a range of A0 or more and A2 or less (hereinafter, the first frequency range). A2 is a value smaller than A1. If it is determined that the input frequency is within the first frequency range, the process proceeds to S40. If it is determined that the input frequency is outside the first frequency range, that is, if it is determined that the input frequency is within a range of greater than A2 and less than or equal to A1, the process proceeds to S60.

[0041] In S40, upper and lower limits of the detectable duty ratio are set, which correspond to a first frequency range, which is a lower frequency range within the normal frequency range. Next, in S50, a correspondence equation is calculated so that values ​​equal to or less than the upper limit set in S40 correspond to the maximum value MAX, and values ​​equal to or greater than the lower limit set in S40 correspond to the minimum value MIN. In more detail, variables X1 and Y1 of the correspondence equation of target speed = duty ratio x X1 + Y1 are calculated. Then, the target speed is calculated from the duty ratio detected by the duty ratio detection unit 15 and the calculated correspondence equation, and this process ends.

[0042] If it is determined in S30 that the input frequency is outside the range of A0 or more and A2 or less, the process proceeds to S60. In S60, it is determined whether the input frequency is greater than A2 and less than or equal to A3 (hereinafter, second frequency range). A3 is a value greater than A2 and less than or equal to A1. If it is determined that the input frequency is within the second frequency range, the process proceeds to S70.

[0043] In S70, upper and lower limits of the detectable duty ratio corresponding to a second frequency range are set. The second frequency range is a normal frequency range that is higher than the first frequency range.

[0044] Subsequently, in S80, a correspondence formula is calculated such that a value equal to or less than the upper limit value set in S70 corresponds to the maximum value MAX, and a value equal to or greater than the lower limit value set in S70 corresponds to the minimum value MIN. Specifically, the variables X2 and Y2 of the correspondence formula of target speed = duty ratio × X2 + Y2 are calculated. Then, the target speed is calculated from the duty ratio detected by the duty ratio detection unit 15 and the calculated correspondence formula, and this process ends.

[0045] In S60, when it is determined that the input frequency is outside the second frequency range, A2 is replaced with A3 (<A1), A3 is replaced with A4, and the processes of S60 to S80 are repeated. A4 is a value greater than A3 and equal to or less than A1. That is, the normal frequency range is divided into two or more frequency ranges, and for each frequency range, the upper limit value and the lower limit value of the duty ratio are set. Then, for each frequency range, a correspondence formula is calculated and the target frequency is calculated.

[0046] When dividing the normal frequency range into two, the first frequency range A0 to A2 and the second frequency range A2 to A3 (= A1), the process of S60 is deleted. Depending on the number of divisions of the normal frequency range, the frequency determination range in S60 is changed, and the processes of S60 to S58 are repeatedly executed.

[0047] <3. Effects> According to the present embodiment described in detail above, the following effects can be obtained. (1) According to the input frequency, the target speed from the minimum value MIN to the maximum value MAX is associated with the detectable duty ratio range. Therefore, the motor 300 can be rotated at a speed corresponding to the detected duty ratio within the range from the minimum value MIN to the maximum value MAX.

[0048] (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 modifications.

[0049] (a) In the above embodiment, upper and lower limit values ​​of the duty ratio corresponding to each frequency range are set, but only the upper limit value of the duty ratio may be set, and the lower limit value may be a constant value regardless of the input frequency. In this case, the motor 300 can be rotated at the maximum value MAX regardless of the input frequency. In other words, the motor 300 can be rotated using the high-speed region.

[0050] (b) The motor control device and the method thereof described in the present disclosure may be realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the motor control device and the method thereof described in the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the motor control device and the method thereof described in the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transient tangible recording medium as instructions executed by a computer. The method for realizing the functions of each unit included in the motor control device does not necessarily need to include software, and all of the functions may be realized using one or more hardware.

[0051] (c) Multiple functions possessed by one component in the above embodiments may be realized by multiple components, or one function possessed by one component may be realized by multiple components. Also, 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 embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0052] (d) In addition to the motor control device described above, the present disclosure can be realized in various forms, such as a system that includes the motor control device as a component, a program for causing a computer to function as the motor control device, and a non-transient physical recording medium such as a semiconductor memory on which the program is recorded. [Explanation of symbols]

[0053] 11: determination unit, 13: processing time acquisition unit, 15: duty ratio detection unit, 17: target speed calculation unit, 20: input unit, 100: motor control device, 200: external device, 300: motor.

Claims

1. A frequency detection unit (10) for detecting the frequency of an input pulse width modulated signal; an upper limit setting unit (10) that sets an upper limit value of a detectable duty ratio of the pulse width modulation signal based on the frequency detected by the frequency detection unit; A duty ratio detection unit (10) for detecting a duty ratio of the pulse width modulation signal; an equation calculation unit (10) that calculates a correspondence equation that makes the duty ratio correspond to the target speed so that a value equal to or less than the upper limit value set by the upper limit setting unit corresponds to a maximum value of the target speed of the motor (300); a speed calculation unit that calculates the target speed corresponding to the duty ratio detected by the duty ratio detection unit, using the corresponding equation calculated by the equation calculation unit; A speed control unit (10) that controls the rotation speed of the motor based on the target speed calculated by the speed calculation unit. Motor control device.

2. a lower limit setting unit (10) that sets a lower limit of a detectable duty ratio of the pulse width modulation signal based on the frequency detected by the frequency detection unit; The equation calculation unit further calculates the correspondence equation so as to make a value equal to or greater than the lower limit value set by the lower limit setting unit correspond to a minimum value of the target speed. The motor control device according to claim 1 .

3. The motor (300) is mounted on a vehicle. The motor control device according to claim 1 or 2.

4. Receives a pulse width modulated signal; Detecting the frequency of the received pulse width modulated signal; setting an upper limit of a detectable duty ratio of the pulse width modulation signal based on the detected frequency; Detecting a duty ratio of the received pulse width modulated signal; Calculating a correspondence equation that associates the duty ratio with the target speed so that a value equal to or less than the set upper limit value corresponds to a maximum value of the target speed of the motor (300); Calculating the target speed corresponding to the detected duty ratio using the calculated correspondence equation; controlling the rotation speed of the motor based on the calculated target speed; Motor control methods.

5. setting a lower limit value of a detectable duty ratio of the pulse width modulation signal based on the detected frequency; Furthermore, the correspondence equation is calculated so as to make a value equal to or greater than the set lower limit value correspond to a minimum value of the target speed.

5. The motor control method according to claim 4.

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