Method for correcting physical variable value determined using sensor

Abstract

The invention relates to a method for correcting a value of a physical variable of a refrigerant in a refrigerant circuit determined using sensors, the refrigerant circuit comprising a compressor for compressing the refrigerant, at least two sensors being provided in the refrigerant circuit, which sensors are provided for determining the physical variable of the refrigerant. In an operating state of the refrigerant circuit in which the refrigerant is in a balanced state, the method includes determining, for each of the at least two sensors, a sensor individual value of a physical variable, determining a deviation of each of the sensor individual values from a common reference value formed by the plurality of sensor individual values, and determining a sensor individual correction rule for each of the at least two sensors according to the determined deviation. In an operating state in which the compressor is operating, the method comprises determining a physical variable using one of the at least two sensors and correcting the physical variable using a sensor individual correction rule assigned to the sensor used.

Description

Field of the Invention

[0001] The present invention relates to a method for correcting values of physical variables determined using sensors, as well as a computing unit and a computer program product for performing the method. Background Art

[0002] In a refrigerant circuit, pressure sensors and temperature sensors are typically used to control and / or monitor the operation of the refrigerant circuit. Generally, at least one pressure sensor can be used in the high-pressure region (downstream of the refrigerant compressor or the compressor) and in the low-pressure region (upstream of the compressor), respectively. At least one temperature sensor can also generally be used. Depending on the configuration of the refrigerant circuit, other pressure and / or temperature sensors can also be used.

[0003] Sensors generally have a tolerance range within which the actual value lies compared to the value output by the sensor. Depending on the accuracy of the individual sensor, the consistency between the values measured by different sensors may not be sufficient. In the case of a refrigerant circuit, for example, a physical model is used to determine the mass flow rate of the refrigerant. The physical model can be based on, for example, the pressure difference or pressure ratio at the compressor and the valves (i.e., the pressures determined at a plurality of different points). In contrast, when determining the superheat and subcooling of the refrigerant, the consistency between the pressure and temperature in the two-phase region of the refrigerant plays a decisive role. For operating the refrigerant circuit, these variables generally need to be as accurate as possible. For example, during superheat regulation, the minimum stable value that can be adjusted is generally higher than the most effective value. If the tolerance of the measured value is large and stable regulation is required, it is generally necessary to adjust to a value higher than the minimum stable value. Summary of the Invention

[0004] According to the present invention, there is provided a method for correcting values of physical variables determined using sensors, as well as a computing unit and a computer program product having the features of the independent claims. Advantageous designs are the subject matter of the dependent claims and the following description.

[0005] The present invention utilizes the measure of calibrating (Abgleich) all sensors (especially pressure and temperature sensors) at the time point when the refrigerant circuit is in a substantially balanced state, so as to be able to identify and correct sensor errors or inaccuracies. This calibration is used to determine the correction rule for each sensor, and then this correction rule is used in the subsequent operation of the refrigerant circuit to correct the corresponding sensor signals, thereby determining as correct a value as possible. Since the pressure present in the refrigerant circuit is temperature-dependent and this pressure corresponds to the boiling point curve (also known as the dew point curve) of the refrigerant used in a wide temperature range (where a two-phase system exists in the refrigerant circuit), the pressure value and the temperature value can be converted into each other. By correcting the values determined by the sensors, the assumed tolerance range is narrowed, thereby enabling the refrigerant circuit to operate more effectively (with a lower safety factor for stable operation).

[0006] In the present invention, the balanced state is understood as a state of the refrigerant circuit in which the refrigerant upstream and downstream of the compressor (or the refrigerant compressor) in the refrigerant circuit has substantially the same values in terms of pressure and temperature. In particular, in the balanced state in this sense, the deviation of the pressure and / or temperature of the refrigerant upstream of the compressor from the pressure and / or temperature of the refrigerant downstream of the compressor is less than 20%, less than 10%, less than 5% or less than 2%.

[0007] The method according to the present invention can be used to correct the values of the physical variables of the refrigerant in the refrigerant circuit determined using sensors. The refrigerant circuit includes a compressor for compressing the refrigerant and at least two sensors for determining the physical variables of the refrigerant. The physical variables are especially state variables and / or intensive physical variables.

[0008] Specifically, the method according to the present invention in the operating state of the refrigerant circuit when the refrigerant is in a balanced state includes: determining the sensor individual values of the physical variables of each of the at least two sensors, determining the deviation of each sensor individual value from the common reference value formed by the plurality of sensor individual values, and determining the sensor individual correction rule for each of the at least two sensors according to the determined deviation. In addition, in the operating state when the compressor is running, the method includes: using one of the at least two sensors to determine the physical variable, and using the sensor individual correction rule assigned to the used sensor to correct the physical variable.

[0009] In particular, if the compressor has not been running for at least a pre-determinable period of time, there exists a balanced state. For example, this can be determined by recording the operating phases of the compressor over time.

[0010] Alternatively or in addition, in order to confirm whether there is an equilibrium state, it is also possible to analyze the rate of change of the physical variable to confirm whether the refrigerant is in an equilibrium state. If the rate of change is lower than a pre-determined threshold, an equilibrium state can be considered to exist.

[0011] In at least one embodiment, this correction is performed on several, in particular all, of the at least two sensors. This means that with the aid of the correction rules, the physical variable can be determined more accurately and / or correctly overall, especially at different positions within the refrigerant circuit, which has a positive effect on the operation or control of the refrigerant circuit. In particular, errors or inaccuracies due to sensor aging can be corrected over a relatively long operating time. This means that the initial calibration can be readjusted without special maintenance.

[0012] In at least one embodiment, the average value, in particular the arithmetic mean value, of at least two physical variable values is used as a common reference value, and the at least two physical variable values are respectively determined using different sensors among the at least two sensors. This is particularly advantageous in the case where the refrigerant is actually in equilibrium, because in this state, the physical variables everywhere in the refrigerant circuit actually have the same value. Usually, the sensors have a certain measurement value scatter, but this measurement value scatter is usually evenly distributed around the actual value, so the arithmetic mean value is the best approximation of the actual value of the physical variable.

[0013] In at least one embodiment, the physical variable includes pressure and / or temperature. These physical variables are variables that are particularly relevant to the operation of the refrigerant circuit and are usually detected by sensors in most refrigerant circuits.

[0014] In at least one embodiment, if at least a first sensor among the at least two sensors is used to determine the temperature and at least a second sensor among the at least two sensors is used to determine the pressure, the sensor individual value of the first sensor can be converted into the unit of the sensor individual value of the second sensor, or the sensor individual value of the second sensor can be converted into the unit of the sensor individual value of the first sensor, wherein the conversion is performed using a pre-determined relationship between the pressure and temperature of the refrigerant in the refrigerant circuit (especially the boiling point curve mentioned above). In this way, more sensors can be included in a single correction measure overall, which on the one hand improves the robustness and on the other hand increases the utility of the method (due to higher accuracy and a larger number of corrected sensor values).

[0015] In at least one embodiment, the method includes determining whether the compressor has not been operating for at least a pre-determinable period of time based on the rate of change over time of at least one individual sensor value. In particular, if the rate of change is below a pre-determinable threshold, it can be confirmed that the compressor has not been operating for at least a pre-determinable period of time. In other words, it is possible to check for the existence of the equilibrium state that has been explained by analyzing the rate of change, because in the equilibrium state, the physical variables are substantially constant (provided that the ambient temperature is constant), which corresponds to a rate of change of zero.

[0016] In at least one embodiment, at least three sensors are used, and when forming a common reference value, the maximum and / or minimum individual sensor values are not considered. This reduces the probability of an incorrect value occurring when forming the average value. In particular, before excluding a value in this way, the distance of each individual sensor value from the reference value can be determined, and if the threshold distance is exceeded, the corresponding value is not considered when re-determining the reference value. In other words, before determining the actually valid reference value (using good-quality values), the quality of each individual sensor value can first be estimated based on its distance from the temporary reference value.

[0017] In at least one embodiment, the method further includes identifying a fault state of the refrigerant circuit based on the deviation of one or more determined individual sensor values from the common reference value. In particular, the fault state may include one or more of the following cases: incorrect refrigerant amount in the refrigerant circuit and failure of one or more of at least two sensors. For example, if an individual sensor value deviates significantly from the reference value, the relevant sensor can be considered to have failed. On the other hand, if the individual sensor values of all (or at least all properly operating) sensors of one type are very similar to each other, but the individual sensor values of another type of sensor have a significant difference after unit conversion, that is, for example, all temperature sensors show similar values to each other and all pressure sensors show similar values to each other, but the pressure value does not correspond to the temperature value according to the boiling point curve, it can be determined that the refrigerant filling amount in the refrigerant circuit is incorrect. In this case, the pre-determined relationship between pressure and temperature no longer conforms to the expected behavior, and thus an incorrect filling amount can be inferred.

[0018] The computing unit according to the present invention, such as the control device of the refrigerant circuit, especially for use in a motor vehicle, is in particular configured by programming techniques to perform the method according to the present invention.

[0019] It is also advantageous to implement the method according to the invention in the form of a computer program or a computer program product, as this particularly results in lower costs, especially when the control device to be executed is still used for other tasks and thus exists anyway. Finally, a machine-readable storage medium is provided, on which the above computer program product is stored. Storage media or data carriers suitable for providing computer program products particularly include magnetic, optical, and electrical memories, such as hard disks, flash memories, EEPROMs, DVDs, etc. The program can also be downloaded via a computer network (Internet, intranet, etc.). Such a download can be carried out wired, i.e., via a cable connection, or wirelessly (e.g., via a wireless local area network, 3G, 4G, 5G, or 6G connection, etc.).

[0020] Further advantages and embodiments of the invention result from the description and the drawings. Description of the Drawings

[0021] The invention is schematically illustrated according to an embodiment in the drawings, and the invention will be described below with reference to the drawings.

[0022] Figure 1 A refrigerant circuit that can be used in an embodiment of the invention is shown in a simplified schematic diagram.

[0023] Figure 2 An embodiment of the method according to the invention is schematically shown in the form of a simplified flow chart. Detailed Description of the Invention

[0024] Figure 1 A refrigerant circuit that can be used in an embodiment of the invention is schematically shown and generally designated by 100. The refrigerant circuit 100 includes a compressor 130 for compressing the refrigerant, and the refrigerant can be temporarily stored in a reservoir 132, for example.

[0025] The refrigerant is a heat transfer fluid that undergoes a phase change, particularly between a liquid and a gaseous state, in at least some operating states of the refrigerant circuit 100. For example, carbon dioxide and / or hydrocarbons, particularly ethane, propane, butane, or their derivatives, or mixtures thereof, can be used as the refrigerant.

[0026] The compressed refrigerant can be conveyed downstream of the compressor 130 to a first heat exchanger 150, where the compressed refrigerant exchanges heat with a cooling medium (such as air from the external atmosphere). In particular, the compressed refrigerant can release a large amount of heat to the cooling medium, thereby causing the refrigerant to at least partially condense. This is particularly useful when the refrigerant circuit 100 is used to cool a component 110.

[0027] Downstream of the first heat exchanger, the refrigerant can be expanded by means of an expansion valve 155 and then conveyed to a second heat exchanger 112, in which the refrigerant undergoes further heat exchange, in particular with a heat transfer fluid (such as a water-based or oil-based one) that exchanges heat with a component 110 to be temperature-controlled, in particular cooled. Downstream of the second heat exchanger 112, the refrigerant can return to the compressor 130 or the accumulator 132.

[0028] In the present example, sensors 161, 162, 163, 164 and 165 are respectively arranged upstream and downstream of the compressor 130, the heat exchangers 150, 112 and the valve 155 for detecting physical variables of the refrigerant, in particular pressure and / or temperature. The sensors 161, 162, 163, 164, 165 are respectively connected to the computing unit 120 in a data-conducting manner, for example via a communication bus system or other wired or wireless communication media. In particular, in the case where the refrigerant circuit 100 is part of a vehicle, the sensors can be connected to the computing unit 120 via a CAN bus.

[0029] The computing unit is also connected to the compressor 130 and the valve 155 in a signal-conducting manner so as to be able to control them. For this purpose, the same or different communication channels as those for the signal transmission between the transmitter and the computing unit can be used.

[0030] In the following, an embodiment of the method according to the invention will also be described with reference to the device components, as Figure 2 schematically shown and generally designated by 200. In particular, reference can be made to Figure 1 the embodiment of the refrigerant circuit just described and shown above. However, it should be clearly emphasized here that the present invention can also be used for other suitable refrigerant circuits other than the refrigerant circuit 100 and is not dependent on or limited to the embodiment of the specifically described refrigerant circuit. For a better understanding of the present invention, the reference to Figure 1 and the above explanations are only for illustrative purposes.

[0031] In the method 200, in step 210, sensor signals from at least two sensors, for example sensor signals from five temperature and / or pressure sensors 161, 162, 163, 164, 165, are received at the signal input of the computing unit 120, for example.

[0032] Based on these signals, in step 215, it is determined whether the refrigerant circuit, or rather the refrigerant, is in a substantially balanced state. For example, the gradient or the rate of change over time of one or more received sensor signals can be analyzed. If the determined gradient is below a predefined threshold, which can in particular be close to zero, the refrigerant circuit can be considered to be in a balanced state. Alternatively or additionally, the operating phases of the compressor 130 recorded over time can also be analyzed to determine whether a balanced state exists. In particular, if the compressor 130 has not been operating for at least a predefinable period of time, a balanced state can be assumed. In this case, the method 200 in the example will continue with step 220.

[0033] In step 220, based on the received sensor signals, the individual sensor values related to the physical variables detected by the sensors are determined respectively. Generally, electronic or electrical sensors can be used in the refrigerant circuit 100, so the sensor signals received by the computing unit can be (analog and / or digital) electrical signals. Therefore, in step 220, the computing unit can determine the physical variable values (for example, the specifically detected pressure value or the specifically detected temperature value) respectively according to the electrical signals of each individual sensor, for example, according to the sensor characteristic curves stored in the computing unit or in a data memory that can be called by the computing unit.

[0034] In step 225, it can be determined whether all sensors have detected the same physical variable, for example, whether all sensors have transmitted pressure signals or all sensors have transmitted temperature signals. If this is not the case, the method 200 will continue with step 227, in which the individual sensor values of one type of sensor (for example, the values of all pressure sensors) are converted to the units of another type (for example, converted to temperature). For this purpose, in particular, the refrigerant boiling point curve stored in the computing unit or its data memory can be used.

[0035] In step 230, a common reference value is calculated based on the (possibly converted) individual sensor values, for example in the form of an arithmetic mean. To form the reference value, in particular, a provisional reference value can first be determined based on all the individual sensor values, and then it is checked whether one or more sensors have provided unreasonable values, or whether all the values meet the quality criteria. For this purpose, for example, the distance between the respective individual sensor value and the common (provisional) reference value can be determined. If this distance exceeds a pre-determinable threshold (quality criterion), the relevant individual sensor value can be ignored when finally (re-)determining the reference value, in order to prevent clearly incorrect values from being included in the reference value. As an alternative or supplement to the pre-determinable threshold, to exclude individual sensor values, it can also be determined which individual sensor values have the smallest distance from the provisional reference value and only these are used for the final reference value (for example, when determining the final reference value, a certain number of individual sensor values with the largest distance from the provisional reference value can be excluded). Figure 2 The repetition of step 230 is indicated by an arrow in the figure.

[0036] Based on the reference value determined in this way and the corresponding (possibly converted) individual sensor values from step 220 or 227, in step 240 an individual sensor correction rule is determined for each sensor. For example, this can be a multiplication factor and / or an (additive) offset value, with which the corresponding individual sensor value is corrected to obtain the actual value of the physical variable. However, if necessary, other types of correction rules can also be used in addition to the correction rules specifically mentioned here as examples.

[0037] During the operation of the refrigerant circuit 100, i.e., outside the equilibrium state (see step 215), in step 250 the corresponding corrected individual sensor values of the refrigerant physical variables are determined based on the received sensor signals, taking into account the corresponding individual sensor correction rules from step 240.

[0038] In particular, the individual sensor correction rules can be stored in the computing unit 120 or its data memory and can be used to correct the corresponding individual sensor values in the operating phase (in step 215) in which it is determined that there is no equilibrium state. In other words, if there is no equilibrium state at the start of the operating phase of the refrigerant circuit 100, but the correction rules have been determined at an earlier time point, the method can also be used. In particular, when new correction rules are saved later, the previous correction rules can be adjusted or replaced accordingly.

[0039] In addition to correcting the individual sensor values as explained above, in method 200, a common reference value and the deviation of the individual sensor values from this reference value can also be used to determine the fault state of the refrigerant circuit 100. For this purpose, in step 260, these deviations are analyzed. For example, during the analysis, it can be determined whether sensors of the same type (such as all temperature sensors) have deviations similar to the reference value, while sensors of another type (such as pressure sensors) show deviations different from those of the first group but also similar to each other. For example, the individual sensor values of all temperature sensors may be higher than the reference value, while the individual sensor values of all pressure sensors may be lower than the reference value. In this case, it can be considered that although the values provided by the sensors are basically correct, the conversion rule (step 227) is not correct. This is likely to occur if the refrigerant filling amount in the refrigerant circuit 100 on which the conversion rule is based is incorrect.

[0040] In another example, during the analysis 260, it can be confirmed that the value provided by one of the sensors 161, 162, 163, 164, 165 deviates significantly from the reference value. In this case, it can be considered that the relevant sensor is defective.

[0041] Therefore, in step 260, it can be determined whether the refrigerant circuit 100 is in a fault state, and in some cases, the fault state can also be identified. In this way, the corresponding fault source can be eliminated in a targeted manner, so that the refrigerant circuit 100 can then operate as expected again.

[0042] It should be emphasized here that the present invention is not limited to the step-by-step procedures described here. In particular, the individual or all of the steps explained can also be carried out in a different order, for example, in the reverse order or partially or completely in parallel or simultaneously. In some embodiments, the individual or all method steps can also be executed partially or fully continuously or cyclically repeated.

Claims

1. A method (200) for correcting a value of a physical variable of a refrigerant in a refrigerant circuit (100) determined using sensors (161, 162, 163, 164, 165), the refrigerant circuit (100) including a compressor (130) for compressing the refrigerant, Among them, at least two sensors (161, 162, 163, 164, 165) are provided in the refrigerant circuit (100), the sensors being arranged to determine the physical variable of the refrigerant, wherein, in an operating state of the refrigerant circuit (100) in which the refrigerant is in an equilibrium state (215), the method (200) includes: determining (210) an individual sensor value (220) of the physical variable for each of the at least two sensors (161, 162, 163, 164, 165), determining the deviation of each individual sensor value (220) from a common reference value (230) formed by a plurality of individual sensor values, and determining an individual sensor correction rule (240) for each of the at least two sensors (161, 162, 163, 164, 165) based on the determined deviation, and wherein, in an operating state in which the compressor (130) is running, the method (200) includes: determining the physical variable using one of the at least two sensors (161, 162, 163, 164, 165), and correcting (250) the physical variable using the individual sensor correction rule (240) assigned to the used sensor.

2. The method (200) according to claim 1, wherein Taking the average value, in particular the arithmetic mean value, of at least two physical variable values as the common reference value (230), the at least two physical variable values being determined by different sensors among the at least two sensors respectively.

3. The method (200) according to claim 1 or 2, wherein, The physical variable includes pressure and / or temperature.

4. The method (200) according to claim 3, wherein, In a case (225) where at least a first sensor among the at least two sensors (161, 162, 163, 164, 165) is used to determine temperature and at least a second sensor among the at least two sensors (161, 162, 163, 164, 165) is used to determine pressure, converting (227) the individual sensor value of the first sensor into the unit of the individual sensor value of the second sensor, or converting the individual sensor value of the second sensor into the unit of the individual sensor value of the first sensor, wherein the conversion (227) is performed using a pre-determinable relationship between the pressure and temperature of the refrigerant in the refrigerant circuit (100), in particular the boiling point curve.

5. The method (200) according to any one of the preceding claims, comprising determining (215) whether the refrigerant is in an equilibrium state, wherein, Determining whether the refrigerant is in an equilibrium state includes: determining whether the compressor (130) has not been running for at least a pre-determinable period of time, and / or based on the time change rate of at least one of the individual sensor values (210).

6. The method (200) according to claim 5, wherein, When the time change rate is lower than a pre-determinable threshold, it is confirmed that the refrigerant is in an equilibrium state.

7. The method (200) according to any one of the preceding claims, wherein, Use at least three sensors (161, 162, 163, 164, 165), and do not consider the maximum sensor individual value and / or the minimum sensor individual value when forming the common reference value (230).

8. The method (200) according to any one of the preceding claims, comprising identifying a fault state (260) of the refrigerant circuit (100) based on the deviation of the determined one or more sensor individual values from the common reference value (230).

9. The method (200) according to claim 8, wherein, The fault state includes one or more of the following cases: an incorrect amount of refrigerant in the refrigerant circuit (100) and a fault in one or more of the at least two sensors (161, 162, 163, 164, 165).

10. A computing unit, which is arranged to carry out all the method steps of the method according to any one of the preceding claims.

11. A computer program product, which, when implemented on a computing unit, causes the computing unit to execute the method according to any one of claims 1 to 9.

12. A machine-readable storage medium, having stored thereon the computer program product according to claim 11.

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