Patent Publication Number: US-2021178606-A1

Title: Apparatus having a capacitive sensing system and electric line(s)

Description:
TECHNICAL FIELD 
     The present invention relates to an appliance, such as a robot, equipped with capacitive detection of object(s) and at least one electric line. 
     The field of the invention is, non-limitatively, that of the field of robotics, in particular the field of industrial robotics or service robots, for example medical or domestic, or also collaborative robots, also called “cobots”. 
     STATE OF THE ART 
     In the field of collaborative robotics, the robots can be equipped with capacitive sensors in order to detect the approach of objects or human operators in the vicinity of said robot. These sensors can for example comprise capacitive electrodes arranged in the form of sensitive surfaces that cover the surface of the robot at least partially. These capacitive electrodes are polarized at an alternating excitation potential, and connected to detection electronics that measures the capacitive coupling between these electrodes and objects polarized at a potential different from the electrodes, most usually ground. 
     These robots are generally equipped with tools or accessories, referenced to ground, and connected to control electronics or electric power supplies by electric cables that pass the length of the robot in cable runs. 
     When these cables are in proximity to a surface of capacitive sensors, they may be detected as obstacles and mistakenly trigger safety procedures. These cables can also interfere with the operation of the capacitive sensors in terms of accuracy and detection reach. 
     A solution may be to distance these cables so that they are outside of the detection zone of the capacitive sensors. But this solution risks collision between an object and said cables. 
     A purpose of the present invention is to overcome these drawbacks. 
     Another purpose of the invention is to propose a solution allowing the passage of a cable polarized at a potential different from the potential of a capacitive sensor in proximity to said capacitive sensor without interfering with the operation of said capacitive sensor. 
     It is also a purpose of the present invention to propose a solution allowing the passage of a cable polarized at a potential different from the potential of a capacitive sensor in proximity to said capacitive sensor without risk of collision with the neighbouring objects. 
     DISCLOSURE OF THE INVENTION 
     At least one of these purposes is achieved with an appliance comprising:
         at least one electrode, called measurement electrode, polarized at an alternating electrical potential, called detection electrical potential, different from a ground potential, at a frequency, called detection frequency, in order to detect at least one object in a detection zone,   at least one capacitive detection electronics, connected to said measurement electrodes, in order to detect a signal with respect to a capacitive coupling between said object and at least one measurement electrode, and   an electric line comprising at least one electric wire, in said detection zone.       

     The appliance according to the invention also comprises at least one spacing means for distancing said electric line in order to position it at a distance from the at least one measurement electrode comprised between:
         a distance, called minimum distance, corresponding to the distance beyond which an electric line, called reference electric line, with a predetermined dimension, generates a coupling capacitance with the at least one measurement electrode, less than a predetermined threshold capacitance; and   a distance, called maximum distance, corresponding to the distance beyond which an object, called reference object, with a predetermined dimension, greater than the dimension of said reference electric line, generates a coupling capacitance with the at least one measurement electrode less than said threshold capacitance.       

     In other words, the invention proposes to:
         choose a reference electric line with a predetermined dimension, and a reference object with a predetermined dimension greater than that of said reference electric line;   determine a distance, called minimum distance, starting from which the coupling capacitance between said reference electric line and the measurement electrode is less than the predetermined threshold capacitance; and   determine a distance, called maximum distance, starting from which the coupling capacitance between said reference object and the measurement electrode is less than the predetermined threshold capacitance.       

     Once the minimum distance and the maximum distance are determined, using a spacing means in order to position the electric line of the appliance between said minimum and maximum distances. 
     Thus, the device according to the invention proposes a specific positioning of the electric line with respect to the capacitive measurement electrodes. As a result, the device according to the invention makes it possible to avoid interferences, or detection errors, caused by the detection of the electric line by the measurement sensors. At the same time, the device according to the invention makes it possible to avoid the risks of collision between the electric line and the neighbouring objects since these objects themselves are detected when they approach the electric line. 
     In the present application, two alternating potentials are identical at a given frequency when they each comprise an identical or similar alternating component at said frequency; i.e. having the same amplitude (for example plus or minus a few percentage points) and the same phase (for example plus or minus a few degrees). Thus, the at least one of the two potentials identical at said frequency can also comprise a continuous component, and/or an alternating component having a frequency different from said given frequency. 
     Similarly, two alternating potentials are different at the given frequency when they do not have an identical or similar alternating component at this given frequency. 
     In the present application, the term “ground potential” or “general ground potential” denotes a reference potential of the electronics, of the appliance or of its environment, which can be for example an electrical ground. This ground potential can correspond to an earth potential or to another potential, connected or not to the earth potential. 
     Furthermore it is noted that generally, objects which are not in direct electrical contact with a particular electrical potential (electrically floating objects) tend to polarize by capacitive coupling at the electrical potential of other objects present in their environment, such as for example earth or electrodes, if the surface areas of overlap between these objects and those of the environment (or the electrodes) are sufficiently large. 
     In the present application, by “object” is meant any object or any person that may be located within the environment of the appliance. 
     Preferentially, the threshold capacitance can be determined by taking account of:
         a capacitance detection limit, dependent on a detection noise level of the capacitive detection electronics; and/or   an infinite capacitance, such as measured by the capacitive detection electronics in the absence of an object or electric line.       

     The infinite capacitance is the capacitance which exists between the electrodes and the environment, due to the presence of the electric charges in the electrode, and any elements of the environment. It thus corresponds to an asymptotic limit of the detection. It can also be variable as a function of the configuration or the position of the appliance on which the electrodes are positioned. In this case, the threshold capacitance can be determined by taking account of an infinite capacitance in a particular configuration of the appliance and/or its environment. 
     The detection noise level can take account, in particular, of electronic noises and gain and offset instabilities. 
     The capacitance detection limit can be determined starting from this detection noise level, and an acceptable signal to noise ratio. The capacitance detection limit can for example correspond to 10 times the detection noise level. 
     In general, the threshold capacitance can be defined as a capacitance, as measured by the capacitive detection electronics, starting from which it is considered that a distinct object in the environment of the appliance is present and detected. Conversely, it is thus possible to consider that no object is present when the capacitance measured is less than this threshold capacitance. 
     Non-limitatively, this threshold capacitance can be defined as, or starting from, an infinite capacitance, increased by the capacitance detection limit, or a quantity dependent on a detection noise level of the capacitive detection electronics. 
     Thus, any electric line with dimension less than or equal to that of the reference electric line, is no longer detected when it is beyond the minimum distance. In addition, any object with dimension greater than or equal to that of the reference object, is detected when it is located below the maximum distance. 
     Consequently, in the distance interval comprised between the minimum distance and the maximum distance:
         any electric line with dimension equal to or less than that of the reference line is not detected; while   any object with dimension equal to or greater than that of the reference object is detected.       

     Advantageously, the dimension of the reference electric line can correspond to a total diameter of the conductors of said reference line. 
     This total diameter can be defined as the diameter of a circle encompassing all of the conductors of the line. 
     Thus, the total diameter of the reference electric line used for the calculations must be chosen so that the diameter, or the total diameter, of the electric line used in the appliance in practice is less than the total diameter of said reference electric line. Or conversely, the electric line used in the appliance must have a total diameter less than or equal to the total diameter of the reference electric line. 
     The dimension of the reference object can correspond to:
         a width or a length of the reference object; or   a width or a length of a reference object, optionally fictitious, of the same width or the same length as the at least one measurement electrode.       

     The second condition can correspond to the fact that the dimension to be taken into account in order to determine a coupling capacitance between a reference object and an electrode is the smaller of the two dimensions, which corresponds to the overlap of the surfaces. 
     As explained above, the maximum positioning distance of the electric line, denoted D max , corresponds in fact to the upper boundary of the detection zone of the measurement electrodes, which is defined as the maximum distance at which a reference object, or a reference operator, with a minimum surface area, denoted S min,o , could be detected in air by the measurement electrodes, and thus generate a threshold capacitance, denoted C min , corresponding, for example, to the minimum capacitance exploitable by the detection electronics, in the sense of the noise threshold or the infinite capacitance as previously described. 
     This maximum distance D max  is evaluated with a dielectric of the air type (ε r =1), which is the least favourable condition. 
     The reference object can be for example a hand. The minimum surface area S min,o  can be defined as the overlap surface area between a measurement electrode and the reference object. 
     The minimum positioning distance of the line, denoted D min , corresponds to the distance starting from which the reference electric line starts to be detected by the measurement electrodes. This is produced when the electrode-line capacitance, denoted C el , is equal to the minimum capacitance C min . 
     Insofar as the reference electric line can be surrounded by sheaths and especially fixed on fixing elements, it is possible to 
     take account of a relative permittivity ε r  in calculating the coupling capacitance of the electric line C el . Thus: 
         C   el   =C   min   (1)
 
     I.e. by replacing C el  and C min  with their respective expressions according to the parallel-plate capacitor formula: 
     
       
         
           
             
               
                 
                   
                     
                       
                         ɛ 
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                       max 
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     where S min,c  is the overlap surface area between the reference electric line and the measurement electrode. Thus: 
     
       
         
           
             
               
                 
                   
                     D 
                     min 
                   
                   = 
                   
                     
                       
                         
                           ɛ 
                           r 
                         
                          
                         
                           S 
                           
                             min 
                             , 
                             c 
                           
                         
                       
                       
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                      
                     
                       D 
                       max 
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
     is obtained. 
     Thus, a spacing distance of the reference electric line, denoted D, with respect to the measurement electrode: 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           ɛ 
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                          
                         
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                   4 
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     is obtained. 
     The minimum positioning distance of the line D min  thus depends on the relationship of the surfaces of the reference electric line and of the reference object, and on the relative dielectric permittivity between the reference electric line and the measurement electrodes. 
     In practice, the following approximations can be made:
         the measurement electrodes can be rectangular or square with a dimension (width or length) of the order of 50 mm or 70 mm;   the reference object can correspond to a hand of an operator, for example of dimension (width) 90 to 100 mm; and   the electric lines used have a diameter (or an equivalent total diameter taking account of the curvature of the lines of the dielectric fields) of the order of 2 to 10 mm.       

     It is thus possible to assume, without too much loss of generality, that the reference object, the reference electric line and the measurement electrode can be approximated by rectangular shapes. It is also possible to assume that the reference object and the reference electric line are both larger than the measurement electrode in one dimension, for example the length. 
     With all of these approximations, and non-limitatively, the minimum distance and the maximum distance can be chosen in order to verify the following relationship: 
     
       
         
           
             
               
                 
                   
                     D 
                     min 
                   
                   = 
                   
                     
                       
                         
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                           L 
                           c 
                         
                       
                       
                         L 
                         o 
                       
                     
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                       max 
                     
                   
                 
               
               
                 
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     with:
         D min  the minimum distance,   D max  the maximum distance,   ε r  the overall (or average) relative permittivity of the spacing means,   L c  the dimension of the reference electric line, and   L o  the dimension of the reference object.       

     At least one spacing means can be produced by any manufacturing method, and in particular by moulding, injection, machining, 3D printing etc. 
     Preferentially, at least one spacing means can have an overall (or average) relative dielectric permittivity less than or equal to 2, in particular 1.5. 
     Thus, the influence of the spacing means on the capacitive detection is reduced, or even insignificant, and it is possible to minimize the minimum distance D min . 
     The spacing means can for example be produced from, or comprise, at least one dielectric material such as plastic, a polymer (polyvinyl chloride PVC, polyurethane, polyester, polyamide, acrylonitrile butadiene styrene ABS, etc.), or also wood, glass. 
     At least one spacing means can be fixed to a surface of the appliance according to the invention, in particular to an external surface of said appliance. 
     Alternatively, or in addition, at least one spacing means can be fixed to the electric line, and in particular around the electric line. 
     In addition, at least one spacing means can extend only or essentially between the appliance according to the invention and the electric line. 
     Consequently, the spacing means is located entirely between the electric line and the appliance according to the invention, with the optional exception of a fixing element or a strap around the cable. 
     Alternatively, or in addition, at least one spacing means can extend beyond the electric line, seen from the at least one measurement electrode. 
     Thus, such a spacing means makes it possible to constitute a contact surface that is beyond the electric line, so that it protects the electric line against impacts with external objects or surfaces, and/or conversely, that it protects objects from a direct contact with the electric line. 
     According to a particularly advantageously characteristic, the height of at least one spacing means can be adjustable and/or variable. 
     Thus it is possible to adapt, in particular on the fly, to different dimensions of electric lines, in the case for example of modification, addition, removal or replacement of an electric line. 
     At least one spacing means can be rigid. 
     Alternatively or in addition, at least one spacing means can be flexible. 
     Such a spacing means makes it possible to avoid damaging the electric line or the appliance when the appliance comprises an articulated part along which the electric line extends. 
     In fact, changing the position, and in particular the orientation of such an articulated part, can cause the spacing to vary between the electric line and said articulated part. The fact of using a flexible spacing means allows these spacing variations to be accommodated without damaging the electric line. 
     Such a situation can occur, in particular, when the appliance according to the invention is a robotized arm comprising articulated segments. 
     Moreover, the flexibility makes it possible to absorb or to minimize impacts with objects in the case of direct contact with the electric line or the spacing means. 
     In particular, at least one spacing means can be flexible and extend beyond the electric line, seen from the at least one measurement electrode. 
     This configuration makes it possible to absorb or minimize impacts with objects in the case of direct contact with the spacing means. It can also make it possible to generate a movement of the electric line, in the case of pressure, towards the measurement electrodes so that this line becomes detectable and thus makes it possible to detect the pressure. 
     Advantageously, at least one spacing means can be inflatable, and/or have the form of a cylindrical brush with radial bristles and/or, at least partly, hollow or spongy, or in the form of a foam. 
     Such a spacing means has in particular a reduced relative dielectric permittivity due to a high proportion of air in the volume. 
     The appliance according to the invention can also comprise at least one electrode, called guard electrode, arranged on the side opposite the detection zone with respect to the measurement electrodes, and polarized at a potential, called guard potential, that is identical to the detection potential at the detection frequency. 
     Such at least one guard electrode makes it possible to protect the measurement electrode or electrodes against the leakage capacitances or unwanted coupling, or interferences, that can be caused by parts of the appliance, which may not be at the detection potential, at the detection frequency. Thus, the range and the accuracy of the capacitive detection are improved. 
     The guard electrode or electrodes can be placed under the measurement electrode or electrodes, on the opposite side to the detection zone. 
     The capacitive detection implemented in the appliance according to the invention is based on the measurement/detection of a capacitive coupling signal between at least one measurement electrode and the object to be detected. 
     To this end, the capacitive detection electronics can comprise measurement electronics for, on the one hand:
         supplying the detection potential, and the guard potential if required, at the detection frequency; and   measuring/detecting a signal with respect to the electrode-object coupling.       

     According to an embodiment, the measurement electronics can comprise an operational amplifier (OA), or a circuit producing an operational amplifier, functioning as a transimpedance or charge amplifier, in which:
         a first input, for example an inverting input, is connected to one or more measurement electrodes, directly or via an optional polling means for example;   a second input, for example a non-inverting input, is connected to an oscillator supplying the detection potential and the guard potential; and   the output is looped on said first input via an impedance, and in particular via a capacitor.       

     In this configuration, the output of the OA supplies a voltage V s , the amplitude of which is proportional to the electrode-object capacitance, denoted C eo , between at least one measurement electrode and the object. 
     The output of the operational amplifier can be connected, directly or indirectly, to a module for measuring the voltage V s . This module for measuring the voltage V s  can comprise a signal conditioner, a demodulation such as a synchronous demodulation at the detection frequency, or an amplitude detection. 
     The detection electronics can also comprise an oscillator supplying the alternating detection potential and the guard potential if required. 
     Advantageously, the detection electronics can be at least partially electrically referenced to the detection potential. 
     The detection electronics can also comprise at least one calculation module arranged in order to determine a distance or an item of distance information, and/or a contact or an item of contact information, between at least one measurement electrode and the object, as a function of the signal with respect to the coupling capacitance C eo  originating from the signal conditioner. 
     This calculation module can for example comprise or be produced in the form of a microcontroller, or an FPGA. 
     The calculation module can also supply other items of information, such as triggering of alarms or safety procedures, when for example the measured distances are less than the predetermined distance thresholds. 
     Of course, the detection electronics can comprise components other than those described. 
     The detection electronics can be produced by digital components, or by analogue components, or even by a combination of digital components and analogue components. 
     In the appliance according to the invention, at least one electric line can be a line for the electric power supply of, and/or control of, and/or for communication with, an electric component part of said appliance. 
     The appliance according to the invention can have the form of a robot. 
     According to non-limitative embodiments, the robot can be or comprise any robotized system. 
     It can in particular have the form of, or comprise, for example a robotized arm, a mobile robot, a vehicle on wheels or tracks such as a truck equipped with an arm or a handling system, or a robot of the humanoid, gynoid or android type, optionally provided with movement component parts such as limbs. 
     In particular the appliance according to the invention can be a robot, in particular a robotized arm, comprising at least two segments connected together by an articulation, and comprising at least one spacing means at said articulation. 
    
    
     
       DESCRIPTION OF THE FIGURES AND EMBODIMENTS 
       Other advantages and characteristics will become apparent on examination of the detailed description of non-limitative examples and from the attached drawings in which: 
         FIG. 1  is a diagrammatic representation of a non-limitative embodiment of capacitive detection electronics that can be utilized in an appliance according to the invention; 
         FIGS. 2-4  are diagrammatic representations of non-limitative examples of spacing means able to be used in an appliance according to the invention; and 
         FIG. 5  is a diagrammatic representation of an example of a device according to the invention. 
     
    
    
     It is well understood that the embodiments that will be described hereinafter are in no way limitative. In particular, variants of the invention may 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. 
     In particular, all the variants and all the embodiments described may be combined together if there is no objection to such combination from a technical point of view. 
     In the figures, elements that are common to several figures retain the same reference. 
       FIG. 1  is a diagrammatic representation of a non-limitative embodiment of capacitive detection electronics that can be utilized in an appliance according to the invention. 
     The detection electronics  100 , shown in  FIG. 1 , can be produced in an analogue or digital form, or an analogue/digital combination. 
     The detection electronics  100  comprises an oscillator  102  delivering an alternating voltage, denoted V G , and referenced to a ground potential  104 . 
     The voltage V G  is used as guard potential in order to polarize one or more guard electrodes  106  via a line or several lines, and as excitation potential in order to polarize measurement electrodes  108   1 - 108   n , which may also be denoted by the reference  108 , or the reference  108   i , hereinafter. It can be any wave shape, for example sinusoidal or square, at a frequency or a fundamental frequency corresponding to the detection frequency. 
     The detection electronics  100  comprises a measurement electronics  110  in order to polarize the measurement electrodes  108  and measure a signal with respect to an electrode-object capacitance C eo  between an object and at least one measurement electrode  108 . 
     The measurement electronics  110  comprises a current, or charge, amplifier  112  represented by an operational amplifier (OA)  114  and a feedback capacitor  116  looping the output of the OA  114  at the inverting “−” input of the OA  114 . 
     In addition, in the example shown, the non-inverting “+” input of the OA  114  receives the voltage V G  and the inverting “−” input of the OA  114  is provided in order to be connected to each measurement electrode  108 , via a polling means  118 , which can be for example a switch, so as to poll the measurement electrodes  108  individually in turn. 
     Use of the polling means  118  is of course optional. 
     Under these conditions, the charge amplifier  112 , and in particular the OA  114 , supplies at the output a voltage V s  of amplitude proportional to the coupling capacitance C eo  between one or more measurement electrodes  108  connected at the “−” input thereof and an object in proximity, or in contact, with said measurement electrode  108 . 
     The measurement electronics  110  can also comprise a signal conditioner  120  making it possible to obtain a signal representative of the sought coupling capacitance C eo . This signal conditioner  120  can comprise for example a synchronous demodulator for demodulating the signal with respect to a carrier, at the detection frequency. The signal conditioner  120  can also comprise an asynchronous demodulator or an amplitude detector. This signal conditioner  120  can of course be produced in an analogue and/or digital form (microprocessor), and comprise all necessary means for filtering, conversion, processing etc. 
     The signal conditioner  120  measures and supplies the value of the voltage V s . 
     The detection electronics  100  can also comprise a calculation module  122  arranged in order to determine a distance or an item of distance information, and/or a contact or an item of contact information, between at least one measurement electrode  108  and an object, as a function of the signal with respect to the coupling capacitance C eo  originating from the signal conditioner  120 . 
     This calculation module  122  can for example comprise or be produced in the form of a microcontroller, or an FPGA. 
     The calculation module  122  can also supply other items of information, such as triggering of alarms or safety procedures, when for example the measured distances are less than predetermined distance thresholds. 
     Of course, the detection electronics  100  can comprise components other than those described. 
     The detection electronics  100 , or at least its sensitive part with the charge amplifier  112 , can be referenced (or supplied by electrical power supplies referenced) to the guard potential V G , in order to minimize the parasitic capacitances. 
     The detection electronics  100  can also be referenced, more conventionally, to the ground potential  104 . 
     Thus, when an object  124  enters the detection zone  126  of the measurement electrode or electrodes  108   1 - 108   n , this object  124  enters into capacitive coupling with at least one measurement electrode  108 , which modifies the capacitance seen by this measurement electrode  108 , and therefore the amplitude of the voltage V s  measured by the measurement electronics  110  connected to this measurement electrode  108 . 
       FIG. 2  is a diagrammatic representation of a non-limitative embodiment of an appliance according to the invention. 
       FIG. 2  shows, in a very partial manner, an appliance  200 , which can be for example a robot. 
     The appliance  200  comprises measurement electrodes  108   1 - 108   n , a single guard electrode  106 . Alternatively, the appliance  200  can comprise several guard electrodes. 
     The appliance  200  also comprises detection electronics, and in particular the detection electronics  100  in  FIG. 1 . 
     The appliance  200  is equipped with an electric line  202 . The electric line  202  can for example be provided in order to supply, or communicate with, an electrical component part (not shown) of said appliance  200 . 
     The appliance  200  is also equipped with a spacing means  204 . The spacing means  204  has the function of separating the electric line  202 , with respect to the measurement electrodes  108 , by a distance D comprised between:
         a minimum distance, denoted D min , beyond which a predetermined reference electric line, of diameter greater than the diameter of the electric line  202 , is no longer detected by the measurement electrodes  108 ; and   a maximum distance, denoted D max , beyond which a predetermined reference object, of dimensions smaller than the object  124 , is no longer detected by the measurement electrodes  108 .       

     As explained above, by taking approximations without too much loss of generality, the minimum and maximum distances are connected by the following relationship: 
     
       
         
           
             
               D 
               min 
             
             = 
             
               
                 
                   
                     ɛ 
                     r 
                   
                    
                   
                     L 
                     c 
                   
                 
                 
                   L 
                   o 
                 
               
                
               
                 D 
                 max 
               
             
           
         
       
     
     with:
         ε r  the relative permittivity of the spacing means  204 ,   L c  the dimension of the predetermined reference electric line, the diameter of which is greater than or equal to the diameter of the line  202 , and   L o  the dimension of a reference object the smallest dimension of which is less than or equal to the smallest dimension of the object  124 , or the dimension of the measurement electrodes  108 , if this is smaller.       

     According to a non-limitative embodiment given by way of illustration only:
         the reference object can be a hand, of dimension or width 90 to 100 mm;   the reference line can have a total diameter of the order of 5 mm; each measurement electrode can have a width of the order of 50 mm;   the relative permittivity of the spacing means (for example a hollow rigid plastic piece) can be 1.5; and   the maximum distance D max , determined starting from the dimension of the measurement electrodes  108  and from the minimum detectable capacitance C min , as described above, can be of the order of 100 mm.       

     Under these conditions, D min =15 mm is obtained. 
     Thus, by positioning an electric line  202  of diameter less than or equal to that of the reference line (5 mm) in an interval of distances between D min =15 mm and D max =100 mm of the measurement electrodes  108 , this electric line  202  is both not “seen” by the measurement electrodes  108  (which it therefore does not interfere with), and positioned in the detection zone  126  of the device, so that an approaching object  124  can be detected before entering into contact with this electric line  202 . Thus, the safety function of the collision detection is maintained despite the presence of the electric line  202 , and also with respect to this electric line  202 . 
     Of course, it may be desirable to define an interval in order to position the electric line contained in the interval (D min ; D max ), but distant from the boundaries thereof. It is possible for example to define a positioning interval of amplitude half or a quarter of the interval (D min ; D max ), positioned around the middle of the interval (D min ; D max ), or around another position. It is thus possible to optimize both the absence of detection of the cable  202  and the detection of objects  124  beyond this cable. 
     In the example in  FIG. 2 , the spacing means  204  have the form of a support that extends between the surface of the device  200  comprising the measurement electrodes  108  and the electric line  202 . The support  204  does not extend significantly beyond the electric line  202 , seen from the appliance  200 . 
     This support  204  can for example be produced in a rigid plastic material, with a hollow structure in order to maximize the volume of included air. 
     The support  204  is fixed to the surface of the appliance  200  comprising the measurement electrodes  108 , optionally above the measurement electrodes  108 , for example by a collar, preferably dielectric, or by any other known fixing means of the screwing, bonding etc. type. 
     The electric line  202  is fixed to the support  204  for example by a collar, or a strap, or by any other means. 
       FIG. 3  is a diagrammatic representation of another non-limitative embodiment of a spacing means that can be utilized in an appliance according to the invention. 
     The appliance represented in  FIG. 3  is the appliance  200  in  FIG. 2 . 
     Unlike in  FIG. 2 , in  FIG. 3 , the appliance  200  comprises a spacing means produced by a support  302  that extends beyond the electric line  202 . In other words, the support  302  does not stop at the electric line  202 . 
     The support  302  comprises a pass-through opening  304  in which the cable  202  is passed. The pass-through opening  304  can be closed. Alternatively, the pass-through opening  304  can be open, for example on the support side  302  or at a free end of said support  302 , to position the electric line  202  there. 
     The support  302  is fixed to the surface of the appliance  200  comprising the measurement electrodes  108 , for example by a collar, preferably dielectric, or by bonding. 
     The support  302  is preferably produced in a flexible and elastic material, for example from foam, intended to crush if an object  124  comes into pressing contact on its end face opposite the measurement electrodes  108 . Thus, the presence of a potentially damaging element on the appliance  200  is avoided. 
     Moreover, and in particular if the support  302  extends beyond the detection zone  126 , it can be arranged so that, in the case of pressure or crushing, the cable  202  moves towards the measurement electrodes  108  to a distance which allows its detection by these electrodes  108 , which makes it possible to detect the presence of an object even beyond the detection zone  126 . 
       FIG. 4  is a diagrammatic representation of another non-limitative embodiment of a spacing means that can be utilized in an appliance according to the invention. 
     The appliance represented in  FIG. 4  is the appliance  200  in  FIG. 2 . 
     Unlike in  FIG. 2 , in  FIG. 4 , the appliance  200  comprises a spacing means produced by a spacer  402  which is fixed to the electric line  202 , and no longer to the surface of the appliance  200  comprising the measurement electrodes  108 . 
     The spacer  402  extends on either side of the electric line  202  symmetrically or non-symmetrically. 
     The spacer  402  comprises a pass-through opening  404  in which the cable  202  is passed. The pass-through opening  404  can be closed. Alternatively, the pass-through opening  404  can be open, for example on the spacer side  402  or at a free end of the spacer  402 , to position the electric line  202  there. 
     The spacer  402  can be fixed, or mobile, along the electric line  202 . 
     The spacer can be produced, for example:
         in the form of a rigid or flexible case, placed around the cable  202  and which traps a volume of air or gas;   in the form on an inflatable element;   from foam; or   in the form of a cylindrical brush with radial bristles.       

       FIG. 5  is a diagrammatic representation of another non-limitative embodiment of an appliance according to the invention. 
     The appliance  500 , represented in  FIG. 5 , is a robot and in particular a robotized arm such as an industrial collaborative robot working under the supervision of, or in collaboration with, an operator, or also a medical robot in the case of a surgical operation on the body of a person, or also a personal assistance robot. 
     The robotized arm  500  comprises a fixed segment  502 , three articulated segments  504 - 508  and a functional head  510  fixed to the articulated segment  508 . The functional head  510  is a gripper equipped with an electric motor (not shown). 
     The robotized arm  500  comprises three articulations  512 - 514 , in particular motorized, making it possible to orientate the segments  504 - 508  according to the configuration sought. 
     Each segment  502 - 508  is equipped with measurement electrodes  108  in order to carry out a capacitive detection of objects located in the environment of the robot  500 , in particular placed in/on the outer case of said segment. 
     The robotized arm  500  comprises an electric line, such as for example the electric line  202 , in order to supply power to the functional head  510  and/or in order to communicate with the functional head  510  and a power supply and/or communication module  518  connected to the line  202 . 
     The robotized arm  500  comprises, at the level of the segment  504 , two spacing supports  204   1  and  204   2 , fixed to the segment  504 , in order to separate the electric line  202  from the measurement electrodes  108  placed on this segment  504 . Each of the spacing supports  204   1  and  204   2  can be the spacing support  204  in  FIG. 2 . 
     The robotized arm  500  comprises, at the level of the segment  506 , two spacing supports  302   1  and  302   2 , fixed to the segment  506 , in order to separate the electric line  202  from the measurement electrodes  108  placed on this segment  506 . Each of the spacing supports  302   1  and  302   2  can be the spacing support  302  in  FIG. 3 . 
     The robotized arm  500  comprises, at the level of each articulation  512 - 516 , a spacer, respectively  402   1 ,  402   2  et  402   3 , fixed to the electric line  202 , in order to separate the electric line  202  from the measurement electrodes  108  placed on the robotized arm  500 . Each of the spacers  402   1 ,  402   3  and  402   3  can be the spacer  402  in  FIG. 4 . 
     Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without exceeding the scope of the invention.