WO2022112856A1

WO2022112856A1 - Absolute position transducer and method for measuring the position

Info

Publication number: WO2022112856A1
Application number: PCT/IB2021/055701
Authority: WO
Inventors: Alessandro SOLDATI
Original assignee: EDRIVELAB S.r.l.
Priority date: 2020-11-26
Filing date: 2021-06-25
Publication date: 2022-06-02

Abstract

An absolute position transducer (1) comprising: two tracks (A, S) having a number of pitches which differs by only one unit; - two sensors (MA, MS) configured to sense a shift of the support (2) as a function of the positions assumed by the tracks (A, S) and to output a first signal (SigA) and a second signal (Sigs) having different periods, respectively; - a signal processing module (3) which, in response to the reception, as input, of the first signal (SigA) and of the second signal (Sigs) is configured to: • detect rising edges (AR) and falling edges (AF) of the first signal (SigA) and rising edges (SR) and falling edges (SF) of the second signal (Sigs); • calculate a plurality of time intervals between the edges (AR, AF, SR, SF); • calculate a travel time of the shift of the support (2) as a function of the time intervals between the edges (AR, AF, SR, SF); • calculate a position value (ϑ) of the support (2) as a function of the travel time of the shift and of the time intervals between the edges (AR, AF, SR, SF).

Description

DESCRIPTION

ABSOLUTE POSITION TRANSDUCER AND METHOD FOR MEASURING THE POSITION

Technical field

The present invention relates to an absolute position transducer and a method for measuring the position.

Background art Analogue position transducers require analogue to digital converters to read the measurement and are affected by noise.

Even the digital position transducers (generally referred to as “encoders”) currently known have some limitations.

For example, for absolute digital transducers, a high resolution is obtained in connection with an equally high level of construction complexity.

Among these, Vernier encoders are based on the nonius, i.e., an instrument provided with a graduated scale which is used to evaluate the fractions of the unit of measurement. Vernier encoders require different tracks for the reading and do not provide velocity information. Furthermore, the absolute position data is available after a minimum shaft rotation.

Incremental or relative digital sensors do not provide instantaneous information, except after the rotation of the measured shaft by at least one revolution, in the worst case. Furthermore, such sensors are sensitive to any pulse loss and require an additional track for correction, always requiring at least one shaft revolution (worst case).

Disclosure of the invention

In this context, the technical task underpinning the present invention is to provide an absolute position transducer and a method for measuring the position which obviate the drawbacks of the prior art as cited above.

In particular, the object of the present invention is to propose an absolute position transducer and a method for measuring the position, which provide more accurate measurements with respect to the currently known instruments based on the nonius principle.

In particular, an object of the present invention is to propose an absolute position transducer and a method for measuring the position which make the absolute angular position measurement available even after small rotations of a shaft.

The stated technical task and specified aims are substantially achieved by an absolute position transducer, comprising:

- a support having at least a first track and a second track, the first track comprising a first series of equally spaced pitches and the second track comprising a second series of equally spaced pitches, the number of pitches of the first series being N and differing from the number of pitches of the second series by only one unit;

- at least two sensors configured to sense a shift of the support as a function of the positions assumed by the first track and the second track and to output a first signal and a second signal having different periods, respectively;

- a signal processing module which, in response to the reception, as input, of the first signal and of the second signal is configured to:

• detect rising edges and falling edges of the first signal and rising edges and falling edges of the second signal;

• calculate a plurality of time intervals between the edges;

• calculate a travel time of the shift of the support as a function of the time intervals between the edges;

• calculate a position value of the support as a function of the travel time of the shift and of the time intervals between the edges.

In accordance with an aspect of the invention, the first signal and the second signal are square-wave signals.

In accordance with an aspect of the invention, the signal processing module is configured to calculate time intervals between homologous edges, i.e. of the same type, of the first signal and between homologous edges, i.e. of the same type, of the second signal.

In accordance with an embodiment, the signal processing module is configured to:

- calculate a first indicator representative of the time elapsing between two consecutive falling edges of the first signal;

- calculate a second indicator representative of the time elapsing between two consecutive rising edges of the first signal;

- calculate a third indicator representative of the time elapsing between two consecutive falling edges of the second signal;

- calculate a fourth indicator representative of the time elapsing between two consecutive rising edges of the second signal;

- apply a first blending function to the first indicator, the second indicator, the third indicator and the fourth indicator so as to output the calculation of the shift travel time.

Preferably, the signal processing module comprises a statistical calculation module configured to apply a first blending function selected from among the following: instantaneous average, moving window average, exponential average with a predefined time constant.

In accordance with an embodiment, the support is a rotating disc and the number of pitches in the second series is N+1. In this case, the signal processing module preferably comprises:

- a first module for calculating the first indicator, the first module comprising a first digital counter configured to calculate the time elapsing between two consecutive falling edges of the first signal, to apply a gain equal to N, to invert and apply a gain equal to 2TT SO that the first indicator is an angular velocity; a second module for calculating the second indicator, the second module comprising a second digital counter configured to calculate the time elapsing between two consecutive rising edges of the first signal, to apply a gain equal to N, to invert and apply a gain equal to 2p so that the second indicator is an angular velocity; a third module for calculating the third indicator, the third module comprising a third digital counter configured to calculate the time elapsing between two consecutive falling edges of the second signal, to apply a gain equal to (N+1 ), to invert and apply a gain equal to 2TT so that the third indicator is an angular velocity;

- a fourth module for calculating the fourth indicator, the fourth module comprising a fourth digital counter configured to calculate the time elapsing between two consecutive rising edges of the second signal, to apply a gain equal to (N+1), to invert and apply a gain equal to 2TT SO that the fourth indicator is an angular velocity.

In accordance with another embodiment, the support is a rotating disc and the number of pitches in the second series is N-1. In this case, the signal processing module preferably comprises:

- a first module for calculating the first indicator, the first module comprising a first digital counter configured to calculate the time elapsing between two consecutive falling edges of the first signal, to apply a gain equal to N, to invert and apply a gain equal to 2TT SO that the first indicator is an angular velocity; a second module for calculating the second indicator, the second module comprising a second digital counter configured to calculate the time elapsing between two consecutive rising edges of the first signal, to apply a gain equal to N, to invert and apply a gain equal to 2p so that the second indicator is an angular velocity;

- a third module for calculating the third indicator, the third module comprising a third digital counter configured to calculate the time elapsing between two consecutive falling edges of the second signal, to apply a gain equal to (N-1), to invert and apply a gain equal to 2TT SO that the third indicator is an angular velocity;

- a fourth module for calculating the fourth indicator, the fourth module comprising a fourth digital counter configured to calculate the time elapsing between two consecutive rising edges of the second signal, to apply a gain equal to (N-1), to invert and apply a gain equal to 2 p so that the fourth indicator is an angular velocity.

In accordance with an aspect of the invention, the signal processing module is configured to calculate time intervals between non-homologous edges, i.e. of a different type, of the first signal and between non- homologous edges, i.e. of a different type, of the second signal.

In accordance with an aspect of the invention, the signal processing module is configured to calculate at least one indicator representative of the time elapsing between an edge of the first signal and an edge of the second signal.

Preferably, the signal processing module is configured to calculate a plurality of indicators representative of the time elapsing between pairs of edges belonging to different signals, i.e. an edge of the first signal and an edge of the second signal, in which the indicators are position values.

In accordance with an embodiment, the signal processing module is configured to apply a second blending function to the position values so as to output an estimate of the position.

In accordance with an embodiment, the indicators are calculated between pairs of homologous edges belonging to different signals, i.e. a rising edge of the first signal and a rising edge of the second signal or a falling edge of the first signal and a falling edge of the second signal.

In accordance with an embodiment, the indicators are also calculated between pairs of non-homologous edges belonging to different signals, i.e. a rising edge of the first signal and a falling edge of the second signal or a falling edge of the first signal and a rising edge of the second signal.

In accordance with an aspect of the invention, the support has further tracks, each of which has one pitch more or one pitch less than the immediately adjacent track.

The stated technical task and specified aims are substantially achieved by a method for measuring the position of a support having at least a first track and a second track, the first track comprising a first series of equally spaced pitches and the second track comprising a second series of equally spaced pitches, the number of pitches of the first series being N and differing from the number of pitches of the second series by only one unit, the method comprising at least the following steps:

- detecting a shift of the support as a function of the positions assumed by the first track and the second track and thus providing a first signal associated with the first track and a second signal associated with the second track, the first signal and the second signal having different periods;

- detecting rising edges and falling edges of the first signal and rising edges and falling edges of the second signal;

- calculating a plurality of time intervals between the detected edges;

- calculating the travel time of the shift as a function of the time intervals;

- calculating the position of the support as a function of the travel time of the shift and of the time intervals.

Brief description of drawings

Further features and advantages of the present invention will become more apparent from the approximate and thus non-limiting description of a preferred, but not exclusive, embodiment of an absolute position transducer and method for measuring the position, as illustrated in the accompanying drawings, in which:

- figure 1 schematically shows an absolute position transducer, according to the present invention;

- figure 2 shows the waveforms of a first signal and a second signal detected by the sensors of the transducer of figure 1 , with some relevant elements;

- figure 3 shows the block diagram of a part of the signal processing module of figure 1 , in particular for the angular velocity calculation, in accordance with an embodiment; - figure 4 shows the block diagram of a part of the signal processing module of figure 1 , in particular for the angular velocity calculation, in accordance with another embodiment;

- figure 5 shows the block diagram of a part of the signal processing module of figure 1 , in particular for the angular position calculation, in accordance with an embodiment;

- figure 6 shows a block diagram of one of the calculation modules of figure 5.

Detailed description of preferred embodiments of the invention

With reference to the figures, the number 1 indicates an absolute position transducer comprising a support 2 having at least two tracks, herein referred to as:

- first track A

- second track S.

The support 2 can be of a linear type, or a rotating disc, as shown in the example of figure 1 .

The first track A comprises a first series of equally spaced pitches PA. In particular, N indicates the number of pitches pAOf the first track A.

The second track S comprises a second series of equally spaced pitches ps.

Originally, the second track S has a number of pitches ps which differs from the number of pitches of the first track PA by only one unit. Therefore, the number of pitches ps of the second track S is equal to N+1 or N-1 .

As can be seen from figure 1 , relative to the rotating disc 2, the two tracks A, S follow two different concentric circumferential lines of the rotating disc 2.

The transducer 1 comprises at least two sensors MA, MS configured to sense a shift of the support 2 (for example an angular shift of the rotating disc 2) as a function of the positions assumed by the first track A and the second track S and to output a first signal SigA, associated with the first track A, and a second signal Sigs, associated with the second track S. In particular, the first signal SigA is a square wave having a first duty-cycle dA, and the second signal Sigs is a square wave having a second duty- cycle ds.

In figure 2, the duty-cycles of both signals are 50%. However, the calculation logic explained below is also valid for different duty-cycle values.

In fact, the duty-cycles of the signals SigA and Sigs depend on the amplitude of the "windows” of the tracks in relation to the period thereof and the particular conditioning circuit linked to the technology of the sensors MA, MS.

The two sensors MA, MS can be based on different physical principles, for example they can be optical sensors or magnetic sensors or sliding contact sensors.

Since the number of pitches PA of the first track A is different from the number of pitches ps of the second track S, the first signal SigA and the second signal Sigs have different periods, as seen in figure 2.

In the event of measurement associated with the rotating disc 2, a period T associated with the pair of the two signals SigA, Sigs is defined, which is represented by the time interval elapsing between two consecutive moments whose first signal SigA and second signal Sigs are in phase, i.e. between two consecutive moments in which homologous events occur for the first signal SigA and for the second signal SigA.

In this context, homologous events are events of the same type, such as rising events or falling events of the signals.

For example, the period T can be calculated as the time interval between a first instant ti in which both the first signal SigA and the second signal Sigs have a rising edge and a second instant t2 in which both the first signal SigA and the second signal Sigs have the next rising edge.

In the event of a linear position transducer, the shift is a linear excursion, therefore the concept of period T (which is linked to rotation) is not present but a travel time of the linear excursion is estimated. The transducer 1 comprises a signal processing module 3 which, in response to the reception, as input, of the first signal SigA and of the second signal Sigs is configured to:

• detect rising edges AR and falling edges AF of the first signal SigA and rising edges SR and falling edges SF of the second signal Sigs;

• calculate a plurality of time intervals between the edges AR, AF, SR, SF;

• calculate the travel time of the shift as a function of the time intervals between the edges AR, AF, SR, SF;

• calculate the position 1? of the support 2 as a function of the travel time of the shift and of the time intervals between the edges AR, AF, SR, SF.

Taking up the specific case of the rotating disc 2, the rotation period T is calculated as a function of the time intervals between the edges AR, AF, SR, SF and the angular position

of the rotating disc 2 is calculated as a function of the period T and the time intervals between the edges AR, AF, SR, SF.

At constant velocity, the angular position i? and the time t are in fact linked by the relation: i? = cot, where w is the angular velocity.

This is in turn linked to the period T by the well-known equation:

T = 2TT/CJ.

In accordance with an aspect of the invention, the signal processing module 3 is configured to calculate time intervals between homologous edges (falling and/or rising) of the first signal SigA and between homologous edges (falling and/or rising) of the second signal Sigs.

In accordance with an embodiment of the invention, the signal processing module 3 is configured to calculate four indicators, namely:

- a first indicator tAF; COAF representative of the time elapsing between two consecutive falling edges AF (which are two consecutive homologous events) of the first signal SigA;

- a second indicator tAR; WAR representative of the time elapsing between two consecutive rising edges AR (which are two consecutive homologous events) of the first signal SigA; - a third indicator tsF; WSF representative of the time elapsing between two consecutive falling edges SF (which are two consecutive homologous events) of the second signal Sigs;

- a fourth indicator tsR; w SR representative of the time elapsing between two consecutive rising edges SR (which are two consecutive homologous events) of the second signal Sigs.

The four indicators can be time or velocity values (for example, angular). The signal processing module 3 is further configured to apply a first blending function fei to the four indicators thus calculated so as to output the measurement of the period T or the duality thereof (angular velocity W).

For example, figure 2 refers to an embodiment in which the second track S has a number of pitches ps equal to N+1 .

In accordance with this embodiment, and considering for example the case of a rotating disc 2, the signal processing module 3 comprises: - a first module 10 for calculating the first indicator WAF, which in turn comprises a first digital counter C1 configured to calculate the time elapsing between two consecutive falling edges AF of the first signal SigA, to apply a gain equal to N, to invert and apply a gain equal to 2p so that the first indicator WAF is an angular velocity; - a second module 11 for calculating the second indicator WAR, which in turn comprises a second digital counter C2 configured to calculate the time elapsing between two consecutive rising edges AR of the first signal SigA, and to apply a gain equal to N, to invert and apply a gain of 27G so that the second indicator WAR is an angular velocity; - a third module 12 for calculating the third indicator CJSF, which in turn comprises a third digital counter C3 configured to calculate the time elapsing between two consecutive falling edges SF of the second signal Sigs, to apply a gain equal to (N+1), to invert and apply a gain equal to 2TT SO that the third indicator GJSF is an angular velocity;

- a fourth module 13 for calculating the fourth indicator CJSR, which in turn comprises a fourth digital counter C4 configured to calculate the time elapsing between two consecutive rising edges SR of the second signal Sigs, to apply a gain equal to (N+1), to invert and apply a gain equal to 2p so that the fourth indicator OSR is an angular velocity.

In particular, the digital counters C1 , C2, C3, C4 are digital counters of known type, preferably with memory.

In particular, the first calculation module 10 outputs the first indicator, corresponding to a first angular velocity CJAF calculated as follows: COAF 2p / (N(tAF’-tAF)), where tAF and tAF are the instants at which two consecutive falling edges occur, indicated as AF and AF’, of the first signal SigA.

The second calculation module 11 outputs the second indicator, corresponding to a second angular velocity COAR calculated as follows: CJAR = 27G / (N(tAR’-tAR)), where tAR and tAF are the instants when two consecutive rising edges occur, referred to as AR and AR', of the first signal SigA.

The third calculation module 12 outputs the third indicator, corresponding to a third angular velocity OJSF calculated as follows: CJSF = 2rr / ((N+1 )(tSF’-tSF)), where tsF and tsF are the instants when two consecutive falling edges occur, indicated as SF and SF’, of the second signal Sigs

The fourth calculation module 13 outputs the fourth indicator, corresponding to a fourth angular velocity w SR calculated as follows: w SR = 2rr / ((N+1 )(tsR’-tsR)), where tsR and tsR’ are the instants in which two consecutive rising edges occur, indicated as SR and SR’, of the second signal Sigs.

In another embodiment, in which the second track S has a number of pitches ps equal to N-1 , in the third module 12 and in the fourth module 13 the gain applied after the respective digital counters C3, C4 is equal to (N- 1)·

Once the indicators have been calculated, the first blending function fei is applied so as to output the measurement of the period T or the angular velocity w.

To this end, the signal processing module 3 comprises a first statistical calculation module 20 configured to apply a first blending function fei selected from among the following: instantaneous average of the four velocities, moving window average of the last M samples of each of the four velocities, exponential average with a predefined time constant, velocity observers based on a dynamic model of the rotation system (e.g., based on Kalman filter).

In practice, once the four angular velocities WAF, WAR, WSF, WSR are calculated, the angular velocity w equal to: w = fBi(WAF, WAR, WSF, WSR) is calculated.

The blending functions fBi mentioned above are of a known type and will not be further described.

In an embodiment, the signal processing module 3 is configured to also calculate further time intervals between non-homologous edges of the first signal SigA and between non-homologous edges of the second signal Sigs.

By way of example, the following additional angular velocity values can be calculated from the first signal SigA:

- a fifth angular velocity WARF calculated as follows:

WARF = 2TT dA / (N(tAF-tAR)), in particular by means of a fifth calculation module 14;

- a sixth angular velocity OMFR calculated as follows:

OMFR = 2TT (1 -dA) / (N(tAF-tAR)), in particular by means of a sixth calculation module 15, where tAR and tAF are the instants when a rising and falling edge of the first signal SigA occurs.

With regard to the second signal Sigs, the following further angular velocity values can also be calculated:

- a seventh angular velocity WSRF calculated as follows:

OJSRF = 2TT ds / (N(tSF-tSR)), in particular by means of a seventh calculation module 16;

- an eighth angular velocity CJSFR calculated as follows:

CJSFR = 27G (1 -ds) / (N(tSF-tSR)), in particular by means of an eighth calculation module 17, where tsR and tsF are the instants in which a rising edge and a falling edge of the second signal Sigs occur.

This embodiment variant is illustrated in figure 4.

In accordance with an aspect of the invention, the signal processing module 3 is configured to calculate time intervals between different signal edges.

In particular, the signal processing module 3 is configured to calculate at least one indicator representative of the time elapsing between an edge of the first signal SigA and an edge of the second signal Sigs.

In particular, the signal processing module 3 is configured to calculate a plurality of indicators representative of the time elapsing between pairs of edges belonging to different signals, i.e. an edge of the first signal SigA and an edge of the second signal Sige.

In accordance with an embodiment, the indicators are calculated from pairs of homologous edges but of different signals.

In particular, in addition to the first four calculation modules indicated with 10, 11 , 12 and 13 (and, optionally, the fifth to eighth modules), the signal processing module 3 also comprises the following:

- a ninth module 18 for calculating a first angular position i9i;

- a tenth module 19 for calculating a second angular position

- an eleventh module 21 for calculating a third angular position i?3; a twelfth module 22 for calculating a fourth angular position i5 .

In particular, in the ninth calculation module 18 the time interval tARSR = tAR- tsR is first calculated, where tAR and tsR are the instants in which a rising edge AR of the first signal SigA and a rising edge SR of the second signal Sigs occur, respectively.

Assuming that the angular velocity is constant, by virtue of the fact that the two tracks A, S differ by only one pitch, the relationship between the ratio tARSR/T and the angular position i9i is invertible.

In the event of non-constant velocity (as occurs in reality), the inverse of the estimate of velocity output by the first blending function f BI is considered.

Then, in the ninth module 18 the ratio between t ARSR and this inverse value is calculated, which is in turn then inverted by a function f^-1.

The same is true for the other modules from the tenth to the twelfth module, which always start from the detection of pairs of homologous edges of different signals, namely: falling edge AF of the first signal SigA and falling edge SF of the second signal Sigs,

- rising edge SR of the second signal Sigs and rising edge AF of the first signal SigA,

- falling edge SF of the second signal Sigs. and falling edge AF of the first signal SigA, to calculate the time intervals between such pairs of edges, for which there is: tAFSF = tAF-tsF, tsRAR = tsR-tAR, tsFAF = tsF-tAF, which are then divided by the estimation of the period and then inverted by means of f ¹. Figure 6 shows in detail the composition of only the ninth module 18 for the purpose of simplicity.

However, the tenth to twelfth modules have a composition which is completely similar to that of the ninth module 18.

In particular, each of them comprises a digital counter C similar to those used in the angular velocity calculation modules, which however receives, as input, both the first signal SigA and the second signal Sigs.

Downstream of the digital counter C there is a division module “x/y” which is configured to calculate the ratio between the time interval tARSR and the estimate of the period T, followed by an inversion block indicated with T¹. Each module has the corresponding inversion block thereof: the functions used have the same shape but a circular rotation on the axis of the abscissae.

The signal processing module 3 is further configured to apply to the angular position values i?i, i?2, i¾, i?4 thus calculated a second blending function fB2 so as to output the angular position ) of the rotating disc 2.

To this end, the signal processing module 3 comprises a second statistical calculation module 23 configured to apply a second blending function fB2 selected from among those listed above.

In practice, once the four angular positions i9i, i?2, i?3, i?4 have been calculated, the angular position i? equal to: i? = fB2(i?i, 1?2, T3-3, i?4) is calculated.

In accordance with an embodiment variant, the signal processing module 3 is configured to also calculate further indicators starting from time intervals between the edges of the first signal SigA and the edges of the second signal Sigs, which are not homologous to each other.

Each of such intervals is then divided by the estimate of period T and then inverted by means of f ¹, as explained for the “homologous” edges of different signals. The transducer 1 further allows to provide the rotation direction of the rotating disc 2, indicated with p, which is identified by observing subsequent positions. In particular, if the rotation occurs with increasing angles, “positive direction" is assumed, while if the rotation occurs with decreasing angles, “negative direction" is assumed.

The mapping of "positive direction” and “negative direction” to “clockwise rotation” or “counter-clockwise rotation” or vice versa is purely arbitrary and depends on the application.

So far, a transducer 1 having only two tracks A, S has been described, which are sufficient to ensure improved performance compared to the known instruments.

In accordance with an embodiment, the support 2 of the transducer 1 can have more than two tracks. The number of pitches always increases (or decreases) by one unit passing from one track to the immediately adjacent one.

For example, in the case of a rotating disc, the number of pitches always increases (or decreases) by one unit, passing from one track to the track which extends along the ideal circumferential line immediately above or below.

From the description, the features of an absolute position transducer and a method for measuring the position according to the present invention appear clear, as do the advantages thereof.

In particular, it is sufficient to use two tracks differing by a single pitch, to obtain much more accurate measurements of velocity and position compared to the known solutions.

In fact, the sensors are able to detect two signals which, not being in quadrature as occurs in the instruments of the prior art, allow to calculate various velocity values. Such values are available at different times and are generally unrelated (although in some cases they may coincide). Merging these instantaneous velocities using more or less averagely complex functions allows to obtain a more accurate velocity measurement than the known solutions.

Similar considerations apply to the calculation of the position, also based on a plurality of instantaneous measurements which are then blended together. Increasing the number of measurements for both velocity and position can further increase the measurement accuracy.

The proposed transducer allows to provide the absolute angular position information already after slight rotations of the shaft, which can in fact be assimilated to vibrations, therefore safely feasible. Finally, the sensors are less sensitive to pulse loss and do not require an additional track for correction, as is the case in the known instruments.

Claims

1. An absolute position transducer (1) comprising:

- a support (2) having at least a first track (A) and a second track (S), said first track (A) comprising a first series of equally spaced pitches (PA), said second track (S) comprising a second series of equally spaced pitches (ps), the number of pitches (PA) of the first series being N and differing from the number of pitches (ps) of the second series by only one unit;

- at least two sensors (MA, MS) configured to sense a shift of the support (2) as a function of the positions assumed by said first track (A) and said second track (S) and to output a first signal (SigA) and a second signal (Sigs), respectively, said first signal (SigA) and said second signal (Sigs) having different periods;

- a signal processing module (3) which, in response to the reception, as input, of the first signal (SigA) and of the second signal (Sigs) is configured to:

• detect rising edges (AR) and falling edges (AF) of said first signal

(SigA) and rising edges (SR) and falling edges (SF) of said second signal (Sigs);

• calculate a plurality of time intervals between said edges (AR, AF, SR, SF);

• calculate a travel time of the shift of the support (2) as a function of the time intervals between said edges (AR, AF, SR, SF);

• calculate a position value (i9 of the support (2) as a function of the travel time of the shift and of the time intervals between said edges (AR, AF, SR, SF).

2. The absolute position transducer (1 ), wherein said first signal (SigA) and said second signal (Sigs) are square-wave signals.

3. The absolute position transducer (1) according to claim 1 or 2, wherein said signal processing module (3) is configured to calculate time intervals between homologous edges, i.e. of the same type, of the first signal SigA and between homologous edges, i.e. of the same type, of the second signal Sigs.

4. The absolute position transducer (1) according to claim 3, wherein said signal processing module (3) is configured to:

- calculate a first indicator (tAF ; CJAF) representative of the time elapsing between two consecutive falling edges (AF) of the first signal (SigA);

- calculate a second indicator (tAR; WAR) representative of the time elapsing between two consecutive rising edges (AR) of the first signal (SigA);

- calculate a third indicator (tsF; CJSF) representative of the time elapsing between two consecutive falling edges (SF) of the second signal (Sigs);

- calculate a fourth indicator (tsR; CJSR) representative of the time elapsing between two consecutive rising edges (SR) of the second signal (Sigs); - apply a first blending function (fBi) to said first indicator (tAF; CJAF), said second indicator (tAR; w AR), said third indicator (tsF; CJSF) and said fourth indicator (tsR; WSR) SO as to output the calculation of the travel time of the shift.

5. The absolute position transducer (1) according to claim 4, wherein said signal processing module (3) comprises a statistical calculation module

(20) configured to apply a first blending function (fBi) selected from among the following: instantaneous average, moving window average and exponential average with a predefined time constant.

6. The absolute position transducer (1) according to claim 4 or 5, wherein the support (2) is a rotating disc and the number of pitches (ps) of the second series is N+1 , said signal processing module (3) comprising:

- a first module (10) for calculating the first indicator (O F), said first module (10) comprising a first digital counter (C1) configured to calculate the time elapsing between two consecutive falling edges (AF) of the first signal (SigA), to apply a gain equal to N, to invert and apply a gain equal to 2TT SO that said first indicator (GOAF) is an angular velocity;

- a second module (11 ) for calculating the second indicator (GJAR), said second module (11 ) comprising a second digital counter (C2) configured to calculate the time elapsing between two consecutive rising edges (AR) of the first signal (SigA), to apply a gain equal to N, to invert and apply a gain equal to 2p so that said second indicator (GJAR) is an angular velocity; - a third module (12) for calculating the third indicator (CJSF), said third module (12) comprising a third digital counter (C3) configured to calculate the time elapsing between two consecutive falling edges (SF) of the second signal (Sigs), to apply a gain equal to (N+1), to invert and apply a gain equal to 2TT SO that said third indicator (CUSF) is an angular velocity;

- a fourth module (13) for calculating the fourth indicator (COSR)), said fourth module (13) comprising a fourth digital counter (C4) configured to calculate the time elapsing between two consecutive rising edges (SR) of the second signal (Sigs), to apply a gain equal to (N+1), to invert and apply a gain equal to 2TT SO that said fourth indicator (WSR) is an angular velocity.

7. The absolute position transducer (1) according to claim 4 or 5, wherein the support (2) is a rotating disc and the number of pitches (ps) of the second series is N-1 , said signal processing module (3) comprising: - a first module (10) for calculating the first indicator (w AF), said first module (10) comprising a first digital counter (C1) configured to calculate the time elapsing between two consecutive falling edges (AF) of the first signal (SigA), to apply a gain equal to N, to invert and apply a gain equal to 2TT SO that said first indicator (GOAF) is an angular velocity;

- a second module (11 ) for calculating the second indicator (GJAR), said second module (11) comprising a second digital counter (C2) configured to calculate the time elapsing between two consecutive rising edges (AR) of the first signal (SigA), to apply a gain equal to N, to invert and apply a gain equal to 2 p so that said second indicator (WAR) is an angular velocity;

- a third module (12) for calculating the third indicator (GJSF), said third module (12) comprising a third digital counter (C3) configured to calculate the time elapsing between two consecutive falling edges (SF) of the second signal (Sigs), to apply a gain equal to (N-1), to invert and apply a gain equal to 2TT SO that said third indicator (w SF) is an angular velocity;

- a fourth module (13) for calculating the fourth indicator (CJSR), said fourth module (13) comprising a fourth digital counter (C4) configured to calculate the time elapsing between two consecutive rising edges (SR) of the second signal (Sigs), to apply a gain equal to (N-1), to invert and apply a gain equal to 2TT SO that said fourth indicator (C SR) is an angular velocity.

8. The absolute position transducer (1 ) according to any one of the preceding claims, wherein said signal processing module (3) is configured to calculate time intervals between non-homologous edges, i.e. of a different type, of the first signal (SigA) and between non-homologous edges, i.e. of a different type, of the second signal (Sigs).

9. The absolute position transducer (1) according to claim 8, wherein said signal processing module (3) is configured to calculate at least one indicator representative of the time elapsing between an edge of the first signal (SigA) and an edge of the second signal (Sigs).

10. The absolute position transducer (1) according to claim 9, wherein said signal processing module (3) is configured to calculate a plurality of indicators representative of the time elapsing between pairs of edges belonging to different signals, i.e. an edge of the first signal (SigA) and an edge of the second signal (Sigs), said indicators being position values (i?i,

11. The absolute position transducer (1) according to claim 10, wherein said signal processing module (3) is configured to apply a second blending function (fB2) to said position values (l?i, 1 ,

T$A) SO as to output an estimate of said position (i3).

12. The absolute position transducer (1) according to either of claims 10 and 11 , wherein said indicators are calculated between pairs of homologous edges belonging to different signals, i.e. a rising edge of the first signal (SigA) and a rising edge of the second signal (Sige) or a falling edge of the first signal (SigA) and a falling edge of the second signal (Sigs).

13. The absolute position transducer (1) according to claim 12, wherein said indicators are also calculated between pairs of non-homologous edges belonging to different signals, i.e. a rising edge of the first signal (SigA) and a falling edge of the second signal (Sigs) or a falling edge of the first signal (SigA) and a rising edge of the second signal (Sigs).

14. The absolute position transducer (1) according to any one of the preceding claims, wherein said support (2) has further tracks, each of which has one pitch more or one pitch less than the immediately adjacent track.

15. A method for measuring the position of a support (2) having at least a first track (A) and a second track (S), said first track (A) comprising a first series of equally spaced pitches (PA), said second track (S) comprising a second series of equally spaced pitches (ps), the number of pitches (PA) of the first series being N and differing from the number of pitches (ps) of the second series by only one unit, said method comprising at least the following steps: - detecting a shift of the support (2) as a function of the positions assumed by said first track (A) and said second track (S) and thus providing a first signal (SigA) associated with the first track (A) and a second signal (Sigs) associated with the second track (S), said first signal (SigA) and said second signal (Sigs) having different periods;

- detecting rising edges (AR) and falling edges (AF) of the first signal (SigA) and rising edges (SR) and falling edges (SF) of the second signal (Sigs);

- calculating a plurality of time intervals between the detected edges (AR, AF, SR, SF);

- calculating the travel time of said shift as a function of said time intervals;

- calculating the position (i?) of the support (2) as a function of the travel time of the shift and of the time intervals.