VEHICLE WITH A DEVICE FOR ESTIMATING THE lateral tilt angle USING THE STEERING RACK FORCE

Abstract

A computer-implemented procedure, executed by data processing hardware, that causes the data processing hardware to perform operations including obtaining a measured position of a steering rack and determining an estimate of a shear force in an axle based on the measured position of the steering rack. The operations also include determining a measured value of the shear force in the axle using an inertial measurement unit. Furthermore, the operations include determining a difference between the estimated and measured shear force in the axle and determining an estimate of a surface's crossfall angle based on this difference.

Description

INTRODUCTION

[0001] The present invention relates generally to estimating a lateral tilt angle using a steering rack force and in particular to a vehicle according to the preamble of claim 1, as is known essentially from JP 2019-172 220 A or EP 1 346 856 A2. Further prior art is also known from DE 10 2016 204 018 A1 and DE 10 2006 016 746 A1.

[0002] Some methods for estimating the sideslip angle rely on lateral acceleration measurements taken by an inertial measurement unit (IMU). However, such methods can have inherent limitations due to the coupling between center of gravity (CG) dynamics and roll dynamics. In other words, measured lateral accelerations can typically only be used to estimate the sideslip angle if the lateral velocity has reached a steady state and the roll motion is negligible. SUMMARY

[0003] According to the invention, a vehicle is presented which is characterized by the features of claim 1.

[0004] One aspect of the invention provides a vehicle comprising a steering rack, an axle, an inertial measurement unit (IMU), data processing hardware, and storage hardware. The storage hardware communicates with the data processing hardware and stores instructions which, when executed by the data processing hardware, cause the data processing hardware to perform operations. These operations include obtaining a measured position of the steering rack and determining an estimate of a lateral force in the axle based on the measured position of the steering rack. Furthermore, the operations include determining a measured value of the lateral force in the axle using the IMU and determining the difference between the estimated and measured lateral force in the axle.Furthermore, the operations include determining an estimated value of a lateral tilt angle of a surface on which the vehicle is located, based on the difference.

[0005] Implementations of the invention may include one or more of the following optional features. According to some implementations, determining the estimated value of the lateral force in the axis based on the measured position of the steering rack includes determining an estimated value of a steering rack force load based on the measured position of the steering rack and determining the estimated value of the lateral force in the axis based on the estimated value of the steering rack force load.

[0006] According to some examples, the vehicle also includes a motor configured to drive the steering rack and involves determining the estimated lateral force in the axle based on the measured position of the steering rack, obtaining a measurement of the motor current, determining an estimated steering rack force load based on the measured motor current, and determining the estimated lateral force in the axle based on the estimated steering rack force load. According to some implementations, determining the measured lateral force in the axle using the IMU involves obtaining a lateral acceleration using the IMU and determining the measured lateral force in the axle based on the lateral acceleration.

[0007] According to some implementations, the operations also include obtaining a measurement of an environmental condition, determining that the measurement of the environmental condition satisfies a criterion, and setting the estimated crossfall angle based on the determination that the measurement of the environmental condition satisfies the criterion. According to some examples, determining that the measurement of the environmental condition satisfies a criterion includes determining that a windy condition exists, and setting the estimated crossfall angle includes discarding the estimated crossfall angle.

[0008] Furthermore, a system is described that includes data processing hardware and storage hardware communicating with the data processing hardware. The storage hardware stores instructions which, when executed in the data processing hardware, cause the data processing hardware to perform operations. These operations include obtaining a measured position of the steering rack and determining an estimate of a shear force in the axle based on the measured position of the steering rack. The operations also include determining a measured value of the shear force in the axle using an inertial measurement unit (IMU) and determining the difference between the estimated and measured shear force in the axle. Finally, the operations include determining an estimate of a surface's crossfall angle based on this difference.

[0009] Implementations of the invention may include one or more of the following optional features. According to some implementations, determining the estimated value of the lateral force in the axis based on the measured position of the steering rack includes determining an estimated value of a steering rack force load based on the measured position of the steering rack and determining the estimated value of the lateral force in the axis based on the estimated value of the steering rack force load. According to some examples, determining the estimated value of the lateral force in the axis is based on a mathematical steering compliance model that represents a first relationship between a steering rack force and a lateral acceleration.The mathematical steering compliance model can also represent a second relationship between a traction force and a lateral acceleration and a third relationship between a normal force and a lateral acceleration.

[0010] According to some examples, determining the estimated lateral force in the axle based on the measured position of the steering rack involves obtaining a measurement of the motor current of a motor configured to drive the steering rack, determining an estimated steering rack force load based on the measured motor current, and determining the estimated lateral force in the axle based on the estimated steering rack force load. According to some implementations, determining the measured lateral force in the axle using the IMU involves obtaining a lateral acceleration using the IMU and determining the measured lateral force in the axle based on the lateral acceleration.

[0011] According to some implementations, the operations also include obtaining a measurement of an environmental condition, determining that the measurement of the environmental condition satisfies a criterion, and setting the estimated crossfall angle based on the determination that the measurement of the environmental condition satisfies the criterion. According to some examples, determining that the measurement of the environmental condition satisfies a criterion includes determining that a windy condition exists, and setting the estimated crossfall angle includes discarding the estimated crossfall angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The drawings described here serve only to illustrate selected configurations; they show: Fig. 1 a view of an exemplary vehicle incorporating a roll angle estimation system according to the principles of the present invention; Fig. 2 a schematic view of the cross slope angle estimation system from Fig. 1; Fig. 3. A flowchart of an exemplary sequence of operations for a procedure for estimating a cross slope angle; Fig. 4. A flowchart of another exemplary arrangement of operations for a procedure for estimating a cross slope angle.

[0013] Corresponding reference symbols in all drawings denote corresponding parts. DETAILED DESCRIPTION

[0014] Some methods for estimating the roll angle rely on lateral acceleration measurements taken by an inertial measurement unit (IMU). However, such methods can have inherent limitations due to the coupling between center of gravity (CG) dynamics and roll dynamics. In other words, measured lateral accelerations can typically only be used to estimate the roll angle when the lateral velocity has reached a steady state and roll motion is negligible. Roll angles can be critical information that must be considered, for example, by electronic stability control (ESC) modules, roll stability control (RSC) modules, automatic stability control (ASC) modules, and / or advanced driver assistance system (ADAS) modules. Therefore, there is a need for improved methods and systems for estimating the roll angle.

[0015] Disclosed configurations estimate lateral tilt angles based on estimated steering rack forces, which, together with measured steering rack forces, can be used to distinguish between multiple causes of center of gravity (CG) lateral dynamics changes, such as steering and pedal inputs (and a resulting lateral velocity and lateral acceleration), roll dynamics (a resulting additional lateral force due to roll dynamics and CG mass), and a lateral tilt angle (a resulting additional lateral force due to a road gradient and CG mass). Specifically, disclosed configurations utilize a real-time estimation of the steering rack force or tie rod load, estimated using information obtained from a steering module or steering rack.The real-time estimation of the steering rack force or tie rod load can then be used to estimate the lateral force using a mathematical compliance model. Specifically, the estimated steering rack force and the estimated lateral force are not affected by the lateral acceleration due to the road's camber angle, so any difference between the estimated lateral force and a lateral force measured by an IMU provides an indication of the camber angle and its effects on the CG dynamics. The lateral force in an axle can be used here to estimate the lateral acceleration, taking into account the lateral acceleration, steering angle, and the inertial and geometric properties of a vehicle.The estimated lateral acceleration can be compared with a lateral acceleration measured by an IMU, and the difference between the estimated and the measured lateral acceleration can be used to estimate the roll angle.

[0016] Revealed configurations are immune to couplings between vehicle dynamics movements such as roll, pitch, and lateral dynamics. Severe driving scenarios or external environmental factors such as road conditions, crosswinds, and changes in terrain can lead to unintended roll, pitch, and lateral slide, making lateral angle estimation challenging. Accordingly, revealed configurations use sensor information / an estimate based on the steering rack force to estimate the lateral force at the front axle and map it to a lateral acceleration. Based on a comparison logic, revealed configurations estimate the lateral acceleration without dependencies on road gradients, thus distinguishing between lateral force / lateral acceleration generated by driver steering and pedal inputs and / or roll and pitch movements, crosswinds, and / or road gradients (lateral angle).

[0017] Although configurations in connection with a vehicle (e.g., a passenger car, a truck, an airplane, a train, a motorcycle, a drone, etc.) are shown and described here, it is to be understood that the disclosed configurations can be used additionally or alternatively for estimating the roll angle for any other type of device (e.g., a robot, a bicycle, a machine, etc.). A vehicle or device can be operated by a person or can operate independently.

[0018] In particular, based on Fig. 1 and Fig.Figure 2 shows a vehicle 10 (e.g., a passenger car, a truck, an airplane, a train, a motorcycle, a drone, etc.) together with a roll angle estimation system 12. As described in more detail below, the roll angle estimation system 12 can be used to estimate a roll angle ψ of a surface on which the vehicle 10 is located or moving.

[0019] The roll angle estimation system 12 includes a roll angle estimation module 20, which can be stored and executed by a body control module (BCM) 22 or by another control module of the vehicle 10. More precisely, the BCM 22 can, for example, store machine-readable instructions in memory hardware 24 to execute the Fig. 3 and / or Fig.The operations shown in Figure 4 are stored and can be executed by data processing hardware (e.g., a processor 26) of the BCM 22 or another control module to perform the operation. According to the example shown, the roll angle estimator 20 communicates with a steering module 32, which receives steering user inputs from a steering wheel 14 of the vehicle 10 and, based on these inputs, controls a steering rack 34 of the vehicle 10 to steer the vehicle 10 in accordance with the inputs. The steering module 32 provides the roll angle estimator 20 with measured values ​​of the steering rack position of the steering rack 34.

[0020] As shown in the example, the cross-slope angle estimation module 20 communicates with a slope angle module 44 and provides it with estimated cross-slope angles ψ. The slope angle module 44 can, for example, use estimated cross-slope angles ψ to perform ESC, RSC, ASC, and / or ADAS functions.

[0021] Furthermore, the side tilt angle estimation module 20 communicates with an inertial measurement unit (IMU) 36, a propulsion module 38, a chassis module 40, and an environment module 42. The IMU 36 provides the side tilt angle estimation module 20 with measured values ​​of the lateral acceleration a. y _ IMU and the roll rate γ̇. The propulsion module 38 provides measured values ​​of the propulsion torque τ for the crossfall angle estimation module 20. The chassis module 40 provides measured values ​​of the longitudinal velocity v for the crossfall angle estimation module 20. x(i.e., of speed). The environment module 42 provides measured values ​​of environmental conditions, such as wind speed, for the cross-slope angle estimation module 20.

[0022] The roll angle estimator 20 receives a measured position of the steering rack 34 from the steering module 32. Based on the measured position of the steering rack, the roll angle estimator 20 determines a first estimate of the lateral force in the axis. Furthermore, using the IMU 36, the roll angle estimator 20 determines a measured value of the lateral force in the axis. Subsequently, the roll angle estimator 20 determines the difference between the estimated and measured values ​​of the lateral force in the axis and, based on this difference, determines the roll angle of a surface on which the vehicle 10 is located or moving. According to some examples, the roll angle estimator 20 estimates the lateral force and the roll angle ψ using the following mathematical expressions: 1. The cross-slope angle estimation module 20 can estimate the shear force in an axis by calculating the following: Txtotal=Fxtotalcos(τ)[rkpcos(γ)+Rnomsin(γ)] Fxtotal=(Ftirex−Frolling)cos(δw)−Ftireysin(δw) Frolling=−frg min(1,vx)sign(vx) Tytotal=Fytotalcos(γ)[t cos(τ)+Rnom,sin(τ)] Fytotal=Ftireycos(δw)+(Ftirex−Frolling)sin(δw) Tztotal=Fztotalsin(γ)cos(τ)sin(δw)[cos(τ)(rkp+Rnomsin(τ))] Fztotal=Nfx2+ZgNfxayLfg Nfx=mgXrXr+Xf−maxZgXr+Xf 2. The lateral tilt angle estimation module 20 can estimate the total force transmitted to the tire by the steering rack using a mathematical steering compliance model 21, which represents a relationship between a traction force and a lateral acceleration and a relationship between a normal force and a lateral acceleration, by calculating the following: FySbW=(LFr−Fxtotalcos(τ)[rkpcos(γ)+Rnom.sin(γ)]−Tztotalcos(γ)[tcos(τ)+Rnom.sin(τ)]) x[k+1]=x[k]+Δt(kx[k]−xdes[k]) x[k+1]=Ax[k]+BU[k] A=[1+Δtk], B=I1⋅1 FySbW[k]=x[k] u[k]=(LFr−Fxtotalcos(τ)[rkυcos(γ)+Rnomsin(γ)]−Tztotalcos(γ)[t cos(τ)+Rnom sin(τ)]) M(y¨+i⋅vx)︸ay−IMU=Fyf−CI cos(δf)++Fyr−Clcos(δr) Izr˙=TM+L1Fyf−Clcos(δf)−L2Fyr−Clcos(δr) Fyf−Cl=Izr˙−TM+L2ay(L1+L2)cos(δf) Fyr−Cl=May−Fyf−Clcos(δf)cos(δr) The rear axle lateral force f yr-Cl This is based on the estimated front axle lateral force f. yf-Cl calculated according to vehicle dynamics in order to remove or reduce the effect of the lateral tilt angle on the estimated lateral force for the rear axle of vehicle 10. 3. The cross slope angle estimation module 20 can estimate the cross slope angle ψ by calculating the following: Fyf−SBWR=f(θm,θ˙m) Izr˙=TM+L1Fyf−SBWRcos(δf)−L2Fyr−SBWRcos(δr)+Ixzy¨ Fyr−SBWR=TM+L1Fyf−SBWRcos(δf)−Izr˙+Ixzy¨ M(y¨+r˙vx−ghθy¨−gcos(θ)sin(ψ))︸ay−SBWR=Fyf−SBWR cos(δf)+Fyr−SBWR cos(δr) ay−SBWR=Fyf−SBWR cos(δf)+Fyr−SBWR cos(δr)M A lateral force determined using lateral acceleration and IMU readings is compared here with a lateral force estimated using the steering rack estimation, which does not include lateral acceleration due to the road's crossfall angle. The discrepancy between the estimated and determined lateral force indicates the angle of inclination and its effect on CG dynamics.

[0023] The variables above are defined as follows: Variable name Description T xtotal The total resistance torque generated around the steering x-axis T yxtotal The total resistance torque generated around the steering y-axis T ztotal The total resistance torque generated around the steering z-axis F xtotal The total resistance force generated around the steering x-axis F yxtotal The total resistance force generated around the steering y-axis F ztotal The total resistance force generated around the steering z-axis R nom Nominal tire radius f r Frictional force N fX Rated tire force L f Front axle track width g Gravitational acceleration F rack The resistance force acting on the steering rack T total The total resistance torque generated around the steering axis F tirex Tire force in the longitudinal direction F tirey Tire force in the lateral direction F tirez Tire force in the normal direction F rolling Force generated by rolling resistance F ySBW The total resistance force generated around the steering y-axis in the SBW system F ySBW The total resistance force generated around the steering y-axis in the SBW system L Front axle track width F r The resistance force acting on the steering rack x State space x d Desired states A System matrix B Input matrix U System input K Time step I Identity matrix d w road wheel angle v x Vehicle forward speed y Vehicle lateral movement F yf-cl Front tire lateral force in the classic approach F yr-cl Rear tire lateral force in the classic approach T M Traction force L1 Front axle length L2 Rear axle length I z Vehicle moment of inertia in the z-direction i m Measured pinion angle I xx Vehicle moment of inertia in the x-direction h θ Vehicle rolling height F yf-TFOR Front tire lateral force in the classic approach (TFOR) a x Vehicle longitudinal acceleration a y_IMU Vehicle lateral acceleration measured by the IMU a y _ SBW Estimated vehicle lateral acceleration in the SBW module M Vehicle unladen weight X r Longitudinal distance between center of gravity and rear axle X f Longitudinal distance between center of gravity and front axle Z g The height of the center of gravity in relation to the ground L The length of the steering lever τ Caster angle γ Spread angle r kp Kingpin radius R nom . Nominal tire radius t Static offset τ Caster angle τ Caster angle L f axle length

[0024] Fig.Figure 3 is a flowchart of an exemplary sequence of operations for a computer-implemented method 300 for estimating a cross slope angle. The operations can be performed by data processing hardware (e.g., the processor 26 from Fig. 1) based on the execution of instructions stored in memory hardware (e.g., memory 24 from Fig. 1) are stored, will be carried out.

[0025] In operation 302, procedure 300 includes obtaining a measured lateral acceleration a y _ IMU , which is measured by the IMU 36. In operation 304, procedure 300 includes obtaining a measured roll rate γ̇, which is measured by the IMU 36, and determining a roll acceleration γ̇ and a roll angle h. Θ .

[0026] In operation 306, procedure 300 includes obtaining a torque τ from the propulsion module 38 and determining a traction force T. Mbased on the torque τ (see above). In operation 308, procedure 300 involves obtaining a velocity v. x (see above) of the chassis module 40 and the determination of a normal force based on the velocity v x (see above).

[0027] In operation 310, procedure 300 includes determining a steering rack force F. r based on the position of the steering rack 34 and the estimation of a lateral acceleration â y based on the steering rack force F r (see above). In operation 312, procedure 300 includes estimating the lateral tilt angle ψ using the vehicle's inertial properties and the measured lateral acceleration a. y_IMU and the estimated lateral acceleration y (see above).

[0028] In operation 314, procedure 300 involves obtaining a measurement of an environmental condition, determining whether the measurement of the environmental condition satisfies a criterion, and, based on the determination that the measurement of the environmental condition satisfies the criterion, setting the specified cross slope angle ψ. According to some examples, the environmental condition satisfies a criterion if a windy condition is present, and setting the specified cross slope angle involves rejecting the specified cross slope angle ψ.

[0029] Fig. Figure 4 is a flowchart of an exemplary sequence of operations for a computer-implemented method 400 for estimating a cross slope angle. The operations can be performed by data processing hardware (e.g., the processor 26 from Fig. 1) based on execution instructions stored in memory hardware (e.g., a 24-bit memory). Fig.1) are stored, will be carried out.

[0030] In operation 402, procedure 400 includes obtaining a measured position of a steering rack 34 of a vehicle 10. In operation 404, procedure 400 includes determining an estimated value of a lateral force in an axle of the vehicle 10 based on the measured position of the steering rack 34. In operation 406, procedure 400 includes determining a measured value of the lateral force in the axle using an IMU 36 of the vehicle 10.

[0031] In operation 408, procedure 400 involves determining the difference between the estimated and measured shear force at the axis. In operation 410, procedure 400 involves determining an estimated crossfall angle ψ of a surface on which vehicle 10 is located, based on this difference.

[0032] According to some implementations, determining the estimated value of the lateral force in the axle based on the measured position of the steering rack 34 involves determining an estimated value of a steering rack force load based on the measured position of the steering rack 34 and determining the estimated value of the lateral force in the axle based on the estimated value of the steering rack force load. According to some examples, determining the estimated value of the lateral force in the axle relies on a mathematical steering compliance model 21 that represents a first relationship between a steering rack force and a lateral acceleration. The mathematical steering compliance model may also represent a second relationship between a traction force and a lateral acceleration and a third relationship between a normal force and a lateral acceleration.

[0033] According to some examples, the vehicle also includes a motor configured to drive the steering rack 34, and includes determining the estimated value of the lateral force in the axle, obtaining a measured value of a motor current of the motor based on the measured position of the steering rack 34, determining an estimated value of a steering rack force load based on the measured motor current, and determining the estimated value of the lateral force in the axle based on the estimated value of the steering rack force load.

[0034] According to some implementations, determining the measured value of the shear force in the axis using the IMU 36 involves obtaining a lateral acceleration using the IMU 36 and determining the measured value of the shear force in the axis based on the lateral acceleration.

[0035] According to some examples, the operations also include obtaining a measurement of an environmental condition, determining that the measurement of the environmental condition satisfies a criterion, and setting the estimated crossfall angle based on the determination that the measurement of the environmental condition satisfies the criterion. Determining that the measurement of the environmental condition satisfies a criterion may include determining that a windy condition exists. Setting the estimated crossfall angle may include discarding the estimated crossfall angle.

Claims

[1] Vehicle (10) comprising: a steering rack (34); an axis; an inertial measurement unit (IMU) (36); Data processing hardware (26); and Storage hardware (24) that communicates with the data processing hardware (26) and stores instructions which, when executed by the data processing hardware (26), cause the data processing hardware (26) to perform operations that include: Obtaining a measured position of the steering rack (34); Determining an estimated value of a lateral force in the axis based on the measured position of the steering rack (34) on the basis of a mathematical steering compliance model (21) that represents a first relationship between a steering rack force and a lateral acceleration; Determining a measurement of the shear force in the axis using the IMU (36); Determining the difference between the estimated value of the shear force in the axis and the measured value of the shear force in the axis; and Determining an estimated value of a cross slope angle of a surface on which the vehicle (10) is located, based on the difference; characterized by , that the mathematical steering compliance model (21) also represents a second relationship between a traction force and a lateral acceleration and a third relationship between a normal force and a lateral acceleration. [2] Vehicle (10) according to claim 1, wherein determining the estimated value of the lateral force in the axle based on the measured position of the steering rack (34) comprises: Determining an estimated value of a steering rack force load based on the measured position of the steering rack (34); and Determining the estimated value of the lateral force in the axle based on the estimated value of the steering rack force load. [3] Vehicle (10) according to claim 1, wherein: the vehicle (10) further comprises a motor configured to operate the steering rack (34); and Determining the estimated value of the lateral force in the axle based on the measured position of the steering rack (34) includes: Obtaining a measured value of the motor current; Determining an estimated value of a steering rack force load based on the measured motor current; and Determining the estimated value of the lateral force in the axle based on the estimated value of the steering rack force load. [4] Vehicle (10) according to claim 1, wherein determining the measured value of the lateral force in the axle using the IMU (36) comprises: Obtaining a lateral acceleration using the IMU (36); and Determining the measured value of the lateral force in the axis based on the lateral acceleration. [5] Vehicle (10) according to claim 1, wherein the operations further comprise: Obtaining a measurement of an environmental condition; Determine that the measured value of the environmental condition satisfies a criterion; and Setting the estimated value of the cross slope angle based on the determination that the measured value of the environmental condition meets the criterion. [6] Vehicle (10) according to claim 5, wherein: Determining that the measured value of the environmental condition satisfies a criterion includes determining that a windy condition exists; and This includes setting the estimated value of the cross slope angle and rejecting the estimated value of the cross slope angle.

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