JP2024098541A - Vehicle zero moment point calculation device - Google Patents

Abstract

[Problem] To calculate the position of the zero moment point of the vehicle by reducing the influence of vibrations of frequencies higher than the roll resonance frequency and pitch resonance frequency of the vehicle, which are absorbed by the suspension. [Solution] An acceleration sensor 12 detects the acceleration of the center of gravity C of the vehicle in the vehicle longitudinal direction (X-axis direction), vehicle width direction (Y-axis direction), and height direction (Z-axis direction). An angular velocity sensor 14 detects the angular velocity of the center of gravity C about the X-, Y-, and Z-axes. A low-pass filter 16 reduces signal components of frequencies higher than the larger of the roll resonance frequency and pitch resonance frequency of the vehicle in the detection signals of the acceleration sensor 12 and the angular velocity sensor 14. A calculation unit 20 calculates the position of the zero moment point ZMP of the vehicle based on the detection signals of the acceleration sensor 12 and the angular velocity sensor 14 after the application of the low-pass filter 14, and the detection signal of the angular velocity sensor 14 after the application of the low-pass filter 14 and differentiation. [Selected Figure] Figure 1

Description

This specification discloses an improvement to a vehicle zero moment point calculation device.

Patent Document 1 discloses a vehicle suspension system that includes a suspension with a variable damping coefficient provided between the vehicle body and each wheel, a bandpass filter to which the sprung velocity, which is the vertical vibration velocity of the vehicle body, is input and that cuts signal components with frequencies higher than the sprung resonance frequency of the vehicle body, and a damping coefficient control means that changes the damping coefficient of the suspension based on the filtered sprung velocity. In Patent Document 1, the bandpass filter is used to cut high-frequency components, thereby reducing the effect on the control of the damping coefficient caused by the phase shift between the actual sprung velocity and the filtered sprung velocity.

Japanese Patent Application Publication No. 6-166314

Conventionally, the position of the zero moment point of a vehicle has been calculated. The zero moment point of a vehicle refers to the point where a line segment extending from the position of the center of gravity of the vehicle in the direction of the resultant force of the gravity of the vehicle and the inertial force acting on the vehicle intersects with the road surface.

Figure 3 is a diagram showing the positional relationship between the zero moment point ZMP and the support polygon S. In Figure 3, the X-axis represents the vehicle's longitudinal direction, the Y-axis represents the vehicle's width direction, and the Z-axis represents the height direction. The support polygon S is a polygon with vertices at the ground contact points of the vehicle's multiple wheels. In the example of Figure 3, since the vehicle has four wheels, the support polygon S is a quadrangle with vertices at the ground contact points of each wheel.

The risk of the vehicle tipping over is evaluated based on the position of the zero moment point ZMP relative to the support polygon S. The closer the zero moment point ZMP is to the center of the support polygon S, the lower the risk of the vehicle tipping over is evaluated. In other words, the farther the zero moment point ZMP is from the center of the support polygon S, the higher the risk of the vehicle tipping over is evaluated. If the center of gravity of the vehicle is directly above the center of the support polygon S, the greater the horizontal component of the inertial force acting on the vehicle (for example, the greater the vehicle's speed when turning a curve), the farther the zero moment point ZMP will be from the center of the support polygon S. Also, if the vehicle is on a flat road surface, the heavier the vehicle's weight (the greater the gravity), the less likely the position of the zero moment point ZMP will change due to inertial force.

There are several methods for calculating the position of the zero moment point (ZMP). For example, the position of the zero moment point (ZMP) can be calculated based on the acceleration of the center of gravity of the vehicle in three axial directions (front-rear, width, and height) and the angular velocity of the center of gravity of the vehicle about the three axes.

Fig. 4 is a schematic diagram of a vehicle, and a diagram showing parameters required for calculating the position of the zero moment point ZMP. In Fig. 4 as well, the X-axis represents the vehicle longitudinal direction, the Y-axis represents the vehicle width direction, and the Z-axis represents the height direction. In Fig. 4, the positions of the four wheels _T1 to _T4 of the vehicle and the center of gravity C of the vehicle are shown. Fig. 4 also shows a support polygon S (a quadrangle with the ground contact points of the wheels _T1 to _T4 as vertices). The following formulas (1) and (2) are examples of formulas for calculating the position of the zero moment point ZMP based on the acceleration of the center of gravity of the vehicle in the three axial directions and the angular velocity of the center of gravity of the vehicle around the three axes.

In formula (1) and formula (2), x _zmp and y _zmp represent the X and Y coordinates of the zero moment point ZMP in the XY coordinate system when the intersection O of the road surface and the perpendicular line from the center of gravity C to the road surface is set as the origin. m represents the mass of the vehicle, and h represents the height of the center of gravity C from the road surface. _{a x} , a _y , and a _z are elements of the translational acceleration vector a = [a _x a _y a _z ] ^T of the center of gravity C in the three axial directions. g _x , g _y , and g _z are elements of the gravitational acceleration vector g = [g _x g _y g _z ] ^T of the center of gravity C in the axial directions. In this specification, the acceleration of the center of gravity C is a concept that includes the translational acceleration vector a and the gravitational acceleration vector g. Furthermore, L _x and L _y are elements of an angular momentum vector L=[L _x L _y L _z ] ^T about the center of gravity C around the three axes. The time derivative of the angular momentum vector L is expressed by the following equation (3).

In equation (3), I is the inertia tensor around the center of gravity C, and ω is the angular velocity vector ω=[ω _x ω _y ω _z ] ^T of the center of gravity C.

Note that the translational acceleration vector a and the gravitational acceleration vector g in equations (1) and (2) are obtained by an acceleration sensor provided near the center of gravity C. Also, the angular velocity vector ω in equation (3) is obtained by an angular velocity sensor provided near the center of gravity C.

If it is possible to detect the ground load of each of the wheels T ₁ to T ₄ , for example by providing a ground load sensor that detects the ground load of each of the wheels T ₁ to T ₄ , it is also possible to calculate the position of the zero moment point ZMP based on the ground load of each of the wheels T ₁ to T _4. The following formulas ( ₄ ) and (5) are examples of formulas for calculating the position of the zero moment point ZMP based on the ground load of each of the wheels T 1 to T ₄ .

In formulas (4) and (5), F ₁ to F ₄ represent the ground loads of the wheels T ₁ to T ₄ , respectively. _{l f} is the distance in the vehicle longitudinal direction from the center of gravity C to the ground contact point of the front wheel (T1 or T2) of the vehicle, and l _r is the distance in the vehicle longitudinal direction from the center of gravity C to the ground contact point of the rear wheel (T3 or T4) of the vehicle. _{t l} is the distance in the vehicle width direction from the center of gravity C to the ground contact point of the left wheel (T1 or T3) of the vehicle, and _tr is the distance in the vehicle width direction from the center of gravity C to the ground contact point of the right wheel (T2 or T4) of the vehicle.

As described above, the position of the zero moment point ZMP can be calculated based on the acceleration and angular velocity of the center of gravity C, or the ground load of each wheel. Here, if the vehicle is vibrating, the vibration will affect the acceleration and angular velocity of the center of gravity C, and the ground load of each wheel. In other words, the acceleration sensor detects the acceleration of the center of gravity C including the influence of the vehicle vibration, the angular velocity sensor detects the angular velocity of the center of gravity C including the influence of the vehicle vibration, and the ground load sensor detects the ground load of each wheel including the influence of the vehicle vibration.

On the other hand, vehicles generally have suspensions. Suspensions are shock-absorbing devices that are installed between the vehicle body and the wheels to prevent shocks from the road surface from being transmitted to the vehicle body. Suspensions include springs that absorb shocks while supporting the weight of the vehicle.

Here, high-frequency components of vehicle vibrations are characterized by being easily absorbed by the suspension. In particular, for rolling vibrations with the rotation axis in the longitudinal direction of the vehicle (i.e., the X-axis), vibrations with frequencies higher than the vehicle's roll resonance frequency are easily absorbed by the suspension, and for pitching vibrations with the rotation axis in the width direction of the vehicle (i.e., the Y-axis), vibrations with frequencies higher than the vehicle's pitch resonance frequency are easily absorbed by the suspension. The roll resonance frequency is the vehicle's natural frequency related to the roll vibration, and the pitch resonance frequency is the vehicle's natural frequency related to the pitch vibration. Incidentally, the roll resonance frequency and pitch resonance frequency are on the order of a few Hz (e.g., 2 to 3 Hz).

Vibrations with frequencies higher than the roll resonance frequency and pitch resonance frequency are quickly absorbed by the suspension, so vibrations in these frequency bands do not have much effect on the position of the zero moment point ZMP. Therefore, in order to calculate the position of the zero moment point ZMP more accurately, it is advisable to calculate the position of the zero moment point ZMP based on the acceleration of the center of gravity C and the angular velocity of the center of gravity C, or the ground contact load of each wheel, excluding the effects of vibrations with frequencies higher than the roll resonance frequency and pitch resonance frequency of the vehicle.

The purpose of the vehicle zero moment point calculation device disclosed in this specification is to calculate the position of the vehicle's zero moment point by reducing the effects of vibrations that are absorbed by the suspension and have frequencies higher than the vehicle's roll resonance frequency and pitch resonance frequency.

The zero moment point calculation device of a vehicle disclosed in this specification is a zero moment point calculation device that calculates the position of the zero moment point of a vehicle having a suspension, and is characterized by comprising an acceleration sensor that detects the acceleration of the center of gravity of the vehicle in three axial directions, i.e., the vehicle longitudinal direction, the vehicle width direction, and the vehicle height direction; an angular velocity sensor that detects the angular velocity of the center of gravity of the vehicle around the three axes; a low-pass filter to which the detection signals of the acceleration sensor and the angular velocity sensor are input, the low-pass filter reducing signal components of frequencies higher than the larger of the roll resonance frequency, which is the resonance frequency of the vehicle related to rolling vibrations with the vehicle longitudinal direction as the rotation axis, and the pitch resonance frequency, which is the resonance frequency of the vehicle related to pitching vibrations with the vehicle width direction as the rotation axis; a differentiation processing unit that differentiates the detection signal of the angular velocity sensor; and a calculation unit that calculates the position of the zero moment point of the vehicle based on the detection signals of the acceleration sensor and the angular velocity sensor after the low-pass filter has been applied, and the detection signal of the angular velocity sensor applied and differentiated by the low-pass filter.

According to this configuration, the low-pass filter reduces signal components in the detection signals of the acceleration sensor and the angular velocity sensor that are greater than the larger of the vehicle's roll resonance frequency and pitch resonance frequency (referred to as the "selected resonance frequency" in this specification). Signal components with frequencies greater than the selected resonance frequency correspond to high-frequency components of the vehicle vibrations that are absorbed by the suspension, and are signal components that should not be used in calculating the position of the zero moment point. The calculation unit then calculates the position of the zero moment point based on the detection signals of the acceleration sensor and the angular velocity sensor to which the low-pass filter has been applied. This makes it possible to calculate the position of the zero moment point by reducing the influence of high-frequency components of the vehicle vibrations that are absorbed by the suspension. In other words, it is possible to calculate a more accurate position of the zero moment point.

The differential processing unit may differentiate the detection signal of the angular velocity sensor after the low-pass filter is applied.

The detection signal of the angular velocity sensor may suddenly show a large value. Such a signal is often noise, not an actual sudden change in the angular velocity of the center of gravity of the vehicle. If such noise is included in the detection signal of the angular velocity sensor, the time fluctuation of the detection signal will also be quite large in the noise portion. If the detection signal of the angular velocity sensor before the low-pass filter is applied is differentiated, such noise components will be emphasized. Even if the low-pass filter is then applied, there is a possibility that the emphasized noise components cannot be sufficiently reduced. According to this configuration, the detection signal of the angular velocity sensor after the low-pass filter is applied is differentiated, so that the noise included in the detection signal of the angular velocity sensor can be more effectively reduced, at least compared to the case of applying the low-pass filter after differentiation.

The zero moment point calculation device for a vehicle disclosed in this specification is a zero moment point calculation device that calculates the position of the zero moment point of a vehicle having a suspension, and is characterized by comprising: a ground load sensor that detects the ground load of each wheel of the vehicle; a low-pass filter to which the detection signal of the ground load sensor is input, the low-pass filter reducing signal components of frequencies higher than the larger of the roll resonance frequency, which is the resonance frequency of the vehicle related to rolling vibrations whose rotation axis is the longitudinal direction of the vehicle, and the pitch resonance frequency, which is the resonance frequency of the vehicle related to pitching vibrations whose rotation axis is the width direction of the vehicle; and a calculation unit that calculates the position of the zero moment point of the vehicle based on the ground load sensor after the low-pass filter has been applied.

According to this configuration, the low-pass filter reduces signal components of frequencies higher than the selected resonant frequency in the detection signal of the ground load sensor. Signal components of frequencies higher than the selected resonant frequency correspond to high-frequency components of the vehicle vibration absorbed by the suspension, and are signal components that should not be used in calculating the position of the zero moment point. The calculation unit then calculates the position of the zero moment point based on the detection signal of the ground load sensor to which the low-pass filter has been applied. This makes it possible to calculate the position of the zero moment point by reducing the influence of high-frequency components of the vehicle vibration absorbed by the suspension. In other words, it is possible to calculate the position of the zero moment point more accurately.

The vehicle zero moment point calculation device disclosed in this specification can calculate the position of the vehicle's zero moment point by reducing the effects of vibrations that are absorbed by the suspension and have frequencies higher than the vehicle's roll resonance frequency and pitch resonance frequency.

FIG. 2 is a functional block diagram of a zero moment point calculation device according to the first embodiment. FIG. 11 is a functional block diagram of a zero moment point calculation device according to a second embodiment. FIG. 13 is a diagram showing the positional relationship between the zero moment point and the support polygon. FIG. 2 is a schematic diagram of a vehicle showing parameters required for calculating the position of the zero moment point;

First Embodiment
Fig. 1 is a functional block diagram of a zero moment point calculation device 10 for a vehicle according to a first embodiment. Fig. 4 can also be referred to as a drawing showing the first embodiment, so hereinafter, the zero moment point calculation device 10 according to the first embodiment will be described with reference to Figs. 1 and 4.

The zero moment point calculation device 10 is provided in a vehicle such as an automobile. In this embodiment, the zero moment point calculation device 10 is provided in a four-wheeled vehicle.

A vehicle (hereinafter simply referred to as "vehicle") in which the zero moment point calculation device 10 is installed is provided with a suspension. As described above, a suspension is a shock-absorbing device that is provided between the vehicle body and the wheels to prevent shocks from the road surface from being transmitted to the vehicle body, and is composed of springs that absorb shocks while supporting the weight of the vehicle.

The acceleration sensor 12 is a sensor that detects the acceleration of the center of gravity C of the vehicle in three axial directions, namely, the vehicle longitudinal direction (X-axis direction), the vehicle width direction (Y-axis direction), and the height direction (Z-axis direction). The acceleration sensor 12 is provided in the vicinity of the center of gravity C. The acceleration detected by the acceleration sensor 12 includes the translational acceleration of the center of gravity C (corresponding to _ax , _ay , and _az in the formulas (1) and (2)) and the gravitational acceleration (corresponding to _gx , _gy , and _gz in the formulas (1) and (2)). That is, the acceleration sensor 12 detects the translational acceleration vector and the gravitational acceleration vector of the center of gravity C. The acceleration sensor 12 continuously detects the acceleration of the center of gravity C in each axial direction. That is, the acceleration sensor 12 detects the time change of the acceleration of the center of gravity C in each axial direction. The number of times the acceleration changes in the direction per unit time in each axial direction is the frequency of the acceleration of the center of gravity C in each axial direction.

The detection signal of the acceleration sensor 12 includes the effects of vehicle vibration. In particular, in this embodiment, the acceleration sensor 12 detects the acceleration of the center of gravity C in three axial directions, so the detection signal of the acceleration sensor 12 includes the effects of both rolling vibration, whose rotation axis is in the longitudinal direction of the vehicle, and pitching vibration, whose rotation axis is in the width direction of the vehicle.

The angular velocity sensor 14 is a sensor that detects the angular velocity of the center of gravity C of the vehicle around three axes, the X-axis, the Y-axis, and the Z-axis. That is, the angular velocity sensor 14 detects the angular velocity vector of the center of gravity C. The angular velocity sensor 14 also continuously detects the angular velocity of the center of gravity C around each axis. That is, the angular velocity sensor 14 detects the change over time in the angular velocity of the center of gravity C around each axis. The number of times the angular velocity changes direction per unit time around each axis is the frequency of the acceleration of the center of gravity C around each axis.

The detection signal of the angular velocity sensor 14 also includes the effects of vehicle vibration. In particular, in this embodiment, the angular velocity sensor 14 detects the angular velocity of the center of gravity C around three axes, so the detection signal of the angular velocity sensor 14 also includes the effects of both rolling vibration and pitching vibration.

The detection signals of the acceleration sensor 12 and the angular velocity sensor 14 are each input to a low-pass filter 16.

The low-pass filter 16 is a filter that reduces high-frequency components of the detection signals of the acceleration sensor 12 and the angular velocity sensor 14. In particular, the low-pass filter 16 reduces signal components with frequencies higher than a selected resonance frequency, which is the higher of the roll resonance frequency and the pitch resonance frequency of the vehicle. As described above, the roll resonance frequency is the resonance frequency of the vehicle related to rolling vibration, and the pitch resonance frequency is the resonance frequency of the vehicle related to pitching vibration. The roll resonance frequency and the pitch resonance frequency are generally different frequencies from each other. The roll resonance frequency and the pitch resonance frequency of the vehicle can be obtained in advance by vehicle analysis, etc.

The detection signal of the acceleration sensor 12 to which the low-pass filter 16 is applied is a detection signal in which signal components with frequencies higher than the selected resonance frequency are reduced while signal components below the selected resonance frequency are maintained. Also, the detection signal of the angular velocity sensor 14 to which the low-pass filter 16 is applied is a detection signal in which signal components with frequencies higher than the selected resonance frequency are reduced while signal components below the selected resonance frequency are maintained.

As described above, both the acceleration sensor 12 and the angular velocity sensor 14 output detection signals that are affected by both rolling vibration and pitching vibration. Therefore, in this embodiment, in order to retain as much of the detection signal in the frequency band necessary for calculating the position of the zero moment point ZMP as possible, the low-pass filter 16 reduces signal components with frequencies higher than the larger of the vehicle's roll resonance frequency and pitch resonance frequency (i.e., the selected resonance frequency).

If the low-pass filter 16 reduces signal components with frequencies greater than the smaller of the vehicle's roll and pitch resonance frequencies, the low-pass filter 16 may reduce signal components in a frequency band that would be better used to calculate the position of the zero moment point ZMP. For example, if the roll resonance frequency is greater than the pitch resonance frequency, and the low-pass filter 16 reduces signal components with frequencies greater than the pitch resonance frequency, the signal components that would be better used to calculate the position of the zero moment point ZMP (signal components that represent rolling vibrations with frequencies greater than the pitch resonance frequency and less than or equal to the roll resonance frequency) will be reduced.

In this embodiment, taking into account the sampling theorem, the cutoff frequency of the low-pass filter 16 is set to twice the selected resonant frequency in order to reduce signal components with frequencies greater than the selected resonant frequency while maintaining signal components equal to or less than the selected resonant frequency. For example, if the selected resonant frequency is 3 Hz, the cutoff frequency of the low-pass filter 16 is set to 6 Hz.

The detection signals of the acceleration sensor 12 and the angular velocity sensor 14 to which the low-pass filter 16 has been applied are input to the calculation unit 20.

The differential processing unit 18 differentiates the detection signal of the angular velocity sensor 14. As shown in FIG. 1, in this embodiment, the differential processing unit 18 differentiates the detection signal of the angular velocity sensor 14 after the low-pass filter 16 is applied.

The differential processing unit 18 may differentiate the detection signal of the angular velocity sensor 14 before the low-pass filter 16 is applied. However, as described below, in order to reduce the effect of noise contained in the detection signal of the angular velocity sensor 14 in the calculation of the position of the zero moment point ZMP, it is preferable that the differential processing unit 18 differentiates the detection signal of the angular velocity sensor 14 after the low-pass filter 16 is applied.

The detection signal of the angular velocity sensor 14 may suddenly show a large value. Such a signal is often noise, not an actual sudden change in the angular velocity of the center of gravity C. If such noise is included in the detection signal of the angular velocity sensor 14, the time fluctuation of the detection signal will also be quite large in the noise portion. If the detection signal of the angular velocity sensor 14 before the low-pass filter 16 is applied is differentiated, such noise components will be emphasized. Even if the low-pass filter 16 is then applied, there is a possibility that the emphasized noise components cannot be sufficiently reduced. If the low-pass filter 16 is applied before differentiation, the noise included in the detection signal of the angular velocity sensor 14 can be more effectively reduced, at least compared to the case where the low-pass filter 16 is applied after differentiation.

The detection signal of the angular velocity sensor 14, which has been applied to the low-pass filter 16 and differentiated by the differential processing unit 18, is input to the calculation unit 20.

The calculation unit 20 calculates the position of the zero moment point ZMP of the vehicle based on the detection signals of the acceleration sensor 12 and the angular velocity sensor 14 after the low-pass filter 16 has been applied, and the detection signal of the angular velocity sensor 14 after the low-pass filter 16 has been applied and differentiated.

The calculation unit 20 calculates the position of the zero moment point ZMP based on the acceleration and angular velocity of the center of gravity C, which are similar to the above-mentioned equations (1), (2), and (3), but to which the low-pass filter 16 is applied. That is, the calculation unit 20 calculates the position of the zero moment point ZMP by the following equations (6), (7), and (8).

は、ローパスフィルタ１６が適用され、且つ、微分処理部１８によって微分された重心Ｃの角速度ベクトルを表す。 In equations (6) and (7), _a'x , _a'y , and _a'z represent elements of the translational acceleration vector a' of the center of gravity C after the low-pass filter 16 has been applied, and _g'x , _g'y , and _g'z represent elements of the gravitational acceleration vector g' of the center of gravity C after the low-pass filter 16 has been applied. In equation (8), ω' represents the angular velocity vector ω _' =[ _ω'xω'yω'z ] ^T of the center of gravity C after the low-pass filter 16 has been applied. In addition _,

represents the angular velocity vector of the center of gravity C applied with the low-pass filter 16 and differentiated by the differential processing unit 18.

The driving control unit (not shown in FIG. 1) of the vehicle controls the steering and braking/driving forces based on the position of the zero moment point ZMP calculated by the zero moment point calculation device 10 so that the zero moment point ZMP approaches the center of the support polygon S. For example, when the vehicle enters a curve at high speed, the driving control unit performs driving control such as decelerating the vehicle according to the distance between the center of the vehicle's support polygon S and the zero moment point ZMP.

The outline of the zero moment point calculation device 10 according to the first embodiment has been described above. According to the zero moment point calculation device 10, high-frequency components (particularly signal components with frequencies higher than the selected resonant frequency) contained in the detection signals of the acceleration sensor 12 and the angular velocity sensor 14 that should not be used in the calculation of the position of the zero moment point ZMP are reduced by the low-pass filter 16. The calculation unit 20 then calculates the position of the zero moment point ZMP based on the detection signals of the acceleration sensor 12 and the angular velocity sensor 14 to which the low-pass filter 16 has been applied. This makes it possible to calculate the position of the zero moment point ZMP by reducing the influence of high-frequency components of the vibration of the vehicle absorbed by the suspension, and to calculate the position of the zero moment point ZMP more accurately.

If the position of the zero moment point ZMP is calculated based on the detection signals of the acceleration sensor 12 and the angular velocity sensor 14 that contain signal components with frequencies higher than the selected resonant frequency, the zero moment point ZMP will be farther away from the center of the support polygon S than it actually is, and the risk of tipping over will be evaluated as being unreasonably high. If the driving control unit were to perform driving control based on the position of the zero moment point ZMP, the driving control unit may perform driving control that is actually unnecessary. According to this embodiment, the position of the zero moment point ZMP is calculated more accurately, making it possible to reduce unnecessary driving control by the driving control unit.

Second Embodiment
Fig. 2 is a functional block diagram of a zero moment point calculation device 30 for a vehicle according to the second embodiment. Fig. 4 can also be referred to as a drawing showing the second embodiment, so hereinafter, the zero moment point calculation device 30 according to the second embodiment will be described with reference to Figs. 2 and 4.

In the first embodiment, the position of the zero moment point ZMP was calculated based on the detection signals of the acceleration sensor 12 and the angular velocity sensor 14, but in the second embodiment, the position of the zero moment point ZMP is calculated based on the detection signal of the ground load sensor 32. Other points are the same as in the first embodiment, so a description will be omitted.

The ground load sensor 32 is a sensor that detects the ground load of each wheel (wheels T ₁ to T ₄ in the example of FIG. 4) of the vehicle. The ground load sensor 32 is provided on each of the wheels T ₁ to T ₄ .

The detection signal of the ground load sensor 32 includes the influence of the vibration of the vehicle. For example, when the vicinity of the vehicle wheel moves downward due to the vibration of the vehicle, the spring of the suspension provided on the wheel shrinks and the ground load increases, and when the vicinity of the vehicle wheel moves upward due to the vibration of the vehicle, the spring of the suspension provided on the wheel expands and the ground load decreases. In particular, the detection signal of the ground load sensor 32 provided on each of the wheels _T1 to _T4 includes the influence of both the rolling vibration and the pitching vibration.

The detection signal of the ground load sensor 32 is input to the low-pass filter 34.

The low-pass filter 34 is a filter that reduces high-frequency components of the detection signal of the ground load sensor 32. Similarly in the second embodiment, the low-pass filter 34 reduces signal components with frequencies higher than the selected resonance frequency, which is the higher of the vehicle's roll resonance frequency and pitch resonance frequency.

The detection signal of the ground load sensor 32 to which the low-pass filter 34 is applied is a detection signal in which signal components with frequencies greater than the selected resonant frequency are reduced while signal components below the selected resonant frequency are maintained.

As described above, the ground load sensor 32 outputs a detection signal that is affected by both rolling and pitching vibrations. Therefore, in the second embodiment, in order to retain as much of the detection signal as possible in the frequency band required for calculating the position of the zero moment point ZMP, the low-pass filter 16 reduces signal components with frequencies higher than the larger of the vehicle's roll resonance frequency and pitch resonance frequency (i.e., the selected resonance frequency).

The detection signal of the ground load sensor 32 to which the low-pass filter 34 is applied is input to the calculation unit 36.

The calculation unit 36 calculates the position of the vehicle's zero moment point ZMP based on the detection signal of the ground load sensor 32 after the low-pass filter 34 has been applied.

The calculation unit 36 calculates the position of the zero moment point ZMP based on the ground contact loads of the wheels _T1 to _T4 using equations similar to the above-mentioned equations (4) and (5), but to which the low-pass filter 34 is applied. That is, the calculation unit 36 calculates the position of the zero moment point ZMP using the following equations (9) and (10).

In equations (9) and (10), F' ₁ , F' ₂ , F' ₃ , and F' ₄ represent the ground contact loads of the wheels T ₁ to T ₄ after the low pass filter 34 has been applied.

The outline of the zero moment point calculation device 30 according to the second embodiment has been described above. According to the zero moment point calculation device 30, high frequency components (particularly signal components with frequencies higher than the selected resonant frequency) contained in the detection signal of the ground load sensor 32 that should not be used in the calculation of the position of the zero moment point ZMP are reduced by the low pass filter 34. The calculation unit 36 then calculates the position of the zero moment point ZMP based on the detection signal of the ground load sensor 32 to which the low pass filter 34 has been applied. This makes it possible to calculate the position of the zero moment point ZMP by reducing the influence of high frequency components of the vibration of the vehicle absorbed by the suspension, and to calculate the position of the zero moment point ZMP more accurately.

Even in the second embodiment, if the position of the zero moment point ZMP is calculated based on the detection signal of the ground load sensor 32 that contains a signal component with a frequency higher than the selected resonant frequency, the zero moment point ZMP will be farther away from the center of the support polygon S than it actually is, and the risk of tipping over will be evaluated as being unreasonably high. If the driving control unit performs driving control based on the position of the zero moment point ZMP, the driving control unit may perform driving control that is actually unnecessary. According to this embodiment, the position of the zero moment point ZMP is calculated more accurately, so unnecessary driving control by the driving control unit can be reduced.

The above describes an embodiment of the vehicle zero moment point calculation device according to the present disclosure, but the vehicle zero moment point calculation device according to the present disclosure is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the device.

10, 30 Zero moment point calculation device, 12 Acceleration sensor, 14 Angular velocity sensor, 16, 34 Low pass filter, 18 Differential processing unit, 20, 36 Calculation unit, 32 Ground load sensor, C Center of gravity, ZMP Zero moment point.

Claims (3)

A zero moment point calculation device for calculating a position of a zero moment point of a vehicle having a suspension, comprising:
an acceleration sensor for detecting acceleration of the center of gravity of the vehicle in three axial directions, i.e., a longitudinal direction, a width direction, and a height direction of the vehicle;
an angular velocity sensor for detecting an angular velocity of a center of gravity of the vehicle about the three axes;
a low-pass filter to which detection signals from the acceleration sensor and the angular velocity sensor are input, the low-pass filter reducing signal components of a frequency higher than the larger of a roll resonance frequency, which is a resonance frequency of the vehicle related to rolling vibrations whose rotation axis is in the vehicle longitudinal direction, and a pitch resonance frequency, which is a resonance frequency of the vehicle related to pitching vibrations whose rotation axis is in the vehicle width direction; and
a differential processing unit that differentiates a detection signal of the angular velocity sensor;
a calculation unit that calculates a position of a zero moment point of the vehicle based on the detection signals of the acceleration sensor and the angular velocity sensor after the low-pass filter has been applied, and the detection signal of the angular velocity sensor after the low-pass filter has been applied and differentiation has been performed; and
A vehicle zero moment point calculation device comprising: The differential processing unit differentiates the detection signal of the angular velocity sensor after the low-pass filter is applied.
2. The zero moment point calculation device according to claim 1 . A zero moment point calculation device for calculating a position of a zero moment point of a vehicle having a suspension, comprising:
a ground load sensor for detecting a ground load of each wheel of the vehicle;
a low-pass filter to which a detection signal of the ground load sensor is input, the low-pass filter reducing signal components of a frequency higher than the larger of a roll resonance frequency, which is a resonance frequency of the vehicle related to rolling vibrations whose rotation axis is in the vehicle longitudinal direction, and a pitch resonance frequency, which is a resonance frequency of the vehicle related to pitching vibrations whose rotation axis is in the vehicle width direction;
a calculation unit that calculates a position of a zero moment point of the vehicle based on the ground load sensor after the low pass filter is applied;
A vehicle zero moment point calculation device comprising:

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