Active damping control for an electric vehicle or hybrid vehicle

Abstract

The invention relates to a method (30) for the active damping control for an electric vehicle or hybrid vehicle having an electric motor drive element (4), comprising the steps of receiving a current target torque value (tq.sub.ElmDes) of the electric motor drive element (4), determining a current rotational angle value (.sub.ElmAct) of the electric motor drive element (4), and determining a current damping torque value (tq.sub.Dmp), characterized in that the current damping torque value (tq.sub.Dmp) is determined using a reduced drive train model (rTSM).

Claims

1. A method (30) for active damping control for an electric vehicle or hybrid vehicle with an electric motor drive element, comprising obtaining a current target torque value (tq.sub.E1mDes) of the electric motor drive element (4); determining a current angle of rotation value (.sub.ElmAct) of the electric motor drive element (4); determining, by a controller, a current damping torque value (tq.sub.Dmp), determining, by the controller, a current drive torque value (tq.sub.ElmAct) for controlling the electric motor drive element (4) from the difference of the current target torque value (tq.sub.E1mDes) and the current damping torque value (tq.sub.Dmp) as tq.sub.ElmAct=tq.sub.ElmDestq.sub.Dmp; and controlling the electric motor drive element (4) based on the current drive torque value (tq.sub.ElmAct); wherein the current damping torque value (tq.sub.Dmp) is determined using a reduced drive train model (rDTM), and is limited to a maximum value (tq.sub.Dmpmax), and is set to zero below an activation threshold (tq.sub.Dmpmin).

2. The method as claimed in claim 1, further comprising the determination of an estimated rotation angle value (.sub.E1mEst) from the current target torque value (tq.sub.E1mDes) and the current rotation angle value (.sub.E1mAct) using the reduced drive train model (rDTM); and controlling the electric motor drive element using the estimated rotation angle value (.sub.E1mEst).

3. The method as claimed in claim 1, further comprising the determination, using the reduced drive train model (rDTM), of an oscillation characteristic (.sub.Osc) from the angular speed (.sub.1) of the rotor of the electric motor drive element and from the angular speed (.sub.2) of an equivalent vehicle mass as w.sub.Osc=.sub.1.sub.2 from $\begin{array}{cc}{\stackrel{.}{}}_1\left(t\right)=-\frac{c}{J_1}.Math.\left({}_1\left(t\right)-{}_2\left(t\right)\right)-\frac{d}{J_1}.Math.\left({}_1\left(t\right)-{}_2\left(t\right)\right)+\frac{1}{J_1}.Math.u\left(t\right)& \mathrm{Equation}1\\ {\stackrel{.}{}}_2\left(t\right)=\frac{c}{J_2}.Math.\left({}_1\left(t\right)-{}_2\left(t\right)\right)-\frac{d}{J_2}.Math.\left({}_1\left(t\right)-{}_2\left(t\right)\right)-\frac{1}{J_2}.Math.t{q}_{\mathrm{Last}}\left(t\right)& \mathrm{Equation}2\end{array}$ with J.sub.1: moment of inertia of the electric motor drive element; J.sub.2: moment of inertia of the vehicle; C: equivalent stiffness of the vehicle drive train according to rDTM; d: equivalent damping constant of the vehicle drive train according to rDTM; u: system stimulation/torque of the electric motor drive element; tq.sub.Last load torque of the vehicle; {acute over ()}.sub.1: angular acceleration of the rotor of the electric motor drive element; {acute over ()}.sub.2: angular acceleration of the equivalent vehicle mass; .sub.1: angular speed/revolution rate of the rotor of the electric motor drive element .sub.2: angular speed/revolution rate of the equivalent vehicle mass; .sub.1: current angle of rotation of the rotor of the electric motor drive element; and .sub.2: current angle of rotation of the rotor of the equivalent vehicle mass.

4. The method as claimed in claim 3, wherein the current damping torque value (tq.sub.Dmp) is determined from the oscillation characteristic (.sub.Osc) using a factor k.sub.Dmp as tq.sub.Dmp=k.sub.Dmp*.sub.Osc.

5. The method as claimed in claim 4, wherein the factor k.sub.Dmp is a non-constant factor.

6. The method as claimed in claim 5, wherein the factor k.sub.Dmp has a functional dependency of at least one value from the group consisting of the speed of the vehicle v(k.sub.Dmp=f(v.sub.Fahrzeug)), the wheel revolution rate n(k.sub.Dmp=f(n.sub.Rad)) or the rotor speed of the electric motor drive element (k.sub.Dmp=f(.sub.1)) and the angular speed .sub.2 of an equivalent vehicle mass(k.sub.Dmp=f(.sub.2)).

7. A controller for a vehicle, arranged to perform the method (30) according to claim 1.

8. A vehicle comprising a controller as claimed in claim 7.

9. The method as claimed in claim 1, wherein the current damping torque value (tq.sub.Dmp) is limited to a maximum value (tq.sub.Dmpmax).

10. The method as claimed in claim 1, wherein the current damping torque value (tq.sub.Dmp) is set to zero below an activation threshold (tq.sub.Dmpmin).

11. The controller for a vehicle as claimed in claim 7, wherein the vehicle is an electric vehicle or hybrid vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention are illustrated in the figures and explained in detail in the following description.

(2) In the figures

(3) FIGS. 1a, b show an exemplary oscillation characteristic of a drive train;

(4) FIG. 2 shows a model of a vehicle drive train according to the present invention;

(5) FIG. 3 shows an exemplary embodiment of a reduced drive train model rDTM according to the present invention; and

(6) FIG. 4 shows an exemplary process diagram of the method for active damping control according to the present invention

DETAILED DESCRIPTION

(7) FIG. 2 shows a model of a vehicle drive train according to the present invention.

(8) The modeled vehicle drive train 2 for a hybrid electric vehicle or an electric vehicle comprises an electric motor drive element 4, which is coupled to a gearbox 6 using a drive shaft 8. Starting from the gearbox 6, two drive wheels 12 are connected to the electric motor 4 via axle shafts 10 by way of example. A rotation of the electric motor 4 is thus transferred via the drive shaft 8, gearbox 6 and axle shafts 10 into a rotation of the drive wheels 12.

(9) Because of the transfer of the rotary motion from the electric motor drive element 4 to the drive wheels 12 using a plurality of intermediate elements, especially by means of their predominant elasticities and dampings, electric motor 4 can vibrate when driving the drive wheels 12.

(10) FIG. 3 shows an exemplary embodiment of a reduced drive train model rDTM according to the present invention, especially an equivalent circuit diagram or a reduced model using a reduced drive train model rDTM of FIG. 2.

(11) In the reduced model of FIG. 3 the rotation of the electric motor drive element 4 or its rotor rotation is transferred to the rotation of the vehicle 14, especially its drive wheels 12. An equivalent moment of inertia J.sub.2, which especially takes into account an equivalent vehicle mass, which ultimately transfers the vehicle mass to a rotation of the drive wheels 12, is used as the moment of inertia of the electric motor 4 J.sub.1, as the moment of inertia of the vehicle including all running resistances. Thus the drive or forward movement of the vehicle 14 can be converted into a rotation of the drive wheels 12, taking into account a corresponding equivalent vehicle mass.

(12) The connection of the electric motor drive element 4 to the drive wheels 12 or the vehicle 14 takes place in FIG. 3 using an equivalent elasticity of the drive train, therefore a mathematical model of the physical behavior of the drive train, especially the following elements: drive shaft 8, gearbox 6 and axle shafts 10 of the vehicle drive train 2 according to FIG. 2.

(13) The mathematical model of the drive train consists here of a mutually parallel spring element 16 and a damping element 18. The spring element 16 here has an equivalent stiffness c and the damping element 18 has an equivalent damping coefficient d.

(14) The electric motor drive element 4 uses a system stimulation u, e.g. the torque of the electric motor drive element 4. The moment of inertia of the vehicle J.sub.2 is affected by the load torque tq.sub.Last of the vehicle, e.g. friction. The angular acceleration .sub.1 of the rotor of the electric motor drive element 4 and .sub.2 the angular acceleration of the vehicle mass, converted to a rotary motion using the equivalent vehicle mass, can be represented respectively by the two following equations:

(15) $\begin{array}{cc}{\stackrel{.}{}}_1\left(t\right)=-\frac{c}{J_1}.Math.\left({}_1\left(t\right)-{}_2\left(t\right)\right)-\frac{d}{J_1}.Math.\left({}_1\left(t\right)-{}_2\left(t\right)\right)+\frac{1}{J_1}.Math.u\left(t\right)& \mathrm{Equation}1\\ {\stackrel{.}{}}_2\left(t\right)=\frac{c}{J_2}.Math.\left({}_1\left(t\right)-{}_2\left(t\right)\right)-\frac{d}{J_2}.Math.\left({}_1\left(t\right)-{}_2\left(t\right)\right)-\frac{1}{J_2}.Math.t{q}_{\mathrm{Last}}\left(t\right)& \mathrm{Equation}2\end{array}$

(16) where

(17) J.sub.1: moment of inertia of the electric motor drive element;

(18) J.sub.2: moment of inertia of the vehicle;

(19) c: equivalent stiffness of the vehicle drive train according to rDTM;

(20) d: equivalent damping coefficient of the vehicle drive train according to rDTM;

(21) u: system stimulation/torque of the electric motor drive element;

(22) tq.sub.Last: load torque of the vehicle;

(23) {acute over ()}.sub.1: angular acceleration of the rotor of the electric motor drive element;

(24) {acute over ()}.sub.2: angular acceleration of the equivalent vehicle mass;

(25) .sub.1: angular speed/revolution rate of the rotor of the electric motor drive element

(26) .sub.2: angular speed/revolution rate of the equivalent vehicle mass;

(27) .sub.1: current angle of rotation of the rotor of the electric motor drive element; and

(28) .sub.2: current angle of rotation of the rotor of the equivalent vehicle mass.

(29) .sub.1 corresponds here to the angular speed or revolution rate of the rotor of the electric motor drive element 4 and .sub.2 to the angular speed/revolution rate of the equivalent vehicle mass of the vehicle 14.

(30) 1 or 2 respectively form the angle of rotation of the rotor of the electric motor drive element 4 or the equivalent vehicle mass, related to the drive wheels 12.

(31) The oscillation characteristic .sub.Osc represents the difference of .sub.1 and .sub.2.

(32) Continuing to refer to FIG. 4, an exemplary process diagram of the method for active damping control according to the present invention is illustrated.

(33) Method 30 for active damping control for an electric vehicle or hybrid vehicle with an electric motor drive element uses a current target torque value tq.sub.ElmDes, which e.g. is specified by a driver of a vehicle using a gas pedal 20. A current damping torque value tq.sub.Dmp can be determined using the reduced drive train model rDTM according to FIG. 3 and taking account of the equivalent stiffness c of the vehicle drive train, the equivalent damping coefficient d of the vehicle drive train and the current angle of rotation of the machine .sub.ElmAct. The current angle of rotation .sub.ElmAct of the electric motor drive element 4 may be determined e.g. by a measurement on the electric motor drive element. .sub.ElmAct corresponds here to .sub.1 of equations 1 and 2.

(34) The target torque tq.sub.ElmDes corresponds here to u(t). In particular, the damping torque tq.sub.Dmp can be determined from .sub.Osc, thus as .sub.1.sub.2. Furthermore, tq.sub.Dmp especially represents .sub.Osc multiplied by the factor element k.sub.Dmp.

(35) Factor element k.sub.Dmp can initially be a constant factor as previously mentioned, but should especially be dynamically adapted to the speed of the vehicle v, a wheel revolution rate n.sub.Rad or a rotor revolution rate of the electric motor drive element 4 or else to the estimated revolution rate .sub.2 of the equivalent vehicle mass or should be dependent thereon.

(36) The damping moment of inertia tq.sub.Dmp can then be limited in its maximum value tq.sub.Dmpmax using a saturation block 22 and can have an activation threshold tq.sub.Dmpmin. A corresponding implementation of a curve profile between tq.sub.DmpEin and tq.sub.DmpAus of the saturation block is shown in FIG. 4.

(37) After the saturation block 22 the calculation of the delivered torque of the electric motor tq.sub.ElmAct takes place as tq.sub.ElmAct=tq.sub.ElmDestq.sub.DmpAus.

(38) The resulting torque of the electric motor drive element 4 is in turn coupled into the reduced drive train model of FIG. 3. A corresponding calculation can now be continued in its next iteration.

(39) At the same time the reduced drive train model provides the estimated angle of rotation .sub.ElmEst, which signal can be used instead of .sub.ElmAct as the signal for current regulation of the electric motor drive element 4. Because of the use of the angle of rotation .sub.2 compared to .sub.1 or .sub.2 compared to .sub.1, a directly compensated control of the electric motor drive element 4 takes place. The signal quality of the angle of rotation used for the regulation can generally be significantly improved by this compared to the angle of rotation .sub.ElmAct directly determined from a sensor.

(40) In particular, with the method of the present invention a speed of the vehicle v is not determined or used for calculation of a compensation torque, but rather a current revolution rate of the rotor of an electric motor drive element is used. As a result, speed-dependent parameterization of a drive control may be performed. Alternatively, an estimated revolution rate .sub.2 of the electric motor drive element 4 or of a drive wheel 12 can also be used.

(41) In addition it is determined that the method according to the invention does not intervene in the revolution rate control, but rather in the torque control. Thus success according to the invention can also be achieved when driving off from a stationary vehicle state. The oscillation characteristic is thus uniquely determined by a revolution rate signal or a bearing angle signal of an electric motor drive element 4 and especially not from a difference measurement between a target revolution rate and an actual revolution rate. The current control of an electric motor drive element 4 remains unaffected by this and does not have to be adapted. The only task of the current control is the adjustment of the torque tq.sub.ElmAct.