Method and device for determining a sensor signal

Abstract

The present invention relates to the determining of a sensor signal. For example, an enveloping waveform of the signal from a rotational angle sensor can be reconstructed for this purpose. To this end, a predefined number of successively sampled values of a signal from a rotational angle sensor are multiplied with the elements of a weighting vector. On the basis of a measurement vector weighted in this way, an enveloping waveform of a signal curve from a rotational angle sensor can then be determined and, therefrom, a phase angle can be calculated.

Claims

1. An apparatus for determining a sensor signal, the apparatus comprising: a recording device that is designed to record a measurement signal at a predetermined sampling rate, wherein the measurement signal comprises two measurement signals phase-shifted relative to one another; a memory that is designed to store a plurality of successive sampled measurement signals; a weighting device that is designed to multiply a measured value vector having the plurality of stored measurement signals by a predetermined weighting vector and to output the result as a weighted measured value vector, wherein the weighting device multiplies the two measurement signals by the weighting vector; and a computation device that is designed to compute the sensor signal based on the weighted measured value vector, wherein the computation device carries out the computation of the sensor signal using the two weighted measurement signals.

2. The apparatus as claimed in claim 1, wherein the weighting vector is customizable.

3. The apparatus as claimed in claim 1, further comprising a synchronization apparatus that is designed to customize elements of the weighting vector based on a phase angle of the sampled measurement signal.

4. The apparatus as claimed in claim 1, wherein the computation device is designed to sum elements of the weighted measured value vector and to carry out the computation of the sensor signal using the summed elements of the measured value vector.

5. The apparatus as claimed in claim 1, wherein the weighting device is designed to select the weighting vector from a plurality of stored weighting vectors.

6. The apparatus as claimed in claim 1, wherein the recording device is designed to record the measurement signal of a phase angle from a rotation angle sensor at the predetermined sampling rate.

7. A drive system, comprising: an electrical machine that is coupled to a driveshaft; a rotation angle sensor that is coupled to the driveshaft and that is designed to provide a measurement signal corresponding to the angular position of the driveshaft; and an apparatus for processing a sensor signal having a recording device that is designed to record the measurement signal at a predetermined sampling rate; a memory that is designed to store a plurality of successive sampled measurement signals; a weighting device that is designed to multiply a measured value vector having the plurality of stored measurement signals by a predetermined weighting vector and to output the result as a weighted measured value vector; and a computation device that is designed to compute a sensor signal based on the weighted measured value vector.

8. The drive system as claimed in claim 7, wherein the rotation angle sensor comprises a resolver.

9. The drive system as claimed in claim 7, wherein the electrical machine is one from a group consisting of: a permanently excited synchronous machine, an electrically excited synchronous machine, and an asynchronous machine.

10. The drive system as claimed in claim 7, wherein the drive system and the electrical machine are part of an electric vehicle.

11. A method for determining a sensor signal, comprising: recording a measurement signal at a first sampling rate, wherein the measurement signal comprises two measurement signals phase-shifted relative to one another; storing the sampled value of the measurement signal; multiplying a predetermined number of stored sampled values of the measurement signal by a weighting vector, wherein the multiplying comprises a multiplication of the two measurement signals by the weighting vector, and a weighted measured value vector is output; and computing the sensor signal using the sum of the products of the stored sampled values and the weighting vector, wherein the computation of the sensor signal is carried out using the two weighted measurement signals.

12. The method as claimed in claim 11, further comprising synchronizing the weighting vector based on a phase angle of the sampled value of the measurement signal.

13. The method according to claim 11, wherein the recording of the measurement signal is of a phase angle from a rotation angle sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1: shows a schematic depiction of an electrical drive system according to an embodiment;

(3) FIG. 2: shows a schematic depiction of an apparatus for determining a phase angle according to an embodiment; and

(4) FIG. 3: shows a schematic depiction of a flowchart as forms the basis for a method according to an embodiment.

DETAILED DESCRIPTION

(5) FIG. 1 shows a schematic depiction of an electrical drive system according to an embodiment. An electrical machine 3 is supplied with power by an electrical energy source 5 via a converter 4. By way of example, the electrical energy source 5 may be a traction battery of an electric vehicle. The electrical machine 3 may be a permanently excited synchronous machine, an electrically excited synchronous machine or else an asynchronous machine, for example. Fundamentally, other electrical machines are also additionally possible. The embodiment of a three-phase electrical machine 3 depicted here was just one exemplary embodiment in this case. Furthermore, electrical machines having a different number of phases than three are also possible. The converter 4 converts the electrical energy provided by the electrical energy source 5 and provides the converted electrical energy for actuating the electrical machine 3. The electrical machine 3 can in this case be actuated based on stipulations or control signals from the control apparatus 1. Furthermore, when the electrical machine 3 is slowed down, it is also possible for kinetic energy to be converted into electrical energy by the electrical machine 3 and for this electrical energy to be supplied to an electrical energy store of the energy source 5 via the converter 4.

(6) Regulation of a permanently or electrically excited synchronous machine now requires knowledge of the position of the rotor in this machine. Further, regulation of asynchronous machines requires knowledge of the electrical frequency of such a machine. To this end, the electrical machine 3 can be coupled to a rotation angle sensor 2. By way of example, the rotation angle sensor 2 can be coupled to the drive axis of the electrical machine 3. By way of example, for determining the rotor position and/or the electrical frequency of the machine 3, sensors based on the Eddy current effect, digital angle sensors or what are known as resolvers are possible.

(7) In a resolver, a housing normally has two stator windings having a 90 electrical offset arranged in it that enclose a rotor with a rotor winding that is mounted in the housing. Fundamentally, various alternatives for ascertaining the angular position are possible, one possibility from which is described by way of example below. By way of example, the rotor winding of the resolver can be excited using a sinusoidal AC voltage. The amplitudes of the voltages induced in the two stator windings of the resolver are now dependent on the angular position of the rotor and are related to the sine and the cosine of the angular position of the rotor. It is therefore possible for the angular position of the rotor to be computed from the arctangent (arctan) to the signals of the two stator windings of the resolver.

(8) The resolver is now excited using a carrier signal. The carrier signal is typically sinusoidal, but may also have other signal forms. The output signal delivered by the resolver is amplitude-modulated signals whose envelopes include the information about the rotor position. The aim of an angle computation is therefore to determine the rotor position (the phase angle) from the amplitude-modulated output signals of the resolver.

(9) FIG. 2 shows a schematic depiction of an apparatus for determining a phase angle according to an embodiment. The signals 10-1 and 10-2 of the resolver are first of all supplied to a sampling apparatus 10 in this case. The sampling apparatus 10 may be an analog-to-digital converter, for example. The sampling apparatus 10 samples the signals of the resolver at a prescribed, normally constant, sampling rate. The sampled values are then first of all buffer-stored in a memory 20 for further processing. The memory 20 may be a cyclic memory, for example, that stores a predetermined number of sampled values. When a further value is written in, the respective oldest stored value is now overwritten. Other memory types are likewise possible, however. By way of example, the memory 20 can store ten respective sampled measured values for each sampled signal. A different number of sampled measured values for each sampled signal is furthermore likewise possible. A weighting device 30 further stores a weighting vector. The weighting vector may be firmly stored in the weighting apparatus 30 in this case. Alternatively, it is also possible for the weighting vector to be able to be overwritten or altered by an external apparatus (not depicted here). Further, the weighting apparatus 30 can also comprise a memory that stores a plurality of different weighting vectors. In this case, one of the plurality of stored weighting vectors can be selected for the further processing based on predetermined parameters. Fundamentally, it is also possible for the weighting vector to be dynamically customized based on received further parameters or sensor signals.

(10) Depending on the parameterization of the weighting vector, the weighting vectors can simulate even already known methods for reconstructing the envelope of the signal profile from the output signals of an angular position sensor. Some examples of possible weighting vectors and their corresponding method are reproduced below in this regard. In this case, the chosen number of ten elements for the weighting vector serves merely to improve comprehension and is not intended to be a restriction for the number of elements for a weighting vector.

(11) a=[0 0 1 0 0 0 0 0 0 0] max method

(12) a=[0 0 0 0 0 0 01 0 0] min method

(13) a=[0 0 0 1 0 0 01 0 0] min/max method

(14) a=[1 1 1 1 111111] integration method

(15) a.sub.i=sin(i/10*2*) where i=0.9 coherent demodulation with moving average as low-pass filter

(16) Furthermore, depending on the application, arbitrary further weighting vectors a are likewise possible. In particular, the use of point symmetrical weighting vectors allows a possible DC component (offset) to be suppressed during measurement of the signals from the rotation angle sensor. Further, it is also possible for offline customization to be effected, particularly when there is a nonsinusoidal excitation signal for the rotation angle sensor, by customizing the elements of the weighting vector. If disturbances (for example disturbance peaks) are furthermore detected in the signals from the rotation angle sensor, for example, then the applicable weighting vector can also be individually customized to such a detected disturbance signal online. This allows a detected disturbance signal to be rejected, for example. By way of example, when the switching times of power electronics in the surroundings of the rotation angle sensor are known, a disturbance caused by these switching processes can be suppressed. Furthermore, it is also possible for customization of the elements of the weighting vector to already attain a desired filter property for the signal processing.

(17) As already mentioned previously, the chosen number of ten elements for the weighting vector is intended to be understood only by way of example. In particular, the number of elements of the weighting vector can be customized in this case to the available computation capacity of the overall system.

(18) The weighting device 30 customizes the weighting vector a to the further constraints if need be and then multiplies a respective element of the weighting vector by an element of a measured value vector that is formed from the plurality of sampled angle signals stored in the memory 20. In this case, the measured value vector has the same number of elements as the weighting vector. The result obtained for this multiplication is therefore a weighted measured value vector.

(19) Based on this weighted measured value vector, the enveloping signal profiles of the signals provided by the rotation angle sensor are then determined by summation of all the elements of the weighted measured value vector and computation of the phase angle corresponding thereto. The phase angle can be computed in this case based on known or novel methods in a computation device 50.

(20) The method will be described once again in more detail below.

(21) In a first step, the last sample is first of all identified before the computation. In this step, the last sample is identified before a reference time in a computing grid. By way of example, this can be accomplished by virtue of the timestamp of the samples being compared with a timestamp of a reference time in the computing grid.

(22) Subsequently, synchronization is effected to orient the weights of the weighting vector. This requires a precise phase angle of the carrier in the excitation signal. For this synchronization, that is to say the ascertainment of the phase angle, a synchronization signal is now provided that can be obtained from the excitation signal read back or from the measurement signals, for example. This synchronization can be effected in a synchronization apparatus 40, for example.

(23) Against the background of the exact phase angle of the carrier in the excitation signals that have been ascertained during the synchronization, and possibly further criteria, such as detection of disturbances, for example, or the determination of switching times, it is then possible to ascertain a suitable weighting vector.

(24) The sampled measured values in the memory 20 are multiplied, as elements of a measurement vector, by the elements of the weighting vector, in each case on an element-by-element basis, and are subsequently summed.

(25) Subsequently, the enveloping waveform of the amplitude-modulated output signals of the rotation angle sensor is computed, and the phase angle is computed therefrom. For later dead-time compensation, it is furthermore possible for a dead time between the time at which the value of the enveloping waveform has been reconstructed and a reference time in the computing grid to be ascertained.

(26) FIG. 3 shows a depiction of a flowchart as forms the basis for a method for determining a sensor signal according to an embodiment.

(27) In step S1, one or more measurement signals are first of all sampled at a first sampling rate. Subsequently, in step S2, the sampled values are stored. As already described previously, a weighting vector can then be read or if need be computed and customized. Then, in step S3, a predetermined number of stored sampled values of the measurement signal is multiplied by the elements of the weighting vector. In step S4, the sensor signal is then computed using the product of the sampled values and the weighting vector.

(28) In summary, the present invention relates to the reconstruction of an enveloping waveform of a measurement signal to determine a sensor signal. By way of example, the signal of a rotation angle sensor (particularly a resolver) can be processed to reconstruct a rotor angle. To this end, a prescribed number of successive sampled values of a signal from a rotation angle sensor is multiplied by the elements of a weighting vector. Based on a measurement vector weighted in this manner, it is then possible for an enveloping waveform of a signal profile from a rotation angle sensor to be determined and for a phase angle to be computed therefrom.