Method and control device for verifying the plausibility of parameters of a damped system

Abstract

A method for verifying the plausibility of quantities of a damped system, namely for checking whether a first quantity, preferably an output quantity, of the damped system lies within a defined tolerance band around a second quantity, preferably an input quantity, of the damped system, wherein the tolerance band is defined by an upper limit and a lower limit, wherein the upper limit and the lower limit are determined depending on a predetermined upper limit, depending on the predetermined lower limit and depending on a change in the second quantity, characterized in that when the change in the second quantity is less than a limit value, the predetermined upper limit is used as the upper limit and the predetermined lower limit as the lower limit, whereas when the change in the second quantity is greater than the limit value,An adjusted upper limit that deviates from the specified upper limit and / or an adjusted lower limit that deviates from the specified lower limit is determined and used.

Description

The invention relates to a method for plausibility checking variables of a damped system. Furthermore, the invention relates to a control device for plausibility checking variables of a damped system.From practice, automatic transmissions of motor vehicles with a hydrodynamic starting element are known, wherein a hydrodynamic starting element is also referred to as a converter. Such a converter is an attenuated system, in which it is necessary to plausibilize the variables, in particular whether a first variable of the attenuated system, which is in particular designed as an output variable, lies within a tolerance band around a second variable of the attenuated system, which is in particular designed as an input variable. Here, the tolerance band is defined by an upper limit and a lower limit which are fixedly predetermined according to practice. Up to now, it has not been possible to carry out the plausibility check correctly in all operating situations, since the attenuation may have such an important effect that the plausibility check known in practice leads to a misdiagnosis. There is therefore a need to improve the plausibility checking of variables of a damped system, in particular of a converter. In particular in the case of speed-adaptive dampers, which are also referred to as DAT converters, the problem occurs particularly strongly.Such methods for plausibility checking variables of a damped system are known from documents DE 10 2012 110 597 A1, DE 103 55 022 B4 and DE 10 2006 032 727 A1, wherein the damped system is in particular a hydrodynamic starting element.Proceeding from this, the object of the invention is to provide an improved method for plausibility checking variables of a damped system and a control device for carrying out the method.This object is achieved by a method for plausibility checking variables of a damped system according to patent claim 1. According to the invention, the upper limit and the lower limit are determined as a function of a predefined upper limit, as a function of the predefined lower limit and as a function of a change in the second variable.The invention proposes determining the upper limit and the lower limit of the tolerance band for plausibility checking by the second variable as a function of how the second variable changes, that is to say as a function of the gradient of the second variable. The plausibility check can thus be carried out particularly advantageously.Furthermore, if the change in the second variable is smaller than a limit value in terms of amount, the predefined upper limit is used as the upper limit and the predefined lower limit is used as the lower limit, whereas if the change in the second variable is larger than the limit value in terms of amount, an adapted upper limit deviating from the predefined upper limit and / or an adapted lower limit deviating from the predefined lower limit is determined and used. In the case of a relatively small gradient of the second variable, the predefined upper limit and the predefined lower limit are accordingly used as upper limit and lower limit of the tolerance band for plausibility checking. Then, on the other hand, if the gradient of the second variable is relatively large, a deviating adapted upper limit and / or a deviating adapted lower limit is determined and used for the tolerance band of the plausibility check, wherein the adaptation of the upper limit and / or the lower limit is in particular dependent on how strongly the change and thus the gradient of the second variable deviates from the limit value. This allows a particularly advantageous plausibility check.According to an advantageous development, if the change in the second variable is greater in magnitude than the limit value and the change has a positive sign, the adapted lower limit deviating from the predefined lower limit is determined and used. Then, if the change in the second variable is greater in magnitude than the limit value and the change has a negative sign, the adapted upper limit deviating from the predefined upper limit is determined and used. This allows a particularly advantageous plausibility check. In the preferred application of plausibility checking of variables of a converter, this development presupposes a non-force-locking transmission which interacts with the converter, since, in the event of a force-locking connection in the transmission being present, the turbine of the converter is coupled to the output.According to an advantageous development, the predefined upper limit is defined by a predefined positive offset and the predefined lower limit is defined by a predefined negative offset with respect to the second variable. Then, if the change in the second variable is greater in terms of amount than the limit value, the predefined positive offset and / or the predefined negative offset is multiplied by a spreading factor which is greater than 1 and which is dependent on how much the change in the second variable is greater in terms of amount than the limit value. Preferably, furthermore, if the change in the second variable is greater in terms of amount than the limit value, the upper limit adapted as a function of the spreading factor and / or the upper limit adapted as a function of the spreading factor is filtered with a delay factor which is dependent on the amount by which the change in the second variable is greater in terms of amount than the limit value. This allows a particularly preferred plausibility check of the variables of the damped system.Preferably, the method according to the invention checks whether the first variable of the damped system embodied as a converter of an automatic transmission, embodied as a turbine rotational speed and thus as a transmission input rotational speed, lies within a defined tolerance band around the second variable of the converter embodied as a pump rotational speed and thus as a drive unit rotational speed, wherein the first variable of the second variable lags behind in a damped manner. In this application, the method according to the invention can be used particularly advantageously.The control device according to the invention is defined in claim 8.Preferred refinements emerge from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawings, without being restricted thereto. The following shows: FIG. 1 is a schematic illustration of a transducer; FIG. 2 shows curves according to the prior art; FIG. 3 shows curves according to the method according to the invention; and FIG. 4 is a block diagram of a control device according to the invention.The present invention relates to a method for plausibility checking variables of a damped system and to a control device for carrying out the method.The invention is described below for the preferred application of plausibility checking of variables of a damped system embodied as a converter of an automatic transmission. FIG. 1 schematically shows a converter 1 of an automatic transmission, wherein a converter input shaft 2 and a converter output shaft 3 of the converter 1 are shown. A drive unit, such as an internal combustion engine, is typically coupled to the converter input shaft 2. A transmission is typically coupled to the converter output shaft 3, for example a transmission input shaft of an automatic transmission. The converter 1 comprises an impeller 5, a turbine 6 and a stator 7 which interacts with a freewheel 8. The converter input shaft 2 and thus the shaft of a drive unit is coupled to the pump wheel 5. The converter output shaft 3 and thus a transmission input shaft of a transmission, not shown, is coupled to the turbine wheel 6. Converter 1 also has a converter bypass clutch 4, with torque equality between converter input shaft 2 and converter output shaft 3 when converter bypass clutch 4 is closed.FIG. 2 shows curve profiles 10, 11, 12 and 13 over time t, which are valid in a method known from practice for plausibility checking. In the specific case, a plausibility check is carried out as to whether a first variable, namely an output variable of the converter 1, which is the rotational speed of the turbine wheel 6 or the rotational speed of the output shaft 3, is in a defined tolerance band around a second variable, namely an input variable of the converter 1, which is the rotational speed of the pump wheel 5 or the rotational speed of the converter input shaft 2. In FIG. 2, the curve profile 10 visualizes the time profile of the second variable or input variable or of the rotational speed of the pump wheel 5 or of the transmission input shaft 2, respectively. the curve profile 11 of FIG. 2 visualizes the time profile of the output variable or of the rotational speed of the turbine wheel 6 and thus of the transmission output shaft 3.A tolerance band defined by an upper limit 12 and a lower limit 13 is spanned around the input variable 10 of the converter 1, wherein a check is made for plausibility checking whether the output variable 11 of the converter 1 lies around the input variable 10 of the converter 1 in the tolerance band defined by the upper limit 12 and the lower limit 13.If the first variable or output variable 11, which lags behind the second variable or input variable 10 in attenuated form, lies within the tolerance band around the second variable or input variable 10, plausible variables are present. If the first variable or output variable 11 lies outside the tolerance band, non-plausible variables are present.According to practice, the upper limit 12 and the lower limit 13 are each predefined by an offset with respect to the second variable or input variable 10, wherein this offset can be identical for the upper limit and the lower limit. A predefined upper limit 12 is accordingly defined by a predefined positive offset and the predefined lower limit 13 by a predefined negative offset with respect to the input variable 10 of the converter 1, wherein, according to practice, the predefined positive offset and the predefined negative offset are constant.If, for example, in the case of a transmission in the neutral position, the accelerator pedal or accelerator pedal is actuated on the driver side, the input variable 10 changes with a large gradient according to FIG. 2, wherein the output variable 11 of the converter 1 then reaches outside the tolerance band defined by the upper limit 12 and the lower limit 13, as a result of which then, after practice, a fault event or non-plausible variables of the converter 1 are detected, although there is actually no fault event. This is to be avoided with the invention.The invention proposes determining the upper limit and the lower limit for plausibility checking as a function of the predefined upper limit, as a function of the predefined lower limit and as a function of the change in input variable 10.Then, if the change or the gradient of the input variable 10 is smaller in terms of amount than a temporal limit value, the predefined upper limit is used as the upper limit and the predefined lower limit is used as the lower limit. In this case, there is then no adaptation of the upper limit and lower limit with respect to the predefined upper limit and the predefined lower limit.In other words, when the change or the temporal gradient of the second variable or of the input variable 10 is smaller in magnitude than a limit value, the actual upper limit used for plausibility checking corresponds to the predefined upper limit and the actual lower limit used for plausibility checking corresponds to the predefined lower limit.In contrast, if the change in the input variable 10 or the temporal gradient thereof is greater than the limit value in terms of amount, an adapted upper limit deviating from the predefined upper limit and / or an adapted lower limit deviating from the predefined lower limit is determined and used for plausibility checking.In other words, if the change or the temporal gradient of the second variable or of the input variable 10 is greater in magnitude than the limit value, the actual upper limit used for plausibility checking deviates from the predefined upper limit and / or the actual lower limit used for plausibility checking deviates from the predefined lower limit.FIG. 3 shows curves 10, 11, 12' and 13' over time t, curves 10 and 11 of FIG. 3 corresponding to curves 10 and 11 of FIG. 2, curve 10 thus corresponding to the input variable of converter 1 and curve 11 corresponding to the output variable of the same.Curve curves 12' and 13' show upper and lower limits adapted according to the invention, namely curve curve curve 12' an adapted upper limit and curve curve curve 13' an adapted lower limit for the tolerance band, which is used for plausibility checking the variables.The adapted upper limit 12' deviates at least partially from the predetermined upper limit 12 and the adapted lower limit 13' deviates at least partially from the predetermined lower limit 13.In the preferred exemplary embodiment shown, the procedure is such that, if the change in the second variable or input variable 10 is greater in magnitude than the limit value and the change has a positive sign, as is the case in FIG. 3 before the time t 1, the adapted lower limit 13' deviating from the predefined lower limit 13 is determined and used for plausibility checking, the upper limit 12 then preferably remains unchanged.If, on the other hand, the change in the input variable 10 is greater in magnitude than the limit value and the change in the same has a negative sign, as is the case in FIG. 3 after the time t 1, the adjusted upper limit 12' deviating from the predefined upper limit 12 is determined and used for plausibility checking, the lower limit 13 is then preferably not adjusted or then remains unchanged.As already stated, the predefined upper limit 12 is defined by a predefined positive offset and the predefined lower limit 13 by a predefined negative offset with respect to the input variable 10, wherein these two offsets can be of the same magnitude.Then, if the change in the second variable or the input variable 10 of the converter 1 is greater in terms of amount than the limit value, the predefined positive offset and / or the predefined negative offset is multiplied by a spreading factor which is greater than 1 and which is dependent on how much the change in the input variable 10 is greater in terms of amount than the limit value. The more the change in the input variable 10 deviates in magnitude from the limit value, the greater the spreading factor is also selected.If the change in the input variable 10 of the converter 1 is greater in magnitude than the limit value, provision is preferably made for a delay factor to also be determined in addition to the spreading factor. The upper limit adapted as a function of the spreading factor and / or the lower limit adapted as a function of the spreading factor is then filtered with this delay factor, wherein the delay factor, like the spreading factor, is preferably dependent on how much the change in the input variable 10 of the converter 1 is greater in terms of amount than the limit value.FIG. 4 shows a block diagram of a control device 20 which serves to carry out the method according to the invention. The control device 20 comprises means for carrying out the method, wherein these means are hardware-side means and software-side means.The hardware-side means of the control device 20 include, for example, a memory 21 with the memory areas 21 aand 21 b. Furthermore, the hardware-side means of the control device 20 comprise a processor 22 for data processing. As a further hardware-side means, the control device 20 comprises at least one data interface 23, at which variables are provided by a data bus 28, namely, in the exemplary embodiment shown, the input variable 10 of the converter 1, which is the rotational speed of the pump wheel 5 or the rotational speed of the converter input shaft 2 or the rotational speed of a drive unit, and the output variable 11 of the converter 1, which is the rotational speed of the turbine wheel 6 or the rotational speed of the converter output shaft 3 or the rotational speed of a transmission input shaft.The input variable 10 of the converter 1 and the output variable 11 of the converter 1 are preferably measured variables.The output 11 of the converter 1 lags behind the input 10 of the converter 1 in a damped manner.In the memory area 21 aof the memory 21, a value of the input variable 10 provided at the interface 23 is stored which is a defined number X sampling cycles before the current sampling cycle.The value of the input variable 10 provided at the data interface 23 for a current sampling cycle is compared in a calculation block 24 with the value of the input variable 10 stored in the memory area 21 a, which is the defined number X sampling cycles before the current sampling cycle, wherein the change of the input variable 10 is thereby determined in the calculation block 24, i.e. a temporal gradient of the input variable 10 of the converter 1.In the calculation block 25, the respectively determined change of the input variable 10 is compared with a limit value, and depending on this comparison, i.e. depending on whether the change of the input variable 10 of the converter 1 is greater or less than a limit value, the above-mentioned spreading factor and preferably also the above-mentioned delay factor is determined.In this case, it is provided in particular that the spreading factor is determined in such a way that the same is selected to be greater the more the change in the input variable 10 deviates from the limit value.The delay factor is also preferably determined in such a way that the same is selected to be larger, the more the change in the input variable 10 of the converter 1 deviates from the limit value.The spreading factor determined in block 25 is provided to calculation block 26, wherein in calculation block 26 the predefined negative offset and / or the predefined positive offset are adapted as a function of the spreading factor in order to ascertain an adapted lower limit 13' and / or an adapted upper limit 12' as a function of the adapted positive offset and / or as a function of the adapted negative offset.The adapted upper limit and adapted lower limit thus determined are provided by the calculation block 26 to the calculation block 27, to which the determined delay factor is also provided by the calculation block 25, wherein the upper limit adapted as a function of the spreading factor and / or the lower limit adapted as a function of the spreading factor is filtered with the delay factor in the calculation block 27, in particular via a PT 1- filter.The limit value required for carrying out the method according to the invention, with which the change in the input variable 10 of the converter 1 is compared, is kept ready in the memory area 21 bof the memory 21. The predetermined negative and positive offset can also be kept ready in the memory area 21 bof the memory 21.Furthermore, data are also stored in the memory area 21b, on the basis of which the spreading factor and preferably also the delay factor can be determined. These can be characteristic curves or characteristic maps or tabular interpolation points or interpolation values for the spreading factor and the deceleration factor. It is possible to interpolate between such support values.Accordingly, in the sense of the present invention, a dynamic operating situation is first detected in which the change in the input variable 10 of the converter 1 is greater than a limit value. This is done in calculation block 24 of control device 10, in which a gradient of input variable 10 is determined. For this purpose, a difference between a value of input variable 10 provided at a current sampling time or sampling cycle and a value of input variable 10 stored in memory area 21 a, which value was previously provided at interface 23 and has a defined number of sampling times or sampling cycles, is ascertained. If this difference is greater than the limit value, the predefined upper limit and the predefined lower limit are not used for plausibility checking, rather an adapted upper limit and / or an adapted lower limit are determined and used for plausibility checking.The adaptation of the upper limit and / or lower limit takes place in the calculation blocks 25, 26 and 27, wherein in block 25 the spreading factor and preferably also the delay factor is determined first, in each case depending on how much the change in the input variable 10 of the converter 1 is greater in terms of amount than the limit value. The spreading factor is provided to the calculation block 26 and the delay factor is provided to the block 27. With the aid of the spreading factor 26, the predefined positive offset and / or the predefined negative offset is adapted in order to determine an adapted upper limit and / or an adapted lower limit, wherein the adapted upper limit and / or the adapted lower limit are filtered with the aid of the delay factor in order to delay the decaying thereof.For plausibility checking, it is then checked whether the output variable 11 lies within or outside the tolerance band around the input variable 10, which is dependent on the adapted upper limit and / or the adapted lower limit. Then, if the output variable 11 lies within the tolerance band around the input variable 10, plausible variables 10, 11 are present.Reference numerals denote reference numerals1 Converter 2 Converter input shaft 3 Converter output shaft 4 Converter bypass clutch 5 Pump wheel 6 Turbine wheel 7 Stator 8 Freewheel 10 Curve profile 11 Curve profile 12 Curve profile 12' Curve profile 13 Curve profile 13' Curve profile 20 Control device 21 Memory 21 a Region 21 b Region 22 Processor 23 Interface 24 Block 25 Block 26 Block 27 Block 28 Data bus t 1 Point in time

Claims

Method for plausibility checking variables of a damped system, namely for checking whether a first variable, preferably an output variable, of the damped system lies within a defined tolerance band around a second variable, preferably an input variable, of the damped system, the tolerance band being defined by an upper limit and a lower limit, the upper limit and the lower limit being determined as a function of a predefined upper limit, as a function of the predefined lower limit and as a function of a change in the second variable, characterized in that, if the change in the second variable is smaller in terms of amount than a limit value, the predefined upper limit is used as the upper limit and the predefined lower limit is used as the lower limit, whereas, if the change in the second variable is larger in terms of amount than the limit value, the upper limit and the predefined lower limit are used as the lower limit, an adjusted upper limit deviating from the predefined upper limit and / or an adjusted lower limit deviating from the predefined lower limit is determined and used.Method according to Claim 1, characterized in that, if the change in the second variable is greater in terms of amount than the limit value and the change has a positive sign, the adapted lower limit which deviates from the predefined lower limit is determined and used.Method according to Claim 2, characterized in that, if the change in the second variable is greater in terms of magnitude than the limit value and the change has a negative sign, the adapted upper limit which deviates from the predefined upper limit determines and uses it.Method according to one of Claims 1 to 3, characterized in that the predefined upper limit is defined by a predefined positive offset and the predefined lower limit is defined by a predefined negative offset with respect to the second variable.Method according to Claim 4, characterized in that, if the change in the second variable is greater in terms of amount than the limit value, the predefined positive offset and / or the predefined negative offset is multiplied by a spreading factor which is greater than 1 and which is dependent on the amount by which the change in the second variable is greater in terms of amount than the limit value.Method according to Claim 5, characterized in that, if the change in the second variable is greater in terms of amount than the limit value, the upper limit which is adapted as a function of the spreading factor and / or the lower limit which is adapted as a function of the spreading factor is filtered with a delay factor which is dependent on the amount by which the change in the second variable is greater in terms of amount than the limit value.Method according to one of Claims 1 to 6, characterized in that it is checked whether the first variable, which is designed as a turbine rotational speed and thus as a transmission input rotational speed, of the damped system, which is designed as a converter of an automatic transmission, lies within a defined tolerance band around the second variable, which is designed as a pump rotational speed and thus as a drive unit rotational speed, of the converter.Control device for checking the plausibility of variables of a damped system, namely for checking whether a first variable, preferably an output variable, of the damped system lies within a defined tolerance band around a second variable, preferably an input variable, of the damped system, wherein the tolerance band is defined by an upper limit and a lower limit, characterized in that the control device determines the upper limit and the lower limit as a function of a predefined upper limit, as a function of the predefined lower limit and as a function of the change in the second variable, and wherein the control device has means for carrying out the method according to one of Claims 1 to 7.

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