Vehicle control system with accurate sideslip estimation

Abstract

It is provided a vehicle control system allowing for reliable sideslip control, particularly, on banked roads. The vehicle control system comprises a sensor system configured for outputting current sensor data representing information on physical parameters related to a current movement of a vehicle and a sideslip estimation unit configured for estimating a roll angle of the vehicle currently moving on a road surface based on at least some of the current sensor data a roll decision parameter based on at least some of the current sensor data and the estimated roll angle, and a sideslip angle of the vehicle currently moving on the road surface based on at least some of the current sensor data, the estimated roll angle and the estimated roll decision parameter.

Description

[0001] VEHICLE CONTROL SYSTEM WITH ACCURATE SIDESLIP ESTIMATION

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a vehicle control system comprising a sensor system configured for outputting current sensor data representing information on physical parameters related to a current movement of a vehicle and a sideslip estimation unit for accurate estimation of the sideslip of the vehicle, in particular, when moving on banked curves.

[0004] BACKGROUND

[0005] Vehicles, in particular, automobiles are more and more frequently equipped with vehicle control systems assisting the driver of the vehicle in demanding driving situations. Vehicle control systems are also necessarily provided in the context of autonomous driving. Physical parameters related to the movement of the vehicle are provided as input data based on which the vehicle control system may analyze properties of the movement of the vehicle and control the movement by feedback operation of brakes, the steering, the engine, etc.

[0006] In the art, vehicles are equipped with some vehicle dynamics stability control that provide yaw rate control and sideslip correction control based on detected yaw rates and estimated sideslip angles of the vehicle during a current travel.

[0007] However, the roll angle of the vehicle is usually not known and, consequently, the estimate of the sideslip angle that depends on the roll angle when the vehicle is moving on a banked road surface, as in a banked curve, is erroneously much too large. An overestimate of the sideslip angle results in inappropriate action of the vehicle dynamics stability control, particularly, in banked curves.

[0008] In the art, this problem is addressed by switching off the control operation or at least the sideslip control of the same based on heuristic algorithms identifying the presence of a banked curve on which the vehicle is assumed to be currently moving. However, this approach not only demands for time consuming calibration processes but also results in reduced security due to the partial or complete suppression of the sideslip control. Another approach comprises the provision of additional elaborated sensor devices particularly configured for directly measuring the actual sideslip of the vehicle at high-precision but, however, at high costs.

[0009] SUMMARY

[0010] In view of the above, it is an objective underlying the present application to provide a vehicle control system that can properly take into account a current roll angle of a moving vehicle, in particular, a vehicle moving on a banked road / curve, without the need for high-cost sideslip angle sensor devices.

[0011] The foregoing and other objectives are achieved by the subject matter of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

[0012] According to a first aspect, it is provided a vehicle control system, comprising a sensor system configured for outputting current sensor data representing information on physical parameters related to a current movement of a vehicle and a sideslip estimation unit. The sideslip estimation unit is configured for estimating:

[0013] a) a roll angle of the vehicle currently moving on a road surface based on at least some of the current sensor data;b) a roll decision parameter based on at least some of the current sensor data and the estimated roll angle; and c) a sideslip angle of the vehicle currently moving on the road surface based on at least some of the current sensor data, the estimated roll angle and the estimated roll decision parameter.

[0014] It is noted that herein the term “road” is to be understood in the most general sense and denotes any driving surface including roads, street, highways, dirt roads and even off-road paths, etc. The road surface can, in particular, be a banked road surface, for example, a road surface of a banked curve. The (total) roll angle is given by the sum of the road bank angle (lateral inclination angle of the road towards a horizontal plane) and the relative vehicle roll angle of the vehicle with respect to the inclined road surface. The vehicle can be an automobile, for example, an electric car. The sensor system may comprise an inertial measurement unit sensor device, wheel speed sensor devices, and wheel steering angle sensor devices. The physical parameters related to a current movement of a vehicle may comprise the yaw rate, longitudinal acceleration and lateral acceleration of the vehicle, wheel speeds, steering angles, individual tire sideslip angle estimates, etc.

[0015] The vehicle control system according to the first aspect provides for an accurate real-time estimate of a roll angle of a vehicle, in particular, a vehicle currently moving in a banked curve, based on the estimated sideslip angle such that any control of the movement of the vehicle that may or should depend in some respect on the roll angle of the vehicle can be improved. Different from the art the estimation of the sideslip angle depends on the roll decision parameter that is estimated based on at least some of the current sensor data and the estimated roll angle. The estimated roll angle may be a corrected / re-calculated version of an initial estimate of the roll angle, the corrected / re-calculated version depending on the roll decision parameter.

[0016] For example, the roll decision parameter may indicate at least one of whether the vehicle is currently moving on a banked road and whether the vehicle is currently moving on the road surface having a low mue friction surface. Particularly, the roll decision parameter may indicate that the vehicle is currently moving on a banked road. Based on such kinds of indications the vehicle control system can perform reliable secure vehicle control, in particular, sideslip control.

[0017] According to an implementation, the sensor system of the vehicle control system according to the first aspect is configured for sensing a sensed lateral acceleration of the vehicle currently moving on the road surface and a yaw rate of the vehicle currently moving on the road surface and the sideslip estimation unit is configured for estimating:

[0018] I) a longitudinal velocity of the vehicle currently moving on the road surface;

[0019] II) the time derivative of a lateral velocity of the vehicle currently moving on the road surface based on the sensed lateral acceleration, the sensed yaw rate, the estimated longitudinal velocity, and the estimated roll angle; and III) the roll decision parameter based on the estimated time derivative of the lateral velocity of the vehicle and the sensed yaw rate.

[0020] This kind of estimating the roll decision parameter may result in a particularly reliable detection of a banked road or slow oversteering situation, for example, and, thus, reliable sideslip control.

[0021] According to a particular implementation of this procedure of estimating the roll decision parameter performed by the sideslip estimation unit, the sensor system is configured for sensing a plurality of values of the yaw rate of the vehicle within a predefined time window and the sideslip estimation unit is configured for estimating:

[0022] i) a plurality of values of the time derivative of the lateral velocity of the vehicle within the pre-defined time window;ii) the time derivatives of the plurality of sensed values of the yaw rate of the vehicle within the pre-defmed time window;

[0023] iii) the variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle; iv) the variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle;

[0024] and

[0025] v) the roll decision parameter based on the estimated variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle and the estimated variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle.

[0026] The sideslip estimation unit may, particularly, be configured for estimating the roll decision parameter based on sensor information provided by a CAN bus of the vehicle comprising, for example, information on a steering angle and / or wheel speeds.

[0027] Estimates of the roll decision parameter based on the above-defined variances may be particularly helpful for deciding whether the vehicle is currently moving on a banked road or on a low mue road surface with slow oversteering. Based on this decision reliable sideslip control can be provided by the vehicle control system.

[0028] According to a particular implementation the variances can be used as follows. The sideslip estimation unit is configured for estimating the roll decision parameter based on at least one of a ratio of the estimated variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle to the estimated variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle and a difference between the estimated variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle and the estimated variance of the estimated time derivatives of the plurality of sensed values of the yaw rate.

[0029] Estimates of the roll decision parameter using a mathematical procedure of using the above-defined variances by the sideslip estimation unit may be particularly helpful for deciding whether the vehicle is currently moving on a banked road or on a low mue road surface with slow oversteering. Based on this decision reliable sideslip control can be provided by the vehicle control system.

[0030] In the vehicle control system according to the first aspect and any implementation thereof the roll decision parameter may be a binary parameter, for example, indicating that either the vehicle is currently moving on a banked road or not. An efficient and relatively simple control logic can be implemented base on such a binary roll decision parameter. Alternatively, the roll decision parameter may be a continuously valued parameter that, for example, indicates magnitudes of a road bank angle or slow oversteering.

[0031] In the vehicle control system according to the first aspect and any implementation thereof the sideslip estimation unit may comprise a Kalman filter unit configured for estimating the roll angle and the sideslip angle of the vehicle currently moving on the road surface. The Kalman filter comprises a vehicle model in its output dynamics equation, which computes a model lateral acceleration using the estimated roll angle and sideslip angle and compares this modelled lateral acceleration to the sensed actual value. The difference between the modelled lateral acceleration and actual sensed lateral acceleration provided by the sensor system is used to correct the estimated states of the Kalman filter, i.e., the sideslip angle and the roll angle.

[0032] The predictor-corrector algorithm of a Kalman filter unit allows for accurately estimating the roll angle and sideslip in a recursive manner during movement of the vehicle.According to an implementation, the Kalman filter unit is configured for estimating the sideslip angle of the vehicle based on a set of measurement noise parameters and a set of process noise parameters and the sideslip estimation unit is configured for choosing the set of measurement noise parameters from at least two sets of measurement noise parameters and the set of process noise parameters from at least two sets of process noise parameters based on the estimated roll decision parameter. In particular, the sideslip estimation unit may be configured for choosing a first set of measurement noise parameters of the at least two sets of measurement noise parameters and a first set of process noise parameters of the least two sets of process noise parameters when the roll decision parameter indicates that the vehicle is currently moving on a banked road and choosing a second set of measurement noise parameters of the at least two sets of measurement noise parameters different from the first set of measurement noise parameters and a second set of process noise parameters of the least two sets of process noise parameters different from the first set of process noise parameters when the roll decision parameter indicates that the vehicle is currently not moving on a banked road.

[0033] Particular sets of measurement noise parameters and process noise parameters can be designed for specific driving situations. For example, if a banked road is detected as indicated by the roll decision parameter, sideslip angle estimation can be carried out by means of the Kalman filter unit based on measurement noise parameters and process noise parameters that are optimized for banked roads. For example, if slow oversteering on a low mue road surface is detected as indicated by the roll decision parameter, sideslip angle estimation can be carried out by means of the Kalman filter unit based on measurement noise parameters and process noise parameters that are optimized for slow oversteering situations.

[0034] The estimated sideslip angle provided by the sideslip estimation unit of the vehicle control system according to the first aspect and any implementation thereof can be used for reliable sideslip control. Thus, the vehicle control system according to the first aspect and any implementation thereof may further comprise a sideslip control unit configured for controlling a sideslip of the vehicle currently moving on the road surface based on the estimated sideslip angle provided by the sideslip estimation unit. Since the sideslip angle is estimated taking into account the estimated roll decision parameter, sideslip control can be performed more accurately as compared to the art.

[0035] Accurate sideslip control is of importance in the context of vehicle dynamics stability control systems (for example, Electronic Stability Control (ESC) or Dynamic Stability Control (DSC), Dynamic Stability and Traction Control (DSTC) or Active Stability Control (ASC)) that assist the driver of a vehicle in demanding driving situations, for example, high speed driving in banked curves, by controlling the yaw rate and sideslip by feedback operation of brakes, electric motors, actuators, etc. Thus, according to an implementation the sensor system comprises a yaw rate sensor device configured for obtaining a yaw rate of the vehicle currently moving on the road surface and, additionally to the sideslip control unit, a yaw rate control unit configured for controlling a yaw rate of the vehicle currently moving on the road surface based on the obtained yaw rate.

[0036] According to a second aspect, it is provided a method of estimating a sideslip angle of a vehicle currently moving on a road surface, comprising:

[0037] outputting, by a sensor system of a vehicle control system, current sensor data representing information on physical parameters related to the current movement of the vehicle; and

[0038] estimating, by a sideslip estimation unit of the vehicle control system,

[0039] a) a roll angle of the vehicle currently moving on a road surface based on at least some of the current sensor data; b) a roll decision parameter based on at least some of the current sensor data and the estimated roll angle; and c) a sideslip angle of the vehicle currently moving on the road surface based on at least some of the current sensor data, the estimated roll angle and the estimated roll decision parameter.The estimated roll angle may be a corrected / re-calculated version of an initial estimate of the roll angle, the corrected / re-calculated version depending on the roll decision parameter. The roll decision parameter may indicate at least one of whether the vehicle is currently moving on a banked road and whether the vehicle is currently moving on the road surface having a low mue friction surface.

[0040] According to an implementation the method further comprises:

[0041] sensing, by the sensor system, a sensed lateral acceleration of the vehicle currently moving on the road surface and a yaw rate of the vehicle currently moving on the road surface; and

[0042] estimating, by the sideslip estimation unit,

[0043] I) a longitudinal velocity of the vehicle currently moving on the road surface;

[0044] II) the time derivative of a lateral velocity of the vehicle currently moving on the road surface based on the sensed lateral acceleration, the sensed yaw rate, the estimated longitudinal velocity, and the estimated roll angle; and III) the roll decision parameter based on the estimated time derivative of the lateral velocity of the vehicle and the sensed yaw rate.

[0045] According to a further implementation, the method further comprises:

[0046] sensing, by the sensor system, a plurality of values of the yaw rate of the vehicle within a pre-defined time window; and

[0047] estimating, by the sideslip estimation unit,

[0048] i) a plurality of values of the time derivative of the lateral velocity of the vehicle within the pre-defined time window;

[0049] ii) the time derivatives of the plurality of sensed values of the yaw rate of the vehicle within the pre-defmed time window;

[0050] iii) the variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle; iv) the variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle;

[0051] and

[0052] v) the roll decision parameter based on the estimated variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle and the estimated variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle.

[0053] According to another implementation, the roll decision parameter is estimated by the sideslip estimation unit based on at least one of a ratio of the estimated variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle to the estimated variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle and a difference between the estimated variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle and the estimated variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle.

[0054] The roll decision parameter used in the method according to the second aspect and any implementation thereof may be a binary parameter or a continuously valued parameter.

[0055] According to an implementation of the method of the second aspect and any implementation thereof the roll angle and the sideslip angle of the vehicle currently moving on the road surface are estimated by a Kalman filter unit comprised by the sideslip estimation unit.Particularly, the sideslip angle of the vehicle may be estimated by the Kalman filter unit based on a set of measurement noise parameters and a set of process noise parameters and the method may further comprise choosing, by the sideslip estimation unit, the set of measurement noise parameters from at least two sets of measurement noise parameters and the set of process noise parameters from at least two sets of process noise parameters based on the estimated roll decision parameter.

[0056] According to a particular implementation a first set of measurement noise parameters of the at least two sets of measurement noise parameters and a first set of process noise parameters of the least two sets of process noise parameters are chosen by the sideslip estimation unit when the roll decision parameter indicates that the vehicle is currently moving on a banked road and a second set of measurement noise parameters of the at least two sets of measurement noise parameters different from the first set of measurement noise parameters and a second set of process noise parameters of the least two sets of process noise parameters different from the first set of process noise parameters are chosen by the sideslip estimation unit when the roll decision parameter indicates that the vehicle is currently not moving on a banked road.

[0057] According to third aspect, it is provided a method of vehicle control comprising the steps of the method of estimating a sideslip angle of a vehicle currently moving on a road surface according to the second aspect or any implementation thereof and further comprising controlling, by a sideslip control unit, a sideslip of the vehicle currently moving on the road surface based on the estimated sideslip angle.

[0058] The method according to the second aspect as well as the implementations of the method according to the second aspect and the method according to the third aspect provide the same advantages as the above-described vehicle control system according to the first aspect and implementations thereof and may be implemented in the above-described vehicle control system according to the first aspect and implementations thereof. On the other hand, the vehicle control system according to the first aspect and implementations thereof may be configured to perform the method according to the second aspect as well as the implementations thereof and the method according to the third aspect.

[0059] According to a fourth aspect, it is provided a computer program product comprising computer readable instructions for, when run on a computer, at least one of performing and controlling the steps of the method according to the second aspect or any implementation thereof or the method according to the third aspect.

[0060] According to a fifth aspect, it is provided a vehicle, an automobile, an electric car, an automated guided vehicle or a mobile robot comprising the vehicle control system according to the first aspect or any implementation of the same.

[0061] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.

[0062] BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In the following, embodiments of the present disclosure are described in more detail with reference to the attached figures and drawings, in which:

[0064] Figure 1 illustrates a vehicle control system comprising a sideslip estimation unit according to an embodiment.

[0065] Figure 2 illustrates a method of method of estimating a sideslip angle of a vehicle moving on a road surface according to an embodiment.

[0066] Figure 3 illustrates a roll angle estimated by a vehicle control system or a method of estimating a sideslip angle of a vehicle moving on a road surface according to an embodiment.

[0067] Figure 4 illustrates a sideslip estimation unit comprising a Kalman filter unit according to an embodiment.Figure 5 illustrates a sideslip estimation unit comprising a Kalman filter unit according to another embodiment.

[0068] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0069] Herein, it is provided a vehicle control system for a vehicle, for example, an automobile. The provided vehicle control system allows for accurate sideslip estimation, particularly, on banked curves and during slow oversteer caused by low mue friction road surfaces as, for example, snowy or icy surfaces.

[0070] Figure 1 illustrates an embodiment of a vehicle control system 100 according to the present disclosure. The vehicle control system 100 may be installed in a vehicle, for example, an automobile, and it comprises a sensor system 110 for providing a plurality of physical parameters related to a movement of the vehicle. The sensor system 110 may comprise an inertial measurement unit sensor device, wheel speed sensor devices, and wheel steering angle sensor devices. The inertial measurement unit sensor device may comprise a yaw rate sensor device, a sensor device for detecting the longitudinal acceleration of the vehicle and a sensor device for detecting the lateral acceleration of the vehicle. In general, the sensor system outputs current sensor data representing information on physical parameters related to a current movement of a vehicle.

[0071] Further, the vehicle control system 100 comprises a sideslip estimation unit 120 configured for estimating a sideslip angle (= arctan (lateral vehicle velocity component / longitudinal vehicle velocity component)) of the vehicle during a current movement of the vehicle on a road surface. The sideslip estimation unit 120 estimates a roll angle of the vehicle currently moving on a road surface based on at least some of the current sensor data. Further, the sideslip estimation unit 120 estimates a roll decision parameter based on at least some of the current sensor data and the estimated roll angle. The roll decision parameter may indicate whether the vehicle is currently moving on a banked road or not or whether the vehicle is currently moving on the road surface having a low mue friction surface or not. For example, the roll decision parameter is a binary parameter indicating whether or not a banked road surface is detected, or it may be a continuous valued parameter that, for example, indicates magnitudes of a road bank angle or slow oversteering.

[0072] Furthermore, the sideslip estimation unit 120 estimates a sideslip angle of the vehicle currently moving on the road surface based on at least some of the current sensor data, the estimated roll angle and the estimated roll decision parameter. For the same sensor outputs provided by the sensor system 110, the estimate of the sideslip angle for the case that the roll decision parameter indicates that the vehicle is currently moving on a banked road, for example, differs from the estimate of the sideslip angle for the case that the roll decision parameter indicates that the vehicle is currently not moving on a banked road. Based on the estimated roll decision parameter the sideslip estimation unit 120 can take into account whether or not the vehicle is currently moving on a banked road or not or whether the vehicle is currently moving on the road surface having a low mue friction surface or not and, therefore, can provide an accurate estimate of the actual sideslip angle.

[0073] The vehicle control system 100 further comprises a sideslip control unit 130 that may be part of a vehicle control configured for controlling elements of the vehicle, for example, brakes, the engine, electric motors, actuators, etc. based on the estimated sideslip angle. The vehicle control may also comprise a yaw rate control unit for controlling a yaw rate of the vehicle based on a sensed yaw rate provided by the sensor system 110.

[0074] Figure 2 represents a flow chart illustrating a method 200 of estimating a sideslip angle of a vehicle currently moving on a road surface. The method 200 may be implemented in the vehicle control system 100 shown in Figure 1. The method 200 comprises outputting S210, by a sensor system of a vehicle control system, current sensor data representing information on physical parameters related to the current movement of the vehicle. The current sensor data comprise a sensed lateral acceleration ayof the vehicle currently moving on the road surface as provided by an inertial measurement unit (IMU) of the sensor system anda yaw rate r of the vehicle currently moving on the road surface that is also provided by the IMU. Further, the method 200 comprises estimating S220, by a sideslip estimation unit of the vehicle control system, a (total) roll angle of the vehicle currently moving on a road surface based on at least some of the current sensor data. Additionally, the sideslip estimation unit provides an estimate of the longitudinal velocity vxof the vehicle currently moving on the road surface. The longitudinal velocity vxcan be estimated based on vehicle sensor data, for example, comprising CAN bus / sensor signals, and by appropriate algorithms.

[0075] The (total) roll angle to be estimated by the sideslip estimation unit is illustrated in Figure 3. Figure 3 shows an automobile 310 moving on a banked road surface 320 laterally inclined to a horizontal plane by the road bank angle Or. The total roll angle © is given by the sum of the road bank angle (lateral inclination angle of the road towards a horizontal plane) Or and the (relative) vehicle roll angle Os of the vehicle with respect to the (inclined) road surface 320. Note that in the example shown in Figure 3 the vehicle roll angle <Iy has a negative sign when measured to the left of a plane that is orientated perpendicular to the road surface 320. Any other sign convention may, alternatively, be used as it is considered appropriate.

[0076] The method 200 is particularly suitable for relatively large road bank angles ||Or|| > ||OS|| or ||Or|| » ||OS||.

[0077] Further, the method 200 comprises estimating S230, by the sideslip estimation unit, a roll decision parameter based on at least some of the current sensor data and the estimated roll angle (best. A first estimate of the roll angle may be corrected / re-calculated depending on the roll decision parameter.

[0078] Furthermore, the method 200 comprises estimating S240, by the sideslip estimation unit, a sideslip angle of the vehicle currently moving on the road surface based on at least some of the current sensor data, the estimated roll angle (best (in particular, a corrected / re-calculated version of an initially estimated roll angle, the corrected / re-calculated version depending on the estimated roll decision parameter) and the estimated roll decision parameter. The roll decision parameter may be a binary parameter indicating whether or not a banked road surface is detected, or it may be a continuous valued parameter that, for example, indicates magnitudes of a road bank angle or slow oversteering.

[0079] According to an embodiment, the method 200 also comprises estimating, by the sideslip estimation unit, the time derivative of a lateral velocity vyof the vehicle currently moving on the road surface based on the sensed lateral acceleration ay, the sensed yaw rate r, the estimated longitudinal velocity vx, and the estimated roll angle (best. In this embodiment, the roll decision parameter is estimated based on the estimated time derivative of the lateral velocity vyof the vehicle and the sensed yaw rate r. For example, the time derivative of a lateral velocity vyof the vehicle is estimated by

[0080] vy= ay— r vx— g sin 4> with 4> = <|)r+ 4>s

[0081] wherein g denotes the gravitational constant.

[0082] According to an embodiment, the method 200 also comprises sensing, by the sensor system, a plurality of values of the yaw rate n (i= 1 ,.., N) of the vehicle within a pre-defined time window and estimating, by the sideslip estimation unit:

[0083] a plurality of values of the time derivative of the lateral velocity vyiof the vehicle within the pre-defined time window (this, from previous sample times);

[0084] the time derivatives of the plurality of sensed values of the yaw rate r;of the vehicle within the pre-defined time window;

[0085] the variance Var^ of the plurality of estimated values of the time derivative of the lateral velocity vyiof the vehicle;the variance Var,-. of the estimated time derivatives of the plurality of sensed values of the yaw rate r;of the vehicle; and

[0086]

[0087] Depending on the ratio or the difference the roll decision parameter may be switched from one value to another or may adopt a value related to the ratio or the difference.

[0088]

[0089] Particularly, the provided method allows for a reliable discrimination between a vehicle driving on a banked road and on a low mue surface with slow oversteering. Accurate sideslip estimation on banked curves, particularly, in a dynamic drying environment, and during slow oversteer can be provided. Deviations of estimated sideslip angle from sideslip angle targetvalues provided by a model of the desired vehicle dynamics can be input into the vehicle control / sideslip control for controlling the sideslip of the actual movement of the vehicle.

[0090] According to an embodiment illustrated in Figure 4, the sideslip estimation unit 120 of the vehicle control system 100 shown in Figure 1 comprises a Kalman filter unit 125 configured for recursively estimating the sideslip angle of the vehicle based on system dynamics equations modelling physical laws of motion of the vehicle, one or more output dynamics equations, for example, the equation for the time derivative of a lateral velocity vyof the vehicle cited above, state extrapolation equations and covariance extrapolation equations. The Kalman filter unit 125 receives sensor outputs provided by the sensor system 110 of the vehicle control system 100. The Kalman filter unit 125 may be an extended / nonlinear Kalman filter unit (for example, an unscented Kalman filter unit) using a nonlinear vehicle model and sensor data. The nonlinear vehicle model may be a model based on classical physics considering rigid body motion of the vehicle based on the principles of kinematics and Newtonian dynamics. Alternatively or complementary, a neural network based vehicle model may be employed, if considered appropriate. The principle operation of Kalman filters for sideslip estimation is known in the art.

[0091]

[0092] As it is illustrated in Figure 5, according to another embodiment, at least two different sets of measurement noise parameters and at least two different sets of process noise parameters are provided. For sideslip estimation a particular set of measurement noise parameters from the at least two sets of measurement and process noise parameters may be chosen depending on the estimated roll decision parameter. For example, a first set of measurement noise parameters (optimized for banked roads) of the at least two sets of measurement noise parameters and a first set of process noise parameters (optimized for banked roads) of the least two sets of process noise parameters are chosen when the roll decision parameter indicates that the vehicle is currently moving on a banked road and a second set of measurement noise parameters (optimized for non-banked roads) of the at least two sets of measurement noise parameters and a second set of process noise parameters (optimized for non-banked roads) of the least two sets of process noise parameters are chosen when the roll decision parameter indicates that the vehicle is currently not moving on a banked road. Switching between parameter sets optimized for different situations facilitates estimation of the sideslip angle as well as re-estimation of the roll (bank) angle by the Kalman filter unit 125 with high accuracy to be used for the estimation of the sideslip angle.All previously discussed embodiments are not intended as limitations but serve as examples illustrating features and advantages of the invention. It is to be understood that some or all of the above-described features can also be combined in different ways.

Claims

CLAIMS1. Vehicle control system (100), comprising:a sensor system (110) configured for outputting current sensor data representing information on physical parameters related to a current movement of a vehicle; anda sideslip estimation unit (120) configured for estimating:a) a roll angle of the vehicle currently moving on a road surface based on at least some of the current sensor data;b) a roll decision parameter based on at least some of the current sensor data and the estimated roll angle; andc) a sideslip angle of the vehicle currently moving on the road surface based on at least some of the current sensor data, the estimated roll angle and the estimated roll decision parameter.

2. The vehicle control system (100) according to claim 1, whereinthe sensor system (110) is configured for sensing a sensed lateral acceleration of the vehicle currently moving on the road surface and a yaw rate of the vehicle currently moving on the road surface; andthe sideslip estimation unit (120) is configured for estimating:I) a longitudinal velocity of the vehicle currently moving on the road surface;II) the time derivative of a lateral velocity of the vehicle currently moving on the road surface based on the sensed lateral acceleration, the sensed yaw rate, the estimated longitudinal velocity, and the estimated roll angle; andIII) the roll decision parameter based on the estimated time derivative of the lateral velocity of the vehicle and the sensed yaw rate.

3. The vehicle control system (100) according to claim 2, whereinthe sensor system (110) is configured for sensing a plurality of values of the yaw rate of the vehicle within a pre-defined time window; andthe sideslip estimation unit (120) is configured for estimatingi) a plurality of values of the time derivative of the lateral velocity of the vehicle within the pre-defined time window;ii) the time derivatives of the plurality of sensed values of the yaw rate of the vehicle within the pre-defmed time window;iii) the variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle;iv) the variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle; andv) the roll decision parameter based on the estimated variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle and the estimated variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle.

4. The vehicle control system (100) according to claim 3, wherein the sideslip estimation unit (120) is configured for estimating the roll decision parameter based on at least one of:a ratio of the estimated variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle to the estimated variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle; anda difference between the estimated variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle and the estimated variance of the estimated time derivatives of the plurality of sensed values of the yaw rate.

5. The vehicle control system (100) according to any of the preceding claims, wherein the roll decision parameter indicates at least one of whether the vehicle is currently moving on a banked road and whether the vehicle is currently moving on the road surface having a low mue friction surface.

6. The vehicle control system (100) according to any of the preceding claims, wherein the roll decision parameter is a binary parameter.

7. The vehicle control system (100) according to any of the preceding claims, wherein the sideslip estimation unit (120) comprises a Kalman filter unit (122) configured for estimating the roll angle and the sideslip angle of the vehicle currently moving on the road surface.

8. The vehicle control system (100) according to claim 7, whereinthe Kalman filter unit ( 122) is configured for estimating the sideslip angle of the vehicle based on a set of measurement noise parameters and a set of process noise parameters; andthe sideslip estimation unit (120) is configured for choosing the set of measurement noise parameters from at least two sets of measurement noise parameters and the set of process noise parameters from at least two sets of process noise parameters based on the estimated roll decision parameter.

9. The vehicle control system (100) according to claim 8 in combination with claim 6, wherein the sideslip estimation unit (120) is configured for:choosing a first set of measurement noise parameters of the at least two sets of measurement noise parameters and a first set of process noise parameters of the least two sets of process noise parameters when the roll decision parameter indicates that the vehicle is currently moving on a banked road; andchoosing a second set of measurement noise parameters of the at least two sets of measurement noise parameters different from the first set of measurement noise parameters and a second set of process noise parameters of the least two sets of process noise parameters different from the first set of process noise parameters when the roll decision parameter indicates that the vehicle is currently not moving on a banked road.

10. The vehicle control system (100) according to any of the preceding claims, further comprising a sideslip control unit (130) configured for controlling a sideslip of the vehicle currently moving on the road surface based on the estimated sideslip angle.

11. A method (200) of estimating a sideslip angle of a vehicle currently moving on a road surface, comprising:outputting (S210), by a sensor system (110) of a vehicle control system (100), current sensor data representing information on physical parameters related to the current movement of the vehicle; andestimating, by a sideslip estimation unit (120) of the vehicle control system (100),a) a roll angle of the vehicle currently moving on a road surface based on at least some of the current sensor data (S220);b) a roll decision parameter based on at least some of the current sensor data and the estimated roll angle (S230);andc) a sideslip angle of the vehicle currently moving on the road surface based on at least some of the current sensor data, the estimated roll angle and the estimated roll decision parameter (S240).

12. The method (200) according to claim 11 , further comprising:sensing, by the sensor system (110), a sensed lateral acceleration of the vehicle currently moving on the road surface and a yaw rate of the vehicle currently moving on the road surface; andestimating, by the sideslip estimation unit (120),I) a longitudinal velocity of the vehicle currently moving on the road surface;II) the time derivative of a lateral velocity of the vehicle currently moving on the road surface based on the sensed lateral acceleration, the sensed yaw rate, the estimated longitudinal velocity, and the estimated roll angle; andIII) the roll decision parameter based on the estimated time derivative of the lateral velocity of the vehicle and the sensed yaw rate.

13. The method (200) according to claim 12, further comprising:sensing, by the sensor system (110), a plurality of values of the yaw rate of the vehicle within a pre-defined time window; andestimating, by the sideslip estimation unit (120),14i) a plurality of values of the time derivative of the lateral velocity of the vehicle within the pre-defined time window;ii) the time derivatives of the plurality of sensed values of the yaw rate of the vehicle within the pre-defmed time window;iii) the variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle;iv) the variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle;andv) the roll decision parameter based on the estimated variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle and the estimated variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle.

14. The method (200) according to claim 13, wherein the roll decision parameter is estimated by the sideslip estimation unit (120) based on at least one of:a ratio of the estimated variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle to the estimated variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle; anda difference between the estimated variance of the plurality of estimated values of the time derivative of the lateral velocity of the vehicle and the estimated variance of the estimated time derivatives of the plurality of sensed values of the yaw rate of the vehicle.

15. The method (200) according to any of the claims 11 to 14, wherein the roll decision parameter indicates at least one of whether the vehicle is currently moving on a banked road and whether the vehicle is currently moving on the road surface having a low mue friction surface.

16. The method (200) according to any of the claims 11 to 15, wherein the roll decision parameter is a binary parameter.

17. The method (200) according to any of the claims 11 to 16, wherein the roll angle and the sideslip angle of the vehicle currently moving on the road surface are estimated by a Kalman filter unit (122) comprised by the sideslip estimation unit (120).

18. The method (200) according to claim 17, whereinthe sideslip angle of the vehicle is estimated by the Kalman filter unit (122) based on a set of measurement noise parameters and a set of process noise parameters; andfurther comprising:15choosing, by the sideslip estimation unit (120), the set of measurement noise parameters from at least two sets of measurement noise parameters and the set of process noise parameters from at least two sets of process noise parameters based on the estimated roll decision parameter.

19. The method (200) according to claim 18 in combination with claim 16, whereina first set of measurement noise parameters of the at least two sets of measurement noise parameters and a first set of process noise parameters of the least two sets of process noise parameters are chosen by the sideslip estimation unit (120) when the roll decision parameter indicates that the vehicle is currently moving on a banked road; anda second set of measurement noise parameters of the at least two sets of measurement noise parameters different from the first set of measurement noise parameters and a second set of process noise parameters of the least two sets of process noise parameters different from the first set of process noise parameters are chosen by the sideslip estimation unit (120) when the roll decision parameter indicates that the vehicle is currently not moving on a banked road.

20. A method of vehicle control, comprising:the steps of the method according to any of the claims 11 to 19; andcontrolling, by a sideslip control unit (130), a sideslip of the vehicle currently moving on the road surface based on the estimated sideslip angle.

21. A computer program product comprising computer readable instructions for, when run on a computer, at least one of performing and controlling the steps of the method according to any of the claims 11 to 20.16

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