Method of verifying the operation of a motor propulsion plant fitted to an automotive vehicle and corresponding system

Abstract

A method and system for verifying operation of a motor propulsion plant fitted to an automotive vehicle with electric or hybrid traction, the motor propulsion plant including an electric motor including a permanent-magnet rotor. The method includes: a regulation of currents of a stator and a measurement of direct and quadratic components of the currents; an application, in a model of the electric motor linking control signals to the direct and quadratic components of the currents, of a change of variable in which X=Iq3+Id3, Y=Iq−Id; determination of minimum and maximum bounds for X and Y to deduce therefrom minimum and maximum bounds for Iq and Id; and a comparison between the measured direct and quadratic components of the currents and the minimum and maximum bounds for Iq and Id.

Claims

1. A method for verifying operation of a power train with which a motor vehicle with electric or hybrid drive is equipped, the power train including an electric motor including a permanent magnet rotor and a stator, the method comprising: regulating, via an electronic control unit, stator currents delivering control signals to the electric motor, the currents to be regulated and the control signals being expressed in a revolving reference frame including a direct axis and a quadratic axis; measuring, via the electronic control unit, the direct and quadratic components of the currents: applying, via the electronic control unit, in a model of the electric motor linking the control signals to the direct and quadratic components of the currents, a change of variable by computation of new variables X and Y according to relationships X=I.sub.q.sup.3+I.sub.d.sup.3 and Y=I.sub.q-I.sub.d, in which I.sub.d and I.sub.q respectively denote the direct component of the current and the quadratic component of the current; determining, via the electronic control unit, minimum and maximum bounds of the changed variables to deduce therefrom minimum and maximum bounds for the direct and quadratic components of the current; comparing, via the electronic control unit, between the measured direct and quadratic components the currents and the minimum and maximum bounds; and limiting, via the electronic control unit, use of the electric motor when one of the measured values is outside the determined bounds.

2. The method as claimed in claim 1, further comprising: measuring torque generated by the electric motor; computing minimum and maximum bounds for the torque from the minimum and maximum bounds for the quadratic component of the current; and comparing between the measured torque and the minimum and maximum bounds for the torque.

3. The method as claimed in claim 1, further comprising generating at least one signal if one of the measured values is outside the determined bounds.

4. A system for verifying operation of a power train with which a motor vehicle with electric or hybrid drive is equipped, the power train including an electric motor including a permanent magnet rotor and a stator, the vehicle including means configured to regulate stator currents delivering control signals to the electric motor, the currents to be regulated and the control signals being expressed in a revolving reference frame including a direct axis and a quadratic axis, and means configured to measure direct and quadratic components of the currents, the system comprising: an electronic control unit that is configured to apply, in a model of the electric motor linking the control signals to the direct and quadratic components of the currents, a change of variable by computation of new variables X and Y according to relationships X=I.sub.q.sup.3+I.sub.d.sup.3 and Y=I.sub.q-I.sub.d, in which I.sub.d and I.sub.q respectively denote the direct component of the current and the quadratic component of the current; determine minimum and maximum bounds for X and Y for deducing minimum and maximum bounds for the direct and quadratic components of the current; compare the measured direct and quadratic components of the currents and the minimum and maximum bounds; and limit use of the electric motor when one of the measured values is outside the determined bounds.

5. The system as claimed in claim 4, further comprising: means configured to compute minimum and maximum bounds for torque from the minimum and maximum bounds for the quadratic component of the current; and means for comparing a torque measured by means for measuring the torque of the vehicle and the minimum and maximum bounds for the torque.

6. The system as claimed in claim 4, further comprising means configured to generate at least one signal if one of the measured values is outside the determined bounds.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other aims, features and advantages of the invention will become apparent on reading the following description, given purely as a nonlimiting example, and with reference to the attached drawings in which:

(2) FIG. 1 schematically illustrates different steps of a method according to an implementation of the invention, and

(3) FIG. 2 schematically illustrates a system according to an embodiment of the invention.

DETAILED DESCRIPTION

(4) FIG. 1 schematically shows the different steps of a method PR for verifying the operation of a power train with which a motor vehicle with electric or hybrid drive is equipped. The power train of this vehicle can comprise an electric motor provided with a permanent magnet rotor and a stator.

(5) A first step E00 can be implemented in which the stator currents (or the torque) can be regulated to obtain control signals. These control signals can be expressed in the Park space and, for example, denoted V.sub.d (component on the direct axis) and V.sub.q (component on the quadrature axis). This regulation can be implemented by conventional means, for example by using a proportional-integral corrector or a proportional-integral-derivative corrector.

(6) The method can also comprise a measurement of the direct and quadratic components of the currents denoted I.sub.d (direct component) and I.sub.q (quadratic component) in the step E01. The step E01 can, as a variant, be implemented later in the method to implement a comparison with determined bounds.

(7) Concurrently with the step E01, a step E01′ can be implemented for measuring the torque denoted C.sub.em.

(8) A step E02 can then be implemented for generating a model of the electric motor linking the control signals to the direct and quadratic components of the currents. As a variant, the step E02 is implemented previously and the same model is used each time the method is implemented.

(9) It should be noted that, in the Park space, such a model corresponds to the following system of equations:

(10) $\begin{array}{cc}\{\begin{array}{c}{V}_d=R_s{I}_d+L_d{\stackrel{•}{I}}_d-{\omega }_r{L}_q{I}_q\\ V_d=R_s{I}_q+L_q{\stackrel{•}{I}}_q-{\omega }_r\left(L_d{I}_d+{\varphi }_f\right)\end{array}& \left(\mathrm{EQ}1\right)\end{array}$

(11) With R.sub.s being the equivalent resistance of the stator of the machine, L.sub.d and L.sub.q being the inductances on each axis, respectively direct and in quadrature, of the Park plane of the machine, ω.sub.r being the rotation speed of the magnetic field of the machine (i.e. the rotation speed of the rotor multiplied by the number of pairs of poles of the machine denoted p), and φ.sub.f being the flux generated by the rotor magnets.

(12) It should also be noted that the system of equations EQ1 is not cooperative. Also, for a machine in which L.sub.d and L.sub.q are equal, the following electromagnetic torque value C.sub.em is obtained:
C.sub.em=pΦ.sub.fI.sub.q  (EQ2)

(13) With p being the number of pairs of poles of the machine, and Φ.sub.f being the flux generated by the rotor magnets.

(14) In order to make the system of equations EQ1 cooperative, the variable changing step E03 can be implemented. In this step, the new variables can be denoted X and Y, with X=I.sub.q.sup.3+I.sub.d.sup.3 and Y=I.sub.q−I.sub.d. If U.sub.x and U.sub.y are used to denote the new control signals applied as input for the system, the following system of equations is obtained:

(15) $\hspace{1em}\begin{array}{cc}\{\begin{array}{c}\frac{3}{L_s}{U}_x=\frac{3}{L_s}\left(I_d^2{V}_d+I_q^2{V}_q\right)=\frac{3R_s}{L_s}X+\stackrel{.}{X}+3{\omega }_r{I}_q\left[I_d\left(I_q-I_d\right)+\frac{{\Phi }_f}{L_s}\right]\\ \frac{1}{L_s}{U}_y=\frac{1}{L_s}\left(-V_d+V_q\right)=\frac{R_s}{L_s}Y+\stackrel{.}{Y}+{\omega }_r\left[I_d+I_q+\frac{{\Phi }_f}{L_s}\right]\end{array}& \left(\mathrm{EQ}3\right)\end{array}$
With L.sub.s being the inductance on each axis q and d of the machine.

(16) This change of variable is implemented by deriving the expressions of X and Y to replace the values of I.sub.q and I.sub.d or their derivatives obtained by the system of equations EQ1.

(17) It can be noted that a cooperative system is obtained. Because of this, if min is used to denote the minimum bounds and max to denote the maximum bounds, and X.sup.+ and X.sup.− to denote the respectively maximum and minimum bounds for X and Y.sup.+ and Y.sup.− to denote the respectively maximum and minimum bounds for Y, the following system is obtained in a step E04:

(18) $\left(\mathrm{EQ}4\right)$$\{\begin{array}{c}\min \left(\frac{3}{L_s}{U}_x\right)=\min \left(\frac{3R_s}{L_s}\right)X^{-}+{\stackrel{.}{X}}^{-}+3{\omega }_r{I}_q{I}_d\left(I_q-I_d\right)+\min \left(3{\omega }_r{I}_q\frac{{\Phi }_f}{L_s}\right)\\ \min \left(\frac{1}{L_s}{U}_y\right)=\min \left(\frac{R_s}{L_s}\right)Y^{-}+{\stackrel{.}{Y}}^{-}+{\omega }_r\left(I_d+I_q\right)+\min \left({\omega }_r\frac{{\Phi }_f}{L_s}\right)\\ \max \left(\frac{3}{L_s}{U}_x\right)=\max \left(\frac{3R_s}{L_s}\right)X^{+}+{\stackrel{.}{X}}^{+}+3{\omega }_r{I}_q{I}_d\left(I_q-I_d\right)+\max \left(3{\omega }_r{I}_q\frac{{\Phi }_f}{L_s}\right)\\ \max \left(\frac{1}{L_s}{U}_y\right)=\max \left(\frac{R_s}{L_s}\right)Y^{+}+{\stackrel{.}{Y}}^{+}+{\omega }_r\left(I_d+I_q\right)+\max \left({\omega }_r\frac{{\Phi }_f}{L_s}\right)\end{array}$

(19) It should be noted that min(3/L.sub.s*U.sub.x)=max(3/L.sub.s)*U.sub.x if U.sub.x is negative, or min(3/L.sub.s)*U.sub.x if U.sub.x is positive.

(20) At each instant t after the initial instant t.sub.0, it is known that the measured values of X and Y (obtained from measurements of I.sub.d and I.sub.q) verify the following two equations:

(21) $\begin{array}{cc}\{\begin{array}{c}{X}^{-}\left(t\right)\le X\left(t\right)\le X^{+}\left(t\right)\\ Y^{-}\left(t\right)\le Y\left(t\right)\le Y^{+}\left(t\right)\end{array}& \left(\mathrm{EQ}5\right)\end{array}$

(22) Also, it should be noted that, in preliminary calibration steps, the minimum and maximum bounds of Rs, Ls, ω.sub.r and φ.sub.f can be determined. It is therefore possible to deduce the values of X.sup.+, X.sup.−, Y.sup.+ and Y.sup.− from the system EQ4.

(23) It is also possible to obtain the values of the maximum bounds (I.sub.d.sup.+ and I.sub.q.sup.+) and minimum bounds (I.sub.d.sup.− and I.sub.q.sup.−) by solving the following system:

(24) $\begin{array}{cc}\{\begin{array}{c}{X}^{-}={\left(I_q^{-}\right)}^3+{\left(I_d^{-}\right)}^3\\ Y^{-}=I_q^{-}-I_q^{+}\\ X^{+}={\left(I_q^{+}\right)}^3+{\left(I_d^{+}\right)}^3\\ Y^{+}=I_q^{+}-I_q^{-}\end{array}& \left(\mathrm{EQ}6\right)\end{array}$

(25) Also, with the formula of the equation EQ2, it is possible to obtain minimum and maximum bounds for the torque C.sub.em.

(26) The step E05 can then be implemented, in which the values measured previously in the steps E01 and E01′ are compared to the bounds obtained in the step E04.

(27) If it is concluded that one of the measurements is outside of the bounds corresponding to this measurement, a step E06 can be implemented to generate signals indicating the failure of the sensor.

(28) FIG. 2 shows a system SYS, for example embedded in a motor vehicle with electric or hybrid drive provided with a power train having a permanent magnet rotor.

(29) The system SYS can be incorporated in an electronic control unit of the vehicle or in other types of computers embedded in a vehicle. Also, the vehicle can comprise other means not represented in FIG. 2 but which communicates with the system SYS, for example means configured to regulate stator currents delivering control signals to the electric motor.

(30) The system SYS comprises means 1 configured to generate a model of the electric motor linking the control signals to the direct and quadratic components of the currents. The means 1 are configured to implement the step E02 described with reference to FIG. 1. As a variant, the system SYS does not comprise any means configured to generate a model of the electric motor linking the control signals to the direct and quadratic components of the currents, such a model having been generated previously.

(31) The system SYS also comprises means 2 configured to apply, in said model, a change of variable in which X=I.sub.q.sup.3+I.sub.d.sup.3, Y=I.sub.q−I.sub.d. In other words, the means 2 are configured to implement the step E03.

(32) The system SYS also comprises means 3 configured to determine minimum and maximum bounds for X and Y suitable for deducing minimum and maximum bounds for I.sub.q and I.sub.d (step E04) and means 4 configured to compare the measured direct and quadratic components of the currents and said minimum and maximum bounds for I.sub.q and I.sub.d (step E05).

(33) Preferentially, the system SYS comprises means 5 configured to generate at least one signal if one of the measured values is outside the determined bounds (step E06).

(34) The vehicle can also comprise means 6 for measuring, or sensors for sensing, the currents Id and Iq, and also means 7 for measuring the torque. The system SYS and the method PR make it possible to determine whether these sensors are operating.

(35) By virtue of the invention, it is possible to determine whether current sensors operate in any type of regime, dynamic or permanent. It is thus possible to limit the use of the electric motor.