PROXIMITY AND PRESSURE DETECTION DEVICE, DETECTION LAYER AND ITEM OF EQUIPMENT EQUIPPED WITH SUCH DEVICES

Abstract

A device for detecting an object, with respect to a detection surface, including at least one measuring electrode, at least one emission electrode coupled to the measuring electrode by a piezoresistive layer, and measurement electronics, configured so as to bias the electrodes at the same alternating potential and perform a measurement, called capacitive measurement, of a first measured signal (Vs) relating to the capacitance (Coe), called object-electrode capacitance, seen by the at least one measuring electrode; apply a potential difference between the electrodes and measure a second signal relating to the resistance (Rie) between the electrodes. Also, a detection layer includes such a detection device as well as an item of equipment equipped with such a detection layer.

Claims

1. A device for detecting an object with respect to a detection surface, comprising: at least one electrode, called measuring electrode; at least one electrode, called emitting electrode, electrically coupled to said measuring electrode by a piezoresistive layer; a measurement electronics, configured to polarize at least one measuring electrode at a first alternating potential (V.sub.1), different from a ground potential (M), at an operating frequency, and to perform a measurement, called capacitive measurement, of a first measurement signal (V.sub.s) relating to the capacitance (C.sub.oe), called object-electrode capacitance, seen by said at least one measuring electrode; the measurement electronics is further configured to: apply a potential difference, direct or alternating, between said at least one measuring electrode and an emitting electrode that is coupled thereto; and perform a measurement, called resistive measurement, of a second measurement signal (V.sub.s) relating to the resistance (R.sub.ie), called inter-electrode resistance, between said measuring electrode and said emitting electrode.

2. The device according to claim 1, characterized in that it comprises at least one guard electrode, disposed facing measuring and emitting electrodes, with respect to the faces thereof opposite to the detection surface.

3. The device according to claim 2, characterized in that the piezoresistive layer has, between at least one measuring electrode and one emitting electrode that is coupled thereto, a resistance having a value identical to, or close to, the value of the impedance formed between said measuring electrode and the guard electrode, at the operating frequency of the capacitive measurement.

4. The device according to claim 1, characterized in that, for at least one measuring electrode, the piezoresistive layer is disposed along the face of the emitting and measuring electrodes on the side of the detection surface.

5. The device according to claim 1, characterized in that, for at least one measuring electrode, the piezoresistive layer is disposed along the face of the emitting and measuring electrodes on the side opposite to the detection surface.

6. The device according to claim 1, characterized in that the piezoresistive layer comprises at least one of: a foam filled with conductive particles; a carbon foam; and/or a piezoresistive film.

7. The device according to claim 1, characterized in that a measuring electrode and at least one emitting electrode with which it is coupled, are disposed at the same level, with respect to the detection surface.

8. The device according to claim 1, characterized in that a measuring electrode and at least one emitting electrode with which it is coupled are disposed one above another, with respect to the detection surface.

9. The device according t claim 1, characterized in that a measuring electrode occupies a greater extent than that occupied by at least one emitting electrode with which it is coupled.

10. The device according to claim 1, characterized in that a measuring electrode is coupled with a single emitting electrode.

11. The device according to claim 1, characterized in that a measuring electrode is coupled with several emitting electrodes.

12. The device according to claim 1, characterized in that a measuring electrode is interlaced, or interdigitated, with at least one, in particular each, emitting electrode that is coupled thereto.

13. The device according to claim 1, characterized in that the measurement electronics comprises an amplifier of the transimpedance type configured to measure a current or a load on the measuring electrode.

14. The device according to claim 1, characterized in that it comprises: a first oscillator supplying the first alternating potential (V.sub.1); a second oscillator supplying a second direct or alternating electrical potential (V.sub.2) to the measuring electrode, or to each emitting electrode, for the resistive measurement.

15. The device according to claim 1, characterized in that said device further comprises a synchronous demodulation stage configured to perform a synchronous demodulation of each of the first and second signals.

16. A detection layer comprising at least one detection device according to claim 1.

17. An item of equipment including a detection device according to claim 1.

18. An item of equipment according to claim 17, characterized in that said item relates to a robot or a part of a robot, mobile or fixed.

19. An item of equipment including a detection layer according to claim 16.

Description

DESCRIPTION OF THE FIGURES AND EMBODIMENTS

[0139] Other advantages and characteristics will become apparent from the examination of the detailed description of an embodiment that is in no way limitative, and from the attached drawings in which

[0140] FIGS. 1-2 are diagrammatic representations, in a cross section view, of non-limitative embodiment examples of arrangements of electrodes capable of being utilized in a detection device according to the invention;

[0141] FIGS. 3-5 are diagrammatic representations, in a top view, of non-limitative embodiment examples of a combination of measuring and emitting electrodes capable of being utilized in a device according to the invention;

[0142] FIGS. 6-9 are diagrammatic representations of non-limitative embodiment examples of a detection device according to the invention;

[0143] FIG. 10 is a diagrammatic representation of a non-limitative embodiment example of an item of equipment equipped with a detection layer according to the invention; and

[0144] FIG. 11 is a diagrammatic representation of another non-limitative embodiment example of an item of equipment according to the invention.

[0145] It is well understood that the embodiments that will be described hereinafter are in no way limitative. It is possible in particular to envisage variants of the invention comprising only a selection of the characteristics described hereinafter, in isolation from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention with respect to the state of the prior art. This selection comprises at least one, preferably functional, characteristic without structural details, or with only a part of the structural details if this part alone is sufficient to confer a technical advantage or to differentiate the invention with respect to the state of the prior art.

[0146] In the figures, the elements common to several figures retain the same reference.

[0147] FIG. 1 is a diagrammatic representation, in a cross section view, of a non-limitative embodiment example of an arrangement of electrodes capable of being utilized in a detection device according to the invention.

[0148] The arrangement of electrodes 100, shown in FIG. 1, is used to detect on the one hand proximity, i.e. approach and contact, and on the other hand pressure exerted by an object O with respect to a detection surface S.

[0149] The arrangement 100 comprises one or more capacitive electrodes 102, called measuring electrode.

[0150] The arrangement 100 further comprises, for each measuring electrode 102, at least one capacitive electrode 104, called emitting electrode, electrically coupled with said measuring electrode 102.

[0151] The electrical coupling between the measuring electrode 102 and the emitting electrode 104 is performed by a layer of piezoresistive material 106 in electrical contact with the electrodes.

[0152] According to an optional but particularly advantageous characteristic, the arrangement of electrodes 100 can comprise a capacitive electrode 108, called guard electrode, which has the function of electrically guarding at least the measuring electrode 102. To this end, the guard electrode 108 is polarized at the same alternating potential as the measuring electrode 102, at the operating frequency.

[0153] In the example shown in FIG. 1, the guard electrode is disposed behind the measuring 102 and emitting 104 electrodes, seen from the detection surface S.

[0154] The guard electrode 108 is separated from the measuring 102 and guard 104 electrodes by a dielectric layer 110.

[0155] The arrangement of electrodes 100 is provided to be connected to a measurement electronics (not shown in FIG. 1) to polarize the measuring electrode 102, the emitting electrode 104 and the guard electrode 108, and to measure: [0156] during a capacitive measurement, a first signal relating to a capacitance C.sub.oe, called object-electrode capacitance, seen by said at least one measuring electrode 102; and [0157] during a resistive measurement, a second signal relating to a resistance (R.sub.ie), called inter-electrode resistance, between said measuring electrode 102 and said emitting electrode 104.

[0158] In the example shown in FIG. 1, the measuring electrode 102 and the emitting electrode 104 are disposed at the same level and the layer of piezoresistive material 106 is disposed over these electrodes 102 and 104, on the side of the detection surface S.

[0159] In this configuration, the measuring 102 and emitting 104 electrodes can be produced in one and the same conductive layer, for example.

[0160] The layer of piezoresistive material 106 further forms a prolongation of the measuring electrode 102 for the capacitive measurement, to the extent that its surface towards the object is the one that participates in the capacitive detection of proximity of this object, i.e. in the capacitive detection of approach and contact. The apparent surface area of the measuring electrode “seen” by the object can then be greater than the surface area of the measuring electrode itself, which contributes to an increase in the reach of the capacitive detection.

[0161] In addition, in this configuration, the piezoresistive layer 106 is located on the side of the object O and forms the layer of contact with the object O. In order to avoid a coupling or an electrical contact between the object O and the piezoresistive layer 106, the latter can be covered with a dielectric thin layer 112 or a film, flexible or not, such as for example a thin layer of paint or lacquer.

[0162] The detection surface S with respect to which the approach, the contact and the pressure are detected can then be merged with the upper face of said dielectric film 112.

[0163] FIG. 2 is a diagrammatic representation of another non-limitative embodiment example of an arrangement of electrodes capable of being utilized in a detection device according to the invention.

[0164] The arrangement 200, shown in FIG. 2, comprises all the elements of the arrangement 100 in FIG. 1.

[0165] In the arrangement 200, and unlike the arrangement 100, the piezoresistive layer 106 is disposed under, or behind, the measuring 102 and emitting 104 electrodes seen from the detection surface.

[0166] In particular, la piezoresistive layer 106 is located between on the one hand the measuring 102 and emitting 104 electrodes, and on the other hand the dielectric layer 110 and the guard electrode 108. It should be noted that if the resistance of the piezoresistive layer 106 is sufficiently high, the dielectric layer 110 can be omitted.

[0167] The dielectric film 112 is disposed on the electrodes 102 and 104 to avoid an electrical coupling or contact between these electrodes and the object when the object comes into contact with these electrodes.

[0168] In this configuration, the piezoresistive layer 106 scarcely participates in the capacitive detection and therefore does not constitute an extension of the measuring electrode 102.

[0169] This configuration has the advantage that the apparent surface area of the measuring electrode “seen” by the object O is well defined as being that of the measuring electrode 102, which can increase the precision of the spatial localization of the capacitive detection.

[0170] FIG. 3 is a diagrammatic representation of a non-limitative embodiment example of a combination of electrodes capable of being implemented in a detection device according to the invention.

[0171] In the example shown in FIG. 3, a single emitting electrode 104 is electrically coupled with a measuring electrode 102, via the piezoresistive layer 106.

[0172] The piezoelectric layer 106 can be located below, or above, the electrodes 102 and 104, seen from the detection surface S.

[0173] The measuring 102 and emitting 104 electrodes are interlaced or interdigitated, so as to measure over one and the same portion of surface both the object-electrode capacitance C.sub.oe and the inter-electrode resistance R.sub.e. This architecture makes it possible to have one and the same spatial resolution for the capacitive measurement and for the resistive measurement.

[0174] Of course, the invention is not limited to a specific structure and any structure of electrodes, whether or not interlaced (or interdigitated), is possible.

[0175] FIG. 4 is a diagrammatic representation of another non-limitative embodiment example of a combination of electrodes capable of being implemented in a detection device according to the invention.

[0176] In the example shown in FIG. 4, a measuring electrode 102 is electrically coupled with several, in particular four, emitting electrodes 104.sub.1-104.sub.4 via a single piezoresistive layer 106, common to all the emitting electrodes 104.sub.1-104.sub.4.

[0177] The piezoresistive layer 106 can be located below, or above, the electrodes 102 and 104.sub.1-104.sub.4, seen from the detection surface.

[0178] Each emitting electrode 104.sub.1-104.sub.4 is interdigitated, or interlaced, with a part of the measuring electrode 102.

[0179] This architecture makes it possible to have a better and finer spatial resolution of the resistive measurement, with respect to the spatial resolution of the capacitive measurement.

[0180] The capacitive detection of approach and contact does not require high spatial resolution, since for an object detected at a significant distance, for example greater than the size of the electrode, the field lines of the electrode splay out and the spatial resolution becomes limited by principle. In addition, detecting approach is often applied to detecting a human or an object in a machine environment in a factory, or in a hospital, for which the objects to be detected are of significant size. On the other hand detecting pressure requires better spatial resolution in order to manipulate an object, imitate a human through touch or handling; which justifies the fact of proposing a better spatial resolution for the resistive detection in comparison with the capacitive detection.

[0181] In the example given in FIG. 4, the capacitive detection zone corresponds to the extent of the measuring electrode 102. In addition, by sequentially exciting or selecting the four emitting electrodes 104.sub.1-104.sub.2, it is possible to measure the pressure in sub-regions of the capacitive detection zone, with an improved spatial resolution: by a factor of 4 in the example shown.

[0182] In the example shown in FIG. 4, the piezoresistive layer is common to all the emitting electrodes 104.sub.1-104.sub.4.

[0183] FIG. 5 is a diagrammatic representation of another non-limitative embodiment example of a combination of electrodes capable of being implemented in a detection device according to the invention.

[0184] The example given in FIG. 5 comprises all the elements of the example given in FIG. 4, with the exception of the differences described below.

[0185] In the example shown in FIG. 5, the emitting electrodes 104.sub.1-104.sub.4 are not coupled to the measuring electrode 102 by a single common piezoresistive layer, as in FIG. 4.

[0186] In FIG. 5, unlike FIG. 4, each emitting electrode 104.sub.1-104.sub.4 is connected to the measuring electrode 102 by an individual piezoelectric layer, respectively 106.sub.1-106.sub.4, that is independent from the other emitting electrodes.

[0187] Each piezoresistive layer 106.sub.1-106.sub.4 can be presented in the form of an individual disc independent from the other piezoresistive layers 106.sub.1-106.sub.4.

[0188] Each piezoresistive layer 106.sub.1-106.sub.4 can be located below, or above, the electrodes 102 and 104.sub.1-104.sub.4, seen from the detection surface.

[0189] As explained above, the piezoresistive layer or layers can be produced in different ways.

[0190] In particular, in the examples illustrated, the or each piezoresistive layer can, for example, be formed by a flexible polymer foam filled with carbon particles in the form of carbon black.

[0191] There will now be described, with reference to FIGS. 6-9, different embodiment examples of a detection device according to the invention capable of implementing any one of the arrangements 100 and 200 of electrodes in FIGS. 1-2 combined with any one of the combinations of electrodes in FIGS. 3-5.

[0192] FIG. 6 is a representation of a non-limitative embodiment example of a detection device according to the invention.

[0193] The device 600, shown in FIG. 6, comprises a multitude of measuring electrodes 102.

[0194] In FIG. 6, a single measuring electrode 102 is shown.

[0195] The device 600 comprises, for each measuring electrode 102, at least one emitting electrode 104 coupled to said measuring electrode 102 by a piezoresistive layer 106.

[0196] A guard electrode 108 can be disposed under each measuring electrode 102 and the at least one emitting electrode 104 that is coupled thereto.

[0197] The detection device 100 further comprises a measurement electronics 602 comprising an amplifier of the transimpedance type configured to measure a current or a load on the measuring electrode 102. The transimpedance amplifier 602 is formed by an operational amplifier (OA) 604, the output of which is looped into one of the inputs via a feedback capacitor 606 and a feedback resistor 608. The OA 604 supplies a voltage V.sub.s at output.

[0198] The device 600 further comprises a first oscillator 610, referenced to a ground potential M, which supplies a first alternating potential V.sub.1 (relative to the ground M) or a first alternating potential difference V.sub.1. According to an example that is in no way limitative:

V.sub.1=E.cos(2πf.sub.1t).

[0199] The first alternating potential V.sub.1 is also the guard potential for the capacitive measurement.

[0200] The device 600 further comprises a second oscillator 612, referenced to the first potential V.sub.1, which supplies a second alternating potential V.sub.2 (or a second alternating potential difference V.sub.2) having a frequency different from V.sub.1. According to an example that is in no way limitative:

V.sub.2=E.cos(2πf.sub.2t).

[0201] The device 600 further comprises a synchronous demodulation stage 614 for performing a synchronous demodulation of the signal V.sub.s supplied by the OA 604. In the device 600, the demodulation stage 614 comprises: [0202] a first synchronous demodulator 616 performing a synchronous demodulation of the signal V.sub.s with a carrier wave identical to the first alternating potential V.sub.1 delivered by the first oscillator 610, and [0203] a second synchronous demodulator 618 performing a synchronous demodulation of the signal V.sub.s with a carrier wave identical to the second alternating potential V.sub.2 delivered by the second oscillator 612.

[0204] Furthermore, a switch 620 makes it possible to connect the measuring electrode 102 selectively: [0205] either to the OA 604 when this measuring electrode 102 is used to perform a measurement: in this case, this measuring electrode 102 is called “active”; [0206] or directly at the first potential V.sub.1 when this measuring electrode 102 is not used to perform a measurement: in this case this measuring electrode 102 is called “passive” and constitutes a guard element for the capacitive measurement.

[0207] Optionally, the detection device 600 can further comprise a control module 622. For example, the control module 622 can be arranged to control the switch 620 for connecting the measuring electrode 102 to the OA 604 and triggering one or more measurements.

[0208] In the example shown in FIG. 6, the output of the OA 604 is looped into its inverting input “−” by the condenser 606 and the resistor 608. The inverting input of the OA 604 is connected to the measuring electrode 102. In addition, the non-inverting input “+” of the OA 604 is connected to the second oscillator 612, itself connected to the first oscillator 610, the latter being referenced to the ground potential M. The measuring electrode 104 and the guard electrode 108 are connected between the first oscillator 110 and the second oscillator 112, so that they are always polarized at the first alternating potential V.sub.1, or guard potential.

[0209] Under these conditions, the voltage V.sub.s supplied by the OA 604 comprises: [0210] a first component, at the frequency f.sub.1, which is a function of the coupling capacitance C.sub.oe between the measuring electrode 102 and the object O; and [0211] a second component, at the frequency f.sub.2, which is an inverse function of the resistance R.sub.ie between the emitting electrode 104 and the measuring electrode 102.

[0212] The synchronous demodulation of V.sub.s in the first synchronous demodulator 616 with the carrier wave V.sub.1 supplies a variable G1 that is a function of the object-electrode capacitance C.sub.oe between the object O and the measuring electrode 102. This variable G1 makes it possible to have information on the proximity of the object O with respect to the measuring electrode 102, and therefore with respect to the detection surface S.

[0213] The synchronous demodulation of V.sub.s in the second synchronous demodulator 618 with the carrier wave V.sub.2 supplies a variable G2 that is an inverse function of the inter-electrode resistance R.sub.ie between the measuring electrode 102 and the emitting electrode 104. This variable G2 makes it possible to have information on the pressure, or the press, applied by the object O on the piezoresistive layer 108, and therefore on the detection surface S.

[0214] In particular, as the measuring electrode 102 is connected to the inverting input of the OA 604, and the second oscillator 612 to the non-inverting input of the OA 604, the variable G2 is a function of the inverse of the resistance of the piezoresistive layer 108. This (1/x) dependency has the advantage of improving the linearity of the detection device, since the law of natural variation of the resistance of a piezoresistive layer is an inverse function of pressure. It is thus possible to best exploit the measurement dynamics of the device according to the invention for the resistive measurement, to efficiently detect a light contact, for example for lifting a flexible beaker, just as well as heavy pressure, for example for assisting a person with their movements.

[0215] In the device 600, the electronic components can be referenced via their feeds to the general ground M, in standard fashion.

[0216] In order to improve the rejection of the unwanted capacitances, the sensitive detection components such as the OA 604 and optionally the synchronous demodulation stage 614 can also be referenced to the guard potential V.sub.1.

[0217] FIG. 7 is a representation of another non-limitative embodiment example of a detection device according to the invention.

[0218] The device 700, shown in FIG. 7, comprises all the elements of the device 600 in FIG. 6.

[0219] Unlike the device 600 in FIG. 6, in the device 700 in FIG. 7, the second oscillator 612 is disposed between the first oscillator and the emitting electrode 104.

[0220] Thus, in the device 700 this second oscillator excites the emitting electrode 104 and not the measuring electrode 102, as is the case in the device 600 in FIG. 6.

[0221] FIG. 8 is a representation of another non-limitative embodiment example of a detection device according to the invention.

[0222] The device 800 shown in FIG. 8 comprises all the elements of the device 600 in FIG. 6, with the exception of the differences described below.

[0223] In the device 800 in FIG. 8, several emitting electrodes 104.sub.1-104.sub.N, with N≥2 are coupled to the measuring electrode 102 via a single common piezoresistive layer 108, or individual piezoresistive layers.

[0224] The device 800 comprises a switch 802 that makes it possible to selectively connect each of the emitting electrodes 104.sub.1-104.sub.N in turn to the potential V.sub.1, during the resistive measurement. Thus, it is possible to measure sequentially a variable G2.sub.1-G2.sub.N for each of the emitting electrodes 104.sub.1-104.sub.N representative of the resistance between each of the emitting electrodes 104.sub.1-104.sub.N and the measuring electrode 102.

[0225] In this example, a resistive measurement is performed sequentially, or in turn, for each of the emitting electrodes 104.sub.1-104.sub.N.

[0226] Of course, it is possible to combine the embodiment examples in FIGS. 7 and 8 and to use a second source to excite sequentially each of the emitting electrodes 104.sub.1-104.sub.N.

[0227] In the devices 600, 700 and 800, the second oscillator 612 delivers an alternating potential V.sub.2 of frequency f.sub.2, different from the frequency f.sub.1 of the first alternating potential V.sub.1. In this case, the variables G1 and G2 can be deduced from one and the same measurement signal so that the capacitive measurement and the resistive measurement are performed simultaneously. Alternatively, the variables G1 and G2 can be deduced from two measurement signals V.sub.s obtained one after another, sequentially.

[0228] In addition, in the devices 600, 700 and 800, the variables G1 and G2 can be deduced simultaneously or sequentially, via two separate demodulators.

[0229] Alternatively, the variables G1 and G2 can be obtained sequentially via a single synchronous demodulator used in turn to obtain the variable G1, then the variable G2, from one and the same measurement signal V.sub.s or from different measurement signals.

[0230] In the devices 600, 700 and 800, the second oscillator 612 delivers an alternating potential V.sub.2. Alternatively, it is possible to replace this second oscillator by a direct-current electrical source delivering a direct-current voltage E.

[0231] In all cases where the capacitive measurement and the resistive measurement (or the resistive measurements) are performed sequentially, the first oscillator 610 can be guarded powered on or powered off during the, or each, resistive measurement. Similarly, the second oscillator 612 can be guarded powered on or powered off during the, or each, capacitive measurement. In this case, by powering on each of the two oscillators alternately, they can generate the same potential difference (V.sub.1=V.sub.2), or a potential difference at the same frequency (f.sub.1=f.sub.2).

[0232] In the devices 600, 700 and 800, a second oscillator 612 is used. Of course, it is possible to use only a single oscillator to perform the capacitive and resistive measurement(s). In this case, the capacitive measurement and the resistive measurement must be performed sequentially.

[0233] FIG. 9 is a representation of another non-limitative embodiment example of a detection device according to the invention.

[0234] The device 900 shown in FIG. 9 comprises all the elements of the device 600 in FIG. 6, with the exception of the differences described below.

[0235] Unlike the device 600, the device 900 comprises only the first oscillator 610 and does not comprise the second oscillator 612.

[0236] In addition, the device 900 comprises only the first demodulator 616 and does not comprise the second demodulator 618.

[0237] The device 900 comprises a contact switch 902 that selectively connects the non-inverting input of the OA 604 either at the first alternating potential V.sub.1 or at the ground potential M.

[0238] Thus, to perform the capacitive measurement, the contact switch 902 is connected at the first alternating potential V.sub.1. Under these conditions, the measuring electrode 102, the emitting electrode 104 and the guard electrode 108 are at the first alternating potential V.sub.1 and a first signal V.sub.s is measured. This first signal V.sub.s is representative of the object-electrode capacitance C.sub.oe and is demodulated in the first demodulator 616 to obtain the variable G1, having as carrier wave the alternating potential V.sub.1.

[0239] In order to perform the resistive measurement, the contact switch 902 is connected at the ground potential M. Under these conditions, the measuring electrode 102 is no longer polarized at the first alternating potential V.sub.1, but at the ground potential M. The emitting electrode 104 and the guard electrode 108 are still at the first alternating potential V.sub.1 and a second signal V.sub.s is measured. This second signal V.sub.s is representative of the resistance R.sub.ie between the measuring electrodes 102 and the, or each, emitting electrode 104. This second signal V.sub.s is demodulated in the first demodulator 616 to obtain the variable G2, still having as carrier wave the first alternating potential V.sub.1.

[0240] Of course, according to an alternative, it is possible to guard the measuring electrode 102 at the first alternating potential V.sub.1 during the resistive measurement, and to polarize the emitting electrode 104 at another potential, and in particular at the ground potential M.

[0241] In all the embodiments, it is advantageous to choose for the piezoresistive layer 106 a resistance having a value identical to, or close to, the value of the impedance formed between the measuring electrode 102 and the guard electrode 108, at the operating frequency of the capacitive measurement, i.e. the frequency f.sub.1 in the examples described. For example, the resistance value of the piezoresistive layer 106 can be greater than 1 kΩ, and preferably greater than several kΩ.

[0242] Regardless of the embodiment described, it is possible to perform a calibration of the resistive measurement. To this end, the measuring electrode 102 and the emitting electrode 104 are polarized at the first alternating potential V.sub.1. If this capacitive measurement signals the absence of an object, then a resistive measurement is performed. This resistive measurement will then supply a threshold value relating to the resistance of the piezoresistive layer 106 at rest, in the absence of any pressure. It also makes it possible to verify correct operation of the device.

[0243] With the devices 600, 800 and 900, it is further possible to perform a diagnosis of the capacitive measurement. This diagnosis can be performed as follows. In the absence of any object, a resistive measurement can be performed by applying the potential difference V.sub.2 between the measuring electrodes 102 on the one hand, and the emitting 104 and guard 108 electrodes on the other hand. The measurement signal V.sub.s, supplied by the measurement electronics 602, can then be on the one hand phase-demodulated and on the other hand quadrature-demodulated with the potential V.sub.2. The result supplied by one of the demodulations (for example the phase demodulation) supplies the resistive measurement, and that supplied by the other demodulation (for example quadrature demodulation) is representative of the capacitance between the measuring electrodes 102 and the guard electrodes 108. These results can be compared to expected values, in particular to verify correct operation of the system.

[0244] FIG. 10 is a representation of a non-limitative embodiment example of an item of equipment according to the invention.

[0245] The item of equipment 1000 in FIG. 10 is a robot, and in particular a robotized arm comprising several articulated segments, connected together by rotary articulations.

[0246] The robotized arm 1000 includes two trim elements 1002 and 1004 disposed on two segments of the robotized arm 1000.

[0247] Each trim element 1002-1004 comprises one or more detection devices according to the invention, such as for example any one of the devices 600, 700, 800 or 900 in FIGS. 6-9.

[0248] The detection electronics of different detection devices equipping the trim elements 1002 and 1004 can be separate, or partially or entirely common.

[0249] The electrodes of each detection device equipping the trim elements 1002-1004 are integrated within the thickness of said trim element 1002-1004, or disposed on one or more of the faces of said trim element 1002-1004.

[0250] The trim elements 1002-1004 are used either instead of an original trim element of the robotized arm 1000, or in addition to an original trim element.

[0251] FIG. 11 is a diagrammatic representation of another non-limitative embodiment example of an item of equipment according to the invention.

[0252] The item of equipment 1100, shown in FIG. 11, is a robot in animal form.

[0253] The robot 1100 is provided with a head 1102, a body 1104 and four legs allowing said robot 1100 to move around.

[0254] The robot 1100 is equipped with a covering in the form of a skin 1106, arranged over a part of the body 1104, as illustrated, or over the entire body. The skin 1106 can be attached onto the body 1104 in such a way that it can be removed or dismantled. It can comprise a holding layer, for example a fabric sewn so as to have the desired shape.

[0255] The skin 1106 comprises one or more detection devices according to the invention, such as for example any one of the devices 600, 700, 800 or 900 in FIGS. 6-9.

[0256] Of course, the invention is not limited to the examples detailed above.