METHOD FOR CONTROLLING AN ELECTRIC MOTOR OF AN ELECTRIC DOOR DRIVE MOTOR AND DOOR DRIVE MOTOR

Description

[0001] The present invention relates to a method for determining the temperature of a motor winding of an electric motor, in particular an electric door drive motor, and a door drive. STATE OF THE ART

[0002] When electric motors are operated, the current flowing through the motor windings leads to heating of the windings, primarily due to ohmic losses. To prevent resulting overheating and potential damage to the electric motor, it is common practice to implement energy management based on the motor's temperature. If a critical temperature limit is at risk of being exceeded, this energy management system initiates temperature-reducing measures. In the case of an electric door drive motor, i.e., the motor driving an automatic door system, such temperature-reducing measures might include, for example, reducing the travel speed of the door leaves or increasing the door's holding time.

[0003] It is known in the art to determine the temperature of the motor windings of electric motors using suitably positioned temperature sensors. A disadvantage of using such temperature sensors is the inherent latency between the heating of the motor winding due to current application and the detection of this heating at the sensor location. Because of this latency, it is not possible to operate the electric motor at its power limit; rather, a certain power reserve must be maintained to prevent overheating of the motor winding. Furthermore, equipping an electric motor with temperature sensors disadvantageously increases its installation space, and this additional sensor system generally increases the complexity and susceptibility to failure of the electric motor.

[0004] FR 3 075 514 discloses a method for controlling an electric motor of an electric door drive motor, wherein the temperature of a winding of the motor is determined by measuring the electrical resistance of the winding. REVELATION OF THE INVENTION

[0005] It is therefore the object of the present invention to propose a method for controlling an electric motor of an electric door drive motor, wherein the method comprises a determination of the temperature of a motor winding of an electric motor which does not require the use of separate temperature sensors.

[0006] This problem is solved starting from a method according to the preamble of claim 1 in conjunction with the characterizing features. Advantageous embodiments of the invention are specified in the dependent claims.

[0007] The invention includes the technical teaching that the electrical resistance of the motor winding is determined as a measure of the temperature.

[0008] The invention is based on the idea of ​​determining the temperature directly within the motor winding itself. Due to its pronounced temperature dependence, electrical resistance is a suitable measure for this purpose, which is also easily accessible through measurement technology. In particular, the electrical resistance changes almost instantaneously with the temperature of the motor winding, so that an energy management system based on the method according to the invention does not need to take into account any latency in the temperature determination. When an electric motor is operating, a well-known electrical voltage is typically applied to the motor winding, and therefore, determining the flowing electric current is suitable for determining the electrical resistance of the motor winding.

[0009] Preferably, the electric motor is provided with at least one current-sensing resistor, wherein the determination of the electrical resistance of the motor winding is carried out by measuring the electric current flowing through the current-sensing resistor.

[0010] In detail, the method according to the invention, in an advantageous embodiment, comprises at least the following steps: Providing the electric motor with at least one current-sensing resistor, wherein the current-sensing resistor is connected in series with the motor winding, applying an electrical voltage to the motor winding and determining the current of the resulting electric current by measuring a voltage drop across the current-sensing resistor, determining the electrical resistance of the motor winding from the quotient of voltage to current, and determining the temperature of the motor winding by assigning the resistance to tabulated resistance-temperature value pairs.

[0011] The method is based on determining the current flowing through the motor winding when a known voltage is applied, and subsequently calculating the desired electrical resistance of the motor winding according to Ohm's law. For this purpose, the voltage drop across a current-sensing resistor is measured. This resistor is connected in series with the motor winding, ensuring that the same current flows through both the resistor and the winding. The temperature of the motor winding is determined from the electrical resistance by matching it to tabulated resistance-temperature value pairs, which are preferably obtained beforehand, ideally through a factory reference measurement.According to the invention, the temperature of the motor winding can thus be determined without the use of separate temperature sensors; rather, it is only necessary to integrate an additional current measuring resistor into the circuit of the electric motor.

[0012] Preferably, the tabulated resistance temperature value pairs are taken from a factory reference measurement, wherein the electric motor for the reference measurement is provided with at least one temperature sensor arranged in the area of ​​the motor winding and is arranged in a climate chamber, and wherein the reference measurement comprises a multiple performance of the following steps: Setting an ambient temperature in the climate chamber, measuring the temperature of the motor winding using the temperature sensor, applying an electrical test voltage to the motor winding and determining the current of the resulting electric current by measuring the voltage drop across the current measuring resistor, determining the electrical resistance of the motor winding from the quotient of test voltage to current, and forming a corresponding resistance-temperature value pair.

[0013] Such a reference measurement only needs to be performed once at the factory, and the resistance-temperature value pairs obtained can be stored, in particular, in a storage medium assigned to the electric motor. For example, when producing a large number of identical electric motors, it is not necessary to subject each individual unit to a reference measurement; rather, it may be sufficient to obtain the resistance-temperature value pairs from only one representative unit.

[0014] The invention further relates to a method for controlling an electric motor, in particular an electric door drive motor, wherein the electric motor comprises at least one motor winding, and wherein the method is geared towards energy management of the electric motor as a function of the temperature of the motor winding. According to the invention, the temperature of the motor winding is determined according to a method based on one of the aforementioned embodiments. The energy management protects the electric motor during operation from overheating and thus potential damage, and thanks to the accuracy of the method according to the invention for determining the motor winding temperature, the electric motor can be operated at its power limit by the controller.

[0015] According to the invention, the electric motor is provided as a brushless, permanent magnet DC motor with three motor phases, wherein each motor phase comprises a motor winding, and wherein the determination of the temperature is carried out for all motor phases together or for each motor phase individually.

[0016] For example, the temperature of a door drive motor is determined in an end position where the door leaf is at rest and pressed against a mechanical stop. The current flowing to the electric motor can be measured using a current-sensing resistor, allowing for the determination of a temperature averaged across all motor windings. However, the current flow to the individual motor phases varies depending on the rotor's position, so a corresponding inaccuracy in the temperature measurement must be taken into account.

[0017] According to the invention, the temperature is determined sequentially for each motor phase individually, whereby a test voltage is applied to each motor phase as a periodic, pulse-width modulated signal, the signal having a pulse-pause ratio of 1% to 20%. Such individual temperature determination offers the possibility of detecting the reaching of a critical limit temperature in each individual motor phase in the event of inhomogeneous heating of the electric motor, or of preventing this by means of energy management. In particular, a defective motor phase can also be identified in this way. In addition, a plausibility check can be carried out by comparing the determined temperature values ​​of the individual phases. When energizing the motor phases for the purpose of temperature determination, care must be taken to ensure that the rotor of the electric motor and the door driven by it are not set in motion by applying a test voltage.For this reason, the shortest possible pulse-pause ratio of the test signal must be selected, while the voltage pulses must be sufficiently long to ensure reliable current measurement across the current-sensing resistor. In the case of an electric door drive motor, the inertia of the associated door leaf must be overcome to initiate movement, and in practice, a pulse-pause ratio in the range of 1% to 20% has been identified as a suitable value range that ensures reliable current measurement without causing significant movement of the door leaf.

[0018] In a non-inventive example, the temperature can be determined for all motor phases simultaneously, whereby the commutation angle of the electric motor is set such that the rotor of the electric motor is not set into rotation. The commutation angle is defined as the angular position of the rotor within one magnetic period of the electric motor. The advantage of this example is that no rotor rotation takes place during the testing of the motor winding temperature, so that when used in a door drive motor, no jerking or other movement of a door leaf is to be expected. A temperature averaged over all motor phases is determined.

[0019] Advantageous embodiments of the method are specified in the dependent claims, the description, and the figures. Furthermore, the problem is also solved by a door drive according to independent claim 6. Advantageous embodiments of the door drive are likewise specified in the description and the figures. In particular, a door drive is protected with which the method according to the invention, especially the method according to any one of claims 1 to 5, can be carried out.

[0020] The invention further relates to a door drive, comprising at least an electric motor with at least one motor winding and a control unit for controlling the electric motor. According to the invention, the control unit has at least one current-sensing resistor connected in series with the motor winding, wherein the control unit is configured to measure a voltage drop across the current-sensing resistor and to control the electric motor according to a method according to one of the aforementioned embodiments.

[0021] In particular, the electric motor is designed as a brushless, permanent magnet DC motor with two motor halves, each comprising three motor phases with one motor winding each, and the control unit comprising two current-sensing resistors, each connected in series with one of the motor halves. Such a design with two independent motor halves is to be regarded as a redundant safety precaution.

[0022] Preferably, the door drive includes an ambient temperature sensor which allows the ambient temperature to be determined in addition to the temperature of the motor winding. Such an ambient temperature measurement may be necessary for energy management purposes in order to isolate an extrinsic component, such as that caused by solar radiation, from the measured temperature of the motor winding. PREFERRED EXAMPLE OF THE INVENTION

[0023] Further measures improving the invention are described in more detail below together with a description of a preferred embodiment of the invention with reference to the figure.

[0024] The figure shows a schematic representation of a door drive 100 according to the invention comprising the electric motor 1 with the three motor phases 1a, 1b, 1c and the control unit 20 for controlling the electric motor 1.

[0025] The electric motor 1 is designed as a brushless, permanent magnet DC motor, wherein the depicted motor phases 1a, 1b, 1c with their respective motor windings 11a, 11b, 11c constitute the stator, and the rotor (not shown here) is equipped with permanent magnets. In particular, the electric motor 1 can consist of two redundant motor halves, although for the sake of clarity only one motor half is shown here. Each of the three motor phases 1a, 1b, 1c has two coils, which together form one motor winding 11a, 11b, 11c. The three motor phases 1a, 1b, 1c are connected in a star configuration at a central star point and can be energized via the control unit 20.

[0026] The control unit 20 comprises the controller 21, the current-sensing resistor 2, and the output stage 22. The current-sensing resistor 2 is connected between the voltage source 4 and the output stage 22 and is therefore in series with all motor windings 11a, 11b, 11c.

[0027] The controller 21 is designed to measure the voltage drop across the current-sensing resistor 2 and, based on this, to calculate the current and the electrical resistance of the respective energized motor windings 11a, 11b, 11c. For a given voltage U and a current determined by means of the current-sensing resistor 2, the total electrical resistance of the electric motor 1 is determined using Ohm's law as Rtotal = UIIThe motor windings 11a, 11b, 11c represent the largest contribution to the total resistance and, in particular, to its dependence on the motor winding temperature T, so that the desired resistance of the motor windings 11a, 11b, 11c is determined to be R winding ( T ) = R in total ( T ) - R Rest. The previously known constant RThe remaining value sums all remaining contributions such as leads, connectors, and power electronics and is simplified, for example, as being temperature-independent. According to the invention, the resistance of the respective motor winding 11a, 11b, 11c determined in this way is then compared with previously known resistance-temperature value pairs, which are stored, for example, in a memory unit of the controller 21, to determine the temperature. The temperature of the motor windings 11a, 11b, 11c determined in this way serves the control method according to the invention for carrying out the energy management of the electric motor 1 during operation of the door drive 100.

[0028] In examples not according to the invention, the determination of the motor winding temperature can be carried out for all motor phases 1a, 1b, 1c jointly, i.e. averaged, or according to the invention sequentially for each motor phase 1a, 1b, 1c individually.

[0029] An average measurement is preferably performed in an end position of the door drive 100, in which the electric motor 1 is energized to press the associated door leaf against a mechanical end stop. In this case, no separate test voltage is applied; instead, the temperature determination according to the invention is carried out in the already energized operating mode. This has the advantage that no separate test sequences need to be performed for the temperature determination, during which the associated door system would have to be put into a corresponding test mode and, for example, would not be able to be opened or closed.However, the described procedure is disadvantageous because, depending on the position of the rotor in the end position of the door drive 100, there may be an uneven current supply to the individual motor phases 1a, 1b, 1c; for example, one of the motor phases 1a, 1b, 1c may be completely without current, so that uneven heating of the motor phases 1a, 1b, 1c may occur.

[0030] According to the invention, the motor phases 1a, 1b, 1c are sequentially energized in pairs by applying a test voltage. For example, a test current flows into motor phase 1a and out of motor phase 1b while motor phase 1c remains de-energized. The resistance of each individual motor phase 1a, 1b, 1c is then calculated from the three resistances of the motor phase pairs obtained in this way using linear algebra. The measurement of the different combinations can also be carried out with a time delay, distributed over several operating cycles of the door drive 100, for example, with intervening door opening or closing operations, in order to interrupt the normal operating mode of the door system only for the shortest possible time. To prevent unwanted starting of the electric motor 1 as far as possible, test voltages in the form of periodic, pulse-width modulated signals with a low pulse-pause ratio of 1% to 20% are applied to the motor phases 1a, 1b, 1c for the measurement.

[0031] In a further embodiment of the method according to the invention, when determining the motor winding temperature, the phase angle of the test voltage signals applied to the motor phases 1a, 1b, 1c is controlled such that the commutation angle of the electric motor 1 is such that the rotor is not set in motion. The control of the motor phases 1a, 1b, 1c by the control unit 20 must therefore be designed, depending on the rotor position, such that no significant torque acts on the rotor, which is the case at a commutation angle of approximately 0° and 180°. The advantage of this measuring principle is that the door drive 100 is not stimulated to any movement, so that the temperature determination can be carried out completely unnoticed by users of the associated door system.

[0032] The door drive 100 shown in the figure further comprises the ambient temperature sensor 3, by means of which the ambient temperature in the respective installation situation of the door drive 100 can be determined. For example, direct sunlight can result in an increased base temperature of the electric motor 1, which is included as an offset in the determination of the motor winding temperature according to the invention and may have to be taken into account in the energy management of the electric motor 1. In addition, a temperature determined by means of the ambient temperature sensor 3 can serve as a reference value with which a motor winding temperature determined by means of the method according to the invention in the "cold" state of the electric motor 1, i.e., for example, after a period of several hours since the last actuation of the door drive 100, can be compared. Reference symbol list

[0033] 100 Door drive 1 Electric motor 1a, 1b, 1c Motor phase 10 Brushless, permanent magnet DC motor 11a, 11b, 11c Motor winding 2 Current measuring resistor 20 Control unit 21 Controller 22 Power stage 3 Ambient temperature sensor 4 Voltage source

Claims

1. A method for controlling an electric motor (1) of an electric door drive motor, wherein the electric motor (1) comprises at least one motor winding (11a, 11b, 11c), and wherein the method is orientated towards energy management of the electric motor (1) as a function of the temperature of the motor winding (11a, 11b, 11c), wherein the electrical resistance of the motor winding (11a, 11b, 11c) is determined as a measure of the temperature in order to determine the temperature of the at least one motor winding (11a, 11b, 11c), wherein the electric motor (1) is provided as a brushless, permanently excited direct current motor (10) with three motor phases (1a, 1b, 1c), wherein each motor phase (1a, 1b, 1c) comprises a motor winding (11a, 11b, 11c), characterised in that the determination of the temperature is carried out sequentially for each motor phase (1a, 1b, 1c) individually, wherein a test voltage for each motor phase (1a, 1b, 1c) is applied as a periodic, pulse-width-modulated signal, wherein the signal has a pulse-pause ratio of 1% to 20%, whereby when the motor phases (1a, 1b, 1c) are energised for the purpose of determining the temperature, care is taken to ensure that the rotor of the electric motor and the door driven thereby are not set in motion by the application of the test voltage.

2. The method according to claim 1, characterised in that the electric motor (1) is provided with at least one current measuring resistor (2), wherein the electrical resistance of the motor winding (11a, 11b, 11c) is determined on the basis of a measurement of the electrical current flowing through the current measuring resistor (2).

3. The method according to claim 1 or 2, at least having the following steps: - Providing the electric motor (1) with at least one current measuring resistor (2), wherein the current measuring resistor (2) is connected in series with the motor winding (11a, 11b, 11c), - Applying an electrical voltage to the motor winding (11a, 11b, 11c) and determining the current strength of the resulting electrical current by measuring a voltage drop across the current measuring resistor (2), - Determining the electrical resistance of the motor winding (11a, 11b, 11c) from the quotient of voltage to current strength, and - Determining the temperature of the motor winding (11a, 11b, 11c) by assigning the resistance to tabulated resistance-temperature value pairs.

4. The method according to one of claims 1 to 3, characterised in that the tabulated resistance-temperature value pairs are taken from a factory reference measurement.

5. The method according to one of the preceding claims, characterised in that the electric motor (1) for the reference measurement is provided with at least one temperature sensor arranged in the region of the motor winding (11a, 11b, 11c) and is arranged in a climatic chamber, and wherein the reference measurement comprises the following steps being carried out multiple times: - Setting an ambient temperature in the climatic chamber, - Measuring the temperature of the motor winding (11a, 11b, 11c) by means of the temperature sensor, - Applying an electrical test voltage to the motor winding (11a, 11b, 11c) and determining the current strength of the resulting electrical current by measuring the voltage drop across the current measuring resistor (2), - Determining the electrical resistance of the motor winding (11a, 11b, 11c) from the quotient of test voltage to current strength, and - Forming a corresponding resistance-temperature value pair.

6. A door drive (100) at least comprising an electric motor (1) with at least one motor winding (11a, 11b, 11c) and a control unit (20) for controlling the electric motor (1), wherein the control unit has at least one current measuring resistor (2) which is connected in series with the motor winding (11a, 11b, 11c), wherein the control unit is configured to measure a voltage drop across the current measuring resistor (2) and to carry out control of the electric motor (1) in accordance with a method according to one of claims 1 to 5.

7. The door drive (100) according to claim 6, characterised in that the electric motor (1) is in the form of a brushless, permanently excited direct current motor (10) with two motor halves, wherein each motor half comprises three motor phases (1a, 1b, 1c) each with a motor winding (11a, 11b, 11c), and wherein the control unit (20) comprises two current measuring resistors (2) which are each connected in series with one motor half.

8. The door drive (100) according to claim 6 or 7, characterised in that the door drive (100) comprises an ambient temperature sensor (3), by means of which the ambient temperature can additionally be determined when determining the temperature of the motor winding (11a, 11b, 11c).