DE102011084299A1 - Method for testing drive circuit of brushless direct current motor utilized in motor car driven by heat engine, involves measuring current flowing through phase windings according to predetermined time - Google Patents

Abstract

The method involves comparing current with an expected current value based on applied voltage and a resistor of a set of phase windings. Tension or current vector is created in direction of a rotor layer of a rotor. The current flowing through the phase windings is measured according to predetermined time, where the predetermined time is selected in dependence of electrical and mechanical time constant of an electronic commutated synchronous machine (1). Averaging of the current value is performed by sequential measurements of the current. An independent claim is also included for an electronic control device.

Description

The invention relates to a method according to the preamble of claim 1 and an electronic control unit according to the preamble of claim 8.

Electronically commutated synchronous machines with a permanently excited rotor and a stator provided with phase windings, also known as a brushless DC motor, are increasingly being used in the automotive industry. An energization of the typically 3 stator windings generates a magnetic field in which the permanently excited rotor aligns itself. By suitable commutation of the currents flowing through the stator windings creates a rotational movement. In a widespread arrangement, the commutation is carried out using a determined with three stator-mounted Hall sensors rotor position. In automotive applications apply due to the possible personal injury strict safety guidelines that must be met by the control of an electric motor used for example as an actuator in a friction brake.

The EP 1683263 B1 describes a method for operating a synchronous machine with a permanent magnet rotor and a stator provided with phase windings, in which a determination of the rotor position is performed. To eliminate angular errors in determining the rotor position, at least one current and / or voltage vector with a defined time duration is fed in the direction of the determined rotor position in a load-less synchronous machine, whereby an orientation of the rotor is forced into the corresponding position.

For controlling the motor, it is necessary to know the currents flowing through the phase windings. Inaccurate or completely incorrect readings of the current affect the control and may lead to further errors or damage to the motor or the driven device.

It is therefore an object of the present invention to enable a check of the function of the current measuring devices of the phase windings.

This object is achieved by the method according to claim 1 and the electronic control device according to claim 8.

Thus, a method is provided in which the drive circuit of an electronically commutated synchronous machine is checked, wherein the measured current is compared with the expected based on the applied voltage and resistance of the phase winding. According to the invention, when the rotor is stationary, a voltage or current vector is applied in the direction of the rotor position, and after a predetermined time the current is measured through at least one phase winding.

In particular, the currents are measured through all phase windings.

This allows a direct plausibility of the relationship between the applied voltage and the measured current through the phase windings. Conveniently, a rectangular voltage vector is applied for a predetermined time. By making a direct comparison between current applied to the phase winding and current flowing through the phase winding, rotor position inaccuracies do not necessarily result in errors in the test. Furthermore, it is not necessary that the rotor is without load. The fact that the method according to the invention is carried out when the engine is at rest eliminates all errors based on dynamic effects.

It is advantageous if the predetermined time is selected as a function of the electrical and mechanical time constant of the synchronous machine.

It is expedient to carry out a plurality of successive measurements of the current, whereupon averaging takes place.

Preferably, a limitation of the currents through the stator windings, in particular by the applied voltage vector is limited by a pulse width modulation in the drive circuit. A pulse width modulated control of the phase windings is simple and inexpensive to carry out. By a suitable choice of the time of measurement and / or an averaging, a falsification of the result can be avoided.

The amplitude of the voltage vector is preferably between 1/6 and 2/3 of the supply voltage. Thus, even at a e.g. by a nearly discharged battery low supply voltage nor a sufficient voltage swing available, at the same time damage to the motor or the driven device is prevented by limiting the maximum torque output.

It is advantageous if, based on the measured current, a temperature of the phase winding is estimated as soon as the measured current lies within a predetermined interval. Thus, the only imprecisely measurable engine temperature can be calculated based on a model of the measured currents.

Appropriately, an error message is output and / or the drive circuit is deactivated when the measured current is outside a predetermined interval. Thus, an operation of the engine under load takes place only after error-free implementation of a method according to the invention, since then the current measurement was plausibility.

It is particularly expedient if the interval is selected as a function of data of a temperature sensor. Therefore, if a temperature sensor is present, the interval may be selected based on the expected resistance change of the phase winding and / or an expected change in the properties of other electronic components. The control circuit should work as well as possible in a temperature range of -40 ° C to + 150 ° C.

The invention also relates to an electronic control unit, which comprises a drive circuit for an electronically commutated synchronous machine and has a microprocessor, which performs a method according to at least one of the preceding claims, and in particular is connected to one or more analog-to-digital converters.

According to a preferred embodiment of the invention, the electronic control unit has means for controlling at least one solenoid valve. Thus, the controller can control both one or more engines and a hydraulic system.

According to a further preferred embodiment of the invention, the electronic control unit comprises means for performing a slip control and / or a vehicle dynamics control of a motor vehicle.

According to a preferred embodiment of the invention, the control device further comprises means for controlling or regulating the brakes of a motor vehicle, in particular it controls one or more electromechanical wheel brake (s).

It is advantageous if the electronic control unit contains a temperature sensor or is connected to a temperature sensor. Thus, the interval of expected currents can be suitably selected.

Conveniently, the electronic control unit includes at least one sense FET, i. a field effect transistor that can deliver a signal proportional to the useful current, or a shunt or a Hall sensor or a magnetoresistive sensor for current measurement. For example, the sense FET or the current-measuring component can be connected to an analog-to-digital converter of a microcontroller.

The invention further relates to the use of a control device according to the invention in a motor vehicle driven by a heat engine and / or an electric machine.

Further preferred embodiments will become apparent from the subclaims and the following description of an embodiment with reference to figures.

Show it

1 a schematic overview of an electronically commutated synchronous machine, and

2 a representation of the geometry of the engine.

As in 1 includes an electronically commutated synchronous machine 1 an electromechanical energy converter 2 , an electronic control device 3 and a rotor position encoder system 4 , In addition to use as a drive and use as a generator is possible, and thus mechanical motion is converted into electrical energy. The stator typically consists of 3 Phase windings, which are designated by U, V and W and meet in a neutral point S. In principle, a delta connection of the phase windings would also be possible. The permanently excited rotor is via a mounted rotor shaft R with a magnetic encoder wheel 7 connected. The magnetic field of the encoder wheel is from digital Hall sensors 6 sampled. These switch, for example, when they are in the field of a magnetic north pole, and do not conduct electricity when a magnetic south pole is directly adjacent. The information H1, H2, H3 typically 3 Hall sensors are powered by a circuit 8th processed to determine the rotor position. Based on the electrical angle, which was determined as the rotor position, determines a drive circuit 9 the to be applied to the strands U, V, W of the stator voltage vector and controls the semiconductor switches of the inverter bridge 5 accordingly. The inverter bridge 5 is equipped with current measuring devices which send their information to the drive circuit 9 send. A current measuring device can be realized, for example, in that a semiconductor switch of the inverter bridge is designed as a sense FET and connected to an analog-to-digital converter. The measurement with a shunt or an inductive measurement of the current with Hall sensor or magnetoresistive sensor is possible. The electronic control device can also be wholly or partially as by a microprocessor or Microcontroller executed program implemented. The three stator-fixed Hall sensors are mounted in such a way that, when the rotor rotates at a distance of 60 ° electrical angle, one sensor each changes its initial state, ie absolute electrical angles of 60 ° are obtained.

2 shows a schematic representation of the geometry of the motor, in which the stator fixed (α, β) coordinate system and the rotor fixed (d, q) coordinate system is located. The magnetic flux of the rotor points in the direction of the d-axis, and the axis of rotation passes vertically through the zero points of the two coordinate systems.

u_sd:

in d-Richtung angelegter Spannungsvektor

u_sq:

in q-Richtung angelegter Spannungsvektor

R_s:

Widerstand der Phasenwicklung

ω_e:

elektrische Drehgeschwindigkeit des Stators

Ψ_rd:

magnetischer Fluss des Rotors in d-Richtung

Ψ_rq:

magnetischer Fluss des Rotors in q-Richtung (nahezu 0)

In the (d, q) coordinate system are the classical electrodynamic equations u _sd = R _s * i _sd + d / dtΨ _rd - ω _e · Ψ _rq u _sq = R _s * i _sq + d / dtΨ _rq - ω _e · Ψ _rd With:

u _sd :

in the d-direction applied voltage vector

u _sq :

in the q-direction applied voltage vector

R _s:

Resistance of the phase winding

ω _e :

electrical rotation speed of the stator

Ψ _rd :

magnetic flux of the rotor in d-direction

_{Q rq} :

magnetic flux of the rotor in q-direction (almost 0)

When the engine is stationary, ω _e = 0, and furthermore d / dt Ψ _rd = 0 and d / dt Ψ _rq = 0.

Then the equations u _sd = R _s i i _sd u _sq = R _s * i _sq ie a voltage applied in the d-direction, ie along the magnetic flux of the rotor, causes only a current with the same orientation, thus producing no torque. Since the current is directly proportional to the applied voltage, the correct function of the phase winding including connections and the motor position sensor can be checked.

• 1. Prüfen, ob der Rotor in Ruhe ist
• 2. Anlegen einer Spannung in Richtung des magnetischen Flusses des Rotors (d-Richtung)
• 3. Prüfen, ob der Rotor (im Rahmen der vorliegenden Win kelauflösung) ruhend in seiner Lage geblieben ist
• 4. Messen des Stroms durch die Phasenwicklung(en)
• 5. Prüfen, ob der gemessene Strom innerhalb vorgegebener Grenzen liegt

The method according to the invention therefore preferably comprises the following steps:

• 1. Check if the rotor is at rest
• 2. Applying a voltage in the direction of the magnetic flux of the rotor (d-direction)
• 3. Check whether the rotor (in the context of the present win kelauflösung) has remained dormant in its position
• 4. Measuring the current through the phase winding (s)
• 5. Check that the measured current is within preset limits

Between the application of the voltage vector and the checking of the rotor position, one waits for a time period dependent on the mechanical (alignment of the rotor) and electrical (transient of the current) time constant.

Zur elektrischen Zeitkonstanten wird die mechanische Zeitkonstante addiert, welche z.B. von dem Trägheitsmoment des Rotors abhängig ist. Vorzugsweise wird die Summe mit einem vorgegebenen Faktor multipliziert, der insbesondere zwischen 3 und 5 liegt. Somit hat das aus Ansteuerschaltung und Phasenwicklung(en) bestehende System ausreichend Zeit, um sich einzuschwingen und eine statische Ruhelage zu erreichen. The electrical time constant τ is essentially calculated from the inductance L and the resistance R _{S of} the phase winding:

For the electrical time constant, the mechanical time constant is added, which depends, for example, on the moment of inertia of the rotor. Preferably, the sum is multiplied by a predetermined factor, which is in particular between 3 and 5. Thus, the drive circuit and phase winding (s) system has sufficient time to settle and reach a static rest position.

According to a preferred embodiment of the invention, the voltage vector is applied for a period of 25ms + -5ms before current measurement.

It is advantageous if the amplitude of the voltage vector is selected such that an effective voltage between 2.0 V and 5.0 V, in particular 3.0 V + -0.5 V, is applied to the phase winding. Thus, sufficient parking reserves are available so that fluctuations in the operating voltage (in automotive applications so 12 V) does not affect the measurement.

The range of possible or plausible currents depends on the positioning accuracy of the voltage or current vector. If one knows the inaccuracy of the pulse width modulation circuit determined by the limited resolution and tolerances of electronic components, as well as the possible fluctuations of the supply voltage or of the supply current, then the temperature-dependent current range can be determined. Thus, a defective circuit and / or phase winding is detected when the measured current is outside of an calculated based on the design parameters of the drive circuit and / or electrical machine interval.

Since the measured current depends essentially on the resistance of the phase winding, and the relationship between Temperature increase and resistance increase, for example, is very well known for copper, a temperature estimate can be made. If the connection is calibrated during production under controlled conditions and corresponding values stored in a non-volatile memory, a high degree of accuracy can be achieved.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1683263 B1 [0003]

Claims (12)

Method in which the drive circuit of an electronically commutated synchronous machine is checked, wherein the measured current is compared with the expected based on applied voltage and resistance of the phase winding, characterized in that when the rotor is stationary, a voltage or current vector is applied in the rotor position, and after a predetermined time the current through at least one phase winding, in particular all phase windings, is measured. A method according to claim 1, characterized in that the predetermined time is selected in dependence on electrical and mechanical time constant of the synchronous machine. A method according to claim 1 or 2, characterized in that a plurality of successive measurements of the current are carried out, whereupon an averaging takes place. Method according to at least one of the preceding claims, characterized in that the amplitude of the voltage vector is between 1/6 and 2/3 of the supply voltage. Method according to at least one of the preceding claims, characterized in that, based on the measured current, a temperature of the phase winding is estimated as soon as the measured current is within a predetermined interval. Method according to at least one of the preceding claims, characterized in that an error message is output and / or the drive circuit is deactivated when the measured current is outside a predetermined interval. A method according to claim 6, characterized in that the interval is selected in dependence on data of a temperature sensor. Electronic control device comprising a drive circuit for an electronically commutated synchronous machine, characterized by a microprocessor, which performs a method according to at least one of the preceding claims, and in particular with one or more analog-to-digital converters is connected. Electronic control unit according to claim 8, characterized in that this means for controlling or regulating the brakes of a motor vehicle, in particular one or more electromechanical wheel brake / n drives. Electronic control unit according to claim 8 or 9, characterized in that it contains a temperature sensor or is connected thereto. Electronic control unit according to at least one of claims 8 to 10, characterized in that it contains at least one sense FET or shunt or Hall sensor or magnetoresistive sensor for current measurement. Use of a control device according to at least one of claims 8 to 11 in a motor vehicle driven by a heat engine and / or an electric machine.

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