Method for regulating an electric motor

Abstract

In a method for regulating an electric motor (15), the method comprises a weighting factor determination process (P2), in which weighting factor values ​​(4) are continuously determined, an integration process (P3), in which the weighting factor values ​​(4) are added up so that an integration value (5) is formed, and a regulating process (P4), in which the electric motor (15) is regulated when the integration value (5) is above a threshold value (6).

Description

Technical FieldThe invention relates to a method for regulating an electric motor according to the preamble of claim 1.Prior ArtElectric vehicles typically include one or more electric motors that drive the electric vehicles. Such electric motors are loaded to varying extents during travel. In particular, different torques are requested by the electric motors at different times, in particular by the fact that the driver actuates the accelerator pedal of a vehicle to a greater or lesser extent.In the case of electric motors overloads are always also possible, for example because the electric motors retrieve torques that are too high for too long, which can lead, for example, to excessive heating of the electric motors. Therefore, it is typically necessary, during the operation of electric vehicles, to regulate the electric motors which have been subjected to excessive loads, so that they can only provide certain reduced torques, at least for a certain period of time, in particular until they have recovered from a previous high load.The shutdown of electric motors in electric vehicles is not simple, however. In particular, the shutdown should take place neither too early nor too late. Known systems for regulating electric motors also have the disadvantage that they are felt unpleasant by vehicle users at least temporarily, for example because they regulate too abruptly or too strongly.DE 10 2008 002 623 A1 discloses a method and a control device for monitoring and limiting the torque in a drive train of a road motor vehicle.GENERAL DESCRIPTION OF THE INVENTIONThe object of the invention is to eliminate or at least reduce the disadvantages of the prior art.The object is achieved by a method for regulating down an electric motor, wherein the method comprises: a weighting factor determination process in the scope of which weighting factor values are determined continuously, an integration process in the scope of which the weighting factor values are added up, such that an integration value is formed, and a regulating down process in the scope of which the electric motor is regulated down if the integration value is above a threshold value.The term "weighting factor value" is understood here to mean a value which indicates how strongly an electric motor is claimed at a specific point in time. By continuously calculating weighting factor values, which are typically not constant during the course of the method, but continuously change during the operation of the electric motor, and adding up these weighting factor values within the scope of the integration process, it is achieved that the integration value corresponds, so to speak, to a "memory" for the stressing of the electric motor. In this "memory", stresses of different magnitude are "stored" by the adding-up, with strong stresses typically being weighted more strongly than stresses of less magnitude. In typical embodiments, the integration value changes continuously, i.e. it can be below the threshold value, for example, at specific times, then above the threshold value for a specific period of time and can then fall below the threshold value again, in particular if a phase of weak stress on the electric motor follows after exceeding the threshold value, within the scope of which for example negative weighting factor values are determined, which then successively decrease the integration value again. In typical embodiments, in the context of the weighting factor determination process, a current motor torque of the electric motor is compared with a continuous torque value, wherein a positive weighting factor is determined if the current motor torque is greater than the continuous torque value and wherein a negative weighting factor value is determined if the current motor torque is less than the continuous torque value. In typical embodiments, the steady state torque value is a torque that the electric motor can deliver for a duration of about 30 minutes without being overloaded. The term "approximately" is typically to be understood in this description in such a way that it describes a tolerance of at most + / - 20%, preferably at most + / - 15%, advantageously at most + / - 10%. By determining the weighting factor values in this way, loads above the continuous torque value result in an increase in the integration value and thus bring the electric motor closer to a shutdown, whereas loads below the continuous torque value result in a reduction in the integration value, whereby the electric motor gradually moves away from a shutdown.In typical embodiments, in the context of the weighting factor determination process, the weighting factor value is determined on the basis of a weighting factor curve which describes the weighting factor value as a function of the current engine torque, wherein the weighting factor curve typically has the value "0" for a current engine torque which corresponds to the continuous torque value, and / or wherein the weighting factor curve typically has a maximum value for a current engine torque which corresponds to a maximum torque value, wherein the maximum torque value is greater than the continuous torque value, and / or wherein a gradient of the weighting factor curve in the direction of the maximum torque value typically increases continuously, at least if a gradient increase torque value is exceeded. In typical embodiments, the maximum torque value is a torque that the electric motor can deliver for a duration of about 30 seconds without being overloaded. In advantageous embodiments, the weighting factor curve is not predefined by a mathematical function, but by a look-up table. Such a look-up table is typically set by a development engineer in the configuration of an electric vehicle or a control device for an electric vehicle or the like. The maximum value is a maximum value that the weighting factor can assume during the course of the method. In other words, this maximum value is therefore output as a weighting factor value within the scope of the weighting factor determination process when and only when the current motor torque of the electric motor is at the maximum torque value. For all current engine torques which are smaller than the maximum torque value, weighting factor values which are each smaller than the maximum value are output by the weighting factor determination process in accordance with the present invention. For this reason, smaller weighting factor values are then also added to such moments in the integration step. It is thus achieved that not all loads above the continuous torque are of equal importance. The fact that, in addition, in typical embodiments, the gradient of the weighting factor curve is not constant but increases toward the maximum torque value has the advantage that current engine torques are all the more important the more they approach the maximum torque value. The inventors have found through experiments that such a weighting factor curve with increase in slope in the direction of the maximum torque value is advantageous because reliable and pleasant down-regulation can thus be made possible, at least in some cases. The formulation "at least when a slope increase torque value is exceeded" is to be understood in such a way that the weighting factor curve can initially increase linearly, i.e. with a constant slope, in a range between the continuous torque value and the slope increase torque value and can only increase its slope successively after the slope increase torque value is reached.In typical embodiments, the method comprises a torque value determination process, within the scope of which the continuous torque value and / or the maximum torque value is / are determined continuously as a function of a current engine speed. In typical embodiments, the continuous determination of the continuous torque value and / or the maximum torque value is accomplished using curves which indicate the continuous torque value and / or the maximum torque value as a function of a current engine speed. These curves are typically described by look-up tables rather than mathematical functions. In typical embodiments, each of the two curves has a constant value first (i.e. between a rotational speed value "0" and a higher rotational speed value, which is referred to as a reduction threshold), i.e. runs horizontally. Subsequently, each curve typically falls off in a nonlinear manner, in particular first very steeply and then increasingly flatter. In other words, the steady-state torque values and / or the maximum torque values are typically higher for low engine speeds than for high engine speeds.In the framework of the cut-off process, in cases where the integration value has exceeded the threshold value, the current motor torque of the electric motor is cut off, wherein a degree of cut-off is determined as a function of the integration value, wherein the degree of cut-off is determined by a control percentage, wherein the control percentage for the threshold value is 100%, wherein the control percentage for an integration value which continues to increase typically becomes smaller and smaller, wherein the control percentage for a maximum integration value has the value 0%, wherein the control percentage between the threshold value and the maximum integration value preferably falls linearly. In typical embodiments, the maximum integration value is about twice as high as the threshold. A settling process configured in this way has the advantage that, starting from a point in time at which the integration value exceeds a threshold value, settling is carried out and the electric motor is thus protected from overloading, wherein the settling does not take place abruptly, but rather becomes progressively stronger depending on how large the integration value actually becomes. Despite the down-regulation, an acceptable driving comfort in an electric vehicle can thereby be maintained. However, other types of shutdown are also possible, for example a step-like shutdown or a non-linear shutdown or even an abrupt shutdown.In typical embodiments, a limit torque for the electric motor is continuously calculated within the scope of the method, preferably within the scope of the shutdown process, wherein the limit torque is calculated according to the following formula: wherein M Grenz is the limit torque, wherein M Dauer is the continuous torque value, wherein M Max is the maximum torque value and wherein k is the control percentage.In typical embodiments, the electric motor must not deliver torque that exceeds the limit torque at any time. In this way, overloading of the electric motor is prevented.The object is furthermore achieved by a system comprising means for carrying out a method according to at least one of the aforementioned embodiments.In advantageous embodiments, the system is suitable for carrying out and / or coordinating and / or controlling a method according to at least one of the aforementioned embodiments. For this purpose, the system advantageously comprises suitable components, for example a weighting factor determination component and / or an integration component and / or a cut-off component and / or a torque value determination component and / or an engine speed determination component and / or a limit value torque calculation component, which is suitable for continuously calculating the limit value torque during operation of the electric motor according to the above-mentioned formula.In advantageous embodiments, the system comprises a control component which is suitable for controlling the method.Advantageously, at least some of the aforementioned components are implemented in the system by means of computer program code. In advantageous embodiments, the system, in particular at least some of the aforementioned components, is at least partially part of a vehicle controller and / or a cloud. In typical embodiments, the system comprises a digital control unit and / or a display and / or means for data input and / or means for data output.In one embodiment of the invention, a vehicle is suitable for carrying out a method according to at least one of the aforementioned embodiments and / or comprises a system according to one of the aforementioned embodiments. For this purpose, the vehicle typically comprises means for carrying out a method according to at least one of the aforementioned embodiments.In one embodiment of the invention, a computer program comprises instructions which, when the computer program is executed by a computer, cause the computer program to execute one of the aforementioned methods. The computer program can also be referred to as a computer program product.In one embodiment of the invention, a computer-readable medium comprises computer program code for carrying out one of the aforementioned methods. The term "computer-readable medium" is to be understood here in particular, but not exclusively, as hard disks and / or servers and / or memory sticks and / or flash memories and / or DVDs and / or Bluerays and / or CDs. In addition, the term "computer-readable medium" is also to be understood as meaning a data stream, as arises, for example, when a computer program and / or a computer program product is downloaded from the Internet.Brief Description of the DrawingsThe invention is briefly explained below with reference to drawings, in which: FIG. 1 : shows a schematic illustration of a method according to the invention in one possible embodiment, FIG. 2 shows a possible curve which maps the continuous torque value as a function of the current engine speed, FIG. 3 shows a possible curve which maps the maximum torque value as a function of the current engine speed, FIG. 4 : shows a weighting factor curve in a first possible embodiment, FIG. 5 shows a weighting factor curve in a second possible embodiment, FIG. 6 : shows a control percentage curve in a possible embodiment, and FIG. 7 : shows a schematic illustration of a vehicle according to the invention with a system according to the invention in one possible embodiment.DESCRIPTION OF PREFERRED EMBODIMENTSFIG. 1 shows a schematic representation of a method according to the invention in one possible embodiment. In particular, FIG. 1 shows a flow chart with a torque value determination process P 1, a weighting factor determination process P 2, an integration process P 3 and a settling process P 4. The method typically runs continuously during the operation of an electric vehicle, that is to say for example in an endless loop. It is also possible for at least some of the processes P 1, P 2, P 3 and P 4 illustrated in FIG. 1 to run parallel and / or overlapping at least temporarily. The torque value determination process P 1 is continuously supplied with the current engine speed 1. This actual engine speed 1 is shown in FIG. 1 as a thick arrow. Also, the other bold arrows in FIG. 1 represent data flows. Based on the current engine speed 1, the torque value determination process P 1 continuously determines a continuous torque value 2 and a maximum torque value 3. Examples of such curves are shown in Figs. 2 and 3, which are discussed below. The continuous torque value 2 and the maximum torque value 3 are respectively applied to both the weighting factor determination process P 2 and the settling process P 4. In the weighting factor determination process P 2, a weighting factor value 4 is determined based on the continuous torque value 2 and the maximum torque value 3. This determination of the weighting factor value 4 takes place within the scope of the weighting factor determination process P 2 with the aid of a weighting factor curve, which will be discussed in detail with reference to FIGS. 4 and 5. The weighting factor value 4 is then fed to the integration process P 3. In the integration process P 3, the weighting factor value 4 is added to an integration value 5. It must be thought that, since the method shown in FIG. 1 runs continuously, weighting factor values 4 are permanently added to the integration process P 3 during the course of the method, which weighting factor values are added to the integration value 5, so that the integration value 5 permanently increases (or also decreases in the course of the method, namely if negative weighting factor values 4 are present). The integration value 5 shown in FIG. 1 is thus likewise a continuously changing value. This integration value 5 is then fed to the settling process P 4. The settling process P 4 is additionally supplied with a threshold value 6 and a maximum integration value 7. The threshold value 6 is a threshold value to which the integration value 5 is continuously compared. If the integration value 5 exceeds the threshold value 6, then a reduction of the mechanical power or of the torque of the electric motor is started. The maximum integration value 7 is a value that the integration value 5 cannot exceed. Thus, when the integration value 5 reaches this maximum integration value 7, addition to the integration value 5 is stopped, and the settling process P 4 adjusts the electric motor to the constant torque value 2. In other words, the electric motor can then no longer supply torque that is greater than the continuous torque value. Only an addition of negative weighting factor values 4 is possible in this case, so that the integration value 5 can only be reduced in this case, but cannot be increased. If the integration value 5 decreases again in this case, then a torque which exceeds the continuous torque value 2 becomes possible again per peu. The continuous torque value 2 and the maximum torque value 3 are fed to the settling process P 4 because the settling process P 4 continuously calculates the limit value torque 8 which the electric motor must not exceed at any time as a function of these two torque values 2, 3. In the exemplary embodiment shown in FIG. 1, this limit value torque 8 is determined according to the following formula: wherein M Grenz is the limit value torque 8, wherein M Dauer is the continuous torque value 2, wherein M Max is the maximum torque value 3 and wherein k is the control percentage k.The limit value torque 8 is continuously output by the control process P 4 so that the components of the vehicle which control the electric motor constantly know what maximum torque the electric motor is allowed to deliver.FIG. 2 shows a possible curve which maps the continuous torque value 2 as a function of the current engine speed 1. As can be seen in FIG. 2, the continuous torque value 2 in a low rotational speed range is initially constant at a specific value, subsequently the continuous torque value 2 falls, initially comparatively steeply, then increasingly less steeply.FIG. 3 shows a possible curve which maps the maximum torque value 3 as a function of the current engine speed 1. Also with reference to FIG. 3, it can be said that the maximum torque value 3 for relatively low rotational speeds 1 is initially constantly at a certain value and subsequently drops in a manner comparable to the curve shown in FIG. 2.FIG. 4 shows a weighting factor curve 12 in a first possible embodiment. The weighting factor curve 12 describes the weighting factor value 4 as a function of the current engine torque 9. the weighting factor values 4 are continuously determined in the course of the method using this curve as part of the weighting factor determination process P 2. Curve 12 shown in FIG. 4 has a weighting factor value 4 with the value "0" for continuous torque value 2. For current engine torques 9, which are less than the continuous torque value 2, the weighting factor values 4 are negative. For current engine torques 9, which exceed the continuous torque value 2, the weighting factor curve 12 outputs positive weighting factor values 4. At a current engine torque 9, which corresponds to the maximum torque value 3, the weighting factor value 4 has a maximum value 10, which can also be referred to as a maximum weighting factor value 10. Between the continuous torque value 2 and the maximum torque value 3, the weighting factor curve 12 rises continuously. In particular, the weighting factor curve 12 has a constant gradient in a range between the continuous torque value 2 and a gradient increase torque value 11 and increases in particular linearly. Between the increase in gradient torque value 11 and the maximum torque value 3, a gradient of the weighting factor curve 12 increases successively, so that at the end of the weighting factor curve 12, namely when the maximum torque value 3 is reached, the gradient of the weighting factor curve 12 is maximum, at least for the positive region of the weighting factor curve 12.FIG. 5 now shows a weighting factor curve 12 in a second possible embodiment. FIG. 5 again shows the weighting factor value 4 as a function of the current engine torque 9 by the weighting factor curve 12. However, the weighting factor curve 12 in FIG. 5 has a different shape than the weighting factor curve 12 in FIG. 4. Rather, a positive continuous torque weighting factor value 13 results with the weighting factor curve 12 in FIG. 5 for a continuous torque value 2. In the case of the maximum torque value 3, the weighting factor value 4 again has the value of the maximum weighting factor value 10. In such a case, the integration value is then typically reduced or deleted in another way in order to ensure that the electric motor is relieved, for example based on a temperature measurement at the electric motor.FIG. 6 shows a control percentage curve 23 in one possible embodiment. The control percentage curve 23 describes the course of the control percentage k as a function of the integration value 5. For an integration value 5 between "0" and "1000", the control percentage curve 23 runs constantly at a control percentage of 100%. When the integration value 5 becomes larger than "1000", the control percentage k also decreases: in the embodiment shown in FIG. 6, the control percentage k between the integration values 5 "1000" and "2000" decreases linearly from 100% to 0%. Considering the above-mentioned formula for calculating the limit torque 8, the control percentage curve 23 shown in FIG. 6 reveals that up to a moment when the integration value 5 reaches the value "1000" as a threshold value, the limit torque 8 corresponds to the maximum torque value 3 because the control percentage k up to then has the value "100%". As long as the integration value 5 has not yet reached the value "1000" (this corresponds to the previously introduced threshold value 6), the electric motor may be operated up to its maximum torque value 3. When the integration value 5 has reached the value "2000" and the control percentage has the value "0%" accordingly, it is apparent from the above formula that the limit value torque 8 then corresponds exactly to the continuous torque value 2. The electric motor may then only be operated at most up to its continuous torque value 2. If the integration value 5 is between the value "1000" (i.e. the threshold value 6) and the value "2000" (i.e. the maximum integration value 7), then the limit value torque 8 which the electric motor is allowed to deliver at maximum is obtained with the above formula, wherein the control percentage k is then naturally also determined according to the control percentage curve 23 (and is accordingly located in the linearly decreasing range of the control percentage curve 23.FIG. 7 now shows a schematic representation of a vehicle 14 according to the invention with a system 16 according to the invention and an electric motor 15 in a possible embodiment. The system 16, which is suitable for carrying out a method according to the invention for shutting down the electric motor 15, is suitable for acting on the electric motor 15, which is illustrated by the thick arrow in FIG. 6. The system 16 comprises the components 17, 18, 19, 20 and 21, which are suitable for carrying out processes and / or partial aspects of the method, namely a weighting factor determination component 17, an integration component 18, a settling component 19, a torque value determination component 20, an engine speed determination component 21 and a limit value torque calculation component 22.The invention is not limited to the described exemplary embodiments. The scope of protection is defined by the claims.In principle, all methods described in the description or in the claims can be carried out by apparatuses which comprise means for carrying out the respective method steps of these methods.Reference numerals denote reference numerals1 Current engine speed 2 Continuous torque value 3 Maximum torque value 4 Weighting factor value 5 Integration value 6 Threshold value 7 Maximum integration value 8 Limit value torque 9 Current engine torque 10 Maximum value / maximum weighting factor value 11 Increase in gradient torque value 12 Weighting factor curve 13 Continuous torque weighting factor value 14 Vehicle 15 Electric motor 16 System 17 Weighting factor ascertainment component 18 Integration component 19 Decrease component 20 Torque value ascertainment component 21 Engine speed ascertainment component 22 Limit value torque calculation component k Control percentage P 1 Torque value ascertainment process P 2 Weighting factor ascertainment process P 3 Integration process P 4 Decrease process

Claims

Method for regulating down an electric motor (15), characterized in that the method comprises the following: - a weighting factor determination process (P2) in the scope of which weighting factor values (4) are determined continuously, - an integration process (P3) in the scope of which the weighting factor values (4) are added up, so that an integration value (5) is formed, and - a regulating down process (P4) in the scope of which the electric motor (15) is regulated down if the integration value (5) is above a threshold value (6), wherein, in the scope of the regulating down process (P4), in cases where the integration value (5) has exceeded the threshold value (6), the current motor torque (9) of the electric motor (15) is regulated down, wherein a degree of the regulating down is determined as a function of the integration value (5), wherein the degree of the downregulation is determined by a control percentage (k), wherein the control percentage (k) for the threshold value (6) is 100%, wherein the control percentage (k) typically becomes smaller and smaller for an integration value (5) which increases further, wherein the control percentage (k) for a maximum integration value (7) has the value 0%, wherein the control percentage (k) preferably decreases linearly between the threshold value (6) and the maximum integration value (7).Method according to Claim 1, characterized in that, within the scope of the weighting factor determination process (P2), a current motor torque (9) of the electric motor is compared with a continuous torque value (2), wherein a positive weighting factor value (5) is determined if the current motor torque (9) is greater than the continuous torque value (2) and wherein a negative weighting factor value (5) is determined if the current motor torque (9) is less than the continuous torque value (2).Method according to Claim 2, characterized in that, within the scope of the weighting factor determination process (P2), the weighting factor value (4) is determined on the basis of a weighting factor curve (12) which describes the weighting factor value (4) as a function of the current engine torque (9), - wherein the weighting factor curve (12) typically has the value "0" for a current engine torque (9) which corresponds to the continuous torque value (2), and / or - wherein the weighting factor curve (12) typically has a maximum value (10) for a current engine torque (9) which corresponds to a maximum torque value (3), - wherein the maximum torque value (3) is greater than the continuous torque value (2), and / or - wherein a slope of the weighting factor curve (12) typically increases continuously in the direction of the maximum torque value (3), at least if a slope increase torque value (11) is exceeded.Method according to one of Claims 2 to 3, characterized in that the method comprises a torque value determination process (P1), within the scope of which the continuous torque value (2) and / or the maximum torque value (3) is / are determined continuously as a function of a current engine speed (1).Method according to claim 1, characterised in that a limit value torque (8) for the electric motor (15) is continuously calculated within the framework of the method, preferably within the framework of the shutdown process (P4), wherein the limit value torque (8) is calculated according to the following formula: M G r e n z = M D a u e r + k ≥ ( M M a x - M D a u e r ) wherein M Grenz is the limit value torque (8), wherein M Dauer is the continuous torque value (2), wherein M Max is the maximum torque value (3) and wherein k is the control percentage (k).A system (16) comprising means for performing a method according to any one of claims 1 to 5.Vehicle (14) suitable for carrying out a method according to one of Claims 1 to 5 and / or comprising a system (16) according to Claim 6.A computer program comprising instructions which, when the computer program is executed by a computer, cause the computer program to carry out the method of any one of claims 1 to 5.A computer readable medium, characterized in that the computer readable medium comprises computer program code for performing a method according to any one of claims 1 to 5.

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