DE102021209966A1 - Actuator and method for determining the temperature of an electrical conductor of an actuator - Google Patents

Abstract

The invention relates to a method for determining a temperature of an electrical conductor of an actuator. A reference measurement is carried out at a first point in time, with a reference temperature being measured as the temperature in an area surrounding the electrical conductor at the first point in time and a reference resistance value being measured as the resistance value of the electrical conductor at the first point in time. Furthermore, the resistance value of the electrical conductor is measured at a second point in time during operation of the actuator. The temperature of the electrical conductor at the second point in time is determined using the reference temperature, the reference resistance value and the resistance value at the second point in time.

Description

The present invention relates to a method for determining a temperature of an electrical conductor of an actuator. The invention further relates to an actuator.

State of the art

Braking systems are known which have an electric motor which is operated in a controlled manner. For component protection, a degradation strategy of the device is necessary when the specified maximum temperatures are exceeded in various hardware components.

A temperature-critical component is the motor, with the motor windings and the permanent magnets each having a specified maximum temperature.

A separate temperature sensor in the engine near the relevant components is usually not used for cost reasons. A temperature determination based on a resistance measurement of the motor windings is made more difficult by the fact that the winding resistances have excessive tolerances.

Due to the unknown engine temperature, the detection of the degradation is usually based only on sensors that measure the temperature near the power electronics. The temperature of the power electronics only partially correlates with the motor temperature. This degradation strategy must be validated empirically and cannot be easily transferred to further developments of a braking system. The correlation between the temperature of the power electronics and the motor temperature will become increasingly difficult due to future smaller packaging dimensions and higher power densities in motor construction.

Disclosure of Invention

The invention provides a method for determining a temperature of an electrical conductor of an actuator and an actuator with the features of the independent patent claims.

Preferred embodiments are the subject of the respective dependent claims.

According to a first aspect, the invention accordingly relates to a method for determining a temperature of an electrical conductor of an actuator. A reference measurement is carried out at a first point in time, with a reference temperature being measured as the temperature in an area surrounding the electrical conductor at the first point in time and a reference resistance value being measured as the resistance value of the electrical conductor at the first point in time. Furthermore, the resistance value of the electrical conductor is measured at a second point in time during operation of the actuator. The temperature of the electrical conductor at the second point in time is determined using the reference temperature, the reference resistance value and the resistance value at the second point in time.

According to a second aspect, the invention relates to an actuator with an electrical conductor, a temperature sensor, which is designed to measure a temperature in an area surrounding the electrical conductor, a resistance sensor, which is designed to measure a resistance value of the electrical conductor, and a computing device. The computing device is designed to determine at a first point in time a temperature measured by the temperature sensor in the vicinity of the electrical conductor as a reference temperature and to determine a resistance value of the electrical conductor measured by the resistance sensor as a reference resistance value. The computing device is also designed to determine a temperature of the electrical conductor at a second point in time, using the reference temperature, the reference resistance value and a resistance value measured by the resistance sensor at the second point in time.

Advantages of the Invention

The invention provides a method for determining the temperature of an electrical conductor of an actuator based on a resistance measurement. It is therefore possible to meet specific requirements without further hardware measures, since devices for measuring resistance are typically already present. Since the resistance value of the electrical conductor can be subject to large component tolerance fluctuations, a calibration is carried out, i.e. reference values for the temperature and the resistance value are determined.

A “temperature in an area surrounding the electrical conductor” can be understood to mean a temperature that is not detected directly on the electrical conductor but at a specified distance from the conductor. For example, the electrical conductor can be located in a housing and the temperature in the vicinity of the electrical conductor is a temperature outside the housing. For this purpose, the temperature sensor is located outside the housing.

wobei T₀ die Referenztemperatur, R(T₀) den Referenzwiderstandswert, R(7) den Widerstandswert zu dem zweiten Zeitpunkt und α_T0 den Temperaturkoeffizienten des elektrischen Leiters bezeichnen. Die Formel kann entweder direkt verwendet werden oder es kann eine Look-up-Table abgespeichert sein, aus welcher der entsprechende Temperaturwert ausgelesen werden kann.According to a further embodiment of the method for determining the temperature of the electrical conductor of the actuator, the temperature T of the electrical conductor at the second point in time is calculated using the following formula: $$T=\left[R\left(T_0\right)\cdot \left(a_{T0}\cdot T_0-1\right)+R\left(T\right)\right]/\left[a_{T0}\cdot R\left(T_0\right)\right]$$

where T ₀ denotes the reference temperature, R(T ₀ ) denotes the reference resistance value, R(7) denotes the resistance value at the second point in time and α _T0 denotes the temperature coefficient of the electrical conductor. The formula can either be used directly or a look-up table can be saved from which the corresponding temperature value can be read out.

According to a further embodiment of the method for determining the temperature of the electrical conductor of the actuator, the reference measurement is carried out when a temperature distribution in the area surrounding the electrical conductor is static and homogeneous. For example, the calibration can be carried out when the device is started. Thus, the calibration takes place under defined conditions.

According to a further embodiment of the method for determining the temperature of the electrical conductor of the actuator, a predetermined criterion is used to determine whether the temperature distribution in the vicinity of the electrical conductor is static and homogeneous. Previous measurement results can be taken into account.

According to a further embodiment of the method for determining the temperature of the electrical conductor of the actuator, a temporal development of the temperature in the vicinity of the electrical conductor and/or a course over time are used to determine whether the temperature distribution in the area surrounding the electrical conductor is static and homogeneous of a current through the electrical conductor is taken into account.

According to a further embodiment of the method for determining the temperature of the electrical conductor of the actuator, it is determined that the temperature distribution in the vicinity of the electrical conductor is static and homogeneous if a period of time during which no current flows through the electrical conductor exceeds a predetermined threshold value . Self-heating can thus be ruled out.

According to a further embodiment of the method for determining the temperature of the electrical conductor of the actuator, self-heating of the electrical conductor is determined based on the course of the current through the electrical conductor over time. It is also determined that the temperature distribution in the vicinity of the electrical conductor is static and homogeneous if self-heating of the electrical conductor falls below a predetermined threshold value. For example, the electrical conductor can be a coil and a winding current flowing through the electrical conductor can be integrated in order to determine temporary self-heating of the electrical conductor by means of modelling.

According to a further embodiment of the method for determining the temperature of the electrical conductor of the actuator, the reference measurement is carried out repeatedly during operation of the actuator. This ensures the accuracy of the measurement even if the environmental conditions change.

According to a further embodiment of the method for determining the temperature of the electrical conductor of the actuator, the actuator is a motor and the electrical conductor is a coil of the motor. Provision can also be made to determine a motor temperature based on the motor winding resistance measured during device operation.

According to a further embodiment of the method for determining the temperature of the electrical conductor of the actuator, a strategy for operating the actuator in the event of degradation is implemented using the determined temperature of the electrical conductor. Thus, an optimized high-temperature degradation strategy can be performed based on the resistance measurement. This increases availability while at the same time guaranteeing component protection.

character list

• 1 ein schematisches Blockdiagramm eines Aktuators gemäß einer Ausführungsform der Erfindung; und
• 2 ein Flussdiagramm eines Verfahrens zum Ermitteln einer Temperatur eines elektrischen Leiters eines Aktuators gemäß einer Ausführungsform der Erfindung.

Show it:

• 1 12 is a schematic block diagram of an actuator according to an embodiment of the invention; and
• 2 a flowchart of a method for determining a temperature of an electrical conductor of an actuator according to an embodiment of the invention.

The numbering of method steps is for the sake of clarity and should not generally imply a specific chronological order. In particular, several method steps can also be carried out simultaneously.

Description of the exemplary embodiments

1 shows a schematic block diagram of an actuator 1. The actuator can at for example an engine, in particular for a motor vehicle. However, the actuator can also be a solenoid valve or, in general, any other actuator that has an electrical conductor through which current flows.

The actuator 1 includes the electrical conductor 2, for example a coil of the motor. The actuator 1 also includes a temperature sensor 3 which measures a temperature in an area surrounding the electrical conductor 2 . The temperature sensor 3 can be located outside of a stator housing, for example, in which a stator and a rotor coil (as an electrical conductor 2) are arranged.

The actuator 1 also includes a resistance sensor 4 which is coupled to the electrical conductor 2 and measures an electrical resistance value of the electrical conductor 2 . For example, the resistance sensor 4 can measure a voltage drop across the electrical conductor 2 and a current flow through the electrical conductor 2 and use this to calculate the electrical resistance value of the electrical conductor 2 .

The actuator 1 also includes a computing device 5 which is coupled to the temperature sensor 3 and the resistance sensor 4 and can optionally send control signals to the temperature sensor 3 and the resistance sensor 4 . Conversely, the computing device 5 receives measurement signals from the temperature sensor 3 and the resistance sensor 4.

The computing device 5 includes a microprocessor, integrated circuit or the like in order to process the measurement signals and optionally to generate the control signals. The computing device 5 also includes at least one memory in order to store the received measurement signals and values calculated therefrom.

The computing device 5 receives a measurement signal from the temperature sensor 3 which includes information relating to the current temperature in the area surrounding the electrical conductor 2 . The information is stored in the memory of the computing device 5 .

Furthermore, the computing device 5 receives a measurement signal from the resistance sensor 4 which includes information relating to the currently measured electrical resistance value. The measurement signal can also include information about the current flow of current through the electrical conductor 2 . The information is also stored in the memory of the computing device 5 .

In particular, information relating to a temporal development of the temperature in the vicinity of the electrical conductor 2 and/or information relating to a temporal progression of the current through the electrical conductor 2 can thus be stored in the memory.

The computing device 5 can use the measurement data from the temperature sensor 3 and the resistance sensor 4 to determine whether a calibration should be carried out. The computing device 5 also determines whether the temperature distribution in the vicinity of the electrical conductor is static and homogeneous. In this case, the computing device 5 can take into account the development over time of the temperature in the area surrounding the electrical conductor 2 and/or information relating to the course of the current through the electrical conductor 2 over time. A necessary condition for recognizing the static and homogeneous temperature distribution can be that no current flows through the electrical conductor 2 for a certain period of time.

An alternative or additional necessary condition for recognizing the static and homogeneous temperature distribution can be that the self-heating of the electrical conductor 2 determined based on the course of the current through the electrical conductor 2 over time falls below a predetermined threshold value. For example, a necessary condition may be that self-heating is zero for at least a predetermined period of time.

The static and homogeneous temperature distribution can also be detected when the actuator 1 is restarted, it being optionally possible to additionally request that the actuator 1 was previously passive or switched off for a predetermined period of time.

If the static and homogeneous temperature distribution has been identified at a first point in time, a reference measurement is carried out. For this purpose, the temperature measured by the temperature sensor 3 is determined as the reference temperature. The electrical resistance value of the electrical conductor 2 determined by the resistance sensor 4 at the first point in time is determined as the reference resistance value.

The computing device 5 is also designed to determine a temperature of the electrical conductor 2 at a second point in time, which is after the first point in time. The second point in time can be during the operation of the actuator 1 . For this purpose, the computing device 5 uses the reference temperature, the reference resistance value and a resistance value measured by the resistance sensor 4 at the second point in time.

The arithmetic unit 5 can be designed to calculate the temperature regularly, for example after fixed predetermined time intervals.

wobei T₀ die Referenztemperatur ist und T die aktuelle Temperatur. α_T0 beschreibt den Temperaturkoeffizienten des Materials. Für einen elektrischen Leiter 2 aus Kupfer gilt bei einer Referenztemperatur von T₀ = 20 °C beispielsweise: $${\alpha }_{T0}=\mathrm{3,93}\cdot {10}^{-3}{\text{K}}^{-1}$$

The temperature dependency of the resistance value R of the electrical conductor 2 is determined by equation (1): $$R\left(T\right)=R\left(T_0\right)\cdot \left[1+a_{T0}\left(T-T_0\right)\right]$$

where T ₀ is the reference temperature and T is the current temperature. α _T0 describes the temperature coefficient of the material. For an electrical conductor 2 made of copper, the following applies at a reference temperature of T ₀ =20° C., for example: $$a_{T0}=3.93\cdot {10}^{-3}{\text{K}}^{-1}$$

For the temperature measurement T during operation, the reference resistance value R(T ₀ ) is first measured by the resistance sensor 4 at the defined reference temperature T ₀ measured by the temperature sensor 3 . During operation, the computing device 5 then determines the temperature T of the electrical conductor 2 via a resistance measurement by the resistance sensor 4 via a conversion of equation (1) as follows: $$T=\left[R\left(T_0\right)\cdot \left(a_{T0}\cdot T_0-1\right)+R\left(T\right)\right]/\left[a_{T0}\cdot R\left(T_0\right)\right]$$

2 shows a flowchart of a method for determining a temperature of an electrical conductor of an actuator, in particular the actuator 1 described above.

First of all, it should be recognized whether the temperature distribution in the vicinity of the electrical conductor 2 is static and homogeneous.

For this purpose, in a first method step S1, time information relating to the historical temperature profile in the area surrounding the electrical conductor 2 and to self-heating due to the energization of the electrical conductor 2 is collected. Furthermore, a current through the electrical conductor 2 is integrated in order to determine a temporary self-heating of the electrical conductor 2 by means of modelling.

In a second method step S2, the information collected in the first method step is used to determine whether the temperature distribution in the vicinity of the electrical conductor 2 is static and homogeneous. In this case it can then be assumed that under these conditions a measured reference temperature (for example in the outside area of a motor) also prevails directly on the electrical conductor 2 (for example in the motor).

The static and homogeneous temperature distribution can be assumed, for example, if the actuator 1 is restarted. For this purpose, it can be known via the time information how long the actuator 1 was passive. The current information can be used to ensure that there is currently no self-heating of the electrical conductor 2 .

A static and homogeneous temperature distribution can thus be assumed if, for example, the electrical conductor 2 has not been energized for a long time and there is also no relevant temperature difference between the temperature sensor 3 and the electrical conductor 2 . This is the case, for example, when the actuator 1 is switched on again after a sufficiently long off time and no appreciable temperature differences between the temperature sensor 3 and the electrical conductor 2 have formed as a result of external influences.

If the conditions for static and homogeneous temperature distribution are not met, method step S1 is repeated, i. H. more information is collected.

Otherwise, in a method step S3, a reference measurement is carried out at a first point in time if a static and homogeneous temperature distribution is present. A reference temperature is determined as the temperature in an area surrounding the electrical conductor 2 at the first point in time, for example by the temperature sensor 3 described above. A reference resistance value is also measured as the resistance value of the electrical conductor 2 at the first point in time, for example by the resistance sensor 4 described above .

In a method step S4, the resistance value of the electrical conductor 2 is measured at a second point in time during the operation of the actuator 1.

In a method step S5, the temperature of the electrical conductor 2 is determined at the second point in time using the reference temperature, the reference resistance value and the resistance value at the second point in time. The relationship between the temperature and the resistance value, ie the temperature coefficient, with a variable reference temperature T ₀ can be stored in the memory of the computing device 5 . In particular, the value of the current temperature can be calculated according to equation (3) above.

Thus, using Equation (3), in further operation under dynamic conditions with inhomogeneous temperature distribution, the temperature of the Actuator 1 are determined, such as an engine temperature.

In a method step S6, a degradation strategy for protecting the actuator components can be implemented based on the determined temperature of the electrical conductor 2. For example, when the temperature of the electrical conductor 2 exceeds a threshold value, a method for controlling the actuator 1 can be carried out.

A new determination of the reference resistance can also take place again during operation under static conditions (no dynamics in the ambient temperature and no recent energization of the electrical conductor 2).

Claims (10)

Method for determining a temperature of an electrical conductor (2) of an actuator (1), with the steps: Carrying out (S3) a reference measurement at a first point in time, a reference temperature being measured as a temperature in an area surrounding the electrical conductor (2) at the first point in time and a reference resistance value being measured as a resistance value of the electrical conductor (2) at the first point in time; Measuring (S4) the resistance value of the electrical conductor (2) at a second point in time during operation of the actuator (1); and Determining (S5) the temperature of the electrical conductor (2) at the second point in time using the reference temperature, the reference resistance value and the resistance value at the second point in time. procedure after claim 1 , wherein the temperature T of the electrical conductor (2) at the second point in time is calculated using the following formula: $$T=\left[R\left(T_0\right)\cdot \left(a_{T0}\cdot T_0-1\right)+R\left(T\right)\right]/\left[a_{T0}\cdot R\left(T_0\right)\right]$$

where T ₀ denotes the reference temperature, R(T ₀ ) denotes the reference resistance value, R(7) denotes the resistance value at the second point in time and α _T0 denotes a temperature coefficient of the electrical conductor (2). procedure after claim 1 or 2 , the reference measurement being carried out when a temperature distribution in the vicinity of the electrical conductor (2) is static and homogeneous. procedure after claim 3 , It being determined using a predetermined criterion (S 1) whether the temperature distribution in the vicinity of the electrical conductor (2) is static and homogeneous. procedure after claim 4 , whereby to determine whether the temperature distribution in the area surrounding the electrical conductor (2) is static and homogeneous, a temporal development of the temperature in the area surrounding the electrical conductor (2) and/or a temporal course of a current through the electrical conductor (2 ) are taken into account. procedure after claim 5 , it being determined that the temperature distribution in the vicinity of the electrical conductor (2) is static and homogeneous if a period of time during which no current flows through the electrical conductor (2) exceeds a predetermined threshold value. procedure after claim 5 or 6 , wherein self-heating of the electrical conductor (2) is calculated on the basis of the course of the current through the electrical conductor (2) over time, and it is determined that the temperature distribution in the vicinity of the electrical conductor (2) is static and homogeneous, if a Self-heating of the electrical conductor (2) falls below a predetermined threshold. Method according to one of the preceding claims, in which the reference measurement is carried out repeatedly during operation of the actuator (1). Method according to one of the preceding claims, in which the actuator (1) is a motor and the electrical conductor (2) is a coil of the motor. actuator (1), with an electrical conductor (2); a temperature sensor (3) which is designed to measure a temperature in an area surrounding the electrical conductor (2); a resistance sensor (4) which is designed to measure a resistance value of the electrical conductor (2); and a computing device (5) which is designed to to determine at a first point in time a temperature measured by the temperature sensor (3) in the vicinity of the electrical conductor (2) as a reference temperature and to determine a resistance value of the electrical conductor (2) measured by the resistance sensor (4) as a reference resistance value, and determining a temperature of the electrical conductor (2) at a second point in time, using the reference temperature, the reference resistance value and a resistance value measured by the resistance sensor (4) at the second point in time.

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