JP2020117196A - Vehicle motion state estimation device - Google Patents

Abstract

To make it possible to estimate a wheel speed generated by braking/driving torque with high accuracy.SOLUTION: A vehicle motion state estimation device 10 is mounted on a vehicle in which a vehicle body 1 and each wheel 2 are coupled via suspension units 5, 8 on front and rear wheel sides. The vehicle motion state estimation device 10 estimates actual wheel speed of each wheel 2 from a wheel speed detection value by each wheel speed sensor 11 and wheel speed change due to vertical motion of the vehicle. Wheel speed change due to vertical motion of the vehicle is determined by estimation calculation with a vehicle braking/driving torque, a vehicle acceleration, a vehicle travel resistant force, and suspension stroke change as parameters. Stroke change of the suspension units 5, 8 is determined by taking longitudinal force due to stroke into consideration.SELECTED DRAWING: Figure 1

Description

The present invention relates to a vehicle motion state estimation device capable of estimating a motion state when a vehicle is running, for example.

Generally, a vehicle such as a four-wheeled vehicle is equipped with a damping force variable damper such as a semi-active suspension in order to absorb vibration during traveling. As a control device for a damping force variable damper according to this type of conventional technology, a wheel speed sensor that detects a wheel speed of each wheel, and a wheel that calculates a wheel speed fluctuation amount based on a wheel speed detection value detected by the wheel speed sensor A speed variation amount calculating means, a state amount calculating means for calculating a state amount of the vehicle (a sprung speed of the vehicle body or a stroke speed of the suspension) based on the wheel speed variation amount, and the spring calculated by the state amount calculating means. A device including a control unit that controls the damping force of the damping force variable damper based on the upper speed or the stroke speed is known (see, for example, Patent Document 1).

JP, 2016-22830, A

By the way, in the prior art, for example, sensorless control that does not use an acceleration sensor, a vehicle height sensor, or the like is performed, and therefore control is performed by extracting a wheel speed change caused by vertical movement of the vehicle from the wheel speed. Since the wheel speed sensor that measures the wheel speed is divided into rotating parts and fixed parts, it is assumed that the measurement signal changes due to four factors: vehicle body pitching, suspension displacement, ground load fluctuation, and braking/driving torque. There is.

Among them, the wheel speed that changes depending on the braking/driving torque is estimated in consideration of the braking/driving torque of the vehicle, the vehicle acceleration, and the running resistance force (air resistance force, rolling resistance force, gradient resistance force). However, the prior art does not consider the longitudinal force applied to the vehicle body due to the stroke change of the suspension. Therefore, there is a problem that the actual wheel speed of each wheel of the vehicle cannot be estimated with high accuracy.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to consider a force due to a stroke change in addition to front and rear wheel torque, a vehicle acceleration, a running resistance force, and a braking/driving torque. An object of the present invention is to provide a vehicle motion state estimating device capable of estimating the wheel speed generated by the vehicle with high accuracy.

In order to solve the above-mentioned problems, the present invention is a vehicle motion state estimation device in a vehicle in which wheels and a vehicle body are coupled via a suspension, and a wheel speed detection value by a wheel speed sensor and a vertical motion of the vehicle. The configuration is such that the actual wheel speed of the wheel is estimated from the resulting wheel speed change, and the wheel speed change resulting from the vertical movement of the vehicle includes braking/driving torque of the vehicle, vehicle acceleration, and running resistance of the vehicle. And the stroke change of the suspension as parameters, and the stroke change of the suspension is obtained in consideration of the longitudinal force caused by the stroke.

According to the present invention, in addition to the front and rear wheel torques (that is, braking/driving torque of the vehicle), vehicle acceleration, and traveling resistance force, the force due to the stroke change is taken into consideration to obtain a highly accurate wheel speed that changes with the braking/driving torque. Can be estimated at.

1 is an overall configuration diagram showing a four-wheeled vehicle equipped with a vehicle motion state estimation device according to an embodiment of the present invention. It is a schematic diagram which shows the suspension apparatus provided between the vehicle body and a wheel. It is a control block diagram which materializes and shows the vehicle motion state estimation apparatus in FIG. It is a schematic diagram which shows the plane model of the four-wheeled vehicle of FIG. It is a vehicle model figure which shows the four-wheeled vehicle of FIG. 1 as a stereo model. It is a schematic diagram showing a wheel speed fluctuation caused by vehicle body pitching. It is a schematic diagram which shows the wheel speed fluctuation which arises with the displacement of a suspension. FIG. 6 is a characteristic diagram showing a non-linear relationship between vertical relative displacement and longitudinal displacement. It is a characteristic diagram which shows the relationship between a ground load and a tire effective turning radius. It is a schematic diagram which shows the wheel speed fluctuation which arises by ground load fluctuation. It is a schematic diagram which shows the side model of a four-wheeled vehicle. It is a schematic diagram showing a two-wheel plane model on the front wheel side of the vehicle. It is a characteristic diagram which shows the relationship between vehicle height, toe angle, and camber angle. FIG. 3 is a control block diagram for estimating and calculating a lateral force due to a vehicle height change in the vehicle motion state estimating device according to the embodiment. FIG. 3 is a control block diagram for estimating a wheel speed that changes according to braking/driving torque in the vehicle motion state estimation device according to the embodiment. It is a control block diagram of a comparative example which estimates a wheel speed which changes with braking/driving torque.

Hereinafter, the vehicle motion state estimating device according to the embodiment of the present invention will be described in detail with reference to FIGS. In addition, in order to avoid complication of the description, subscripts indicating left front (fl), right front (fr), left rear (rl), and right rear (rr) are attached to the reference numerals of the vehicle wheels. explain. When collectively referring to left front, right front, left rear, and right rear, the subscripts will be omitted from the reference numerals for explanation. Similarly, subscripts indicating front (f) and rear (r) are attached to the reference numerals for description. When collectively referring to front and rear, the subscripts will be omitted from the reference numerals for explanation.

In the figure, a vehicle body 1 constitutes a body of a vehicle (automobile). On the lower side of the vehicle body 1, there are provided a front left wheel 2fl, a front right wheel 2fr, a rear left wheel 2rl, and a rear right wheel 2rr (hereinafter collectively referred to as wheel 2). Each wheel 2 is configured to include a tire 3 as shown in the schematic diagram of FIG. 2, for example. The tire 3 acts, for example, as a spring that absorbs fine unevenness on the road surface. The vehicle body 1 of the vehicle and each wheel 2 are coupled to each other via, for example, a front wheel side suspension device 5 and a rear wheel side suspension device 8.

A front stabilizer 4F is provided between the left front wheel 2fl and the right front wheel 2fr, for example, as shown in FIG. 5, in order to suppress the roll of the vehicle body 1. Similarly, a rear stabilizer 4R is provided between the left rear wheel 2rl and the right rear wheel 2rr. The stabilizer 4 is a stabilizer mechanism provided in the vehicle. The stabilizer 4 is attached to the vehicle body 1 via a pair of attachment bushes and the like which are separated from each other on the left and right. The front stabilizer 4F generates a stabilizer reaction force due to torsional rigidity due to a roll or a difference in vertical movement between the left front wheel 2fl and the right front wheel 2fr. Similarly, the stabilizer 4R on the rear side generates a stabilizer reaction force due to torsional rigidity due to a roll or a vertical movement difference between the left rear wheel 2rl and the right rear wheel 2rr.

As shown in FIG. 2, the front wheel suspension device 5 is interposed between the vehicle body 1 and the wheels 2 (left front wheel 2fl, right front wheel 2fr). The suspension device 5 includes a spring 6 as a suspension spring, and a damping force adjusting type which is interposed between the vehicle body 1 and two wheels 2 (left front wheel 2fl, right front wheel 2fr) in parallel with the spring 6. A damping force variable damper (hereinafter referred to as damper 7) as a shock absorber. The suspension device 8 on the rear wheel side is interposed between the vehicle body 1 and the wheels 2 (left rear wheel 2rl, right rear wheel 2rr). The suspension device 8 includes a spring 9 as a suspension spring, and a damper 7 which is provided in parallel with the spring 9 between the vehicle body 1 and the wheel 2 (left rear wheel 2rl, right rear wheel 2rr). There is.

Here, the dampers 7 of the front and rear wheel side suspension devices 5 and 8 are configured using damping force adjusting hydraulic shock absorbers such as semi-active dampers. An actuator (not shown) including a damping force adjusting valve or the like is provided in these dampers 7 in order to adjust the characteristics (damping characteristics) of the generated damping force from hard characteristics (hard characteristics) to soft characteristics (soft characteristics). Is attached. The damping characteristics of each damper 7 are changed by the actuator being driven by an external command and the flow of the working fluid being variably controlled. Specifically, the damper 7 has its damping force characteristic (ie, damping characteristic) adjusted according to the relative speed between the vehicle body 1 and the wheel 2 and the target damping coefficient (corrected damping coefficient). That is, the controller (for example, the vehicle motion state estimating device 10 described later) outputs a command current according to the relative speed and the target damping coefficient. The damper 7 can generate a damping force that is variably adjusted according to a command current output from the controller.

The front and rear wheel suspension devices 5 and 8 may be configured to use air springs (not shown) of an air suspension, for example, instead of the springs 6 and 9 as suspension springs. In this case, the working fluid (compressed air) is supplied to or discharged from the air springs on the left front wheel 2fl, the right front wheel 2fr, the left rear wheel 2rl, and the right rear wheel 2rr, so that the wheels 2 and the vehicle body 1 You can adjust the vehicle height, which is the distance between.

A vehicle motion state estimating device 10 is mounted on a vehicle body 1 of the vehicle shown in FIG. This vehicle motion state estimation device 10 has its input side connected to a wheel speed sensor 11, an acceleration sensor 12, a gyro sensor 13, a steering angle sensor 14, a braking/driving control unit 15 and a steering control unit 16 on the side of each wheel 2 and outputs them. The braking/driving control unit 15 and the steering control unit 16 are connected to the side.

The wheel speed sensor 11, the acceleration sensor 12, the gyro sensor 13, and the steering angle sensor 14 are generally mounted on the vehicle. The four wheel speed sensors 11 individually measure and detect the rotation speeds of the wheels 2 (that is, the left front wheel 2fl, the right front wheel 2fr, the left rear wheel 2rl, and the right rear wheel 2rr) as the respective wheel speeds. The acceleration sensor 12 detects acceleration (for example, longitudinal acceleration Gx, lateral acceleration Gy) that acts on the center of gravity G (see FIGS. 4 and 5) of the vehicle body 1. The gyro sensor 13 detects a yaw rate which is a rotational angular velocity around the center of gravity G of the vehicle body 1. The steering angle sensor 14 is a sensor that detects the steering angle (rotation angle) of the steering wheel or the steering angle of the wheel 2 that is generated by the steering of the driver who drives the vehicle.

The braking/driving control unit 15 generates a driving force generated by a prime mover of the vehicle (for example, an internal combustion engine or an electric motor as an engine) and/or a braking device (based on the steering wheel operation of the driver or the output of the vehicle motion state estimation device 10). It is a control unit that controls the braking force generated by (not shown) or the like. The steering control unit 16 is a control unit that controls the steering angle of the wheels 2 (for example, the left front wheel 2fl and the right front wheel 2fr) based on the driver's steering wheel operation, the output of the vehicle motion state estimation device 10, and the like.

Here, to one or both of the braking/driving control unit 15 and the steering control unit 16, a signal detected by the above-described sensor is input, and a slip ratio, which is a wheel slip in the front-rear direction of the wheel 2, a lateral direction. A plane motion estimating unit that estimates and outputs a plane motion state quantity such as a side slip angle that is the wheel slip of the above may be provided. Further, the vehicle body 1 may include a host controller (not shown) that transmits a control command and an estimated value to the braking/driving control unit 15 and the steering control unit 16, and the host controller is a vehicle motion state. The vertical movement state quantity that is the output of the estimation device 10 may be input to generate a control command and an estimated value.

In the following description, the signal values detected by the above-described sensors (wheel speed sensor 11, acceleration sensor 12, gyro sensor 13, and steering angle sensor 14) and the braking/driving control unit 15 or steering control unit 16, or the same. The values estimated and output by both are described as running state information. Then, the vehicle motion state estimation device 10 estimates the vertical motion state amount of the vehicle body 1 such as the relative speed and the pitch rate by inputting the above-mentioned running state information, and outputs the result to the braking/driving control unit 15 and the like.

Next, a specific configuration of the vehicle motion state estimation device 10 will be described with reference to FIG. FIG. 3 is a conceptual diagram of a configuration of a vehicle motion state estimation device 10 that estimates and outputs vertical motion state quantities such as relative displacement and relative speed between the vehicle body 1 and the wheels 2 based on the running state information of the vehicle described above. Is shown as.

The vehicle motion state estimation device 10 includes a rotary motion estimation unit 21 that estimates a rotary motion state amount, a wheel speed fluctuation estimation unit 22 that estimates a wheel speed fluctuation caused by vertical motion, and a bounce motion estimation that estimates a bounce motion state amount. It is composed of a unit 23 and a correction value estimation unit 24 which estimates a correction value. As shown in FIG. 3, the vehicle motion state estimation device 10 collectively outputs the rotational motion state amount and the bounce motion state amount. In the following description, this output (rotational motion state quantity and bounce motion state quantity) will be referred to as vertical motion state quantity.

The rotational motion estimation unit 21 receives the traveling state information as an input, and based on the equation of motion, the filter, and the gain, the roll angle θx and the pitch angle θy that are the rotation angles around the center of gravity G of the vehicle body 1, and the roll rate that is the rotational angular velocity. And the pitch rate are estimated, and the rotational motion state quantity estimated value is output. Here, the rotational motion estimation unit 21 is not included in the vehicle motion state estimation device 10, but is mounted and estimated in another unit (for example, the braking/driving control unit 15 or the like) connected to the vehicle motion state estimation device 10. The rotational motion state quantity estimated value may be input to the vehicle motion state estimation device 10. Therefore, the method of acquiring the rotational motion state quantity estimated value in the vehicle motion state estimation device 10 is not limited to the configuration shown in FIG.

The wheel speed fluctuation estimation unit 22 inputs the traveling state information and the rotational motion state quantity estimated value and estimates the wheel speed fluctuation caused by the vertical movement caused by the vertical displacement of the road surface or the vertical movement of the vehicle. Then, the wheel speed fluctuation estimation unit 22 outputs the wheel speed fluctuation caused by the vertical motion thus estimated to the bounce motion estimation unit 23.

The bounce motion estimating unit 23 receives the traveling state information, the rotational motion state amount estimated value, the wheel speed variation due to the vertical movement, and a correction value described later as inputs, and the relative displacement between the vehicle body 1 and the wheel 2 is input. Estimate the amount of bounce motion such as the relative velocity. Then, the bounce motion estimating unit 23 outputs the bounce motion state quantity thus estimated. The correction value estimation unit 24 receives the running state information and the bounce motion state amount estimated value as inputs, estimates a correction value, and outputs this estimated value to the bounce motion estimation unit 23.

Next, the wheel speed fluctuation estimating unit 22, the bounce motion estimating unit 23, and the correction value estimating unit 24 will be described in more detail. First, a method of estimating the wheel speed fluctuation due to the vertical movement in the wheel speed fluctuation estimation unit 22 will be described with reference to FIG.

FIG. 4 is a diagram showing a plane model of a four-wheeled vehicle. The center of gravity G on the spring of the vehicle body 1 is the origin, the front-rear direction of the vehicle is the x-axis, the left-right direction of the vehicle is the y-axis, and the up-down direction of the vehicle is the z-axis. FIG. 4 shows the movement during turning by a four-wheeled vehicle with front-wheel steering.

As shown in FIGS. 4 and 5, the actual steering angle that is the steering angle of the wheel 2 is δ, the speed in the traveling direction of the vehicle is V, the speed in the front-rear direction of the vehicle is Vx, the speed in the left-right direction of the vehicle is Vy, The yaw rate, which is the rotational angular velocity around the z-axis detected by the gyro sensor 13, is r, the angle formed by the forward and backward directions of the vehicle is the vehicle body slip angle β, the wheels 2 (left front wheel 2fl, right front wheel 2fr, left rear wheel 2rl and The angles formed by the traveling direction of the right rear wheel 2rr) and the rotation surface are wheel side slip angles βfl, βfr, βrl, βrr, and the wheel speed Vws detected by the wheel speed sensor 11 is Vwsfl, Vwsfr, Vwsrl, Vwsrr, respectively. The distance between the front and rear wheel axles is L, the distance between the front and rear axles and the sprung center of gravity G in the vehicle longitudinal direction is Lf and Lr, and the treads of the front and rear wheels are df and dr. The suffix "f" is the front wheel, "r" is the rear wheel, "fl" is the left front wheel, "fr" is the right front wheel, "rl" is the left rear wheel, and "rr" is the right rear wheel. There is. The subscript “z” is a notation associated with the vertical z-axis, and “Vz” represents the wheel speed fluctuation due to the vertical movement of each wheel 2.

The wheel speed fluctuations Vzfl, Vzfr, Vzrl, Vzrr due to the vertical movement estimated and calculated by the wheel speed fluctuation estimation unit 22 are obtained by the following formula 1. Here, the wheel speed fluctuations Vzfl, Vzfr, Vzrl, and Vzrr due to the vertical movement in the equation 1 are wheel speeds Vwxfl, Vwxfr, Vwxrl, and Vwxrr converted to the sprung center of gravity position, and the center of gravity of the vehicle body 1 detected by the acceleration sensor 12. It is calculated based on the longitudinal acceleration Gx acting on G, the lateral acceleration Gy, the gravitational acceleration g, the roll angle θx and the pitch angle θy estimated by the rotational motion estimating unit 21, and the like.

The vehicle speed Vx in the front-rear direction of the equation 1 is calculated by time-differentiating the plane motion state amount estimated by the controller such as the braking/driving control unit 15 described above and the position information detected using GPS. It may be a value or a plane motion state quantity estimated by the plane motion estimation unit provided in the vehicle motion state estimation device 10 (not shown). Therefore, the method of acquiring the vehicle speed Vx in the front-rear direction is not limited to the above-described configuration.

Further, the wheel side slip angles βfl, βfr, βrl, and βrr of the equation 1 are calculated based on the plane motion state amount estimated by the controller such as the braking/driving control unit 15 or the vehicle body side slip angle β detected using GPS. It may be a value obtained by the above, or a plane motion state quantity estimated by the plane motion estimation unit provided in the vehicle motion state estimation device 10 (not shown). Therefore, the method of acquiring the wheel side slip angles βfl, βfr, βrl, and βrr is not limited to the above-described configuration.

Further, the roll angle θx and the pitch angle θy in the equation 1 may be values estimated by the controller such as the braking/driving control unit 15 described above, or values detected by using a stereo camera or the like. Therefore, the method of acquiring the roll angle θx and the pitch angle θy is not limited to the above-described configuration.

From the above, the wheel speed fluctuation estimating unit 22 determines the wheel speeds Vwsfl, Vwsfr, Vwsrl, Vwsrr detected by the wheel speed sensor 11 which is the traveling state information, and the yaw rate r which is the rotational angular speed around the z-axis detected by the gyro sensor 13. Etc. are input to estimate and calculate wheel speed fluctuations Vzfl, Vzfr, Vzrl, Vzrr due to vertical movement. Then, the wheel speed fluctuation estimating unit 22 outputs the wheel speed fluctuations Vzfl, Vzfr, Vzrl, Vzrr due to the vertical motion estimated by the equation 1 to the bounce motion estimating unit 23.

Next, a method for estimating the bounce motion state quantity in the bounce motion estimating unit 23 and a method for estimating the correction value in the correction value estimating unit 24 will be described with reference to specific examples shown in FIGS.

In the bounce motion estimation unit 23, the detected or estimated observed amount is set as an output vector y, the bounce motion state amount is set as a state vector x, the vehicle motion is made into a state equation, and an observer based on the state equation inputs the output vector y and the input vector y. The state vector x is estimated from the vector u and output. Therefore, it is necessary to derive the equation of state represented by the following equation (2).

Therefore, the derivation of the state equation of Equation 2 will be described below.
FIG. 5 is a diagram showing a full-vehicle model of a four-wheeled vehicle, showing the motion of the four-wheeled vehicle with vertical displacement of the road surface. Here, the sprung masses on the vehicle body 1 side are mbf and mbr, and the unsprung masses on the wheel 2 side are mwf and mwr. The vertical displacement on the spring of each wheel 2 (left front wheel 2fl, right front wheel 2fr, left rear wheel 2rl and right rear wheel 2rr) is Z2fl, Z2fr, Z2rl, Z2rr, and the unsprung vertical displacement is Z1fl, Z1fr, Let Z1rl and Z1rr, and the vertical displacement of the road surface be Z0fl, Z0fr, Z0rl and Z0rr. Further, the roll angle θx and the pitch angle θy of the center of gravity G on the spring are set, the suspension spring constants of the springs 6 and 9 are set to Ksf and Ksr, the suspension damping coefficients of the damper 7 are set to Csfl, Csfr, Csrl, and Csrr, and the stabilizer 4F, The spring constants of 4R are Kstf and Kstr.

The vertical movement of the vehicle that accompanies the vertical displacement of the road is obtained by the following equations (3) to (7). Formula 3 is a motion equation relating to a vertical force acting on the spring on the vehicle body 1 side, and Formula 4 is a motion equation relating to a vertical force acting on the wheel 2 side unsprung force. Equation 5 is an equation of motion relating to a vertical force acting between the sprung part and the unsprung part. Formula 6 is used to obtain relative displacements Z21fl, Z21fr, Z21rl, Z21rr in the vertical direction between the sprung and unsprung parts for each wheel 2 (left front wheel 2fl, right front wheel 2fr, left rear wheel 2rl and right rear wheel 2rr). It is an arithmetic expression. Expression 7 is a relational expression between the roll angle θx that is the rotation angle around the x axis and the pitch angle θy that is the rotation angle around the y axis.

Next, the wheel speed fluctuation estimation unit 22 estimates the wheel speed fluctuation Vz due to vehicle body pitching, which constitutes the output wheel speed fluctuation Vz due to vertical movement, the wheel speed fluctuation Vzb due to suspension displacement, and the ground contact. The wheel speed fluctuation Vzc due to the load fluctuation and the wheel speed fluctuation Vzd due to the braking/driving torque will be described with reference to, for example, FIGS. 6 to 11. Since the wheels 2 shown in FIGS. 6, 7, 10, and 11 are common to all the wheels, for example, the subscripts of the left front wheel 2fl, the right front wheel 2fr, the left rear wheel 2rl, and the right rear wheel 2rr are omitted. , Wheels 2 as a whole. The body 1 side has an unsprung mass mb, and the wheel 2 side has an unsprung mass mw.

First, a specific example of the wheel speed fluctuation Vza due to vehicle body pitching will be described. FIG. 6 is a diagram showing wheel speed fluctuations caused by vehicle body pitching, and schematically shows how wheel speed fluctuations Vza occur due to the relative angular velocities of the vehicle body 1 and the wheels 2 (tires 3) that occur during traveling on a swell road or the like. It is a representation. The wheel speed fluctuation Vza caused by the vehicle body pitching is obtained by the following formula 8 using the pitch rate (dθy/dt), which is the time derivative of the pitch angle θy, where the height of the sprung center of gravity G is h.

Next, the wheel speed fluctuation Vzb due to suspension displacement will be described. FIG. 7 is a diagram showing wheel speed fluctuations caused by displacement of the suspension. The vehicle 2 and the wheels 2 (tires 3) are subjected to relative displacement Z21 in the vertical direction, which occurs during traveling on a swell road or the like. 3A schematically shows how the center Ow of 3) is displaced around the instantaneous rotation center Os of the suspension to cause a longitudinal displacement Xzb in the wheel 2 (tire 3).

A characteristic line 31 indicated by a dotted line in FIG. 8 is a characteristic diagram showing the relationship between the vertical displacement Z21 of the vehicle body 1 and the wheel 2 (tire 3) in FIG. 6 and the longitudinal displacement Xzb of the wheel 2 (tire 3). Is. Here, FIG. 8 is a characteristic diagram with the origin when the vehicle (body 1) is stationary on a horizontal plane, and the angle σ shown in FIG. 8 is a linear approximate gradient at the origin of the characteristic line 31. The wheel speed fluctuation Vzb1 due to the suspension displacement, which is a time derivative of the longitudinal displacement Xzb of the wheel 2 (tire 3), is expressed by the following formula 9 as follows: relative displacement Z21 between the vehicle body 1 and the wheel 2 (tire 3) in the vertical direction. The relative speed, which is the time derivative of, is calculated as (dZ21/dt). Since the equation 9 uses the above-described linear approximation gradient σ, Vzb and Vzb1 are equal to each other in a linearly approximated range.

On the other hand, in the region where the longitudinal displacement Xzb of the wheel 2 (tire 3) and the relative vertical displacement Z21 of the vehicle body 1 and the wheel 2 (tire 3) shown in FIG. is there. Therefore, in the present invention, the correction value estimation unit 24 receives the bounce motion state quantity estimation value as an input, estimates and outputs a correction value based on this non-linear characteristic, and inputs the correction value to the bounce motion estimation unit 23 to solve the above-mentioned problems. Resolve.

Next, a specific example of the method of estimating the correction value in the correction value estimation unit 24 will be described. As an example, the characteristic line 31 (forward-backward displacement Xzb) shown in FIG. 8 can be approximated by a quadratic function represented by the following formula 10. Where α1 is a quadratic coefficient of vertical relative displacement Z21, α2 is a linear coefficient of relative displacement Z21, α3 is an intercept, and Z21o is a relative displacement when the vehicle (body 1) is stationary on a horizontal plane. Is. In the present embodiment, the approximation is performed by the quadratic function, but the approximation may be performed by a function of third order or higher, and the approximation method of the characteristic diagram is not limited.

Since the object of correction is the speed term, the wheel speed fluctuation Vzb2 due to suspension displacement obtained by differentiating the equation 10 with respect to time is obtained by the following equation 11.

Based on the above equations 9 and 11, the change amounts Vzbdfl, Vzbdfr, Vzbdrl, Vzbdrr of the wheel speed fluctuation due to the suspension displacement estimated by the correction value estimation unit 24 are obtained by the following equation 12.

Equation 12 is an equation assuming that the relationship between the relative displacement Z21 and the longitudinal displacement Xzb is non-linear both in the front and rear suspensions. For example, when the front wheel side has a linear characteristic and the rear wheel side has a non-linear characteristic, Vzbdfl and Vzbdfr can be made to correspond to both the linear characteristic and the non-linear characteristic by setting the respective values to zero (0). The non-linear component of the wheel speed fluctuation due to the suspension displacement of the formula 12 may be calculated using a characteristic diagram or the like, and the calculation method of the non-linear component of the wheel speed fluctuation due to the suspension displacement is not limited. Absent.

Further, the linear approximation gradient σ used in Expression 12 is set to σ=0, and the correction value estimating unit 24 estimates and outputs the wheel speed variation Vzb due to suspension displacement, and inputs it to the bounce motion estimating unit 23. May be Further, the relative displacements Z21ofl, Z21ofr, Z21orl, and Z21orr when the vehicle of Formula 12 (the vehicle body 1) is stationary on the horizontal plane change depending on the increase/decrease in the number of passengers and the increase/decrease in mass accompanying the loading of luggage.

Therefore, in order to realize highly accurate estimation of the bounce motion state quantity, relative displacement when the vehicle (body 1) is stationary on a horizontal plane is detected from detection signals of the external environment recognition sensor such as a stereo camera or the acceleration sensor 12. It is desirable to estimate Z21ofl, Z21ofr, Z21orl, Z21orr.

In addition, the relative displacements Z21ofl, Z21ofr, Z21orl, and Z21orr when the vehicle of Formula 12 (the vehicle body 1) is stationary on the horizontal plane are set to zero (0), and the estimation of the bounce motion state quantity with high robustness is performed. In order to realize the calculation, the second-order coefficient α1 of the relative displacement Z21 in the vertical direction, the first-order coefficient α2 of the relative displacement Z21, the intercept α3, and the linear approximation gradient σ under the condition of the most frequently used mass or the like. Is preferred.

Further, the formula 12 is the relative displacement Z21ofl, Z21ofr, Z21orl, Z21orr when the vehicle (body 1) is stationary on the horizontal plane, and the relative displacement Z21fl, Z21fr of the vehicle 1 and the wheel 2 (tire 3) in the vertical direction. , Z21rl, Z21rr, and time derivative of relative displacement of the vehicle body 1 and the wheel 2 (tire 3) in the vertical direction (dZ21fl/dt), (dZ21fr/dt), (dZ21rl/dt), (dZ21rr/dt). Is a map that outputs relative displacements Z21ofl, Z21ofr, Z21orl, Z21orr when the vehicle (body 1) is stationary on a horizontal plane, and changes Vzbdfl, Vzbdfr, Vzbdrl, Vzbdrr of wheel speed fluctuations due to suspension displacement. However, the method for estimating the variations Vzbdfl, Vzbdfr, Vzbdrl, and Vzbdrr of wheel speed fluctuations due to suspension displacement is not limited to the above.

Next, the wheel speed fluctuation Vzc due to the ground load fluctuation will be described with reference to FIGS. 9 and 10. FIG. 10 is a diagram showing wheel speed fluctuations caused by ground load fluctuations. The tire effective rotation radius R decreases as the ground load fluctuation Fzd acting on the wheels 2 (tires 3) increases, and as a result, the wheel speeds are reduced. It is a schematic representation of how the variation Vzc increases. A characteristic line 32 shown in FIG. 9 represents the relationship between the ground contact load Fz and the tire effective rotation radius R.

The wheel speed fluctuation Vzc due to the ground load fluctuation is η as a linear approximation gradient of the characteristic line 32 shown in FIG. 9, Rd is the amount of change in the tire effective rotation radius R, Kt is the tire vertical spring constant, Vwx is the wheel speed, and spring is the spring. The lower vertical displacement is Z1 and the road vertical displacement is Z0. Here, the method of deriving the variation amount Rd of the tire effective radius of rotation R using the linear approximation gradient η of the equation 13 is one example, and the characteristic diagram shown in FIG. 9 and the approximation formula of the characteristic diagram are used. However, the method of deriving the variation amount of the tire effective rotation radius R is not limited to the above method.

Next, the wheel speed variation Vzd due to the torque ground load variation will be described. FIG. 11 shows a vehicle model of the vehicle viewed from the side. Although only two wheels located on the left side of the vehicle are shown in FIG. 11, for example, four wheels are actually taken into consideration. Braking/driving torques Tfl, Tfr, Trl, and Trr are applied to the respective wheels 2 (left front wheel 2fl, right front wheel 2fr, left rear wheel 2rl, right rear wheel 2rr).

Here, the longitudinal velocity Vb of the vehicle body 1 and the longitudinal velocities Vfl, Vfr, Vrl, Vrr of the wheels 2 (left front wheel 2fl, right front wheel 2fr, left rear wheel 2rl, right rear wheel 2rr) are calculated from the wheel coordinate system. The longitudinal force Fxfl, Fxfr, Fxrl, Fxrr for each wheel 2 and the lateral forces Fsfl, Fsfr, Fsrl, Fsrr caused by the stroke change of the wheel 2 similarly determined from the wheel coordinate system are determined by the vehicle geometry and the tire characteristics. ..

Toe angles αfl, αfr, αrl, αrr of wheels 2 (left front wheel 2fl, right front wheel 2fr, left rear wheel 2rl, right rear wheel 2rr), mass mb of vehicle body 1, and mass mfl, mfr, mrl of each wheel 2. , Mrr and the inertia moments Ifl, Ifr, Irl, Irr of the front and rear wheels are mt=mb+mfl+mfr+mrl+mrr, where the total mass mt of the vehicle is expressed by the following equation 14 ˜Equation 18 can be obtained.

Here, the air resistance force Fa is obtained from the following equation 19 using the air density ρ, the front projected area A of the vehicle, and the air resistance coefficient Cd. The gradient resistance force Fθ is calculated by the following equation 20 as the total mass mtotal (ie, mt) of the vehicle, the road surface gradient θ, the gravitational acceleration g, and the front and rear road surface vertical inputs Z0f and Z0r.

FIG. 12 is a view of the front wheels (left front wheel 2fl, right front wheel 2fr) of the vehicle as viewed from above. The left front wheel 2fl has a toe angle of αfl. At this time, a lateral force due to the toe angle and a lateral force due to the camber angle are generated, and the resultant force is defined as Fsfl. Further, the toe angle of the right front wheel 2fr is the angle αfr. At this time, a lateral force due to the toe angle and a lateral force due to the camber angle are generated, and the resultant force between them is sfr. There is a relationship between the stroke (that is, the vehicle height) of the damper 7 and the toe angle and the camber angle as shown by characteristic lines 33 and 34 shown in FIG. It is known that when the changes in the toe angle and the camber angle are small, the lateral force generated in the tire is proportional to the respective angles. Therefore, the lateral force Fs due to the vehicle height change is obtained by performing the calculation shown in FIG. be able to.

Here, the first map calculation unit 35 shown in FIG. 14 has a function of performing map calculation of the toe angle with respect to the vehicle height, and when the vehicle height signal is input, the toe angle at this time is a signal of the calculation result. (That is, a calculation signal). The second map calculation unit 36 has a function of performing map calculation of the camber angle with respect to the vehicle height, and when the vehicle height signal is input, the camber angle at this time is output as a signal of the calculation result (that is, calculation signal). To do. The first gain calculation unit 37 integrates the gain with respect to the toe angle calculation signal output from the first map calculation unit 35, and outputs a lateral force signal due to a change in the toe angle. The second gain calculation unit 38 integrates the gain with respect to the calculation signal of the camber angle output from the second map calculation unit 36, and outputs a lateral force signal due to the change of the camber angle.

Next, the adder 39 adds the lateral force signal output from the first gain calculation unit 37 and the lateral force signal output from the second gain calculation unit 38, and outputs the added signal to the vehicle. Output as lateral force Fs due to high change. The first and second map calculators 35 and 36, the first and second gain calculators 37 and 38, and the adder 39 shown in FIG. 14 are, for example, a part of the vehicle motion state estimating device 10 shown in FIG. I am configuring. In addition, although the above equation (18) is intended for the straight traveling state of the vehicle, the calculation may be performed in consideration of the turning angle due to the vehicle steering.

Next, when the slip of the wheel 2 (left front wheel 2fl, right front wheel 2fr, left rear wheel 2rl, right rear wheel 2rr) is considered, the respective slip ratios λfl, λfr, λrl, λrr are expressed by the following formulas 21-24. It is calculated by the formula.

From the above, the wheel speed fluctuations Vzdfl, Vzdfr, Vzdrl, Vzdrr due to the braking/driving torque can be obtained by the following equations 25 to 28.

ただし、係数Ａfl，Ａfr，Ａrl，Ａrrは、下記の数２９〜３２式により求められる。

However, the coefficients Afl, Afr, Arl, and Arr are obtained by the following equations 29 to 32.

The wheel speed fluctuations Vzfl, Vzfr, Vzrl, and Vzrr due to the vertical movement can be obtained by the following Expressions 35 to 38 using the wheel speed fluctuations represented by the above Expressions 8 to 28.

Here, the wheel speeds Vzfl, Vzfr, Vzrl, and Vzrr change from moment to moment. Therefore, when the bounce motion estimator 23 is a linear observer composed of time-invariant constants, which will be described later, it is necessary to consider variations in the wheel speeds. There is.

The wheel speed fluctuations Vzcfl, Vzcfr, Vzcrl, and Vzcrr due to the ground load fluctuations in the equations 35 to 38 are calculated as the term of the wheel speed fluctuations due to the ground load fluctuations due to the steady wheel speed Vws and the wheel speed fluctuations due to the ground load fluctuations. The items separated by the variations Vzcdfl, Vzcdfr, Vzcdrl, and Vzcdrr are expressed by the following equations 39 to 42.

That is, the correction value estimation unit 24 receives the bounce motion state quantity estimation values such as the relative displacement Z21 and the relative speed dZ21/dt as input, and based on the formula 12 and the formulas 39 to 42, the wheel speed caused by the suspension displacement is calculated. The variations Vzbdfl, Vzbdfr, Vzbdrl, Vzbdrr and the variations Vzcdfl, Vzcdfr, Vzcdrl, Vzcdrr of the wheel speed variation due to the ground load variation shown in equations 39 to 42 are estimated and output.

The state equation shown in the above equation 2 is obtained by the following equation 43. This makes it possible to estimate the state vector x, which is the bounce motion state quantity such as the relative displacement Z21 and the relative velocity (dZ21/dt), by the linear observer using the state matrix A and the input matrix B as time-invariant constants. The details of the state matrix A and the input matrix B are omitted.

The above is the method for estimating the vertical motion state quantity of the vehicle in the present invention, and by using the vehicle motion state estimation device 10 having such a configuration, even a vehicle having a non-linear suspension characteristic, such as a wheel speed sensor, The vertical motion state quantity can be estimated by using a vehicle-mounted sensor and a vehicle dynamics model.

On the other hand, in the comparative example shown in FIG. 16 (for example, the prior art of Patent Document 1), the wheel speed calculation unit 47 outputs the wheel speed that changes depending on the braking/driving torque to the output unit 48 as the result of the estimation calculation. , Braking/driving torque of the vehicle (that is, the first input information unit 42), vehicle acceleration (that is, the second input information unit 43), and running resistance (that is, the third input information unit 44) The estimation calculation was performed in consideration of the input information of. The third input information unit 44 uses, as input information, traveling resistance force including air resistance force, rolling resistance force, and gradient resistance force, for example. However, in the comparative example shown in FIG. 16, since the longitudinal force applied to the vehicle body due to the stroke change of the suspension is not taken into consideration, the actual wheel speed of each wheel of the vehicle cannot be estimated with high accuracy.

Therefore, in the present embodiment, the wheel speed calculation unit 40 shown in FIG. 15 outputs the result of the estimation calculation (that is, the wheel speed that changes depending on the braking/driving torque) to the output unit 41. , In addition to the third input information units 42, 43 and 44, the input information from the fourth input information unit 45 is considered. That is, the first input information unit 42 outputs the braking/driving torque of the vehicle to the wheel speed calculation unit 40 as a parameter for the estimation calculation, and the second input information unit 43 uses the vehicle acceleration as a parameter for the estimation calculation. It is output to the calculation unit 40.

In addition, the third input information unit 44 outputs the traveling resistance force (for example, air resistance force, rolling resistance force, gradient resistance force) to the wheel speed calculation unit 40 as a parameter of the estimation calculation, and the fourth input information unit 44. 45 outputs the stroke change of the damper 7 (that is, the suspension) to the stroke-induced longitudinal force calculation unit 46 as a parameter for the estimation calculation. Then, the stroke-induced longitudinal force calculation unit 46 outputs the longitudinal forces Fxfl, Fxfr, Fxrl, and Fxrr for each wheel 2 as viewed from the wheel coordinate system to the wheel speed calculation unit 40 as parameters for the estimation calculation.

As described above, in the present embodiment, the braking/driving torques Tfl, Tfr, Trl, Trr of the vehicle, the vehicle acceleration, the running resistance of the vehicle, and the vehicle running resistance and The suspension stroke change is used, and the suspension stroke change is determined in consideration of the stroke-induced longitudinal forces Fxfl, Fxfr, Fxrl, and Fxrr. Thus, in addition to the front and rear wheel torques (that is, the braking/driving torque of the vehicle), the vehicle acceleration, and the running resistance force, the wheel speed that changes with the braking/driving torque is estimated with high accuracy by considering the force due to the stroke change. be able to.

Next, as the vehicle motion state estimation device included in the above-described embodiment, for example, the following modes are conceivable.

As a first aspect, there is provided a vehicle motion state estimating device for a vehicle in which wheels and a vehicle body are connected via a suspension, wherein a wheel speed detection value by a wheel speed sensor and a wheel speed change caused by the vertical movement of the vehicle. And the actual wheel speed of the wheel is estimated from the above, and the wheel speed change caused by the vertical movement of the vehicle includes braking/driving torque of the vehicle, vehicle acceleration, running resistance of the vehicle, and suspension of the vehicle. It is characterized in that it is obtained by an estimation calculation using the stroke change as a parameter, and that the stroke change of the suspension is obtained in consideration of the longitudinal force due to the stroke.

1 vehicle body 2 wheels 3 tires 5,8 suspension device 6,9 springs (suspension springs)
7 damper (damping force adjustment type shock absorber)
10 Vehicle Motion State Estimation Device 11 Wheel Speed Sensor 12 Acceleration Sensor 13 Gyro Sensor 14 Steering Angle Sensor 15 Braking/Drive Control Unit 16 Steering Control Unit 21 Rotational Motion Estimator 22 Wheel Speed Fluctuation Estimator 23 Bounce Motion Estimator 24 Corrected Value Estimator 40 Wheel speed calculation unit 41 Output unit (Wheel speed that changes depending on braking/driving torque)
42 First Input Information Section (Vehicle Braking/Driving Torque)
43 Second input information section (vehicle acceleration)
44 Third input information section (running resistance)
45 4th input information section (stroke change of suspension)
46 Stroke-induced longitudinal force calculation unit

Claims (1)

A vehicle motion state estimating device in a vehicle in which wheels and a vehicle body are coupled via a suspension,
A configuration for estimating the actual wheel speed of the wheel from the wheel speed detection value by the wheel speed sensor and the wheel speed change caused by the vertical movement of the vehicle,
The wheel speed change caused by the vertical movement of the vehicle is obtained by an estimation calculation using the braking/driving torque of the vehicle, the vehicle acceleration, the running resistance of the vehicle, and the stroke change of the suspension as parameters.
Further, the vehicle motion state estimating device is characterized in that the stroke change of the suspension is obtained in consideration of the longitudinal force caused by the stroke.

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