METHOD AND ALGORITHM FOR VIRTUALLY MEASURING AND ESTIMATING A TEAR BAR FORCE AND VALIDATING SENSOR DATA

Abstract

A vehicle contains a system that performs a procedure for operating the vehicle. A rack is coupled to a left wheel and / or a right wheel. A sensor receives a measurement of a dynamic parameter of the vehicle that is related to a force on the rack. A processor determines a first estimate of a rack force resulting from the force, based on the measurement of the dynamic parameter. It receives a second estimate of the rack force based on a signal from a wheel actuator coupled to the rack. A mediated rack force is selected from the first and second estimates. Based on this mediated rack force, a handwheel actuator coupled to the vehicle's steering wheel is activated to generate a feedback torque at the steering wheel.

Description

[0001] The present disclosure relates to the operation of a vehicle and in particular to a system and a method for applying a feedback torque to a steering wheel of a steering system for electromechanical steering of the vehicle such that it corresponds to a force on a rack of the vehicle.

[0002] Electromechanical steering systems were developed to steer a vehicle. In an electromechanical steering system, there is no mechanical connection between a steering wheel and a wheel actuator that steers the vehicle's wheels. Instead, communication occurs between the steering wheel and a controller, and between the controller and the wheel actuator. Due to the lack of a mechanical connection, external forces acting on the steering rack, such as a sudden jolt when the vehicle hits a pothole, are not transmitted to the steering wheel. Thus, the driver does not need to be aware of the driving conditions and external forces. Accordingly, it is desirable to provide a system and method for delivering feedback torque to the driver to better integrate the driver into the driving experience. SUMMARY

[0003] In an exemplary embodiment, a method for operating a vehicle is disclosed. A measurement of a dynamic parameter of the vehicle, which is related to a force on a rack of the vehicle, is obtained. The rack is coupled to a left wheel and / or a right wheel. A first estimate of a rack force is determined, the first estimate resulting from the force based on the measurement of the dynamic parameter. A second estimate of the rack force is determined, the second estimate being based on a signal from a wheel actuator coupled to the rack. An intermediate rack force is selected from the first and second estimates of the rack force.A handwheel actuator, coupled to the vehicle's steering wheel, is activated based on the mediated rack force to generate a feedback torque at the steering wheel.

[0004] In addition to one or more of the features described here, the dynamic parameter includes a force applied externally to a tire and / or an acceleration obtained from an inertial measurement unit (IMU), and / or a wheel angle and / or a longitudinal speed of the vehicle.

[0005] In addition to one or more of the features described herein, the method further comprises determining an estimate for the right wheel of the rack force using forces on a right front wheel of the vehicle, determining an estimate for the left wheel of the rack force using forces on a left front wheel of the vehicle, and determining the first estimate of the rack force based on the estimate for the right wheel and the estimate for the left wheel.

[0006] In addition to one or more of the features described herein, the procedure further includes determining an error in the measurement of the dynamic parameter used to calculate the first estimate and / or the signal from the impeller actuator used to calculate the second estimate.

[0007] In addition to one or more of the features described here, the procedure further includes selecting the second estimate as the mediated rack force if no error is found in the signal from the impeller actuator.

[0008] In addition to one or more of the features described here, the first rack force estimate and / or the second rack force estimate include a temporal sequence of forces.

[0009] In addition to one or more of the features described here, the steering wheel and rack are mechanically separated and each is coupled to an electromechanical steering system.

[0010] In a further exemplary embodiment, a system for operating a vehicle is disclosed. The system comprises a rack coupled to a left wheel and / or a right wheel, a sensor for obtaining a measurement of a dynamic parameter of the vehicle that is related to a force on the rack, and a processor.The processor is configured to determine a first estimate of a rack force resulting from the force based on the measurement of the dynamic parameter, to obtain a second estimate of the rack force based on a signal from an impeller actuator coupled to the rack, to select a mediated rack force from the first and second estimates of the rack force, and to activate a handwheel actuator coupled to the vehicle's steering wheel based on the mediated rack force to generate a feedback torque at the steering wheel.

[0011] In addition to one or more of the features described here, the dynamic parameter includes an external force applied to a tire and / or an acceleration obtained from an inertial measurement unit (IMU), and / or a wheel angle and / or (iv) a longitudinal speed of the vehicle.

[0012] In addition to one or more of the features described herein, the processor is further configured to determine an estimate for the right wheel rack force using forces on a right front wheel of the vehicle, to determine an estimate for the left wheel rack force using forces on a left front wheel of the vehicle, and to determine the first estimate of the rack force based on the estimate for the right wheel and the estimate for the left wheel.

[0013] In addition to one or more of the features described herein, the processor is further configured to determine an error in: (i) the measurement of the dynamic parameter used to calculate the first estimate; and / or (ii) the signal from the impeller actuator used to calculate the second estimate.

[0014] In addition to one or more of the features described here, the processor is further configured to select the second estimate as the mediated rack force if no error is found in the signal from the impeller actuator.

[0015] In addition to one or more of the features described here, the first rack force estimate and / or the second rack force estimate include a temporal sequence of forces.

[0016] In addition to one or more of the features described here, the steering wheel and rack are mechanically separated and each is coupled to an electromechanical steering system.

[0017] In yet another exemplary embodiment, a vehicle is disclosed. The vehicle includes a steering wheel, a rack coupled to a left wheel and / or a right wheel, a sensor for obtaining a measurement of a dynamic parameter of the vehicle that is related to a force on the rack, and an electromechanical steering system coupled to the steering wheel and the rack.The electromechanical steering system includes a processor configured to determine a first estimate of a rack force resulting from the force based on the measurement of the dynamic parameter, to obtain a second estimate of the rack force based on a signal from a wheel actuator coupled to the rack, to select a mediated rack force from the first and second estimates of the rack force, and to activate a handwheel actuator coupled to the vehicle's steering wheel based on the mediated rack force to generate a feedback torque at the steering wheel.

[0018] In addition to one or more of the features described here, the dynamic parameter includes a force applied externally to a tire and / or an acceleration obtained from an inertial measurement unit (IMU), and / or a wheel angle and / or a longitudinal speed of the vehicle.

[0019] In addition to one or more of the features described herein, the processor is further configured to determine an estimate for the right wheel rack force using forces on a right front wheel of the vehicle, to determine an estimate for the left wheel rack force using forces on a left front wheel of the vehicle, and to determine the first estimate of the rack force based on the estimate for the right wheel and the estimate for the left wheel.

[0020] In addition to one or more of the features described here, the processor is further configured to determine an error in the measurement of the dynamic parameter used to calculate the first estimate and / or the signal from the impeller actuator used to calculate the second estimate.

[0021] In addition to one or more of the features described here, the processor is further configured to select the second estimate as the mediated rack force if no error is found in the signal from the impeller actuator.

[0022] In addition to one or more of the features described here, the first rack force estimate and / or the second rack force estimate include a temporal sequence of forces.

[0023] The features and advantages described above, and further features and advantages of the disclosure, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further features, advantages and details appear only as examples in the following detailed description, which refers to the drawings; they show: Fig. 1 a vehicle according to an exemplary embodiment; Fig. 2 a schematic top view of the vehicle in an illustrative embodiment; Fig. 3 a diagram of the steering system in an illustrative embodiment; Fig. 4 a diagram illustrating the forces on the rack and the wheels of the vehicle; Fig. 5 a diagram of a system architecture for calculating suitable rack forces and subsequently providing a feedback torque; Fig. 6 a graph showing illustrative estimates of rack forces; and Fig. 7. A flowchart of a mediation process for the estimated rack forces. DETAILED DESCRIPTION

[0025] The following description is merely exemplary and is not intended to limit the present disclosure, its application, or uses. It should be understood that throughout the drawings, corresponding reference numerals denote similar or corresponding sections and features. As used herein, the term "module" refers to a processing circuit arrangement that may include an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or grouped) with memory executing one or more software or firmware programs, a combinational logic circuit, and / or other suitable components providing the described functionality.

[0026] According to an exemplary embodiment, Fig. 1. A vehicle 100. The vehicle has a center of mass 102, which is located at a distance Z.g above ground 104. A body-centered coordinate system 106 is shown for illustration. The body-centered coordinate system 106 includes an x-axis aligned with a longitudinal axis of the vehicle 100, a y-axis aligned along the lateral axis of the vehicle, and a z-axis pointing vertically downwards.

[0027] Fig. Figure 2 shows a schematic top view 200 of the vehicle 100 in an illustrative embodiment. The top view 200 shows a left front wheel 202, a right front wheel 204, a left rear wheel 206, and a right rear wheel 208. The left front wheel 202 and the right front wheel 204 are connected by a front axle 210. The left rear wheel 206 and the right rear wheel 208 are connected by a rear axle 212.

[0028] A rack 214 is coupled to the front axle 210. The rack 214 moves in a transverse direction (along the y-axis) based on the steering angle of a steering wheel 216. The movement of the rack 214 changes the wheel angle (RAA) of the left front wheel 202 and the right front wheel 204. A steering system 218 controls the steering of the vehicle. In several embodiments, the steering system 218 is an electromechanical steering system.

[0029] The vehicle 100 also contains various sensors for detecting dynamic parameters of the vehicle. The sensors include an inertial measurement unit (IMU) 220, which measures accelerations occurring on the vehicle along one or more axes; tire force sensors 222, which measure forces on the tires; a wheel angle sensor 224 (RWA sensor), which measures a wheel angle (RWA); and a speedometer 226, which measures a longitudinal speed v. xThe vehicle's measurements are not limited to these. The steering system 218 communicates with these sensors and can receive data, perform calculations based on the data, and determine various forces on the rack 214 using this data.

[0030] Fig. Figure 3 is a diagram 300 of the steering system 218 in an illustrative embodiment. The steering system 218 communicates with both the steering wheel 216 and the rack 214. The steering wheel 216 and the rack are mechanically separated. The steering system 218 includes a steering rod 302, a steering column 304, and a controller 306.

[0031] The steering rod 302 contains a steering angle sensor 308 and a handwheel actuator 310. The steering angle sensor 308 measures the steering angle (SWA) of the steering wheel 216 by measuring the rotation angle of the steering rod 302. The steering angle sensor 308 provides a signal indicating the SWA to the controller 306. The controller 306 can also provide a feedback torque instruction to the handwheel actuator 310, which, based on this torque instruction, provides feedback torque to the steering rod 302.

[0032] The steering column 304 contains a wheel actuator 312 and a wheel angle sensor 314. The wheel angle sensor 314 measures the wheel angle (RA) of the wheels (e.g., of a left front wheel 202 and / or a right front wheel 204) and sends the RWA to the controller 306. The controller 306 sends a suitable signal to the wheel actuator 312. The wheel actuator 312 controls the rotation of a pinion 316. The pinion 316 is mechanically connected to the rack 214. A rotation of the pinion 316 thus moves the rack laterally, thereby changing the RWA of the wheels.

[0033] The controller 306 may include a processing circuit arrangement that may contain an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or grouped) with memory executing one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the described functionality. The controller 306 may include a non-transient, computer-readable medium that stores instructions which, when processed by one or more processors of the controller 306, implement a method for providing feedback torque to the steering wheel 216 according to one or more embodiments described in detail herein.

[0034] To steer the vehicle 100°, the steering angle sensor 308 sends the steering angle angle (SWA) to the controller 306. The controller 306 calculates a suitable steering angle angle (RWA) for the wheels based on the SWA and sends the appropriate RWA to the wheel actuator 312. The wheel actuator 312 then controls the rack 214 to implement the RWA at the wheels. To provide feedback to the driver, the wheel angle sensor 314 provides a wheel angle to the controller 306. The controller 306 calculates forces on the rack based on the dynamic parameter data received from the sensors, determines a suitable feedback torque so that the steering wheel responds to the forces on the rack, and provides the feedback torque to the handwheel actuator 310. The handwheel actuator 310 applies the feedback torque to the steering rod 302.

[0035] Fig. Figure 4 is a diagram 400 illustrating forces on the rack 214 and the wheels of the vehicle 100. The rack 214 is connected to the left front wheel 202 by means of a left steering lever 402 and to the right front wheel 204 by means of a right steering lever 404.

[0036] A force appears at the rack 214 as a result of externally exerted forces experienced at the wheels, such as wheel contact forces, rolling forces, etc. The methods disclosed here are discussed using the right front wheel 204 as an example. The wheel forces are shown at the point of contact between the right front wheel 204 and the ground. Forces on the tires due to the road surface include a longitudinal tire force (F). xtotal ), a tire lateral force (F ytotal ) and a tire normal force (F ztotal These forces are responsible for generating a torque on the wheel, which is converted into a rack force.

[0037] The longitudinal force F on the tire xtotal is described in terms of force components, as shown in Eq. (1): Fxtotal=(Ftirex−Frolling)cos(δw)−Ftireysin(δw) where F tirex a road contact force on the tire in the longitudinal direction, F tirey The road contact force on the tire in the lateral direction is F rolling the force generated by rolling resistance, and δ w The wheel angle (RWA) is the rolling resistance. The rolling resistance is described in Eq. (2): Frolling=−frg min(1,vx)sign(vx) where f r the frictional force is, v x where g is the longitudinal speed of the vehicle and g is the acceleration due to gravity.

[0038] The tire lateral force F ytotal is described in terms of force components, as shown in Eq. (3): Fytotal=Ftireycos(δw)+(Ftirex−Frolling)sin(δw)

[0039] The tire normal force F ztotalis described in terms of force components, as shown in Eq. (4): Fztotal=Nfx2+ZgNfxayLfg where Z g the height of the vehicle's center of mass relative to the ground is, a y The lateral acceleration of the vehicle is g, the acceleration due to gravity is L f the axis length is and N fx given in Eq. (5): Nfx=mgXrXr+Xf−maxZgXr+Xf where X r The longitudinal distance between the center of mass and the rear axle is X f the longitudinal distance between the center of mass and the front axle is, a x where is the longitudinal acceleration of the vehicle and m is the mass of the vehicle.

[0040] Forces on the rack can be determined once the externally exerted wheel forces have been calculated. A resistance force F rackcan be calculated from a resistance torque about the steering axis of the right front wheel 204 (which runs along the length L of the right steering lever 404), as shown in Eq. (6): Frack=TtotalL where T total The total resistance torque is the torque generated around the steering axis. The total resistance torque T total can be decomposed into its torque components, as shown in Eq. (7): Ttotal=Txtotal+Tytotal+Tztotal

[0041] The x-axis torque component T xtotal refers to the longitudinal force T on the tire xtotal , as shown in Eq. (8): Txtotal=Fxtotalcos(τ)[rkpcos(γ)+Rnomsin(γ)] where τ is a caster angle of the wheel, γ is a kingpin angle, r kp a kingpin radius and R nom The nominal radius of the tire is [missing information]. The y-axis torque component T [missing information]. ytotal is shown in Eq. (9): Tytotal=Fytotalcos(τ)[t cos(τ)+Rnomsin(τ)] where t is the static offset of the wheel. The z-axis torque component T ztotal is shown in Eq. (10): Tztotal=Fztotalsin(γ)cos(τ)sin(δw)[cos(τ)(rkp+Rnomsin(τ))]

[0042] Fig. Figure 5 is a diagram 500 of a system architecture for calculating rack forces and subsequently providing a feedback torque. The system architecture includes a first set of modules 502 for performing a first procedure for calculating rack forces using forces on the wheels, and a second set of modules 504 for performing a second procedure for calculating rack forces using signals from the wheel actuator 312. The first set of modules 502 includes a rack force estimation module 506 for a right wheel, a rack force estimation module 508 for a left wheel, and a dynamics estimation module 510. The rack force estimation module 506 for the right wheel calculates an estimate of the rack force for the right wheel using tire forces measured at the right front wheel 204.The rack force estimation module 508 for the left wheel calculates an estimate of the rack force for the left wheel using tire forces measured at the left front wheel 202. Calculations in these modules use data from sensors 512, which include the inertial measurement unit (IMU) 220, tire force sensors 222, a wheel angle sensor 224, and a speedometer 226. The data is provided to the estimation modules in a temporal sequence or over several time steps of a selected time interval. Thus, each module calculates a temporal sequence of forces and provides this sequence to the dynamic estimation module 510. The dynamic estimation module 510 then provides an initial estimate of the rack force F̂. rl based on the estimate for the right wheel and the estimate for the left wheel. The first estimate F̂ rI It can be a temporal sequence or a temporal vector.

[0043] The second set of modules 504 receives signals (e.g. current, pulses, etc.) from the impeller actuator 312 and calculates a second estimate of the rack force F̂ rII based on these signals.

[0044] A switching module 516 performs a switching step 518. The switching module 516 receives the first estimate of the rack force F̂ rI from the dynamic estimation module 510 and the second estimate of the rack force F̂ rII from the RWA-based estimator 514. The mediation module 516 determines whether the first estimate F̂ rI the rack force and / or the second estimate F̂ rII The rack force is valid. This can include determining whether the data used to calculate these estimated rack forces are valid, or whether an error occurs during the estimation of one or more of these forces. The mediation module 516 selects between the initial estimate of the rack force F̂rI and the second estimate of the rack force F̂ rII based on the validity of the input data and gives a mediated rack force F̂ rarb to the handwheel actuator 310. The handwheel actuator 310 then exerts a feedback torque on the steering rod, which mediates the rack force F̂ rarb indicates.

[0045] The switching module 516 also transmits the switched rack force F̂ arb to additional modules that operate with the controller 306 and include a steering control module 520, a steering estimation module 522, and a steering diagnostics module 524. The steering control module 520 uses the mediated rack force F̂ rarbto control the rack in a manner that counteracts the rack force. The steering estimation module 522 controls the feedback torque feeling at the steering wheel 216. The steering diagnostic module 524 monitors the rack force to determine the suitability of steering operations. For example, the steering diagnostic module 524 can determine whether the rack force is within a range that allows continued operation of the vehicle or whether corrective action is required.

[0046] Referring to the rack force estimation of the first set of Module 502, the rack force can be estimated by updating a state equation over several time steps. x[k] represents an estimate of the rack force at time step k and is calculated from state measurements corresponding to time step k. The rack force is updated to the next time step k + 1. x[k+1]=x[k]+Δt(Kx[k]−xdes[k]) where Δt is a difference between time steps, K is the system dynamics control factor, and x des [k] is a ground-truth estimate of the rack force at time step k. Eq. (11) can be rewritten as shown in Eq. (12): x[k+1]=Ax[k]+Bu[k] where x[k]=Fr[k] A=[1+ΔtK] a system matrix and B=−ΔtI1∗1 is an input matrix. The input u[k] is given, as shown in Eq. (17): u[k]=1L(Fxtotalcos(τ)[rkp cos(γ)+Rnomsin(γ)]+Fytotalcos(γ)[t cos(τ)+Rnomsin(τ)]+Tztotal)

[0047] Fig. Figure 6 is a graph 600 that shows illustrative estimates of rack forces. Time is shown along the abscissa in seconds (s), and the rack force is shown along the ordinate in newtons (N). A first curve 602 shows a time evolution of the first estimate of the rack force F̂ rIA second curve 604 shows a time evolution of the second estimate of the rack force F̂ rII At approximately t = 5.5 seconds, a fault occurs in the impeller actuator 312. The fault lasts approximately 15.5 seconds. Thus, the second curve 604 shows a fault line that does not coincide with the first curve 602. During this fault, the switching module 516 can select the first estimate F̂ rI a rack force (the first curve 602) as the mediated rack force F̂ rarb to use. Otherwise, the second estimate F̂ will be used. rII the rack force as the mediated rack force F̂ rarb used.

[0048] Fig. Figure 7 is a flowchart 700 of a mediation process for the estimated rack forces. The procedure begins in Box 702. In Box 704, a check is performed on input signals used in the calculations for the first estimate of the rack force F̂. rIThe test detects the occurrence of any errors in the input signals and / or a reduction in the quality of the initial estimate of the rack force F̂. rI If any errors have occurred, the procedure proceeds to Box 706. Otherwise, the procedure proceeds to Box 712. Box 712 is a mediation process. The mediation process is carried out using the first estimate of the rack force (F̂). rI ) carried out, which is estimated using the first set of modules 502. And the second estimate of the rack force (F̂ rII ), which is estimated using the second set of modules 504.

[0049] Box 706 performs a check on input signals used to make the second estimate of the rack force F̂ rIito calculate. The test detects the occurrence of any errors in the input signals and / or a reduction in the quality of the second estimate of the rack force F̂. rII If any errors have occurred, the procedure proceeds to Box 708. Box 708 provides a signal to a Controller 306 to indicate the unavailability of the rack force estimate. The Controller 306 can then take a corrective action based on the missing rack force estimate.

[0050] Returning to box 706, if there is no error in calculating the second estimate of the rack force F̂ rII The second estimate of the rack force for box 710 is provided. In box 710, the rack force estimates are compared to determine a relationship between them. Between the first estimate of the rack force F̂ rIand the second estimate of the rack force F̂ rII A Mahala-Nobis distance is calculated. The Mahala-Nobis distance is calculated as shown in Eq. (18): T=12(F^rI−F^rIi)TC−1(F^rI−F^rIi) where T is the Mahala-Nobis distance and C is the sum of variance / covariance matrices related to the two estimates of rack forces. The Mahala-Nobis distance is compared to a threshold value to determine a relationship between the estimates.

[0051] If T >= T u (where T u (a calibratable threshold), the estimates are coherent and the procedure proceeds to Box 708. Otherwise (T < T uIf the estimates are inconsistent, the procedure proceeds to Box 712. In Box 712, mediation is performed. The first and second rack force estimates are mediated based on mediation logic. During mediation, the second rack force estimate (calculated from the RWA signals) has priority over the first rack force estimate (calculated using tire forces). Thus, the second rack force estimate is chosen if no error or deterioration is detected in the calculation of the second estimate (using an RWA signal). If an error occurs in the second estimate, the first estimate is used. The procedure ends in Box 714.

[0052] The terms "a" and "an" do not denote a limit on the number of elements, but rather indicate the presence of at least one of the referenced element. The term "or" means "and / or" unless clearly indicated otherwise by context. A reference to "an aspect" in the application text means that a specific element (e.g., a feature, a structure, a step, or a property) described in connection with that aspect is contained in at least one aspect described therein and may or may not be present in other aspects. It should also be understood that the described elements in the various aspects may be combined in any suitable manner.

[0053] When an element, such as a layer, a thin layer, an area, or a substrate, is described as "attached" to another element, it may be located directly adjacent to that element, or there may be intervening elements. Conversely, when an element is described as "directly adjacent" to another element, there are no intervening elements.

[0054] Unless otherwise specified herein, all testing standards shall be the most recent valid standard as of the filing date of this application or, if priority is claimed, as of the filing date of the earliest priority application in which the testing standard appears.

[0055] Unless otherwise defined, technical and scientific terms used herein have the same meaning as would normally be understood by a person skilled in the field to which this disclosure belongs.

[0056] While the disclosure described above has been described with reference to exemplary embodiments, those skilled in the art will understand that various modifications can be made and elements can be replaced by their equivalents without altering its scope. Furthermore, many adaptations can be made to fit a particular situation or material to the instructions given in the disclosure without deviating from its essential scope. Therefore, it is intended that the present disclosure is not limited to the specific embodiments disclosed, but includes all embodiments that fall within its scope. legend

[0057] In the drawing figures, N stands for no and Y for yes.

Claims

[1] Method of operating a vehicle comprising: Obtaining a measurement of a dynamic parameter of the vehicle that is related to a force on a rack of the vehicle, wherein the rack is coupled to a left wheel and / or a right wheel; Determining an initial estimate of a rack force resulting from the force, based on the measurement of the dynamic parameter; Obtaining a second estimate of the rack force based on a signal from an impeller actuator coupled to the rack; Selecting a mediated rack force from the first estimate of the rack force and the second estimate of the rack force, and Activating a handwheel actuator coupled to the vehicle's steering wheel, based on the mediated rack force, to generate a feedback torque at the steering wheel. [2] Method according to claim 1, wherein the dynamic parameter comprises: (i) a force applied externally to a tire and / or (ii) an acceleration obtained from an inertial measurement unit (IMU); and / or (iii) a wheel angle and / or (iv) a longitudinal speed of the vehicle. [3] The method of claim 1, further comprising determining an error in: (i) the measurement of the dynamic parameter used to calculate the first estimate; and / or (ii) the signal from the impeller actuator used to calculate the second estimate. [4] Method according to claim 3, further comprising selecting the second estimate as the mediated rack force if no error is found in the signal from the impeller actuator. [5] Method according to claim 1, wherein the first estimation of the rack force and / or the second estimation of the rack force comprise a temporal sequence of forces. [6] System for operating a vehicle, comprising: a rack and pinion coupled to a left wheel and / or a right wheel; a sensor for obtaining a measurement of a dynamic parameter of the vehicle that is related to a force on the rack; and a processor configured to: Determining an initial estimate of a rack force resulting from the force, based on the measurement of the dynamic parameter; Obtaining a second estimate of the rack force based on a signal from an impeller actuator coupled to the rack; Selecting a mediated rack force from the first estimate of the rack force and the second estimate of the rack force, and Activating a handwheel actuator coupled to the vehicle's steering wheel, based on the mediated rack force, to generate a feedback torque at the steering wheel. [7] System according to claim 6, wherein the dynamic parameter comprises: (i) a force applied externally to a tire and / or (ii) an acceleration obtained from an inertial measurement unit (IMU); and / or (iii) a wheel angle and / or (iv) a longitudinal speed of the vehicle. [8] System according to claim 6, wherein the processor is further configured to determine an error in: (i) the measurement of the dynamic parameter used to calculate the first estimate; and / or (ii) the signal from the impeller actuator used to calculate the second estimate. [9] System according to claim 8, wherein the processor is further configured to select the second estimate as the mediated rack force if no error is found in the signal from the impeller actuator. [10] System according to claim 6, wherein the first estimate of the rack force and / or the second estimate of the rack force comprise a temporal sequence of forces.

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