Test stand and method for power-limited testing of a test object

Abstract

In order to specify a method for power limitation on a test stand (100), which is better than the methods known from the prior art, a power comparison value (eP) is determined from a dynamometer power (Pdyno,1) of a load machine (M1) of the test stand (100) and a predefined power limit value (Pmax), a manipulated-variable limiting factor (klim) is determined from the power comparison value (eP) and the determined manipulated-variable limiting factor (klim) is used to scale an upper manipulated-variable limit value (ulim1,max) and / or a lower manipulated-variable limit value (ulim1,min) to limit a dynamometer manipulated variable (UD1) to control the load machine (M1), said scaling being based on at least one dynamometer state variable (XD1) of the load machine (M1).

Description

[0001] Test bench and procedure for power-limited testing of a test specimen

[0002] The present invention relates to a method for power limitation on a test bench, wherein a test object is loaded by a load machine and the load machine is controlled by a drive control unit. The drive control unit determines a dyno manipulated variable for controlling the load machine from at least one dyno setpoint to be controlled, and at least one power limit value is specified for limiting a dyno power of the load machine. Furthermore, the invention relates to a test bench with a load machine, a test object, and a drive control unit, wherein a power limit value for limiting a dyno power of the load machine is stored in the drive control unit.

[0003] With test benches of various types, it is common practice to use several load units simultaneously, sometimes of different types, to load and thus test one or more test objects. A test bench can be an engine test bench, a powertrain test bench, a transmission test bench, a clutch test bench, or even test benches from the field of electromobility, such as high-speed electric motor test benches, cell testers or battery testers, or even test benches from the field of fuel cell technology. A load unit, in turn, can be an electrical load machine, specifically an electrical synchronous or asynchronous machine that loads a test object in a known manner, such as a drivetrain or an automobile engine.Such test concepts are well known from the state of the art, so that for further details in this regard, reference can be made to the literature, e.g. to EP 3 172 550 B1, AT 520179 B1 or DE 10 2021 125 156 B3.

[0004] Electrical load units, in particular electrical load machines (dynamometers, hereinafter referred to as "dynos"), of a test bench, but in particular also electrical load units from different test benches which together form a test field, are typically connected to a common grid-side electrical converter via a common DC bus. The grid-side converter is connected to a power supply network on the side facing away from the load units in order to either draw energy from the grid to supply the load units or to feed energy generated during testing of a test object, e.g. an internal combustion engine, back into the grid. The grid-side converter is often designed for a lower drive or generation power than the load units used.Depending on the operating conditions of the load units connected to the line-side converter, the power limits intended for the operation of the line-side converter may be reached or sometimes exceeded. This is obviously undesirable and, depending on the severity of the violation, can lead to errors on the test bench. Errors on the test bench can, in turn, result in unintentional aborts of test programs, and aborts of test programs can ultimately lead to the loss of important measurement results, some of which may have originated from long-running endurance tests.

[0005] This problem is known in the prior art, e.g. from the documents DE 10 2018 103 433 A1 , which shows a test bench for an internal combustion engine with two load controllers, and DE 10 2021 206 778 A1 , which teaches a power-limiting method for operating a drive train of a work machine.

[0006] However, the approaches known from the state of the art have in common that they address specifics, particularly those resulting from different operating states of a test object, a test bench, or one or more load units, only inadequately and, above all, imprecisely. In many cases, this results in more severe restrictions on test operation during test bench operation than would be necessary to meet specified performance limits. This results in performance losses and / or deterioration of test results.

[0007] It is therefore the object of the present invention to provide an improved method for power limitation on a test bench.

[0008] According to the invention, this object is achieved for the power limitation method mentioned at the outset by determining a power comparison value from the dyno power and the power limit value, determining a manipulated variable limiting factor from the power comparison value, and using the determined manipulated variable limiting factor to scale an upper manipulated variable limit value and / or a lower manipulated variable limit value for limiting the dyno manipulated variable as a function of at least one dyno state variable of the load machine.

[0009] This inventive approach ensures that limit values ​​for a manipulated variable are not rigidly modified depending on the difference between the power to be monitored and a specified power limit, but rather that additional information is taken into account, specifically information about at least one state variable of the load machine. In this way, manipulated variable limits can be influenced much more accurately in many cases, and an unnecessary reduction in the available control range can often be avoided.

[0010] Quantities relating to a load machine (“dyno,” “dynamometer”) (dyno power, dyno setpoint, dyno manipulated variable, dyno state variable, etc.) are given the prefix “dyno-” in the context of this discussion to distinguish them from other quantities. The prefix “dyno-” serves merely for linguistic precision, so that, for example, a dyno state variable of a load machine can correspond to any suitable, conventional state variable of a load machine, such as a speed of a load machine, an electric current of a load machine, a torque of a load machine, a magnetic flux of a load machine, or, for example, a dyno setpoint or dyno manipulated variable can be understood as a setpoint or manipulated variable suitable for controlling a load machine, etc.

[0011] With regard to the dyno power used according to the invention, there is flexibility within the scope of this invention, so that a generator electrical power delivered by the load machine to the drive control unit can be used as the dyno power of the load machine, or a motor electrical power delivered by the drive control unit to the load machine can be used as the dyno power of the load machine, or a mechanical shaft power occurring on a dyno shaft of the load machine for the mechanical connection of the load machine to the test object can be used as the dyno power of the load machine.

[0012] Advantageous embodiments of the invention, which in particular enable precise adaptation of the inventive concept to different applications and thus different requirements, result from determining the manipulated variable limiting factor from the power comparison value by means of a suitable limiting control law, e.g. a control law from the area of ​​P, PI or PID controllers, from the area of ​​flatness-based control or from the area of ​​model-predictive control, for which the dyno power can preferably be subtracted from the power limit value to determine the power comparison value, or by determining the dyno state variable of the load machine as the dyno speed of the load machine.

[0013] In a particularly advantageous manner, the dyno state variable of the load machine can be determined from a dyno speed of the load machine, which is advantageously filtered during the calculation of the dyno state variable, e.g. by a hysteresis element, and the upper manipulated variable limit can be scaled if the dyno state variable exceeds a predetermined speed threshold, and / or the lower manipulated variable limit can be scaled if the dyno state variable falls below a predetermined speed threshold. Due to the typically given availability of high-quality (i.e., high-resolution both in terms of time and value) measurement data of dyno speeds of load machines, the use of speeds is often advantageous. In principle, however, the use of a torque, an electrical current or an electrical voltage of a load machine as a dyno state variable is also conceivable.

[0014] A further, particularly advantageous embodiment of the invention results from determining an upper manipulated variable comparison value for describing a deviation between the upper manipulated variable limit and the dyno manipulated variable, as well as a lower manipulated variable comparison value for describing a deviation between the lower manipulated variable limit and the dyno manipulated variable, wherein, in the event that the determined upper manipulated variable comparison value exceeds a predetermined upper deviation threshold and the upper manipulated variable limit is to be scaled according to the invention, the upper manipulated variable limit is changed to an adapted upper manipulated variable limit whose deviation from the dyno manipulated variable is below the predetermined upper deviation threshold, or in the event that the determined lower manipulated variable comparison value exceeds a predetermined lower deviation threshold and the lower manipulated variable limit is to be scaled according to the invention,The lower manipulated variable limit is changed to an adapted lower manipulated variable limit whose deviation from the dyno manipulated variable is below the specified lower deviation threshold. As explained in detail below, this can achieve a faster effect on a dyno manipulated variable in many applications, which can be particularly advantageous in situations involving grid converters with only a low overload capacity.

[0015] A further significant advantage of the present invention is that its applicability is by no means limited to a single dynamometer. Indeed, within the scope of this invention, the power outputs of multiple dynamometers, which may originate from one or more test benches, can also be monitored in combination. For this purpose, the dynamometer outputs of the dynamometers to be monitored are advantageously summed to form a total dynamometer output, and the total dynamometer output is compared with the power limit value to determine the power comparison value. Particularly in the case of multiple dynamometers, but also in situations with only one dynamometer, it can be advantageous to provide separate limit values ​​for a generator total dynamometer output and for a motor total dynamometer output, which is also easily possible within the scope of the invention.

[0016] Furthermore, the stated object is achieved for a test bench mentioned at the outset in that the drive control unit is further configured to determine a power comparison value from the dyno power and the power limit value and a manipulated variable limiting factor from the power comparison value and to use the determined manipulated variable limiting factor to scale an upper manipulated variable limit value and / or a lower manipulated variable limit value for limiting the dyno manipulated variable depending on at least one dyno state variable of the load machine.

[0017] The present invention will be explained in more detail below with reference to Figures 1 to 4, which show exemplary, schematic, and non-limiting advantageous embodiments of the invention. Figure 1 shows an example of a powertrain test bench,

[0018] Fig.2 shows a control circuit according to the invention for controlling a load machine,

[0019] Fig.3 an embodiment of the invention for limiting the power of several load machines,

[0020] Fig.4 shows an embodiment of an allocation unit.

[0021] Fig. 1 shows an example of an arrangement of a test object 1, in this case a drive train, on a test bench 100, in this case a drive train test bench. Drive train test benches such as the one shown in Fig. 1 are well known in the art, e.g., from EP 3 237 875 B1, and are particularly suitable for use with the present invention.

[0022] In the powertrain test bench according to Fig. 1, the test object 1 is physically installed as real hardware on the test bench 100. The powertrain comprises a drive unit 12, such as an internal combustion engine or an electric motor, which drives a transmission 13. A drive shaft 15 connects the transmission 13 to a differential gear 14, which drives two side shafts 16 in a known manner. During normal operation, wheel carriers and tires are arranged on the side shafts 16. On the present test bench 100, however, the vehicle wheel is replaced by loading machines M1, M2, generally by electric motors such as synchronous machines or asynchronous machines, which are referred to in the relevant literature and thus also below in particular as "dynamometers" or "dyno" for short. Variables relating to a loading machine M1, M2, e.g. a speed of a loading machine, a manipulated variable for controlling a loading machine, etc., are, as mentioned, given the prefix “Dyno-” to distinguish them from other quantities on test bench 100.

[0023] The loading machines M1, M2 are connected to the wheel carriers 18 in a suitable manner, e.g., positively connected by a connecting flange 19 and a dyno shaft 20. A loading torque MD is transported via the dyno shafts 20, which is set by the loading machines M1, M2 to load the test specimen 1. The loading torques MD1, MD2 each result in a dyno speed noi, nD2, which, by product formation with the corresponding loading torque MD, each describe a mechanical shaft power.

[0024] In a test specimen 1 corresponding to the illustration in Fig. 1, a braking system is generally also provided to apply a braking torque MB to the drive train for braking. Likewise, further torques may act in the drive train, e.g., a torque from a wheel hub motor or an electric motor in a hybrid drive train, which generates a further drive torque, which does not limit the application of the invention. It should be noted that the drive train test bench according to Fig. 1 is merely an exemplary application of the invention, and that the invention can be used in the same way with other test bench types, e.g., engine test benches, transmission test benches, clutch test benches, fuel cell test benches, and generally in cases where a test specimen drive is replaced by a load machine or a drive machine, etc.

[0025] In order for the load machines M1, M2 to be able to load the test object 1, they must be supplied with electricity. For this purpose, the embodiment shown in Fig. 1 includes an electrical energy transmission network N, a grid converter N-UR and a DC bus BDC. The energy transmission network N is connected to the DC bus BDC via the grid converter N-UR. In this way, alternating electrical quantities transported in the energy transmission network N (in particular mains alternating voltage with a frequency of 50 Hz or 60 Hz and a voltage level of 400 V, 690 V, 10 kV, 20 kV or 30 kV) are first converted into direct electrical quantities, i.e. direct electrical voltage and direct electrical current, which are then transported via the DC bus BDC. The DC variables transported via the DC bus BDC are subsequently fed to different drive control units AR1, AR2, which generate alternating variables, i.e. alternating voltage and alternating current, from the DC variables.The alternating variables generated by the drive control units AR1, AR2 are applied in a known manner to the load machines M1, M2 for control. The frequencies and amplitudes of these alternating variables applied to the load machines M1, M2 are precisely selected and, in particular, adapted to torque and / or speed curves resulting from predetermined test scenarios or test runs in order to precisely reproduce the torque and / or speed curves for testing the test object 1 and to load the test object 1 with them. If a load machine M1, M2 is directly connected to the energy transmission network N, i.e. without an intermediate drive control unit AR1, AR2 and without an intermediate grid converter N-UR, an adaptation and / or change of frequency and / or amplitude would not be possible for obvious reasons.

[0026] The drive control units AR1, AR2 therefore fulfill the function of a frequency converter (FU), which is sufficiently dealt with, for example, in the documents DE 10 2010 052 261 B4 and AT 519261 B1. In order to be able to adjust a load torque MD precisely to a specified setpoint time curve, a wide variety of electronic components are typically installed in the drive control units AR1, AR2, e.g. components for signal processing of measurement signals resulting from the measurement of torques, speeds, currents, etc. Likewise, a modern drive control unit AR1, AR2 typically provides a control unit for open-loop and closed-loop control. A control unit (not shown) of a drive control unit AR1, AR2 can preferably be implemented using microprocessor-based hardware, such as microcontrollers and / or integrated circuits (ASIC, FPGA).

[0027] The electrical powers P sup,1 , P sup,2 are exchanged between the dynamometers M1 , M2 and the drive control units AR1 , AR2. The above-mentioned mechanical shaft powers resulting from the shaft torques MDI , MD2 and shaft speeds noi, nD2 differ only slightly from a corresponding electrical power P sup,1 , P sup,2 , specifically due to internal losses occurring in the dynamometers M1 , M2, which are typically in a range of less than 1%, 2%, 3%, 5% or 10% of a corresponding shaft power. In a known manner, energy flows with different directions arise depending on whether the test object 1 is in motor (i.e. energy absorbing) or generator (i.e. energy releasing) operation.In motor mode, energy is transported from the grid N via the DC bus BDC via the drive control units AR1, AR2 to the load machines M1, M2. In generator mode, the energy is transported in the opposite direction. For example, in motor mode of a load machine M1, M2, the shaft power transmitted to the dyno shafts 20 must first be converted into electrical supply power P. sup ,i,2 are provided via the DC bus BDC.

[0028] In addition to supplying load machines M1, M2 from the energy transmission network N (“motor operation”), the DC bus BDC can therefore be given the task, particularly in the case of powerful, active test objects 1, of feeding energy back from the load machines M1, M2 into the energy transmission network N. If a test object 1 generates, for example, an accelerating torque which, for example, increases the speeds of the side shafts 16 against a load torque MD applied by the load machines M1, M2, a positive energy flow occurs from the drive unit 12 via the drive control units AR1, AR2 to the DC bus BDC and further to the energy transmission network N (“generator operation”).

[0029] As already explained earlier, the N-UR grid converter in particular represents a limiting component in this context. Since an N-UR grid converter must typically convert electrical energy from and for a plurality of load machines M1, M2, but also since the components installed in an N-UR grid converter, such as semiconductor switch modules or diodes or resistors or other power electronic components, cannot be loaded to any desired extent and are therefore also subject to restrictions, N-UR grid converters are regularly operated within the range of their load limits. Load limits are usually expressed in the form of maximum power P m ax. As mentioned, depending on the operating conditions of the load machines connected to the N-UR grid converter, the power limits P max can be reached and sometimes exceeded, which is obviously undesirable and, depending on the severity of the excess, can lead to errors on the test bench and thus also to damage.

[0030] How such problems, which arise in particular from the limitations of the N-UR grid converter, can be solved according to the invention is explained below with reference to Fig.2, initially using the example of only one load machine M1.

[0031] Specifically, Fig.2 shows a coupling plan which can be implemented in particular in a drive control unit AR1, AR2, e.g. as a Simulink coupling plan, and which can be used to implement a method for power limitation on a test bench 100, in which a test object 1 is loaded by a load machine M1, e.g. a drive train in the sense of Fig.1 or another test object 1. The drive control unit AR1 has for this purpose a load machine controller RM1 in order to determine from at least one predetermined dyno setpoint SDI and a dyno actual variable y to be adjusted to the dyno setpoint SDI Di (e.g., a speed noi or a torque) to determine a dyno control variable UDI for controlling the load machine M1. At least one power limit value Pmax is specified to limit a dyno power Pdyno.i of the load machine M1.

[0032] The dyno power Pdyno.i of the load machine M1 can describe a power absorbed, converted, or output by the load machine M1. Since, as explained above, in particular an electrical power P sup ,i and a mechanical shaft power of a load machine M1 usually differ only slightly, depending on the application, a mechanical shaft power can be used as dyno power Pdyno.i, or an electrical supply power P SU p,i , Psu P ,2 can be used as dyno power Pdyno.i, or a combination of a mechanical shaft power and an electrical supply power P su P ,1 , P su P ,2 can be used as dyno power P dyno,1 .

[0033] According to the invention, the coupling plan according to Fig.2 provides for determining a power comparison value ep from the dyno power Pdyno.i of the load machine M1 and the power limit value Pmax and subsequently a manipulated variable limiting factor ki™ from the power comparison value ep, and using the determined manipulated variable limiting factor ki™ to determine an upper manipulated variable limit value uij depending on at least one dyno state variable XD.I of the load machine M1 m i,max and / or a lower manipulated variable limit uij m i,min to limit the dyno control variable UDI ZU.

[0034] In the embodiment according to Fig. 2, to implement the invention, an allocation unit 31 selects, depending on the at least one dyno state variable XD.I, which of the two manipulated variable limit values ​​uumi .min.max is to be scaled. For example, if it turns out that the upper manipulated variable limit value Uümi.max is to be scaled, the lower manipulated variable limit value uij m i,min, however, is not, the upper signal channel outgoing from the allocation unit 31 can be assigned the value of the manipulated variable limiting factor ki™, while the lower one can be assigned the value 1. To implement this assignment, further manipulated variable limiting factors knm.max and kiim.min are provided in Fig. 2. If, as just mentioned, it turns out that the upper manipulated variable limit Uümi.max is to be scaled, the lower manipulated variable limit uij m i,min but not, e.g. kij m ,max=kiim and kij m,min=1 can be selected. A concrete possibility for the design of an allocation unit 31 will be discussed in the course of the discussion of Fig.4.

[0035] In the case shown in Fig.2, the dyno power Pdyno.i is used to determine the power comparison value ep from the power limit value P m ax is subtracted, which corresponds to a common procedure in control engineering. However, other approaches to determining the power comparison value ep are also conceivable, such as filtering the dyno power Pdyno.i in a suitable filter in which the power limit value P m ax is taken into account, or through appropriate product formation, etc.

[0036] Advantageous embodiments of the invention and thus of the coupling plan according to Fig.2, which in particular enable precise adaptation of the inventive concept to different applications and thus different requirements, result from the determination of the manipulated variable limiting factor ki™ from the power comparison value ep by means of a suitable limiting control law RP, e.g. a control law from the area of ​​P, PI or PID controllers, from the area of ​​flatness-based control or from the area of ​​model-predictive control, or further by the determination of the dyno state variable XD,I of the load machine M1 as the dyno speed noi of the load machine M1.

[0037] In the case of determining the dyno state variable XD,I from or as a dyno speed noi, in particular the upper manipulated variable limit value uij mi,max are scaled when the dyno state variable XD.I , ie in this case the dyno speed noi, exceeds a specified speed threshold, or the lower manipulated variable limit uij m i,min can be scaled if the dyno state variable XD,I falls below a specified speed threshold. A dyno speed noi of the load machine M1 can be additionally filtered in a particularly advantageous manner when calculating the dyno state variable XD,1. It has been found that the use of a hysteresis element H is particularly suitable for this purpose. These relationships will be discussed in detail later.

[0038] The invention ensures that limit values ​​for a manipulated variable are not rigidly modified depending on the difference between the power to be monitored and a specified power limit, but rather that information available during the adaptation of manipulated variable limit values ​​is taken into account via at least one state variable XD of the load machine M1. In this way, a much more accurate influence on manipulated variable limits can be achieved in many cases, and an unnecessary reduction in the available control range can often be avoided. The possibility of using a limiting control law RP precisely tailored to an individual application also enables a significant improvement in many cases compared to approaches known from the prior art.

[0039] It should be emphasized that the use of a factor, i.e. the use of a manipulated variable limiting factor khm, represents an equally important, sometimes decisive advantage for power reduction, since such a manipulated variable limiting factor khm can be applied to various physical setpoint variables of the load units (torque, current, etc.) and consequently ensures increased flexibility. In the prior art, absolute values ​​of manipulated variable limits are typically specified directly, which can often lead to obvious problems. If, for example, an electrical voltage is to be limited as a manipulated variable, completely different value ranges must usually be taken into account than when limiting a torque as a manipulated variable. A manipulated variable limiting factor kum according to the invention can be used here without any significant restrictions, even for manipulated variables from different physical domains.

[0040] In a particularly advantageous embodiment of the invention, the manipulated variable limiting factor khm can also be applied to test object setpoints, i.e., to setpoints that are specified, for example, in an engine control unit (ECU) of a test object 1 and implemented by appropriately influencing the test object (e.g., changing an accelerator pedal position a, changing the actuation times of semiconductor switches, etc.). This makes it possible to also include active test objects in the power limitation measures.

[0041] A particularly advantageous embodiment of the invention results from the fact that an upper manipulated variable comparison value for describing a deviation between the upper manipulated variable limit value Uhmi.max and the dyno manipulated variable UDI and a lower manipulated variable comparison value for describing a deviation between the lower manipulated variable limit value u-limi .min and the dyno manipulated variable UDI are determined, wherein in the event that the determined upper manipulated variable comparison value exceeds a predetermined upper deviation threshold value and the upper manipulated variable limit value Uümi.max is to be scaled according to the invention, the upper manipulated variable limit value Uhmi .max is changed to an adapted upper manipulated variable limit value whose deviation from the dyno manipulated variable UDI is below the specified upper deviation threshold, or in the case that the determined lower manipulated variable comparison value exceeds a specified lower deviation threshold and the lower manipulated variable limit value uij. m i,min is to be scaled according to the invention, the lower manipulated variable limit uij mi ,min is changed to an adapted lower manipulated variable limit value whose deviation from the dyno manipulated variable UDI is below the specified lower deviation threshold value.

[0042] In addition to the advantages mentioned above, this approach also solves the problem that individual dyno control variables UDI themselves can often be far away from a control variable limit value uij intended for them. m i.max, reaching a power limit P max makes a restriction of a dyno-manipulated variable UDI necessary. In such a case, if a change in a manipulated variable limiting factor ki™ is only started (slowly), it can sometimes take a considerable amount of time until an inventive reduction of a manipulated variable limit value uij m i,max,min actually begins to affect a manipulated variable. In order to react more quickly, a manipulated variable limit value uij can be set in the case of a large deviation. mi,max,min, for example, can be changed abruptly to an adapted value that is closer to a current value of the manipulated variable UDI, so that the scaling according to the invention begins to take effect earlier. In this context, one speaks of a "jump to the pressure point", since in this way a manipulated variable can be acted on preferably immediately, or at least much more quickly. The deviation threshold can be specified, for example, as a relative value of the dyno manipulated variable UDI, e.g. as 100% of a dyno manipulated variable dui or as 50% of a dyno manipulated variable UDI or as 10% of a dyno manipulated variable UDI . Of course, the specification of a fixed absolute value is also conceivable.

[0043] As is known, the control or regulation of a test bench 100 is typically carried out digitally, i.e., at discrete points in time. In an advantageous manner, a value of a manipulated variable UDI can be used to determine a manipulated variable comparison value, which has been recorded at a discrete point in time, preferably immediately before the discrete point in time at which the inventive scaling of the manipulated variable limiting factor ki™ is to begin. Of course, it is also conceivable to use a value of a manipulated variable limiting value uij from further back. m i,max,min can be used for comparison, and an average value of several past manipulated variable limit values ​​uijmi ,max,min can also be used for comparison.

[0044] In a particularly advantageous manner, the adapted upper manipulated variable limit value can be selected to be equal to a value of the dyno manipulated variable UDI, ie equal to a past value according to the above statements, ie a value recorded at a previous, discrete measuring time, or immediately previous value or mean value, or of course the adapted lower manipulated variable limit value can also be selected to be equal to the dyno manipulated variable UDI.Further design flexibility in implementing this embodiment of the invention arises from selecting the adapted upper manipulated variable limit value as a function of the overload capacity of a grid converter N-UR connected to the drive control unit AR1 or as a function of the at least one dyno state variable XD,I of the load machine M1, and / or selecting the adapted lower manipulated variable limit value as a function of the overload capacity of a grid converter N-UR connected to the drive control unit AR1 or as a function of the at least one dyno state variable XD,I of the load machine M1. If, for example, it is known that the overload capacity of a grid converter N-UR is very low, it can be advantageous to make a rapid, immediate, and large change to a manipulated variable limit value uij. mi,max,min must be provided so that any dyno power Pdyno that occurs can be reduced quickly. Specifically, depending on the overload capacity of a grid converter N-UR, for example, a decision can be made as to whether to jump directly to a value of a dyno manipulated variable UDI or to an adapted value that deviates from the dyno manipulated variable UDI, e.g., by 20%, 10%, or 5%.

[0045] As explained above, Fig. 2 shows an application of the invention for regulating the power of just one load machine M1. In a particularly advantageous manner, however, the invention can be used in particular to regulate multiple powers assigned to multiple load machines M1, M2, .... Multiple load machines M1, M2, ... can originate from a single test bench, like the load machines M1, M2 from the powertrain test bench according to Fig. 1. The multiple load machines M1, M2, ... can also originate from different test benches from a more comprehensive test field. Particularly in engine development, it is common practice to arrange a sometimes large number of engine test benches next to one another, but to supply the given load machines M1, M2 via a common DC bus BDC. How this can be done is shown below with reference to Fig. 3.

[0046] 3, two further controlled load machines M2, M3 are provided for loading a test specimen 1, although this is by no means to be understood as limiting. In the same way, considerably more further load machines M2, M3, M4, ... could be provided. A test specimen 1 loaded by a further load machine M2, M3 can be the same test specimen 1 that is already loaded by the load machine M1. Especially in powertrain test benches, up to six or even more load machines M1, M2 are sometimes common for testing just one test specimen 1. As mentioned, a test specimen 1 loaded by a further load machine M2, M3 can also be a different test specimen, i.e. a test specimen that is different from the test specimen 1 that is loaded by the first load machine M1.For the additional load machines M2, M3, as for the first load machine M1, a further dyno control variable UD2, UD3 is determined for control from a further dyno setpoint SD2, SDS to be controlled, so that the additional load machines M2, M3 also implement or have a dyno power Pdyno,2, Pdyno,3. In order to now calculate the multiple given dyno powers Pd. y no,2, Pdyno,3, it is provided in an embodiment according to Fig.3, the dyno power Pdyno.i of the first load machine M1 and the further dyno powers Pd y no,2, Pdyno,3 to a total dyno power P SU m to combine, in the present case to sum up, in order to obtain from the thus obtained total dyno power P SU m and the power limit P max to determine the power comparison value ep. As before, a manipulated variable limiting factor ki™ is determined from the power comparison value ep, which is then used to scale additional upper manipulated variable limit values ​​uiim2,max, uiim3,max and / or lower manipulated variable limit values ​​uiim2,min, uiim3,min of all load machines M1, M2, M3 to limit the additional dyno manipulated variables UD2, UD2 ZU depending on additional dyno state variables XD,2, XD,3 of the additional load machines M2, M3.

[0047] As a special, advantageous measure, in the variant shown in Fig. 3, a generator maximum power Pmax,gen is provided for the generator case and a motor maximum power Pmax,mot is provided for the motor case, whereby two different manipulated variable limiting factors kiim.gen, khm.mot are determined. In order to be able to further process both of these manipulated variable limiting factors kiim.gen, khm.mot, the allocation units 31 in Fig. 3 each have an additional input. A concrete structure of an allocation unit 31, which in particular can also process two manipulated variable limiting factors ki im,gen, kiim.mot, is discussed below with reference to Fig. 4. According to the above explanations, such a division into two is by no means absolutely necessary, and it is also possible to continue to use just a single power limiting value Pmax.

[0048] Although the specific method of forming the total dyno power P SU m alternatives exist, for example by a weighted addition, the use of a simple sum offers the significant advantage that in the case frequently occurring in practice that the load machines M1, M2, M3 used run in different operating modes (motor, generator), the total dyno power P SU m often does not even exceed a specified limit value, especially since the power flow between the load units on the local intermediate circuit of the test bench system levels itself out by balancing generator and motor power.

[0049] In this context, it should be noted that the powers involved can be assigned different signs depending on the convention and application. For example, in practice, there are cases in which a motor power is assigned a positive sign (“+”), a generator power is assigned a negative sign, or vice versa, where a motor power is assigned a negative sign. A generator signal is provided with a positive sign (“+”). A different sign convention may make it necessary, particularly when implementing the coupling plan shown in Fig.3, to determine the power comparison values ​​e p , m ot and e p , gto reverse the signs. However, such minor adaptations fall within the scope of routine activities of a specialist in the field of control engineering, who will be able to carry out any necessary adjustments without difficulty. It is only necessary to take into account that motor power and generator power are given opposite signs. In the embodiments shown in Figures 2 and 3, the allocation unit 31 mentioned several times above is of key importance. How such an allocation unit 31 can be constructed in concrete terms will be discussed in conclusion with reference to Figure 4. Specifically, in the allocation unit 31 according to Figure 4, a dyno state variable XD is first recorded and filtered by a hysteresis element H. This is done in particular to prevent fluctuations in the dyno state variable XD which could cause nervous switching between the available manipulated variable limiting factors.mot would result in.

[0050] The filtered dyno state variable XD is then scaled with a scaling factor Cv, which preferably conveys information about whether the load torque MD generated by the corresponding load machine is positive or negative and whether the load machine is therefore in motor or generator mode. Depending on the operating mode, the limit factors ki im.mot and ki im,gen can thus be assigned to the correct manipulated variable limit values ​​Uüm.max or uiim.min. In this case, the scaling factor Cv can take on the values ​​1 and -1 and thus, in particular, also reflect the sign convention of the load machine. This allows, preferably in combination with an optional, further change of sign (multiplication by -1) after the switching elements S1, S2 described below, a correct assignment of the limit factors kiim.mot and kiim.gen to the manipulated variable limit values ​​uiim.max or uiim.min, depending on the direction of rotation, the sign conventions, and the operating mode. A dyno state variable XD filtered and scaled in this way subsequently forms an input to two different switching elements S1, S2, so that in the case of a positive value of the filtered and scaled dyno state variable XD, the motor-based manipulated variable limiting factor kiim.mot is output at the output S1-E of the first switching element S1, while the generator-based manipulated variable limiting factor kn is output at the output S2-E of the second switching element S2. m In the case of a negative value of the filtered and scaled dyno state variable XD, a reverse assignment occurs.

Claims

Patent claims 1 . Method for power limitation on a test bench (100), wherein a test object (1) is loaded by a load machine (M1) and the load machine (M1) is controlled by a drive control unit (AR1), wherein the drive control unit (AR1) determines a dyno manipulated variable (UDI) for controlling the load machine (M1) from at least one dyno setpoint value (SDI) to be controlled, and wherein at least one power limit value (Pmax) for limiting a dyno power (Pdyno.i) of the load machine (M1) is specified, characterized in that a power comparison value (ep) is determined from the dyno power (Pdyno.i) and the power limit value (Pmax), that a manipulated variable limiting factor (kum) is determined from the power comparison value (ep), and that the determined manipulated variable limiting factor (khm) is used to determine an upper Control variable limit value (Uhmi.max) and / or a lower manipulated variable limit (uij. mi ,min) to limit the dyno control variable (UDI) ZU scale.

2. Method according to claim 1, characterized in that the dyno power (Pdyno.i) is subtracted from the power limit value (Pmax) to determine the power comparison value (ep).

3. Method according to claim 1 or 2, characterized in that the manipulated variable limiting factor (khm) is determined from the power comparison value (ep) by means of a predetermined limiting control law (RP).

4. Method according to one of the preceding claims, characterized in that a generator electrical power (P sup ,i) is used as dyno power (Pdyno.i) of the load machine (M1) and / or that a motor electrical power (Psup ,i) is used as dyno power (Pdyno.i) of the loading machine (M1) and / or that a mechanical shaft power occurring on a dyno shaft (20) of the loading machine (M1) for the mechanical connection of the loading machine (M1) to the test object (1) is used as dyno power (Pdyno.i) of the loading machine (M1).

5. Method according to one of the preceding claims, characterized in that the dyno state variable (XD.I) of the load machine (M1) is determined from a dyno speed (noi) of the load machine (M1), preferably corresponds to a dyno speed (nD1) of the load machine (M1), and in that the upper manipulated variable limit value (Uhmi .max) is scaled if the dyno state variable (XD.I) exceeds a predetermined speed threshold value and / or in that the lower manipulated variable limit value (uij m i,min) is scaled, when the dyno state variable (XD,I) falls below a specified speed threshold.

6. Method according to claim 5, characterized in that the dyno speed (noi) of the loading machine (M1) is filtered in the calculation of the dyno state variable (XD,I), preferably by a hysteresis element (H).

7. Method according to one of the preceding claims, characterized in that an upper manipulated variable comparison value for describing a deviation between the upper manipulated variable limit value (Uhmi.max) and the dyno manipulated variable (UDI) and a lower manipulated variable comparison value for describing a deviation between the lower manipulated variable limit value (uiimi.min) and the dyno manipulated variable (UDI) are determined, that in the event that the determined upper manipulated variable comparison value exceeds a predetermined upper deviation threshold value and the upper manipulated variable limit value (Uhmi.max) is to be scaled, the upper manipulated variable limit value (Uhmi.max) is changed to an adapted upper manipulated variable limit value whose deviation from the dyno manipulated variable (UDI) is below the specified upper deviation threshold, or in the event that the determined lower manipulated variable comparison value exceeds a specified lower deviation threshold and the lower manipulated variable limit value (uij. m i,min) is to be scaled, the lower manipulated variable limit (uij mi ,min) is changed to an adapted lower manipulated variable limit whose deviation from the dyno manipulated variable (UDI) is below the specified lower deviation threshold.

8. The method according to claim 7, characterized in that the adapted upper manipulated variable limit value is selected to be equal to the dyno manipulated variable (UDI) or that the adapted lower manipulated variable limit value is selected to be equal to the dyno manipulated variable (UDI).

9. The method according to claim 7, characterized in that the adapted upper manipulated variable limit value is selected as a function of an overload capacity of a grid converter (N-UR) connected to the drive control unit (AR1) or as a function of the at least one dyno state variable (XD,I) of the load machine (M1), and / or that the adapted lower manipulated variable limit value is selected as a function of an overload capacity of a grid converter (N-UR) connected to the drive control unit (AR1) or as a function of the at least one dyno state variable (XD,I) of the load machine (M1).

10. Method according to one of the preceding claims, characterized in that at least one further controlled load machine (M2) with a further dyno power (Pdyno,2) is provided for loading the test object (1), for which a further dyno manipulated variable (UD2) for controlling is determined from a further dyno setpoint value (SD2) to be controlled, wherein the dyno power (Pdyno.i) of the first load machine (M1) and the further dyno power (Pdyno,2) are combined to form a total dyno power (P SU m) combined, preferably added to obtain the total dyno power (P SUm) and the power limit value (Pmax), and that the determined manipulated variable limit factor (khm) is used to scale an upper manipulated variable limit value (uiim2,max) and / or a lower manipulated variable limit value (uiim2,min) for limiting the further dyno manipulated variable (UD2) ZU depending on a further dyno state variable (XD,2) of the further load machine (M2).

11. Method according to one of the preceding claims, characterized in that a further test bench (200) with a further test object (P2) and at least one further controlled load machine (M3) with a further dyno power (Pdyno.s) for loading the further test object (P2) is provided, for which a further dyno manipulated variable (UDS) for controlling is determined from a further dyno setpoint value (SDS) to be controlled, wherein the dyno powers (Pdyno.i , Pdyno,2 , Pdyno.s) of the load machines (M1 , M2, M3) of the test bench (100) and of the further test bench (200) are combined, preferably added, to form a total dyno power (Psum) in order to determine from the total dyno power (P SUm) and the power limit value (Pmax), and that the determined manipulated variable limiting factor (kum) is used to scale an upper manipulated variable limit value (uiims.max) and / or a lower manipulated variable limit value (uiim3,min) for limiting the further dyno manipulated variable (UDS) ZU depending on a further dyno state variable (XD.S) of the further load machine (M3) of the further test bench (200).

12. Method according to one of the preceding claims, characterized in that a motor power limit value (P m ax,mot) is specified to limit a motor dyno power (Pdyno.i) of the load machine (M1), that a generator power limit value (Pmax.mot) is specified to limit a generator dyno power (Pdyno.i) of the load machine (M1), that the dyno power (Pdyno.i) and the motor power limit value (P max,mot) a motor power comparison value (ep.mot) is determined, that from the dyno power (Pdyno.i) and the generator power limit value (Pmax, gen) a generator power comparison value (ep, gen ) is determined, that a motor control variable limiting factor (khm.mot) is determined from the motor power comparison value (ep.mot), that a generator control variable limiting factor (kij m ,gen) is determined and that, depending on the dyno state variable (XD.I), either the motor manipulated variable limiting factor (khm.mot) or the generator manipulated variable limiting factor (küm.gen) is used to scale an upper manipulated variable limit value (Uhmi.max) and / or a lower manipulated variable limit value (Uhmi.min) for limiting the dyno manipulated variable (UDI) depending on the dyno state variable (XD.I) of the load machine (M1).

13. Test bench (100) for power-limited testing of a test object (1), comprising a loading machine (M1) for loading the test object (1) for testing, and a drive control unit (AR1) for controlling the loading machine (M1), wherein the drive control unit (AR1) is designed to determine a dyno manipulated variable (UDI) for controlling the loading machine (M1) from at least one dyno setpoint value (SDI) to be controlled, and wherein at least one power limit value (Pmax) is provided for limiting a dyno power (Pdyno.i) of the loading machine (M1), characterized in that the drive control unit (AR1) is further designed to determine a dyno manipulated variable (UDI) from the dyno power (Pdyno.i) and the power limit value (Pmax) to determine a power comparison value (ep) and from the power comparison value (ep) to determine a manipulated variable limiting factor (khm) and to use the determined manipulated variable limiting factor (khm) to scale an upper manipulated variable limit value (u-limi.max) and / or a lower manipulated variable limit value (uumi ,min) for limiting the dyno manipulated variable (UDI) ZU depending on at least one dyno state variable (XD,I) of the load machine (M1).

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