Test device for checking capacitive sensors and sensor testing method

Abstract

TITLE: Test device for checking capacitive sensors and sensor checking method. Test device (10) for checking capacitive distance sensors or protective installations incorporating capacitive distance sensors, comprising a test member (12) for simulating a reference object. The test member (12) is coupled by a capacitor (20) to a reference potential (22), the capacitance of which corresponds to that of the reference object with respect to the reference potential (22). Figure 1

Description

Title of the invention: Test device for testing capacitive sensors and sensor testing method FIELD OF THE INVENTION

[0001] The present invention relates to a testing device for controlling capacitive distance sensors or protection installations equipped with capacitive distance sensors and a method for controlling such sensors. STATE OF THE ART

[0002] Such a testing device is already known for controlling capacitive distance sensors or protection installations equipped with capacitive distance sensors, for example, for calibrating or checking distance sensors of industrial robots with human-machine interaction, to avoid risks to objects or people.

[0003] According to document DE 10 2010 064 328 A1, capacitive distance sensors are known which are fitted to industrial robots and which are associated with the parts, in particular the moving parts, of the robots. The distance sensors are used, for example, to avoid dangerous encounters causing injuries when a person approaches the industrial robot, to avoid this situation during the movement of the robot and the person.

[0004] In the context of the verification of force-limiting safety sensors, it is, for example, known according to document DE 10 2016 206 480 B4 to use a control or test device with a test surface having an installation provided with a variable spring constant to adapt the test installation to different manipulators to be verified.

[0005] DISCLOSURE AND ADVANTAGES OF THE INVENTION

[0006] The present invention relates to a test device for controlling capacitive distance sensors or protection installations comprising capacitive distance sensors, comprising a test member for simulating a reference object, the test member being coupled by at least one capacitor to a reference potential, the capacitance of this capacitor corresponding to the capacitance of the reference object with respect to the reference potential.

[0007] The test device as defined above, according to the invention, has the advantage of being adaptable to verify the correct functioning of the distance sensors in connection with the most diverse objects or test members. Thus, the test device according to the invention makes it possible to apply the most diverse distance sensors in the context of their use, for example, in connection with the gripping of objects or a person, in a particularly simple and universal manner. Furthermore, the method according to the invention makes it possible to check or control distance sensors in a particularly precise manner, i.e. exact and in a manner close to reality.

[0008] In the context of the above indications of test devices according to the invention for controlling capacitive distance sensors or protection installations comprising such distance sensors as defined above, it is provided that the control member comprises at least one capacitor coupled to a reference potential, the capacitance of this capacitor corresponding to the capacitance of the object to be detected with respect to the reference potential.

[0009] In other words, this means overall that the dimensioning of the capacitance of this capacitor on the test member imitates a reference object to be detected, for example the hand of a person approaching the distance sensor. For this, it is necessary that the test member has the same properties (electrical or electromagnetic) as the reference object from the point of view of the physical properties captured by the distance sensor, the values ​​or properties of the reference object being deduced from standards. The reference object is, for example, a reference object defined by a standard and whose geometry, material or other property are thus defined or specified. The fact that the test member is coupled to a particular capacitance of the capacitor thus makes it possible to adapt the test device to different reference objects in a particularly simple manner.

[0010] According to a preferred development of the test device, the reference potential corresponds to a reference potential of the distance sensor to be checked or of the protection installation to be checked.

[0011] According to one feature, in parallel with the capacitor at least one electrical resistor connects the reference object to the reference potential, the value of the resistor corresponding to the resistance of the reference object with respect to the reference potential. This applies in particular to capacitive distance sensors having low excitation frequencies or objects to be detected with a weakly ohmic connection to the reference potential.

[0012] In addition, it should be noted that both for the capacitor and also for the electrical resistance additional electrical resistances or other capacitive couplings or ohmic connections of the reference object are avoided, it is also possible to compensate by the value of the capacitor's capacitance or the value of the electrical resistance. Furthermore, the values ​​of the capacitor and the optional ohmic resistance are preferably those of the standards or those which are deduced from the standards. For the capacitive coupling of a person to the ground potential, reference will be made, for example, to the standard IEC / TR 61340-1.

[0013] For the optimal adaptation of the test organ to a reference object, it can further be provided that the permittivity (i.e. the electrical conductivity) and / or the geometry and / or the projection geometry of the test member correspond to the characteristics of the reference object. In the case of adaptation of the permittivity of the test member to that of the reference object, this allows, in particular in the near domain of the distance sensor, to have a more precise verification of the operation.

[0014] In connection with the verification of protective installations, for example, of protective devices equipping robot arms, comprising capacitive distance sensors, furthermore, according to a preferred development of the testing device, the testing member is connected at least indirectly to a force sensor assembly for capturing the forces applied to the testing member, the timing diagram of the forces obtained being captured, preferably, by an operating installation. It can thus be verified whether upon contact with the testing member no critical force or critical stress occurs on the testing member and which, in a real situation, could lead, for example, to damage to objects or injury to persons.

[0015] Alternatively or additionally, the test member is connected at least indirectly to a pressure sensor assembly for recording the (mechanical) pressures acting on the test member, the timing diagram of the pressures obtained being recorded, preferably, by another operating installation.

[0016] In particular, the force sensor assembly and / or the pressure sensor assembly, as already indicated, serve to detect forces or force peaks which occur, for example, in limitation installations or during a collision of a robot arm with an object or a person, in order to exploit these taking into account, for example, the limit values ​​given by directives and standards.

[0017] In a particularly preferential manner, in addition, at least the test member is installed on and / or adjustable on at least one spatial axis and preferably with a base equipped with distance measuring means. Such a base allows an optimal spatial adaptation between the distance sensor to be checked and the test member to be adjusted and in the case of a detection, the distance between the distance sensor and the test member is determined, for example, in a particularly simple manner.

[0018] According to a preferred development of such a base, the test member is preferably connected to an adjustment drive with a programmed adjustment speed for approaching the distance sensor to be tested. This makes it possible, for example, to carry out automated operation, i.e., an automated check of a distance sensor by bringing the test member closer, for example, using a defined approach speed, i.e., fixed within the framework of a standard, to the distance sensor and to stop the movement drive when the test member is gripped by the distance sensor. From the holding value of the test member until stopping, the distance between the test member and the distance sensor can be deduced. in the event of detection.

[0019] The invention also relates to a method for testing a capacitive distance sensor or a protective installation comprising capacitive distance sensors using a testing device as described above according to the invention. The method for testing a capacitive distance sensor or a protective installation equipped with capacitive distance sensors using a testing device comprises the following succession of steps consisting of:

[0020] - adjust at least the capacitance of the capacitor between the test organ and the potential of reference corresponding to the capacity of the reference object with respect to the reference potential, and

[0021] - position the test member relative to the distance sensor at a distance au- beyond the detection range of the distance sensor,

[0022] - reduce the distance between the test member and the distance sensor until the capture of the test organ by the distance sensor or until a safe operating state of the safety function performed by the protective installation is reached,

[0023] - enter the distance or a minimum detection distance between the test organ and the distance sensor for detecting the test device or when the safe operating state of the safety function performed by the protective installation is reached.

[0024] Preferably, the method is characterized in that the distance between the test member and the distance sensor is reduced and the signals from the distance sensor are automatically captured. Brief description of the drawings

[0025] The present invention will be described hereinafter in more detail with the aid of embodiments of the testing device and its method shown in the accompanying drawings in which:

[0026] [Fig-1] schematic representation of a test device for controlling capacitive distance sensors or protection installations comprising capacitive distance sensors,

[0027] [Fig.2] diagram of another testing device according to the invention,

[0028] [Fig.3] diagram of another testing device according to the invention,

[0029] [Fig.4] test device corresponding to [Fig.l] installed on a base comprising a distance measuring means also shown schematically,

[0030] [Fig.5] Test device according to [Fig.l] during a distance measurement with a distance sensor according to a schematic representation.

[0031] DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0032] In the following description, elements of the same function bear the same references in the different figures.

[0033] [Fig. 1] shows a test device 10 for testing capacitive distance sensors 1 ([Fig. 5]) or protective installations (not shown) comprising capacitive distance sensors 1, for example, to prevent collision between an industrial robot and objects or people, according to a greatly simplified representation. The test device 10 comprises a test member 12 fixed, for example, to a base 14. To fix different test members 12 on the base 14, it is possible to provide, for example, a standardized interface 16 (mechanical interface) between the test member 12 and the base 14.

[0034] The test member 12 of the exemplary embodiment shown is in the form of a plate 17 perpendicular to the plane of [Fig. 1]. The test member 12 is in particular a test member 12 conforming to a suitable standard and which imitates a reference object (not shown). In particular, the test member 12 has a geometry not shown in detail, for example, the geometry or the projection of a geometry of a hand; it is made of a material having defined mechanical or electrical properties. To ensure that it has the same properties as the reference object, the test member 12 is connected by a capacitor 20 to a reference potential 22 (electrical potential). The reference potential 22 is, for example, a reference potential 22 connected to ground or to a low external voltage or, preferably, to the same potential as that of the distance sensor 1 which only appears in [Fig. 5].It is important that the capacitance or capacitance value of capacitor 200 matches the capacitance of the reference object with respect to the reference potential 22. .

[0035] Optionally, the reference member 12 can also be connected to the reference potential 22 in parallel to the capacitor 20 by an electrical resistor 24; the value of the resistor 24 corresponds to the resistance of the reference object with respect to the reference potential.

[0036] [Fig. 2] shows a variant of the test device 10a compared to that of [Fig. 1]. This test device comprises, on the side facing the distance sensor 1 (not shown), a spacer member 25, for example, made of a rigid foam, with a relative permittivity close to unity. The spacer member 25 has a thickness (d) which corresponds to the minimum detection range (a) for capturing this minimum detection range (a).

[0037] [Fig. 3] shows another variant of the test device 10b. The test device 10b essentially corresponds to the test device 10 without the electrical resistor 24. In addition, the test device 10b has, on the side facing the distance sensor 1, a pressure sensor assembly 26 for recording the pressures acting (mechanically) on the test member 12. The pressure sensor assembly 26 is, preferably, a pressure sensor 26 or several pressure sensors 28 produced in a manner known per se, to allow local recording of the pressures exerted on the test member 12.

[0038] Furthermore, the region of the base 14 has a force sensor assembly 30 comprising at least one force sensor 32. The force sensor assembly 30 can capture the axial forces F acting on the test member 12 in particular perpendicular to the plane of the test member 12. Furthermore, the pressure sensor assembly 26 or the force sensor assembly 30 is coupled to a first evaluation installation 34 or to a second evaluation installation 36 which, in addition to capturing the absolute values, also captures the timing diagram of the pressures or forces.

[0039] [Fig. 4] shows a test setup 100 like the one used as an example in connection with the test device 10. The test device 10 is here fixed by its base body 12 to a base 38. A measuring installation 40 is additionally provided on the base 38 for recording the displacement of the base 14 and thus of the test member 12 in a direction perpendicular to the plane of the test member 12. Preferably, the base 38 or the base 14 are further coupled to a non-detailed adjustment drive 42 which makes it possible to move the base 14 and thus the test member 12 relative to the distance sensor 1 to be tested, along at least one of the axes (x, y, z) of a Cartesian coordinate system and, if appropriate, around the corresponding axes (x, y, z) of the coordinate system Cartesian. For this, a non-detailed 50 control installation is used.

[0040] To capture the minimum distance (b) between an area 52 to be protected, for example, a robot arm and the test member 12 corresponding to [Fig. 5], it is possible, for example, to move the test member 12 by the test assembly 100 in the direction of the arrow 53 relative to the distance sensor 1, until the distance sensor 1 captures the test member 12. For this, the distance sensor 1, whose electromagnetic field 54 is represented in [Fig. 5] by a semicircle, is, for example, coupled by an installation 60 which is at the reference potential; the installation 60 serves both to supply the distance sensor 1 and also to record the corresponding input quantities of the distance sensor 1 when the test member 12 is picked up. As soon as the test member 12 has been picked up, the distance (b) from the base 38 can, for example, be determined by the measuring installation 40, at which distance the distance sensor 1 picks up the test member 12.

[0041] In principle, the test device 10, 10a and 10b is designed both to detect the test member 12 as such and also the distance (b) and compliance with a minimum detection distance (a) of a distance sensor 1 to be validated. With the aid of the pressure sensor assembly 26 and the force sensor assembly 30 in the case of the test device 10b, this test device 10b is furthermore able to validate sensors of distance 1 equipping protective installations; the approach of the test organ 12 to be detected and the zone 52 to be protected or by contact, the residual risk such as, for example, the kinetic effect between the zone 52 and the test organ 12 is exploited.

[0042] To validate the detection of the test member 12, the test member 12 and at least the region to be monitored by the distance sensor 1 are made to overlap in space. The distance sensor 1 must then detect the test member 12. To verify the desired function of the distance sensor 1, the test member 12 and at least the region not to be monitored of the distance sensor 1 must also be overlapped in space. Then, the distance sensor 1 must not detect the test member 12. If the function for the entire monitored area of ​​the distance sensor 1 is to be verified, several positions of the distance sensor 1 must be checked or tested in the respective areas. If necessary, influencing parameters which influence the detection capability of the distance sensor 1 (e.g., air humidity, stray electric fields or the like) must be taken into account by proceeding empirically and analytically.

[0043] To validate the distance (b) of the test member 12 by the distance sensor 1, the test member 12 and the distance sensor 1 are brought closer to each other. The end of the approach can be done either in an automated manner (with a stopping stroke as short as possible) coupled to trigger recognition of the test member 12 by the distance sensor 1. In the case of detection, the measuring installation 40 makes it possible to measure the distance (b).

[0044] To validate a minimum detection distance (a), the test device 10a is preferably used with the spacer member 25. Thus, the test member 12 with the spacer member 25 is brought closer to the area 52 to be protected or to the distance sensor 1 until the area 52 and the spacer member 25 touch. In this case, the distance sensor 1 must generate a corresponding signal by capturing the test member 12.

[0045] In the case of protective installations comprising distance sensors 1 for detecting the test member 12 or the reference member, a distinction must be made between protective installations operating without contact or those operating in a tactile manner. To validate a protective installation operating without contact, the test member 12 is brought closer to the area to be protected 52. To validate a machine to be protected with areas monitored by distance sensors 1, such as, for example, a collaborative robot, the machine must preferably be brought closer to the test member 12 at the maximum foreseeable speed (v). Once the safe state has been reached (for example, an emergency stop of the robot), the minimum distance (b) between the area 52 to be protected and the test member 12 is measured. If the response time of the distance sensor 1 is monitored and if this corresponds to the longest foreseeable case, Correspondingly, moreover, all the parameters that influence the transition to the secure state of the worst case, we can validate the security of the system for a positive distance value.

[0046] If the parameters do not correspond to the worst-case state or if the response time is not monitored, the relationship between the parameters and the duration of the transition of the system to the safe state is, however, known analytically or sufficiently empirically to calculate the potentially necessary additional stopping travel and compare it to the minimum distance (b) separating the area to be protected and the test member 12.

[0047] If the minimum distance (b) is greater than or equal to the potentially necessary additional travel, the safety of the system can also be confirmed. If the relationships between the parameters and the duration of the transition to the safe state are not known, the test member 12 and the area 52 to be protected against contact can be brought closer together by repeating the operation several times until the safety of the system can be confirmed by a statistically significant probability of the requirements imposed on the system. For this, reference is made, for example, to a similar calculation method, according to ISO / TS 15066 and DIN EN ISO 13855.

[0048] To validate a protective installation with tactile operation, based on a sensor assembly comprising a distance sensor 1, for which the minimum distance between the zone to be protected 52 and the test member 12 is zero, there will thus be contact between the zone to be protected 52 and the test member 12. To exploit this contact, the test device 10b can be used, for example, for the protection of people with respect to moving parts of a machine. As with contactless validation, the test member 12 and the area to be protected 52 are brought together. Once the safe state (for example, emergency stop) has been reached in the case of a protective installation, the pressure and / or force curves acting on the test member 12 and obtained with the pressure sensor assembly 26 or the force sensor assembly 30 are used. If these curves are within predefined limit values, the safety of the system can also be confirmed.

[0049] In addition, it should be noted that it is possible to use the means described for the validation of protective installations with tactile operation, with other residual risks such as, for example, an electrical risk due to voltages, a risk linked to high temperatures or to dangerous products, etc. For this, a suitable sensor (ammeter, temperature sensor, harmful product sensor and others) is used with the support member 12 which metrologically captures the residual risk in the event of contact and allows exploitation.

[0050] The test devices 10, 10a, 10b described above can be modified in various ways without departing from the scope of the invention.

[0051] Thus, it is possible, for example, to envisage that for validation, multi-channel systems are used for the test devices 10a, 10b with the possibility of combining in AND logic, security channels to trigger the transition to the secure state of the system to be verified.

[0052] NOMENCLATURE OF MAIN ELEMENTS

[0053] (numeric references without alphabetical suffixes)

[0054] 1 Distance sensor

[0055] 10 Test device

[0056] 12 Test organ

[0057] 14 Basic body

[0058] 17 Plate

[0059] 20 Capacitor

[0060] 22 Reference potential

[0061] 24 Electrical resistance

[0062] 26 Pressure sensor assembly

[0063] 29 Pressure sensor

[0064] 30 Force sensor assembly

[0065] 32 Force sensor

[0066] 34 First operating installation

[0067] 36 Second operating installation

[0068] 40 Measuring installation

[0069] 50 Control installation

[0070] 52 Area to be protected

[0071] 53 Arrow

[0072] 54 Electromagnetic field

[0073] 60 Installation

[0074] 100 Test assembly

[0075] a Minimum detection range

[0076] b Distance

[0077] Thickness

Claims

Claims

1. Test device (10; 10a; 10b) for testing capacitive distance sensors (1) or protective installations equipped with capacitive distance sensors (1), comprising a test member (12) for simulating a reference object, - the test member (12) being coupled by at least one capacitor (20) to a reference potential (22), and - the capacitance of this capacitor (20) corresponds to the capacitance of the reference object with respect to the reference potential (22).

2. Test device according to claim 1, characterized in that the reference potential (22) corresponds to the reference potential (22) of the distance sensor (1) to be tested or of the protective installation to be tested.

3. Test device according to claim 1 or 2, characterized in that - at least one electrical resistor (24) connects the test member (12) to the reference potential (22), in parallel to the capacitor (20), - the value of this resistor corresponds at least to the resistance (24) of the reference object with respect to the reference potential (22).

4. Test device according to one of claims 1 to 3, characterized in that the permittivity and / or the projection geometry of the test member (12) correspond to those of the reference object.

5. Test device according to one of claims 1 to 4, characterized in that the test member (12) is connected at least indirectly to a force sensor (30) for recording the force (F) acting on the test member (12), the timing diagram of the force (F) obtained being recorded, preferably, by an operating installation (36).

6. Test device according to one of claims 1 to 5, characterized in that - the test member (12) is connected at least indirectly to a pressure sensor (26) for recording the mechanical pressures exerted on the test member (12), - the timing diagram of the pressures obtained is recorded, preferably, using another operating installation (34).

7. Testing device according to one of claims 1 to 6, characterized in that at least the testing member (12) can be adjusted in one and / or around at least one spatial axis (x, y, z) of a Cartesian coordinate system and preferably with a base (38) provided with a distance measuring device (40).

8. Test device according to claim 7, characterized in that the test member (12) is connected to a programmed adjustment drive (42) of its adjustment speed to approach the distance sensor (1) to be tested.

9. Test device according to one of claims 1 to 8, characterized in that the test member (12) comprises at least one further sensor for detecting a risk.

10. Test device according to one of claims 1 to 9, characterized in that - the test member (12) comprises a spacer member (25) having a thickness (d) which corresponds to the minimum detection range (a) of the distance sensor (1), and - the material of the spacer member (25) preferably has a relative permittivity close to the unity value.

11. Method for testing capacitive distance sensors (1) or protective installations equipped with capacitive distance sensors (1) using a testing device (10, 10a, 10b) according to one of claims 1 to 10 and comprising the following sequence of steps: - setting at least the capacitance of the capacitor (20) between the test member (12) and the reference potential (22) corresponding to the capacitance of the reference object with respect to the reference potential (22), - positioning the test member (12) relative to the distance sensor (1) at a distance beyond the detection range of the distance sensor (D, - reducing the distance between the test member (12) and the distance sensor (1) until the test member (12) is captured by the distance sensor (1) or until a safe operating state of the safety function is reached carried out by the protection installation,and - enter the distance (b) or a minimum detection distance (a) between, the test member (12) and the distance sensor (1) for detecting the test member (12) or when the safe operating state of the safety function applied by the protective installation is reached.

12. A method according to claim 11, characterized in that the distance between the test member (12) and the distance sensor (1) is reduced and the signals from the distance sensor (1) are automatically captured.

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