Method and circuit for detecting a short circuit of the sine or cosine receiver coil of a resolver

Abstract

A method for detecting a short circuit to ground or to the operating voltage of a signal line (11, 12) of a resolver (16) has the following steps: measuring the potential of the signal lines (13a, 13b; 14a, 14b) of the receiver coil (18) with respect to ground at two sampling times (R and F) provided symmetrically at the middle of the excitation period; calculating an offset value for a signal line pair (13a, 13b; 14a, 14b) by calculating the average value of the four measured values (U.sub.HR, U.sub.LR, U.sub.HF and U.sub.LF) for the associated receiver coil (17, 18); and identifying a short circuit and the potential to which the short-circuited line is connected in that the offset value is compared to threshold values.

Claims

1. A method for detecting a short circuit (10) to ground or to the operating voltage (UB) of a signal line (11, 12) of a resolver (16), having the following steps: measuring (31) the potential of the signal lines (13a, 13b; 14a, 14b) of the receiver coil with respect to ground at two sampling instants (R, F) which are situated symmetrically with respect to the midpoint of the excitation period; calculating (32) an offset value (UDC) for the respective signal line pair (13a, 13b; 14a, 14b) by forming the average of the four measured values (UHR, ULR, UHF, ULF) of the respective receiver coil (17, 18); and identifying (33) a short circuit and the potential toward which the short-circuited line is able to be pulled, by comparing the offset value to limit values.

2. The method as claimed in claim 1, wherein pull-up resistors (R1; R3) and pull-down resistors (R2; R4) which are connected to the signal lines (13a, 13b; 14a, 14b) are supplied with a voltage potential via their other end.

3. The method as claimed in claim 2, wherein the voltage potentials of the pull-up resistors (R1; R3) and the pull-down resistors (R2; R4) differ from one another by a constant amount which is smaller than the measurement range of the A/D converters for the measured values of the receiver coil.

4. A circuit for detecting a short circuit of a signal line (11, 12) of a resolver (16) to ground or to the operating voltage (UB), including: a control device (1) including a processor (2), power stages (3, 4) and first terminals (6, 7) for providing signals for excitation lines (11, 12) to an excitation coil (16) of the resolver (15), and second terminals (7a, 7b, 8a, 8b) for connecting signal lines (13a, 13b, 14a, 14b) for the signals of a sine coil and a cosine coil (17, 18); two A/D converters (21, 22) which are connected to the second terminals (7a, 7b and 8a, 8b) of the control device (1), the outputs of which being readable and evaluable by the software of the processor (2); the excitation lines (11, 12) which couple the first terminals (5, 6) of the excitation coil (16) to the resolver (15); the signal lines (13a, 13b, 14a, 14b) which are to be diagnosed for the sine and cosine signals provided by the resolver (15), and which couple the resolver to the two terminals (7a, 7b, 8a, 8b) of the control device (1); pull-up resistors (R1, R3) which are connected via their one end to one of the terminals (7a, 8a) for the conductors (13a, 14a) sine coil (17) and of the cosine coil (18), and via their other end to a first DC voltage potential (UH); pull-down resistors (R2 and R4) which are connected via their one end to the other one of the terminals (7b, 8b) for the lines (13b, 14b) sine coil (17) and of the cosine coil (18), and which are connected via their other end to a second DC voltage potential (UL); four electronic switches (26, 27, 28, 29) which are inserted into the connection of the terminals (7a, 7b; 8a, 8b) for the signal lines (13a, 13b; 14a, 14b) to inputs (H, L) of the A/D converters (21, 22), wherein the switches (26, 27, 28, 29) are configured such that they respectively disconnect one input of the A/D converter (21, 22) from the signal line (13a, 13b; 14a, 14b) and temporarily connect this input to ground; and a display and/or storage device (9) for displaying and/or storing the information identified by the processor (2), into which the positive detection of a short circuit (10) of a signal line (11, 12) of a resolver (16) to ground or to the operating voltage (UB) by the processor (2) is incorporated.

5. The circuit as claimed in claim 4, wherein the pull-up resistors (R1 and R3) and pull-down resistors (R2 and R4) are integrated into the control device (1).

6. The circuit as claimed in claim 4 or 5, wherein the resistance values of the pull-up resistors (R1 and R3) and pull-down resistors (R2 and R4) are large relative to the ohmic resistance of the sine coil (17) and the cosine coil (18).

7. A circuit for detecting a short circuit of a signal line (11, 12) of a resolver (16) to ground or to the operating voltage (UB), including: a control device (1) including a processor (2), power stages (3, 4) and first terminals (6, 7) for providing signals for excitation lines (11, 12) to an excitation coil (16) of the resolver (15), and second terminals (7a, 7b, 8a, 8b) for connecting signal lines (13a, 13b, 14a, 14b) for the signals of a sine coil and a cosine coil (17, 18); two A/D converters (21, 22) which are connected to the second terminals (7a, 7b and 8a, 8b) of the control device (1), the outputs of which being readable and evaluable by the software of the processor (2); the excitation lines (11, 12) which couple the first terminals (5, 6) of the excitation coil (16) to the resolver (15); the signal lines (13a, 13b, 14a, 14b) which are to be diagnosed for the sine and cosine signals provided by the resolver (15), and which couple the resolver to the two terminals (7a, 7b, 8a, 8b) of the control device (1); pull-up resistors (R1, R3) which are connected via their one end to one of the terminals (7a, 8a) for the conductors (13a, 14a) sine coil (17) and of the cosine coil (18), and via their other end to a first DC voltage potential (UH); pull-down resistors (R2 and R4) which are connected via their one end to the other one of the terminals (7b, 8b) for the lines (13b, 14b) sine coil (17) and of the cosine coil (18), and which are connected via their other end to a second DC voltage potential (UL); four additional A/D converters in which one input is set to ground, and the other inputs are connected to one of the terminals (7a, 7b, 8a, 8b) for the signal lines (13a, 13b, 14a, 14b) of the sine coil (17) and the cosine coil (18); and a display and/or storage device (9) for displaying and/or storing the information identified by the processor (2), into which the positive detection of a short circuit (10) of a signal line (11, 12) of a resolver (16) to ground or to the operating voltage (UB) by the processor (2) is incorporated.

8. The circuit as claimed in claim 7, wherein the pull-up resistors (R1 and R3) and pull-down resistors (R2 and R4) are integrated into the control device (1).

9. The circuit as claimed in claim 7, wherein the resistance values of the pull-up resistors (R1 and R3) and pull-down resistors (R2 and R4) are large relative to the ohmic resistance of the sine coil (17) and the cosine coil (18).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a circuit according to one exemplary embodiment of the present invention;

(2) FIG. 2 schematically describes the steps for carrying out the method, according to one exemplary embodiment of the present invention; and

(3) FIG. 3 describes the temporal development of the potential of the signal lines.

DETAILED DESCRIPTION

(4) FIG. 1 focuses on the control device 1 for the resolver 15, it being possible to integrate said control device into the control unit for a vehicle (not depicted here). Said control device includes (or shares the use of) a processor 2 which monitors the correct operation of all resolver functions which are to be controlled, and also displays malfunctions if needed.

(5) The control device 1 in particular controls the power stages 3 and 4 for providing the sinusoidal excitation signal for the excitation coil 16 of the resolver 15 to the first terminals 5 and 6. At the second terminals 7a, 7b and 8a, 8b, the signals of the sine coil 17 and the cosine coil 18, which represent the instantaneous angular position of the measured object (for example, the shaft of the motor), enter the control device 1 and may be further processed via software as a digital signal after conversion in the A/D converters 21 and 22.

(6) The resolver signal lines 13a, 13b, 14a, and 14b are the connection from the second terminals 7a, 7b and 8a, 8b of the control device 1 to the resolver 15, i.e., to its sine coil 17 and cosine coil 18. It is essential to monitor these lines for a short circuit 10, i.e., an undesirable connection to ground or to the operating voltage U.sub.B, as is indicated in FIG. 1 by the potential connections 10 represented by dashed lines.

(7) For performing the short-circuit diagnosis, the voltage profile of the individual signal lines to ground is evaluated, wherein the evaluation for the sine and cosine coils 17 and 18 is carried out in the same manner. For doing this, the signal lines must already have a defined potential without the occurrence of a short circuit. Pull-up resistors R.sub.1 and R.sub.3 are therefore used, which are connected via their one end to one of the terminals 7a, 8a for the lines 13a, 14a sine coil 17 and of the cosine coil 18, and via their other end to a first DC voltage potential U.sub.H; and pull-down resistors R.sub.2 and R.sub.4, which are connected via their one end to the other one of the terminals 7b, 8b for the lines 13b, 14b of the sine coil 17 and the cosine coil 18, and which via their other end to a second DC voltage potential U.sub.L. Corresponding to the resistor ratio, a voltage division results between U.sub.H and U.sub.L if the ohmic resistance of the receiver coils is small relative to that of the resistors R.sub.1, R.sub.2, R.sub.3, and R.sub.4.

(8) In order to measure the voltages to ground at the signal line connections to the A/D converters 21 and 22 for the resolver signal for the purpose of fault diagnosis, an electronic switch 23, 24, 25, and 26 may be inserted into each of the connections of the terminals 7a, 7b, 8a, and 8b for the signal lines 13a, 13b, 14a, and 14b to inputs H and L of the A/D converters 21, 22. These four switches are configured in such a way that they respectively disconnect an input of the A/D converter (21, 22) from the terminal 7a, 7b, 8a, and 8b for the signal lines 13a, 13b, 14a, and 14b, and temporarily connect this input to ground. Alternatively, instead of the switches, four additional A/D converters may be used (not depicted in FIG. 1), which is set to ground via one of their two inputs, while the other input is connected to one of the terminals 7a, 7b, 8a, and 8b for the signal lines 13a, 13b, 14a, and 14b.

(9) The measurement (31 in FIG. 2) of the potential, i.e., the voltage to ground, at the terminals 7a, 7b, 8a, and 8b of signal lines 13a, 13b, 14a, and 14b of the receiver coils 17 and 18, is carried out in that either the respective switch 26, 27, 28, or 29 is switched over for this sampling, or, in the case of the use of the alternative circuit, the respective corresponding additional A/D converter is queried. As FIG. 3 illustrates, the measurement takes place at two sampling instants R (or rise) and F (or fall) which are situated symmetrically with respect to the midpoint of the excitation period, wherein the one of the lines is designated by H (or high) and the other by L (or low).

(10) The calculation (32 in FIG. 2) of an offset value U.sub.DC is carried out via the resulting four measured values for each line pair 13a and 13b (or 14a and 14b), i.e., via two measured values each on the two lines H and L to the respective terminals 7a and 7b (or 8a and 8b) of the receiver coil 17 (or 18) to be measured, at the two instants R and F. This takes place by forming the average value of these four measured values U.sub.HR, U.sub.LR, U.sub.HF, and U.sub.LF:
U.sub.DC=*(U.sub.HR+U.sub.LR+U.sub.HF+U.sub.LF)

(11) FIG. 3 describes the meaning of this offset value. It is apparent that via the time-symmetrical sampling, the potential contributions which are induced by the sinusoidal excitation signal mutually cancel out one another, and the voltage division which is determined by the pull-up and pull-down resistors remains as an average value. However, in the event of a fault, the offset value is the potential caused by the short circuit, i.e., toward ground or U.sub.B, and the resistors R.sub.1, R.sub.2, R.sub.3, and R.sub.4 have little or no further influence.

(12) Thus, the identification of a short circuit 10 and the potential (toward ground or U.sub.B), toward which the short-circuit line is pulled (cf. FIG. 1), may be carried out in that the offset value U.sub.DC is compared (33 in FIG. 2) to limit values C.sub.G for a short to ground, and C.sub.B for a connection to the operating voltage U.sub.B. In fact, if
U.sub.DC<C.sub.G
a short to ground may be diagnosed, whereas with
U.sub.DC>C.sub.B
a connection to the operating voltage U.sub.B may be diagnosed.

(13) On the basis of the determination of which of these cases exists, the processor 2 is able to diagnose whether a short circuit 10 of a signal line exists, and the required measures may be carried out.

(14) A display and/or storage device 9 is used for displaying and/or storing the information ascertained by the processor 2. The positive detection of a short circuit 10, and the designation of the short-circuited line pair and the potential (ground or U.sub.B) toward which this line is pulled, are included in this display. In this case, the short-circuited line pair may, for example, be designated by its color or reference number.