WO2008107613A1

WO2008107613A1 - System and method for open loop control of an active anti-roll system by characterizing the yaw rate of a vehicle based on a nonlinear two-wheel model

Info

Publication number: WO2008107613A1
Application number: PCT/FR2008/050133
Authority: WO
Inventors: Alessandro Monti; Richard Pothin
Original assignee: Renault S.A.S.
Priority date: 2007-02-01
Filing date: 2008-01-29
Publication date: 2008-09-12
Also published as: FR2912083A1; FR2912083B1

Abstract

The invention relates to a method for controlling an active anti-roll system for a vehicle, characterized in that the control method comprises a determination of the desired yaw rate and a determination of the anti-roll torque as a function of the difference between the estimated yaw rate and the desired yaw rate, and in that the control method determines the estimated yaw rate from a nonlinear two-wheel model in order to determine the anti-roll torque value to be applied by the actuators as a function of the difference between the estimated yaw rate and the desired yaw rate.

Description

A system and method of open loop control of an active anti-roll system by typing the yaw rate of a vehicle based on a two-wheel nonlinear model.

The invention relates to the field of stabilization systems of a motor vehicle and stability modeling systems of a motor vehicle.

Current motor vehicles are equipped with a driver assistance system that acts both on the safety of the vehicle and its occupants and on driving comfort. Active anti-roll systems control the yaw behavior of the vehicle, helping to improve ride comfort and trajectory accuracy in situations involving abrupt changes in yaw rate.

EP 0 827 852 discloses a system and method for improving the stability of a vehicle with two anti-roll actuators. This paper proposes to determine the speed and steering angle of the vehicle, then to determine the theoretical rate of change of the yaw angle and to compare this theoretical rate of change in yaw angle with the rate of change of yaw. yaw angle actually perceived by the vehicle. The difference between the theoretical and actual values of the yaw rate and the value of the steering angle, as well as the value of the lateral acceleration, make it possible to determine the magnitude of the antiroll torque correction and its distribution between the nosewheel. and back. The calculation of the theoretical variation rate of the yaw angle is performed in a closed loop according to a linear model. A system using such a calculation can not simultaneously control the roll and the yaw rate of the vehicle. The invention relates to a system and a method for controlling an active anti-roll system, with one or two trains, for a motor vehicle making it possible to improve the control of the yaw behavior of such a vehicle. The invention also relates to a control method of an active anti-roll system based on a two-wheel nonlinear model.

In one embodiment, a method of controlling an active anti-roll system for a vehicle is defined, including determining the desired yaw rate and determining the antiroll torque based on the difference between the estimated yaw rate and the desired yaw rate, and the control method determines the yaw rate estimated from a two-wheel nonlinear model to determine the antiroll torque setpoint to be applied by the actuators as a function of the speed difference. of estimated yaw and desired yaw rate.

The desired yaw rate can be determined from a nonlinear two wheel model based on the input information. The difference between the desired yaw rate and the estimated yaw rate can be estimated and a load transfer coefficient determined according to the input information.

The control method determines the anti - roll torques to be applied to the stabilizer bars as a function of the gap between the desired yaw rate and the estimated yaw rate. The control method uses a calculation loop whose inputs are the desired yaw rate and the zero error load transfer coefficient. The zero error load transfer coefficient is used to initialize the calculation loop. The calculation loop is used to determine the estimated yaw rate and antiroll torque. Yaw rate is estimated from a non - linear physical model, allowing for static and dynamic behaviors. The non-linearity makes it possible to take into account the influence of the load distribution between the front and rear trains on the yaw rate of the vehicle. A reset signal of the calculation of the load transfer coefficient correction can be issued if the input information is outside the operating range of the vehicle in which the anti-roll correction influences the desired yaw rate. Resetting the calculation of the correction of the load transfer coefficient makes it possible to avoid calculating antiroll torque instructions which would have no effect on the current situation. Thus, the anti-roll system is active only in situations where it has an effect, the system becoming passive in other cases. This also avoids applying a correction that may cause unexpected behavior of the vehicle from the driver 's point of view.

The value of the load transfer coefficient may be saturated with the value of a load transfer coefficient of a passive vehicle if the value of the load transfer coefficient is greater than the value of a load transfer coefficient of load. 'a passive vehicle.

In such a method, at least one antiroll torque to be applied to a train can be determined as a function of the load transfer coefficient. The estimated yaw rate can be determined from a nonlinear model for estimating the lateral forces exerted on the vehicle from the load transfer coefficient and the input information.

The input information may include at least one of the following quantities, vehicle speed, steering angle, total antiroll torque, longitudinal acceleration, and lateral acceleration.

According to another aspect of the invention, a system for controlling an active anti-roll device for a vehicle is defined, comprising a calculation module receiving on its inputs signals coming from a measurement module capable of determining the driving parameters. of the vehicle, including vehicle speed, steering angle, total antiroll torque, longitudinal acceleration and lateral acceleration. The calculation module sends on its outputs control signals to the front and rear anti-roll torque actuators.

The calculation module may comprise a desired yaw rate determination module, a yaw rate determination module estimated from a non-yaw rate model. linear two - wheeled vehicle, a module for estimating the correction of the load transfer coefficient, a module for limiting the operating range of the module for estimating the correction of the load transfer coefficient, a module for the saturation of the load coefficient. load report, a module for estimating antiroll couples.

Other objects, features and advantages of the invention will become apparent on reading the following description, given solely by way of nonlimiting example and with reference to the appended drawings, in which: FIG. 1 shows a control system according to an aspect of the invention; and

- Figure 2 is a block diagram of the main steps of the control method.

In FIG. 1, a measurement module 1 comprises a vehicle speed measuring sensor 1, a steering angle sensor Ib, a longitudinal acceleration measurement sensor Ic, a sensor I d measuring the lateral acceleration and a sensor for measuring the total antiroll torque used in particular for two - train anti - roll systems. The control system comprises a desired yaw rate determination module 3 receiving at its inputs signals from the vehicle speed measuring sensor 1a through the link 9b and from the angle of the steering angle sensor 1b. the link 9a. The determination module 3 of the desired yaw rate is connected by at least one of its outputs via a link 15 to a first adder 17.

The first adder 17 is connected by an output 17a to an estimation module 4 of the correction of the load transfer coefficient. The estimation module 4 of the correction of the load transfer coefficient is connected by at least one of its outputs to a second adder 21 by a connection 18.

A branch 16 of the connection 15 is connected at the input of a limitation module 5 of the operating domain of the estimation module 4 of the correction of the load transfer coefficient. A The tap 10 of the connection 9 is also connected to one of the inputs of the limitation module 5 of the operating domain of the estimation module 4 of the correction of the load transfer coefficient. A connection 1 1 connects the limitation module 5 to the sensor Ic for measuring the longitudinal acceleration and a connection 12 connects the limitation module 5 to the sensor I d for measuring the lateral acceleration. The limitation module 5 is connected by at least one of its outputs to the estimation module 4 of the correction of the load transfer coefficient by the connection 19 and by at least one of its outputs to the second adder 21 via the connection 20.

The second adder 21 is connected by a connection 21a to a saturation module 6 of the load transfer coefficient. The saturation module 6 of the load transfer coefficient is connected by at least one of its outputs to a determination module 8 of the estimated yaw rate by the connection 22.

A branch 23 of the connection 22 is connected at the input of an estimation module 7 of the antiroll couples. The estimation module 7 of the anti-roll torques is connected by its inputs to the sensor for measuring the total antiroll torque by the connection 13 and to the sensor I d for measuring the lateral acceleration by the branch 14 of the connection 12. The module The anti-roll torque estimator 7 emits via the connection 24 an anti-roll torque setpoint for the nose gear and by connecting an antiroll torque setpoint for the rear axle. The determination module 8 of the estimated yaw rate is connected to a sensor 1 for measuring the speed of the vehicle by a connection 26, to a sensor Ib for measuring the steering angle by a connection 27 and to a sensor Ic for measuring the longitudinal acceleration by a connection 27. The determination module 8 of the estimated yaw rate is connected by at least one of its outputs via a connection 29 to the first adder 17.

The determination module 3 of the desired yaw rate receives the values of the vehicle speed v and the steering angle α. From these values, the determination module 3 of the speed of desired yaw determines the desired yaw rate based on a two - wheel model described by the following relationships:

With

Di = drift stiffness of front tires

D ₂ = rigidity of rear tire drift

1 ₁ = distance from the center of gravity of the front axle

1 ₂ = distance of the center of gravity of the rear axle m = mass of the vehicle v = speed of the vehicle δ = angle of drift of the vehicle α = steering angle of the front wheels

I _z = inertia of the vehicle body around its yaw axis ψ = angular yaw rate of the vehicle body

It is possible to consider a quasi-static relation by taking δ = 0.

The limitation module 5 determines a zero error load coefficient according to the physical modeling of the vehicle. This coefficient reflects both the behavior of the vehicle predicted by the physics and makes it possible to initialize the feedback loop formed by the estimation modulus 4 of the correction of the load transfer coefficient, the saturation module 6 of the coefficient charge transfer and the determination module 8 of the estimated yaw rate while the first adder 17 upstream of the estimation module 4 of the correction of the load transfer coefficient can not perform a signal default calculation on its negative entry. Thus, the feedback loop works from a value of a load transfer coefficient already close to reality, minimizing calculation times, response times and the risk of error. Simultaneously, the limitation module 5 receives the values of the vehicle speed, lateral acceleration, longitudinal acceleration and the desired yaw rate calculated by the desired yaw rate determination module 3. From these values, the limitation module 5 determines whether the vehicle is in a field where the antiroll system can have an influence. If this is not the case, the limitation module 5 issues a reset command to the estimation module 4 of the load transfer coefficient correction in order to stop the calculation of the correction of the load coefficient. load report.

In parallel, the first adder 17 subtracts the estimated yaw rate from the desired yaw rate, and sends the result at the input of the estimation module 4 of the correction of the load transfer coefficient. The correction of the load transfer coefficient and the zero error load transfer coefficient are summed and sent as input load factor of the saturation module 6 of the load transfer coefficient. The saturation module 6 of the load transfer coefficient verifies that the load coefficient sent to the input of the determination module 8 of the estimated yaw rate is less than the load transfer coefficient of a passive vehicle. Passive vehicle means a vehicle without anti-roll stabilization system. Thus, a vehicle equipped with an anti-roll system is guaranteed to be more stable than a vehicle which would be deprived of it, regardless of the result of the calculation. The saturated load transfer coefficient k _s is transmitted to the estimation module 7 of the anti-roll torques and to the determination module 8 of the estimated yaw rate.

The determination module 8 of the estimated yaw rate calculates the load on each wheel.

m,,, s mhγ, IT e ₂ m,,, _s mhγ, IL e ₂

And deduces the lateral forces:

F _yι = -γ (P ⁴ (F _zl ) + P ⁴ (F _{z 2} ))

With L = vehicle wheelbase g = gravitational constant γ _t = lateral acceleration γi = longitudinal acceleration h = height of the center of gravity of the vehicle relative to the ground ei = distance between the two front wheels e ₂ = distance between the two rear wheels k _s = load report of the active vehicle after saturation O ₁ = drift angle of the wheel P ⁴ = order 4 polynomial By injection into the following model, the determination module 8 of the estimated yaw rate can estimate ψ _e . mv (δ + ψ) = F _yl + F _y2 I _z ψ = hF _yi - l ₂ F _y2

The estimated yaw rate is then sent to the input of the first adder 17. At the same time, the antiroll torque estimation module 7 receives the values of the total antiroll torque Ct and of the transverse acceleration γ _t in addition to the load transfer coefficient. saturated k _s and deduces the torques to be applied to the front axle Ca l and to the rear axle Ca2 by the following equations If active anti-roll bars equip the front and rear trains, we have:

Cai = (l -k _p ) * Ct + (k _s -k _p ) * m * h * γ _t

Ca ₂ = k _p * Ct - (k _s -k _p ) * m * h * γ _t

If active anti-roll bars equip the front axle alone, we have:

Cal = (k _s -k _p ) * m * h * γ _t / k _p

If active anti-roll bars equip the rear axle alone, we have:

Ca 2 = (k _s -k _p ) * m * h * γ _t / (l -k _p )

With k _p = coefficient of load ratio of a passive vehicle

Figure 2 shows the main steps of the control method. The method begins in step 30 by acquiring the input data. In step 31, the control system estimates the desired yaw rate based on the input data. In parallel with step 32, the control system estimates the area of validity of the PID calculation and the control system calculates a load transfer coefficient for a zero error distribution value.

In step 33, the control system estimates a correction of the load transfer coefficient, in particular by a PID method with saturation of the integral term, also known by the term "anti-windup" device, according to the speed of desired yaw and estimated yaw rate. A signal from step 32 stops the calculation if the input data is outside the range of effect of the antiroll correction.

In step 34, the control system saturates the load transfer coefficient, the result of the sum of the load transfer coefficient for a zero error distribution value which is the value a load transfer coefficient for the same passive vehicle, and the correction of the load transfer coefficient

In step 35, the control system uses the saturated load transfer coefficient to estimate the estimated yaw rate from a nonlinear mathematical model. The speed obtained is compared with the desired yaw rate in step 33. The control system also estimates the correction of the load transfer coefficient.

In parallel, in step 36, the control system determines the antiroll torque instructions based on the saturated load transfer coefficient. The forward and reverse torque instructions are then sent to the concerned organs.

The system and method of controlling an anti-roll system makes it possible to determine the torque controls of a roll stabilization system based on a limited number of measurements. The determination of the torque controls of the anti - roll system is based on the estimation of the yaw rate according to a nonlinear model. The control method is of open loop type which allows a greater reactivity of the calculation. The limited number of sensors required for input measurements combined with the ease of access of these measurements makes it possible to reconcile cost and performance.

Claims

A method of controlling an active anti-roll system for a vehicle characterized in that the control method comprises a determination of the desired yaw rate and a determination of the anti-roll torque as a function of the difference between the estimated yaw rate. and the desired yaw rate, and a determination of the yaw rate estimated from a two-wheel nonlinear model to determine the anti-roll torque setpoint to be applied by the actuators as a function of the difference in speed between estimated yaw and desired yaw rate.

The method of claim 1 wherein the desired yaw rate is determined from a nonlinear two wheel model based on the input information.

The method of claim 2 wherein the control system estimates the difference between the desired yaw rate and the estimated yaw rate, and the control system determines a correction of the load transfer coefficient based on the input information.

The method according to claim 3, wherein a reset signal of the calculation of the correction of the load transfer coefficient is issued if the input information is outside the operating range of the vehicle in which the anti-roll correction influences the desired yaw rate.

5. The method according to claim 4, wherein the value of the load transfer coefficient is limited to the value of a load transfer coefficient of a passive vehicle if the value of the load transfer coefficient is greater than the value of the load transfer coefficient. a load transfer coefficient of a passive vehicle.

6. The method of claim 5 wherein at least one antiroll torque to be applied to a train is determined according to the load transfer coefficient.

The method of claim 5 wherein the estimated yaw rate is determined from a nonlinear model for estimating lateral forces exerted on the vehicle from the load transfer coefficient and input information.

A method in which the input information comprises at least one of the following quantities, vehicle speed, steering angle, total antiroll torque, longitudinal acceleration, and lateral acceleration.

9. Control system of an active anti-roll device for a vehicle, characterized in that it comprises a calculation module

(2) comprising a determination module (3) of the desired yaw rate, and a determination module (8) of the yaw rate estimated from a non-linear two-wheel model, the calculation module (2 ) receiving on its inputs signals from a measurement module (1) capable of determining vehicle running parameters, the calculation module (2) being able to determine the anti-roll torque setpoint to be applied by the actuators in function the difference between the estimated yaw rate and the desired yaw rate, and outputting control signals to the front and rear anti - roll torque actuators at its outputs.

10. Control system according to claim 9 wherein the calculation module (2) comprises in particular an estimation module (4) of the correction of the load transfer coefficient, a limitation module (5) of the operating range of the estimation module (4) for the correction of the load transfer coefficient, a saturation module (6) for the load transfer coefficient, an estimation module (7) for the antiroll couples.