JP2010162911A - Motion control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology and device for reducing any sense of discomfort and improving safety performance by automatically performing acceleration/deceleration interlocked with a handle operation to be operated from a daily driving region, and by reliably reducing sideslip in a marginal driving region. <P>SOLUTION: On the basis of a yaw moment control command calculated from sideslip information of a vehicle, vehicle longitudinal acceleration/deceleration, to be achieved in a mode in which different braking/driving forces are generated in right/left wheels among four wheels, is corrected so that almost equal braking/driving forces are added to the right/left wheels among the four wheels by reducing the difference from an acceleration/deceleration control command interlocked with lateral motion. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle motion control apparatus.

  The following equation is known as a command value for automatically performing acceleration / deceleration linked to the steering wheel operation (see, for example, Non-Patent Document 1).

  Basically, this is a simple control law in which the lateral jerk Gy is multiplied by the gain Cxy and a value obtained by adding a first-order delay is used as a longitudinal acceleration / deceleration command. As a result, it has been confirmed that a part of the linkage control strategy for the lateral and longitudinal movement of the expert driver can be simulated (see, for example, Non-Patent Document 2). Gx_DC in this equation is a deceleration component not linked to the lateral motion. This term is required when there is a foreseeable deceleration when there is a corner ahead or when there is a section speed command. The sgn (signum) term is a term provided so that the above operation can be obtained for both the right corner and the left corner. Specifically, the vehicle decelerates when turning in at the start of steering, and can stop when decelerating (because the lateral jerk becomes zero), and can perform an operation of accelerating when exiting the corner at the start of steering return.

  When controlled in this way, the combined acceleration of longitudinal acceleration and lateral acceleration (denoted as G) is a diagram in which the horizontal axis represents the longitudinal acceleration of the vehicle and the vertical axis represents the lateral acceleration of the vehicle. Since it is directed to make a transition (Vectoring), it is called “G-Vectoring control”.

  In addition, the skid prevention device for improving the safety performance in the marginal driving region is the origin of the same sign of β and β_dot (first and third quadrants) on the phase plane of the vehicle skid angle β and the vehicle skid angular velocity (β_dot). Since it is unstable (divergence direction) when the vehicle behavior transitions to a region away from the vehicle, it is reported that it is effective when used for the determination for starting the skid prevention device (for example, non-patent document) 3). It is disclosed that the vehicle is stabilized by applying different brake hydraulic pressures to the left and right wheels based on the side slip information, generating different left and right deceleration forces, and generating a yaw moment in a direction in which the side slip angle is reduced. Yes.

M. Yamakado, M. Abe: Improvement of Vehicle Agility and Stability by G-Vectoring Control, Proc. Of AVEC2008-080420 M. Yamakado, M. Abe: Proposal of the longitudinal driver model in coordination with vehicle lateral motion based upon jerk information, Review of Automotive Engineering, Vol. 29, No. 4, October 2008, P.533-541 S. Inagaki, I. Kushiro, M. Yamamoto: Analysis on Vehicle Stability in Critical Cornering Using Phase-Plane Method, Proc. Of AVEC1994- 9438411

  In Non-Patent Document 1 and Non-Patent Document 2, this control method is extracted from the brake and accelerator operations corresponding to the steering operation that is optionally performed by the expert driver. The simulation results show that there are few possibilities and that the mechanical rationality, maneuverability and stability of this control method are improved. This means that the acceleration / deceleration is controlled so that the behavior of the vehicle appropriately responds to the driver's steering operation, and as a result, it is possible to prevent the side slip angle of the vehicle from increasing. In particular, it is effective in reducing the so-called “understeer” in which the turning radius becomes too large for steering.

  On the other hand, this control does not compensate for reliably reducing the skid angle when the skid angle increases for some reason. For example, when the lateral movement of the vehicle is stabilized in the drift state in which the side slip angle is increased, the lateral acceleration becomes constant and the lateral jerk becomes zero. As a result, the acceleration / deceleration control command expressed by Equation 1 becomes zero, and the vehicle is in a stable state while drifting. Although it is stable mechanically, there is no guarantee that all drivers will be able to drive comfortably.

  Moreover, although the skid prevention apparatus described in the nonpatent literature 3 is operated based on the skid information, no skid is generated or a guideline for operation from a small daily area is not shown. Furthermore, from the viewpoint of preventing “understeer”, which “G-Vectoring control” is good at, “side skid prevention device” means that a moment is applied only after a large amount of skidding has occurred. For this reason, control tends to be performed later, and a large moment is required to reduce understeer. As a result, the understeer reducing effect is reduced, and there is a concern that an uncomfortable feeling may be caused by unnecessarily slowing down.

  Also, no consideration is given to the deceleration that occurs when the skid prevention device generates a yaw moment, the moment to be generated is first determined, and the acceleration / deceleration of the vehicle is determined by the resultant force of the left and right braking force. End up. This cannot be said to be acceleration / deceleration linked with lateral movement.

  The present invention has been made to solve such problems, and automatically performs acceleration / deceleration linked to the steering operation operated from the daily operation area, thereby reliably reducing the side slip in the limit operation area. An object of the present invention is to provide a vehicle motion control device that can improve safety performance with less discomfort.

  One aspect of the present invention is a vehicle motion control apparatus capable of independently controlling the driving force and braking force of four wheels, and based on an acceleration / deceleration control command linked to the lateral motion of the vehicle, A first mode for generating substantially the same braking / driving force, and a second mode for generating different braking / driving forces for the left and right wheels of the four wheels based on the yaw moment control command calculated from the side slip information of the vehicle. The vehicle motion control device selects the first mode when the yaw moment command is smaller than a predetermined value and selects the second mode when the yaw moment command is larger than the predetermined value. .

  ADVANTAGE OF THE INVENTION According to this invention, the motion control apparatus of the vehicle which has little discomfort and can improve safety performance can be provided.

The figure which shows the whole structure of a vehicle. The figure which shows vehicle lateral acceleration and jerk estimation using a vehicle model. The figure which shows vehicle lateral acceleration and jerk estimation using an acceleration sensor. The figure which shows the concept of the mutual complement by an estimated signal and a measurement signal. The figure which shows the mode from the left corner approach of the G-Vectoring control vehicle to escape. The figure which shows the time series data at the time of driving | running | working like FIG. The figure which shows the negative yawing moment addition by right-and-left differential braking and driving force. The figure which shows positive yawing moment addition by right-and-left differential braking and driving force. The figure which shows the mode from the left corner approach of the side slip prevention control vehicle to escape. The figure which shows the time series data at the time of driving | running | working like FIG. The figure which shows the fusion logic of G-Vectoring control and skid prevention control. The figure which shows the force and acceleration which are applied to the vehicle 0, and yawing motion. The figure which shows the yaw moment resulting from the load movement of G-Vectoring control. The figure which shows the intervention conditions of skid prevention control. The figure which shows the time series data at the time of the fusion control of G-Vectoring and skid prevention. The figure which shows the time series data at the time of the fusion control of G-Vectoring and skid prevention (small moment command). The figure which shows the control effect which appears in a "gg" diagram.

  Embodiments of the present invention will be described below. The present embodiment relates to a technique and an apparatus for automatically performing acceleration / deceleration linked with a steering operation operated from a daily operation area and improving safety performance in a limit operation area.

  In this embodiment, a technology and an apparatus that automatically improve acceleration / deceleration linked to a steering operation that operates from a daily operation area and reliably reduce skid in a limit operation area, and that can improve safety performance. The purpose is to provide.

  For this purpose, it is necessary to fuse and decouple the “G-Vectoring control” that works from the daily field and the “side skid prevention device” that works in the limit field.

  Considering vehicle motion as motion on a plane, Back-and-forth motion; Lateral motion and rotation around the center of gravity, ie C.I. Can be described by yawing movement.

  “G-Vectoring control” that realizes acceleration / deceleration linked to lateral motion is It controls acceleration / deceleration in the front-rear direction. It does not control the yawing moment. In other words, the yawing moment is “arbitrary” and has a degree of freedom.

  In addition, the “skid prevention device” is a direct C.I. Controls the yaw moment. It does not control longitudinal acceleration / deceleration. That is, the longitudinal acceleration / deceleration is “arbitrary” and has a degree of freedom.

  Therefore, in order to realize the fusion of these controls, the A.D. The longitudinal acceleration is controlled, and the C.I. The yawing moment may be controlled.

Specifically, the apparatus is configured to have the following two modes.
1) In a normal region where skidding is not significant, substantially the same braking / driving force is generated on the left and right wheels based on the “G-Vectoring control” command (first mode).
2) The skid increases and the braking / driving force different from the left and right is generated by the yaw moment command determined by the “slip prevention control” (second mode).

  If the longitudinal acceleration generated by the braking / driving force of the four wheels is different from the longitudinal acceleration command determined by the “G-Vectoring control” in the second mode, for example, the difference What is necessary is just to calculate the braking / driving force to be applied to the vehicle in order to generate the acceleration, and add the equally distributed values to the left and right wheels. As a result, the commanded acceleration / deceleration can be realized while maintaining the commanded yawing moment (the fusion of the two controls and the non-interference).

  Further, for example, in the case of two-wheel drive, or when the yaw moment is controlled only by brake control, a desired driving force may not be generated. In this case, “side skid prevention control” is given priority, and a moment is surely generated to ensure safety.

  As a result, the technology and equipment that automatically improve acceleration and deceleration linked to the steering operation that has merit in the normal operation area, and reliably reduce the skid in the limit operation area, and improve safety performance. realizable.

  FIG. 1 shows the overall configuration of the first embodiment of the present invention.

  In this embodiment, the vehicle 0 is configured by a so-called by-wire system, and there is no mechanical coupling between the driver and the steering mechanism, the acceleration mechanism, and the deceleration mechanism.

<Drive>
The vehicle 0 drives a left rear wheel 63 and a right rear wheel 64 by a motor 1, and also drives a left front wheel 61 by a left front wheel motor 121 and a right front wheel 62 by a right front wheel motor 122 (All Wheel Drive: AWD car). A driving force distribution mechanism 2 connected to the motor 1 and capable of freely distributing the motor torque to the left and right wheels is mounted. Here, there is no particular difference between power sources such as an electric motor and an internal combustion engine. As a most preferred example showing the present embodiment, the driving force and braking force of the four wheels can be freely controlled by combining with the four-wheel independent brake shown later. The configuration will be described in detail below.

  The left front wheel 61, the right front wheel 62, the left rear wheel 63, and the right rear wheel 64 are each equipped with a brake rotor, a wheel speed detection rotor, and a wheel speed pickup on the vehicle side so that the wheel speed of each wheel can be detected. It has become. Then, the depression amount of the accelerator pedal 10 of the driver is detected by the accelerator position sensor 31 and is processed by the central controller 40 via the pedal controller 48. This calculation process includes torque distribution information corresponding to the “slip prevention control” as an object of the present embodiment. The power train controller 46 controls the outputs of the motor 1, the left front wheel motor 121, and the right front wheel motor 122 according to this amount. The output of the motor 1 is distributed to the left rear wheel 63 and the right rear wheel 64 at an optimum ratio via the driving force distribution mechanism 2 controlled by the power train controller 46.

  An accelerator reaction force motor 51 is also connected to the accelerator pedal 10, and the reaction force is controlled by the pedal controller 48 based on a calculation command from the central controller 40.

<Braking>
The left front wheel 51, the right front wheel 52, the left rear wheel 53, and the right rear wheel 54 are each provided with a brake rotor, and a caliper that decelerates the wheel by sandwiching the brake rotor with a pad (not shown) on the vehicle body side. Is installed. The caliper is a hydraulic type or an electric type having an electric motor for each caliper.

  Each caliper is basically controlled by a brake controller 451 (for front wheels) and 452 (for rear wheels) based on a calculation command from the central controller 40.

  A brake reaction force motor 52 is also connected to the brake pedal 11, and the reaction force is controlled by the pedal controller 48 based on a calculation command from the central controller 40.

<Integrated control of braking and driving>
In the present embodiment, different braking force and driving force are generated in the left and right wheels based on the side slip angle information, but it is the difference between the left and right braking force or driving force that contributes as the yaw moment. Therefore, in order to realize this difference, there may be a different operation such as driving one side and braking the other side. In such a situation, the central controller 40 determines the integrated control command in an integrated manner, the brake controller 451 (for front wheels), 452 (for rear wheels), the powertrain controller 46, the motor 1, the driving force distribution mechanism 2 Is properly controlled through

<Steering>
The steering system of the vehicle 0 has a steer-by-wire structure in which there is no mechanical connection between the steering angle of the driver and the tire turning angle. The power steering 7 includes a steering angle sensor (not shown), the steering 16, the driver steering angle sensor 33, and a steering controller 44. The steering amount of the driver's steering wheel 16 is detected by the driver steering angle sensor 33 and is processed by the central controller 40 via the steering controller 44. The steering controller 44 controls the front power steering 7 and the rear power steering 8 in accordance with this amount.

  A steering reaction force motor 53 is also connected to the steering 16, and the reaction force is controlled by the steering controller 44 based on a calculation command from the central controller 40.

  The depression amount of the brake pedal 11 of the driver is detected by the brake pedal position sensor 32 and is processed by the central controller 40 via the pedal controller 48.

<Sensor>
Next, the motion sensor group of this embodiment will be described. The sensor for measuring the movement of the vehicle in this embodiment is equipped with an absolute vehicle speedometer, a yaw rate sensor, an acceleration sensor, and the like. In addition, vehicle speed and yaw rate are estimated by a wheel speed sensor, and yaw rate and lateral acceleration are estimated simultaneously using a vehicle speed, a steering angle, and a vehicle motion model.

  The vehicle 0 is equipped with a millimeter-wave ground speed sensor 70, and the longitudinal speed Vx and the lateral speed Vy can be detected independently. Further, the wheel speeds of the respective wheels are inputted to the brake controllers 451 and 452 as described above. The absolute vehicle speed can be estimated by averaging the wheel speeds of the front wheels (non-drive wheels) from the wheel speeds of these four wheels. In this embodiment, when the speed of the four wheels simultaneously decreases by adding the signal of the acceleration sensor that detects the wheel speed and the acceleration in the longitudinal direction of the vehicle using the method disclosed in Japanese Patent Laid-Open No. 5-16789. However, it is configured to accurately measure the absolute vehicle speed (Vx). In addition, a configuration for estimating the yaw rate of the vehicle body by taking the difference between the left and right wheel speeds of the front wheels (non-driving wheels) is included, thereby improving the robustness of the sensing signal. These signals are constantly monitored as shared information in the central controller 40. The estimated absolute vehicle speed is compared and referred to the signal of the millimeter-wave to ground vehicle speed sensor 70, and is configured to complement each other when any of the signals is defective.

  As shown in FIG. 1, the lateral acceleration sensor 21, the longitudinal acceleration sensor 22, and the yaw rate sensor 38 are arranged near the center of gravity. Differentiating circuits 23 and 24 are mounted for differentiating the outputs of the respective acceleration sensors to obtain jerk information. Further, a differentiation circuit 25 for differentiating the sensor output of the yaw rate sensor 38 to obtain a yaw angular acceleration signal is mounted. In the present embodiment, it is illustrated that each sensor is installed in order to clarify the existence of the differentiation circuit. However, in actuality, the acceleration signal is directly input to the central controller 40 to perform various arithmetic processes and then the differentiation process. May be. Therefore, the yaw angular acceleration of the vehicle body may be obtained by performing differentiation in the central controller 40 using the yaw rate estimated from the wheel speed sensor.

  In order to obtain jerk, an acceleration sensor and a differentiation circuit are used. However, a jerk sensor disclosed in Japanese Patent Application No. 2002-39435 may be used.

  In this embodiment, a method for estimating lateral acceleration and lateral jerk is also employed.

  A method of estimating the lateral acceleration estimated value Gye and the lateral jerk estimated value Gye from the steering angle δ will be described with reference to FIG.

  First, in the vehicle lateral movement model, the steering angle δ [deg] and the vehicle speed V [m / s] are input, and the yaw rate r at the time of steady circle turning without dynamic characteristics is calculated.

  In this equation, stability factor A and wheelbase l are parameters specific to the vehicle, and are fixed values obtained experimentally. Further, the lateral acceleration Gy is expressed by the following equation.

  β is the side slip angle change speed of the vehicle, but it is a motion within the linear range of the tire force and is omitted because it is small. As described above, the lateral acceleration Gy is calculated by multiplying the yaw rate r and the vehicle speed V. This lateral acceleration does not take into account the dynamic characteristics of a vehicle having response delay characteristics in the low frequency region. This is due to the following reason. In order to obtain the lateral jerk information Gy of the vehicle, it is necessary to differentiate the lateral acceleration Gy in discrete time. At this time, the noise component of the signal is enhanced. In order to use this signal for control, it is necessary to pass through a low-pass filter (LPF), which causes a phase delay. Therefore, it was decided to obtain the jerk by adopting a method in which dynamic characteristics are omitted, acceleration having a phase earlier than the original acceleration is calculated, discrete differentiation is performed, and LPF having a time constant Tlpfe is passed. It may be considered that this expresses the dynamic characteristics of the lateral acceleration with a delay due to the LPF, and the obtained acceleration is simply differentiated. The lateral acceleration Gy is also passed through the LPF having the same time constant Tlpf. In this way, dynamic characteristics are given also to acceleration, and although illustration is omitted, it has been confirmed that the actual acceleration response can be well expressed in the linear range.

  As described above, the method of calculating the lateral acceleration and the lateral jerk using the steering angle has the advantages of suppressing the influence of noise and reducing the response delay between the lateral acceleration and the lateral jerk. However, this estimation method omits various vehicle slip information and ignores non-linear characteristics of tires. Therefore, when the skid angle increases, it measures the actual vehicle side acceleration and uses it. There is a need to do. FIG. 3 shows a method of obtaining lateral acceleration and lateral jerk information using the detection signal of the lateral acceleration sensor 21. Since noise components such as road surface irregularities are included, it is necessary to pass a low-pass filter (time constant Tlpfs) for the sensor signal (not dynamics compensation).

  In order to achieve both the advantages of lateral acceleration, jerk estimation, and measurement as described above, in this embodiment, a method of using both signals in a complementary manner as shown in FIG. 4 is adopted. The estimation signal and the detection signal are added together with a gain that is variable based on the side slip angle information. The variable gain Ke (Ke <1) for the estimated signal is changed to take a large value in a region where the side slip angle is small and to take a small value when the side slip increases. Further, the variable gain Ks (Ks <1) with respect to the detection signal is changed to take a small value in a region where the side slip angle is small and to take a large value when the side slip increases. With this configuration, there is little noise from the normal region where the side slip angle is small to the limit region where the side slip is large, and acceleration and jerk signals suitable for control can be obtained. These gains are determined by a function of side slip information or a map.

  So far, the apparatus configuration of the first embodiment of the present invention and the method for estimating the lateral acceleration and lateral jerk (these are included as logic in the central controller 40) have been described. Now, “acceleration / deceleration control command linked to side motion” and “yaw moment control command calculated from side slip information of vehicle” will be described.

<Acceleration / deceleration control command linked to lateral motion: G-Vectoring>
A guideline for acceleration / deceleration control linked to the lateral motion is disclosed in Non-Patent Document 1, for example.

  Basically, this is a simple control law in which the lateral jerk Gy is multiplied by the gain Cxy and a value obtained by adding a first-order delay is used as a longitudinal acceleration / deceleration command. It has been confirmed in Non-Patent Document 2 that a part of the linkage control strategy of the expert driver's lateral and back-and-forth motion can be simulated. Gx_DC in this equation is a deceleration component not linked to the lateral motion. This term is required when there is a foreseeable deceleration when there is a corner ahead or when there is a section speed command. The sgn (signum) term is a term provided so that the above operation can be obtained for both the right corner and the left corner. Specifically, the vehicle decelerates when turning in at the start of steering, and can stop when decelerating (because the lateral jerk becomes zero), and can perform an operation of accelerating when exiting the corner at the start of steering return. Acceleration / deceleration according to lateral jerk can be understood as decelerating when lateral acceleration increases and accelerating when lateral acceleration decreases. Further, referring to Equations 2 and 3, it can also be interpreted that the vehicle decelerates when the steering angle increases and accelerates when the steering angle decreases.

  Now, when controlled in this way, the combined acceleration of longitudinal acceleration and lateral acceleration (indicated as G) is a diagram in which the horizontal axis represents the longitudinal acceleration of the vehicle and the vertical axis represents the lateral acceleration of the vehicle. This is called “G-Vectoring control” because it is directed to make a transition (Vectoring).

  The vehicle motion when the control of Formula 1 is applied will be described assuming specific traveling. FIG. 5 assumes general traveling scenes of entering and exiting a corner, such as a straight path A, a transition section B, a steady turning section C, a transition section D, and a straight section E. At this time, the acceleration / deceleration operation by the driver is not performed. FIG. 6 is a time calendar waveform showing steering angle, lateral acceleration, lateral jerk, acceleration / deceleration command calculated by Equation 1, and braking and driving force of four wheels (61, 62, 63, 64). is there. As will be described in detail later, the front outer ring (62 when turning left), the front inner ring (61), the rear outer ring (64), and the rear inner ring (63) have the same value on the left and right (inner and outer). The braking force and driving force are distributed.

  First, the vehicle enters the corner from straight road section A. In the transition section B (points 1 to 3), the lateral acceleration Gy of the vehicle increases (the lateral jerk Gy is positive) as the driver gradually increases steering. At this time, according to Formula 1, the control vehicle decelerates (Gxc is negative) as the lateral acceleration Gy increases. Thereafter, when the vehicle enters the steady turning section C (points 3 to 5), the driver stops increasing steering and keeps the steering angle constant. At this time, since the lateral jerk Gy is zero, the acceleration / deceleration command Gxc is zero. Next, in the transition period D (points 5 to 7), the lateral acceleration Gy of the vehicle decreases due to the steering return operation of the driver. At this time, the lateral jerk Gy of the vehicle is negative, and the acceleration / deceleration command Gxc is positive from Equation 1 and the vehicle is accelerated. In the straight section E, the lateral jerk Gy is 0, so acceleration / deceleration control is not performed. As described above, the vehicle decelerates from the turn-in at the start of steering (point 1) to the clipping point (point 3), stops the deceleration during steady circle turning (points 3 to 5), and starts the steering switchback (points). Accelerate when exiting the corner from 5) (point 7). As described above, when G-Vectoring control is applied to the vehicle, the driver can realize the vehicle motion of acceleration / deceleration linked to the lateral motion only by steering for turning. Moreover, when this motion is expressed in a “gg” diagram showing the acceleration mode generated in the vehicle, with the longitudinal acceleration on the horizontal axis and the lateral acceleration on the vertical axis, it is a characteristic motion that transitions into a smooth curved line. Become. This curved transition is a clockwise transition as shown in the figure for the left corner, and a transition path inverted with respect to the Gx axis for the right corner, and the transition direction is counterclockwise. When the transition is made in this way, the pitching motion generated in the vehicle by the longitudinal acceleration and the roll motion generated by the lateral acceleration are suitably linked, and the peak values of the roll rate and pitch rate are reduced.

<Yaw moment control command>
Next, yaw moment control by left / right wheel drive / braking force distribution will be briefly described with reference to the drawings. FIG. 7 is a schematic diagram showing a situation in which a yaw moment in a direction (positive) that promotes turning is input from the counterclockwise turning standard state (A) of the vehicle 0. First, a lateral motion equation and a yawing (rotation) motion equation of the vehicle 0 in the standard state are shown.

  Where m: mass of vehicle 0, Gy: lateral acceleration applied to vehicle 0, Fyf: lateral force of front two wheels, Fyr: lateral force of rear two wheels, M: yaw moment, Iz: yawing moment of inertia of vehicle 0 , R: yaw angular acceleration of vehicle 0 (r is yaw rate), lf: distance between the center of gravity of vehicle 0 and the front axle, lr: distance between the center of gravity of vehicle 0 and the rear axle. In the steady circular turning state, the yawing motion is balanced (the yaw moment is zero), and the angular acceleration is zero.

  From this state, (B) shows an example in which only the inner rear wheel (left rear wheel 63) is braked to give a braking force (Fxfl), and (C) in addition to this, the inner front wheel is braked and braking force ( (D) is an example in which driving force (Fxfr, Fxrr) is applied to the outer front and rear wheels in addition to (C).

  In this case, the vehicle 0 has

The yawing moment of will work. Here, the force in the forward direction, that is, the driving direction is positive, the force in the braking direction is negative, and d indicates the distance (tread) between the left and right wheels. Further, the combined braking / driving force of the left front and rear wheels is Fxr, and the combined braking / driving force of the right front and rear wheels is Fxl.

  Similarly, FIG. 8 shows the distribution of braking / driving force that generates a negative moment, that is, a yaw moment in the negative direction, that is, clockwise (restoring side) when turning left. Also in this case, the equation of yawing motion is expressed by Equation 6.

  In the vehicle 0, both the positive and negative yaw moments can be generated because braking and driving force can be freely generated in each of the four wheels by a command from the central controller 40.

  Next, assuming specific traveling, the application of such yaw moment control to “slip prevention” will be described, including an outline of its operating conditions. FIG. 9 shows a case where “understeer” and “oversteer” are as follows for the traveling scenes of entering and exiting a corner, such as a straight path A, a transition section B, a steady turning section C, a transition section D, and a straight section E. The result of performing the “slip prevention control” in a situation where the vehicle slips and the vehicle deviates from the course is shown.

  The determination of “understeer” and “oversteer” will be briefly described using the three yaw rates and sideslip angles of FIG. FIG. 10 shows a steering angle, a yaw rate including an estimated value, an estimated vehicle side slip angle, a yaw moment command obtained therefrom, and braking of four wheels (61, 62, 63, 64), which are used for the intervention condition of the “slip prevention control”. , Driving force, vehicle longitudinal acceleration and lateral acceleration at this time are shown as time calendar waveforms.

  First, the yaw rate rδ obtained from the steering is calculated using Equation 2 using the stability factor A, the wheel base 1, the vehicle speed V, and the steering angle δ. Since the steering angle of the driver is used as an input, it can be considered that the intention of the driver is reflected best.

  Next, the yaw rate rGy obtained from the lateral acceleration is obtained by dividing the lateral acceleration by the vehicle speed as in Equation 7, omitting the side slip angle change β, as in Equation 3.

  This value is considered to indicate the revolution speed of the vehicle, and is considered to be an amount indicating the vehicle turning limit.

  Further, the yaw rate rs detected by the yaw rate sensor 38 indicates the actual rotation speed of the vehicle.

  The side slip angle β is defined as an arc tangent arctan (v / u) using the vehicle speed u in the front-rear direction and the vehicle speed v in the lateral direction. it can. For example, the arrow passing through the center of gravity of the vehicle in FIGS. 7 and 8 indicates the vehicle traveling direction, the angle formed by this and the longitudinal direction of the vehicle is the side slip angle, and the vehicle fixed coordinate system counterclockwise is positive. FIG. 7 shows a state in which oversteer → spin is induced when the side slip angle is negative and large. In contrast, FIG. 8 shows a state in which understeer → path protrusion is induced in a state where the side slip angle is positive and large.

  The side slip angle βδ obtained from the steering can be calculated as follows using a vehicle motion model.

  Here, m is the vehicle mass, and Kr is the cornering stiffness that represents the gain of the lateral force with respect to the unit side slip angle of the rear wheel.

  The side slip angle is detected by the millimeter-wave to ground vehicle speed sensor 70 independently of the longitudinal speed Vx and the lateral speed Vy,

You can ask for it,

As described above, the estimation accuracy may be improved by using an integration method or an observer estimation method using a vehicle motion model.

  The yaw rate rδ obtained from the steering, the yaw rate rGy obtained from the lateral acceleration, the yaw rate rs detected by the yaw rate sensor 38, the side slip angle βδ obtained from the steering, and the side slip angle β obtained from the detected or estimated value are used. A. Intervention conditions for “slip prevention control” The yaw moment control amount is determined.

A. Intervention condition The yaw rate obtained from the lateral acceleration is compared with the actual yaw rate, and when the actual yaw rate is small, it is determined that the vehicle is understeer, when it is large, it is oversteer, and when the skid angle is negative and large, it is determined to be oversteer. The threshold value, dead zone, and the like at this time are adjusted by a sensitivity test such as a test driver.

B. Yaw moment control amount Basically, yaw moment is added so that the actual value is close to the yaw rate obtained from steering and the side slip angle. Further, the side slip angle differential value or the like is multiplied by a gain adjusted to fit the feeling, and correction is performed using a value obtained by adding these.

  Now, understeer and oversteer occurrence situations in this embodiment, and “slip prevention control” corresponding thereto will be described with reference to FIG. First, there is a possibility that understeer occurs and deviates from the course at positions 2 to 3 in the transitional section B when entering the corner. This can be detected because the actual yaw rate rs is smaller than the yaw rate rGy obtained from the lateral acceleration. Therefore, a yaw moment command in the direction that promotes turning (positive) is calculated. In this embodiment, a braking force is generated on the left (inner) rear wheel, and a moment in the direction (positive) that promotes turning is applied.

  Further, in the steady turning section C, the equivalent cornering stiffness of the rear wheels is relatively lowered in the maximum lateral acceleration state, and it is likely that oversteer will occur to induce spin. This can be detected from the fact that the actual yaw rate rs is larger than the yaw rate rGy obtained from the lateral acceleration, and further, the side slip angle is larger than the threshold value βth, resulting in a large side slip angle. Can be detected. In order to restore the excessive yawing motion, in this embodiment, a braking force is generated on the right (outer) wheel and a clockwise moment is applied.

  Only when the yaw moment command is present, the front outer wheel (62 when turning left), the front inner wheel (61), the rear outer wheel (64) and the rear inner wheel (63) have different values on the left and right (inner and outer). The braking force is distributed so that

  By controlling the braking force (driving force) so that the left and right are different from each other in this way, yaw moment control for preventing the skidding of the vehicle can be realized. ) And stability can be ensured. However, at this time, as shown in FIG. 10, deceleration is applied according to the occurrence state of skid. Naturally, since a speed change or the like also occurs, even if the steering wheel is smoothly steered as shown in FIG. 10, the lateral acceleration also varies. When this motion is expressed in a “gg” diagram showing the acceleration mode generated in the vehicle, with the longitudinal acceleration on the horizontal axis and the lateral acceleration on the vertical axis, it is between 1 and 5 as shown in FIG. This will cause two counterclockwise loops. In this case, the pitching motion and the rolling motion become asynchronous, and the motion becomes jerky as compared with the motion during the G-Vectoring control of FIG. The acceleration / deceleration motion is not linked to the lateral motion generated by so-called driver input. This is the reason why a feeling of stall and discomfort occurs. In this embodiment, in response to such a problem, acceleration / deceleration linked to a steering operation operated from the daily operation area is automatically performed (G-Vectoring), and the side slip is reliably reduced in the limit operation area (side slip prevention control). By integrating control, there is little sense of incongruity and safety performance can be improved. Hereinafter, a specific configuration and method of the control device will be disclosed.

<Fusion of G-Vectoring control and "Slip prevention control">
FIG. 11 schematically shows the relationship between the arithmetic control logic of the central controller 40 and the observer that estimates the skid angle based on signals from the vehicle 0, the sensor group, and the sensors (although calculation is performed in the central controller 40). It is shown in. The entire logic is roughly composed of a vehicle motion model 401, a G-Vectoring controller unit 402, a yaw moment controller unit 403, and a braking force / driving force distribution unit 404.

  In the vehicle motion model, the estimated lateral acceleration (Gye), target yaw rate rt, and target skid angle βt are estimated from the steering angle δ input from the driver steering angle sensor 33 and the vehicle speed V using Formula 2, Formula 3 or Formula 8. To do. In this embodiment, the target yaw rate rt is set to be the same as the yaw rate rδ obtained from the steering described above.

  As for the lateral acceleration and lateral jerk input to the G-Vectoring controller 402, as shown in FIG. 4, a logic 410 that complementarily uses both signals is employed. The G-Vectoring controller 402 uses these lateral acceleration and lateral jerk to determine the component linked to the current vehicle lateral motion in the target longitudinal acceleration command GXt according to Equation 1. Further, the target longitudinal acceleration command GXt is calculated by adding the deceleration components Gx_DC that are not linked to the current lateral vehicle motion, and output to the braking force / driving force distribution unit 404.

  Here, Gx_DC is a term that is required when there is a predictive deceleration when there is a corner ahead or when there is a section speed command. Since the section speed command is information determined by the coordinates at which the vehicle is present, it can be determined by checking the coordinate data obtained by GPS or the like against the map information on which the section speed command is posted. . Next, foreseeable deceleration with respect to the front corner, although details of detection are omitted in the present embodiment, for example, a camera such as a monocular camera, a stereo camera, a ranging radar such as a laser and a millimeter wave, or GPS information, etc. It can be realized by taking information ahead of the car and accelerating / decelerating it according to the future lateral movement (lateral jerk) that has not yet become apparent. The future steering angle is estimated in the same manner as a so-called “driver model” that determines the steering angle using the route at the forward gaze distance / time and the deviation information at the predicted arrival position of the vehicle. Then, according to the future lateral jerk that will be generated in the vehicle by this steering operation, G-Vectoring is performed in the same manner as Equation 1 (Preview G-Vectoring), so that foreseeable deceleration with respect to the front corner becomes possible.

  Next, the yaw moment controller 403 is based on the deviations Δr and Δβ between the target yaw rate rt (rδ) and the target skid angle βt and the actual yaw rate and the actual (estimated) skid angle in accordance with the logic described above. The target yaw moment Mt is calculated and output to the braking force / driving force distribution unit 404.

  The braking force / driving force distribution unit 404 determines the braking / driving forces (Fxfl, Fxfr, Fxrl, Fxrr) of the four wheels of the vehicle 0 based on the target longitudinal acceleration command GXt and the target yaw moment Mt. In the following, first, basic allocation rules will be shown, and in addition to this, an indirect yaw moment control (IYC: Indirect Yaw-moment Control) effect characteristic of “G-Vectoring” control in this embodiment will be outlined. The characteristic points to note in braking force / driving force distribution will be described.

  First, the equations of motion for longitudinal motion, lateral motion, and yawing motion will be considered using FIG. Here, in order to improve the visibility of the equation, the force for two wheels is redefined as follows for the braking / driving force and the tire lateral force.

In this way,
<Previous movement>

<Lateral movement>

<Yawing exercise>

Furthermore, the description of the target yawing moment and the braking / driving force of each wheel is as follows:

It becomes. Here, when the mathematical expression 15 of the longitudinal motion and the mathematical expression 18 of the yawing moment are combined, it can be analytically solved with two unknowns and two equations as follows.

  Now, the braking force / driving force for the two right and left front wheels and the braking force / driving force for the two left and right front wheels can be compatible with the acceleration / deceleration command by the “G-Vectoring” control and the moment command by the “slip prevention control”. We were able to distribute power. Next, these are distributed to the front and rear wheels according to the vertical load ratio of the front and rear wheels. Now, assuming that the height of the center of gravity of the sprung mass of the vehicle 0 from the ground is h, and the vehicle 0 is accelerating / decelerating by Gxt, the load (Wf, Wr) for the two wheels of the front wheel and the rear wheel is respectively It becomes as follows.

  Therefore, the braking / driving force of the four wheels allocated according to the load ratio is as follows.

  However,

It is.

  This is the basic distribution rule of this embodiment. From Equation 23 to Equation 26, when the “G-Vectoring” control command value Gxt is zero, the yaw moment command based on the “slip prevention control” is distributed according to the static load of the front and rear wheels. When the “-Vectoring” control command value Gxt is not zero, the braking force / driving force for realizing the longitudinal acceleration is set to the same value for the left and right wheels so that no extra moment is generated, and the load distribution is It can be interpreted as being distributed to the ratio.

  Now, there is another point to consider in the fusion of “G-Vectoring control” and “side-slip prevention control” in the present embodiment. This is an indirect yaw moment control (IYC) effect resulting from the load dependency of the tire lateral force. This effect will be outlined with reference to FIG. For simplicity, it is assumed that lf (distance from the center of gravity point to the front axis) and lr (distance from the center of gravity point to the back axis) are equal. That is, it is assumed that the front and rear wheel loads when the front and rear wheels are stationary are equal.

  As shown in FIG. 13, the tire lateral force is proportional to the tire side slip angle when the side slip angle is small, and has a saturation characteristic when it is large. Since it is assumed that the loads on the front and rear wheels are equal, the same lateral force is generated for the same side slip angle. Here, when the vehicle 0 decelerates based on the “G-Vectoring” control value Gxt, the front wheel load increases as shown in Equation 21 and the rear wheel load decreases as shown in Equation 22. As a result, if the vehicle decelerates during turning, the lateral force Fyf of the front wheels increases and the lateral force Fyr of the rear wheels decreases. When this phenomenon is considered based on the yawing equation of motion of Equation 17, a moment that promotes turning works. Further, if the vehicle accelerates during turning, the restoring side yaw moment acts as shown in the lower part of FIG.

  In the “G-Vectoring” control linked to the lateral movement, when the lateral acceleration is increased, that is, when the turning is started, the vehicle is decelerated. Therefore, the yaw moment in the direction of promoting the turning works. Further, when the lateral acceleration decreases, that is, when the turn is finished, the acceleration is performed, so that the yaw moment in the direction toward restoring the turn and going straight goes on. These indicate that they have the potential to improve maneuverability and stability, respectively.

  Now, when the yaw moment for “slip prevention control” is added to such “G-Vectoring control”, there is a possibility that the control amount is too large to cause a problem. For example, when entering a corner. This may occur when a yaw moment for understeer prevention control is input from the viewpoint of “side slip prevention control” and “G-Vectoring” control is further added thereto. There is also a concern that the control amount for preventing understeer is too large, and oversteer is passed over neutral steer. In order to avoid such a situation, in this embodiment, when the G-Vectoring control is operating as shown in FIG. 14, the braking force / driving force unless the yaw moment control amount exceeds a certain threshold. It is configured to include logic that does not perform left and right distribution. Accordingly, when the yaw moment command is small, the operation is performed in the first mode (G-Vectoring), and when the yaw moment command is large, the operation is performed in the second mode (side slip prevention control). Further, the vehicle longitudinal acceleration realized in the second mode (side-slip prevention control) that generates different braking / driving forces on the left and right wheels of the four wheels is different from the acceleration / deceleration control command in (G-Vectoring). It can be seen that the correction control is performed so as to apply substantially the same braking / driving force to the left and right wheels of the four wheels so as to be close to each other (see also Equations 23 to 26). However, considering other embodiments where braking / drive distribution is not possible, such as a normal two-wheel drive vehicle and performing only brake control, different braking / driving forces are not necessarily generated on the left and right wheels of the four wheels. The vehicle longitudinal acceleration realized in the second mode (side slip prevention control) is not consistent with the acceleration / deceleration control command of (G-Vectoring). For example, if brake control is performed when the G-Vectoring command is zero, deceleration will inevitably occur. However, when the G-Vectoring control command is larger than the current speed generated by the skid prevention control command, the braking / driving is substantially equal to the left and right wheels of the four wheels so that the difference from the G-Vectoring control command is close. Correction control can be performed so as to apply force, and there are scenes for solving the problems of the present embodiment, which are within the scope of the present embodiment.

  Finally, the effect of this embodiment will be described with reference to FIGS. 15, 16, and 17. FIG. FIGS. 15, 16, and 17 are examples in which the present embodiment is applied to scenes to which only the “slip prevention control” shown in FIGS. 9 and 10 is applied. Further, FIG. 16 assumes the case where “under steer” and “over steer” occur at the same point as in FIGS. 10 and 15, but with a slight change in the steer characteristic.

  FIG. 15 shows acceleration / deceleration commands, yaw moment control commands, wheel braking / drive distribution determined according to the lateral motion generated according to the steering angle, vehicle yaw moment, vehicle longitudinal acceleration, vehicle lateral acceleration, and the like. Indicates acceleration. At this time, the yaw moment command for understeer and oversteer reduction has a larger absolute value than the control operation threshold value Mth (“side slip prevention control” operation). In the diagrams showing the braking force and driving force of each wheel, the dotted line is an acceleration / deceleration command signal for only “G-Vectoring” control, and the broken line is a deceleration amount based on a yaw moment command for “side slip prevention control”. By applying braking / driving force distribution to which this embodiment is applied, braking force is applied to the four wheels from point 1 to 3, and when a turning acceleration moment is generated, after point 2, a large braking force is applied only to the rear inner wheel. It can be seen that the wheel braking force is reduced, the longitudinal acceleration follows the command of the “G-Vectoring” control, and the yaw moment required by the “side-slip prevention control” is also realized. Further, at points 4 to 5, it is understood that the braking force of the front outer wheel and the rear outer wheel is reduced, the driving force is applied to the front inner wheel and the rear inner wheel, and the vehicle longitudinal acceleration and yaw moment follow as commanded. .

  In FIG. 16, a yaw moment command for understeer reduction is generated from point 2 to 3, but since there is an acceleration / deceleration command and the yaw moment command is smaller than the threshold value Mth, the left and right wheels Independent braking / driving control is omitted (same braking force for left and right wheels). On the other hand, at points 4 to 5, the yaw moment command is smaller than the threshold value Mth, but there is no acceleration / deceleration control command by “G-Vectoring” and load movement does not occur on the front and rear wheels. An example of operation is shown.

  As shown in FIGS. 15 and 16, when the braking force / driving force of the four wheels is controlled, the “G-Vectoring” control and the yaw moment control for “slip prevention” are performed as shown in FIG. Similarly, it is possible to realize a characteristic motion that makes a smooth curve transition on the “gg” diagram. This curved transition is a clockwise transition as shown in the figure for the left corner, and a transition path inverted with respect to the Gx axis for the right corner, and the transition direction is counterclockwise. When the transition is made in this way, the pitching motion generated in the vehicle by the longitudinal acceleration and the roll motion generated by the lateral acceleration are suitably linked, and the peak values of the roll rate and the pitch rate are reduced.

  Of course, it is necessary to consider a situation in which the system or driver issues a deceleration command when the vehicle ahead stops suddenly or receives information that there is an obstacle on the road. In such a situation, it is necessary to reflect these commands with the highest priority. This can be done by inputting the system from the part where Gx_DC is added in the logic diagram of FIG.

  As described above, according to the present embodiment, acceleration / deceleration linked to the steering operation that operates from the daily operation area is automatically performed, and the side slip is surely reduced in the limit operation area. It becomes possible to provide the technology and apparatus which enable.

0 vehicle 1 motor 2 driving force distribution mechanism 7 front power steering 8 rear power steering 10 accelerator pedal 11 brake pedal 16 steering 21 lateral acceleration sensor 22 longitudinal acceleration sensors 23, 24, 25 differentiation circuit 31 accelerator sensor 32 brake sensor 33 steering angle sensor 38 Yaw Rate Sensor 40 Central Controller 44 Steering Controller 46 Powertrain Controller 48 Pedal Controller 51 Acceleration Reaction Motor 52 Brake Reaction Motor 53 Steering Reaction Motor 61 Left Front Wheel 62 Right Front Wheel 63 Left Rear Wheel 64 Right Rear Wheel 70 Millimeter Wave vs Ground Vehicle Speed Sensor 121 Front left wheel motor 122 Right front wheel motor 451, 452 Brake controller

Claims (10)

In a vehicle motion control device that can independently control the driving force and braking force of four wheels,
A first mode for generating substantially the same braking / driving force on the left and right wheels of the four wheels based on an acceleration / deceleration control command linked to the lateral movement of the vehicle;
A second mode for generating different braking / driving forces on the left and right wheels of the four wheels based on the yaw moment control command calculated from the side slip information of the vehicle,
A vehicle motion control apparatus that selects the first mode when a yaw moment command is smaller than a predetermined value, and selects the second mode when the yaw moment command is larger than the predetermined value. The vehicle motion control apparatus according to claim 1,
The braking / driving force substantially equal to the left and right wheels of the four wheels is applied so that the difference between the vehicle longitudinal acceleration realized in the second mode and the acceleration / deceleration control command linked to the lateral motion is close. A vehicle motion control apparatus that is subjected to correction control. The vehicle motion control device according to claim 2,
The acceleration / deceleration control command is determined so as to make a curved transition on the diagram over time when a diagram is defined in which the horizontal axis represents the longitudinal acceleration of the vehicle and the vertical axis represents the lateral acceleration of the vehicle. Vehicle motion control device. The vehicle motion control device according to claim 2,
The acceleration / deceleration control command is a vehicle motion control device that is determined so that the vehicle decelerates when the lateral acceleration of the vehicle increases and the vehicle accelerates when the lateral acceleration of the vehicle decreases. The vehicle motion control device according to claim 2,
A vehicle motion control device, wherein the acceleration / deceleration control command is determined so that the vehicle decelerates when the steering angle of the vehicle increases and the vehicle accelerates when the steering angle of the vehicle decreases. The vehicle motion control device according to claim 2,
The acceleration / deceleration control command Gxc is

(Gy: vehicle lateral acceleration, Gy: vehicle lateral jerk, Cxy: gain, T: first-order lag time constant, s: Laplace operator, Gx_DC: driver, or acceleration / deceleration command automatically input based on external information The vehicle motion control device determined by The vehicle motion control apparatus according to claim 1,
The side slip information of the vehicle includes the handle angle and the handle angular velocity,
Estimated from each wheel speed or the vehicle speed Vx in the longitudinal direction of the vehicle directly measured from the ground speed and the vehicle lateral velocity Vy estimated from the vehicle yaw rate and vehicle lateral acceleration or directly measured from the ground speed. The side slip angle represented by arctangent arctan (Vy / Vx), or the side slip angular velocity that is a time derivative thereof, further consists of vehicle yaw rate, part or all of vehicle lateral acceleration,
A vehicle motion control device that calculates a large yaw moment control command in a direction to reduce the side slip angle when the side slip angle is large or the side slip angular velocity is large. The vehicle dynamic control device according to claim 7,
Measure the longitudinal acceleration and lateral acceleration of the vehicle, take the acceleration of the vehicle in the positive direction of the horizontal axis, decelerate in the negative direction, the lateral acceleration of the left direction of the vehicle in the positive direction of the vertical axis, negative When the yaw moment control command is a clockwise value, the left wheel is given a larger deceleration than the right wheel, or the right wheel is more than the left wheel. When a large driving force is applied and the yaw moment control command is a counterclockwise value, a vehicle motion control that applies a larger deceleration force to the right wheel than the left wheel or a larger driving force to the left wheel than the right wheel apparatus. The vehicle motion control device according to claim 2,
Measure the longitudinal acceleration and lateral acceleration of the vehicle, take the acceleration of the vehicle in the positive direction of the horizontal axis, decelerate in the negative direction, the lateral acceleration of the left direction of the vehicle in the positive direction of the vertical axis, negative As shown in the diagram with the acceleration in the right direction, when starting counterclockwise motion, it shows a clockwise curvilinear transition over time, and when starting clockwise motion, A vehicle motion control apparatus in which acceleration / deceleration in the front-rear direction is determined according to a lateral motion so as to show a counterclockwise curved transition as time passes. The vehicle motion control apparatus according to claim 1,
A vehicle motion control device that corrects an acceleration / deceleration control command linked to lateral motion in accordance with an acceleration / deceleration command that is automatically input based on a driver or external information.

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