CN115224985A

CN115224985A - Rotation angle detection method, program, and rotation angle detection device

Info

Publication number: CN115224985A
Application number: CN202210361561.9A
Authority: CN
Inventors: 都军安; 陈琦婷; 木村涉; 前田亮
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 2021-04-16
Filing date: 2022-04-07
Publication date: 2022-10-21
Also published as: JP2022164441A

Abstract

The invention provides a rotation angle detection method, a rotation angle detection program and a rotation angle detection device, which can accurately obtain the rotation angle of a motor when the motor performs inertia rotation. The rotation angle detection method includes: a current measurement process of measuring a current flowing through the motor; and a rotation angle detection process of determining a rotation angle of the motor based on a current value measured by the current measurement process, wherein in the rotation angle detection process, a time constant of a decay of the current of the motor is determined based on a current value measured by the current measurement process after a predetermined time elapses from a time point when a polarity of a current value of a reverse current measured by the current measurement process is inverted and an absolute value thereof has a peak until the current value measured by the current measurement process becomes zero when the motor performs inertial rotation, and the rotation angle during the inertial rotation is determined based on the determined time constant.

Description

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

Technical Field

The invention relates to a rotation angle detection method, a rotation angle detection program, and a rotation angle detection device.

Background

Conventionally, there is an apparatus for acquiring information on rotation of a motor including a rectifier, the apparatus including: a rotation angle calculation unit that calculates a rotation angle of the motor based on an inter-terminal voltage of the motor and a current flowing through the motor; a 1 st signal generation unit configured to generate a 1 st signal based on a ripple component contained in a current flowing through the motor; a 2 nd signal generating unit configured to generate a pseudo-pulse signal as a 2 nd signal indicating that the motor has rotated by a predetermined angle, based on the 1 st signal and the rotation angle; and a rotation information calculation unit that calculates information on rotation of the motor based on an output of the 2 nd signal generation unit (see, for example, patent document 1).

Patent document 1 International publication No. 2018-123453

However, in the conventional device, the pulsation component cannot be detected with the current attenuation during the inertial rotation period after the power supply to the motor is stopped, and therefore the angle error tends to increase.

Disclosure of Invention

In view of the above, an object of the present invention is to provide a rotation angle detection method, a rotation angle detection program, and a rotation angle detection device that can accurately determine a rotation angle of a motor when the motor performs inertial rotation.

The rotation angle detection method according to the embodiment of the present invention includes: a current measurement process of measuring a current flowing through the motor; and a rotation angle detection process of obtaining a rotation angle of the motor based on the current value measured by the current measurement process, wherein the rotation angle detection process obtains a time constant of a decay of the current of the motor based on a current value measured by the current measurement process until the current value measured by the current measurement process becomes zero after a predetermined time elapses from a time point when a polarity of a current value of a reverse current measured by the current measurement process is inverted and an absolute value thereof reaches a peak value when the motor performs an inertial rotation, and obtains the rotation angle in the inertial rotation based on the obtained time constant.

Effects of the invention

A rotation angle detection method, a rotation angle detection program, and a rotation angle detection device capable of accurately determining the rotation angle of a motor when the motor is rotating by inertia.

Drawings

Fig. 1 is a diagram showing a rotation angle detection device 100 according to an embodiment.

Fig. 2 is a diagram showing a connection state between the DC motor 10 and the drive circuit 20.

Fig. 3 is a graph showing temporal changes in the current i and the angular velocity ω before and after the DC motor 10 is turned off.

Fig. 4 is a graph showing the angular velocity ω and the current i of the DC motor 10 during the period in which the DC motor 10 is performing the inertial rotation.

Fig. 5 is a flowchart showing a process of detecting the rotation angle by the rotation angle detecting unit 133B.

Detailed Description

Hereinafter, an embodiment to which the rotation angle detection method, the rotation angle detection program, and the rotation angle detection device of the present invention are applied will be described.

< embodiment >

Fig. 1 is a diagram showing a rotation angle detection device 100 according to an embodiment. The motor for detecting the rotation angle by the rotation angle detection device 100 is not limited to a motor for driving a power window of a vehicle, but here, as an example, a mode in which the rotation angle detection device 100 of the embodiment is used as a rotation angle detection device for a motor of a power window will be described.

Fig. 1 shows a DC (Direct Current) motor 10, a resistor 15, a drive circuit 20, a DC power supply 30, a power window 50, and a drive mechanism 51, in addition to the rotation angle detection device 100.

The DC motor 10 has terminals 11 and 12, and is driven by a drive circuit 20 connected to the terminals 11 and 12. A resistor 15 is connected to the terminal 12 of the DC motor 10 and is used to detect the current of the DC motor 10. The drive circuit 20 drives the DC motor 10 with DC power supplied from the DC power supply 30. The drive circuit 20 drives the DC motor 10 under control of a drive control unit, not shown, and the drive control unit is omitted here.

The power window 50 is a power window of a vehicle, and is opened and closed by a driving force transmitted from a rotor (a rotary member) of the DC motor 10 via a driving mechanism 51. The drive mechanism 51 is a mechanical mechanism such as an actuator that is provided inside a door panel of a vehicle or the like and converts a rotational force of a rotor of the DC motor 10 into a vertical drive force of the power window 50.

The rotation angle detecting apparatus 100 includes a filter Circuit 110, an IC (Integrated Circuit) chip 120, and a microcomputer 130.

The Filter circuit 110 has LPFs (Low Pass filters) 111, 112. The voltage between the terminals 11 and 12 of the DC motor 10 is input to the LPF111, and high-frequency noise and the like contained in the voltage are removed and output to the microcomputer 130. The voltage across the resistor 15 is input to the LPF112 as a voltage representing the current of the DC motor 10, and noise and the like having high frequencies included in the voltage are removed and output to the microcomputer 130.

The IC chip 120 includes a BPF (Band Pass Filter) 121 and a ripple detection unit 122. The BPF121 receives the voltage across the resistor 15 as a voltage representing the current of the DC motor 10, and removes high-frequency noise and low-frequency noise contained in the voltage, and outputs the voltage to the ripple detection unit 122. The ripple detector 122 detects ripples contained in the data indicating the current input from the BPF121, converts the ripples into pulses, and outputs the pulses to the microcomputer 130.

The microcomputer 130 includes a/D (Analog to Digital)

converters

131 and 132 and a processing unit 133. The microcomputer 130 is implemented 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 that present the function (function) of the program executed by the microcomputer 130 as a functional block.

The a/D converter 131 converts the output of the LPF111 into a digital signal and outputs the digital signal to the processing unit 133. Since the output of the LPF111 represents the voltage of the DC motor 10, the output of the a/D converter 131 is digital data representing the voltage value of the DC motor 10.

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

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 represent functions (functions) of programs executed by the microcomputer 130 as functional blocks. In addition, the memory 133C is a component that presents the memory of the microcomputer 130 as a functional module.

The current measuring unit 133A performs a current measuring process of measuring the current flowing through the DC motor 10 based on the output of the a/D converter 132. The current measuring unit 133A outputs data indicating the measured current value to the rotation angle detecting unit 133B.

The rotation angle detection unit 133B performs rotation angle detection processing for determining the rotation angle during the inertial rotation of the DC motor 10 based on the output (voltage value) of the a/D converter 131, the output (current value) of the current measurement unit 133A, and the pulse input from the pulsation detection unit 122. The inertial rotation of the DC motor 10 means that the voltage application is interrupted (the DC motor 10 is turned off) from a state in which the DC motor 10 is driven by the voltage application from the drive circuit 20 (a state in which the DC motor 10 is turned on), and the rotor of the DC motor 10 is inertially rotated by inertia. The inertial rotation of the DC motor 10 is performed when a drive control unit, not shown, controls the drive circuit 20 to cut off the voltage applied from the drive circuit 20 to the DC motor 10.

The rotation angle detection unit 133B obtains the rotation angle of the rotor of the DC motor 10 during the inertial rotation of the DC motor 10. The rotation angle of the rotor of the DC motor 10 is synonymous with the rotation angle of the DC motor 10. A specific method of determining the rotation angle will be described later with reference to fig. 2 to 5.

The memory 133C stores a program and data used when the current measuring unit 133A and the rotation angle detecting unit 133B execute the processing, an output (voltage value) of the a/D converter 131, an output (current value) of the current measuring unit 133A, data of the pulse input from the pulsation detecting unit 122, and the like.

Next, a connection state between the DC motor 10 and the drive circuit 20 will be described with reference to fig. 2. Fig. 2 is a diagram showing a connection state between the DC motor 10 and the drive circuit 20. The drive circuit 20 has two

switches

21, 22. Fig. 2 (a) shows a connection state of the drive circuit 20 for turning on the DC motor 10.

In order to turn on the DC motor 10, the

switches

21 and 22 may be switched to connect the DC motor 10 to the DC power supply 30. Fig. 2 (B) shows a connection state of the drive circuit 20 for disconnecting the DC motor 10. In order to turn off the DC motor 10, the

switches

21 and 22 may be switched to separate the DC motor 10 from the DC power supply 30. As an example, in a state where the DC motor 10 is turned off, both terminals of the DC motor 10 are connected to the negative terminal of the DC power supply 30. This is a state where the DC motor 10 is short-circuited (short).

Next, a circuit equation that holds for the DC motor 10 will be described based on the theory of the DC motor. In the DC motor 10, the following expressions (1) and (2) hold in accordance with the theory of a DC motor. L is the inductance of the DC motor 10, R is the resistance of the DC motor 10, J is the inertia of the rotor of the DC motor 10, ke is the back electromotive force constant of the DC motor 10, kt is the torque constant of the DC motor 10, kv is the viscous friction coefficient of the DC motor 10, F is the load of the DC motor 10, u is the driving voltage applied from the driving circuit 20 to the DC motor 10, and i is the current flowing through the DC motor 10 measured by the current measuring section 133A of fig. 1. The current i is a current value obtained by measuring the output of the a/D converter 132 by the current measuring unit 133A, and represents a current waveform when arranged in time series.

[ formula 1 ]

[ formula 2 ]

When the DC motor 10 is turned off, the terminals 11 and 12 of the DC motor 10 are short-circuited as shown in fig. 2 (B), so that the driving voltage u (t) =0 of the DC motor 10 and the DC motor 10 starts inertial rotation. Further, if the amount of change (di/dt) in the current i when the energy discharge of the inductor L is completed is assumed to be zero, a proportional relationship expressed by equation (3) is established between the current i and the angular velocity ω of the DC motor 10 according to equation (1). The angular velocity ω is an angular velocity of a rotating member (rotor) of the DC motor 10.

[ formula 3 ]

If the differential equation is solved by substituting equation (3) into equation (2) and assuming that the load F in the state where the terminals 11 and 12 of the DC motor 10 are short-circuited is zero, the angular velocity can be expressed by equation (4) below. Here, ω 0 is an angular velocity at which the DC motor 10 starts inertial rotation, and τ is a time constant of the decay of the angular velocity ω of the DC motor 10.

[ formula 4 ]

The time constant τ of the decay of the angular velocity ω of the DC motor 10 can be expressed by the following equation (5).

[ formula 5 ]

From equation (5), it is understood that the time constant τ is affected by variations in many parameters. As can be seen from equations (3) and (4), the angular velocity ω of the inertial rotation of the DC motor 10 decays in an exponential curve, and the current i also decays in the same exponential curve. 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.

Fig. 3 is a graph showing temporal changes in the current i and the angular velocity ω before and after the DC motor 10 is turned off. Fig. 3 (a) shows the temporal changes in the current i and the angular velocity ω before and after the DC motor 10 is turned off. When the DC motor 10 is turned off, the DC motor 10 rotates by inertia, the angular velocity ω decays exponentially, and the current i also decays exponentially after the constant period elapses. The reason why the current i is delayed with respect to the angular velocity ω is because the current flows as a result of the counter electromotive force. The current caused by the counter electromotive force is a reverse current that flows in a direction opposite to the current flowing when the DC motor 10 is turned on.

Here, when the waveform of the current i in fig. 3 (a) is set to-K times and the current i is superimposed on the angular velocity ω, the current i is superimposed on the angular velocity ω during the inertial rotation as shown in fig. 3 (B). 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 obtained from the current i using the time constant τ of the decay of 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 inertial rotation of the DC motor 10 is detected based on the obtained angular velocity ω. That is, the rotation angle detection device 100 detects the rotation angle during the inertial rotation of the DC motor 10 by estimating and using the time constant τ of the decay of the current i, which is obtained based on the current i during the inertial rotation of the DC motor 10, as the time constant τ of the decay of the angular velocity during the inertial rotation of the DC motor 10.

Next, a method of detecting the angular velocity ω based on the current i of the DC motor 10 will be described with reference to fig. 4. Fig. 4 is a graph showing the angular velocity ω and the current i of the DC motor 10 during the period in which the DC motor 10 is performing inertial rotation. Fig. 4 shows an enlarged view of the period of inertial rotation in fig. 3 (B). That is, the current i shown in fig. 4 is represented by a waveform which is-K times the waveform of the current i in fig. 3 (a).

Hereinafter, as shown in fig. 4, a method of calculating a current integration value or the like using a waveform of the current i multiplied by-K so as to overlap with the waveform of the angular velocity ω will be described, but the current i may not be multiplied by-K in actual calculation. Therefore, when describing the calculation method, the description will be made using the current i as it is.

In fig. 4, time t0 is a time at which the DC motor 10 is turned off (power supply is turned off), and is a time at which the DC motor 10 starts inertial rotation. The angular velocity ω 0 at the time point t0 is the angular velocity of the DC motor 10 immediately before the power supply is turned off. The angular velocity ω 0 can be calculated based on the pulse input from the pulsation detecting unit 122. When the power supply of the DC motor 10 is turned off, the drive circuit 20 is in a connected state shown in fig. 2 (B).

Here, a period from a time point t0 at which the DC motor 10 starts the inertial rotation to a time point tend at which the current i of the DC motor 10 becomes zero will be described. Since it can be considered that the current i becomes zero is when the rotation of the DC motor 10 is stopped, the angular velocity ω end of the DC motor 10 at the time point tend becomes zero.

The time point t1 is a time point at which the polarity of the current i is reversed. The time t1 is a time at which the value of-K times the current — Ki is inverted from negative to positive (polarity is inverted) as shown in fig. 4, and is a time at which the value of the actual current i is inverted from positive to negative (polarity is inverted). Therefore, current value i1 at time point t1 is zero.

When 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 t1 is a time point at which the polarity of the current i is inverted by the current in the opposite direction due to the counter electromotive force. The angular velocity ω 1 at the time point t1 is treated to be equal to the angular velocity ω 0. This is because the rotor of the DC motor 10 is hardly applied with a brake due to the current i in the opposite direction generated by the counter electromotive force from the time point t1 when the polarity of the current i is reversed by the counter electromotive force after the DC motor 10 is turned off.

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 t2 is a time at which the absolute value of the actual current i reaches the peak. 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 varies, the rotation angle detection unit 133B may determine that the absolute value of the current i has a peak when the current i measured by the current measurement unit 133A falls within a predetermined range. The angular velocity ω 2 at the time point t2 is attenuated more than the angular velocity ω 1 at the time point t 1. This is because the braking due to the current i in the opposite direction is applied.

The time point T3 is a time point after a predetermined time Δ T has elapsed from the time point T2 (after a predetermined time has elapsed). The predetermined time Δ T is a time (period) required from when the current-Ki takes the maximum value to when the swing width of the value of the current-Ki is stable to some extent. The predetermined time Δ T is a time (period) required from when the absolute value of the current i is obtained to when the amplitude of the fluctuation of the value of the current i is stable to some extent. For example, the predetermined time Δ T is about 1/10 of the desired time from the time T2 to the time tend at which the current i becomes zero. The data indicating the predetermined time Δ T may be stored in the memory 133C in advance.

Since the current i decays in the same exponential curve as the angular velocity ω after the elapse of the constant period from the start of the inertial rotation as described above, the current i after the time point t3 can be expressed by the following expression (6) using the current value i3 at the time point t3 according to the expression (4).

[ formula 6 ]

In fig. 4, t4 is a time point between time point t3 and time point tend at which current i becomes zero. The current integrated value of the current i from the time point t3 to the time point t4 is defined as Si3, and the current integrated value of the current i from the time point t4 to the time point tend is defined as Si4.

The rotation angle detection unit 133B obtains a current integrated value Si3+ Si4 of the current i from the time point t3 to the time point tend via the time point t4, and a current integrated value Si4 of the current i from the time point t4 to the time point tend. The current integrated value Si3+ Si4 is an example of the 1 st current integrated value, and the current integrated value Si4 is an example of the 2 nd current integrated value.

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

[ formula 7 ]

[ formula 8 ]

The integration processing of the current i by the equations (7) and (8) has a filtering effect equivalent to the filtering processing, and therefore has an effect of removing a ripple component included in the current i.

The time point t4 can be represented by the following formula (9). Kr in formula (9) is an adjustment coefficient of less than 1 (Kr < 1).

[ formula 9 ]

t4＝t3+Kr*(tend-t3) (9)

At time t4, if it is between time t3 and time tend, it may be any time, but for the sake of convenience of calculation using the current integrated values Si3 and Si4 described later, it is preferable that a certain period of time is present until time tend so that the current integrated value Si4 is not too small, and that the current integrated value Si3 and the current integrated value Si4 are set to be unequal.

The time constant τ of the decay of the current i of the DC motor 10 can be obtained from the equations (7) and (8) as shown in the equation (10) below. 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 obtained instead of the time constant of the decay of the angular velocity of the DC motor 10.

[ formula 10 ]

Since the natural logarithm in equation (10) includes the division processing of (Si 3+ Si 4)/Si 4, an effect of reducing measurement errors of the current of the a/D converter 132 and the like derived from the components included in the circuit such as the resistor 15, the LPF112, and the a/D converter 132 can be obtained.

Instead of equation (10), the time constant τ of the decay of the current i of the DC motor 10 may be directly obtained from equation (7) as in equation (11) below.

[ formula 11 ]

When the time constant τ is calculated using the equation (11), the number of calculations is smaller and simpler than when the time constant τ is calculated using the equation (10), but since the current i3 is used, the time constant τ is more susceptible to a ripple component and a measurement error than the time constant τ calculated using the equation (10). Therefore, it is sufficient to determine which of equations (10) and (11) is used, depending on the application of the rotation angle detection device 100 and the like.

After the power supply of the DC motor 10 is turned off at time t0, the time until the switching of the contact points of the

switches

21 and 22 of the drive circuit 20 is completed is short, but if the rotation at the same speed as that at the time when the DC motor 10 is turned on is assumed to be performed before the current i is reversed at time t1 as described above, the rotation angle of the DC motor 10 can be obtained as follows.

Here, the period from the time t0 when the power is turned off to the time tend is divided into periods (1) and (2) for calculation. The period (1) is a period from the time point t0 to the time point t 1. The period (2) is a period from the time point t1 to the time point tend.

In the period (1), the rotor of the DC motor 10 is hardly applied with a brake due to the current i generated by the counter electromotive force. Therefore, the average of the angular velocity ω of the DC motor 10 in the period (1) is equivalent to the angular velocity ω 0 immediately before the power supply is turned off, and it can be considered that the DC motor 10 is rotating at a constant velocity. The angular velocity ω 0 can be calculated based on the pulse input from the pulsation detecting section 122 immediately before the power supply is turned off. The rotation angle θ 1 at which the DC motor 10 rotates in the period (1) can be obtained from the following equation (12).

[ formula 12 ]

θ1＝ω0·(t1-t0) (12)

In the period (2), the angular velocity of the DC motor 10 is attenuated, but the angular velocity ω 1 at the time point t1 which is the start point of the period (2) can be considered to be equal to the angular velocity ω 0 immediately before the time point t 1. Therefore, the rotation angle θ 2 at which the DC motor 10 rotates in the period (2) can be obtained from the following expression (13) based on the expression (4).

[ formula 13 ]

As described above, the rotation angle θ of the DC motor 10 during the period from the time point t0 when the power supply of the DC motor 10 is turned off to the time point tend when the current i becomes zero can be obtained as the total angle of the rotation angle θ 1 during the period (1) and the rotation angle θ 2 during the period (2) by the following equation (14).

[ formula 14 ]

θ＝ω0·(t1-t0)+ω0·τ (14)

In this way, the rotation angle detection device 100 can determine the rotation angle θ during the period in which the DC motor 10 performs inertial rotation. Here, the process of detecting the rotation angle by the rotation angle detecting unit 133B will be described with reference to fig. 5. Fig. 5 is a flowchart showing a process of detecting the rotation angle by the rotation angle detecting unit 133B. The processing shown in fig. 5 is realized by the processing unit 133 executing the rotation angle detection program according to the embodiment, and is realized by the rotation angle detection method according to the embodiment. More specifically, as a premise, the current measuring unit 133A performs a current measuring process of measuring the current i of the DC motor 10, and the rotation angle detecting unit 133B performs a rotation angle detecting process described below.

When the process is started, the rotation angle detection unit 133B determines whether or not the power supply of the DC motor 10 is turned off (step S1). Specifically, the circuit angle detection unit 133B detects the power-off of the DC motor 10 by detecting a power-off control command output to the drive circuit 20 from a drive control unit, not shown, and sets the time point as t0. As an example, the rotation angle detection unit 133B may determine that the power supply of the DC motor 10 is turned off when the voltage value of the DC motor 10 input from the a/D converter 131 becomes zero (or a predetermined value or less close to zero).

The rotation angle detection unit 133B calculates an angular velocity ω 0 immediately before the power supply of the DC motor 10 is turned off, based on the pulse converted by the pulsation detection unit 122 immediately before the power supply of the DC motor 10 is turned off (step S2).

The rotation angle detection unit 133B records the current i measured by the current measurement unit 133A from the time point t0 until the current i becomes zero (until the time point tend) and the time (time point) in the memory 133C (step S3). Specifically, the rotation angle detection unit 133B sequentially records the elapsed time from the time point t0 and the current value at the time point in pairs in the memory 133C for each operation of a periodic task (a task started at each constant period by a timer or the like of the microcomputer 130). In step S3, a time point t1 when the polarity of the current i is inverted and a time point t2 when the current i becomes a peak are also recorded. Specifically, the rotation angle detection unit 133B checks pairs of the elapsed time and the current value recorded in the memory 133C in order from the time point t0, and records the elapsed time at the time point when the current value is zero or the polarity of the current value is inverted in the memory 133C as t 1. The rotation angle detection unit 133B records the elapsed time corresponding to the minimum current value among the current values of all the data in the memory 133C as t2.

The rotation angle detection unit 133B calculates the time point t4 by equation (9), and obtains the current integrated value Si3+ Si4 and the current integrated value Si4 based on equations (7) and (8) below, respectively (step S4). Here, the time T3 is obtained by adding a predetermined time Δ T to the time T2. The rotation angle detection unit 133B stores the time point t3, the time point t4, the current integrated value Si3+ Si4, and the current integrated value Si4 in the memory 133C.

The rotation angle detection unit 133B obtains the time constant τ of the decay of the current i of the DC motor 10 based on the equation (10) (step S5). The rotation angle detection unit 133B may calculate the time constant time τ using equation (11). In addition, the current i3 used in equation (11) may be obtained by the rotation angle detecting unit 133B from the memory 133C as the current i3 at the time point t3.

The rotation angle detection unit 133B obtains the rotation angle θ of the DC motor 10 during a period from the time t0 when the power supply of the DC motor 10 is turned off to the time tend when the current i becomes zero, based on the equation (14) (step S6). Through the above steps, a series of processes ends (end).

As described above, the rotation angle θ during the period in which the DC motor 10 performs the inertial rotation can be very easily obtained. Further, since the time constant τ can be obtained in real time during the inertial rotation by equation (10), the problem of parameter error and the problem of accumulated angle error in the conventional technique can be solved, and the rotation angle can be detected with very high accuracy. In addition, for example, the accuracy of the rotation angle in the system including the power window 50 can be greatly improved, and the capability of coping with individual differences, environmental changes, and aging changes can be greatly improved.

Therefore, it is possible to provide the rotation angle detection method, the rotation angle detection program, and the rotation angle detection device 100 that can accurately determine the rotation angle of the DC motor 10 when the DC motor 10 is performing the inertial rotation.

Since the rotation angle detection device 100 obtains the time constant τ of the decay of the current i based on the current during the inertial rotation of the DC motor 10, and estimates the obtained time constant τ as the time constant τ of the decay of the angular velocity during the inertial rotation of the DC motor 10 to obtain the rotation angle of the DC motor 10, it is possible to easily detect the rotation angle of the DC motor 10 based on the current i.

Further, the opening/closing amount of power window 50 can be calculated based on rotation angle θ detected by rotation angle detection device 100. For example, when the power window 50 is stopped at a position between the fully open position and the fully closed position, the opening/closing amount of the power window 50 can be accurately determined. The power window 50 must be provided with an anti-pinch mechanism, and when the power window 50 is stopped at a position between the fully open position and the fully closed position and then opened and closed, the position at which the power window 50 is stopped needs to be accurately detected.

Further, since the rotation angle detection device 100 can detect the rotation angle of the DC motor 10 with very high accuracy 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.

The time constant τ of the decay of the current i is obtained based on the time point t3, the time point t4, the time point tend, the current integrated value Si3+ Si4, and the current integrated value Si4. Therefore, the time constant τ of the decay of the current i, which can be used instead of the time constant τ of the decay of the angular velocity ω, can be easily obtained based on the temporal change of the current i. Further, since the integration process for obtaining the current integration value corresponds to the filter process, the ripple component included in the current i can be removed, and the rotation angle of the DC motor 10 can be detected with very high accuracy.

Since the time constant τ of the decay of the current i can be obtained based on the equation (10), the time constant τ of the decay of the current i, which can be used in place of the time constant τ of the decay of the angular velocity ω, can be easily obtained by incorporating the equation (10) into the program executed by the processing unit 133. Further, the ripple component included in the current i is removed by the filter effect of the integration processing according to the program executed by the processing unit 133, and the rotation angle of the DC motor 10 can be detected with very high accuracy. Since the natural logarithm in expression (10) includes a division process of the current integration value, it is possible to reduce a measurement error of the current of the a/D converter 132 and the like, which is derived from components included in the circuits such as the resistor 15, the LPF112, and the a/D converter 132, and to detect the rotation angle of the DC motor 10 with very high accuracy.

Further, since the time constant τ of the decay of the current i is obtained based on the time point t3 and the current integral value Si3+ Si4 of the current value measured by the current measuring unit 133A from the time point t3 to the time point tend, the time constant τ of the decay of the current i, which can be used instead of the time constant τ of the decay of the angular velocity ω, can be obtained more easily with a small number of calculations. Further, since the integration process for obtaining the current integration value corresponds to the filter process, the ripple component included in the current i can be removed, and the rotation angle of the DC motor 10 can be detected with high accuracy.

Since the time constant τ of the decay of the current i can be obtained based on the equation (11), the time constant τ of the decay of the current i, which can be used in place of the time constant τ of the decay of the angular velocity ω, can be easily obtained by incorporating the equation (11) into the program executed by the processing unit 133.

Further, since the rotation angle in the inertial rotation of the DC motor 10 is obtained based on the angular velocity ω 0 immediately before the time point t0 at which the drive of the DC motor 10 is turned off, 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 obtained using the time constant τ of the decay of the current i that is used in place of the time constant τ of the decay of the angular velocity ω.

Further, since the rotation angle during the inertial rotation of the DC motor 10 is obtained based on the equation (14), by incorporating the equation (14) into the program executed by the processing unit 133, the rotation angle during the inertial rotation of the DC motor 10 can be obtained using the time constant τ of the decay of the current i, which can be used instead of the time constant τ of the decay of the angular velocity ω.

The rotation angle detection method, the rotation angle detection program, and the rotation angle detection device according to the exemplary embodiments of the present invention have been described above, but the present invention is not limited to the specifically disclosed embodiments, and various modifications and changes can be made without departing from the scope of the present invention.

Description of reference numerals

10 … DC motor; 11. a 12 … terminal; 15 … resistor; 20 … driver circuit; 30 … dc supply; 50 … power window; a 51 … drive mechanism; 100 … rotation angle detection device; 110 … filter circuit; 111. 112 … LPF;120 … IC chip; 121 … BPF;122 … pulsation detecting section; 130 … microcomputer; 131. 132 … a/D converter; 133 …;133A … current measuring part; 133B … rotation angle detection unit; 133C … memory.

Claims

1. A rotation angle detection method comprising:

a current measurement process of measuring a current flowing through the motor; and

a rotation angle detection process of obtaining a rotation angle of the motor based on the current value measured by the current measurement process,

the method for detecting a rotation angle is characterized in that,

in the rotation angle detection process, a time constant of a decay of the current of the motor is obtained based on a current value measured by the current measurement process until a current value measured by the current measurement process becomes zero after a predetermined time elapses from a time point when a polarity of a current value of a reverse current measured by the current measurement process is inverted and an absolute value thereof has a peak value when the motor performs inertial rotation, and the rotation angle during the inertial rotation is obtained based on the obtained time constant.

2. The rotation angle detecting method according to claim 1,

in the rotation angle detection process, the time constant τ of the decay of the current is obtained based on a time point t3 after the predetermined time has elapsed, a time point tend at which 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, a 1 st current integrated value of the current value measured by the current measurement process from the time point t3 to the time point tend, and a 2 nd current integrated 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,

in the rotation angle detection process, the time constant τ of the decay of the current is obtained based on the following equation (1) when the 1 st current integrated value is Si3+ Si4 and the 2 nd current integrated value is Si4,

[ formula 1 ]

4. The rotation angle detecting method according to claim 1,

in the rotation angle detection process, the time constant τ of the decay of the current is obtained based on the current value i3 measured by the current measurement process at the time point t3 after the predetermined time has elapsed and the 1 st current integrated value of the current value measured by the current measurement process from the time point t3 to the time point tend at which the current value measured by the current measurement process becomes zero.

5. The rotation angle detecting method according to claim 4,

in the rotation angle detection process, the time constant τ of the decay of the current is obtained based on the following expression (2) assuming that the 1 st current integrated value is Si3+ Si4,

[ formula 2 ]

6. The rotation angle detection method according to any one of claims 1 to 5,

in the rotation angle detection process, the rotation angle during the inertial rotation is determined based on an angular velocity ω 0 immediately before a time point t0 at which the drive of the motor is turned off, a time point t1 at which the polarity of a current value measured by the current measurement process is reversed after the drive of the motor is turned off at the time point t0, and a time constant τ of the decay of the current.

7. The rotation angle detection method according to claim 6,

in the rotation angle detection process, the rotation angle in the inertial rotation of the motor is determined based on the following expression (3),

[ formula 3 ]

θ＝ω0·(t1-t0)+ω0·τ (3)。

8. A rotation angle detection program that causes a computer to execute processing including:

the rotation angle detection program is characterized in that,

9. A rotation angle detecting device comprising:

a current measuring unit for measuring a current flowing through the motor; and

a rotation angle detection unit for determining a rotation angle of the motor based on the current value measured by the current measurement unit,

the rotation angle detection device is characterized in that,

the rotation angle detection unit obtains a time constant of the decay of the current of the motor based on the current value measured by the current measurement unit until the current value measured by the current measurement unit becomes zero after a predetermined time elapses from the time point at which the polarity of the current value of the reverse current measured by the current measurement unit is inverted and the absolute value thereof has acquired the peak value when the motor performs the inertial rotation, and obtains the rotation angle during the inertial rotation based on the obtained time constant.

10. The rotation angle detecting device according to claim 9,

the motor is a motor that drives a drive mechanism of a power window.