JP5886608B2 - Wheel rotation angle detection device - Google Patents

Description

  The present invention relates to a wheel rotation angle detection device capable of detecting a wheel rotation angle with high accuracy using an ABS signal in a vehicle having an ABS (anti-lock brake system).

  In recent years, a plurality of strain sensors are mounted on tire sidewalls at different positions in the circumferential direction of the tire, and the tire strain is simultaneously measured at a predetermined wheel rotation angle position, thereby acting on the tire from the sensor output obtained thereby. Techniques for estimating longitudinal force, lateral force, vertical force, and the like have been proposed in, for example, the following Patent Documents 1 and 2. In this technique, since the estimation formula differs for each wheel rotation angle position, it is necessary to detect the wheel rotation angle with high accuracy. For this reason, a rotary encoder or the like is separately attached to the axle side.

  However, when using a rotary encoder, etc., it is necessary to create a dedicated jig for its installation, and the detection device becomes large, which is disadvantageous in terms of cost and workability, and is restricted in terms of installation space. There is also the problem of reducing the degree of freedom.

  Therefore, it is desired to detect the wheel rotation angle using an ABS signal for ABS control used in a vehicle having an ABS.

  Here, the ABS signal is a voltage signal output from a wheel speed sensor that detects the rotational speed of the wheel, and forms an N-cycle sinusoidal waveform for each rotation of the wheel.

  Specifically, for the wheel speed sensor, generally, a rotor that is attached so as to be integrally rotatable with an axle and a magnetic sensor that is attached to face the rotor are used. The rotor has a gear shape in which a plurality of tooth portions are formed on the outer periphery thereof, or a disc shape in which a plurality of magnetic pole portions of N poles and S poles are alternately magnetized sequentially on the outer peripheral surface. The magnetic sensor detects a change in magnetic flux when each tooth portion or magnetic pole portion passes due to rotation of the rotor, and outputs it as a sinusoidal voltage signal.

  Therefore, in the ABS signal, the period N of the waveform per rotation of the wheel is positioned as the number of teeth formed in the rotor or the number of pairs of magnetic poles (N pole and S pole are paired). . However, since the rotor has a small size and a small diameter, there is a limit to the number of teeth and the like, which is conventionally set to about 48. That is, the period N of the ABS signal waveform is about 48. Therefore, when this ABS signal is used as it is as an angle signal for detecting the wheel rotation angle, only an angle signal of 7.5 degrees (= 360 degrees / 48) can be obtained. Furthermore, it becomes difficult to detect the wheel rotation angle with high accuracy of 1 degree or less.

JP 2010-215180 A JP 2010-215178 A

  Therefore, an object of the present invention is to provide a wheel rotation angle detection device that can detect a wheel rotation angle with high accuracy of, for example, 2 degrees or less, or even 1 degree or less, using an ABS signal.

In order to solve the above-mentioned problems, the invention of claim 1 of the present application is an ABS (anti-lock brake system) which is output from a wheel speed sensor for detecting the rotation speed of a wheel and forms a sine wave waveform of N cycles per one rotation of the wheel. ) A wheel rotation angle detection device that detects a wheel rotation angle using a signal,
(1) a receiver for receiving the ABS signal;
(2) a differential signal generating step for generating an ABS differential signal having a phase shift waveform in which the phase of the quarter signal is shifted from the waveform of the ABS signal by differentiating the received ABS signal with respect to time;
A first angle signal generation step of binarizing the ABS signal with the amplitude center as a threshold, and generating angle signals P1 and P2 of the binarized edge pulse for each waveform of the ABS signal;
A second angle signal generation step of binarizing the ABS differential signal with the amplitude center as a threshold and generating the angle signals P3 and P4 of the binarized edge pulse for each waveform of the ABS differential signal; Thus, for each waveform of one cycle of the ABS signal, an angle signal generator that generates an angle signal P including at least the four angle signals P1 to P4, and (3) the angle signal for each rotation of the wheel An arithmetic unit having an angle calculation unit for detecting the wheel rotation angle by counting P is provided .
The angle signal generation unit integrates the ABS differential signal and a coefficient corresponding to the rotational speed of the wheel to convert the ABS differential signal into an ABS differential signal having a constant amplitude that does not vary depending on the rotational speed of the wheel. A constant amplitude calculation step is included, and the second angle signal generation step is performed using the ABS differential signal having a constant amplitude .

In the present invention, the angle signal generator is
An absolute value signal generating step of generating a differential absolute value signal consisting of the absolute value of the constant amplitude ABS differential signal amplitude center of the constant amplitude of the ABS differential signal as 0,
Binarizing the differential absolute value signal values of the differential absolute value signal in the constant amplitude ABS phase position which gave deviated 1/8 cycle from the waveform apex of fine partial signal as a threshold value, one cycle of the ABS differential signal Performing a third angle signal generation step for generating angle signals P5 to P8 of the binarized edge pulse for each waveform of
Thereby, the angle signal generation unit generates an angle signal P composed of the eight angle signals P1 to P8 for each waveform of one cycle of the ABS signal.

According to a third aspect of the present invention , there is provided a rotation reference position comprising a reflection plate attached to the tire or wheel and rotating integrally with the tire or wheel, and an optical sensor for setting a rotation reference position for each rotation of the wheel by detecting the reflection plate. It is characterized by comprising setting means.

  Since the wheel rotation angle detection device of the present invention is configured as described above, four angle signals P1 to P1 whose phases are different from each other by ¼ period for each waveform of the ABS signal from the ABS signal. An angle signal P including P4 can be generated. Therefore, the angle detection resolution can be increased four times or more as compared with the case where the ABS signal is used as it is as an angle signal for detecting the wheel rotation angle. That is, for example, when the ABS signal has a sinusoidal waveform with 48 cycles per rotation of the wheel, the wheel rotation angle is detected with high accuracy with a resolution of at least 1.875 degrees (= 7.5 degrees / 4) or less. Is possible.

It is a conceptual diagram which shows the wheel rotation angle detection apparatus of this invention. It is a flowchart of the process in an angle signal generation part. It is a graph of an ABS signal. It is a graph which shows the shift | offset | difference of the phase of an ABS signal and an ABS differential signal. (A) is explanatory drawing which shows the production | generation of angle signals P1 and P2 by a 1st angle signal production | generation step, (B) is explanatory drawing which shows the production | generation of angle signals P3 and P4 by a 2nd angle signal production | generation step. is there. It is a graph which shows the phase of angle signal P1-P8. (A) is a graph showing the relationship between the amplitude of the ABS signal and the rotation angle of the wheel, and (B) is a graph showing the relationship between the amplitude of the ABS differential signal and the rotation angle of the wheel. It is explanatory drawing which shows the production | generation of the angle signals P5-P8 by the 3rd angle signal production | generation step.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a conceptual diagram showing a wheel rotation angle detection device 1 according to the present invention. The wheel rotation angle detection device 1 includes a receiving unit 2 that receives an ABS signal and a waveform of one cycle from the received ABS signal. An arithmetic unit 5 having an angle signal generation unit 3 that generates an angle signal P including the angle signals P1 to P4, and an angle calculation unit 4 that detects the wheel rotation angle by counting the angle signal P every rotation of the wheel. With

  The wheel rotation angle detection device 1 is further provided with a rotation reference position setting means 9 for setting a rotation reference position Qo for each rotation of the wheel, and the computing unit 5 includes the rotation reference position setting means 9. A rotation reference position signal generation unit 10 that generates a rotation reference signal for each rotation of the wheel and sends it to the angle calculation unit 4 is attached.

  The rotation reference position setting means 9 of this example includes a reflector 7 that is attached to the tire Ta or the wheel Tb and rotates integrally with the tire Ta or the wheel Tb, and a rotation reference position for each rotation of the wheel by detecting the reflector 7. And an optical sensor 8 for setting Qo. The reflection plate 7 may include a seal-like body that is attached to the tire Ta (or wheel Tb) and a printing body such as ink that is directly applied to the tire Ta (or wheel Tb). The optical sensor 8 is, for example, a light reflection type sensor. The optical sensor 8 detects that the reflecting plate 7 passes under the optical sensor 8, and sets the detection time as the rotation reference position Qo for each rotation of the wheel.

  The ABS signal is a voltage signal output from the wheel speed sensor 6 for detecting the rotational speed of the wheel T, as described above. For example, as shown in FIG. It is output as a sinusoidal waveform with amplitude in 48 cycles. As the wheel speed sensor 6, a conventional one can be suitably used.

  Next, the arithmetic unit 5 is an integrated circuit capable of arithmetic processing in which an arithmetic processing program is written, an electronic circuit board incorporating the integrated circuit, an arithmetic processing device incorporating the electronic circuit board, or the like. The receiver 2 includes an angle signal generator 3, an angle calculator 4, and a rotation reference position signal generator 10.

  The receiving unit 2 receives the ABS signal from the wheel speed sensor 6 and temporarily stores it.

In addition, the angle signal generation unit 3 is shown in the flowchart in FIG.
(A) a differential signal generation step of generating an ABS differential signal having a phase shift waveform in which the phase of the quarter signal is shifted from the waveform of the ABS signal by differentiating the received ABS signal with respect to time t;
(A) A first angle signal generation step of binarizing the ABS signal with the amplitude center as a threshold and generating the angle signals P1 and P2 of the binarized edge pulse for each waveform of the ABS signal. When,
(C) A second angle signal that binarizes the ABS differential signal with the amplitude center as a threshold value and generates the angle signals P3 and P4 of the binarized edge pulse for each waveform of the ABS differential signal. Generation step.

The angle signal generator 3 further includes:
(D) an absolute value signal creation step of creating a differential absolute value signal composed of the absolute value of the ABS differential signal with the amplitude center of the ABS differential signal set to 0;
(E) binarizing the differential absolute value signal values of the differential absolute value signal as a threshold value in the phase position which gave deviated 1/8 cycle from the waveform apex of the ABS fine minute signal, one period of the ABS differential signal The third angle signal generation step of generating the angle signals P5 to P8 of the binarized edge pulse for each waveform.

  As a result, the angle signal generation unit 3 of the present example can generate an angle signal P composed of eight angle signals P1 to P8 whose phases are different by 1/8 period for each waveform of one period of the ABS signal. The angle detection resolution can be increased by a factor of 8 compared to the case where is used as an angle signal as it is.

  In the differential signal generation step, an ABS differential signal is generated by differentiating the ABS signal with respect to time t.

Here, the ABS signal has a sinusoidal waveform with N cycles per wheel rotation, and the ABS signal V _abs can be approximated by the following equation (1).
V _abs = A × SIN (ωt + θ) + B −−− (1)
A: ABS signal amplitude B: ABS signal shift value ω: Angular velocity (ω = 2 × π × f)
t: time θ: phase f: frequency In FIG. 3, the ABS signal is shown as a corrected waveform in which the amplitude center Vo is corrected to 0 by subtracting the shift value B from the ABS signal. For this reason, in this specification, the waveform of the ABS signal, the waveform of the ABS differential signal, and the waveform of the differential absolute value signal are shown as corrected waveforms in which the amplitude center Vo of each waveform is corrected to 0, respectively.

The ABS differential signal (dV _abs / dt) represented by the following differential equation (2) can be obtained by differentiating the ABS signal V _abs shown in the equation (1) with respect to time t.
dV _abs / dt = A × ω × COS (ωt + θ)
= A × ω × SIN (ωt + θ + π / 2) −−− (2)

  As shown in FIG. 4 schematically showing the waveform of the ABS signal and the waveform of the ABS differential signal, the waveform of the ABS differential signal is π / 2, that is, a phase in which the phase of the 1/4 cycle is shifted from the waveform of the ABS signal. It can be seen that a shift waveform is formed.

  Next, in the first angle signal generation step, angle signals P1 and P2 are generated from the ABS signal for each waveform of one cycle. Specifically, as shown in FIG. 5A, the ABS signal is binarized using the amplitude center Vo as a threshold value to obtain a square wave binarized signal. Then, from the binarized signal, the positions of the rising and falling edges are detected, and a pulse signal is generated in synchronization with the edge position, whereby the binarized edge pulse as the pulse signal is generated. Are generated as angle signals P1 and P2.

  In the second angle signal generation step, angle signals P3 and P4 are generated for each waveform of the cycle from the ABS differential signal. Specifically, as shown in FIG. 5B, the ABS differential signal is binarized using the amplitude center Vo as a threshold value to obtain a square wave binarized signal. Then, the edge position that is the rising edge and the falling edge is detected from the binarized signal, and the pulse signal is generated in synchronization with the edge position, whereby the binarized edge pulse that is the pulse signal is The angle signals P3 and P4 are generated.

As described above, the ABS differential signal and the ABS signal V _abs are out of phase with each other by a quarter period. Therefore, as conceptually shown in FIG. 6, the angle signals P1 to P4 are also formed as pulse signals whose phases are shifted from each other by a quarter period, that is, one period is equally divided into four.

  Here, as shown in FIG. 7A, the ABS signal has a characteristic that its amplitude A varies depending on the rotational speed Vw of the wheel. Similarly, the ABS differential signal is also shown in FIG. As shown in B), the amplitude A × ω varies depending on the rotational speed Vw. Therefore, when the ABS differential signal is subjected to a third angle signal generation step, which will be described later, without considering the wheel rotation speed Vw, the period changes for each wheel rotation speed, resulting in an error in the angle signal. There arises a problem that the accuracy increases as the size increases.

  Therefore, a constant amplitude calculation step is performed in the angle signal generation unit 3 to convert the ABS differential signal into an ABS differential signal having a constant amplitude that does not vary depending on the rotational speed Vw of the wheel. Then, a third angle signal generation step is performed using the ABS differential signal having a constant amplitude. In this example, the ABS differential signal having the constant amplitude is also used as the ABS differential signal in the second angle signal generation step.

The constant amplitude calculation step makes the amplitude A × ω of the ABS differential signal constant by integrating the ABS differential signal and a coefficient K corresponding to the rotational speed Vw of the wheel. Specifically, the reciprocal 1 / (A × ω) of the amplitude A × ω is obtained, and the reciprocal 1 / (A × ω) is added as the coefficient K to the ABS differential signal. As shown in FIG. 7B, the amplitude A × ω has a substantially linear relationship with the rotation speed Vw. Therefore, the amplitude A × ω is expressed by the following equation (3): It can be approximated by a linear expression of the rotation speed Vw. In the formula, a and b are constants and can be obtained in advance by a preliminary test.
A × ω = a × Vw + b −−− (3)

  Accordingly, by multiplying the value of the ABS differential signal by the inverse number K of the amplitude A × ω obtained by the above equation (3), it can be converted into an ABS differential signal having a constant amplitude that does not vary with the rotational speed Vw.

  Next, an absolute value signal creation step is performed on the ABS differential signal having the constant amplitude. In this absolute value signal creation step, as shown in FIG. 8, a differential absolute value signal composed of the absolute value of the ABS differential signal having the constant amplitude is created with the amplitude center Vo of the ABS differential signal having the constant amplitude set to 0.

Also in the third angle signal generating step, as shown in the figure, the value of the differential absolute value signal in the constant amplitude ABS phase position which gave deviated 1/8 cycle from the waveform vertex J of fine minute signal M Is used as a threshold value to binarize the differential absolute value signal, thereby obtaining a square wave-like binarized signal. Then, the edge position that is the rising edge and the falling edge is detected from the binarized signal, and the pulse signal is generated in synchronization with the edge position, whereby the binarized edge pulse that is the pulse signal is The angle signals P5 to P8 are generated.

  The angle signals P5 to P8 are displaced by 1/8 period with respect to the angle signals P1 to P4 as indicated by a one-dot chain line in FIG. It is formed as a pulse signal that is phase-shifted by 8 periods, that is, equally dividing one period into eight.

  Next, the angle calculator 4 receives the rotation reference signal from the rotation reference position signal generator 10 and starts counting the angle signal P from this rotation reference signal. That is, the angle signal P can be counted for each rotation of the wheel, and the wheel rotation angle from the rotation reference position Qo can be detected. The rotation reference signal also functions as a reset signal for resetting the count number of the angle signal P counted so far.

  As described above, the wheel rotation angle detection device 1 according to the present invention has the same phase difference of ¼ period per one period of the ABS signal by the first and second angle signal generation steps by the angle signal generation unit 3. Two angle signals P1-P4 can be generated. Therefore, the angle detection resolution can be increased four times as compared with the case where the ABS signal is used as it is as an angle signal for detecting the wheel rotation angle. That is, when the ABS signal has a sinusoidal waveform with 48 cycles per rotation of the wheel, for example, the resolution can be increased to 1.875 degrees.

  In addition, as in this example, when the first to third angle signal generation steps are further performed by the angle signal generation unit 3, eight angles that are equally out of phase by 1/8 period per period of the ABS signal. Signals P1-P8 can be generated. Therefore, the angle detection resolution can be increased by a factor of eight compared to the case where the ABS signal is used as it is as an angle signal for detecting the wheel rotation angle. That is, when the ABS signal has a sinusoidal waveform with 48 cycles per rotation of the wheel, for example, the resolution can be increased to about 0.94 degrees.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

DESCRIPTION OF SYMBOLS 1 Wheel rotation angle detection apparatus 2 Reception part 3 Angle signal generation part 4 Angle calculation part 5 Calculator 6 Wheel speed sensor 7 Reflector 8 Optical sensor 9 Rotation reference position setting means T Wheel Ta Tire Tb Wheel Vw Rotation speed

Claims (3)

Wheel rotation angle detection that detects the wheel rotation angle using an ABS (anti-lock brake system) signal that is output from a wheel speed sensor that detects the rotation speed of the wheel and that has an N-cycle sinusoidal waveform for each rotation of the wheel. A device,
(1) a receiver for receiving the ABS signal;
(2) a differential signal generating step for generating an ABS differential signal having a phase shift waveform in which the phase of the quarter signal is shifted from the waveform of the ABS signal by differentiating the received ABS signal with respect to time;
A first angle signal generation step of binarizing the ABS signal with the amplitude center as a threshold, and generating angle signals P1 and P2 of the binarized edge pulse for each waveform of the ABS signal;
A second angle signal generation step of binarizing the ABS differential signal with the amplitude center as a threshold and generating the angle signals P3 and P4 of the binarized edge pulse for each waveform of the ABS differential signal; Thus, for each waveform of one cycle of the ABS signal, an angle signal generator that generates an angle signal P including at least the four angle signals P1 to P4, and (3) the angle signal for each rotation of the wheel An arithmetic unit having an angle calculation unit for detecting the wheel rotation angle by counting P is provided .
The angle signal generation unit integrates the ABS differential signal and a coefficient corresponding to the rotational speed of the wheel to convert the ABS differential signal into an ABS differential signal having a constant amplitude that does not vary depending on the rotational speed of the wheel. A wheel rotation angle detection apparatus comprising a constant amplitude calculation step, and performing the second angle signal generation step using the ABS differential signal having a constant amplitude . The angle signal generator is
An absolute value signal generating step of generating a differential absolute value signal consisting of the absolute value of the constant amplitude ABS differential signal amplitude center of the constant amplitude of the ABS differential signal as 0,
Binarizing the differential absolute value signal values of the differential absolute value signal in the constant amplitude ABS phase position which gave deviated 1/8 cycle from the waveform apex of fine partial signal as a threshold value, one cycle of the ABS differential signal Performing a third angle signal generation step for generating angle signals P5 to P8 of the binarized edge pulse for each waveform of
2. The wheel rotation angle detection according to claim 1, wherein the angle signal generation unit generates an angle signal P composed of the eight angle signals P <b> 1 to P <b> 8 for each waveform of one cycle of the ABS signal. apparatus. A rotation reference position setting means comprising a reflection plate attached to the tire or wheel and rotating integrally with the tire or wheel, and an optical sensor for setting a rotation reference position for each rotation of the wheel by detecting the reflection plate is provided. The wheel rotation angle detection device according to claim 1 or 2, characterized in that.

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