Vehicle zero moment point calculation device

Abstract

To provide a zero moment point calculation unit of a vehicle which calculates a position of a zero moment point of a vehicle while reducing an influence of vibrations absorbed by a suspension with frequencies larger than a roll resonance frequency and a pitch resonance frequency of the vehicle.SOLUTION: A zero moment point calculation unit of a vehicle comprises: an acceleration sensor 12 which detects acceleration of a center C of gravity of the vehicle in a vehicle longitudinal direction (X-axis direction), a vehicle width direction (y-axis direction), and a height direction (z-axis direction); an angular velocity sensor 14 which detects angular speed of the center C of gravity of the vehicle around an X axis, a Y axis, and a Z axis; a low pass filter 16 which reduces signal components in detection signals of the acceleration sensor 12 and the angular velocity sensor 14 in which frequencies of the signal components are larger than a resonance frequency that is a larger one of a roll resonance frequency of the vehicle and a pitch resonance frequency; and an arithmetic logical unit 20 which calculates a position of a zero moment point ZMP of the vehicle based on the detection signals of the acceleration sensor 12 and the angular velocity sensor 14 after applying the low pass filter 14 and based on the detection signal of the angular velocity sensor 14 to which the low pass filter is applied and which is differentiated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This specification discloses an improvement to a vehicle zero moment point calculation device. [Background technology]

[0002] Patent Document 1 discloses a vehicle suspension system including a suspension provided between the vehicle body and each wheel, with a variable damping coefficient, a bandpass filter to which the sprung velocity, which is the vertical vibration velocity of the vehicle body, is input and which cuts signal components of frequencies higher than the sprung resonance frequency of the vehicle body, and a damping coefficient control means which changes the damping coefficient of the suspension based on the filtered sprung velocity.In Patent Document 1, by cutting high-frequency components using the bandpass filter, the influence on damping coefficient control caused by a phase shift between the actual sprung velocity and the filtered sprung velocity is reduced. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-166314 Summary of the Invention [Problem to be solved by the invention]

[0004] 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 center of gravity of the vehicle in the direction of the resultant force of gravity and the inertial force acting on the vehicle intersects with the road surface.

[0005] FIG. 3 is a diagram showing the positional relationship between the zero moment point ZMP and the support polygon S. In FIG. 3, the X axis represents the longitudinal direction of the vehicle, the Y axis represents the width direction of the vehicle, 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 FIG. 3, since the vehicle has four wheels, the support polygon S is a quadrangle with vertices at the ground contact points of each wheel.

[0006] 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 position of 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 position of 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 corner), the farther the position of the zero moment point ZMP will be from the center of the support polygon S. Furthermore, when 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.

[0007] 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 directions of the vehicle) and the angular velocity of the center of gravity of the vehicle about the three axes.

[0008] 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, the X axis represents the longitudinal direction of the vehicle, the Y axis represents the width direction of the vehicle, 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. In addition, FIG. 4 also shows a support polygon S (a quadrangle with vertices at the contact points of the wheels T1 to T4). 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 about the three axes.

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[0009] 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 perpendicular line drawn from the center of gravity C to the road surface and the road surface is taken 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 , a z is the translational acceleration vector a=[a x a y a z ] T is an element of g x , g y , g z is the gravitational acceleration vector g=[g x g y g z ] T 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. x , L y is the angular momentum vector L=[L x L y L z ] T The time derivative of the angular momentum vector L is expressed by the following equation (3).

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[0010] 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 is.

[0011] 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. The angular velocity vector ω in equation (3) is obtained by an angular velocity sensor provided near the center of gravity C.

[0012] If the ground load of each wheel T1 to T4 can be detected by providing a ground load sensor that detects the ground load of each wheel T1 to T4, the position of the zero moment point ZMP can also be calculated based on the ground load of each wheel T1 to T4. 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 wheel T1 to T4.

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[0013] In equations (4) and (5), F1 to F4 represent the ground contact loads of wheels T1 to T4, respectively. f is the distance in the longitudinal direction of the vehicle from the center of gravity C to the contact point of the front wheel (T1 or T2) of the vehicle, and l r is the distance in the longitudinal direction of the vehicle from the center of gravity C to the contact point of the rear wheel (T3 or T4) of the vehicle. l is the distance in the vehicle width direction from the center of gravity C to the contact point of the left wheel (T1 or T3) of the vehicle, and t r 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.

[0014] 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 contact load of each wheel. Here, when the vehicle is vibrating, the vibration affects the acceleration and angular velocity of the center of gravity C, and the ground contact 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 contact load sensor detects the ground contact load of each wheel including the influence of the vehicle vibration.

[0015] On the other hand, vehicles are generally equipped with suspensions. A suspension is a shock absorber that is installed between the vehicle body and the wheels to prevent shocks from the road surface from being transmitted to the vehicle body. The suspension is composed of springs that absorb shocks while supporting the weight of the vehicle.

[0016] Here, high-frequency components of vehicle vibrations are characterized by being easily absorbed by the suspension. In particular, for roll vibrations whose rotation axis is 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 pitch vibrations whose rotation axis is in the vehicle's width direction (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 roll vibrations, and the pitch resonance frequency is the vehicle's natural frequency related to pitch vibrations. Incidentally, the roll resonance frequency and pitch resonance frequency are on the order of a few Hz (for example, 2 to 3 Hz).

[0017] Vibrations of 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 and angular velocity of the center of gravity C or the ground contact load of each wheel, excluding the effects of vibrations of frequency components higher than the roll resonance frequency and pitch resonance frequency of the vehicle.

[0018] The purpose of the vehicle zero moment point calculation device disclosed in this specification is to calculate the position of the vehicle 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. [Means for solving the problem]

[0019] 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: an acceleration sensor that detects the acceleration of the center of gravity of the vehicle in three axial directions, i.e., the longitudinal direction of the vehicle, the width direction of the vehicle, and the height direction; an angular velocity sensor that detects the angular velocity of the center of gravity of the vehicle about these 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 frequencies higher than the larger of a roll resonance frequency that is the resonance frequency of the vehicle related to rolling vibrations about the longitudinal direction of the vehicle as the axis of rotation, and a pitch resonance frequency that is the resonance frequency of the vehicle related to pitching vibrations about the width direction of the vehicle as the axis of rotation; 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 that has been applied and differentiated by the low-pass filter.

[0020] 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 have a frequency higher 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 a frequency higher than the selected resonance frequency correspond to high-frequency components of 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 while reducing the influence of high-frequency components of vehicle vibrations that are absorbed by the suspension. In other words, it is possible to calculate the position of the zero moment point more accurately.

[0021] The differential processing unit may differentiate the detection signal of the angular velocity sensor after the low-pass filter has been applied.

[0022] The detection signal of the angular velocity sensor may suddenly exhibit a large value. Such a signal is often noise, not a sudden change in the angular velocity of the vehicle's center of gravity. If such noise is included in the detection signal of the angular velocity sensor, the time fluctuation of the detection signal in the noise portion will also be significantly large. 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 subsequently applied, the emphasized noise components may not be sufficiently reduced. According to this configuration, the detection signal of the angular velocity sensor after the low-pass filter is applied is differentiated, thereby more effectively reducing the noise included in the detection signal of the angular velocity sensor than when the low-pass filter is applied at least after differentiation.

[0023] 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 a detection signal of the ground load sensor is input, the low-pass filter reducing signal components of frequencies higher than the larger of a roll resonance frequency that is the resonance frequency of the vehicle related to rolling vibrations whose rotation axis is in the longitudinal direction of the vehicle, and a pitch resonance frequency that is the resonance frequency of the vehicle related to pitching vibrations whose rotation axis is in the vehicle width direction; 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.

[0024] 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. The signal components of frequencies higher than the selected resonant frequency correspond to high-frequency components of 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 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 while reducing the influence of high-frequency components of vehicle vibrations that are absorbed by the suspension. In other words, it is possible to calculate the position of the zero moment point more accurately. [Effects of the Invention]

[0025] 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. [Brief explanation of the drawings]

[0026] [Figure 1]FIG. 1 is a functional block diagram of a zero moment point calculation device according to a first embodiment. [Figure 2] FIG. 10 is a functional block diagram of a zero moment point calculation device according to a second embodiment. [Figure 3] FIG. 10 is a diagram showing the positional relationship between the zero moment point and the support polygon. [Figure 4] FIG. 2 is a schematic diagram of a vehicle showing parameters required to calculate the position of the zero moment point. DETAILED DESCRIPTION OF THE INVENTION

[0027] First Embodiment Fig. 1 is a functional block diagram of a zero moment point calculation device 10 for a vehicle according to the first embodiment. Fig. 4 can also be referred to as a drawing illustrating the first embodiment, so the zero moment point calculation device 10 according to the first embodiment will be described below with reference to Figs. 1 and 4.

[0028] 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-wheel vehicle.

[0029] 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 absorber 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 configured to include a spring that absorbs shocks while supporting the weight of the vehicle.

[0030] The acceleration sensor 12 is a sensor that detects the acceleration of the center of gravity C of the vehicle in three axial directions: the longitudinal direction of the vehicle (X-axis direction), the width direction of the vehicle (Y-axis direction), and the height direction (Z-axis direction). The acceleration sensor 12 is provided near the center of gravity C. The acceleration detected by the acceleration sensor 12 is the translational acceleration of the center of gravity C (a in Equations (1) and (2)). x ,a y ,a z) and gravitational acceleration (equivalent to g in equations (1) and (2) x ,g y ,g z 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 change in the acceleration of the center of gravity C over time in each axial direction. The number of times the direction of acceleration changes per unit time in each axial direction is the frequency of the acceleration of the center of gravity C in each axial direction.

[0031] The detection signal of the acceleration sensor 12 includes the influence of vehicle vibrations. In particular, in this embodiment, the acceleration sensor 12 detects the acceleration of the center of gravity C in three axial directions, and therefore the detection signal of the acceleration sensor 12 includes the influence of both rolling vibrations whose rotation axis is in the longitudinal direction of the vehicle and pitching vibrations whose rotation axis is in the width direction of the vehicle.

[0032] 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 changes 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.

[0033] The influence of vehicle vibrations is also included in the detection signal of angular velocity sensor 14. In particular, in this embodiment, angular velocity sensor 14 detects the angular velocity of the center of gravity C around three axes, and therefore the detection signal of angular velocity sensor 14 also includes the influence of both rolling vibration and pitching vibration.

[0034] The detection signals of the acceleration sensor 12 and the angular velocity sensor 14 are input to a low-pass filter 16, respectively.

[0035] 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 of 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. In general, the roll resonance frequency and the pitch resonance frequency are often different from each other. The roll resonance frequency and the pitch resonance frequency of the vehicle can be obtained in advance by vehicle analysis or the like.

[0036] 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 of frequencies higher than the selected resonance frequency are reduced while signal components of frequencies equal to or lower than the selected resonance frequency are maintained. Similarly, 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 of frequencies higher than the selected resonance frequency are reduced while signal components of frequencies equal to or lower than the selected resonance frequency are maintained.

[0037] 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 of frequencies higher than the larger of the vehicle's roll resonance frequency and pitch resonance frequency (i.e., the selected resonance frequency).

[0038] If low-pass filter 16 were to reduce signal components of frequencies higher than the smaller of the roll resonance frequency and pitch resonance frequency of the vehicle, signal components in a frequency band that should be used to calculate the position of the zero moment point ZMP may be reduced by low-pass filter 16. For example, if the roll resonance frequency is higher than the pitch resonance frequency, reducing signal components of frequencies higher than the pitch resonance frequency by low-pass filter 16 would result in reducing signal components that should be used to calculate the position of the zero moment point ZMP (signal components that represent rolling vibrations with frequencies higher than the pitch resonance frequency and equal to or lower than the roll resonance frequency).

[0039] In this embodiment, in consideration of the sampling theorem, in order to reduce signal components with frequencies higher than the selected resonance frequency while maintaining signal components equal to or lower than the selected resonance frequency, the cutoff frequency of the low-pass filter 16 is set to a frequency twice the selected resonance frequency. For example, if the selected resonance frequency is 3 Hz, the cutoff frequency of the low-pass filter 16 is set to 6 Hz.

[0040] 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 a calculation unit 20 .

[0041] 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 has been applied.

[0042] 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 will be described below, in order to reduce the influence of noise contained in the detection signal of the angular velocity sensor 14 in calculating 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 has been applied.

[0043] The detection signal of angular velocity sensor 14 may suddenly exhibit large values. Such signals are often noise, rather than a sudden change in the angular velocity of center of gravity C. When such noise is included in the detection signal of angular velocity sensor 14, the time fluctuation of the detection signal in the noise portion also becomes significantly large. Differentiating the detection signal of angular velocity sensor 14 before applying low-pass filter 16 emphasizes such noise components. Applying low-pass filter 16 thereafter may not sufficiently reduce the emphasized noise components. Applying low-pass filter 16 before differentiation allows for more effective reduction of noise included in the detection signal of angular velocity sensor 14 than, at least, applying low-pass filter 16 after differentiation.

[0044] The detection signal of the angular velocity sensor 14 is applied to the low-pass filter 16 and differentiated by the differential processing unit 18 , and is input to the calculation unit 20 .

[0045] 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.

[0046] 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 using equations similar to the above-mentioned equations (1), (2), and (3), but to which the low-pass filter 16 has been applied. That is, the calculation unit 20 calculates the position of the zero moment point ZMP using the following equations (6), (7), and (8).

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[0047] In the formulas (6) and (7), a' x , a' y , a' zrepresents the elements of the translational acceleration vector a' of the center of gravity C after the low-pass filter 16 is applied, and g' x , g' y , g' z represents an element of the gravitational acceleration vector g' of the center of gravity C after the low-pass filter 16 is applied. In equation (8), ω' represents the angular velocity vector ω'=[ω' x ω' y ω' z ] T Also, the first term on the right side of equation (8)

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[0048] A 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.

[0049] The above is an overview of the zero moment point calculation device 10 according to the first embodiment. 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 and which should not be used in calculating 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 while reducing the influence of high-frequency components of vehicle vibrations absorbed by the suspension, thereby enabling a more accurate calculation of the position of the zero moment point ZMP.

[0050] 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 include 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, resulting in an unreasonably high risk of tipping over. 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, thereby reducing unnecessary driving control by the driving control unit.

[0051] 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 illustrating 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.

[0052] 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 thereof will be omitted.

[0053] The ground load sensor 32 is a sensor that detects the ground load of each wheel of the vehicle (wheels T1 to T4 in the example of FIG. 4). The ground load sensor 32 is provided on each of the wheels T1 to T4.

[0054] The detection signal of the ground load sensor 32 includes the influence of vehicle vibration. For example, when the vicinity of a vehicle wheel moves downward due to vehicle vibration, the suspension spring provided on that wheel contracts, increasing the ground load, and when the vicinity of a vehicle wheel moves upward due to vehicle vibration, the suspension spring provided on that wheel expands, decreasing the ground load. 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 rolling vibration and pitching vibration.

[0055] The detection signal of the ground load sensor 32 is input to a low-pass filter 34 .

[0056] 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 of frequencies higher than a selected resonance frequency, which is the higher of the roll resonance frequency and the pitch resonance frequency of the vehicle.

[0057] 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 of frequencies higher than the selected resonance frequency are reduced while signal components of frequencies equal to or lower than the selected resonance frequency are maintained.

[0058] As described above, the ground load sensor 32 outputs a detection signal that is affected by both rolling vibration and pitching vibration. Therefore, in the second embodiment as well, the low-pass filter 16 reduces signal components of frequencies higher than the larger of the vehicle's roll resonance frequency and pitch resonance frequency (i.e., the selected resonance frequency) in order to leave as much of the detection signal as possible in the frequency band necessary for calculating the position of the zero moment point ZMP.

[0059] The detection signal of the ground load sensor 32 to which the low-pass filter 34 has been applied is input to a calculation unit 36 ​​.

[0060] The calculation unit 36 ​​calculates the position of the zero moment point ZMP of the vehicle based on the detection signal of the ground load sensor 32 after the low-pass filter 34 has been applied.

[0061] The calculation unit 36 ​​calculates the position of the zero moment point ZMP based on the ground contact load of each 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 has been applied. That is, the calculation unit 36 ​​calculates the position of the zero moment point ZMP using the following equations (9) and (10).

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[0062] In the formulas (9) and (10), F'1, F'2, F'3, and F'4 represent the ground contact loads of the wheels T1 to T4 after the low-pass filter 34 has been applied.

[0063] The above is an overview of the zero moment point calculation device 30 according to the second embodiment. 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 calculating 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 while reducing the influence of high-frequency components of vehicle vibrations that are absorbed by the suspension, thereby enabling a more accurate calculation of the position of the zero moment point ZMP.

[0064] 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 includes 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, resulting in an unreasonably high risk of tipping over. 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, thereby reducing unnecessary driving control by the driving control unit.

[0065] 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 as long as they do not deviate from the spirit of the device. [Explanation of symbols]

[0066] 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

1. A zero moment point calculation device that calculates the 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., the longitudinal direction, the width direction, and the height direction of the vehicle; an angular velocity sensor for detecting the angular velocity of the center of gravity of the vehicle around 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 frequencies 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 the 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:

2. the differential processing unit differentiates the detection signal of the angular velocity sensor after the low-pass filter has been applied; 2. The zero moment point calculation device according to claim 1.

3. A zero moment point calculation device that calculates the 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 from the ground load sensor is input, the low-pass filter reducing signal components of frequencies 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 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 has been applied; A vehicle zero moment point calculation device comprising:

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