Positioning device for producing a rotational position signal and an excitation device for producing an excitation signal for a resolver
A positioning device ( 101 ) for producing a position signal indicative of a rotational position of a resolver is presented. The positioning device comprises a signal interface ( 102 ) for receiving alternating signals (V_cos, V_sin) from the resolver and a processing system ( 103 ) for generating the position signal based on position-dependent amplitudes of the alternating signals and on polarity information indicative of a polarity of an excitation signal (V_exc) of the resolver. The processing system is configured to recognize a polarity indicator, such as a change of frequency or phase, on a waveform of one or both of the alternating signals and to determine the polarity information based on the recognized polarity indicator. Thus, the polarity information related to the excitation signal is included in the alternating signals and therefore there is no need for a separate signaling channel for transferring the polarity information to the positioning device.
1. A positioning device for producing a position signal indicative of a rotational position of a resolver, the positioning device comprising:
a signal interface configured to receive a first alternating signal (V_cos) and a second alternating signal (V_sin), amplitudes of the first and second alternating signals being dependent on the rotational position of the resolver so that envelopes of the first and second alternating signals have a mutual phase shift, and
a processing system configured to generate the position signal based on the amplitudes of the first and second alternating signals and on polarity information indicative of a polarity of an excitation signal of the resolver,
wherein the processing system is configured to:
recognize a polarity indicator related to the polarity of the excitation signal on a waveform of at least the first alternating signal, and
determine the polarity information based on the recognized polarity indicator.
2. The positioning device according to claim 1 , wherein the processing system is configured to recognize a change of phase or a change of frequency of the first alternating signal and to determine the polarity information based on the recognized change of phase or the recognized change of frequency.
3. The positioning device according to claim 2 , wherein the processing system is configured to constitute a zero-crossing detector for recognizing zero-crossings of the waveform of the first alternating signal to recognize the change of phase or the change of frequency.
4. The positioning device according to claim 1 , wherein the processing system is configured to compare the waveform of the first alternating signal to a predetermined waveform pattern and, in response to a match between the waveform of the first alternating signal and the predetermined waveform pattern, to determine the polarity information based on a part of the first alternating signal matching the predetermined waveform pattern.
5. The positioning device according to claim 1 , wherein the processing system is configured to recognize the polarity indicator on both the waveform of the first alternating signal and a waveform of the second alternating signal.
6. A converter for controlling voltages of a winding system of an electric machine, the converter comprising the positioning device according to claim 1 for producing the position signal indicative of the rotational position of the resolver connected to a rotor of the electric machine.
7. The converter according to claim 6 , wherein the converter further comprises an excitation device for producing an excitation signal for the resolver.
8. The converter according to claim 6 , wherein the converter is a frequency converter.
9. A method comprising:
receiving a first alternative signal and a second alternative signal from a resolver, amplitudes of the first and second alternating signals being dependent on a rotational position of the resolver so that envelopes of the first and second alternating signals have a mutual phase shift, and
generating a position signal indicative of the rotational position of the resolver based on the amplitudes of the first and second alternating signals and on polarity information indicative of a polarity of an excitation signal of the resolver,
wherein the method comprises:
recognizing a polarity indicator related to the polarity of the excitation signal on a waveform of at least the first alternating signal, and
determining the polarity information based on the recognized polarity indicator.