Rotation angle detection method, program, and rotation angle detection device

Abstract

The present application provides a rotation angle detection method, a rotation angle detection program, and a rotation angle detection device capable of accurately calculating the rotation angle of a motor when the motor is inertially rotating. The rotation angle detection method includes: a current measurement process for measuring the current flowing through the motor; and a rotation angle detection process for calculating the rotation angle of the motor based on the current value measured by the current measurement process, wherein in the rotation angle detection process, the time constant of the decay of the current of the motor is calculated based on the current value measured by the current measurement process after a predetermined time from the time point at which the polarity of the current value of the reverse current measured by the current measurement process when the motor is inertially rotating is reversed and the absolute value reaches a peak until the current value measured by the current measurement process becomes zero, and the rotation angle in the inertial rotation is calculated based on the calculated time constant.

Description

TECHNICAL FIELD

[0001] The present application relates to a rotation angle detection method, a rotation angle detection program, and a rotation angle detection device. BACKGROUND

[0002] In the past, there has been a device that acquires information about rotation of a motor that has a rectifier, in which the device includes: a rotation angle calculation section that calculates a rotation angle of the motor based on a voltage between terminals of the motor and a current flowing in the motor; a first signal generation section that generates a first signal based on a pulsation component contained in the current flowing in the motor; a second signal generation section that generates a pseudo-pulsation signal as a second signal that indicates that the motor has rotated by a predetermined angle, based on the first signal and the rotation angle; and a rotation information calculation section that calculates information about rotation of the motor based on an output of the second signal generation section (for example, see Patent Literature 1).

[0003] Patent Literature 1: International Publication No. 2018-123453

[0004] However, in the device of the past, since the pulsation component cannot be detected along with decay of the current during a period in which inertial rotation is performed after power supply to the motor is stopped, there is a tendency for an angle error to become large. SUMMARY

[0005] In view of this, an object of the present application is to provide a rotation angle detection method, a rotation angle detection program, and a rotation angle detection device that can accurately calculate a rotation angle of a motor when the motor is performing inertial rotation.

[0006] The rotation angle detection method of an embodiment of the present application includes: a current measurement process that measures a current flowing through a motor; and a rotation angle detection process that calculates a rotation angle of the motor based on a current value measured by the current measurement process, characterized in that, in the rotation angle detection process, after a time point at which a polarity of a current value of a reverse current measured by the current measurement process when the motor is performing inertial rotation is reversed and an absolute value reaches a peak value elapses a predetermined time, until the current value measured by the current measurement process becomes zero, the current value measured by the current measurement process is used to calculate a time constant of decay of the current of the motor, and the rotation angle in the inertial rotation is calculated based on the calculated time constant.

[0007] EFFECT OF THE INVENTION

[0008] A rotation angle detection method, a rotation angle detection program, and a rotation angle detection device that can accurately calculate a rotation angle of a motor when the motor is performing inertial rotation can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a diagram showing a rotation angle detection device 100 of an embodiment.

[0010] Figure 2 is a diagram showing a connection state of a DC motor 10 and a drive circuit 20.

[0011] Figure 3 is a diagram showing time changes of a current i and an angular velocity ω before and after the DC motor 10 is disconnected.

[0012] Figure 4 is a diagram showing an angular velocity ω and a current i of the DC motor 10 in a period in which the DC motor 10 performs inertial rotation.

[0013] Figure 5 is a diagram showing a flowchart showing a process of detecting a rotation angle by the rotation angle detection section 133B. DETAILED DESCRIPTION

[0014] Hereinafter, an embodiment of a rotation angle detection method, a rotation angle detection program, and a rotation angle detection device to which the present application is applied will be described.

[0015] <EMBODIMENT>

[0016] Figure 1 is a diagram showing a rotation angle detection device 100 of an embodiment. The motor whose rotation angle is detected by the rotation angle detection device 100 is not limited to a motor that drives a power window of a vehicle, but here, as one example, a mode in which the rotation angle detection device 100 of the embodiment is used as a rotation angle detection device of a motor of a power window will be described.

[0017] Figure 1 In addition to the rotation angle detection device 100, a DC (Direct Current) motor 10, a resistor 15, a drive circuit 20, a direct current power supply 30, a power window 50, and a drive mechanism 51 are shown in the figure.

[0018] The DC motor 10 has terminals 11, 12, and is driven by the drive circuit 20 connected to the terminals 11, 12. The resistor 15 is connected to the terminal 12 of the DC motor 10, and is used to detect a current of the DC motor 10. The drive circuit 20 drives the DC motor 10 by direct current power supplied from the direct current power supply 30. The drive circuit 20 drives the DC motor 10 by being controlled by a drive control section not shown, which is omitted here.

[0019] The power window 50 is a power window of a vehicle, which is opened and closed by a driving force transmitted from a rotor (rotating member) of the DC motor 10 via a driving mechanism 51. The driving mechanism 51 is a mechanical mechanism such as an adjuster, which is provided in the interior of a door panel of the vehicle or the like, and which converts the rotational force of the rotor of the DC motor 10 into the driving force in the up-and-down direction of the power window 50.

[0020] The rotation angle detection device 100 includes a filter circuit 110, an IC (Integrated Circuit) chip 120, and a microcomputer 130.

[0021] The filter circuit 110 has LPFs (Low Pass Filters) 111, 112. The voltage between the terminals 11, 12 of the DC motor 10 is input to the LPF 111, and the frequency-high noise and the like contained in the voltage are removed and output to the microcomputer 130. The voltage between the both ends of the resistor 15 as the voltage indicating the current of the DC motor 10 is input to the LPF 112, and the frequency-high noise and the like contained in the voltage are removed and output to the microcomputer 130.

[0022] The IC chip 120 has a BPF (Band Pass Filter) 121 and a pulsation detection section 122. The voltage between the both ends of the resistor 15 as the voltage indicating the current of the DC motor 10 is input to the BPF 121, and the frequency-high noise and the frequency-low noise and the like contained in the voltage are removed and output to the pulsation detection section 122. The pulsation detection section 122 detects the pulsation contained in the data indicating the current input from the BPF 121, and converts the pulsation into a pulse to output to the microcomputer 130.

[0023] The microcomputer 130 has A / D (Analog to Digital) converters 131, 132 and a processing section 133. The microcomputer 130 is realized by a computer including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an input / output interface, an internal bus, and the like. The A / D converters 131, 132 and the processing section 133 are components which exhibit the functions of the program executed by the microcomputer 130 as function modules.

[0024] The A / D converter 131 converts the output of the LPF 111 into a digital signal and outputs to the processing section 133. Since the output of the LPF 111 indicates the voltage of the DC motor 10, the output of the A / D converter 131 is digital data indicating the voltage value of the DC motor 10.

[0025] A / D converter 132 converts the output of LPF112 into a digital signal and outputs it to processing unit 133. Since the output of LPF112 is a signal representing the current of DC motor 10, the output of A / D converter 132 is digital data representing the current value of DC motor 10.

[0026] The processing unit 133 includes a current measuring unit 133A, a rotation angle detecting unit 133B, and a memory 133C. The current measuring unit 133A and the rotation angle detecting unit 133B are components that display the functions of the program executed by the microcomputer 130 as functional modules. In addition, the memory 133C is a component that displays the memory of the microcomputer 130 as a functional module.

[0027] The current measuring unit 133A performs current measurement processing based on the output of the A / D converter 132 to measure the current flowing through the DC motor 10. The current measuring unit 133A outputs data indicating the measured current value to the rotation angle detection unit 133B.

[0028] The rotation angle detection unit 133B performs rotation angle detection processing based on the output (voltage value) of the A / D converter 131, the output (current value) of the current measuring unit 133A, and the pulse input from the pulsation detection unit 122 to determine the rotation angle during the period of inertial rotation of the DC motor 10. The inertial rotation of the DC motor 10 refers to the rotation of the rotor of the DC motor 10 due to inertia when the voltage applied to the DC motor 10 by the drive circuit 20 is cut off (the DC motor 10 is disconnected). The inertial rotation of the DC motor 10 occurs when the drive control unit (not shown) controls the drive circuit 20 to cut off the voltage applied to the DC motor 10 by the drive circuit 20.

[0029] The rotation angle detection unit 133B calculates the rotation angle of the rotor of the DC motor 10 during the period of inertial rotation. The rotation angle of the rotor of the DC motor 10 is synonymous with the rotation angle of the DC motor 10. The specific method for calculating the rotation angle will use... Figures 2 to 5 To be discussed later.

[0030] The memory 133C stores the program and data used when the current measuring unit 133A and the rotation angle measuring unit 133B perform processing, the output (voltage value) of the A / D converter 131, the output (current value) of the current measuring unit 133A, and the pulse data input from the pulsation detection unit 122.

[0031] Next, use Figure 2 The connection status between the DC motor 10 and the drive circuit 20 is explained. Figure 2This diagram shows the connection status between the DC motor 10 and the drive circuit 20. The drive circuit 20 has two switches 21 and 22. Figure 2 (A) indicates the connection state of the drive circuit 20 that connects the DC motor 10.

[0032] To turn on the DC motor 10, simply switch switches 21 and 22 to connect the DC motor 10 to the DC power supply 30. Additionally, Figure 2 (B) shows the connection state of the drive circuit 20 when the DC motor 10 is disconnected. To disconnect the DC motor 10, simply switch switches 21 and 22 to disconnect the DC motor 10 from the DC power supply 30. As an example, when the DC motor 10 is disconnected, both terminals of the DC motor 10 are connected to the negative terminal of the DC power supply 30. This is the state where the DC motor 10 is short-circuited.

[0033] Next, based on the theory of DC motors, we will explain the circuit equations that hold true for DC motor 10. For DC motor 10, according to the theory of DC motors, the following equations (1) and (2) hold true. L is the inductance of DC motor 10, R is the resistance of DC motor 10, J is the rotor inertia of DC motor 10, Ke is the back electromotive force constant of DC motor 10, Kt is the torque constant of DC motor 10, Kv is the viscous friction coefficient of DC motor 10, F is the load of DC motor 10, u is the driving voltage applied to DC motor 10 from drive circuit 20, and i is the voltage applied to DC motor 10 by drive circuit 20. Figure 1 The current flowing through the DC motor 10 is measured by the current measuring unit 133A. The current i is the current value obtained by the current measuring unit 133A from the output of the A / D converter 132, and it represents the current waveform when arranged in time sequence.

[0034] Formula 1

[0035]

[0036]

Formula 2

[0037]

[0038] If DC motor 10 is disconnected, then due to... Figure 2 As shown in (B), terminals 11 and 12 of the DC motor 10 are short-circuited, so the driving voltage u(t) of the DC motor 10 is 0, and the DC motor 10 begins to rotate due to inertia. Furthermore, if we assume that the change in current i (di / dt) is zero when the energy discharge of inductor L ends, then according to equation (1), a proportional relationship expressed by equation (3) holds between the current i and the angular velocity ω of the DC motor 10. The angular velocity ω is the angular velocity of the rotating component (rotor) of the DC motor 10.

[0039]

Formula 3

[0040]

[0041] If we substitute equation (3) into equation (2) and assume that the load F of the DC motor 10 is zero when the terminals 11 and 12 are short-circuited, the angular velocity can be expressed by equation (4). Here, ω0 is the angular velocity of the DC motor 10 when it starts to rotate inertia, and τ is the time constant of the decay of the angular velocity ω of the DC motor 10.

[0042]

Formula 4

[0043]

[0044] In addition, the time constant τ of the decay of the angular velocity ω of the DC motor 10 can be represented by the following equation (5).

[0045]

Formula 5

[0046]

[0047] According to equation (5), the time constant τ is affected by the variation of many parameters. It should be noted that, according to equations (3) and (4), the angular velocity ω of the inertial rotation of the DC motor 10 decays exponentially, and the current i also decays exponentially. That is, the time constant of the decay of the current i of the DC motor 10 is equal to the time constant τ of the decay of the angular velocity of the DC motor 10.

[0048] Figure 3 This is a graph showing the time-varying current i versus angular velocity ω before and after the DC motor 10 is disconnected. Figure 3 In (A), the time variation of current i and angular velocity ω before and after the DC motor 10 is disconnected is represented as is. If the DC motor 10 is disconnected, the DC motor 10 rotates due to inertia, and the angular velocity ω decays exponentially. After a constant period, the current i also decays exponentially. The reason why the current i is delayed relative to the angular velocity ω is because of the current flow caused by back electromotive force. The current caused by back electromotive force is a reverse current that flows in the opposite direction to the current flowing when the DC motor 10 is connected.

[0049] Here, if Figure 3 The waveform of the current i in (A) is -K times and overlaps with the angular velocity ω, then as follows Figure 3As shown in (B), the current i overlaps with the angular velocity ω during the period of inertial rotation. This is because the time constant of the decay of the current i of the DC motor 10 is equal to the time constant τ of the decay of the angular velocity of the DC motor 10. Therefore, in the rotation angle detection device 100, the angular velocity ω is calculated based on the current i of the DC motor 10 instead of the time constant τ of the decay of the angular velocity of the DC motor 10, and the rotation angle during the period of inertial rotation of the DC motor 10 is detected based on the calculated angular velocity ω. That is, the rotation angle detection device 100 infers the time constant τ of the decay of the current i calculated based on the current i during the period of inertial rotation of the DC motor 10 as the time constant τ of the decay of the angular velocity during the period of inertial rotation of the DC motor 10 and uses it to detect the rotation angle during the period of inertial rotation of the DC motor 10.

[0050] Next, use Figure 4 A method for detecting angular velocity ω based on the current i of a DC motor 10 is explained. Figure 4 This is a graph showing the angular velocity ω of the DC motor 10 versus the current i during the period of inertial rotation. Figure 4 Lieutenant General Figure 3 The period of inertial rotation in (B) is magnified. That is, Figure 4 The current i shown is Figure 3 The waveform of the current i in (A) is represented by a waveform that is -K times the waveform of the current i.

[0051] The following, such as Figure 4 As shown, a method is explained that uses a waveform of current i equal to -K times the waveform of angular velocity ω to calculate the integral value of the current, etc. However, in actual calculations, the current i may not be equal to -K times. Therefore, when explaining the calculation method, the current i will be used as is.

[0052] exist Figure 4 In this context, time point t0 is the point at which the DC motor 10 is disconnected (power is turned off), and it is the point at which the DC motor 10 begins to rotate due to inertia. The angular velocity ω0 at time point t0 is the angular velocity of the DC motor 10 just before the power is about to be disconnected. The angular velocity ω0 can be calculated based on the pulses input from the pulse detection unit 122. Furthermore, if the power supply to the DC motor 10 is disconnected, the drive circuit 20 becomes... Figure 2 The connection state of (B).

[0053] Here, the explanation will use the period from the time point t0 when the DC motor 10 begins its inertial rotation until the time point tend when the current i of the DC motor 10 becomes zero. Since the rotation of the DC motor 10 can be considered to stop when the current i becomes zero, the angular velocity ωend of the DC motor 10 at time point tend can be considered to be zero.

[0054] The time point tl is a time point at which the polarity of the current i is reversed. The time point tl is a time point at which the value of the current - Ki shown in the drawing is reversed from negative to positive (the polarity is reversed). Therefore, the current value il at the time point tl is zero. Figure 4

[0055] If the DC motor 10 is turned off, a current in the opposite direction to that when the DC motor 10 is turned on flows due to the counter electromotive force. The time point tl is a time point at which the polarity of the current i is reversed due to the opposite direction current caused by the counter electromotive force. Further, the angular velocity ωl at the time point tl is treated as being equal to the angular velocity ωO. This is because from the time when the DC motor 10 is turned off until the time point tl at which the polarity of the current i is reversed due to the counter electromotive force, the rotor of the DC motor 10 is hardly subjected to braking caused by the opposite direction current i due to the counter electromotive force.

[0056] The time point t2 is a time point at which the current - Ki takes a maximum value (the current i takes a peak value). That is, the time point t2 is a time point at which the absolute value of the actual current i takes a peak value. In other words, the time point t2 is a time point at which the actual current i takes a minimum value. The current value i2 at the time point t2 is the minimum value of the actual current i and is the peak value of the absolute value. Since the current i fluctuates, when the current i measured by the current measuring section 133A enters a prescribed range, the rotation angle detecting section 133B can determine that the absolute value of the current i takes a peak value. The angular velocity ω2 at the time point t2 is attenuated from the angular velocity ωl at the time point tl. This is because braking caused by the opposite direction current i is applied.

[0057] The time point t3 is a time point after (after a lapse of) a prescribed time ΔT from the time point t2. The prescribed time ΔT is a time (period) considered to be required from when the current - Ki takes a maximum value until the fluctuation amplitude of the value of the current - Ki is stabilized to some extent. If the actual current i is considered, the prescribed time ΔT is a time (period) considered to be required from when the absolute value of the current i takes a peak value until the fluctuation amplitude of the value of the current i is stabilized to some extent. As one example, the prescribed time ΔT is about 1 / 10 of the time required from the time point t2 to the time point tend at which the current i becomes zero. Data indicating the prescribed time ΔT can be stored in the memory 133C in advance.

[0058] Since the current i attenuates in the same exponential curve as the angular velocity ω after a constant period elapses from the start of the inertial rotation as described above, the current i after the time point t3 can be represented by the following equation (6) using the current value i3 at the time point t3 according to equation (4). ​

[0059]

Formula 6

[0060]

[0061] In addition, Figure 4 Let t4 be a time point between time point t3 and the time point when current i becomes zero (tend). Additionally, let Si3 be the integral value of current i from time point t3 to time point t4, and let Si4 be the integral value of current i from time point t4 to time point (tend).

[0062] The rotation angle detection unit 133B calculates the current integral value Si3+Si4 of the current i from time point t3 through time point t4 to time point tend, and the current integral value Si4 of the current i from time point t4 to time point tend. The current integral value Si3+Si4 is an example of the first current integral value, and the current integral value Si4 is an example of the second current integral value.

[0063] The current integral value Si3+Si4 and the current integral value Si4 can be obtained by the following equations (7) and (8), respectively.

[0064]

Formula 7

[0065]

[0066]

Form 8

[0067]

[0068] Since the integral processing of current i implemented by equations (7) and (8) has a filtering effect equivalent to the filtering process, it has the effect of removing the pulsating component contained in current i.

[0069] The time point t4 can be represented by the following equation (9). In equation (9), Kr is an adjustment coefficient less than 1 (Kr < 1).

[0070]

Form 9

[0071] t4=t3+Kr*(tend-t3) (9)

[0072] If time point t4 is between time point t3 and time point temp, it can be any time point. However, for the convenience of the calculation of current integral values ​​Si3 and Si4 described later, it is preferable that there is a certain period up to time point temp so that the current integral value Si4 is not too small. In addition, it is set that the current integral values ​​Si3 and Si4 are not equal.

[0073] The time constant τ of the decay of the current i of the DC motor 10 can be calculated as in the following Equation (10) from Equation (7) and Equation (8). Since the time constant τ of the decay of the current i of the DC motor 10 is equal to the time constant of the decay of the angular velocity of the DC motor 10, the time constant τ of the decay of the current i of the DC motor 10 is calculated instead of the time constant of the decay of the angular velocity of the DC motor 10.

[0074] [Equation 10]

[0075]

[0076] Since the natural logarithm in Equation (10) includes the division process of (Si3+Si4) / Si4, an effect of reducing the measurement error of the current of the A / D converter 132 and the like, which is included in the circuit of the resistance 15, the LPF 112, the A / D converter 132, and the like, can be obtained.

[0077] Alternatively, instead of Equation (10), the time constant τ of the decay of the current i of the DC motor 10 can be calculated directly from Equation (7) as in the following Equation (11).

[0078] [Equation 11]

[0079]

[0080] If Equation (11) is used to calculate the time constant τ, the number of calculations is less and simple compared to the case where Equation (10) is used to calculate the time constant τ, but since the current i3 is used, the time constant τ calculated using Equation (10) is more likely to be affected by the pulsation component and the measurement error. Therefore, which one of Equation (10) and Equation (11) to use can be determined depending on the use of the rotation angle detection device 100 and the like.

[0081] When the power supply of the DC motor 10 is turned off at the time point t0, although the time until the switching of the contacts of the switches 21 and 22 of the drive circuit 20 is completed is short, if the period until the current i at the time point t1 is reversed is assumed to be rotating at the same speed as when the DC motor 10 is turned on as described above, the rotation angle of the DC motor 10 can be calculated as follows.

[0082] Here, the period from the time point t0 when the power supply is turned off to the time point tend is divided into periods (1) and (2) to perform the calculation. The period (1) is the period from the time point t0 to the time point t1. The period (2) is the period from the time point t1 to the time point tend.

[0083] In the period (1), the rotor of the DC motor 10 is hardly subjected to braking due to the current i generated by the counter electromotive voltage. Therefore, the average of the angular velocity ω of the DC motor 10 in the period (1) is equivalent to the angular velocity ω0 immediately before the power is turned off, and it can be considered that the DC motor 10 is rotating at a constant speed. The angular velocity ω0 can be calculated on the basis of the pulse input from the pulsation detection section 122 immediately before the power is turned off. The rotation angle θ1 by which the DC motor 10 rotates in the period (1) can be found in accordance with the following equation (12).

[0084] [Equation 12]

[0085] θ1 = ω0 · (t1 - t0) (12)

[0086] In addition, in the period (2), the angular velocity of the DC motor 10 decays, but it can be considered that the angular velocity ω1 at the time point t1 which is the start point of the period (2) is equivalent to the angular velocity ω0 between the time point t1 immediately before the power is turned off. Therefore, the rotation angle θ2 by which the DC motor 10 rotates in the period (2) can be found in accordance with the equation (4) by the following equation (13).

[0087] [Equation 13]

[0088]

[0089] As described above, the rotation angle θ of the DC motor 10 in the period from the time point t0 at which the power of the DC motor 10 is turned off until the time point tend at which the current i becomes zero can be found as the total of the rotation angle θ1 in the period (1) and the rotation angle θ2 in the period (2) by the following equation (14).

[0090] [Equation 14]

[0091] θ = ω0 · (t1 - t0) + ω0 · τ (14)

[0092] In this way, the rotation angle detection device 100 can find the rotation angle θ in the period in which the DC motor 10 performs inertial rotation. Here, the rotation angle detection device 100 uses the equation (14) to find the rotation angle θ. Figure 5 The processing by which the rotation angle detection section 133B detects the rotation angle will be described. Figure 5 is a diagram showing a flowchart representing the processing by which the rotation angle detection section 133B detects the rotation angle. Figure 5 The processing shown in FIG. 13B is processing which is realized by the processing section 133 executing the rotation angle detection program of the embodiment, and is processing which is realized by the rotation angle detection method of the embodiment. More specifically, as a premise, the current measurement section 133A executes the current measurement processing of measuring the current i of the DC motor 10, and the rotation angle detection section 133B executes the rotation angle detection processing shown below.

[0093] If the processing is started, the rotation angle detection section 133B determines whether the power supply of the DC motor 10 is turned off (step S1). As a specific example, the rotation angle detection section 133B detects the turning off of the power supply of the DC motor 10 by detecting a control instruction for turning off the power supply outputted from a drive control section not shown to the drive circuit 20, and takes the time point as tO. Incidentally, as an example, the rotation angle detection section 133B can determine that the power supply of the DC motor 10 is turned off when the voltage value of the DC motor 10 inputted from the A / D converter 131 becomes zero (or a prescribed value below which the value is close to zero).

[0094] The rotation angle detection section 133B calculates the angular velocity ωO of the DC motor 10 immediately before the power supply is turned off, on the basis of the pulse converted by the pulsation detection section 122 immediately before the power supply of the DC motor 10 is turned off (step S2).

[0095] The rotation angle detection section 133B records the current i and the time (time point) measured by the current measurement section 133A from the time point tO until the current i becomes zero (until the time point tend) in the memory 133C (step S3). As a specific example, the rotation angle detection section 133B records the elapsed time from the time point tO and the current value at the time point in pairs in the memory 133C sequentially for each action of a periodic task (a task activated every constant period by a timer or the like of the microcomputer 130). In step S3, the time point tl at which the polarity of the current i is reversed, and the time point t2 at which the current i becomes a peak value are also recorded. As a specific example, the rotation angle detection section 133B sequentially checks the paired data of the elapsed time and the current value recorded in the memory 133C from the time point tO, and records the elapsed time of the time point at which the current value is zero or the polarity of the current value is reversed as tl in the memory 133C. In addition, the rotation angle detection section 133B records the elapsed time corresponding to the minimum current value among the current values of all the data as t2 in the memory 133C.

[0096] The rotation angle detection section 133B calculates the time point t4 by formula (9), and obtains the current integral value Si3+Si4 and the current integral value Si4 based on the following formulas (7), (8), respectively (step S4). Incidentally, the time point t3 is obtained by adding a prescribed time ΔT to the time point t2. The rotation angle detection section 133B stores the time point t3, the time point t4, the current integral value Si3+Si4, and the current integral value Si4 in the memory 133C.

[0097] The rotation angle detection section 133B calculates the time constant τ of the decay of the current i of the DC motor 10 based on Equation (10) (Step S5). Also, the rotation angle detection section 133B can calculate the time constant τ using Equation (11). Also, for the current i3 used in Equation (11), the rotation angle detection section 133B can simply take the current value at the time point t3 from the memory 133C as the current i3.

[0098] The rotation angle detection section 133B calculates the rotation angle θ of the DC motor 10 in the period from the time point to at which the power supply to the DC motor 10 is turned off until the time point tend at which the current i becomes zero based on Equation (14) (Step S6). With the above steps, the series of processes ends (end).

[0099] As described above, the rotation angle θ in the period in which the DC motor 10 performs inertial rotation can be calculated very simply. Also, since the time constant τ can be calculated in real time during inertial rotation using Equation (10), the problem of parameter error in the conventional method, the problem of angle accumulation error can be eliminated, and the rotation angle can be detected with very high precision. Also, for example, the precision of the rotation angle in the system including the power window 50 can be greatly improved, and the ability to cope with individual differences, environmental changes, and aging changes can be greatly improved.

[0100] Therefore, a rotation angle detection method, a rotation angle detection program, and a rotation angle detection device 100 that can calculate the rotation angle of a DC motor 10 with high precision when the DC motor 10 performs inertial rotation can be provided.

[0101] Since the rotation angle detection device 100 calculates the time constant τ of the decay of the current i based on the current during the period of inertial rotation of the DC motor 10, and infers the calculated time constant τ as the time constant τ of the decay of the angular velocity during the period of inertial rotation of the DC motor 10, to calculate the rotation angle of the DC motor 10, the rotation angle detection of the DC motor 10 can be performed simply based on the current i.

[0102] Also, the opening and closing amount of the power window 50 can be calculated based on the rotation angle θ detected by the rotation angle detection device 100. For example, when the power window 50 is stopped at a position between full opening and full closing, the opening and closing amount of the power window 50 can be calculated with high precision. The power window 50 must be provided with an anti-pinch mechanism, and when the power window 50 is opened and closed after being stopped at a position between full opening and full closing, the position at which the power window 50 is stopped needs to be accurately detected.

[0103] In addition, since the rotation angle detection device 100 can detect the rotation angle of the DC motor 10 with very high precision without using an expensive device such as a Hall IC to detect the opening / closing amount of the power window 50, the manufacturing cost can be greatly reduced.

[0104] In addition, the time constant τ of the decay of the current i is found based on the time point t3, the time point t4, the time point tend, the current integral value Si3+Si4, and the current integral value Si4. Thus, the time constant τ of the decay of the current i that can be used instead of the time constant τ of the decay of the angular velocity ω can be simply found based on the temporal change of the current i. In addition, since the integration processing for finding the current integral value corresponds to filtering processing, it has an effect of being able to remove the pulsation component contained in the current i, and the rotation angle of the DC motor 10 can be detected with very high precision.

[0105] In addition, since the time constant τ of the decay of the current i can be found based on the formula (10), the time constant τ of the decay of the current i that can be used instead of the time constant τ of the decay of the angular velocity ω can be simply found by incorporating the formula (10) into the program executed by the processing section 133. In addition, by removing the pulsation component contained in the current i according to the program executed by the processing section 133 using the filtering effect of the integration processing, the rotation angle of the DC motor 10 can be detected with very high precision. In addition, since the natural logarithm in the formula (10) includes division processing of the current integral value, the measurement error of the current of the A / D converter 132 and the like resulting from the components included in the circuit of the resistor 15, the LPF 112, and the A / D converter 132 can be reduced, and the rotation angle of the DC motor 10 can be detected with very high precision.

[0106] In addition, since the time constant τ of the decay of the current i is found based on the time point t3 and the current integral value Si3+Si4 of the current value measured by the current measurement section 133A from the time point t3 to the time point tend, the time constant τ of the decay of the current i that can be used instead of the time constant τ of the decay of the angular velocity ω can be more simply found with a smaller number of calculation times. In addition, since the integration processing for finding the current integral value corresponds to filtering processing, it has an effect of being able to remove the pulsation component contained in the current i, and the rotation angle of the DC motor 10 can be detected with high precision.

[0107] In addition, since the time constant τ of the decay of the current i can be found based on the formula (11), the time constant τ of the decay of the current i that can be used instead of the time constant τ of the decay of the angular velocity ω can be simply found by incorporating the formula (11) into the program executed by the processing section 133.

[0108] In addition, since the rotation angle in the inertial rotation of the DC motor 10 is calculated based on the angular velocity ω0before the time point t0at which the driving of the DC motor 10 is to be disconnected, the time point t1, and the time constant τ of the decay of the current i of the DC motor 10, the rotation angle in the inertial rotation of the DC motor 10 can be calculated using the time constant τ of the decay of the current i that can be used instead of the time constant τ of the decay of the angular velocity ω.

[0109] In addition, since the rotation angle in the inertial rotation of the DC motor 10 is calculated based on the angular velocity ω0before the time point t0at which the driving of the DC motor 10 is to be disconnected, the time point t1, and the time constant τ of the decay of the current i of the DC motor 10, the rotation angle in the inertial rotation of the DC motor 10 can be calculated using the time constant τ of the decay of the current i that can be used instead of the time constant τ of the decay of the angular velocity ω.

[0110] The above describes the rotation angle detection method, the rotation angle detection program, and the rotation angle detection device of the illustrative embodiment of the present application, but the present application is not limited to the specifically disclosed embodiment, and various modifications and changes can be made without departing from the technical scope.

[0111] Explanation of Reference Numerals

[0112] 10…DC motor; 11, 12…terminal; 15…resistor; 20…driving circuit; 30…DC power supply; 50…power window; 51…driving mechanism; 100…rotation angle detection device; 110…filter circuit; 111, 112…LPF; 120…IC chip; 121…BPF; 122…pulse detection section; 130…microcomputer; 131, 132…A / D converter; 133…processing section; 133A…current measurement section; 133B…rotation angle detection section; 133C…memory.

Claims

1. A method for detecting rotation angle, comprising: Current measurement processing is used to measure the current flowing through the motor; and The rotation angle detection process calculates the rotation angle of the motor based on the current value measured by the current measurement process. The rotation angle detection method is characterized in that... In the rotation angle detection process, based on the time elapsed since the polarity of the current value measured by the current measurement process reverses and the absolute value reaches its peak during the inertial rotation of the motor, and then after a predetermined time elapsed until the current value measured by the current measurement process becomes zero, the time constant of the current decay of the motor is calculated, and the rotation angle during the inertial rotation is determined based on this calculated time constant. In the rotation angle detection process, the rotation angle in the inertial rotation is calculated based on the angular velocity ω0 before the time point t0 when the drive of the motor is about to be disconnected, the time point t1 when the polarity of the current value measured by the current measurement process is reversed after the drive of the motor is disconnected at the time point t0, and the time constant τ of the current decay.

2. The rotation angle detection method according to claim 1, characterized in that, In the rotation angle detection process, the time constant τ of the current decay is calculated based on the time point t3 after the specified time, the time point tend when the current value measured by the current measurement process becomes zero, a certain time point t4 between the time point t3 and the time point tend, the first current integral value of the current value measured by the current measurement process from the time point t3 to the time point tend, and the second current integral value of the current value measured by the current measurement process from the time point t4 to the time point tend.

3. The rotation angle detection method according to claim 2, characterized in that, In the rotation angle detection process, when the first current integral value is set to Si3+Si4 and the second current integral value is set to Si4, the time constant τ of the current decay is calculated based on the following equation (1). Formula 1 4. The rotation angle detection method according to claim 1, characterized in that, In the rotation angle detection process, the time constant τ of the current decay is calculated based on the current value i3 measured by the current measurement process at time point t3 after the specified time, and the first current integral value of the current value measured by the current measurement process from time point t3 until time point tend when the current value measured by the current measurement process becomes zero.

5. The rotation angle detection method according to claim 4, characterized in that, In the rotation angle detection process, when the first current integral value is set to Si3+Si4, the time constant τ of the current decay is calculated based on the following equation (2). Formula 2 6. The rotation angle detection method according to claim 1, characterized in that, In the rotation angle detection process, the rotation angle θ in the inertial rotation of the motor is calculated based on the following equation (3). 【Formula 3】 θ=ω0·(t1-t0)+ω0·τ (3).

7. A rotation angle detection program that causes a computer to perform a process including the following: Current measurement processing, measuring the current flowing through the motor; and The rotation angle detection process calculates the rotation angle of the motor based on the current value measured by the current measurement process. The rotation angle detection program is characterized in that... In the rotation angle detection process, based on the time elapsed since the polarity of the current value measured by the current measurement process reverses and the absolute value reaches its peak during the inertial rotation of the motor, and then after a predetermined time elapsed until the current value measured by the current measurement process becomes zero, the time constant of the current decay of the motor is calculated, and the rotation angle during the inertial rotation is determined based on this calculated time constant. In the rotation angle detection process, the rotation angle in the inertial rotation is calculated based on the angular velocity ω0 before the time point t0 when the drive of the motor is about to be disconnected, the time point t1 when the polarity of the current value measured by the current measurement process is reversed after the drive of the motor is disconnected at the time point t0, and the time constant τ of the current decay.

8. A rotation angle detection device, comprising: The current measuring unit measures the current flowing through the motor; and The rotation angle detection unit calculates the rotation angle of the motor based on the current value measured by the current measuring unit. The rotation angle detection device is characterized in that... The rotation angle detection unit calculates the time constant of the motor's current decay based on the time elapsed after a predetermined period following the point when the polarity of the current value measured by the current measuring unit reverses and the absolute value reaches its peak during the inertial rotation of the motor, and then calculates the rotation angle during the inertial rotation based on the current value measured by the current measuring unit until the current value measured by the current measuring unit becomes zero. The rotation angle detection unit calculates the rotation angle in the inertial rotation based on the angular velocity ω0 before the time point t0 when the drive of the motor is about to be disconnected, the time point t1 when the polarity of the current value measured by the current measuring unit reverses after the drive of the motor is disconnected at the time point t0, and the time constant τ of the current decay.

9. The rotation angle detection device according to claim 8, characterized in that, The electric motor is the motor that drives the drive mechanism of the electric window.

Images