Swim angle control with an active differential

Abstract

Device (30, 40) for controlling the lateral dynamics of a vehicle (20), comprising an observer (31) which measures the actual drift angle (β H ) of the vehicle (20) is determined, wherein the device (30, 40) further includes a unit (10, 41) for specifying a target float angle (β) H ), a controller (32), and an actuator (33) for adjusting the float angle (β) H ) based on a control difference (e) of the float angle (β H ) exhibits, characterized in that the observer (31) has an actual swimming angle (β) related to the rear axle of the vehicle (20). H ) outputs that the unit (10, 41) is used to specify the target swimming angle (β H ) a mathematical model (10) that includes the target swimming angle (β H ) calculated with respect to the rear axle of the vehicle, and that the actuator (33) includes a controllable differential.

Description

State of the art

[0001] The invention relates to a device for controlling the lateral dynamics of a vehicle according to the preamble of claim 1.

[0002] Various vehicle dynamics control systems, such as ESP (Electronic Stability Program), are known from the state of the art to regulate a vehicle's lateral dynamics. Their primary function is to assist the driver in critical driving situations, such as when the vehicle oversteers or understeers. These systems typically control the vehicle's yaw rate. The actual yaw rate is measured by a yaw rate sensor, and the target yaw rate is calculated using a mathematical model, such as the so-called single-track model. If the deviation between the target and actual values ​​becomes too great, the system intervenes in the driving process. This intervention usually occurs via the wheel brakes or active steering.

[0003] While the yaw rate control described above can regulate the vehicle's movement around its vertical axis, it cannot influence the vehicle's orientation, i.e., the sideslip angle, as desired. Therefore, driving situations can occur in which the vehicle drifts sideways through a curve.

[0004] Documents DE 10 2004 036 565 A1 and DE 10 2006 019 790 A1 each disclose a device for controlling the lateral dynamics of a vehicle, comprising an observer that determines an actual sideslip angle of the vehicle, wherein the device further comprises a unit for specifying a target sideslip angle, a controller, and an actuator for adjusting the sideslip angle based on a control deviation of the sideslip angle.

[0005] German patent application DE 197 49 005 A1 discloses a device for controlling the lateral dynamics of a vehicle, comprising an observer that determines the actual sideslip angle of the vehicle, wherein the device has a controller and an actuator for adjusting the sideslip angle based on a control deviation of the sideslip angle.

[0006] Publication JP 2006 - 240 494 A discloses a device for controlling the lateral dynamics of a vehicle, wherein the device further comprises a unit for specifying a target swim angle, a controller, and an actuator for adjusting the swim angle based on a control deviation of the swim angle. Disclosure of the invention

[0007] Therefore, the object of the invention is to provide a device for controlling the lateral dynamics of a vehicle, with which the sideslip angle of the vehicle can be adjusted.

[0008] The problem according to the invention is solved by the features of independent claim 1. Further embodiments of the invention are the subject of dependent claims.

[0009] According to the invention, a sideslip angle controller is proposed that includes an observer which determines the current sideslip angle of the vehicle. For the purposes of the invention, an observer is defined as any device that determines the sideslip angle from various measured and / or estimated variables. The target sideslip angle is provided by a setpoint generator, according to the invention. This generator can, for example, calculate the target value using a model or specify a fixed value, such as zero or near zero. If the control deviation becomes too large, the sideslip angle controller intervenes in the driving operation using an actuator, such as an active differential, to generate a moment about the vehicle's vertical axis that corrects the sideslip angle.

[0010] The inventive sideslip controller preferably uses a differential, such as an active or passive differential (with brake) and / or a steering actuator, as the control element. The service brake, such as a hydraulic brake, is preferably not used by the sideslip controller. The aforementioned actuators have the advantage over the service brake that they react significantly faster than the wheel brakes of a hydraulic braking system.

[0011] According to a first embodiment, the target drift angle is calculated using a mathematical model. A preferred mathematical model is the single-track model according to Richert / Schunk, as illustrated in the figure description below. The target drift angle is preferably calculated relative to the rear axle of the vehicle. This method is less computationally intensive and therefore faster than calculating the target drift angle relative to the vehicle's center of gravity.

[0012] According to a second embodiment of the invention, the target slip angle is set to a fixed value, such as zero or close to zero. This further reduces the complexity of the control system. A constant target slip angle also reduces the wheel slip angles on the front axle. Furthermore, setting the target slip angle to zero simplifies starting on a road surface with µ-split conditions (different coefficients of friction on the left and right tires), as the tendency for the rear end to break away can be immediately corrected via the slip angle.

[0013] The calculation of the actual and / or target float angle can be performed at a repetition rate that depends on the vehicle's speed. In principle, the faster the vehicle travels, the higher the repetition rate should be.

[0014] The float angle controller according to the invention preferably generates a yaw moment value as its output or manipulated variable, which is then implemented by means of an actuator. The manipulated variable can also be implemented simultaneously by several actuators.

[0015] The float angle controller according to the invention can be implemented, for example, as a linear controller (state controller, etc.), a compensation controller (linear or non-linear) or as a so-called robust controller. Brief description of the drawings

[0016] The invention is explained in more detail below with reference to the accompanying drawings. These show: Fig. 1. A block diagram for the general description of a system as a mathematical model; Fig. 2 a representation of a vehicle in which the parameters of a mathematical vehicle model are shown; Fig. 3 a block diagram of a float angle controller according to a first embodiment; and Fig. 4 a block diagram of a float angle controller according to a second embodiment. Embodiments of the invention

[0017] The Fig. 1 and Fig. Figure 2 shows a general block diagram of a mathematical model 10 for a time-varying system.

[0018] A physical system, such as a vehicle 20, converts physical state variables, which can be summarized as an input vector ü(t), into other physical quantities, which can be summarized as an output vector. y→(t) can be represented. For example, when the driver turns the steering wheel, the steering angle δ forms F the state variable of the input vector u→(t). Vehicle 20 then enters the curve with a sideslip angle β and rotates around the z-axis with a yaw rate ψ̇. In this case, sideslip angle β and yaw rate ψ̇ represent the physical state variables of the output vector. y→(t).

[0019] The states of vehicle 20 change over time. This property is represented by a time-derived state vector. x→˙(t), an integration term 12 and a state vector x→(t) The state vector is shown. x→˙(t) This is derived from the sum of the state vector last updated by the system matrix A. x→(t) and the input vector ü(t) modified by the input matrix B. The updated state vector x→(t) is then modified by the output matrix C and finally as a sum with the input vector ü(t) modified by the through matrix D as the output vector y→(t) output. Mathematically, model 10 can be described as follows: x→˙(t)=A⋅x→(t)+Bu→(t) y→(t)=C⋅x→(t)+D⋅u→(t)

[0020] To model the lateral dynamics of the vehicle 20 from Fig. 2. Equations (1) and (2) look like this, for example: (β˙Ψ¨)=(CH+CVmvVVIV−CHIHmv2−1CHIH−CVIVJzCVIV2−CHIH2Jzv)⋅(βΨ˙)+(−CVmvCVIVJz)⋅(δF) (βΨ˙)=(11)⋅(βΨ˙)

[0021] The state variables of the state vector x→(t) The yaw angle β and the yaw rate ψ̇ are used here. These time-varying modeling parameters are constantly updated during the journey.

[0022] The modeling parameters of the system matrix A are the skew stiffnesses C. V ,C Hthe front and rear wheels, the distances I V ,I H the front and rear axles from the vehicle's center of gravity 24, the vehicle mass m and the moment of inertia J Z of the vehicle 20 around the z-axis, as well as the vehicle speed v .

[0023] The input matrix B contains the vehicle mass m and the moment of inertia J. Z around the z-axis, the skewing stiffness C V of the front wheel, the distance I V the front axle to the vehicle's center of gravity, as well as the vehicle speed v as modeling parameters.

[0024] Does the driver specify a certain steering angle δ? F Before, a swim angle β and a yaw rate ψ̇ are calculated using model 20 (output vector y→(t)). The actual yaw rate ψ̇ and the actual swim angle β of the vehicle are measured or estimated using a model.

[0025] According to a specific embodiment of the invention, the sideslip angle β is calculated with respect to the rear axle of the vehicle 20. For this purpose, the additionally applied yaw moment M is used. Z The actuator is introduced as an additional input variable into the input vector ü(t). The state vector x→(t) In this case, the swimming angle β is used. H The equations are formed at the rear axle of vehicle 20 and the yaw rate. The corresponding model equations are: (β˙HΨ¨)=(CH+CVmv(IH+IV)⋅CVmv2CHIH−CVIVJz(IH+IV)CVIVJzv)⋅(βHΨ˙)+(−CVmv0CVIVJz1Jz)⋅(δFMz) (βHΨ˙)=(11)⋅(βHΨ˙)

[0026] This model, which focuses on the rear axle of the vehicle, allows understeer or oversteer to be detected and corrected more quickly.

[0027] Fig. Figure 3 shows the control loop 30 of a vehicle dynamics controller according to a first embodiment of the invention, although only the control loop for the sideslip angle is shown. This includes a mathematical model 10 that defines the setpoint values ​​for the sideslip angle β. H and the yaw rate is calculated, for example, according to one of the previously described model equations, as well as an observer 31 who determines the actual swimming angle β H The angle of drift is determined either model-based or directly from various measured and estimated parameters. The method for determining the angle of drift is well-known in the art.

[0028] Model 10 receives the vehicle speed v and the steering angle δ from observer 31. F These measured values ​​are required for a continuous update of the model equations (5) and (6). The control error e is then calculated at node 34. The actual controller 32, such as a linear controller, determines a yawing moment M based on this value.Z , which should be applied to correct the vehicle's orientation. The yaw moment M Z is finally implemented by an actuator 33, such as a differential and / or a steering actuator.

[0029] In the second embodiment of control loop 40 of Fig. 4 becomes the target swimming angle β H not estimated, but permanently set to zero (or close to zero) (Block 41). Mathematical model 10 is thus completely eliminated, resulting in faster control. It also becomes apparent that constant control of the float angle β H The slip angles on the front axle are reduced to zero. This improves the vehicle's handling.

Claims

[1] Device (30, 40) for controlling the lateral dynamics of a vehicle (20), comprising an observer (31) which measures the actual sideslip angle (β H ) of the vehicle (20) is determined, wherein the device (30, 40) further includes a unit (10, 41) for specifying a target float angle (β) H ), a controller (32), and an actuator (33) for adjusting the float angle (β) H ) based on a control difference (e) of the float angle (β H ) shows, characterized by , that the observer (31) has an actual swimming angle (β) related to the rear axle of the vehicle (20). H ) outputs that the unit (10, 41) is used to specify the target swimming angle (β H ) a mathematical model (10) that includes the target swimming angle (β H ) calculated with respect to the rear axle of the vehicle, and that the actuator (33) includes a controllable differential. [2] Device according to claim 1, characterized by, that the unit (10, 41) represents the target swimming angle (β H ) depending on a steering angle (δ F ) and the speed (v) of the vehicle. [3] Device according to claim 1, characterized by , that the unit (10, 41) has a target float angle (β H ) with a value of zero or close to zero. [4] Device according to any one of the preceding claims, characterized by , that the actuator (33) includes a steering actuator. [5] Device according to claim 1, characterized by , that the controller (32) is a compensation controller or linear controller. [6] Device according to any of the preceding claims, characterized by , that means for controlling the swimming angle (β H ) as well as the yaw rate (ψ̇) are provided.

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