FR2888194A1 - Motor vehicle`s e.g. track vehicle, front/rear wheel chamber controlling method, involves elaborating chamber angle threshold based on vehicle`s speed and estimated vehicle conditions, and transmitting threshold to distinct system - Google Patents

Abstract

The method involves estimating conditions e.g. drift angle, of a motor vehicle according to the speed of the vehicle, rate of yaw e.g. rotation speed of the vehicle around its center of gravity along a vertical axis, steering lock angle of rear wheels and previous information of the wheel chamber, of the vehicle. A chamber angle threshold is elaborated according to the speed of the vehicle and estimate conditions, and the elaborated threshold is transmitted to a distinct system of a wheel chamber control system. Independent claims are also included for the following: (1) a wheel chamber controlling system for a motor vehicle (2) a motor vehicle comprising a chassis and a wheel chamber.

Description

Active camber and vehicle control method and system

so equipped.

  The present invention relates to the field of land vehicle control systems, particularly wheeled motor vehicles.

  Traditionally, motor vehicles are provided with a chassis, a passenger compartment, wheels connected to the chassis by a suspension mechanism with front wheels steering controlled by a steering wheel available to the driver in the passenger compartment of the vehicle.

  The suspension mechanism allows substantially vertical oscillations of each wheel as a function of the load applied to this wheel and the guiding of the wheel, that is to say the control of the angular position of the wheel plane, the wheel plane being perpendicular to the axis of the wheel and passing through the center of the area of contact with the ground. The angular position of the wheel plane relative to the vehicle body is defined by two angles, the camber angle and the steering angle. The camber angle of a wheel is the angle separating, in a transverse plane perpendicular to the ground, the wheel plane of the median plane of the vehicle. The camber angle is positive when the upper part of the wheel deviates from the median plane towards the outside of the vehicle. The steering angle of a wheel is the angle separating, in a horizontal plane from the ground, the plane of the wheel of the median plane of the vehicle.

  On most vehicles, the camber angle is fixed for a particular position of suspension and steering. However, the camber angle undergoes variations induced by the deformations of the constituent elements of the suspension device caused by the forces exerted by the ground on the wheel. A current passenger vehicle can see its camber angle vary by several degrees under the transverse forces developed by the tire in a curve, regardless of the contribution of the roll of the vehicle body which generally tilts in the same direction under the effect of centrifugal force. This variation increases the camber angle for the outer wheel at the turn and decreases the camber angle for the inside wheel at the turn.

  The camber has a great influence on the vehicle behavior and the performance of the ground link.

  Document FR-A-2 833 233 describes a support linking a wheel to suspension elements of a vehicle, the support comprising camber means conferring on the wheel a degree of freedom of camber with respect to the suspension elements. The carrier is configured such that the wheel has a first instantaneous center of rotation about an average position, located in an interval of one to two and a half times the radius of the wheel above the ground, the carrier comprising control means capable of actively influencing the camber of the wheel. The control means are in the form of a jack and can be controlled according to the various driving parameters of the vehicle, for example the speed, the longitudinal or transverse acceleration, the steering wheel position, the speed of rotation of the steering wheel. , the torque exerted on the steering wheel, the roll, the roll speed, the roll acceleration, the yaw, the yaw rate, the yawing acceleration, the forces on the wheels, including at vertical load, the type driving behavior or behavior desired by the driver.

  This document describes a purely mechanical device and remains silent on the orders sent to the control means.

  US 6,634,654 discloses a passenger car wheel suspension, for varying the camber by means of a cylinder controlled by a camber computer receiving as input the current camber angle, the transverse acceleration, the longitudinal vehicle speed, steering angle, condition of the road and yaw rate. The camber computer can also receive data from an additional system, such as brake assist, dynamic driving programs, anti-lock brake systems. The camber computer can also exchange information with a computer computer.

  This document does not indicate how the orders sent to the camber actuators are generated.

  The present invention aims to remedy the shortcomings of the aforementioned documents.

  The present invention provides a method and a camber control system, for improving the behavior of the vehicle in the understeer or oversteer phases by rejecting external disturbances and parametric variations acting on the vehicle.

  The present invention provides a method and a camber control system, for controlling front and / or rear active camber systems by rejecting disturbances, such as a side gust, braking with asymmetric grip, a lever. from foot to curve, a variation in the mass of the vehicle or a variation of tire drift rigidities, and this from a small number of input data.

  The method of controlling wheel camber for a vehicle includes steps in which, depending on the vehicle speed, yaw rate, wheel angle, and an earlier wheel camber setpoint. vehicle state data is estimated, and, depending on the vehicle speed and the estimated status data, a current wheel cam instruction is developed.

  We can develop a current set of camber front and / or rear wheels.

  The steering angle of the wheels may include the steering angle of front and / or rear wheels.

  In one embodiment, a current set of camber wheels is developed for receiving an external signal.

  In one embodiment, the current camber setpoint of the wheels is sent to separate systems of the wheelbase control system.

  Advantageously, the estimated state data includes yaw rate and drift angle. The estimated state data may further include an estimated disturbance.

  The wheel camber control system for a vehicle includes a vehicle state data estimation module according to the vehicle speed, yaw rate, wheel angle, and an earlier wheel camber setpoint, and means for generating a current wheel camber setpoint based on vehicle speed and estimated condition data.

  Advantageously, the estimation module is capable of estimating the yaw rate and the drift angle.

  The vehicle includes a chassis, at least four wheels resiliently connected to the chassis, a camber adjustment mechanism and a camber control system. The control system includes a vehicle state data estimation module based on vehicle speed, yaw rate, wheel angle, and an earlier wheel steering setpoint. , and means for generating a current wheel camber setpoint as a function of vehicle speed and estimated state data.

  It is thus possible to reject the disturbances acting on the vehicle and improve the behavior of the vehicle during a braking curve, a curved foot, a single or double obstacle avoidance, a grip low or asymmetric or during an aerodynamic disturbance, such as a gust of wind.

  The invention applies to vehicles with four wheels, two front wheels and two rear wheels, three wheels or even vehicles with six or more wheels.

  The invention allows a vehicle to adopt the most stable behavior possible. whatever the driver demands or the condition of the roadway, while increasing the feeling of safety, comfort and driving pleasure.

  The present invention will be better understood on studying the detailed description of some embodiments taken as non-limiting examples and illustrated by the accompanying drawings, in which: FIG. 1 is a schematic view of a vehicle equipped with a control system according to one aspect of the invention; FIG. 2 is a logic diagram of the system according to one aspect of the invention; FIG. 3 is a logic diagram of the system according to another aspect of the invention; and FIG. 4 is a logic diagram of the system according to another aspect of the invention.

  As can be seen in FIG. 1, the vehicle 1 comprises a chassis 2, two front guide wheels 3 and 4 and two rear guide wheels 5 and 6, the wheels being connected to the chassis 2 by a not shown suspension mechanism. However, the rear wheels 5 and 6 may be non-steered.

  The vehicle 1 is completed by a steering system 7 comprising a rack 8 disposed between the front wheels 3 and 4, a rack actuator 9 adapted to orient the front wheels 3 and 4 via the rack 8 as a function of orders received, mechanically or electrically, from a steering wheel, not shown, available to a driver of the vehicle.

  The camber control system 10 comprises a control unit 11, a sensor 12 of the steering position of the front wheels 3 and 4, for example positioned on the actuator 9, a sensor 13 of the speed of rotation, for example wheels before, for determining the speed V of the vehicle, and a sensor 14 of the yaw rate tp of the vehicle. i.e., the speed of rotation of the vehicle around its center of gravity along a vertical axis.

  In addition, in the case of steered rear wheels, the system 10 comprises sensors 17 and 18 of the steering angle α 2 of the rear wheels 5 and 6, and actuators 19 and 20 for orienting said rear wheels 5 and 6. However, a single sensor 17 and a single actuator 19 may be sufficient for detecting the steering angle and the orientation of the rear wheels 5 and 6. The position and speed sensors may be of the optical or magnetic type. , for example Hall effect, cooperating with an encoder secured to a moving part while the sensor is non-rotating.

  The system 10 comprises camber actuators 21 to 24, mechanically linked to the suspension mechanism of the wheels 3 to 6 and capable of modifying the camber angle of said wheels 3 to 6. The actuators 21 to 24 are controlled by the control unit. 11. The system 10 comprises sensors 25 to 28 of the camber angle of the wheels 3 to 6.

  In the embodiment shown, the sensors 25 to 28 are associated with the camber actuators 21 to 24. However, the sensors 25 to 28 may be arranged separately from the actuators 21 to 24. The camber sensors 25 to 28 are connected to the camber actuator. control unit 11 for supplying said control unit 11 with the respective camber angles of said wheels 3 to 6.

  The control unit 11 can be implemented in the form of a microprocessor equipped with a random access memory, a read-only memory, a central unit and input / output interfaces for receiving information from the sensors. and to send instructions, in particular to the actuators 19 and 20.

  More specifically, the control unit 11 comprises an input block 29 receiving the signals from the sensors 12 to 14, 17, 18 and 25 to 28, and in particular the vehicle speed V, the yaw rate and the angle front wheel steering a, the steering angle of the rear wheels a2, and the camber angle of the front wheels y, and rear wheels y2, see Figure 2. The vehicle speed V can be obtained by making the average speed of the front wheels or rear wheels as measured by the sensors of an anti-lock braking system. In this case, there is provided a sensor 13 per wheel, the anti-lock system comprising an output connected to an input of the control unit 11 for providing the vehicle speed information. Alternatively, each sensor 13 is connected to an input of the control unit 11, the control unit 11 then performing the average of the wheel speed.

  The control unit 11 also comprises a state observer 30, for estimating the information that is not measured and which is necessary for the control, including the disturbances that act on the vehicle. The state observer 30 may for example be constructed from a non-dangling two-wheeled vehicle model assuming that a step-type disturbance can directly affect the yaw rate of the vehicle on a finite time interval. A dynamics that models the behavior of the actuator can be added. The state equations associated with the models extended by the perturbation, are as follows. Active camber model before 2 1 D1L1 + D2L + 2 D2L2 - DILI H1L1 VIz Iz Iz 1 + D2L2 - D1L1 D1 + D2 HI 0 MV2

MV MV

  1 0 0 - - 0 0 0 j y = (1 0 0 1) o \ J DILI \ Iz DI al + MV o D2 MV o o

Q + Yf d (0 ^ z a2 + y1

  2888194 9 Rear active camber model DILI + D2L2 D2L2 -DILI H2L2 V1Z IZ Iz H -1 + D2L2 - D, L1 DI + D2 2 MV2 MV MV oooo Q y = (1 0 0 1) in which we note y the output considered, M the total mass of the vehicle, I the inertia of the vehicle around a vertical axis passing through its center of gravity, L, the distance from the center of gravity to the front axle, L2 the distance from the center of gravity to rear axle, D, front drift rigidity, D2 rear drift rigidity, H, front camber rigidity, H2 rear camber rigidity, y, front camber angle measured, y2 angle of rear camber measured, yf1 the front camber angle filtered, Yf2 the rear camber angle filtered, a, the front wheel angle with the longitudinal axis of the vehicle, a2 the rear wheel angle with the longitudinal axis of the vehicle, V the speed of the vehicle, tai the yaw rate, [3 the drift angle, and T the response time of the actuator.

  From this model, we develop the classical theory of linear observers. The state observer 30 makes it possible to estimate the states of the vehicle and all the disturbances which act on the Q Yf2 o +

MV D1 o a1 +

D L 2 2

MV D2 o Iz o y 1 T a2 + \ 0) Yt2 d

  vehicle. The state observer can therefore use the following equations: Active camber observer before D1L1 + D 2L-2

_

D2L2 - DILI H L _ 1 1 0

D L 2 2

IZ IZ

VIZ o

IZ D2 MV

DI

  H D ,, L, DILI DI + D2 I -1 ± MV2 MV MV + aI + a2 + yI + K (V) (W -)

MV r o o o o o / 1 Yf d

  y = 0 0 0 1) Rear active camber observer DILI + D2L2 D, L2 - DILI -1+ D, L ,, - DILI

MV MV r

  o o o o o o o fl y 2 Iz Vlz Il L 2 2 0 \ \. 0 / D1L]

MV Iz DI o

  y + K (V) (yi - f3 + Yf ,, d a + DL \ ,, Iz D ,, MV oov = (1 0 0 1) d where A means that the values are estimated, d the disturbance experienced by the vehicle, and K (V) the state observer setting parameter that changes with the vehicle speed, the estimated value provides an estimate of the condition of the vehicle that could be used by other elements of the vehicle. the control unit 11.

  The control unit 11 further comprises an asymptotic disturbance rejection block 31.

  The asymptotic disturbance rejection block 31 makes it possible to make the perturbation d unobservable with respect to the output 15 considered, in general the yaw rate tif of the vehicle 1. The looping is performed on the perturbation d estimated by the state observer. 30. The expression of the command is - for the camber AV: yI = -Gal xd - for cambering AR: y2 = -Ga2 xd Yf 2 The control unit 11 is completed by an output 32. The output 32 of Disturbance rejection module 31 forms the general output of the control unit 11 and provides the camber angle setpoint y ,, 2 of the vehicle wheels.

  In the embodiment illustrated in FIG. 3, the control unit 11 is similar to the previous one and further comprises a situation detection module 33 which receives information via inputs 34 connected to outputs of other non-module modules. shown, such as a wheel lock anti-lock system control module and an anti-wheel slip control-command module. The situation detection module 33 is able to send instructions to the state observer 30 and the disturbance rejection block 31 in order to allow a better estimate of the disturbance d by providing the state observer 30 a representative signal for example of the activation of the anti-lock wheel system. The situation detection module 33 is also able to send disabling rejection block 31 inhibition instructions when the detected situation is such that it is desirable for the setpoint angle y1.2 to be zero.

  In the embodiments illustrated in FIGS. 2 and 3, the wheel cam reference angle y, .2 is provided to the front and rear wheel camber actuators 21 to 24. In addition, provision can be made, see FIG. 4, for supplying the setpoint angle y12 to other vehicle systems, for example an anti-lock system control-command module 35, in order to allow said module 35 to take account of the rear wheel camber when developing these braking instructions, see figure 4.

  By way of example, it is then possible during asymmetric braking, to brake more or less the wheels with the best grip, depending on whether the camber system is available or not to compensate for the yaw moment induced by such asymmetrical braking. . In this way, it is possible to significantly improve the handling of the vehicle during operation of the anti-lock wheel system.

  Alternatively, it can be provided that the module 35 is an anti-skid module wheels. It is also possible to provide a variant in which the system comprises a situation detection module 34, as illustrated in FIG. 3, and a control / command module of another system, as illustrated in FIG. setpoint angle Y1,2.

  The invention allows to benefit from the camber wheels y ,, 2 at desired times, especially as soon as the vehicle is in motion, and improves the road holding of the vehicle and the driving comfort experienced by the driver.

Claims (10)

  A method of controlling wheel camber for a vehicle, wherein in accordance with vehicle speed, yaw rate, wheel angle, and anterior camber setpoint, estimates vehicle status data, and, based on vehicle speed and estimated status data, a current wheel cam instruction is developed.   2-Method according to claim 1, wherein is developed a current camber instruction of the front and / or rear wheels.   The method of claim 1 or 2, wherein the steering angle of the wheels comprises the steering angle of front and / or rear wheels.   4-A method according to any one of the preceding claims, wherein is developed a current set of camber wheels for receiving an external signal.   A method according to any one of the preceding claims, wherein the current camber setpoint of the wheels is sent to separate systems of the wheelbase control system.   The method of any of the preceding claims, wherein the estimated state data comprises the drift angle 13.   The method of claim 6, wherein the estimated state data further comprises an estimated disturbance d.   A wheel camber control system (10) for a vehicle (1), comprising an estimation module (30) of vehicle status data as a function of vehicle speed, yaw rate, the wheel steering angle, and an earlier wheel camber setpoint, and means (31) for deriving a current wheel camber setpoint as a function of the vehicle speed, and data of estimated condition.   9-System according to claim 8, wherein the estimation module (30) is capable of estimating the drift angle P. 10-Vehicle (1) comprising a chassis (2), at least four wheels (3 to 6) elastically connected to the chassis, a camber adjustment mechanism and a system according to any one of claims 8 or 9 capable of controlling said mechanism.