CONTROL UNIT FOR AN ELECTRIC VEHICLE WITH AN ELECTROMECHANICAL BRAKE UNIT, VEHICLE THEREWITH AND METHOD OF USE

Abstract

A control unit (56) for a vehicle (10) with an electric drive (12) and an electromechanically actuated brake unit (14) includes a high-voltage DC link (20) disconnectably connected to a first energy store (24) of the electric drive (12), a converter (18) connected to the high-voltage DC link (20) and operable bidirectionally, and an electric motor (16) connected to the converter (18) for driving a wheel (50) of the vehicle (10). A brake drive circuit (36) is connected to the high-voltage DC link (20), and another electric motor (34), is connected to the brake drive circuit (36). A function block (55) has an input (69) for receiving a voltage signal (68) indicative of the voltage of the high-voltage DC link (20), a first output (63) for outputting a converter drive signal (60), and a first closed-loop controller unit (66) for generating the converter drive signal (60).

Claims

1. A control unit (56) for a vehicle (10) having an electric drive (12) and an electromechanically actuated brake unit (14), wherein the electric drive (12) includes a high-voltage DC link (20) disconnectably connected to a first energy store (24) of the electric drive (12), a converter (18) connected to the high-voltage DC link (20) and operable bidirectionally, and an electric drive motor (16) connected to the converter (18) for driving a wheel (50) of the vehicle (10), the electric motor being operable in a generator mode, wherein the electromechanically actuated brake unit (14) includes a brake drive circuit (36) connected to the high-voltage DC link (20), and an electric brake motor (34) connected to the brake drive circuit (36), for actuating a brake of the vehicle (10), wherein the control unit comprises a function block (55), which includes: an input (69) for receiving a voltage signal (68) indicative of the voltage of the high-voltage DC link (20), a first output (63) for outputting a converter drive signal (60) for driving the converter (18), and a first closed-loop controller unit (66) for generating the converter drive signal (60) depending on the received voltage signal (68) and a predefined comparison value (70), in particular a setpoint voltage value.

2. The control unit (56) as claimed in claim 1, wherein the function block (55) additionally comprises: a second output (109) for outputting a DC-DC converter drive signal (108) for driving a DC-DC converter (46) connected between the high-voltage DC link (20) and a low-voltage DC link (48), and a second closed-loop controller unit (102) for generating the DC-DC converter drive signal (108) depending on the voltage signal (68) and on at least one of the comparison value (70) and a second comparison value (104).

3. The control unit (56) as claimed in claim 1, wherein the control unit (56) comprises a voltmeter (71) for measuring the voltage of the high-voltage DC link (20) to generate the voltage signal (68) therefrom and to supply the voltage signal (68) to the input (69) of the function block (55).

4. The control unit (56) as claimed in claim 1, wherein the control unit (56) comprises has a changeover switch (62) for switching over between a normal operating mode and an emergency operating mode, and the changeover switch (62) is configured to generate the converter drive signal (60) in the emergency operating mode depending on the received voltage signal (68) and the predefined comparison value (70) and in the normal operating mode depending on a torque request signal (64) received at a second input (67), for the electric drive (12).

5. A system for a vehicle (10), the system comprising the control unit (56) as claimed in claim 1 and the electric drive (12), wherein the electric drive (12) includes comprises: the high-voltage DC link (20) disconnectably connectable to the first energy store (24) of the electric drive (12), the converter (18) connected to the high-voltage DC link (20) and operable bidirectionally, and the electric drive motor (16) connected to the converter (18), for driving the wheel (50) of the vehicle (10), the electric motor being operable in the generator mode.

6. The system as claimed in claim 5, further comprising an electromechanically actuated brake unit (14) connected to the high-voltage DC link (20), wherein the electromechanically actuated brake unit (14) comprises: a brake drive circuit (36) connected to the high-voltage DC link (20), and an electric brake motor (34) connected to the brake drive circuit (36), for actuating a brake of the vehicle (10).

7. The system as claimed in claim 5, wherein the system comprises a first energy store (24) and a second energy store (42), wherein the first energy store (24) has a rated voltage corresponding at least to a multiple of a rated voltage of the second energy store (42), wherein the first energy store (24) is disconnectably connected to the high-voltage DC link (20), and the second energy store (42) is connected to a low-voltage DC link (48) or is part of the low-voltage DC link (48).

8. The system as claimed in claim 5, wherein the converter (18) of the electric drive (12) is a four-quadrant converter.

9. A vehicle (10) having a control unit (56) as claimed in claim 1, wherein the vehicle (10) is a utility vehicle, a heavy goods vehicle, a bus, a tractor, or a trailer.

10. A method for a vehicle (10) having an electric drive (12) and an electromechanically actuated brake unit (14), the method comprising the following steps: measuring (110) the voltage of a high-voltage DC link (20) of the electric drive (12) and transmitting a voltage signal (68) dependent on the voltage, to a control unit (56); and generating (112) a converter drive signal (60) for the electric drive (12) depending on the voltage signal (68) and a predefined comparison value (70) by a first closed-loop controller unit (66).

11. The method as claimed in claim 10, wherein the step of generating (112) the converter drive signal (60) (112) comprises: supplying (114) the voltage signal (68) of the high-voltage DC link (20) as an actual value to the first closed-loop controller unit (66), supplying (116) the predefined comparison value (70) as a setpoint value to the first closed-loop controller unit (66), and outputting (118) a manipulated variable (72) of the first closed-loop controller unit (66) as a converter drive signal (60).

12. The method as claimed in claim 10, wherein the method further comprises generating (120) a DC-DC converter drive signal (108), by performing the following steps: comparing (124) the voltage signal (68) with a threshold value or comparing a change over time with a change threshold value (104), and outputting (126) the DC-DC converter drive signal (108) only upon determining that the voltage signal (68) is below the threshold value or above a change threshold value.

13. The method as claimed in claim 10, further comprising the steps of: converting the converter drive signal (60) into a setpoint current variable (82) by a further closed-loop controller (76) depending on a present speed (78) of an electric drive motor (16), converting the setpoint current variable into a setpoint voltage (96) by a further closed-loop controller (84) depending on a current generated or taken up by the electric drive motor (16), and converting the setpoint voltage in a further unit (98) into a pulse-width-modulated signal (26, 100) for driving a converter (18).

14. A non-volatile computer memory storing a program code which causes a control device of a vehicle (10) to initiate the following method steps: measuring (110) the voltage of a high-voltage DC link (20) of an electric drive (12) and transmitting a voltage signal (68) dependent on the voltage, to a control unit (56); and generating (112) a converter drive signal (60) for an electric drive (12) depending on the voltage signal (68) and a predefined comparison value (70) by a first closed-loop controller unit (66).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In the drawings,

[0039] FIG. 1 shows a vehicle having an electric drive and an electromechanically actuated brake unit,

[0040] FIG. 2 shows the design of the driving of an electric drive in accordance with one exemplary embodiment,

[0041] FIG. 3 shows the design of the driving of an electric drive in accordance with a further exemplary embodiment, and

[0042] FIG. 4 shows steps in the method in accordance with one exemplary embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 shows a vehicle 10 having an electric drive 12 and an electromechanically actuated brake unit 14. The electric drive 12 comprises an electric motor 16, which is connected, via a converter 18, to a high-voltage DC link 20. The high-voltage DC link 20 is further electrically connected to a first energy store 24 via a switch disconnector 22. A substantially constant voltage for operating the electric motor 16 of the electric drive 12 is provided from the energy store 24 via the high-voltage DC link 20. Energy which is generated in the generator operating mode of the motor 16 can also be fed into the energy store 24 via the converter 18. The converter 18 of the electric drive 12 is driven depending on an electronic signal 26, which has been generated in a controller 28 from a converter drive signal. The electronic signal 26 is, for example, a pulse-width-modulated signal, a data signal (for example CAN) or an analog drive signal. The converter drive signal is likewise generated by the controller 28. In this case, in the normal operating mode of the vehicle 10, the converter drive signal and the electronic signal 26 resulting therefrom is generated by the controller 28 depending on a driver's desire to accelerate or brake. In order to communicate the driver's desire to the controller 28, in particular a brake pedal 30 and a gas pedal 32 are made available to the driver. A signal for accelerating or decelerating the vehicle can moreover, in accordance with a further exemplary embodiment not illustrated here, also originate from a driver assist system or a system for automated driving.

[0044] In the event of a desire to brake being expressed via the brake pedal 30, in addition the electromechanically actuated brake unit 14 is drivable via the controller 28 in order to provide additional braking power when the electric motor 16 of the electric drive 12 cannot provide this braking power in the generator operating mode. For this purpose, the electromechanically actuated brake unit 14 likewise has an electric motor 34, which is likewise connected to the high-voltage DC link 20 via a brake drive circuit 36, which is preferably likewise in the form of a converter. The brake drive circuit 36 is driven by the controller 28 by a brake request signal 40 when the brake unit 14 is required.

[0045] Correspondingly, energy is therefore supplied to the electric motor 16 of the electric drive 12 from the high-voltage DC link 20 via the converter 18 of the electric drive 12 depending on the signal 26 or, in the generator operating mode of the electric motor 16 of the electric drive 12, energy is fed into the high-voltage DC link 20 via the converter 18 of the electric drive 12. Likewise, the electric motor 34 of the electromechanically actuated brake unit 14 draws the energy for actuating friction brakes likewise from the high-voltage DC link 20.

[0046] Furthermore, the vehicle 10 comprises a vehicle battery 42, which serves the purpose of supplying energy to consumers 44 of the vehicle 10 which do not belong to the electric drive 12 or to the electromechanically actuated brake unit 14. Examples of such consumers 44 are the lighting of the vehicle 10 or the controller 28 itself. The vehicle battery 42 is connected to the high-voltage DC link 20 via a DC-DC converter 46. The vehicle battery 42 at the same time represents a low-voltage DC link 48.

[0047] In FIG. 1, the electric drive 12 and the electromechanically actuated brake unit 14 are only illustrated for one wheel 50 of the vehicle 10. This illustration is used for ease of understanding. Particularly preferably, an electromechanically actuated brake unit 14 is provided for each wheel 50, wherein the electric drive 12 can also have a plurality of electric motors 16, in each case for a plurality of wheels 50 of the vehicle 10 or in each case for driving an axle of the vehicle 10. Preferably, in the event that the electric drive 12 has a plurality of motors 16, each motor 16 has a converter 18, which is connected to the high-voltage DC link 20.

[0048] The controller 28 is illustrated by way of example in this figure and comprises a plurality of units, namely in particular a vehicle control device 52, a brake control device 54 and the control unit 56 according to the invention. The control unit 56 according to the invention is illustrated here as a separate unit but, in accordance with other exemplary embodiments, is also part of the vehicle control device 52 or the brake control device 54 or corresponds to the vehicle control device 52 or the brake control device 54. For improved clarity, the three mentioned units are combined here as controller 28.

[0049] FIG. 2 shows a more detailed illustration of part of the controller 28 from FIG. 1 and the design for driving the electric drive 12 in accordance with one exemplary embodiment. In particular, FIG. 2 shows a function block 55 of a control unit 56 in accordance with one exemplary embodiment of the invention for generating a converter drive signal 60. The converter drive signal 60 is output by a changeover switch 62 of the control unit 56 at a first output 63 of the control unit 56. The changeover switch 62 is used for switching over between a normal operating mode and an emergency operating mode. If the first energy store 24 is disconnected from the high-voltage DC link 20, the changeover switch 62 switches to the emergency operating mode. In this case, the converter drive signal 60 is generated by a first closed-loop controller 66 and is output at the first output 63 via the changeover switch 62. The converter drive signal 60 is generated by the closed-loop controller 66 by virtue of a voltage signal 68 of the present voltage of the high-voltage DC link 20 being supplied as actual value via a first input 69 to the first closed-loop controller 66. The voltage is measured by means of a voltmeter 71. In addition, a comparison value 70 is preset as setpoint value for the first closed-loop controller 66. The first closed-loop controller 66 generates herefrom a manipulated variable 72, which corresponds to the converter drive signal 60 and is output via the changeover switch 62. In the normal operating mode, the converter drive signal 60 corresponds to a torque request signal 64 which is received from the control unit 56 and which is received via a second input 67 and passed through the changeover switch 62.

[0050] The converter drive signal 60 is not used directly for driving the converter 18 of the electric drive 12 but is now subjected to further signal processing in a further function block 73. This signal processing in accordance with the present example is not part of the control unit 56, but part of a further control unit 74 of the electric drive 12, which control unit 74 is likewise contained in the controller 28. This further control unit 74 is, however, also embodied as part of the control unit 56 according to the invention, in accordance with further exemplary embodiments (not illustrated here). The control unit 56 according to the invention together with the further control unit 74 of the electric drive 12 is part of the brake control device 54 in accordance with a further exemplary embodiment. In the further signal processing illustrated here as further control unit 74, the converter drive signal 60 is first supplied to a further closed-loop controller 76, to which a present speed 78 of the electric motor 16 is likewise supplied by a sensor 80 arranged at the electric motor 16.

[0051] The converter drive signal 60, which preferably corresponds to a torque value, is converted by the further closed-loop controller 76 into a drive current 82 depending on the speed 78. The further closed-loop controller 76 is necessary since the drive current 82 is dependent on the present speed 78 for a desired torque. In a further closed-loop controller 84, the drive current 82, which is supplied as setpoint value, is then compared with the aid of an actual current 86, which is likewise supplied to the closed-loop controller 84 and which is being taken up or output at that time by the electric motor 16. For this purpose, the actual current signal 86 is generated by virtue of, first, the current being measured over three phases 88, which are supplied to the electric motor 16, by an ammeter 90, and this current being converted into the actual current signal 86 via a Clarke transformer 92 taking into consideration an angle of rotation 94 determined likewise by the position sensor 80. From this, a DC voltage signal 96 is generated, which acts as manipulated variable for the converter 18. In a further unit 98, a DQ transformation is implemented, and the transformed signal is converted into an electronic signal 26 in the form of a pulse-width-modulated signal 100, likewise taking into consideration the angle of rotation 94. The pulse-width-modulated signal 100 is used for directly driving the converter 18.

[0052] FIG. 3 shows substantially the elements from FIG. 2, wherein here, in addition, a second closed-loop controller unit 102 is arranged in the function block 55. The second closed-loop controller unit 102 is provided a further comparison value 104 as setpoint value. Furthermore, the second closed-loop controller unit 102 receives the voltage signal 68 as actual value, which, however, is derived via a differentiating element 106 prior to being supplied to the second closed-loop controller unit 102, in order to generate, depending on the change in this signal, a DC-DC converter drive signal 108 by means of the second closed-loop controller unit 102 as manipulated variable. The DC-DC converter drive signal 108 is output via a second output 109, then used to drive the DC-DC converter 46, which is connected to the high-voltage DC link 20 on one side and to a vehicle battery 42 on the other side.

[0053] FIG. 4 shows the steps in a method in accordance with one exemplary embodiment. The method comprises a step 110, in which a voltage of a high-voltage DC link 20 is measured. In step 112, a converter drive signal 60 for an electric drive 12 is then generated depending on the voltage signal 68 generated from the measured voltage by a first closed-loop controller unit 66 depending on a predefined comparison value 70. For this purpose, step 112 comprises the subordinate step 114, in which the voltage signal 68 is supplied as actual value to the first closed-loop controller unit 66. In addition, in subordinate step 116, a predefined comparison value 70 is supplied as setpoint value to the first closed-loop controller 66. In the further subordinate step 118, a manipulated variable 72 of the first closed-loop controller unit 66 is output as converter drive signal 60. In a further step 120, a DC-DC converter drive signal 108 is generated by virtue of the voltage signal being supplied, in a subordinate step 122, to a second closed-loop controller unit 102. In a further subordinate step 124, a further predefined comparison value 104 is compared with the voltage signal. In a further step 126, which is subordinate to step 120, the DC-DC converter drive signal 108 is output.