Method for controlling two electric motors

Abstract

The disclosure relates to a method for controlling a first electric motor (M1) and a second electric motor (M2) of a wheel drive module, wherein the wheel drive module comprises a wheel (R) and a speed modulation gearbox (G), and wherein the wheel (R) is drivable about a wheel axis (A) jointly by the first and the second electric motors (M1, M2) by means of the speed modulation gearbox (G) and steerable about a steering axis (L) which is orthogonal to the wheel axis (A), wherein electrical control signals for controlling the first and second electric motors (M1, M2) are determined from wheel reference values which characterize the driving and/or the steering of the wheel (R).

Claims

1. A method for controlling a first electric motor (M1) and a second electric motor (M2) of a wheel drive module, wherein the wheel drive module comprises a wheel (R) and a speed modulation gearbox (G), and wherein the wheel (R) is drivable about a wheel axis (A) jointly by the first and the second electric motors (M1, M2) by means of the speed modulation gearbox (G) and steerable about a steering axis (L) which is orthogonal to the wheel axis (A), wherein electrical control signals for controlling the first and second electric motors (M1, M2) are determined from wheel reference values which characterize the driving and/or the steering of the wheel (R).

2. The method according to claim 1, wherein the wheel reference values are a wheel reference angle and a wheel reference rotational speed or a wheel reference speed or a wheel reference torque.

3. The method according to claim 2, wherein the wheel reference values are determined from a path to be traveled by the wheel (R) or by the wheel drive module and a speed of the wheel (R) or of the wheel drive module along the path, wherein the path takes into consideration the distance to be traveled and the course of the road.

4. The method according to claim 1, wherein, from the control signals for the first and second electric motors (M1, M2), by a respective motor control associated with the first or with the second electric motor (M1, M2), a motor reference rotational speed, a motor reference position or a motor reference torque is determined, and the respective electric motor (M1, M2) is controlled in order to achieve the motor reference rotational speed, the motor reference position or the motor reference torque.

5. The method according to claim 4, wherein the motor reference rotational speed of the respective electric motor (M1, M2) is determined from a first motor reference rotational speed for achieving a driving speed and from a second motor reference rotational speed for achieving a steering angle, so that:
motor reference rotational speed.sub.M1(t)=motor reference rotational speed.sub.Driving(t)motor +reference rotational speed.sub.Steering(t) and
motor reference rotational speed.sub.M2(t)=motor reference rotational speed.sub.Driving(t)−motor reference rotational speed.sub.Steering(t).

6. The method according to claim 5, wherein the motor reference rotational speed for achieving a driving speed for the first and the second electric motors (M1, M2) at an identical gear ratio of the speed modulation gearbox (G) for the first and second electric motors (M1, M2) is identical and is determined in particular from a wheel reference rotational speed of the wheel (R) and the gear ratio of the speed modulation gearbox (G), so that:
motor reference rotational speed.sub.Driving(t)=reference rotational speed(t).Math.gear ratio.sub.Driving

7. The method according to claim 5, wherein the motor reference rotational speed for achieving the steering angle for the second electric motor (M2), at identical gear ratio of the speed modulation gearbox (G) for the first and second electric motors (M1, M2), is the negative value of the motor reference rotational speed for achieving the steering angle for the first electric motor (M1), and the motor reference rotational speed for achieving the steering angle for the first electric motor (M1) is determined from a change of the wheel steering angle of the wheel (R) about the steering axis (L), so that:
motor reference rotational speed.sub.Steering(t)=motor reference rotational speedM1.sub.Steering(t)=−motor reference rotational speed.sub.M2Steering(t)=d wheel steering angle(t).Math.gear ratio.sub.Steering.Math.(2π.Math.TA.sup.−1)

8. The method according to the preceding claim 7, wherein the change of the wheel steering angle is obtained as follows:
d wheel steering angle(t)=wheel steering angle.sub.Reference(t+TA).Math.wheel steering angle.sub.Actual(t)with TA as call interval and wherein wheel steering angle.sub.Actual(t)=(motor position.sub.M1(t)−motor position.sub.M2(t))(2.Math.gear ratio.sub.Steering).

9. A wheel drive module comprising the wheel (R), the speed modulation gearbox (G) as well as the first electric motor (M1) and the second electric motor (M2), which are controlled by the method according to claim 1, wherein the first and the second electric motors (M1, M2) are designed to drive the wheel (R) jointly by means of the speed modulation gearbox (G) about a wheel axis (A) and to steer it about a steering axis (L) which is orthogonal to the wheel axis (A), the wheel drive module comprises a first motor electronics unit for controlling the first electric motor (M1) and a second motor electronics unit for controlling the second electric motor (M2) as well as a central electronics unit which is connected so as to enable a signal exchange with the first and second motor electronics units, and wherein the drive wheel module comprises a control logic for controlling the first and second electric motors (M1, M2) for driving the wheel (R) about the wheel axis (A) and for steering the wheel (R) about the steering axis (L), which is provided by the first and second motor electronics units, the central electronics unit, an application electronics unit, which is connected to the central electronics unit so as to enable a signal exchange, or which is provided jointly by central electronics unit and the first and second motor electronics units, wherein the control logic is designed to determine, from the wheel reference values, the electrical control signals for the first and second electric motors (M1, M2) and to transmit the control signals to the first and/or second electric motors (M1, M2).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other advantageous developments of the disclosure are characterized in the dependent claims and represented in further detail below together with the description of the preferred design of the disclosure in reference to the figures. In the figures:

(2) FIG. 1 shows a wheel driven by a first and a second electric motor by means of a speed modulation gearbox;

(3) FIG. 2 shows a diagrammatic representation of an implementation of the method for controlling a first and a second electric motor by a central electronics unit of the wheel drive module.

(4) The figures are diagrammatic examples. Identical reference numerals in the figures refer to identical functional and/or structural features.

DETAILED DESCRIPTION

(5) In FIG. 1, the wheel R, the first and second electric motors M1, M2 as well as the speed modulation gearbox G for driving and steering the wheel R by means of the two electric motors M1, M2 are represented. Here, by FIG. 1, only one possible design alternative of the drive of the wheel R about the wheel axis A and the steering axis L by the first and second electric motors M1, M2 is illustrated. For example, the wheel R can be arranged under the drive gear rings G3, G3′, or the electric motors M1, M2 can comprise another transmission to the drive gear rings G3, G3′ as well as another orientation. In the represented example, the speed modulation gearbox G comprises the pinions G1, G1′, the intermediate wheels G2, G2′, the drive gear rings G3, G3′ as well as the output gearwheel G4 and the output shaft G5. In addition, in other embodiment variants, the speed modulation gearbox G can also comprise additional components.

(6) The first and the second electric motors M1, M2 drive the first and the second drive gear rings G3, G3′. In the embodiment shown, the first electric motor M1 is arranged opposite the second electric motor M2, wherein the electric motors M1, M2 can each comprise a separate motor transmission. The electric motors M1, M2 are in each case connected via a motor shaft to a respective pinion G1, G1′.

(7) The first pinion G1 engages by means of its toothing in a toothing of a first intermediate gear G2 which engages by means of its toothing in a drive toothing of the first drive gear ring G3, so that, due to a rotation of the first pinion G1, the first drive gear ring G3, driven by the first electric motor M1, can be rotated about the rotation axis or steering axis L.

(8) Analogously, the same applies to the second drive gear ring G3′. The second pinion G1′ engages by means of its toothing in a toothing of a second intermediate gear G2′ which engages by means of its toothing in a drive toothing of the second drive gear ring G3′, whereby, by a rotation of the second pinion G1′, the second drive gear ring G3′, driven by the second electric motor M2, can be rotated about the rotation axis or steering axis L.

(9) Between the first and the second drive gear rings G3, G3′, an output gearwheel G4 is arranged, which engages by means of its toothing both in a toothing of the first drive gear ring G3 facing the output gearwheel G4 and also in a toothing of the second drive gear ring G3′ facing the output gearwheel G4. The rotation of the output gearwheel G4 (third rotation) is consequently brought about by the rotation of the first drive gear ring G3 (first rotation) and also by the rotation of the second drive gear ring G3′ (second rotation).

(10) From the output gearwheel G4, an output shaft G5 connected in a rotationally fixed manner to the output gearwheel G4 extends along a wheel axis A in the direction of the rotation axis or the steering axis L of the drive gear rings G3, G3′. On a side spaced from the output gearwheel G4 along the wheel axis A, the wheel R is connected in a rotationally fixed manner to the output shaft G5, whereby a rotation (third rotation) of the output gearwheel G4 is transmitted via the output shaft G5 to the wheel R. As represented in sections, the wheel R is accommodated between the first drive gear ring G3 and the second drive gear ring G3′, which are spaced apart along the rotation axis L thereof and define a wheel accommodation space between them. Both drive gear rings G3, G3′ comprise a ring opening extending along the rotation axis L through the respective drive gear ring G3, G3′. The wheel R extends at least on the side thereof which faces the bottom through the respective ring opening, whereby the wheel R substantially comprises five sections. A first section by means of which the wheel R is arranged between the drive gear rings, two second sections by means of which the wheel R is arranged in the ring openings of the drive gear rings G3, G3′, and two third sections by means of which the wheel R lies along the rotation axis L outside of the drive gear rings G3, G3′. The arrangement of the wheel R in the wheel accommodation space leads to three advantageous effects. The installation space of the wheel drive module is clearly reduced, since the wheel R, in a steering movement, does not need to rotate around the drive gear rings G3, G3′, and the possible steering angle is increased, since the wheel R can be rotated 360° in the drive gear rings G3, G3′ without the steering movement or rotation about the rotation axis L being limited by the intermediate gears G2, G2′. In addition, the wheel R is protected by the wheel drive module 1 or by the first and second drive gear rings G3, G3′ since they form a cage around the wheel R.

(11) The rotation direction of the first motor rM1 and the rotation direction of the second motor rm2, drawn in FIG. 1, are oriented with respect to one another such that the drive gear rings G3, G3′ in a pure driving movement perform a counter-rotation with respect to one another and as a result the wheel R is not rotated about the steering axis L.

(12) In FIG. 2, a portion of the wheel drive module is represented diagrammatically. By the drive of the wheel R about the steering axis L and the wheel axis A, a driving function X2 and a steering function X1 are provided on or by the wheel R. For the provision of the steering and driving function X1, X2 by means of the speed modulation gearbox G, said speed modulation gearbox is driven by the first and second electric motors M1, M2 by means of the first and second operative connection X31, X32.

(13) In an application case such as in the field of logistics, for example a transport carriage, the respective application comprises at least two and preferably four wheel drive modules. Thus, eight motors for driving and for steering the transport carriage have to be controlled by the control of such a transport carriage.

(14) In order to relieve the control of the transport carriage, it is therefore provided in the embodiment variant shown that the control 50 of the transport carriage transmits to each of its wheel drive modules the respective wheel reference steering angle φ.sub.R of the wheel R as well as the wheel reference rotational speed n.sub.R of the wheel R, for example, via a bus line.

(15) Here it is also advantageous that, for the control 50 of the application or the transport carriage, it is not important how the electric motors M1, M2 are controlled and whether only one electric motor contributes to the steering and only one electric motor contributes to the driving or whether both electric motors M1, M2 contribute to driving and steering.

(16) In the represented diagrammatic representation, the method for controlling the first and second electric motors M1, M2 is implemented by the central electronics unit 30. The input values, respectively the wheel reference steering angle φ.sub.R and the wheel reference rotational speed n.sub.R, are transmitted to the central electronics unit 30 and converted into a motor reference rotational speed of the first electric motor M1 (motor reference rotational speed.sub.M1) or n.sub.M1, as well as into a motor reference rotational speed of the second electric motor M2 (motor reference rotational speed.sub.M2) or n.sub.M2. The two motor reference rotational speeds nM1 and nM2 are transferred from the central electronics unit 30 to the respective motor electronics unit 10, 20 and the respective electric motor M1, M2 is controlled in order to achieve the respective motor reference rotational speed n.sub.M1, n.sub.M2 by them.