Series redundant capacitive sensing device

Abstract

A device for capacitive detection of an object with respect to a detection surface, including: at least one capacitive detection electrode, and detection electronics including at least one item of measurement electronic equipment, for: polarizing the at least one detection electrode at an alternating excitation potential (VG), different from a ground potential; measuring a measurement signal relative to an electrode-object capacitance; and the detection electronics also includes, for the measurement electronics, at least two separate calculation modules, operating in parallel, and supplying two independent detection signals for one and the same measurement signal originating from the measurement electronics.

Claims

1. A device for capacitive detection of an object with respect to a detection surface, comprising: at least one capacitive detection electrode; and electronics; detection electronics comprising at least one item of electronic equipment, called measurement electronics, for: polarizing said at least one detection electrode at an alternating potential (VG), called excitation potential, different from a ground potential; measuring a signal, called measurement signal, relative to a capacitance, called electrode-object capacitance, between each detection electrode and said object; and the detection electronics also comprises, for said at least one measurement electronics, at least one first and one second separate calculation modules, operating in parallel, and supplying at least two independent detection signals for one and the same measurement signal originating from the measurement electronics.

2. The device according to claim 1, characterized in that the detection electronics also comprises a control module arranged to compare the detection signals supplied by the first and second calculation modules.

3. The device according to claim 1, characterized in that the detection electronics comprises at least one capacitance, called reference capacitance, used to verify and/or calibrate the operation of the measurement electronics and/or of at least one calculation module.

4. The device according to claim 1, characterized in that it also comprises at least one electrode, called guard electrode, to guard at least one detection electrode, said at least one guard electrode being polarized at an alternating guard potential (VG) identical or substantially identical to the excitation potential at at least one working frequency, at least during measurement of a measurement signal relative to an electrode-object capacitance.

5. The device according to claim 4, characterized in that for at least one detection electrode, at least one test electrode is formed by a guard electrode, or a part of a guard electrode, associated with said detection electrode.

6. The device according to claim 1, characterized in that it comprises, for at least one detection electrode, at least one electrode, called test electrode, arranged to verify, during a verification sequence, the operation of said detection electrode by: polarizing said test electrode and said detection electrode at electrical potentials different to at least one working frequency, and measuring a signal relative to the capacitance, called test capacitance, between said test electrode and said detection electrode.

7. The device according to claim 6, characterized in that it comprises a means for modifying the polarization of the at least one test electrode, respectively of the at least one detection electrode, between a measurement sequence and a verification sequence, so as to polarize said at least one electrode: during a verification sequence: at a first electrical potential (VT) different from the excitation potential (VG) at at least one working frequency, and during a measurement sequence: at a second alternating potential (VG), identical or substantially identical to said excitation potential at at least one working frequency, or corresponding to said excitation potential.

8. The device according to claim 7, characterized in that the first potential is one of: the ground potential, or a potential (VT) identical to the excitation potential, but having a different amplitude.

9. The device according to claim 1, characterized in that the at least one measurement electronics comprises a polling means to poll at least a part of the detection electrodes, sequentially.

10. The device according to claim 1, characterized in that the detection electronics is at least partially referenced electrically to the alternating excitation potential (VG).

11. The device according to claim 1, characterized in that each detection electrode carries out a capacitive detection for a detection location of the detection surface, at least one detection electrode comprising at least one first and one second independent electrodes, called measurement electrodes.

12. The device according to claim 11, characterized in that, for at least one detection electrode: the first and second measurement electrodes are juxtaposed in a non-interleaved manner; or one from the first and second measurement electrodes is at least partially interleaved with the other of said measurement electrodes; or the first and second measurement electrodes are at least partially interleaved with one another.

13. A detection layer, for an item of equipment, fitted with a detection device according to claim 1.

14. The detection layer according to claim 13, characterized in that it comprises, along a face, a plurality of detection electrodes distributed according to a matrix arrangement.

15. The detection layer according to claim 13, characterized in that it comprises: along a face, at least one detection electrode, and along another face, at least one guard electrode and/or at least one test electrode.

16. The detection layer according to claim 13, characterized in that it has the form of a rigid or resilient trim element.

17. An item of equipment fitted with a detection layer according to claim 13.

18. An item of equipment fitted with a detection device according to claim 1.

19. The item of equipment according to claim 18, characterized in that it is a robot, a robotized handling arm or a robot segment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other advantages and characteristics will become apparent on examination of the detailed description of examples that are in no way limitative, and from the attached drawings, in which:

(2) FIGS. 1-5 are diagrammatic representations of five non-limitative embodiment examples of a capacitive detection device according to the invention;

(3) FIGS. 6a-6e are diagrammatic representations of embodiment examples of a capacitive detection electrode that can be implemented in a device according to the invention; and

(4) FIG. 7 is a diagrammatic representation of an embodiment example of a robot fitted with a detection device according to the invention.

DETAILED DESCRIPTION

(5) It is well understood that the embodiments that will be described hereinafter are in no way limitative. Variants of the invention can in particular be envisaged comprising only a selection of 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.

(6) In particular, all the variants and all the embodiments described can be combined together if there is no objection to this combination from a technical point of view.

(7) In the figures, elements common to several figures keep the same reference.

(8) FIG. 1 is a diagrammatic representation of a first non-limitative embodiment example of a capacitive detection device according to the invention.

(9) The detection device 100, shown in FIG. 1, can be produced in an analogue or digital form, or an analogue/digital combination.

(10) The detection device 100 comprises several capacitive detection electrodes 102, only one of which is shown in FIG. 1 for the sake of clarity.

(11) The detection device 100 also comprises one or more guard electrodes 104, to electrically guard said detection electrodes 102. Similarly, a single guard electrode is shown in FIG. 1 for the sake of clarity.

(12) The device 100 can comprise a single guard electrode 104 forming a guard plane common to several, or all, the detection electrodes 102, or an individual guard electrode 104 for each detection electrode.

(13) The detection device 100 also comprises detection electronics 106. The detection electronics 106 comprises in particular a measurement electronics 108 connected to the detection electrode 102 and to the guard electronics 104.

(14) The measurement electronics 108 comprises a current, or charge, amplifier 110 represented by an operational amplifier (OA) 112 and a feedback capacitor 114 looping the output of the OA 112 to the inverting “−” input of the OA 112.

(15) An oscillator 116, referenced to a ground potential 118, supplies an alternating excitation voltage, denoted V.sub.G. This alternating excitation voltage is also used as a guard potential in order to polarize the guard electrodes 104.

(16) In the example shown, the non-inverting “+” input of the OA 112 receives the voltage V.sub.G and the inverting “−” input of the OA 112 is provided to be connected to each detection electrode 102 via a polling means 120, which can be for example a switch, so as to poll a set of “n” detection electrodes 108 individually in turn. The switch 120 is also arranged to connect the detection electrodes 102, either to the OA, or to the guard potential.

(17) Under these conditions, the charge amplifier 110, and in particular the OA 112, supplies at the output a voltage V.sub.s at an amplitude proportional to the coupling capacitance C.sub.eo, called electrode-object capacitance, between the detection electrode 102 connected to the “−” inverting input thereof and an object in proximity to, or in contact with, said detection electrode 102.

(18) The measurement electronics 108 can also optionally comprise a signal conditioner 122 making it possible to obtain a signal representative of the sought coupling capacitance C.sub.eo. This signal conditioner 122 can comprise, for example, a synchronous demodulator for demodulating the signal with respect to a carrier wave, at a working frequency. The signal conditioner 122 can also comprise an asynchronous demodulator or an amplitude detector. This signal conditioner 122 can of course be produced in an analogue and/or digital form (microprocessor), and comprise all necessary means for filtering, conversion, processing etc.

(19) The signal conditioner 122 measures and supplies the value of the voltage V.sub.S.

(20) The detection electronics 106 comprises, for the measurement electronics 108, at least one first calculation module 124 and one second calculation module 126 that are separate, operating in parallel, and supplying at least two independent detection signals for one and the same measurement signal originating from the measurement electronics 108.

(21) A third, optional, calculation module 128, can be placed between the measurement electronics 108, and the first and second calculation modules 124 and 126.

(22) Each calculation module 124-128 can be produced by, or comprise, a microprocessor, or a chip (FPGA), or independent logic elements (comparators, etc.).

(23) The detection electronics 106 also comprises a control module 130 arranged to carry out a comparison of the signals supplied by the first and second calculation modules 124 and 126, and to verify the correct operation of the detection device 100. The control module 130 can transmit an alarm signal or a safety signal in case of failure of the detection device 100.

(24) In the example shown in FIG. 1, the control module 130 can be formed by an independent processor, or a chip.

(25) As specified above, the measurement electronics 108 supplies at the output a voltage value V.sub.s, or an equivalent variable, in numerical form.

(26) According to a first embodiment, the first, second and third calculation modules 124-128 can be arranged to carry out the following operations: from the signal supplied by the measurement electronics 108, the third calculation module 128 calculates a distance value between an object and the detection electrode 102, and supplies this distance value to the calculation modules 124 and 126; and independently, each calculation module 124 and 126 compares this distance to a threshold distance value corresponding to a safety distance or a contact between the detection electrode 102 and an object, and supplies a signal relative to the crossing of said safety distance or to said contact. This signal can be an analogue, numerical signal, or a closing or opening of a relay.

(27) According to a second embodiment, the first, second and third calculation modules 124-128 can be arranged to carry out the following operations: from the signal supplied by the measurement electronics 108, the third calculation module 128 calculates a capacitance value between an object and the detection electrode 102, and supplies this capacitance value to the calculation modules 124 and 126; and independently, each calculation module 124 and 126 compares this capacitance value to a threshold capacitance value corresponding to a safety distance or a contact between the detection electrode and an object, and supplies a signal relative to the crossing of said safety distance or to said contact. This signal can be an analogue, numerical signal, or a closing or opening of a relay.

(28) According to a third embodiment, the first, second and third calculation modules 124-128 can be arranged to carry out the following operations: from the signal supplied by the measurement electronics 108, the third calculation module 128 calculates a capacitance value between an object and the detection electrode 102, and supplies this capacitance value to the calculation modules 124 and 126; and independently, each calculation module 124 and 126: calculates a distance value from the capacitance value supplied by the third calculation module 128; and compares this distance value to a threshold distance value corresponding to a safety distance or a contact between the detection electrode 102 and an object, and supplies a signal relative to the crossing of said safety distance or to said contact. This signal can be an analogue, numerical signal, or a closing or opening of a relay.

(29) According to another embodiment example, the detection device 100 may not comprise a third calculation module 128. The first and second calculation modules 124-126 can be arranged to carry out the following operations: from the signal supplied by the measurement electronics 108, each calculation module 124 and 126 independently calculates a distance value between an object and the detection electrode 102, compares this distance to a threshold distance value corresponding to a safety distance or a contact between the detection electrode 102 and an object, and supplies a signal relative to the crossing of said safety distance or to said contact. This signal can be an analogue, numerical signal, or a closing or opening of a relay.

(30) The detection electronics 106, or at least its sensitive part with the charge amplifier 110, can be referenced (or supplied by electrical power supplies referenced) to the guard potential V.sub.G, in order to minimize the parasitic capacitances.

(31) The detection electronics 106 can also be referenced, more conventionally, to the ground potential 118.

(32) FIG. 2 is a diagrammatic representation of a second non-limitative embodiment example of a capacitive detection device according to the invention.

(33) The detection device 200, shown in FIG. 2, comprises all the elements of the device 100 in FIG. 1, except the control module 130.

(34) Unlike the device 100, in the device 200 the control module has the form of two subassemblies 130.sub.1 and 130.sub.2. The sub-module 130.sub.1 is integrated in the first calculation module 124 and the sub-module 130.sub.2 is integrated in the second calculation module 126.

(35) Each sub-module 130.sub.1-130.sub.2 communicates with the other sub-module 130.sub.1-130.sub.2 to transmit thereto the signal calculated by the calculation module 124-126 in which it is integrated. Each sub-module 130.sub.1-130.sub.2 compares the signal originating from the control module 124-126 in which it is implanted with the signal originating from the other calculation module 124-126. The control sub-module 130.sub.1-130.sub.2 (or the first calculation module 124 and/or the second calculation module 126) can transmit an alarm signal or a safety signal in case of failure of the detection device 100. This arrangement allows optimal operational redundancy and safety since each calculation module 124-126 is monitored by two independent control sub-modules 130.sub.1-130.sub.2.

(36) FIG. 3 is a diagrammatic representation of a third non-limitative embodiment example of a capacitive detection device according to the invention.

(37) The detection device 300, shown in FIG. 3, comprises all the elements of the device 100 in FIG. 1.

(38) The device 300, and in particular the detection electronics 106 of the device 300, also comprises a reference capacitance 302 which is used to carry out a calibration or a verification of the operation of the detection device 300, during a verification sequence.

(39) The reference capacitance(s) is(are) connected to the inverting input of the charge amplifier 110 by virtue of the polling means 120, in order to carry out the verification sequence. In this case, all the detection electrodes 102 are connected to the guard potential. If the measured value of the reference capacitance 302 is correct then there is no failure to be signaled. In the opposite case, in particular if the measured value of the reference capacitance 302 is outside of a range of acceptable predefined values, the detection device 300 is faulty and the control module 130 signals this failure by an alarm signal or a safety signal. The measured value of the reference capacitance 302 can also be used, in so far as it is within the range of acceptable values, to carry out a calibration of the detection electronics 106.

(40) The verification sequence can be carried out before or after each measurement sequence applied to a set of several detection electrodes 102, or before or after each measurement of a detection electrode 102.

(41) Of course, the reference capacitance 302 can also be implemented in the device 200 in FIG. 2.

(42) FIG. 4 is a diagrammatic representation of a fourth non-limitative embodiment example of a capacitive detection device according to the invention.

(43) The detection device 400, shown in FIG. 4, comprises all the elements of the device 100 in FIG. 1.

(44) The device 400 also comprises a second oscillator 402, referenced to the ground potential 118 and supplying an alternating potential V.sub.T identical to the guard potential V.sub.G but having a different amplitude, in particular a weaker amplitude.

(45) The device 400 also comprises an electrical switch 404 making it possible to switch the polarization of the detection electrode 102 such that: in a first position of the switch 404, shown in FIG. 4, the detection electrode 102 is polarized at the potential V.sub.G; and in a second position of the switch 404, the detection electrode 102 is polarized at the potential V.sub.T.

(46) The device 400 makes it possible to use the guard electrode 104 as test electrode and to measure the capacitance, called test capacitance, denoted C.sub.T, between the detection electrode 102 and the guard electrode 104. The value of the test capacitance C.sub.T being known, it is possible to detect a failure of the detection device 400.

(47) The test capacitance C.sub.T can be measured during a verification sequence during which the detection electrode 102 is polarized with the potential V.sub.T by switching the switch 404 into its second position.

(48) The verification sequence can be carried out before or after each measurement sequence applied to a set of several detection electrodes 102, or before or after each measurement of a detection electrode 102.

(49) According to an alternative, the switch 404 can be used to modify the polarization of the guard electrode 104, in place of the detection electrode 102.

(50) According to another alternative, the switch 404 can be omitted and replaced with a second oscillator 402 which supplies either the alternating potential V.sub.T, or the excitation or guard potential V.sub.G.

(51) Of course, the device 400 can also utilize the reference capacitance 302 of the device 300. In this case, the verification sequence can carry out a measurement both of the test capacitances for the detection electrodes 102 and of the reference capacitance 302.

(52) FIG. 5 is a diagrammatic representation of a fifth non-limitative embodiment example of a capacitive detection device according to the invention.

(53) The detection device 500, shown in FIG. 5, comprises all the elements of the device 400 in FIG. 4.

(54) In the device 500, unlike the device 400, the guard electrode 104 is produced in three independent parts: 104.sub.1-104.sub.3.

(55) The switch 404 is used to modify only the polarization of the part 104.sub.2 of the guard electrode 104. In particular, the electrical switch 404 makes it possible to switch the polarization of the part 104.sub.2 of the guard electrode 104 such that: in a first position of the switch 404, shown in FIG. 5, the part 104.sub.2 of the guard electrode 104 is polarized at the potential V.sub.G; and in a second position of the switch 404, the part 104.sub.2 of the guard electrode 104 is polarized at the potential V.sub.T.

(56) The other parts 104.sub.1 and 104.sub.3 of the guard electrode 104 are always polarized at the guard potential V.sub.G.

(57) The device 400 makes it possible, during a verification sequence, to use the part 104.sub.2 of the guard electrode 104 as test electrode and to measure the capacitance, called test capacitance, denoted C.sub.T, between the detection electrode 102 and the part 104.sub.2 of the guard electrode 104. The value of the test capacitance C.sub.T being known, it is possible to detect a failure of the detection device 500. Of course: the part 104.sub.2 of the guard electrode 104 forming a test electrode can be specific to one detection electrode 102, or common to several detection electrodes 102; the device 500 can comprise one or a plurality of test electrodes formed respectively by one or a plurality of parts 104.sub.2 of guard electrode 104.

(58) The verification sequence can be carried out before or after each measurement sequence applied to a set of several detection electrodes 102, or before or after each measurement of a detection electrode 102.

(59) According to an alternative, the switch 404 can be omitted and replaced by a second oscillator 402 which supplies either the alternating potential V.sub.T or the excitation or guard potential V.sub.G.

(60) Of course, the device 400 can also utilize the reference capacitance 302 of the device 300. In this case, the verification sequence can carry out a measurement both of the test capacitances for the detection electrodes 102 and of the reference capacitance 302.

(61) Each detection electrode 102 can be formed by one single measurement electrode.

(62) Alternatively, each detection electrode 102 can be produced by several, and in particular two, measurement electrodes, capable of being polled by the detection electronics 106 in turn or sequentially. Thus, it is possible to obtain for each detection location, a redundant detection by virtue of several measurement electrodes.

(63) FIGS. 6a-6e give five embodiment examples of a detection electrode that can be implemented in a capacitive detection device according to the invention.

(64) In FIG. 6a, the detection electrode 102 is formed by a first measurement electrode 602, entirely interleaved with a second measurement electrode 604. The second measurement electrode 604 completely surrounds the first measurement electrode 602. The connection tracks can then be produced on another layer of conductor.

(65) In FIG. 6b, the detection electrode 102 is formed by a first measurement electrode 602, entirely interleaved with a second measurement electrode 604. The second measurement electrode 604 does not completely surround the first measurement electrode 602 and has the form of a “C”.

(66) In FIG. 6c, the detection electrode 102 is formed by a first measurement electrode 602, and a second measurement electrode 604 which are interleaved with one another. Each measurement electrode has the shape of a comb. The combs are interleaved with one another.

(67) In FIG. 6d, the detection electrode 102 is formed by four measurement electrodes 602-608 which are interleaved with one another in threes. The measurement electrodes 602 and 604 are identical and face one another. The measurement electrodes 606 and 608 are identical and face one another.

(68) Each measurement electrode is interleaved with the two measurement electrodes which are adjacent to it.

(69) In FIG. 6e, the detection electrode 102 is formed by a first measurement electrode 602, juxtaposed with a second measurement electrode 604.

(70) FIG. 7 is a diagrammatic representation of a robot equipped with trim elements according to the invention.

(71) The robot 700 shown in FIG. 7, is a robotized arm comprising several segments that are articulated and connected to one another by rotary articulations.

(72) The robot 700 comprises two trim elements 702 and 704 placed on two segments of the robot 700.

(73) Each trim element 702-704 comprises a detection device according to the invention, such as for example any one of the detection devices in FIGS. 1-5.

(74) The detection electronics of the detection devices equipping the trim elements 702 and 704 that can be separate, or partially or completely common.

(75) The detection electrodes 102 of each detection device equipping the trim elements trim 702-704 are integrated in the thickness of said trim element, or arranged on a face or the faces of said trim element 702-704.

(76) The trim elements 702-704 also comprise a guard layer to avoid parasitic couplings between the detection electrodes and the structure of the robot.

(77) The trim elements 702-704 are used either in place of an original trim element of the robot, or in addition to an original trim element.

(78) Of course, the invention is not limited to the examples that have just been described, and numerous modifications may be made to these examples without exceeding the scope of the invention.