DE102015114860A1 - Method for operating a microcontroller - Google Patents

Abstract

The invention relates to a method of operating a microcontroller provided for controlling an actuator, comprising the method comprising: determining a cutoff current or a cutoff voltage (actually, the cutoff point is independent of the voltage.) It is only turned off due to a current value the maximum achievable current through the phase coil) taking into account at least one parameter representing a runtime previously completed by the actuator or a travel path traveled so far by an output shaft of the actuator, and / or a temperature of the actuator or a temperature in the vicinity of the actuator; and turning off the actuator if an input current or an input voltage of the actuator reaches or exceeds the turn-off current or cut-off voltage.

Description

The invention relates to a method for operating a microcontroller, which is provided for controlling an actuator.

To control the flap angle in air conditioning flaps or air inlets in vehicles usually actuators (actuators) are used, which consist of an electric motor and a downstream transmission. To protect the end stops and the blades from mechanical damage, the actuator must not exceed certain maximum torques. Otherwise, the actuator is switched off.

To control the actuator, a microcontroller is used, for example a microcontroller based on a controller architecture of the type 8051 from Intel.

The torque can be derived from the phase current of the motor and the gear ratio. If the microcontroller detects a phase current which corresponds to the predetermined maximum torque, then the microcontroller causes the shutdown.

The ratio of phase current and output torque can theoretically be assumed to be approximately constant for the invention. In practice, however, it has been found that the output torque is not proportional to the phase current, in particular due to temperature influences. Thus, the output torque in some cases can not be accurately determined from the measurement of the phase current. As a result, it may happen that the actuator is shut down too early, or generates a torque that is above the predetermined maximum. The latter case can lead to a reduction in the life of the operated actuators and / or the actuator.

The object of the present invention is to solve or mitigate this problem.

This object is achieved by the method specified in claim 1. Advantageous embodiments are specified in the subclaims.

According to the invention, a method is provided for operating a microcontroller provided for controlling an actuator, the method comprising: determining a cutoff current or a cutoff voltage taking into account at least one parameter representing a runtime previously completed by the actuator or a travel time taken by an output shaft of the actuator Running path, and / or a temperature of the actuator or a temperature in the vicinity of the actuator reproduces; and turning off the actuator if an input current or an input voltage of the actuator reaches or exceeds the turn-off current or cut-off voltage.

The present invention is based on the finding that, by taking into account a parameter which reflects an already completed running time or an already traveled running path of the actuator, a cut-off current can be determined which more precisely corresponds to the actually required turn-off torque. This applies analogously to the temperature in or on the actuator. Influences due to operating age or temperature influences can thus be largely eliminated. Thus, too early shutdown or vice versa overloading a actuated by the actuator actuator can be prevented and the life of the components used can be increased.

To shut off the actuator, the microcontroller can interrupt the input current or the input voltage or generate a shutdown signal. The shutdown can be done without delay. For example, the electric motor of the actuator can be brought to a predetermined Kommutierungsschema to a halt. For this purpose, for example, a fixed commutation scheme can be stored in a table. Such a fixed commutation scheme may for example describe a stop ramp so that the commutation frequency is continuously reduced. When the electric motor is at a standstill, it can then be provided that it is supplied with a holding current so that a holding torque acts on the rotor of the electric motor. Thus, the electric motor, or the actuator, hold its position after switching off.

The current temperature can be determined, for example, by a thermistor, for example an NTC resistor, in or on the actuator. Alternatively, other temperature sensors such as an NTC resistor or a measurement of the ohmic resistance of the phase winding to Temperature determination can be used. Likewise, an estimate of the temperature, for example by a state observer, may be implemented.

In some embodiments of the invention, a sensed temperature value or other sensed parameter is applied to an analog-to-digital converter (ADC). In the ADC, an averaging of the detected parameter can take place over time. Of course, an averaging of the at least one parameter can also be implemented differently and be carried out, for example, in a microcontroller.

In one embodiment, the at least one parameter indicates the runtime previously completed by the actuator or the travel path traveled by the output shaft of the actuator since the actuator was put into operation, in particular the first startup in a motor vehicle. It has been found that this parameter is a measure of the grease or lubricant distribution in the actuator, which in turn affects the torque.

In particular, the number of revolutions of the output shaft of the actuator is included, wherein the at least one parameter represents the number of revolutions previously completed by the output shaft of the actuator. The number of revolutions can be determined by means of a sensor which is arranged on the output shaft of the actuator. The number of revolutions is recorded cumulatively. The meter reading can be easily managed and processed by the microcontroller.

In one embodiment, the determination of the cut-off current or the cut-off voltage takes place dynamically and / or in real time. Thus, the influence of temperature changes, which may arise during operation, can be directly taken into account.

In one embodiment, the turn-off current or the turn-off voltage is determined by means of a polynomial formula. The calculation is done during the term. This refinement has the advantage that existing microcontrollers can be converted in a simple manner by depositing the formula and providing the current measured values needed to resolve the formula. Additional memory requirements on the part of the microcontroller results only to a limited extent.

The polynomial formula can be determined by approximating a map containing a plurality of measurements of the at least one parameter. In principle, a map of any dimension can be used. In particular, the map may also be three-dimensional or four-dimensional and contain a plurality of parameters. For example, the parameters may include one or more of the following: a runtime previously completed by the actuator, a track traveled by an output shaft of the actuator, a temperature of the actuator, or a temperature in the vicinity of the actuator, an input current, or an input voltage of the actuator , a torque generated by the actuator or an output force generated by the actuator, and a running time of the actuator. For example, a three-dimensional characteristic map may include the parameters temperature, current and torque.

In one embodiment, the plurality of measured values for a plurality of copies of the actuator are recorded, wherein the measured values are averaged over the number of copies. Thus, copy-dependent variations are reduced or eliminated.

The method is particularly suitable for an implementation in a microcontroller, which controls an actuator for actuating an actuating element in a motor vehicle, in particular air conditioning or ventilation flaps. The microcontroller may be a microcontroller having an 8051 controller architecture.

In an alternative embodiment, the switch-off current or the switch-off voltage is determined by means of a reference table. This refinement has the advantage that a simple adaptation of the turn-off behavior by changing reference values is made possible.

In addition, a data processing program is provided, comprising instructions that, when executed by a data processing system -. As a microcontroller - cause an implementation of the method described above.

Further features and advantages of the invention will become apparent from the following description in which reference is made to the accompanying drawings:

1 shows schematically a system for actuating an actuating element in a vehicle in which the method according to the invention can be used;

2 shows the sequence of a method according to an embodiment of the invention; and

3 FIG. 12 is a diagram illustrating a method of creating a momentum matrix according to a feature of an embodiment of the invention. FIG.

1 schematically shows a system for actuating an actuating element in a vehicle in which the inventive method can be used. The system includes a microcontroller 1 which provides an input current I _IN for an actuator 2 generated. Depending on the input current I _IN , the actuator generates an output torque M _AB on an output shaft, by means of which an actuating element, such as air conditioning or ventilation flaps in a motor vehicle, is actuated.

The generated output torque M _AB depends on the input current I _IN . If the input current I _{ON reaches} a value I _MAX , from which it is derived that an output torque which can not be exceeded is reached or exceeded, the microcontroller switches 1 the actuator 1 from. This process is in the flowchart in FIG 2 shown. One in the step 1 Applied input current I _ON is the one in step 3 certain turn-off current I _MAX in one step 5 compared. If it is determined there is the case I _IN > I _MAX , the actuator becomes 1 in one step 7 off. In particular, it may be provided that the electric motor is controlled brought to a standstill. After reaching the standstill, it may also be provided that the electric motor of the actuator is energized with a holding current, so that a loss of position is avoided. If in step 5 it is determined that the input current I _IN is greater than the cut-off current I _MAX, the process is again from step 1 proceeding starting.

When determining the switch-off current I _MAX , the operating time of the actuator and the ambient temperature are taken into account. Since these parameters are constantly changing, there is a dynamic adaptation of the switch-off current I _MAX .

The switch-off current I _MAX corresponds to a maximum permitted output torque. The determination of the current cut-off current I _MAX is effected in one embodiment of the invention by means of a reference table. The reference table contains a large number of values of temperature and transit time and the respective associated cut-off current I _MAX . These values are determined in advance by measurement. The table can be stored in a memory of the microcontroller.

In another embodiment, the turn-off current I _{MAX is determined} by means of an approximation function.

To determine the approximation function, various parameters of the actuator are measured at different operating conditions. For this purpose, the microcontroller of the actuator detects analog signals, such. As current and temperature with suitable sensors via analog-digital interfaces. The measured values are transmitted via a bus provided in the motor vehicle to which the microcontroller is connected, for. B. a LIN or CAN bus, transmitted to a computer provided for the evaluation.

With the help of the measurement data, a map is created, which contains the quantities current, temperature and moment.

To measure the internal actuator temperature, the temperature sensor of the motor driver electronics can be used. In order to obtain additional measured values from the ambient temperature, a further temperature sensor can be provided. By using two sensors, any dependencies between the internal actuator temperature and the ambient temperature can be taken into account.

In addition, the measurements can be repeated for several actuators of the same type.

To simplify the calculation of the mathematical approximation function, the measured values are sorted. For this purpose, the measured values are classified into a matrix of torque values, the row values being temperature-dependent and the column values being current-dependent.

The current axis is described by the variable x and the temperature axis by the variable y. To create the momentum matrix, a grid will be placed in the xy plane of all existing data points Measurement taken. The 3 shows the vertical view on the xy plane of the characteristic map of the recorded measured values. The grid width Δx is dependent on the set number of elements x _i elements and the minimum or maximum measured current value. The grid height Δy behaves analogously to the width Δx, but as a function of the temperature.

The function now searches all existing measuring points starting from the element x _i , y _i and extracts those which are in the range x _{i + 1} -x _i-1 , y _{i + 1} -y _i-1 (see the in 3 outlined area). For each of these points D _i the Euclidean distance δ _i to the point x _i , y _i is calculated as follows.

The maximum distance δ _max is composed as follows:

des Drehmomentes an der Stelle x_i, y_i zu berechnen, wird eine Summe über die z-Komponenten z_i aller Datenpunkte in dem vorgegebenen Bereich gebildet.To the value

of the torque at the location x _i , y _i , a sum is formed over the z components z _{i of} all the data points in the predetermined area.

Previously, the value is multiplied by a normalized weighting factor. The larger the distance δ _{i of} a point, the lower the value is in the total. The weighting factor g _i for each data point D _i is calculated as follows:

Finally, the calculated total is divided by the sum of the individual weighting factors.

an der Stelle x_i, y_i lautet:

The entire formula for calculating the value

at the point x _i , y _i is:

The described method was performed on the measurement results of each actuator.

From the generated maps, a mathematical function is then created, which maps the recorded map. As output map M The mean value of all recorded maps M _M is used for the approximation. Since the individual maps are in the form of matrices with the same number of rows and columns, the calculation of the mean value can be carried out easily.

For the mean M of all maps applies:

The output map M is used to determine a copy-independent approximation function. Instead of the arithmetic mean can be used to determine the output map M also the median, the root mean or a differently defined mean are calculated.

For the approximation of the output map, the following procedure is used. First, the output map is decomposed into individual two-dimensional maps. The number n of decompositions can be changed depending on the necessary approximation accuracy. The approximation of the respective maps is carried out by the Least Square method and provides the following equation: W (n) = b _{n, 1} * x ² + b _{n, 2} * x + b _{n, 3}

In order to determine the approximated, minimized function, in the implementation of the method of the least squares method described here, the approximation in the y direction is carried out over the course of the previously generated functions W (n). For this purpose, functions are again defined that depend on the coefficients b _n . Q ₁ = f (b _1,1 , b _2,1 ... b _{n, 1} ) = (c _1,1 · y ² + c _1,2 · y + c _1,3 ) Q ₂ = f (b _1,2 , b _2,2 ... b _{n, 2} ) = (c _2,1 · y ² + c _2,2 · y + c _2,3 ) Q ₃ = f (b _1,3 , b _2,3 ... b _{n, 3} ) = (c _3,1 · y ² + c _3,2 · y + c _3,3 )

The least squares method is now applied to these functions to obtain the parameters c _1,1 to c _3,3 .

Solving these equations with the least square method provides the solution for the approximation function: M (I, T) = c _1,1 · I ² · T ² + c _1,2 · I ² · T + c _1,3 · I ² + c _2,1 · I · T ² + c _2,2 · I · T + c _2.3 · I + c _3.1 · T ² + c _3.2 · T + c _3.3

The following table summarizes the procedure of the method for creating the approximation function:

The present invention is not limited to features of the described exemplary embodiments. In particular, methods of determination other than the abovementioned approximation methods can also be used for determining the characteristic diagram. Likewise, the output map M be determined in a variety of ways, not necessarily averaging must be provided. Alternatively, it can be provided that the measured values are transferred directly to a table without an approximation being made. The advantage of an approximation, however, is that you can also calculate values that lie between the measuring points or even outside the range of values of the measuring points. In addition, the approximation can be used to determine a closed formula that can be easily implemented on modern controller architectures, for example an ARM Cortex 32-bit ARM architecture.

Claims (13)

A method of operating a microcontroller provided to control an actuator, the actuator comprising an electric motor, the method comprising the steps of: Determining a switch-off current and / or a switch-off voltage taking into account at least one parameter representing a runtime previously completed by the actuator or a travel path traveled so far by an output shaft of the actuator, and / or a temperature of the actuator or a temperature in the vicinity of the actuator; and Turning off the actuator if an input current reaches or exceeds the cutoff current or if an input voltage of the actuator reaches or exceeds the cutoff voltage. The method of claim 1, wherein the at least one parameter reproduced by the actuator so far runtime or by the output shaft of the actuator hitherto traveled path since commissioning of the actuator. The method of claim 1 or 2, comprising: Detecting the number of revolutions of the output shaft of the actuator, wherein the at least one parameter represents the number of revolutions so far completed by the output shaft of the actuator. The method of claim 3, comprising: Determining the number of revolutions by means of a sensor disposed on the output shaft of the actuator; and Cumulative recording and saving of the number of revolutions. Method according to one of the preceding claims, wherein the temperature is determined by means of a sensor which is arranged in or on the actuator. Method according to one of the preceding claims, wherein the determination of the cut-off current or the cut-off voltage takes place dynamically and / or in real time. Method according to one of the preceding claims, wherein the cut-off current or the cut-off voltage is determined by means of a polynomial formula. The method of claim 7, wherein the polynomial formula is determined by approximating a map containing a plurality of measurements of the at least one parameter. The method of claim 8, wherein the map is at least three-dimensional and contains a plurality of measured values of parameters, the previously completed by the actuator runtime or by an output shaft of the actuator hitherto traveled path, a temperature of the actuator or a temperature in the environment Actuator, an input current or an input voltage of the actuator, and reproduce a torque generated by the actuator or an output force generated by the actuator. The method of claim 7 or 8, wherein the plurality of measured values each represent an average value for a plurality of copies of the actuator. Method according to one of claims 1 to 6, wherein the cut-off current or the cut-off voltage is determined by means of a reference table. Method according to one of the preceding claims, wherein the actuator is used to actuate an actuating element in a motor vehicle. Data processing program comprising instructions which, when executed by a data processing system, cause execution of the method according to any one of the preceding claims.

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