Method for measuring a displacement

Abstract

A method of measuring a movement, the method comprising the steps of: acquiring and digitizing both a first measurement voltage across the terminals of a first secondary winding and also a second measurement voltage across the terminals of a second secondary winding of an inductive movement sensor; multiplying the first measurement voltage by itself in order to obtain a first component of a crossed vector, multiplying the second measurement voltage by itself in order to obtain a second component of the crossed vector, and multiplying together the first measurement voltage and the second measurement voltage in order to obtain a third component of the crossed vector; applying the crossed vector as input to a lowpass filter in order to obtain a filtered vector, and estimating the movement from the components of the filtered vector.

Claims

1. A method of measuring a movement, the method comprising: acquiring and digitizing both a first measurement voltage (V.sub.a) across terminals of a first secondary winding and also a second measurement voltage (V.sub.b) across terminals of a second secondary winding of an inductive movement sensor; multiplying the first measurement voltage by itself to obtain a first component (V.sub.1) of a crossed vector (V.sub.c), multiplying the second measurement voltage by itself to obtain a second component (V.sub.2) of the crossed vector (V.sub.c), and multiplying together the first measurement voltage and the second measurement voltage to obtain a third component (V.sub.3) of the crossed vector (V.sub.c); applying the crossed vector as input to a lowpass filter to obtain a filtered vector (V.sub.f); and estimating the movement from the components of the filtered vector (V.sub.f).

2. The measurement method according to claim 1, wherein the lowpass filter includes a first biquadratic filter and a second biquadratic filter.

3. The measurement method according to claim 1, wherein the inductive movement sensor is a resolver and wherein the movement is an angular movement, the measurement method further comprising: calculating V.sub.fa={square root over (V.sub.fa)}, where V.sub.fa is a first component of the filtered vector (V.sub.f); calculating V.sub.fb={square root over (V.sub.fb)}, where V.sub.fb is a second component of the filtered vector (V.sub.f); determining the sign of V.sub.fc, where V.sub.fc is a third component of the filtered vector (V.sub.f); and if V.sub.fc0, estimating the angular movement by using the formula =atan 2(Vf.sub.a, Vf.sub.b); or if V.sub.fc<0, estimating the angular movement by using the formula =atan 2(V.sub.fa, V.sub.fb).

4. The measurement method according to claim 1, wherein the inductive movement sensor is a linear variable differential transformer (LVDT) or a rotary variable differential transformer (RVDT), the movement being a linear movement or an angular movement, the measurement method further comprising: calculating V.sub.S=V.sub.fa+V.sub.fb, where V.sub.fa is a first component of the filtered vector (V.sub.f) and V.sub.fb is a second component of the filtered vector (V.sub.f); calculating V.sub.D=V.sub.faV.sub.fb; and if V.sub.D< and V.sub.D>, setting V.sub.R=0, and estimating the movement d by using the formula d=d.sub.0.Math.V.sub.R, where d.sub.0 is a maximum movement and is a dead zone threshold; or else calculating V.sub.R=V.sub.S/V.sub.D and V.sub.R.sup.2 and estimating the movement d from V.sub.R.sup.2.

5. The measurement method according to claim 4, wherein said estimating the movement d from V.sub.R.sup.2 comprises: comparing V.sub.R.sup.2 with 1; if V.sub.R.sup.21, estimating the movement d by using the formula d=d.sub.0.Math.V.sub.R; and if V.sub.R.sup.2>1, calculating V.sub.T={square root over (V.sub.R.sup.21)}; and if V.sub.fc0 and V.sub.D<0, or if V.sub.fc<0 and V.sub.D0, V.sub.fc being a third component of the filtered vector (V.sub.f), setting V.sub.R=V.sub.T, and estimating the movement d by using the formula d=d.sub.0.Math.V.sub.R; or else setting V.sub.R=V.sub.T, and estimating the movement d by using the formula d=d.sub.0.Math.V.sub.R.

6. An electrical processor circuit for connection to an inductive movement sensor, the electrical processor circuit comprising a processor component arranged to perform the measurement method according to claim 1.

7. A system comprising an electrical processor circuit according to claim 6 and an inductive movement sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Reference is made to the accompanying drawings, in which:

(2) FIG. 1 shows a system comprising a resolver, an electrical acquisition circuit, an electrical processor circuit, and an electrical generator circuit, with a measurement method in a first implementation of the invention being performed in the electrical processor circuit;

(3) FIG. 2 shows a processor component of the electrical processor circuit;

(4) FIG. 3 shows an initialization step of the measurement method of the first implementation of the invention;

(5) FIG. 4 shows steps of the measurement method of the first implementation of the invention;

(6) FIG. 5 shows a processor component of an electrical processor circuit in which use is made of a measurement method in a second implementation of the invention;

(7) FIG. 6 shows an initialization step of the measurement method of the second implementation of the invention; and

(8) FIG. 7 shows steps of the measurement method of the second implementation of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(9) The measurement method in a first implementation of the invention is for measuring the angular position of a rotor of an electric motor of an electromechanical actuator.

(10) With reference to FIG. 1, a resolver 1 is integrated in the electric motor. The resolver 1 comprises a stator and a rotor that is constrained to rotate with the rotor of the electric motor.

(11) An angular movement of the rotor of the resolver 1 is measured in order to obtain an estimate of the angular position of the rotor of the electric motor.

(12) The measurement method is performed in a processor component 2 of an electrical processor circuit 3. The electrical processor circuit 3 is mounted on an electric circuit card integrated in a first piece of electrical equipment. By way of example, the first piece of electrical equipment is a computer, a data concentrator, a control unit, etc.

(13) In this example, the processor component 2 is a field programmable gate array (FPGA), however it could be some other component, e.g. a microcontroller, a processor, or an application specific integrated circuit (ASIC), etc.

(14) The electrical processor circuit 3 is connected to an electrical acquisition circuit 4, which is itself connected to the resolver 1. An electrical generator circuit 5 is also connected to the electrical acquisition circuit 4. The electrical generator circuit 5 is mounted on an electric circuit card integrated in a second piece of electrical equipment that is situated at a certain distance from the first piece of electrical equipment.

(15) The electrical acquisition circuit 4 includes a digital-to-analog converter 7, a first analog-to-digital converter 8, a second analog-to-digital converter 9, a first amplifier 11, a second amplifier 12, and a third amplifier 13.

(16) An output of the electrical generator circuit 5 is connected to an input of the digital-to-analog converter 7. An output of the digital-to-analog converter 7 is connected to an input of the first amplifier 11. An output of the first amplifier 11 is connected to an output S.sub.1 of the electrical acquisition circuit 4, and an electrical ground is connected to an output S.sub.2 of the electrical acquisition circuit 4.

(17) The second amplifier 12 is associated with four resistors R.sub.1, R.sub.2, R.sub.3, and R.sub.4. The resistor R.sub.1 is connected between a non-inverting input of the second amplifier 12 and an input E.sub.1 of the electrical acquisition circuit 4. A first terminal of the resistor R.sub.2 is connected to a terminal of the resistor R.sub.1, and a second terminal of the resistor R.sub.2 is connected to electrical ground. The resistor R.sub.3 is connected between an input of the second amplifier 12 and an input E.sub.2 of the electrical acquisition circuit 4. A first terminal of the resistor R.sub.4 is connected to a terminal of the resistor R.sub.3, and a second terminal of the resistor R.sub.4 is connected to electrical ground.

(18) An output of the second amplifier 12 is connected to an input of the first analog-to-digital converter 8. An output of the first analog-to-digital converter 8 is connected to the processor component 2 of the electrical processor circuit 3.

(19) Likewise, the third amplifier 13 is associated with four resistors R.sub.1, R.sub.2, R.sub.3, and R.sub.4. The four resistors R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are connected between the third amplifier 13 and inputs E.sub.3 and E.sub.4, and they are arranged like the resistors R.sub.1, R.sub.2, R.sub.3, and R.sub.4.

(20) An output of the third amplifier 13 is connected to an input of the second analog-to-digital converter 9. An output of the second analog-to-digital converter 9 is connected to the processor component 2 of the electrical processor circuit 3.

(21) Each of the outputs S.sub.1 and S.sub.2 of the electrical acquisition circuit 4 is connected to a respective terminal of the primary winding 15 of the resolver 1. Terminals of a first secondary winding 16 of the resolver 1 are connected to the inputs E.sub.1 and E.sub.2. Terminals of a second secondary winding 17 of the resolver 1 are connected to the inputs E.sub.3 and E.sub.4.

(22) When the angular position of the rotor of the electric motor is to be measured, the electrical generator circuit 5 produces a digital excitation voltage V.sub.EXC, which is transformed into an analog excitation voltage V.sub.EXC by the digital-to-analog converter 7 of the electrical acquisition circuit 4. The excitation voltage V.sub.EXC is applied to the terminals of the primary winding 15 of the resolver 1.

(23) The excitation voltage V.sub.EXC is such that:
V.sub.EXC=U.sub.0.Math.sin(t+)
where U.sub.0, , and are respectively the amplitude, the angular frequency, and the phase of the excitation voltage V.sub.EXC.

(24) A first measurement voltage V.sub.a across the terminals of the first secondary winding 16 of the resolver 1 is then acquired and digitized by the second amplifier 12 and by the first analog-to-digital converter 8. Likewise, a second measurement voltage V.sub.b across the terminals of the second secondary winding 17 of the resolver 1 is then acquired and digitized by the third amplifier 13 and by the second analog-to-digital converter 9.

(25) With reference to FIG. 2, the first measurement voltage V.sub.a and the second measurement voltage V.sub.b are then acquired by the processor component 2 of the electrical processor circuit 3.

(26) The first measurement voltage V.sub.a can be estimated theoretically by the formula:
V.sub.a=V.sub.EXC.Math.sin()
where is the angular movement of the rotor of the resolver 1.

(27) The second measurement voltage V.sub.b can be estimated theoretically by the formula:
V.sub.b=V.sub.EXC.Math.cos().

(28) The processor component 2 also acquires AR coefficients C.sub.aij and AM coefficients C.sub.bij.

(29) The AR coefficients C.sub.aij comprise AR coefficients C.sub.a00, C.sub.a01 of a first biquadratic filter, and AR coefficients C.sub.a10, C.sub.a11 of a second biquadratic filter.

(30) The AM coefficients C.sub.bij comprise AM coefficients C.sub.b00, C.sub.b01, and C.sub.b02 of a first biquadratic filter, and AM coefficients C.sub.b10, C.sub.b11, and C.sub.b12 of a second biquadratic filter.

(31) The processor component 2 also acquires a dead zone threshold .

(32) Implementation of the measurement method makes use of a first state vector S.sub.00 of the first biquadratic filter, a second state vector S.sub.01 of the first biquadratic filter, a first state vector S.sub.10 of the second biquadratic filter, and a second state vector S.sub.11 of the second biquadratic filter.

(33) In the present application, it should be observed that vectors are written using bold notation.

(34) The vectors S.sub.00, S.sub.01, S.sub.10, and S.sub.11 are vectors, each comprising one column and four rows.

(35) With reference to FIG. 3, the measurement method begins with an initialization step E0, during which the vectors S.sub.00, S.sub.01, S.sub.10, and S.sub.11 are initialized to zero:

(36) $S_{00} = S_{01} = S_{10} = S_{11} = [\begin{matrix} 0 \\ 0 \\ 0 \\ 0 \end{matrix}] .$

(37) With reference to FIG. 4, the first measurement voltage V.sub.a is then multiplied by itself in order to obtain a first component V.sub.1 of a crossed vector V.sub.c. The second measurement voltage V.sub.b is multiplied by itself to obtain a second component V.sub.2 of the crossed vector V.sub.c. The first measurement voltage V.sub.a and the second measurement voltage V.sub.b are multiplied together in order to obtain a third component V.sub.3 of the crossed vector V.sub.c. A fourth component V.sub.4 of the crossed vector V.sub.c is set to zero (step E1).

(38) Thus:

(39) $V_{c} = [\begin{matrix} V_{1} \\ V_{2} \\ V_{3} \\ V_{4} \end{matrix}] = [\begin{matrix} V_{A} .Math. V_{A} \\ V_{B} .Math. V_{B} \\ V_{A} .Math. V_{B} \\ 0 \end{matrix}] .$

(40) The crossed vector V.sub.c is then applied as input to a lowpass filter.

(41) The lowpass filters serves to eliminate a 2 component from the crossed vector V.sub.c.

(42) The lowpass filter includes the first biquadratic filter and the second biquadratic filter.

(43) The crossed vector V.sub.c is thus applied initially as input to the first biquadratic filter (step E2).

(44) The following equations are obtained:
V.sub.i=C.sub.b00.Math.V.sub.c+S.sub.00
S.sub.00=C.sub.b01.Math.V.sub.cC.sub.a00.Math.V.sub.i+S.sub.01
S.sub.01=C.sub.b02.Math.V.sub.cC.sub.a01.Math.V.sub.i
V.sub.i is an intermediate vector output by the first biquadratic filter.

(45) The intermediate vector V.sub.i is then applied as input to the second biquadratic filter (step E3).

(46) The following equations are then obtained:
V.sub.f=C.sub.b10.Math.V.sub.i+S.sub.10
S.sub.10=C.sub.b11.Math.V.sub.iC.sub.a10.Math.V.sub.f+S.sub.11
S.sub.11=C.sub.b12.Math.V.sub.iC.sub.a11.Math.V.sub.f
V.sub.f is a filtered vector at the output from the second biquadratic filter.

(47) The angular movement of the rotor of the resolver 1 is then estimated from the components of the filtered vector V.sub.f.

(48) The measurement method thus includes the step of calculating V.sub.fa={square root over (V.sub.fa)}, where V.sub.fa is a first component of the filtered vector V.sub.f, and then of calculating V.sub.fb={square root over (V.sub.fb)}, where V.sub.fb is a second component of the filtered vector V.sub.f (step E4).

(49) The sign of V.sub.f, is then determined. V.sub.fc is a third component of the filtered vector V.sub.f (step E5).

(50) If V.sub.fc0, the angular movement is estimated by using the formula =atan 2(V.sub.fa, V.sub.fb): step E6.

(51) If V.sub.fc<0, the angular movement is estimated by using the formula =atan 2(V.sub.fa, V.sub.fb): step E7.

(52) It should be observed that the function atan 2(y, x) can be defined as follows:
atan 2(y,x)=arctan(y/x) if x>0;
atan 2(y,x)=/2arctan(x/y) if y>0;
atan 2(y,x)=/2arctan(x/y) if y<0;
atan 2(y,x)=arctan(y/x) if x<0;
atan 2(y,x) being undefined if x=0 and y=0.

(53) The measurement method then ends.

(54) The measurement method can thus be performed without the electrical processor circuit 3 acquiring the excitation voltage V.sub.EXC. Thus, there is no need to connect together the first piece of electrical equipment (in which the electrical processor circuit 3 is located) and the second piece electrical equipment (in which the electrical generator circuit 5 is located), by means of a cable dedicated to transmitting the excitation voltage V.sub.EXC.

(55) This serves to reduce the weight and the complexity of the system as described above, and to increase the reliability of said system.

(56) It should be observed that the accuracy of the resulting measurement is the same as when performing synchronous demodulation that makes use of the excitation voltage V.sub.EXC. Nevertheless, it is specified that the measurement taken without excitation is valid only for an angle lying in the range [/2; /2]. Outside this definition range, there is ambiguity of radians on the measurement of the angle .

(57) There follows a description of a measurement method in a second implementation of the invention. This time, the measurement method in the second implementation of the invention is for measuring the angular position of an actuator member of an electromechanical actuator.

(58) The measurement makes use of an RVDT. The angular movement of the rotor of the RVDT is measured in order to obtain an estimate of the angular position of the actuator member of the electromechanical actuator.

(59) The hardware of the system that takes the measurement is similar to that of the system as described above.

(60) With reference to FIG. 5, the first measurement voltage V.sub.a and the second measurement voltage V.sub.b are then acquired by the processor component 20 of the electrical processor circuit.

(61) The processor component 20 also acquires AR coefficients C.sub.aij and AM coefficients C.sub.bij.

(62) The AR coefficients C.sub.aij comprise AR coefficients C.sub.a00, C.sub.a01 of a first biquadratic filter, and AR coefficients C.sub.a10, C.sub.a11 of a second biquadratic filter.

(63) The AM coefficients C.sub.bij comprise AM coefficients C.sub.b00, C.sub.b01, C.sub.b02, and C.sub.b03 of a first biquadratic filter, and AM coefficients C.sub.b10, C.sub.b11, C.sub.b12, and C.sub.b13 of a second biquadratic filter.

(64) The processor component 20 also acquires a dead zone threshold .

(65) The predator component 20 also acquires a maximum angular movement .sub.0.

(66) With reference to FIG. 6, the measurement method begins with an initialization step E10, during which the vectors S.sub.00, S.sub.01, S.sub.10, and S.sub.11 are initialized to zero:

(67) $S_{00} = S_{01} = S_{10} = S_{11} = [\begin{matrix} 0 \\ 0 \\ 0 \\ 0 \end{matrix}] .$

(68) With reference to FIG. 7, the first measurement voltage V.sub.a is then multiplied by itself in order to obtain a first component V.sub.1 of a crossed vector V.sub.c. The second measurement voltage V.sub.b is multiplied by itself to obtain a second component V.sub.2 of the crossed vector V.sub.a. The first measurement voltage V.sub.a and the second measurement voltage V.sub.b are multiplied together in order to obtain a third component V.sub.3 of the crossed vector V.sub.c. A fourth component V.sub.4 of the crossed vector V.sub.c is set to zero (step E11).

(69) Thus:

(70) $V_{c} = [\begin{matrix} V_{1} \\ V_{2} \\ V_{3} \\ V_{4} \end{matrix}] = [\begin{matrix} V_{A} .Math. V_{A} \\ V_{B} .Math. V_{B} \\ V_{A} .Math. V_{B} \\ 0 \end{matrix}] .$

(71) The crossed vector V.sub.c is then applied as input to a lowpass filter including the first biquadratic filter and the second biquadratic filter.

(72) The crossed vector V.sub.c is initially applied as input to the first biquadratic filter (step E12).

(73) The following equations are thus obtained:
V.sub.i=Cb.sub.00.Math.V.sub.c+S.sub.00
S.sub.00=C.sub.b01.Math.V.sub.cC.sub.a00.Math.V.sub.i+S.sub.01
S.sub.01=C.sub.b02.Math.V.sub.cC.sub.a01.Math.V.sub.i
V.sub.i is an intermediate vector at the output from the first biquadratic filter.

(74) The intermediate vector V.sub.i is then applied as input to the second biquadratic filter (step E13).

(75) The following equations are then obtained:
V.sub.f=C.sub.b10.Math.V.sub.i+S.sub.10
S.sub.10=C.sub.b11.Math.V.sub.iC.sub.a10.Math.V.sub.f+S.sub.11
S.sub.11=C.sub.b12.Math.V.sub.iC.sub.a11.Math.V.sub.f
V.sub.f is a filtered vector at the output from the second biquadratic filter.

(76) The angular movement of the rotor of the RVDT is then estimated from the components of the filtered vector.

(77) The measurement method thus includes the step of calculating V.sub.S=V.sub.fa+V.sub.fb and V.sub.D=V.sub.faV.sub.fb, where V.sub.fa is a first component of the filtered vector V.sub.f and V.sub.fb is a second component of the filtered vector V.sub.f (step E14).

(78) If V.sub.D< and V.sub.D> (step E15), then the measurement method includes the step of setting:
V.sub.R=0(step E16).

(79) The angular movement is then estimated by using the formula:
=.sub.0.Math.V.sub.R(step E17).

(80) Otherwise, the measurement method includes the step of calculating:
V.sub.R=V.sub.S/V.sub.D and V.sub.R.sup.2=V.sub.R.Math.V.sub.R(step E18).

(81) Thereafter, V.sub.R.sup.2 is compared with 1 (step E19).

(82) If V.sub.R.sup.21, the angular movement is estimated by using the formula:
=.sub.0.Math.V.sub.R(step E17).

(83) If V.sub.R.sup.2>1, the measurement method includes the step of calculating:
V.sub.T={square root over (V.sub.R.sup.21)}(step E20).

(84) Under such circumstances, if: V.sub.fc0 and V.sub.D<0, or if V.sub.fc<0 and V.sub.D0 (step E21), then the measurement method includes a step of setting:
V.sub.R=V.sub.T(step E22).
V.sub.fc is a third component of the filtered vector V.sub.f.

(85) Otherwise, the measurement method includes a step of setting:
V.sub.R=V.sub.T(step E23).

(86) The angular movement is then estimated by using the formula:
=.sub.0.Math.V.sub.R(step E17).

(87) The measurement method then ends.

(88) It should be observed at this point that the measurement method in the second implementation of the invention can also be used with an LVDT, serving to measure a linear movement X.

(89) In the above, the angular movement should be replaced by the linear movement X, and the maximum angular movement .sub.0 should be replaced by the maximum linear movement X.sub.0.

(90) The measurement method is thus generalized by using a movement d and a maximum movement d.sub.0. d is an angular movement or a linear movement, and d.sub.0 is a maxim-m angular movement or a maximum linear movement.

(91) Naturally, the invention is not limited to the embodiments described, but covers any variant coming within the ambit of the invention as defined by the claims.

(92) It is stated above that the first piece of electrical equipment and the second piece of electrical equipment are not connected together by a cable for transmitting the excitation voltage V.sub.EXC. Specifically, the excitation voltage V.sub.EXC is not required by the measurement method of the invention.

(93) Nevertheless, it should be observed that it is entirely possible for the first piece of electrical equipment and the second piece of electrical equipment to be connected together by such a cable. By way of example, it is then possible, in normal operation, to make provision for taking measurements by performing conventional synchronous demodulation that makes use of the excitation voltage. The measurement method of the invention is then used when the excitation voltage is no longer available, e.g. because the cable has broken.

Method for measuring a displacement

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G06F17/16

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G01D5/2073

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G06F17/00

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G06F2101/08

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G06F2101/02

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G01R23/167

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G06F2101/04

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G01D5/2291

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Abstract

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Description