METHOD AND SYSTEM FOR DETERMINING OPERATING PERFORMANCE PARAMETERS OF A DEVICE

Abstract

A method of determining operational performance parameters of a device (e.g., of a vehicle) with device mounted sensors and computer-implemented models. Further, a system, such as a virtual sensor applied to a device, such as a vehicle, for determining operational performance parameters of the device is provided. The system includes device mounted sensors and at least one processing unit configured to execute the computer-implemented method to generate an output parameter set. Measured data may be combined, and calculated parameters may be provided to a Kalman-filter to enable virtual sensing of unobservable parameters.

Claims

1. A method of determining operational performance parameters of a device with device mounted sensors and computer-implemented models, the method being computer-implemented and comprising: measuring a first parameter set during operation of the device using the device mounted sensors; providing a computer-implemented supplemental model and determining a second parameter set by the computer-implemented supplemental model; combining parameters of the first parameter set with at least one selected parameter of the second parameter set, such that a hybrid parameter set is obtained; providing the parameters of the hybrid parameter set to a Kalman-Filter-module; predicting, by the Kalman-Filter-module, a third parameter set by a second model being equivalent to the hybrid parameter set regarding the respective parameter types; comparing, by the Kalman-Filter-module, the parameters of the hybrid parameter set and the third parameter set; estimating, by the Kalman-Filter-module, an output parameter set; determining a deviation between respectively one distinct parameter of the first parameter set and an equivalent parameter of the second parameter set; providing a correlation between deviation values and covariance values for at least one parameter of the third parameter set; determining a covariance value from the correlation based on the determined deviation; and forwarding the covariance value to the Kalman-Filter-module for estimating the output parameter set.

2. The method of claim 1, wherein the device is a vehicle, and wherein the at least one selected parameter is a vehicle side slip angle.

3. The method of claim 1, wherein the parameter sets respectively comprise a lateral velocity, longitudinal velocity, yaw rate, lateral acceleration, front cornering stiffness, rear cornering stiffness, or any combination thereof, and wherein the Kalman-Filter-module is an extended Kalman-filter.

4. The method of claim 1, wherein an input to the supplemental model, the second model, or the first model and the second model, respectively, is a longitudinal acceleration, a steering angle, or the longitudinal acceleration and the steering angle.

5. The method of claim 1, wherein supplemental model is of a linear type, and wherein the second model is of a non-linear type.

6. The method of claim 1, wherein the one distinct parameter for determination of the covariance value is a yaw rate, and the covariance value determined from the correlation based on the determined deviation is forwarded to the Kalman filter as a covariance of a cornering stiffness of a vehicle tire of the vehicle, and wherein the correlation provides a lower covariance value in case of a lower deviation and a higher covariance value in case of a higher deviation.

7. The method of claim 1, further comprising: displaying at least one parameter of the output parameter set or a modified parameter based on the output parameter set on a display to a user.

8. A system for determining operational performance parameters of a device, the system comprising: device mounted sensors; and at least one processing unit configured to generate an output parameter set, the at least one processing unit being configured to generate the output parameter set comprising the at least one processing unit being configured to: measure a first parameter set during operation of the device using the device mounted sensors; provide a computer-implemented supplemental model and determine a second parameter set by the computer-implemented supplemental model; combine parameters of the first parameter set with at least one selected parameter of the second parameter set, such that a hybrid parameter set is obtained; provide the parameters of the hybrid parameter set to a Kalman-Filter-module; predict, by the Kalman-Filter-module, a third parameter set by a second model being equivalent to the hybrid parameter set regarding the respective parameter types; compare, by the Kalman-Filter-module, the parameters of the hybrid parameter set and the third parameter set; estimate, by the Kalman-Filter-module, an output parameter set; determine a deviation between respectively one distinct parameter of the first parameter set and an equivalent parameter of the second parameter set; provide a correlation between deviation values and covariance values for at least one parameter of the third parameter set; determine a covariance value from the correlation based on the determined deviation; and forward the covariance value to the Kalman-Filter-module for estimating the output parameter set.

9. The system of claim 8, further comprising a display configured to display at least one parameter of the output parameter set or a modified parameter based on the output parameter set to a user.

10. The system of claim 8, wherein the device is a vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 shows a schematic diagram illustrating method acts according to an embodiment and a system according to an embodiment as a virtual sensor.

[0030] The illustration in the drawings is in schematic form. In different figures, similar or identical parameters may be provided with the same reference signs.

DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 shows a schematic illustration of method acts according to the present embodiments as well as a system for carrying out the method. The system is a virtual sensor. FIG. 1 shows the method applied to a device DVC (e.g., a vehicle VCL), in which the method according to the present embodiments may be incorporated. A measuring [act a] of the first parameter set PS1 during operation of the vehicle VCL is performed using sensors SNS. The vehicle VCL receives a steering angle at a steering wheel and a longitudinal acceleration a.sub.x as an input IPT from a user, respectively, from an engine of the car. The steering angle may be obtained by measuring the angle at the steering wheel and dividing the measured angle by a known ratio. The longitudinal acceleration a.sub.x may be obtained by accelerometers. This input IPT is forwarded to a computer-implemented supplemental model MD1 for determining a second parameter set PS2 [act b].

[0032] The supplemental model MD1 is a linear model. The supplemental model MD1 receives a virtual sideslip angle .sub.lin, which may be considered a virtual measurement, obtained by integrating over time the linear supplemental model MD1, assuming that under small angle assumption for a sideslip angle

[00001]${}_{\mathrm{lin}}=\frac{v_{y\mathrm{lin}}}{\mathrm{v\_x}}$

may be applied, with [0033] v.sub.y:=lateral velocity, [0034] v.sub.x:=longitudinal velocity.

[0035] The supplemental model MD1 may be formulated as follows:

[00002]$\{\begin{array}{c}{\stackrel{.}{v}}_{y\mathrm{lin}}=\frac{-2.Math.\left(\stackrel{\_}{C_f}+\stackrel{\_}{C_r}\right)}{m.Math.v_x}{v}_{y\mathrm{lin}}-\left(\frac{2.Math.\left(\stackrel{\_}{C_f}.Math.l_f-\stackrel{\_}{C_r}.Math.l_r\right)}{m.Math.v_x}+v_x\right){\stackrel{.}{}}_{\mathrm{lin}}+\frac{2.Math.\stackrel{\_}{C_f}}{m}\\ {\stackrel{.Math.}{}}_{\mathrm{lin}}=\frac{-2.Math.\left(\stackrel{\_}{C_f}.Math.l_f-\stackrel{\_}{C_r}.Math.l_r\right)}{I_{\mathrm{zz}}.Math.v_x}{v}_{y\mathrm{lin}}-\frac{2.Math.\left(\stackrel{\_}{C_f}.Math.l_f^2+\stackrel{\_}{C_r}.Math.l_r^2\right)}{I_{\mathrm{zz}}.Math.v_x}{\stackrel{.}{}}_{\mathrm{lin}}+\frac{2.Math.\stackrel{\_}{C_f}.Math.l_f}{I_{\mathrm{zz}}}\end{array}$

where u=[v.sub.x, ].sup.T is the input vector of the supplemental model MD1 (e.g., originating from input IPT: steering angle , longitudinal acceleration a.sub.x), and C.sub.f and C.sub.r are front and rear cornering stiffnesses, respectively, assumed in this model to be constant.

[0036] Further, this supplemental model MD1 refers to: [0037] {dot over ()}.sub.lin Yaw rate [0038] l.sub.f, l.sub.r distance between the center of gravity and the front and rear axles respectively [0039] m Vehicle mass [0040] I.sub.zz Vehicle yaw inertia.

[0041] In the next act (c), parameters of the first parameter set PS1 with at least one selected parameter SPS (e.g., pin) of the second parameter set PS2 are combined, obtaining a hybrid parameter set PSH. This hybrid parameter set PSH includes measured quantities, and at least one calculated quantity is considered as a virtual sensor measurement.

[0042] During the subsequent act (d), the parameters of the hybrid parameter set PSH are provided to a Kalman-Filter-module EKF.

[0043] The Kalman-Filter-module EKF predicts a third parameter set PS3 by a second model MD2 being equivalent to the hybrid parameter set PSH regarding the respective parameter types within act (e). Here, the Kalman-Filter-module EKF is an extended Kalman filter employing a single-track model coupled with an adaptive linear tire model, resulting in the set of state equations:

[00003]$\{\begin{array}{c}\stackrel{.}{v_y}=\frac{-2\left(C_f+C_r\right)}{m.Math.v_x}{v}_y-\left(\frac{2\left(C_f.Math.l_f-C_r.Math.l_r\right)}{m.Math.v_x}+v_x\right)\stackrel{.}{}+\frac{2.Math.C_f}{m}\\ \stackrel{.Math.}{}=\frac{-2\left(C_f.Math.l_f-C_r.Math.l_r\right)}{I_{\mathrm{zz}}.Math.v_x}{v}_y-\frac{2\left(C_f.Math.l_f^2+C_r.Math.l_r^2\right)}{I_{\mathrm{zz}}.Math.v_x}\stackrel{.}{}+\frac{2.Math.C_f.Math.l_f}{I_{\mathrm{zz}}}\\ \stackrel{.}{v_x}=a_x+v_y.Math.\stackrel{.}{}\\ \stackrel{.}{C_f}=0\\ \stackrel{.}{C_r}=0\end{array}$

[0044] x=[v.sub.y, {dot over ()}, v.sub.x, C.sub.f, C.sub.r].sup.T is the Kalman-filter-state-vector, and u=[a.sub.x, ].sup.T is the input vector with a meaning of the symbols as explained above.

[0045] The cornering stiffness values C.sub.f, C.sub.r are modeled with a random walk model to consider the non-linear behavior of the tire even at low levels of lateral acceleration (e.g., as in the on-center driving condition).

[0046] The initial output equation set of the Kalman-Filter-module EKF is:

[00004]$\{\begin{array}{c}\stackrel{.}{}=\stackrel{.}{}\\ a_y=\frac{-2.Math.\left(C_f+C_r\right)}{m.Math.v_x}{v}_y-\frac{2.Math.\left(l_f.Math.C_f-l_r.Math.C_r\right)}{m.Math.v_x}\stackrel{.}{}+\frac{2.Math.C_f}{m}\\ v_x=v_x\end{array}$

[0047] The final output equation of the Kalman-Filter-module EKF is obtained by augmenting this equation with the virtual measurement of the sideslip angle .sub.lin, which was obtained from the supplemental model MD1 (e.g., by integrating over time the above referenced linear model). The final equations result as:

[00005]$\{\begin{array}{c}\stackrel{.}{}=\stackrel{.}{}\\ a_y=\frac{-2.Math.\left(C_f+C_r\right)}{m.Math.v_x}{v}_y-\frac{2.Math.\left(l_f.Math.C_f-l_r.Math.C_r\right)}{m.Math.v_x}\stackrel{.}{}+\frac{2.Math.C_f}{m}\\ v_x=v_x\\ {}_{\mathrm{lin}}=\frac{v_{y\mathrm{lin}}}{v_x}\end{array}$

where y=[{dot over ()}, a.sub.y, v.sub.x, .sub.lin] is the output vector including quantities as explained above.

[0048] The virtual measurement of the sideslip angle .sub.lin provides a reliable reference during straight driving, when the cornering stiffnesses are basically unobservable. Further, the virtual measurement of the sideslip angle .sub.lin provides an additional reference for the lateral velocity, which is very difficult to measure (e.g., at low levels of lateral acceleration).

[0049] In method act (f), the Kalman-Filter-module EKF compares the parameters of the hybrid parameter set PSH and the third parameter set PS3. This is illustrated in FIG. 1 by determination of a difference DIF.

[0050] In act (g), the extended Kalman-Filter-module EKF estimates an output parameter set PSO by a Kalman-Filter-output-module EKF-OTP. The estimation is done in a known manner as a linear quadratic estimation LQE. The linear quadratic estimation LQE is an algorithm using the measurements including the history of measurements. These measurements may include statistical noise and other inaccuracies. The Kalman-Filter-module EKF produces estimates of the state variables that are likely to be more accurate than those based on single measurements alone. The Kalman-Filter-module EKF estimates a joint probability distribution over the variables for each timeframe.

[0051] Using a virtual reference such as .sup.lin, as a result of a simplified model (e.g., supplemental model MD1), may correctly represent the actual behavior of the vehicle in certain operating conditions but may also lead to errors and limitations during others.

[0052] FIG. 1 shows additional acts to cope with this issue respectively to increase accuracy by: (i) determining a deviation DVT between respectively one distinct parameter DCP, DCP1 of the first parameter set PS1 and the equivalent parameter DCP, DCP2 of the second parameter set PS2; (ii) providing a correlation CVL between the deviation DVT values and covariance values COV for at least one parameter of the third parameter set PS3; (iii) determining a covariance value COV from the correlation CVC based on the determined deviation DVT; and (iv) forwarding the covariance value COV to the Kalman-Filter-module EKF for estimating the output parameter set PSO.

[0053] As illustrated in FIG. 1, a covariance module CVM provides covariance values COV based on a predetermined correlation.

[0054] The deviation DVT is a measure of non-linearity determining whether the linear supplemental model MD1 is reliable at each time step. This is done here, as:

DVT(N)=|{dot over ()}.sub.meas(N){dot over ()}.sub.lin(N)|

[0055] The deviation DVT value is then used to adapt covariance values COV for at least one parameter of the third parameter set PS3 (e.g., the covariance values of the cornering stiffnesses, Q.sub.C.sub.f and Q.sub.C.sub.r and of the virtual sideslip angle measurement R.sub..sub.lin). The covariances COV are used as tuning parameters to adjust the final estimator performance according to the trust placed in either the model or the measure.

[0056] In one embodiment, the correlation CVL between the deviation DVT values and covariance values COV may provide a lower covariance value in case of a lower deviation and a higher covariance value in case of a higher deviation. In detail, the following ruling may be applied: [0057] {dot over ()}.sub.meas{dot over ()}.sub.lin.fwdarw.DVT is small: the tire is behaving linearly. In this case, [0058] Q.sub.C.sub.f, Q.sub.C.sub.r are set to low values since under linear tire behavior the cornering stiffnesses do no need to be adapter [0059] R.sub..sub.lin is set to a low value since .sub.lin accurately predicts the vehicle behavior [0060] {dot over ()}.sub.meas{dot over ()}.sub.lin.fwdarw.DVT is large: the tire is behaving in a non-linear way. In this case, [0061] Q.sub.C.sub.f, Q.sub.C.sub.r are set to high values since the cornering stiffnesses values are not reliable in this condition and need to be adapted [0062] R.sub..sub.lin is set to a high value since .sub.lin is no longer an accurate estimate of the vehicle sideslip angle [0063] {dot over ()}.sub.meas={dot over ()}.sub.lin.fwdarw.DVT=0: this occurs in straight driving, where no lateral excitation is present. In this case, [0064] Q.sub.C.sub.f, Q.sub.C.sub.r are set to zero to stabilize the estimator and avoid drifting of the cornering stiffnesses [0065] R.sub..sub.lin is set to a low value since .sub.lin accurately predicts the vehicle behavior during straight driving.

[0066] The System SYS shown in FIG. 1 includes at least one processing unit CPU configured to execute the computer-implemented method according to the present embodiments to generate the output parameter set PSO. The System SYS further includes a display DSP for displaying at least one parameter of the output parameter set PSO or a modified parameter based on the output parameter set PSO on a display DSP to a user USR.

[0067] Although the present invention has been described in detail with reference to the embodiments, it is to be understood that the present invention is not limited by the disclosed examples but by the scope defined by the claims, and that numerous additional modifications and variations may be made thereto by a person skilled in the art without departing from the scope of the invention defined by the independent claims.

[0068] The use of a or an throughout this application does not exclude a plurality, and comprising does not exclude other steps or parameters. Also, parameters described in association with different embodiments may be combined. Reference signs in the claims should not be construed as limiting the scope of the claims.

[0069] The elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent. Such new combinations are to be understood as forming a part of the present specification.

[0070] While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications can be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.