Method for controlling electrical machines in low-efficiency operation

Abstract

A method (20) for controlling at least one electric machine (11) of a vehicle (100) is disclosed, wherein an efficiency-optimized torque map and a trimmed torque map are determined or provided (21) by a pulse inverter (12) of the electric machine (11), the efficiency-optimized torque map and the trimmed torque map are received by a control unit (22) and taken into account (23) when determining an operating strategy of the at least one electric machine (11). Furthermore, an arrangement (10) and a vehicle (100) are disclosed.

Description

[0001] The invention relates to a method for controlling at least one electric motor of a vehicle. Furthermore, the invention relates to an arrangement and a vehicle with an arrangement.

[0002] The efficiency of electric drives in vehicles is constantly being optimized with considerable effort. This aims to reduce the power losses of the electric drive. Using a technique called map trimming, electric drives or machines can also be operated at maximum power loss, for example, to modify torque limits. Operation at maximum power loss is known as low-efficiency operation. Map trimming can also achieve increased deceleration in generator mode. The activation of this operating state for increased deceleration is typically selected automatically within the electric machine's control system based on battery current limits, without intervention from a higher-level control unit.Another possible way to activate the characteristic map trimming is by means of an externally specified operating state. The pulse inverter then sends the torque potentials to a higher-level control unit.

[0003] DE 10 2021 131 845 A1 describes a method for situationally increasing the preset electrical pull-out torque limits of the traction current inverter module. An inverter control strategy is selected by a control unit based on a series of vehicle-specific inputs.

[0004] US patent 2023 / 0219426 A1 discloses a method for operating an electric drive. The possible torque range of the drive is extended by deviations from the drive's maximum efficiency. WO 2021 / 216228A1 also describes a method for adjusting the torque of an electric drive in a manner deviating from operating the drive at its maximum efficiency.

[0005] In the solutions already known, the overarching control unit has no knowledge of the possible torques of the electric machine during low-efficiency operation.

[0006] DE 103 01 531 A1 discloses a device and a method for operating an electric machine of a vehicle. Depending on requirements, a torque control variable and a voltage control variable are defined to control the electric machine.

[0007] DE 10 2011 119 207 A1 describes a method for controlling at least two electric motors in a vehicle. The respective electric motors are controlled within a defined target current, and it is checked whether the sum of the target currents exceeds a limit value of the traction battery.

[0008] In DE 10 2022 104 909 A1 a method for determining and displaying the torque of an electric drive is described.

[0009] From DE 10 2021 119 537 A1 a method for controlling an electric drive system of an electrically powered vehicle during a recuperation process is known.

[0010] DE 10 2016 207 183 A1 discloses a method and a control device for shifting a transmission in a motor vehicle.

[0011] DE 10 2023 104 692 A1 describes an electrically operated powertrain of a vehicle. If required, the thermal power loss of the powertrain can be specifically increased in order to supply it to the traction battery and / or the vehicle interior.

[0012] The object of the present invention is to provide a method by which the inefficient operation of an electric machine is used to relieve the friction brake of a vehicle. According to the invention, this object is achieved by a method with the features of claim 1, an arrangement with the features of claim 7, and a vehicle with the features of claim 8. Advantageous embodiments and further developments are described in the dependent claims.

[0013] The method according to the invention serves to control at least one electric machine of a vehicle, wherein an efficiency-optimized torque map and a trimmed torque map are determined or provided by a pulse inverter of the electric machine. The efficiency-optimized torque map can be used by the pulse inverter to operate the at least one electric machine at maximum efficiency. The trimmed torque map exhibits, for example, inconsistencies in the timing of the control of the electric machine. By controlling the electric machine based on the trimmed torque map, the electric machine can be operated with a reduction in efficiency.The torques achieved when controlling the electric machine using the efficiency-optimized torque map and the trimmed torque map can be the same. However, using the trimmed torque map allows for a significantly higher braking torque from the electric machine in generator mode. In drive mode, the electric machine can generate higher heat output at the same torque due to the increased power losses resulting from the lower efficiency.

[0014] The torque maps can be presented as multiple two-dimensional diagrams or as three-dimensional diagrams. In particular, the resulting torques in the torque maps can be determined by a magnetizing current (I). d ) and from a moment-forming current (I qThe torque curves depend on various factors, including the total current required to operate the electric machine. Furthermore, other parameters, such as the speed of the electric machine, the temperature of the rotor and stator, and similar factors, can be included in the torque curves.

[0015] The efficiency-optimized torque map and the trimmed torque map, or individual possible torque potentials from the torque maps (e.g., for the current operating state, current speed of the electric machine, and the like), are provided by the pulse inverter and received by a control unit. The control unit can preferably be configured as a higher-level control unit than the pulse inverter. When determining an operating strategy for the at least one electric machine, the control unit takes both received torque maps into account.

[0016] According to a further aspect of the invention, an arrangement is provided which is configured to carry out the method according to the invention. The arrangement comprises at least one electric machine, a pulse inverter, and a control unit.

[0017] According to a further aspect of the invention, a vehicle is provided which has an arrangement according to the invention. The at least one electric machine can be configured as a traction machine of the vehicle and convert a requested torque into propulsion or a requested braking torque into deceleration of the vehicle.

[0018] The pulse inverter can determine the torque based on the current operating point of the electric machine and the assigned current limit using torque characteristic maps. Depending on requirements, either the trimmed torque characteristic map or the efficiency-optimized torque characteristic map can be used to determine or adjust the torque of the electric machine.

[0019] The modified torque map, which depends on the magnetizing current and the torque-generating current, allows, for example, more braking torque to be provided in generator mode at the same charging current limit. This results in lower efficiency compared to efficiency-optimized operation. The additional braking torque generated above the charging current limit can thus be converted into losses in the form of heat. This effect allows more braking torque to be provided by at least one electric drive, thereby relieving the vehicle's friction brakes.

[0020] In one embodiment, within the framework of the determined operating strategy, the control unit generates control commands to activate the at least one electric machine via the pulse inverter with the trimmed torque map when the control unit detects heat generation and / or an increase in braking torque by the at least one electric machine. The vehicle's at least one electric machine with the pulse inverter can send the additional braking torque potentials resulting from the adverse operating mode to the higher-level control unit using the trimmed torque map. The higher-level control unit can then request this (trimmed) operating point via a target torque specification and thus, for example, set a wider range of possible braking torques by the electric machine.

[0021] Electric machines can also be controlled by the trimmed torque map in such a way that they generate maximum power loss at the same torque. For example, inefficient points in the current distribution are used on the torque iso-curves of the torque map. This low-efficiency operation can be used, for example, to provide heat energy for interior heating and / or battery heating.

[0022] According to another embodiment, the control unit, within the framework of the determined operating strategy, defines a target torque based on the efficiency-optimized torque map or the trimmed torque map and transmits this to the pulse inverter. The pulse inverter then sets the target torque for the at least one electric machine.

[0023] In generator mode, the at least one electric machine is driven against the set target torque by a drive force. The electric machine generates a current, which is measured by the pulse inverter. The target torque is adjusted based on the trimmed torque map if the current generated by the electric machine exceeds a current limit. This current limit can be dynamically or situationally provided to the pulse inverter by the control unit. Alternatively or additionally, the current limit can be determined by the operating parameters of the vehicle's traction battery. This enables automated compensation that prevents overcharging of the traction battery and reduces the load on the vehicle's friction brakes.

[0024] According to another embodiment, the pulse inverter transmits information to the control unit when switching from a target torque set according to the efficiency-optimized torque map to a target torque set according to the trimmed torque map. If the allocated current limit is exceeded, the pulse inverter can automatically switch the electric machine to the low-efficiency mode with the trimmed torque map. The control unit is notified of this by the pulse inverter.

[0025] According to a further embodiment, the control unit takes into account the information about the use of the modified torque map when determining the operating strategy of the at least one electric machine. This measure allows the control unit to consider the switching to the so-called low-efficiency operation of the electric machine during further data processing. For example, the changed operating mode of the electric machine can be incorporated into the vehicle's power balance, the control unit can perform all-wheel distribution of the braking torque, and so on.

[0026] According to a further embodiment, a requested braking torque of the vehicle is distributed by the control unit between a braking torque generated by at least one friction brake and a braking torque generated by at least one electric machine operating in generator mode. The control unit transmits a target torque to the pulse inverter for generating the braking torque by the at least one electric machine, thereby minimizing the braking torque generated by the at least one friction brake. This can be achieved, in particular, by extending the possible braking torques of the electric machine due to the trimmed torque map. By minimizing the load on the friction brake, more efficient braking with less brake dust and less wear can be achieved. Thus, the braking potential of the electric machine, made possible by the trimmed torque, can be optimally utilized.

[0027] The invention is schematically illustrated with reference to embodiments in the drawings and is further described with reference to the drawings. It shows: Fig. 1 A schematic side view of a vehicle with an arrangement according to an embodiment of the invention. Fig. 2 a schematic flowchart to illustrate a process according to an embodiment of the invention.

[0028] Elements and components with identical or similar constructive or functional characteristics are provided with the same reference symbols across all figures.

[0029] In Fig. Figure 1 shows a schematic side view of a vehicle 100 with an arrangement 10 according to an embodiment of the invention. The arrangement is configured to carry out a method 20 which is Fig. Figure 2 illustrates the arrangement 10, which comprises at least one electric machine 11, one pulse inverter 12, and one control unit 13. Furthermore, at least one friction brake 14 is provided. The friction brake 14 is shown by way of example in the form of a disc brake.

[0030] In the illustrated embodiment, an electric machine 11 is provided, which serves to drive or decelerate the vehicle 100. The electrical energy for driving the electric machine 11 is supplied by a traction battery 15. In generator mode, the electric machine 11 can convert the vehicle's kinetic energy into electrical energy, thereby generating a braking torque.

[0031] As part of determining an operating strategy for the vehicle 100, the control unit 13 determines what proportion of a requested braking torque of the vehicle 100 is distributed to the electric machine 11 in generator operation and what proportion of the requested braking torque is distributed to the at least one friction brake 14 of the vehicle 100.

[0032] The Fig. Figure 2 shows a schematic flowchart to illustrate a method 20 according to an embodiment of the invention. The method 20 serves to control at least one electric machine 11 of a vehicle 100. By way of example, reference is made to the vehicle 100 in Fig. 1 taken.

[0033] In step 21 of the process 20, an efficiency-optimized torque map and a trimmed torque map of a pulse inverter 12 of the electric machine 11 are determined or provided. This can be done as part of a factory calibration or determined during operation using measurements. Depending on the configuration, instead of two different torque maps, an extended torque map with an efficiency-optimized torque range and with a trimmed torque range can also be determined and / or provided.

[0034] The modified torque map or torque range allows a greater torque potential of the electric machine 11 to be provided to the control unit 13. This torque is provided by the pulse inverter 12 and received by the control unit 13 22.

[0035] According to a further step 23 of the procedure 20, when determining an operating strategy for the at least one electric machine 11 by the control unit 13, the two received torque maps or torque ranges are taken into account. This allows the control unit 13 to specify a target torque for a braking effect or a driving effect of the electric machine 11 24.

[0036] The pulse inverter 12 can determine the torque using torque maps based on the current operating point of the electric machine 11 and an assigned current limit for charging the traction battery 15. Depending on requirements, either the trimmed torque map or the efficiency-optimized torque map can be used to determine or adjust the torque of the electric machine. The target torque is set using the trimmed torque map 25 when the current generated by the electric machine exceeds a current limit. The current limit can be dynamically or situationally provided to the pulse inverter by the control unit. Otherwise, 26 the efficiency-optimized torque map or an efficiency-optimized operating point within the torque map of the electric machine 11 is used to generate a braking effect by the electric machine 11.

[0037] The corresponding automatic setting of the pulse inverter 12 is communicated to the control unit in a further step 27 of the procedure 20. The information as to whether the electric machine 11 is operated in an efficiency-optimized range or in a low-efficiency range can be further processed by the control unit 13 within the framework of the operating strategy of the vehicle 100 28. REFERENCE MARK LIST: 100 vehicles 10 Arrangement 11 electric machine 12 pulse inverters 13 Control unit 14 Friction brake 15 traction batteries 20 procedures 21 Measuring or providing possible torques 22 Receiving possible torques 23 Determining an operating strategy 24. Specifying a target torque 25 Setting the target torque in a low-efficiency operation 26 Setting the target torque in an efficiency-optimized operation 27. Informing the control unit 28 Processing of information by the control unit

Claims

[1] Method (20) for controlling at least one electric machine (11) of a vehicle (100), wherein an efficiency-optimized torque map and a trimmed torque map are determined or provided (21) by a pulse inverter (12) of the electric machine (11), wherein the efficiency-optimized torque map and the trimmed torque map are received (22) by a control unit (13) and taken into account (23) when determining an operating strategy of the at least one electric machine (11). [2] Method according to claim 1, wherein, within the framework of the determined operating strategy, the control unit (13) generates control commands to control the at least one electric machine (11) by the pulse inverter (12) with the trimmed torque map when heat generation and / or an increase in braking torque by the at least one electric machine (11) is detected by the control unit (13). [3] Method according to claim 1 or 2, wherein the control unit (13) determines a target torque based on the efficiency-optimized torque map or the trimmed torque map within the framework of the determined operating strategy and transmits (24) to the pulse inverter (12), wherein the pulse inverter (12) sets the target torque at the at least one electric machine (11), wherein in generator operation of the at least one electric machine (11) a current is generated by a drive of the at least one electric machine (11) against the set target torque and is measured by the pulse inverter (12), wherein a target torque is set (25) based on the trimmed torque map if the generated current exceeds a current limit. [4] Method according to claim 3, wherein a switching from a target torque set on the basis of the efficiency-optimized torque map (26) to a target torque set on the basis of the trimmed torque map (25) is transmitted by the pulse inverter (12) in the form of information to the control unit (13) (27). [5] Method according to claim 4, wherein the information (27) about the use of the trimmed torque map is taken into account (28) by the control unit (13) when determining the operating strategy of the at least one electric machine (11). [6] Method according to any one of claims 1 to 5, wherein a requested braking torque of the vehicle (100) is distributed by the control unit (11) to a braking torque generated by at least one friction brake (14) and to a braking torque generated by at least one electric machine (11) switched to generator operation, wherein the control unit (13) transmits a target torque to the pulse inverter (12) for generating the braking torque by the at least one electric machine (11), by which a braking torque generated by the at least one friction brake (14) is minimized. [7] Arrangement (10) which is configured to carry out a method (20) according to one of the preceding claims, wherein the arrangement (10) comprises at least one electric machine (11), a pulse inverter (12) and a control unit (13). [8] Vehicle (100) which has an arrangement (10) according to claim 7.

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