JP4636230B2 - Wheel load estimation device and wheel load estimation method - Google Patents

Description

  The present invention acquires wheel speed data based on a signal output from a wheel speed sensor provided on a wheel, and wheel load of the wheel based on a frequency component of vibration having a resonance frequency included in the wheel speed data. The present invention relates to a wheel load estimation device and a wheel load estimation method.

When the vehicle travels on the road surface, the tire vibrates due to the unevenness of the road surface. This vibration is transmitted to the wheel via the tire. When a wheel vibrates, two forces are applied to the wheel axle. One is a force generated when the sidewall portion of the tire is twisted. The other is the force generated by the deformation of the bush in the front-rear direction of the suspension provided to absorb the vibration in the front-rear direction of the vehicle body.
The force thus generated changes the rotational speed of the wheel. As a result, a signal corresponding to the rotational speed of the wheel detected by the wheel speed sensor attached to the wheel is referred to as vibration generated by twisting of the sidewall portion of the tire (hereinafter referred to as tire torsional resonance vibration). ) And frequency characteristics based on the characteristics of vibrations generated by deformation of the bush in the longitudinal direction of the suspension (hereinafter referred to as suspension longitudinal vibrations) (hereinafter also referred to as vibration amplitude or vibration gain). ) Will be included.

In fact, when the wheel speed calculated from the wheel speed data obtained based on the signal is frequency-analyzed, the frequency component of vibration having each frequency generally has three peaks within a frequency range of 100 Hz. .
Among these, as shown in FIG. 1, the peak of the vibration gain that appears in the region where the frequency is around 30 to 50 Hz is based on the torsional resonance vibration of the tire. The resonance frequency related to this peak is hereinafter referred to as “tire torsional resonance frequency”.
Further, the peak of the vibration gain appearing in the region where the frequency is around 10 to 20 Hz is based on the resonance vibration in the longitudinal direction of the suspension. Hereinafter, the resonance frequency related to this peak is referred to as “suspension longitudinal resonance frequency”.

  By the way, it can be considered that tires, wheels, and the like constitute a spring-mass system, as schematically shown in FIGS. 2 (a) and 2 (b). When the wheel load of the wheel (that is, the force by which the wheel including the tire pushes the road surface) is large, the ground contact area of the tire is large as shown in FIG. Accordingly, a grip force sufficient to receive a spring reaction force corresponding to the torsional resonance vibration of the tire can be generated between the tire and the road surface. As a result, as indicated by the solid line in FIG. 3A, the vibration gain of the torsional resonance vibration of the tire increases.

  On the other hand, when the wheel load of the wheel is small, the ground contact area of the tire is small as shown in FIG. For this reason, a grip force sufficient to receive the spring reaction force is not generated between the tire and the road surface. As a result, as indicated by the dotted line in FIG. 3A, the vibration gain of the torsional resonance vibration of the tire is smaller than that when the wheel load of the wheel is large. Thus, there is a certain correlation between the torsional resonance vibration of the tire and the wheel load of the wheel.

The vehicle control apparatus described in Patent Document 1 utilizes this correlation, and each vibration gain of the resonance frequency of the tire corresponds to the wheel load (wheel load) of each wheel. The wheel load or the vehicle body load of the wheel is estimated.
Japanese Patent Publication No. 11-028172 (International Publication No. WO99 / 28172, pages 17 to 20, FIG. 4)

  However, the vibration gain having the torsional resonance frequency of the tire not only fluctuates depending on the ground contact area due to the wheel load, but also due to changes in road surface irregularities (changes in road surface input) as shown in FIG. Change. Further, the vibration gain having the torsional resonance frequency also changes depending on changes in the internal pressure of the tire and the internal temperature of the tire, as shown in FIGS. 3 (c) and 3 (d).

  Therefore, according to the conventional vehicle control device that estimates the wheel load based only on the vibration gain having the torsional resonance frequency of the tire without considering the internal pressure of the tire, etc., the wheel load of the wheel is estimated incorrectly. There was a problem of being.

  An object of the present invention is to acquire wheel speed data based on a signal output from a wheel speed sensor, and use a frequency component of vibration having a torsional resonance frequency included in the wheel speed data as various parameters such as tire internal pressure. The frequency component of the vibration obtained when the various parameters are in a constant reference state is obtained, and the wheel load of the wheel is estimated from the frequency component of the vibration, thereby affecting the frequency component of the vibration. An object of the present invention is to provide an apparatus for accurately estimating the wheel load of a wheel in consideration of factors.

The wheel load estimation device according to the present invention is:
A wheel speed sensor that outputs a signal corresponding to the rotational speed of the wheel including the tire;
Wheel speed data acquisition means for acquiring wheel speed data corresponding to the rotational speed of the wheel based on the signal output from the wheel speed sensor;
A torsional resonance amplitude extracting means (torsional resonance frequency component extracting means) for extracting the amplitude of the vibration having the torsional resonance frequency of the tire from the amplitude ( frequency component ) of vibration included in the acquired wheel speed data;
Tire pressure detecting means for detecting the internal pressure of the tire;
Calculating a tire pressure correction value corresponding to a difference between a reference internal pressure of a given tire and the detected internal pressure of the tire, and using the tire pressure correction value, the vibration having the extracted torsional resonance frequency is calculated. a torsional resonance amplitude correction means for correcting the amplitude (torsional resonance frequency component correction means),
Storage means for storing the relationship between the amplitude of vibration having a reference torsional resonance frequency obtained when the internal pressure of the tire is the reference internal pressure and the wheel load of the wheel;
Wheel load estimating means for estimating the wheel load on the basis of the amplitude of vibration having the corrected torsional resonance frequency and the relationship stored in the storage means.

  The wheel speed data obtained based on the signal output from the wheel speed sensor includes a vibration frequency component having a torsional resonance frequency. The frequency component of the vibration having the torsional resonance frequency changes with a change in the internal pressure of the tire. Considering this relationship, the wheel load estimation device according to the present invention calculates a tire pressure correction value according to the difference between the reference internal pressure of a given tire and the internal pressure of the tire, and uses the correction value. The frequency component of the vibration having the extracted torsional resonance frequency is corrected. As a result, the frequency component of vibration having the torsional resonance frequency is the frequency component of vibration (reference torsional resonance frequency obtained when the internal pressure of the tire is the reference internal pressure, regardless of the internal pressure state of the tire. Frequency component of vibration).

  Further, there is a certain correlation between the vibration frequency component having the reference torsional resonance frequency and the wheel load of the wheel. In consideration of this relationship, the present apparatus estimates the wheel load of the wheel from the corrected frequency component of the vibration. As a result, the influence of the internal pressure of the tire on the frequency component of the vibration having the torsional resonance frequency is eliminated, so that the wheel load of the wheel can be estimated more accurately.

The wheel load estimation device according to the present invention further includes:
Suspension longitudinal resonance amplitude extraction means (suspension longitudinal resonance resonance) for extracting vibration amplitude having " suspension longitudinal resonance frequency smaller than the torsional resonance frequency of the tire" from vibration amplitude included in the acquired wheel speed data Frequency component extraction means)
The torsional resonance amplitude correcting means is
Calculated amplitude correction value corresponding to the difference between the amplitude of the vibration having an amplitude and the extracted suspension longitudinal direction resonance frequency of the vibration having a given reference suspension longitudinal direction resonance frequency (frequency component correction value), the same amplitude Further correcting the amplitude of vibration having the corrected torsional resonance frequency using a correction value,
Relationship stored in the storage means is a relational obtained when the amplitude of the vibration having a suspension longitudinal direction resonance frequency is the amplitude of the vibration having the reference suspension longitudinal direction resonant frequency,
The wheel load estimating means includes
The wheel load is estimated based on the amplitude of vibration having a torsional resonance frequency further corrected using the amplitude correction value and the relationship stored in the storage means.

  The frequency component of vibration having a torsional resonance frequency also changes with changes in road surface input. The change in the road surface input appears as a change in the frequency component of the vibration having the suspension longitudinal resonance frequency included in the wheel speed data. Therefore, it can be considered that the frequency component of the vibration having the torsional resonance frequency changes as the frequency component of the vibration having the suspension longitudinal resonance frequency changes.

  In view of this relationship, the apparatus corrects the frequency component corresponding to the difference between the frequency component of vibration having a given reference suspension longitudinal resonance frequency and the frequency component of vibration having the extracted suspension longitudinal resonance frequency. A value is calculated, and the frequency component of the vibration having the torsional resonance frequency already corrected by the tire pressure correction value is further corrected using the correction value. As a result, the vibration frequency component having the torsional resonance frequency is the reference internal pressure, regardless of the road surface condition, and the vibration frequency component having the extracted suspension longitudinal resonance frequency is the reference suspension. The frequency component of vibration (frequency component of vibration having a reference torsional resonance frequency) obtained when the frequency component of vibration having a longitudinal resonance frequency is approached.

  Further, there is a certain correlation between the vibration frequency component having the reference torsional resonance frequency and the wheel load of the wheel. In consideration of this relationship, the present apparatus estimates the wheel load of the wheel from the frequency component of the vibration having the torsional resonance frequency further corrected by the frequency component correction value. As a result, the influence of the road surface unevenness on the frequency component of the vibration having the torsional resonance frequency together with the internal pressure of the tire is eliminated, so that the wheel load of the wheel can be estimated more accurately.

The wheel load estimation device according to the present invention further includes:
Tire temperature detecting means for detecting the internal temperature of the tire,
The torsional resonance amplitude correcting means is
Calculating a tire temperature correction value corresponding to a difference between a reference internal temperature of a given tire and the detected internal temperature of the tire, and using the tire temperature correction value, the vibration having the corrected torsional resonance frequency is calculated. Further correct the amplitude ,
The relationship stored in the storage means is a relationship obtained when the internal temperature of the tire is the reference internal temperature,
The wheel load estimating means includes
The wheel load is estimated based on the amplitude of vibration having a torsional resonance frequency further corrected using the tire temperature correction value and the relationship stored in the storage means.

  The frequency component of vibration having a torsional resonance frequency also changes with changes in the internal temperature of the tire. In consideration of this relationship, this device calculates a tire temperature correction value according to the difference between the reference internal temperature of a given tire and the internal temperature of the tire, and has already corrected the tire pressure using the tire temperature correction value. The frequency component of the vibration having the torsional resonance frequency corrected by the value and the frequency component correction value is further corrected. As a result, the frequency component of the vibration having the torsional resonance frequency is not limited to the internal temperature of the tire, and the vibration obtained at the reference internal pressure, the frequency component of the vibration having the reference suspension longitudinal resonance frequency, and the reference internal temperature. It approaches a frequency component (frequency component of vibration having a reference torsional resonance frequency).

  Further, there is a certain correlation between the vibration frequency component having the reference torsional resonance frequency and the wheel load of the wheel. In consideration of this relationship, the present apparatus estimates the wheel load of the wheel from the frequency component of the vibration having the torsional resonance frequency further corrected by the tire temperature correction value. As a result, the influence of the internal temperature of the tire and the unevenness of the road surface on the frequency component of the vibration having the torsional resonance frequency as well as the internal temperature of the tire is eliminated, so that the wheel load of the wheel can be estimated more accurately.

The wheel load estimation device according to the present invention is:
A wheel speed sensor that outputs a signal corresponding to the rotational speed of the wheel including the tire;
Wheel speed data acquisition means for acquiring wheel speed data corresponding to the rotational speed of the wheel based on the signal output from the wheel speed sensor;
A torsional resonance amplitude extracting means (resonant frequency component extracting means) for extracting a frequency component of vibration having a torsional resonance frequency of the tire from the amplitude of vibration included in the acquired wheel speed data;
Suspension longitudinal resonance amplitude extraction means (suspension longitudinal resonance frequency component extraction means) for extracting the vibration amplitude having the suspension longitudinal resonance frequency from the vibration amplitude included in the acquired wheel speed data;
Calculated amplitude correction value corresponding to the difference between the amplitude of the vibration having an amplitude and the extracted suspension longitudinal direction resonance frequency of the vibration having a given reference suspension longitudinal direction resonance frequency (frequency component correction value), the same amplitude Torsional resonance amplitude correction means (resonance frequency component correction means) for correcting the amplitude of vibration having the extracted torsional resonance frequency using a correction value;
Storing the amplitude of the vibration having a suspension longitudinal direction resonant frequency stores the relationship between the amplitude and the wheel wheel load of the vibration with reference torsional resonance frequency obtained when the amplitude of the oscillation having the reference suspension longitudinal direction resonant frequency Means,
Wheel load estimating means for estimating the wheel load on the basis of the amplitude of vibration having the corrected torsional resonance frequency and the relationship stored in the storage means.

  As described above, the frequency component of the vibration having the torsional resonance frequency changes in accordance with the change of the frequency component of the vibration having the suspension longitudinal resonance frequency. Further, the vibration frequency component having the reference torsional resonance frequency obtained when the vibration frequency component having the suspension longitudinal resonance frequency is the frequency component of the vibration having the reference suspension longitudinal resonance frequency and the wheel load of the wheel. Have a certain correlation. In consideration of these relationships, the apparatus corrects the frequency component of the vibration having the torsional resonance frequency extracted using the frequency component correction value, and calculates the wheel load of the wheel from the corrected frequency component of the vibration. presume. As a result, the influence of the road surface unevenness on the frequency component of the vibration having the torsional resonance frequency is eliminated, so that the wheel load of the wheel can be estimated more accurately.

The wheel load estimation device according to the present invention further includes:
Outside temperature detecting means for detecting outside temperature;
An outside air temperature correction value corresponding to a difference between a given reference outside air temperature and the detected outside air temperature is calculated, and the amplitude of vibration having the extracted longitudinal resonance frequency of the suspension is extracted using the outside air temperature correction value. Suspension longitudinal resonance amplitude correction means for correcting (suspension longitudinal resonance frequency component correction means) ,
The torsional resonance amplitude correcting means is
Using the amplitude of the vibration with the outside air temperature correction value suspension longitudinal direction resonant frequency corrected using as the amplitude of the oscillation having the extracted suspension longitudinal direction resonant frequency used when calculating the amplitude correction value ,
The relationship stored in the storage means is
The amplitude of the vibration having a suspension longitudinal direction resonant frequency, a relationship obtained when the amplitude of the oscillation having the reference suspension longitudinal direction resonant frequency when the outside air temperature is the reference outside air temperature.

  The frequency component of vibration having the longitudinal resonance frequency of the suspension changes as the outside air temperature changes. In consideration of this relationship, the device calculates an outside air temperature correction value corresponding to a difference between a given reference outside air temperature and the detected outside air temperature, and the suspension longitudinal resonance extracted using the correction value. A frequency component of vibration having a frequency is corrected. As a result, the frequency component of vibration at the suspension longitudinal resonance frequency approaches the frequency component of vibration having the reference suspension longitudinal resonance frequency obtained when the outside air temperature is the reference outside temperature, regardless of the outside air temperature.

  In addition, the reference torsional resonance frequency obtained when the vibration frequency component having the suspension longitudinal resonance frequency is the frequency component of the vibration having the reference suspension longitudinal resonance frequency when the outside air temperature is the reference outside air temperature. There is a certain correlation between the frequency component of vibration and the wheel load of the wheel. In consideration of this relationship, the apparatus estimates the wheel load of the wheel from the vibration frequency component having the torsional resonance frequency corrected based on the vibration frequency component having the corrected suspension longitudinal resonance frequency. As a result, the influence of the road surface unevenness on the frequency component of the vibration having the torsional resonance frequency is eliminated regardless of the outside air temperature, so that the wheel load of the wheel can be estimated more accurately.

The wheel load estimation device according to the present invention further includes:
Tire temperature detecting means for detecting the internal temperature of the tire,
The torsional resonance amplitude correcting means is
Calculating a tire temperature correction value corresponding to a difference between a reference internal temperature of a given tire and the detected internal temperature of the tire, and using the tire temperature correction value, the vibration having the corrected torsional resonance frequency is calculated. Further correct the amplitude ,
The relationship stored in the storage means is a relationship obtained when the internal temperature of the tire is the reference internal temperature,
The wheel load estimating means includes
The wheel load is estimated based on the amplitude of vibration having a torsional resonance frequency further corrected using the tire temperature correction value and the relationship stored in the storage means.

  As described above, the frequency component of vibration having a torsional resonance frequency changes with a change in the internal temperature of the tire. Further, the vibration frequency component having the suspension longitudinal resonance frequency is the vibration frequency component having the reference suspension longitudinal resonance frequency when the outside air temperature is the reference outside temperature, and the tire internal temperature is the reference internal temperature. There is a certain correlation between the “frequency component of vibration having the reference torsional resonance frequency and the wheel load of the wheel” obtained when In consideration of these relationships, this device further corrects the frequency component of the vibration having the torsional resonance frequency already corrected by the frequency component correction value by using the tire temperature correction value, and the corrected frequency of the same vibration. The wheel load of the wheel is estimated from the component. As a result, the wheel load of the wheel is estimated more accurately.

The wheel load estimation method according to the present invention includes:
Wheel speed data corresponding to the rotation speed of the wheel is acquired based on a signal corresponding to the rotation speed of the wheel including the tire output from the wheel speed sensor,
Extracting the vibration amplitude having the torsional resonance frequency of the tire from the vibration amplitude (frequency component) included in the acquired wheel speed data,
Obtaining the internal pressure of the tire output from the pressure sensor;
Calculating a tire pressure correction value corresponding to a difference between a reference internal pressure of a given tire and the acquired internal pressure of the tire, and using the tire pressure correction value, the vibration having the extracted torsional resonance frequency is calculated. Correct the amplitude ,
The basis of the relationship between the wheel load amplitude and wheel vibration with reference torsional resonance frequency obtained when the internal pressure of the tire is the reference internal pressure, the amplitude of the vibration having said corrected torsional resonance frequency, the This is a method for estimating the wheel load.

  As described above, the frequency component of the vibration having the torsional resonance frequency changes with a change in the internal pressure of the tire. Further, there is a certain correlation between the vibration frequency component having the reference torsional resonance frequency obtained when the tire internal pressure is the reference internal pressure and the wheel load of the wheel. In consideration of these correlations, the wheel load estimation method according to the present invention corrects the frequency component of vibration having the extracted torsional resonance frequency by the tire pressure correction value, and corrects the frequency component of the corrected vibration. To estimate the wheel load of the wheel. As a result, the influence of the internal pressure of the tire on the frequency component of the vibration having the torsional resonance frequency is eliminated, so that the wheel load of the wheel can be estimated more accurately.

Further, the wheel load estimation method according to the present invention includes:
Wheel speed data corresponding to the rotation speed of the wheel is acquired based on a signal corresponding to the rotation speed of the wheel including the tire output from the wheel speed sensor,
Extracting the vibration amplitude having the torsional resonance frequency of the tire from the vibration amplitude (frequency component) included in the acquired wheel speed data,
Extracting the amplitude of vibration having a " suspension longitudinal resonance frequency smaller than the torsional resonance frequency of the tire " from the amplitude of vibration included in the acquired wheel speed data,
Calculated amplitude correction value corresponding to the difference between the amplitude of the vibration having an amplitude and the extracted suspension longitudinal direction resonance frequency of the vibration having a given reference suspension longitudinal direction resonance frequency (frequency component correction value), the same amplitude Using the correction value to correct the amplitude of vibration having the corrected torsional resonance frequency;
And the relationship between the wheel load amplitude and wheel vibration with reference torsional resonance frequency obtained when the amplitude of the vibration having a suspension longitudinal direction resonance frequency is the amplitude of the vibration having the reference suspension longitudinal direction resonant frequency, the correction The wheel load is estimated based on the amplitude of vibration having a torsional resonance frequency.

  As described above, the frequency component of the vibration having the torsional resonance frequency changes in accordance with the change of the frequency component of the vibration having the suspension longitudinal resonance frequency. The vibration frequency component having the reference torsional resonance frequency obtained when the vibration frequency component having the suspension longitudinal resonance frequency is the frequency component of the vibration having the reference suspension longitudinal resonance frequency and the wheel load of the wheel. Have a certain correlation. In consideration of these relationships, the present method corrects the frequency component of the vibration having the extracted torsional resonance frequency by the frequency component correction value, and calculates the wheel load of the wheel from the corrected frequency component of the vibration. presume. As a result, the wheel load of the wheel is estimated more accurately in consideration of the effect of the road surface unevenness on the frequency component of vibration having a torsional resonance frequency.

Hereinafter, a wheel load estimating device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 4 schematically shows the configuration of a vehicle equipped with the wheel load estimation device 10 according to this embodiment.
The vehicle has a first wheel 11 and a second wheel 12 positioned on the left and right sides of the front side of the vehicle, a third wheel 13 and a fourth wheel 14 positioned on the left and right sides of the vehicle, and the wheels. A first tire 21, a second tire 22, a third tire 23, and a fourth tire 24 are provided.

  The wheel load estimating device 10 includes a first wheel speed sensor 31, a second wheel speed sensor 32, a third wheel speed sensor 33, a fourth wheel speed sensor 34, a direct pressure type first pressure sensor 35, The second pressure sensor 36, the third pressure sensor 37, the fourth pressure sensor 38, the outside air temperature sensor 39, and a receiver that receives signals output from the pressure sensors via the receiving antennas 41a and 41b. 40, a brake fluid pressure control unit 42, a brake pedal depression force sensor 43, an initialization switch 44, and an electronic control unit 50.

  Since the first wheel speed sensor 31 to the fourth wheel speed sensor 34 have the same structure, the first wheel speed sensor 31 will be described below as an example. As shown in FIGS. 2A and 2B, the first wheel speed sensor 31 includes a sensor rotor 31a that rotates with the same rotation shaft fixed to the rotation shaft of the first wheel 11, and a pickup coil 31b. And a magnet (not shown). The sensor rotor 31a is provided with teeth on the outer periphery thereof arranged at predetermined center angles. The pickup coil 31b is disposed close to the tooth portion. The first wheel speed sensor 31 takes out a change in the magnetic field generated by the rotation of the magnet and the sensor rotor 31a as a voltage change by the pickup coil 31b, and outputs the voltage change as an AC signal. That is, the first wheel speed sensor 31 to the fourth wheel speed sensor 34 each output a signal corresponding to the rotational speed of the wheel including the tire.

  Since the first pressure sensor 35 to the fourth pressure sensor 38 have the same structure, the first pressure sensor 35 will be described below as an example. The first pressure sensor 35 is mounted integrally with the air valve of the wheel fixed to the hub of the first wheel 11 and inside the tire. The first pressure sensor 35 includes a pressure detector that detects the internal pressure P1 of the tire, a temperature detector that detects the internal temperature T1 of the tire, and a transmitter. The transmitter transmits the internal pressure P1 of the tire as a pressure signal and transmits the internal temperature T1 as a temperature signal. The first pressure sensor 35 to the fourth pressure sensor 38 correspond to tire pressure detecting means for detecting the internal pressures P1 to P4 of the first tire 21 to the fourth tire 24, respectively. This corresponds to tire temperature detecting means for detecting the internal temperatures T1 to T4.

The outside air temperature sensor 39 detects the outside air temperature and outputs a signal indicating the outside air temperature. The outside air temperature sensor 39 corresponds to outside air temperature detecting means for detecting the outside air temperature outside the vehicle.
The receiver 40 receives the pressure signal and the temperature signal transmitted from the first pressure sensor 35 and the second pressure sensor 36, respectively, via a receiving antenna 41a provided at a substantially central portion in the left-right direction in front of the vehicle. It has become. In addition, the receiver 40 receives the pressure signal and the temperature signal transmitted from the third pressure sensor 37 and the fourth pressure sensor 38, respectively, via a reception antenna 41b provided at a substantially central portion in the left-right direction behind the vehicle. It is supposed to be.

The brake hydraulic pressure control unit 42 controls each wheel by controlling the hydraulic pressure (brake hydraulic pressure) for pressing each brake pad (not shown) against each disk rotor (not shown) that rotates with each wheel. Each power is controlled.
The brake pedal depression force sensor 43 outputs a signal indicating the depression force of the brake pedal BP.

  The initialization switch 44 is disposed in the passenger compartment, and when a serviceman or a crew member of a maintenance shop replaces a tire, the initialization switch 44 is operated after correctly managing the tire air pressure. The signal which represents is output.

  The electronic control unit 50 includes a microcomputer mainly composed of a CPU 51, a ROM 52, a RAM 53, a back up RAM 54, and an interface 55 connected to each other by a bus.

  The electronic control unit 50 is connected to the first wheel speed sensor 31 to the fourth wheel speed sensor 34, the outside air temperature sensor 39, the receiver 40, and the brake pedal depression force sensor 43, and is detected from each wheel speed sensor. The AC signal, the signal detected from the outside air temperature sensor 39, the pressure signal and temperature signal received by the receiver 40, the signal output from the brake pedal depression force sensor 43, and the signal output from the initialization switch 44 are input. It is like that.

  Further, the electronic control unit 50 is connected to the brake hydraulic pressure control unit 42, and in response to an instruction from the CPU 51, a control signal for driving each electromagnetic valve and motor (not shown) is sent to the brake hydraulic pressure control unit 42. It is supposed to be sent out.

Next, an operation in which the wheel load estimation device 10 configured as described above executes a wheel load estimation process will be described.
The CPU 51 of the electronic control unit 50 estimates the wheel load indicated by the processing routine (program) for calculating the wheel speed SPD (C) indicated by the flowchart of FIG. 5 and the flowchart of FIG. 6 while the vehicle is traveling. The main processing routine (program) for executing the processing is repeatedly executed every elapse of a predetermined time.

  Note that all the processes described later are similarly executed based on the wheel speed data obtained based on the signals detected from the respective wheel speed sensors and the signals detected from the respective pressure sensors. Based on the wheel speed data obtained based on the signal detected from the first wheel speed sensor 31 and the signal detected from the first pressure sensor 35, the first wheel 11 and the first tire 21 are targeted. Only the processing will be described.

Wheel speed SPD (C) calculation processing.
When the predetermined timing is reached, the CPU 51 starts processing from step 500 in FIG. 5 and proceeds to step 505, adds “1” to the counter C, and proceeds to step 510. The counter C indicates the number of wheel speeds SPD (C) calculated in step 515 described later. The counter C is set to “0” in advance in an initial routine that is executed when the ignition key is changed from “OFF” to “ON”. Therefore, the value of the counter C is “1” at the present time.

  Next, in step 510, the CPU 51 reads the wheel speed data t. The electronic control unit 50 incorporates a waveform shaping circuit (not shown). The waveform shaping circuit compares the AC signal output from the first wheel speed sensor 31 with a predetermined threshold, and when the AC signal is greater than the threshold, the high level, and when the AC signal is less than the threshold. A pulse signal having a low level is formed. Then, the CPU 51 calculates a time between successive rising edges (or between falling edges) of the pulse signal by a wheel speed data calculation routine (not shown) that is interrupted and activated at the rising edge (or falling edge) of the pulse signal. The obtained time is stored in a storage area such as the RAM 53 as the wheel speed data t described above. Therefore, in step 510, the CPU 51 reads the wheel speed data t calculated by the wheel speed data calculation routine.

  Next, the CPU 51 proceeds to step 515 to calculate the wheel speed SPD (C) (= SPD (1)) based on the wheel speed data t. That is, the CPU 51 calculates the wheel speed SPD (C) by dividing the constant K by the wheel speed data t. Next, the CPU 51 proceeds to step 520 to perform a band pass filter (digital filter) process on the wheel speed SPD (C). Specifically, the CPU 51 performs filtering with a bandwidth of 10 to 20 Hz, and stores the wheel speed SPD (C) filtered with the same bandwidth in the RAM 53 shown in FIG. Further, the CPU 51 performs a filter process with a bandwidth of 30 to 50 Hz, and converts a wheel speed SPD (C) filtered with the same bandwidth to a wheel speed SPD (C) filtered with the bandwidth of 10 to 20 Hz. ) So that it can be identified. Next, the CPU 51 proceeds to step 525, where the outside air temperature Tout (C) (= Tout (1)) detected from the outside air temperature sensor 39 in association with the wheel speed SPD (C), from the first pressure sensor. The detected tire internal pressure P (C) (= P1 (1)) and tire internal temperature T (C) (= T1 (1)) are read, and together with the wheel speed SPD (C), the RAM 53 shown in FIG. To store.

Next, the CPU 51 proceeds to step 595 to end the processing of this routine once. Thus, the wheel speed SPD (C), the outside air temperature Tout (C), the tire internal pressure P (C), and the tire internal temperature T (C) are stored in the RAM 53 by the number indicated by the counter C. Is done.

  The wheel speed data calculation routine and step 510 described above are based on the wheel speed data t corresponding to the rotational speed of each wheel based on the signals output from the first wheel speed sensor 31 to the fourth wheel speed sensor 34. This corresponds to wheel speed data acquisition means for acquiring

Wheel load estimation processing.
When the predetermined timing is reached, the CPU 51 starts processing from step 600 in FIG. 6 and proceeds to step 605 to determine whether or not the counter C is equal to the analysis number Cmax. In the analysis number Cmax, the number (Cmax> 1) of wheel speeds SPD (C) necessary for performing frequency analysis (for example, FFT calculation) is set in advance.

  At this time, since the value of the counter C is “1”, it is not equal to the analysis number Cmax. Therefore, the CPU 51 makes a “No” determination at step 605 to proceed to step 610, sets the value of the determination flag H to “0”, proceeds to step 695, and temporarily ends the processing of this routine.

  The determination flag H is a flag for determining whether or not frequency analysis has been executed for the wheel speed SPD (C). When the value is “0”, it indicates that frequency analysis has not been executed. A value of “1” indicates that frequency analysis is being performed. The determination flag H is set to a value of “0” in step 610 and is set to a value of “1” in step 850 described later after performing a frequency analysis of the wheel speed SPD (C). .

  After that, when the value of the counter C is increased by the processing of step 505 of FIG. 5 described above and becomes equal to the analysis number Cmax, the CPU 51 proceeds to step 605 following step 600, and at step 605, “ The process proceeds to step 615, and a subroutine for suspension longitudinal resonance frequency component calculation processing shown in the flowchart of FIG. 7 is called.

The CPU 51 starts processing from step 700 of the called subroutine, proceeds to step 705, and sets the value of the counter C to “0”.
Next, the CPU 51 proceeds to step 710 and selects data to be subjected to frequency analysis based on the wheel speed SPD (1) to the wheel speed SPD (Cmax) filtered with a bandwidth of 10 to 20 Hz. Specifically, the CPU 51 changes the wheel speed SPD (i) from the previously calculated wheel speed SPD (i-1) among the wheel speeds SPD (1) to SPD (Cmax). If it is determined that the absolute value of the minute (| SPD (i) −SPD (i−1) |, i is a natural number) is equal to or greater than a predetermined value, the corresponding wheel speed SPD (1) to wheel speed SPD (Cmax) All are excluded from the data subject to frequency analysis as a set. Further, the CPU 51 out of the outside air temperature Tout (1) to the outside air temperature Tout (Cmax) stored in the RAM 53 in association with each of the wheel speed SPD (1) to the wheel speed SPD (Cmax), the outside air temperature Tout (i). ) Is outside the predetermined range, all the corresponding wheel speed SPD (1) to wheel speed SPD (Cmax) are excluded from the data subject to frequency analysis as one set. As a result, data containing a large amount of noise components (for example, other frequency components generated from an external force other than road surface unevenness) is eliminated.

  Next, the CPU 51 proceeds to step 715 to perform frequency analysis on the selected wheel speed SPD (1) to wheel speed SPD (Cmax). As a result, the vibration gain G (f) of each frequency f (for example, 0.1 Hz interval) shown in FIG. 1 is extracted.

  Next, the CPU 51 proceeds to step 720 and adds the vibration gain G (f) of each frequency f of 10 to 20 Hz to the integrated gain GS (f) of each frequency f. The integrated gain GS (f) is used to integrate the vibration gain G (f), and is set to “0” in advance in the initial routine.

  Next, the CPU 51 proceeds to step 725 to add “1” to the vibration gain addition count S. The vibration gain addition count S indicates the number of times the vibration gain G (f) is added to the integrated gain GS (f), and is set to a value of “0” in advance in the initial routine. Accordingly, at the present time, the value of the vibration gain addition count S is “1”.

  Next, the CPU 51 proceeds to step 730 and determines whether or not the vibration gain addition number S is equal to the maximum addition number Smax. The maximum number of additions Smax indicates the number of times (Smax> 1) at which the vibration gain G (f) should be added to the integrated gain GS (f). At this time, the value of the vibration gain addition number S is not equal to the maximum addition number Smax. Therefore, the CPU 51 makes a “No” determination at step 730 and immediately proceeds to step 795 to end the processing of this subroutine once until it is called from the main routine next time.

Next, the CPU 51 proceeds to step 620 of the main routine as the return destination, and calls the torsional resonance frequency component calculation processing subroutine shown by the flowchart in FIG.
The CPU 51 starts processing from the called step 800 and proceeds to step 805, where the frequency analysis is performed based on the wheel speed SPD (1) to the wheel speed SPD (Cmax) filtered with a bandwidth of 30 to 50 Hz. Select the data to be. Specifically, as executed in step 710 described above, the CPU 51 calculates the absolute value of the change in the wheel speed SPD (k) from the wheel speed SPD (k−1) calculated immediately before ( | SPD (k) −SPD (k−1) |, where k is a natural number), when it is determined that the absolute value is greater than or equal to a predetermined value, the corresponding wheel speed SPD (1) to wheel speed SPD (Cmax ) Are removed from the frequency analysis target data as a set. Further, the CPU 51 associates each of the wheel speed SPD (1) to the wheel speed SPD (Cmax) with the tire internal pressures P (1) to P (Cmax) and the tire internal temperature T (1) stored in the RAM 53. ) To T (Cmax), when it is determined that the internal pressure P (k) or the internal temperature T (k) is outside the predetermined range, all the corresponding wheel speeds SPD (1) to SPD (Cmax) Are excluded from the data subject to frequency analysis as a set.

  Next, the CPU 51 proceeds to step 810 to execute frequency analysis on the selected wheel speed SPD (1) to wheel speed SPD (Cmax). As a result, the vibration gain G (f) of each frequency f (for example, 0.1 Hz interval) shown in FIG. 1 is extracted.

  Next, the CPU 51 proceeds to step 815 to add the vibration gain G (f) of each frequency f of 30 to 50 Hz to the integrated gain GN (f) of each frequency f. The integrated gain GN (f) is used to integrate the vibration gain G (f), and is set to “0” in advance in the initial routine.

  Next, the CPU 51 proceeds to step 820 to determine whether or not the vibration gain addition number S is equal to the maximum addition number Smax (Smax> 1). At this time, the value of the vibration gain addition count S is “1”, which is not equal to the maximum addition count Smax. Therefore, the CPU 51 makes a “No” determination at step 820 to immediately proceed to step 895 to end the processing of this subroutine once until it is called from the main routine next time.

  Next, the CPU 51 proceeds to step 625 of the main routine as the return destination, and determines whether or not the value of the determination flag H is “1”. At this time, the value of the determination flag H has not been changed after being set to “0” in Step 610. Therefore, the CPU 51 makes a “No” determination at step 625 to immediately proceed to step 695 to end the processing of this routine once.

  Thereafter, the CPU 51 repeats the processing of steps 705 to 730, and when the vibration gain addition number S becomes equal to the maximum addition number Smax in step 730, the CPU 51 determines “Yes” in the step 730. Proceeding to step 735, the integrated gain GS (f) of each frequency f is divided by the maximum number of additions Smax to obtain an average value Gsa (f) of the vibration gain G (f) of each frequency f.

  Next, the CPU 51 proceeds to step 740, and determines the maximum value of the average value Gsa (f) of the vibration gain of each frequency f within the range of 10 to 20 Hz thus obtained as the vibration gain Gsa (hereinafter referred to as the suspension longitudinal resonance frequency). , Also referred to as vibration gain Gsa). Next, the CPU 51 proceeds to step 745, sets the value of the integrated gain GS (f) of each frequency f to “0”, proceeds to step 795, and ends the processing of this subroutine once until it is called from the main routine next. To do.

  Similar to the processing in steps 705 to 730, the CPU 51 repeats the processing in steps 805 to 820. When the vibration gain addition number S becomes equal to the maximum addition number Smax in step 820, the CPU 51 In step 825, the integrated gain GN (f) of each frequency f is divided by the maximum number of additions Smax, and the average value Gne () of the vibration gain G (f) of each frequency f is determined. f) is obtained. Next, the CPU 51 proceeds to step 830, where the maximum value of the average value Gne (f) of the vibration gain of each frequency f within the range of 30 to 50 Hz obtained in this way is set as the vibration gain Gne (hereinafter referred to as the vibration gain Gne). It is also called vibration gain Gne).

  Next, the CPU 51 proceeds to step 835, sets “0” as the value of the vibration gain addition count S, proceeds to step 840, and sets “0” as the value of the integrated gain GN (f) of each frequency f. Thereafter, the process proceeds to step 845, where the value of the determination flag H is set to “1”, the process proceeds to step 895, and the process of this subroutine is temporarily ended until the next call from the main routine.

  As described above, as shown in FIG. 1, the vibration gain Gsa with respect to the suspension longitudinal resonance frequency appearing in the region around 10-20 Hz based on the wheel speed SPD (C) and the twist appearing in the region around 30-50 Hz. A vibration gain Gne with respect to the resonance frequency is extracted.

Steps 710 to 740 extract the vibration frequency component (vibration gain Gsa) having the suspension longitudinal resonance frequency from the vibration frequency component (vibration gain G (f)) included in the wheel speed data t. It corresponds to a resonance frequency component extraction means.
Steps 805 to 830 extract a torsional resonance frequency component for extracting a vibration frequency component (vibration gain Gne) having a torsional resonance frequency from the vibration frequency component (vibration gain G (f)) included in the wheel speed data t. Corresponds to means.

  At this point, when the CPU 51 returns to step 625 of the main processing routine shown in FIG. 6, the value of the determination flag H is set to “1”. Therefore, the CPU 51 makes a “Yes” determination at step 625 to proceed to step 630, and calls the suspension longitudinal resonance gain correction processing subroutine shown in the flowchart of FIG.

  The CPU 51 starts processing from the called step 900 and proceeds to step 905, reads the outside air temperature Tout, and proceeds to step 910. Here, the electronic control device 50 takes in the outside air temperature detected by the outside air temperature sensor 39 at regular time intervals, calculates an average value of a plurality of outside air temperatures taken within a predetermined time as the outside air temperature Tout, and the like. Is stored in the storage area. That is, the outside air temperature Tout is an average outside air temperature during a period in which the wheel speed SPD (C) for obtaining the vibration gain Gsa and the vibration gain Gne is taken.

  The vibration gain Gsa having the suspension longitudinal resonance frequency changes as the outside air temperature Tout changes. Further, the absolute value of the vibration gain Gsa with respect to the outside air temperature Tout varies depending on the wheel load value. Accordingly, any one of the plurality of linear functions shown in FIG. 10A shows the proportional relationship between the vibration gain Gsa and the outside air temperature Tout corresponding to the wheel load actually applied to the wheel. It becomes the function shown.

  However, at present, actual wheel loads are not required. Therefore, the CPU 51 obtains a correction amount HTout (that is, an outside air temperature correction value) corresponding to a difference between a given reference outside air temperature Toutst (for example, 40 ° C.) and the read outside air temperature Tout, and the suspension obtained this time. The vibration gain Gsa having the longitudinal resonance frequency is corrected.

  That is, the CPU 51 substitutes the outside air temperature Tout into the function g in Step 910, thereby correcting the amount of correction HTout corresponding to the difference between a given reference outside air temperature Toutst (for example, 40 ° C.) and the read outside air temperature Tout. The process proceeds to step 915, and the correction amount HTout is added to the vibration gain Gsa having the suspension longitudinal resonance frequency to obtain the vibration vibration Gsah having the corrected suspension longitudinal resonance frequency. As a result, the vibration gain Gsah having the corrected suspension longitudinal resonance frequency has the reference suspension longitudinal resonance frequency obtained when the outside temperature Tout is the reference outside temperature Toutst regardless of the outside temperature Tout. Approaching Gsast.

  Next, in step 920, the CPU 51 corrects the vibration gain Gsast having the given reference suspension longitudinal resonance frequency by substituting the vibration gain Gsah having the corrected suspension longitudinal resonance frequency into the function h. The correction amount HGsa (frequency component correction value) corresponding to the difference from the vibration gain Gsah is calculated, and the process proceeds to step 995 to end the process of this subroutine once until it is called from the main routine. The correction amount HGsa is used to correct the vibration gain Gne having the torsional resonance frequency of the tire in step 1305 described later.

  The vibration gain Gne having the torsional resonance frequency changes with changes in road surface unevenness. The change in the road surface unevenness appears as a change in the vibration gain Gsa having the suspension longitudinal resonance frequency included in the wheel speed data t. Therefore, as shown in FIG. 10B, it can be considered that the vibration gain Gne having the torsional resonance frequency changes as the vibration gain Gsa having the suspension longitudinal resonance frequency changes.

  More specifically, the vibration gain Gsa having the suspension longitudinal resonance frequency and the vibration gain Gne having the torsional resonance frequency are in a proportional relationship. This proportional relationship is represented by a linear function in which the intercept value is specified by the wheel load value. In other words, no matter what the wheel load is, if the vibration gain Gsah having the suspension longitudinal resonance frequency changes by a predetermined amount, the vibration gain Gne having the torsional resonance frequency always changes by a predetermined amount. The function h shown in step 920 is obtained based on this relationship.

  Therefore, the vibration gain having the torsional resonance frequency obtained by adding the correction amount HGsa calculated in step 920 to the vibration gain Gne having the torsional resonance frequency is independent of the road surface unevenness state and the outside air temperature Tout. A vibration gain Gnesst having a reference torsional resonance frequency obtained when the outside air temperature Tout is the reference outside air temperature Toutst and the vibration gain Gsa having the suspension longitudinal resonance frequency is the vibration gain Gsast having the reference suspension longitudinal resonance frequency. Get closer to.

  Steps 910 and 915 calculate an outside air temperature correction value (correction amount HTout) corresponding to a difference between a given reference outside air temperature Toutst and the detected outside air temperature Tout, and are extracted using the correction value. This corresponds to suspension longitudinal resonance frequency component correction means for correcting the vibration frequency component (vibration gain Gsa) having the suspension longitudinal resonance frequency.

Next, when the CPU 51 returns to step 635 of the main processing routine shown in FIG. 6, the CPU 51 calls a torsional resonance gain correction processing subroutine shown by the flowchart in FIG.
The CPU 51 starts processing from the called step 1100 and proceeds to step 1105 to read the tire internal pressure P (= P1) and the tire temperature T (= T1) detected by the first pressure sensor 35. Proceed to step 1110. In step 1110, the CPU 51 substitutes the tire internal pressure P into the function l to obtain a difference between the reference internal pressure Pst (for example, 200 kpa) of the given tire and the read tire internal pressure P. The corresponding correction amount Hp (tire pressure correction value) is calculated, and the process proceeds to step 1115. The correction amount Hp is used to correct the vibration gain Gne having the torsional resonance frequency of the tire in step 1305 described later.

  As shown in FIG. 12 (a), the vibration gain Gne having a torsional resonance frequency also changes as the tire internal pressure P changes. A plurality of linear functions shown in FIG. 12 (a) indicate a proportional relationship between the internal pressure P of the tire and the vibration gain Gne having a torsional resonance frequency, and are determined on any straight line depending on the wheel load value. It is. In consideration of this relationship, the CPU 51 calculates a correction amount Hp (tire pressure correction value) corresponding to the difference between the reference internal pressure Pst of the given tire and the internal pressure P of the tire. As a result, the vibration gain having the torsional resonance frequency obtained by adding this correction amount Hp to the vibration gain Gne having the torsional resonance frequency is equal to the reference internal pressure Pst regardless of the tire internal pressure P. It approaches the vibration gain Gnepst having the reference torsional resonance frequency obtained when.

  Next, the CPU 51 proceeds to step 1115, and substitutes the tire internal temperature T into the function m, so that the reference internal temperature Tst (for example, 50 ° C.) of the given tire and the read internal temperature of the tire are obtained. A correction amount Ht (that is, a tire temperature correction value) corresponding to the difference from T is calculated, the process proceeds to step 1195, and the process of this subroutine is temporarily ended until called from the main routine next.

  As shown in FIG. 12 (b), the vibration gain Gne having the torsional resonance frequency also changes as the tire internal temperature T changes. A plurality of linear functions shown in FIG. 12 (b) indicate a proportional relationship between the tire internal temperature T and the vibration gain Gne having the torsional resonance frequency, and are determined in any straight line depending on the wheel load value. It is. In consideration of this relationship, the CPU 51 calculates a correction amount Ht (tire temperature correction value) corresponding to the difference between the reference internal temperature Tst of the given tire and the internal temperature T of the tire. As a result, the vibration gain having the torsional resonance frequency obtained by adding the correction amount Ht to the vibration gain Gne having the torsional resonance frequency is equal to the reference internal temperature Tst regardless of the tire internal temperature T. It approaches the vibration gain Gnetst having the reference torsional resonance frequency obtained when.

Next, the CPU 51 returns to step 640 of the main processing routine shown in FIG. 6 and calls the wheel load calculation processing subroutine shown by the flowchart in FIG.
The CPU 51 starts processing from the called step 1300 and proceeds to step 1305 to add the correction amount HGsa (frequency correction value), the correction amount Hp (tire pressure correction value), and the correction amount Ht to the vibration gain Gne having the torsional resonance frequency. By adding (tire temperature correction value), the vibration gain Gneh having the corrected torsional resonance frequency is obtained.

  Accordingly, the vibration gain Gneh having the corrected torsional resonance frequency is such that the tire internal pressure P is the reference internal pressure Pst, the tire internal temperature T is the reference internal temperature Tst, and the outside air temperature Tout is the reference outside air temperature Toutst. And a vibration gain having a reference torsional resonance frequency obtained when the vibration gain Gsa having the suspension longitudinal resonance frequency is the vibration gain Gsast having the reference suspension longitudinal resonance frequency.

  Next, the CPU 51 proceeds to step 1310 to estimate the wheel load WF by substituting the vibration gain Gneh having the corrected torsional resonance frequency into the function n. The correlation between the vibration gain having the reference torsional resonance frequency shown in step 1310 and the wheel load WF is stored in advance in a storage area such as the RAM 53. The stored correlation is that the tire internal pressure P is the reference internal pressure Pst, the tire internal temperature T is the reference internal temperature Tst, the outside air temperature Tout is the reference outside air temperature Toutst, and the suspension longitudinal direction “Relationship between vibration gain having torsional resonance frequency and wheel load” obtained when vibration gain Gsa having resonance frequency is vibration gain Gsast having a resonance frequency in the longitudinal direction of the reference suspension. Yes.

  Next, the CPU 51 proceeds to step 1315 and determines whether or not the process proceeds to the same step for the first time after the initialization switch 44 is changed to the “ON” state. If it is immediately after a serviceman or crew member of a factory or the like has replaced a tire and the initialization switch 44 is operated, the CPU 51 determines “Yes” in step 1315 and proceeds to step 1320. The wheel load WF estimated in step 1310 is set to the wheel load reference value WFstd, the process proceeds to step 1395, and the process of this subroutine is temporarily ended until called from the main routine next time.

On the other hand, when the predetermined time elapses after the initialization switch 44 is operated and the CPU 51 proceeds to step 1315, the process proceeds to the first step after the initialization switch 44 is changed to the “ON” state. If not, the CPU 51 makes a “No” determination at step 1315 to proceed to step 1325, and divides the wheel load WF estimated this time by the wheel load reference value WFstd at step 1310 to thereby calculate the wheel load ratio RWF. The process proceeds to step 1395, and the process of this subroutine is temporarily ended until it is called from the main routine next time.
Next, the CPU 51 returns to step 695 of the main processing routine shown in FIG. 6, and once ends the processing of this routine.

  In step 1310, the vibration frequency component (vibration gain Gneh) having the corrected torsional resonance frequency, the vibration frequency component having the reference torsional resonance frequency stored in the storage area (RAM 53), and the wheel load are calculated. This corresponds to wheel load estimating means for estimating the wheel load WF of the wheel based on the relationship.

  When various parameters such as the internal pressure P of the tire are in a constant reference state, the relationship between the vibration gain having the torsional resonance frequency and the wheel load WF of the wheel can be uniquely determined. In order to make use of this relationship, the present apparatus corrects the extracted (obtained) vibration gain Gne having the torsional resonance frequency based on correction values of various parameters, and when the various parameters are in a constant reference state. The vibration gain (frequency component) Gneh having the torsional resonance frequency that will be obtained in the above is obtained. Then, the wheel load WF of the wheel is estimated from the corrected frequency component Gneh of the same vibration and the unique relationship described above. As a result, the influence of various parameters such as the tire internal pressure on the vibration gain Gne having the torsional resonance frequency is eliminated, so that the wheel load of the wheel can be estimated more accurately.

  In the above embodiment, the CPU 51 corrects the vibration gain Gne having the torsional resonance frequency by using all the parameters of the tire internal pressure P, the vibration gain Gsa having the suspension longitudinal resonance frequency, and the tire internal temperature T. However, among these parameters, at least one of the tire internal pressure P, the vibration gain Gsa having the longitudinal resonance frequency of the suspension, and the tire internal temperature T (any two or more combinations may be used). Thus, the vibration gain Gne having the torsional resonance frequency may be corrected, and the wheel load of the wheel may be estimated from the corrected frequency component Gneh of the same vibration. As a result, the influence of at least one of the parameters used for the correction on the vibration gain Gne having the torsional resonance frequency is eliminated, so that the wheel load of the wheel can be estimated more accurately.

  For example, when correcting the vibration gain Gne using the tire internal pressure P as the only parameter, the CPU 51 corrects the vibration gain Gne by adding the tire pressure correction value Hp to the vibration gain Gne having the torsional resonance frequency in step 1305. A vibration gain Gneh having a torsional resonance frequency can be obtained. In this case, step 1305 corresponds to torsional resonance frequency component correction means for correcting the vibration gain Gne having the torsional resonance frequency using the tire pressure correction value Hp.

  Further, for example, when correcting the vibration gain Gne using the tire internal temperature T as the only parameter, the CPU 51 adds the tire temperature correction value Ht to the vibration gain Gne having a torsional resonance frequency in Step 1305. The vibration gain Gneh having the corrected torsional resonance frequency can be obtained. In this case, step 1305 corresponds to torsional resonance frequency component correction means for correcting the vibration gain Gne having the torsional resonance frequency using the tire temperature correction value Ht.

  For example, when correcting the vibration gain Gne having the torsional resonance frequency using the vibration gain Gsa having the suspension longitudinal resonance frequency as the only parameter, the CPU 51 sets the frequency component correction value HGsa to the vibration gain Gne in step 1305. By adding, the vibration gain Gneh having the corrected torsional resonance frequency can be obtained. In this case, step 1305 corresponds to torsional resonance frequency component correction means for correcting the vibration gain Gne having the torsional resonance frequency using the frequency component correction value HGsa.

  In the same embodiment, the vibration gain Gsa having the suspension longitudinal resonance frequency is corrected using the correction amount HTout obtained based on the outside air temperature Tout in steps 905 to 915 in FIG. However, the above-described step of correcting the vibration gain Gsa having the suspension longitudinal resonance frequency according to the outside air temperature Tout is not executed, and the process immediately proceeds from step 900 to step 920. Based on this, the vibration gain Gne having the torsional resonance frequency may be corrected.

  The wheel load ratio RWF estimated in this way is, for example, determined so that the ratio of the rear wheel braking force to the front wheel braking force is reduced according to the degree of slip of the rear wheel with respect to the front wheel during vehicle braking. It is used for EBD control (Electronic Break Force Distribution) for controlling power. Specifically, the CPU 51 calculates a front / rear wheel load ratio, which is a wheel load ratio between the front wheels and the rear wheels, based on the wheel load ratio RWF of each wheel, and calculates a braking force distribution ratio based on the front / rear wheel load ratio. Ask. The brake hydraulic pressure control unit 42 controls the brake hydraulic pressure applied to each wheel cylinder of each rear wheel according to the degree of slip of the rear wheel based on the braking force distribution ratio, thereby applying to each rear wheel. Control each braking force. Further, the brake fluid pressure increasing speed and decreasing speed in the anti-skid control device may be changed by the wheel load ratio RWF. Furthermore, in the said embodiment, although wheel load ratio RWF is calculated | required, you may comprise so that wheel load itself may be calculated | required.

It is the figure which showed the vibration gain contained in wheel speed data. FIG. 2 (a) is a diagram schematically showing the state of the tires and wheels constituting the spring-mass system when the wheel load is large, and FIG. 2 (b) is the tire when the wheel load is small. It is a figure showing typically the state of a wheel or a wheel. FIG. 3A is a diagram showing a change in vibration gain accompanying a change in wheel load, FIG. 3B is a diagram showing a change in vibration gain accompanying a change in road surface input, and FIG. FIG. 3 is a diagram showing a change in vibration gain accompanying a change in the internal pressure of the tire, and FIG. 3D is a diagram showing a change in vibration gain accompanying a change in the internal temperature of the tire. It is a schematic block diagram of a wheel load estimation device. It is the flowchart which showed the program performed in order to calculate wheel speed SPD (C). It is the flowchart which showed the program performed in order to estimate a wheel load. It is the flowchart which showed the program performed in order to calculate a suspension longitudinal direction resonance frequency. It is the flowchart which showed the program performed in order to calculate a torsional resonance frequency. It is the flowchart which showed the program performed in order to correct | amend the vibration gain which has a suspension longitudinal direction resonance frequency. FIG. 10A is a diagram showing the relationship between the outside air temperature and the vibration gain having the suspension longitudinal resonance frequency. FIG. 10B is a diagram showing the relationship between the vibration gain having the corrected longitudinal resonance frequency of the suspension and the vibration gain having the torsional resonance frequency. It is the flowchart which showed the program performed in order to correct | amend the vibration gain which has a torsional resonance frequency. FIG. 12A is a diagram showing the relationship between the internal pressure of the tire and the vibration gain having the torsional resonance frequency. FIG. 12B is a diagram showing the relationship between the internal temperature of the tire and the vibration gain having the torsional resonance frequency. It is the flowchart which showed the program performed in order to calculate a wheel load.

DESCRIPTION OF SYMBOLS 10 ... Wheel load estimation apparatus, 11 ... 1st wheel, 12 ... 2nd wheel, 13 ... 3rd wheel, 14 ... 4th wheel, 21 ... 1st tire, 22 ... 2nd tire, 23 3rd tire, 24 ... 4th tire, 31 ... 1st wheel speed sensor, 32 ... 2nd wheel speed sensor, 33 ... 3rd wheel speed sensor, 34 ... 4th wheel speed sensor, 35 ... 1st pressure sensor, 36 ... 2nd pressure sensor, 37 ... 3rd pressure sensor, 38 ... 4th pressure sensor, 39 ... Outside temperature sensor, 40 ... Receiver, 41a, 41b ... Reception antenna, 42 ... brake fluid pressure control unit, 43 ... brake pedal depression force sensor, 44 ... initialization switch, 50 ... electronic control unit.

Claims (8)

A wheel speed sensor that outputs a signal corresponding to the rotational speed of the wheel including the tire;
Wheel speed data acquisition means for acquiring wheel speed data corresponding to the rotational speed of the wheel based on the signal output from the wheel speed sensor;
A torsional resonance amplitude extracting means for extracting the vibration amplitude having the torsional resonance frequency of the tire from the vibration amplitude contained in the acquired wheel speed data;
Tire pressure detecting means for detecting the internal pressure of the tire;
Calculating a tire pressure correction value corresponding to a difference between a reference internal pressure of a given tire and the detected internal pressure of the tire, and using the tire pressure correction value, the vibration having the extracted torsional resonance frequency is calculated. and the torsional resonance amplitude correction means for correcting the amplitude,
Storage means for storing the relationship between the amplitude of vibration having a reference torsional resonance frequency obtained when the internal pressure of the tire is the reference internal pressure and the wheel load of the wheel;
Wheel load estimating means for estimating the wheel load based on the amplitude of vibration having the corrected torsional resonance frequency and the relationship stored in the storage means;
A wheel load estimation device comprising: The wheel load estimation device according to claim 1, further comprising:
Suspension longitudinal resonance amplitude extraction means for extracting the vibration amplitude having a suspension longitudinal resonance frequency smaller than the torsional resonance frequency of the tire from the vibration amplitude included in the acquired wheel speed data;
The torsional resonance amplitude correcting means is
An amplitude correction value corresponding to a difference between an amplitude of vibration having a given reference suspension longitudinal resonance frequency and an amplitude of vibration having the extracted suspension longitudinal resonance frequency is calculated, and the amplitude correction value is used to calculate the amplitude correction value. Further correcting the amplitude of the vibration having the corrected torsional resonance frequency;
Relationship stored in the storage means is a relational obtained when the amplitude of the vibration having a suspension longitudinal direction resonance frequency is the amplitude of the vibration having the reference suspension longitudinal direction resonant frequency,
The wheel load estimating means includes
A wheel load estimation device that estimates the wheel load based on the amplitude of vibration having a torsional resonance frequency further corrected using the amplitude correction value and the relationship stored in the storage means. The wheel load estimation device according to claim 1 or 2, further comprising:
Tire temperature detecting means for detecting the internal temperature of the tire,
The torsional resonance amplitude correcting means is
Calculating a tire temperature correction value corresponding to a difference between a reference internal temperature of a given tire and the detected internal temperature of the tire, and using the tire temperature correction value, the vibration having the corrected torsional resonance frequency is calculated. Further correct the amplitude ,
The relationship stored in the storage means is a relationship obtained when the internal temperature of the tire is the reference internal temperature,
The wheel load estimating means includes
A wheel load estimation device that estimates the wheel load based on an amplitude of vibration having a torsional resonance frequency further corrected using the tire temperature correction value and the relationship stored in the storage means. A wheel speed sensor that outputs a signal corresponding to the rotational speed of the wheel including the tire;
Wheel speed data acquisition means for acquiring wheel speed data corresponding to the rotational speed of the wheel based on the signal output from the wheel speed sensor;
A torsional resonance amplitude extracting means for extracting the vibration amplitude having the torsional resonance frequency of the tire from the vibration amplitude contained in the acquired wheel speed data;
Suspension longitudinal resonance amplitude extraction means for extracting the vibration amplitude having a suspension longitudinal resonance frequency smaller than the torsional resonance frequency of the tire from the amplitude of vibration included in the acquired wheel speed data;
An amplitude correction value corresponding to a difference between an amplitude of vibration having a given reference suspension longitudinal resonance frequency and an amplitude of vibration having the extracted suspension longitudinal resonance frequency is calculated, and the amplitude correction value is used to calculate the amplitude correction value. Torsional resonance amplitude correcting means for correcting the amplitude of vibration having the extracted torsional resonance frequency;
Storing the amplitude of the vibration having a suspension longitudinal direction resonant frequency stores the relationship between the amplitude and the wheel wheel load of the vibration with reference torsional resonance frequency obtained when the amplitude of the oscillation having the reference suspension longitudinal direction resonant frequency Means,
Wheel load estimating means for estimating the wheel load based on the amplitude of vibration having the corrected torsional resonance frequency and the relationship stored in the storage means;
A wheel load estimation device comprising: The wheel load estimation device according to claim 4, further comprising:
Outside temperature detecting means for detecting outside temperature;
An outside air temperature correction value corresponding to a difference between a given reference outside air temperature and the detected outside air temperature is calculated, and the amplitude of vibration having the extracted longitudinal resonance frequency of the suspension is extracted using the outside air temperature correction value. A suspension longitudinal resonance amplitude correction means for correcting,
The torsional resonance amplitude correcting means is
Using the amplitude of the vibration with the outside air temperature correction value suspension longitudinal direction resonant frequency corrected using as the amplitude of the oscillation having the extracted suspension longitudinal direction resonant frequency used when calculating the amplitude correction value ,
The relationship stored in the storage means is
The amplitude of the vibration having a suspension longitudinal direction resonant frequency, wheel load estimator is a relation obtained when the amplitude of the oscillation having the reference suspension longitudinal direction resonant frequency when the outside air temperature is the reference outside air temperature. The wheel load estimation device according to claim 4 or 5, further comprising:
Tire temperature detecting means for detecting the internal temperature of the tire,
The torsional resonance amplitude correcting means is
Calculating a tire temperature correction value corresponding to a difference between a reference internal temperature of a given tire and the detected internal temperature of the tire, and using the tire temperature correction value, the vibration having the corrected torsional resonance frequency is calculated. Further correct the amplitude ,
The relationship stored in the storage means is a relationship obtained when the internal temperature of the tire is the reference internal temperature,
The wheel load estimating means includes
A wheel load estimation device that estimates the wheel load based on an amplitude of vibration having a torsional resonance frequency further corrected using the tire temperature correction value and the relationship stored in the storage means. Wheel speed data corresponding to the rotation speed of the wheel is acquired based on a signal corresponding to the rotation speed of the wheel including the tire output from the wheel speed sensor,
Extracting the vibration amplitude having the torsional resonance frequency of the tire from the vibration amplitude contained in the acquired wheel speed data,
Obtaining the internal pressure of the tire output from the pressure sensor;
Calculating a tire pressure correction value corresponding to a difference between a reference internal pressure of a given tire and the acquired internal pressure of the tire, and using the tire pressure correction value, the vibration having the extracted torsional resonance frequency is calculated. Correct the amplitude ,
The basis of the relationship between the wheel load amplitude and wheel vibration with reference torsional resonance frequency obtained when the internal pressure of the tire is the reference internal pressure, the amplitude of the vibration having said corrected torsional resonance frequency, the A wheel load estimation method for estimating the wheel load. Wheel speed data corresponding to the rotation speed of the wheel is acquired based on a signal corresponding to the rotation speed of the wheel including the tire output from the wheel speed sensor,
Extracting the vibration amplitude having the torsional resonance frequency of the tire from the vibration amplitude contained in the acquired wheel speed data,
From the amplitude of vibration included in the acquired wheel speed data, extract the amplitude of vibration having a suspension longitudinal resonance frequency smaller than the torsional resonance frequency of the tire ,
An amplitude correction value corresponding to a difference between an amplitude of vibration having a given reference suspension longitudinal resonance frequency and an amplitude of vibration having the extracted suspension longitudinal resonance frequency is calculated, and the amplitude correction value is used to calculate the amplitude correction value. Correct the amplitude of the vibration with the extracted torsional resonance frequency;
And the relationship between the wheel load amplitude and wheel vibration with reference torsional resonance frequency obtained when the amplitude of the vibration having a suspension longitudinal direction resonance frequency is the amplitude of the vibration having the reference suspension longitudinal direction resonant frequency, the correction A wheel load estimation method for estimating the wheel load based on the amplitude of vibration having a torsional resonance frequency.

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