DE102021214983A1 - Testing device and method for checking capacitive distance sensors or protective devices having capacitive distance sensors - Google Patents

Abstract

The invention relates to a testing device (10; 10a; 10b) for testing capacitive distance sensors (1) or protective devices having capacitive distance sensors (1), with a test body (12) for simulating a reference object, the test body (12) having at least one capacitor (20) is coupled to a reference potential (22).

Description

technical field

The invention relates to a testing device for testing capacitive distance sensors or protective devices having capacitive distance sensors, for example for calibrating or testing distance sensors in industrial robots that are used in an interaction between man and machine in order to avoid endangering objects and/or people. Furthermore, the invention relates to a method using a testing device according to the invention.

State of the art

From the DE 10 2010 064 328 A1 The applicant is aware of capacitive distance sensors in connection with industrial robots, which are arranged on the surface of, in particular, moving parts of the industrial robot. The distance sensors are used, for example when a person approaches the industrial robot, to prevent dangerous encounters that can lead to injuries between the industrial robot and the person when it is moving.

In connection with the review of force-limiting safety sensors, it is, for example, from the DE 10 2016 206 480 B4 It is known to provide a test device with a test surface that has a variable spring constant device in order to be able to adapt the test device to different manipulators to be tested.

Disclosure of Invention

The test device according to the invention for checking capacitive distance sensors or protective devices having capacitive distance sensors with the features of claim 1 has the advantage that it can be adapted to check the proper functionality of the distance sensors in connection with a wide variety of objects or test specimens. The testing device according to the invention thus makes it possible to use a wide variety of distance sensors in a particularly simple and universal manner with regard to their use, for example in connection with the detection of objects or a person. Furthermore, the method according to the invention makes it possible to test the distance sensors in a particularly precise or accurate and realistic manner.

Against the background of the above explanations, it is therefore provided in a test device according to the invention for testing capacitive distance sensors or protective devices having capacitive distance sensors with the features of claim 1 that it has a test body which is coupled to a reference potential via at least one (electrical) capacitor , wherein the capacitance of the at least one capacitor corresponds to the capacitance of an object to be detected with respect to the reference potential.

In other words, overall this means that a reference object to be detected, for example a human hand approaching the distance sensor, is imitated by the dimensioning of the capacitance of the at least one capacitor on the test body. For this it is necessary that the test body has the same (electrical or electromagnetic) properties as the reference object with regard to the physical properties detected by the distance sensor, with the values or properties of the reference object being able to be derived from standards. The reference object can be, for example, a reference object defined in a standard, which is defined or specified with regard to its geometry, its material or other properties. The fact that the test body can be coupled to a special capacitance of the capacitor makes it possible to adapt the test device to different reference objects in a particularly simple manner.

Advantageous developments of the testing device according to the invention for testing capacitive distance sensors or protective devices having capacitive distance sensors are listed in the dependent claims.

In a preferred embodiment of the testing device, it is provided that the reference potential corresponds to a reference potential of the distance sensor to be tested or the protective device to be tested.

Provision can also be made for at least one electrical resistor connecting the reference object to the reference potential to be provided parallel to the capacitor, the resistance value of the at least one resistor corresponding to that of the reference object compared to the reference potential. This is particularly useful for capacitive distance sensors with low excitation frequencies or objects to be detected with a low-impedance connection to the reference potential.

In addition, it is mentioned that both with a view to the capacitor and with a view to the electrical resistance, additional or other capacitive couplings or ohmic connections of the reference object are to be avoided or are to be compensated by the capacitance value of the capacitor or the resistance value of the electrical resistor. Furthermore, the values of the capacitor and those of the optional ohmic resistor should preferably be taken or derived from a standard. For example, reference is made to IEC/TR 61340-1 for the capacitive coupling of humans to earth potential.

In order to optimally adapt the test body to a reference object, it can also be provided that the permittivity (i.e. the dielectric conductivity) and/or the geometry and/or the projected geometry of the test body corresponds to that of the object to be detected. In the case of adapting the permittivity of the test body to the reference object to be checked, this enables a more precise function check, especially in the close range of the distance sensor.

In connection with the testing of protective devices, for example protective devices on robot arms, which are equipped with capacitive distance sensors, it is also provided in a further preferred embodiment of the test device that the test body is at least indirectly connected to a force sensor system for detecting forces acting on the test body is connected, the force profile of the determined forces preferably being detectable by means of an evaluation device. This is to check whether contact with the test specimen does not produce any critical forces or loads on the test specimen, which in a real case could, for example, damage objects or injure people or the like.

Alternatively or additionally, it can also be provided that the test body is at least indirectly connected to a pressure sensor system for detecting (mechanical) pressures acting on the test body, with the time course of the determined pressures preferably being detectable by means of a further evaluation device.

In particular, the force sensors and/or the pressure sensors serve, as already mentioned, to detect the forces or force peaks occurring, for example, in the case of limiting devices or a collision of a robot arm with an object or human being, in order to evaluate them with a view to limit values defined by guidelines and standards, for example .

In addition, it is very particularly preferred if at least the test body is arranged on a frame device that can be adjusted in and/or about at least one spatial axis and is preferably provided with distance measuring means. Such a frame device makes it possible to set an optimal spatial adjustment between the distance sensor to be checked and the test body and, in the event of a detection, to determine, for example, the distance between the distance sensor and the test body in a particularly simple manner.

In a preferred development of such a frame device, it is provided that the test body is connected to an adjustment drive, which can preferably be programmed with regard to its adjustment speed, in order to approach the distance sensor to be checked. This makes it possible, for example, to carry out automated operation or an automated check of a distance sensor, for example by approaching the test object to the distance sensor at a defined approach speed or within the framework of a standard and stopping the adjustment drive when the test object is detected by the distance sensor. With a view to a known stop value of the test object until it comes to a standstill, the distance between the test object and the distance sensor in the event of detection can be deduced.

• Zunächst erfolgt das Einstellen zumindest der Kapazität des Kondensators zwischen dem Prüfkörper und dem Referenzpotential entsprechend der Kapazität des zu detektierenden Objekts gegenüber dem Referenzpotential. Anschließend erfolgt ein Positionieren des Prüfkörpers zu dem Abstandssensor in einem Abstand außerhalb der Detektionsreichweite des Abstandssensors. Danach erfolgt eine Verringerung des Abstands zwischen dem Prüfkörper und dem Abstandssensor, bis der Prüfkörper durch den Abstandssensor erfasst wird oder aber ein sicherer Betriebszustand der mit der Schutzeinrichtung realisierten Sicherheitsfunktion erreicht wird, wie beispielsweise durch ein Roboterhalt. Zuletzt erfolgt die Erfassung bzw. Ermittlung des Abstands oder des Mindestdetektionsabstands zwischen dem Prüfkörper und dem Abstandssensor bei der Detektion des Prüfkörpers bzw. beim Erreichen des sicheren Betriebszustands. Dabei ist der systembedingte Nachlaufweg zu berücksichtigen.

Furthermore, the invention also includes a method for checking capacitive distance sensors or protective devices having capacitive distance sensors by means of a testing device according to the invention as described so far. The method includes at least the following steps:

• First, at least the capacitance of the capacitor between the test body and the reference potential is set according to the capacitance of the object to be detected compared to the reference potential. The test body is then positioned relative to the distance sensor at a distance outside the detection range of the distance sensor. The distance between the test body and the distance sensor is then reduced until the test body is detected by the distance sensor or a safe operating state of the safety function implemented with the protective device is achieved, such as by a robot stop. Finally, the distance or the minimum detection distance between the test body and the distance sensor is recorded or determined when the test body is detected or when the safe operating state is reached. The system-related overrun must be taken into account.

In addition, a method is preferred in which the reduction of the distance between the test body and the distance sensor and the detection of signals from the distance sensor are automated.

Further advantages, features and details of the invention result from the following description of preferred embodiments of the invention and from the drawings.

character list

• 1 until
• 3 show in schematic representations different test devices for checking capacitive distance sensors or protective devices having capacitive distance sensors,
• 4 a test device according to the 1 , which is arranged on a frame having distance measuring means, also in a schematic representation and
• 5 the test device according to 1 while performing a distance measurement with a distance sensor in a schematic representation.

Embodiments of the invention

Identical elements or elements with the same function are provided with the same reference numbers in the figures.

In the 1 is a testing device 10 for testing capacitive distance sensors 1 ( 5 ) or capacitive distance sensors 1 having protective devices, not shown, for example for preventing a collision between an industrial robot and objects or people, shown in a greatly simplified manner. The testing device 10 has a test body 12 which is fastened to a base body 14, for example. For example, a (mechanical) standardized interface 16 can be provided between the test body 12 and the base body 14 for fastening different test bodies 12 to the base body 14 .

The test body 12 is in the illustrated embodiment as perpendicular to the plane of the 1 running plate 17 is formed. The test body 12 can in particular be a test body 12 designed according to a standard, which is used to simulate a reference object (not shown). In particular, the test body 12 has a geometry that is not shown in detail, for example the geometry or the projection of a geometry of a hand, and consists of a defined material having mechanical or electrical properties. In order to ensure that the test body 12 has the same properties as the reference object, the test body 12 is connected to an (electrical) reference potential 22 via a capacitor 20 . The reference potential 22 can be, for example, a grounded or low-interference reference potential 22, or preferably the same potential that corresponds to the potential of the only in the 5 recognizable distance sensor 1 corresponds. What is essential here is that the capacitance or the capacitance value of the capacitor 20 corresponds to the capacitance of the reference object with respect to the reference potential 22 .

Provision can also optionally be made for the test body 12 to be connected to the reference potential 22 in parallel with the capacitor 20 via an electrical resistor 24 , the resistance value of the resistor 24 corresponding to the resistance of the reference object with respect to the reference potential 22 .

In the 2 is one opposite the 1 modified testing device 10a shown. On the side facing the distance sensor 1 (not shown), this has a spacer body 25 which consists, for example, of a solid foam material with a relative permittivity close to the value one. For detecting a minimum detection range a, the spacer body 25 has a thickness d corresponding to the minimum detection range a.

In the 3 a further modified testing device 10b is shown. The testing device 10b essentially corresponds to the testing device 10 without the electrical resistance 24. In addition, the testing device 10b has a pressure sensor system 26 on the side facing the distance sensor 1 for detecting (mechanical) pressures acting on the test body 12. The pressure sensor system 26 is preferably at least one pressure sensor 28 or a multiplicity of pressure sensors 28 designed in a manner known per se in order to determine a local detection of pressures on the test body 12 .

Furthermore, a force sensor system 30 in the form of at least one force sensor 32 is arranged in the area of the base body 14 . By means of the force sensor system 30, in particular axial forces F running perpendicular to the plane of the test body 12 and acting on the test body 12 can be detected. Furthermore, the pressure sensors 26 and the force sensors 30 are coupled to a first evaluation device 34 and a second evaluation device 36 which, in addition to detecting absolute values, also Enable detection of pressures or forces over time.

In the 4 A test arrangement 100 is shown, as is used in connection with the test device 10 by way of example. For this purpose, the testing device 10 is attached to a frame device 38 via its base body 14 . In addition, a measuring device 40 is arranged on the frame device 38 and is used to detect an axial displacement of the base body 14 and thus of the test body 12 in a direction running perpendicular to the plane of the test body 12 . Preferably, the frame device 38 or the base body 14 is also coupled to an adjustment drive 42, not shown in detail, which makes it possible to move the base body 14 and thus the test body 12 in relation to the distance sensor 1 to be checked in at least one axis x, y, z of a Cartesian coordinate system and, if necessary, to adjust the corresponding axis x, y, z of the Cartesian coordinate system. A control device 50, not shown in detail, is used for this purpose.

To detect a minimum distance b between an area to be protected 52, such as a robot arm, and the test body 12 according to 5 For example, the test body 12 can be moved in the direction of the arrow 53 to the distance sensor 1 by means of the test arrangement 100 until the distance sensor 1 detects the test body 12 . For this purpose, the distance sensor 1, the electromagnetic field 54 in the 5 is shown in a semicircle, coupled for example via a device 60 having a reference potential, the device 60 serving both to supply energy to the distance sensor 1 and to detect corresponding input variables of the distance sensor 1 when the test body 12 is detected. As soon as the test body 12 has been detected, the distance b at which the distance sensor 1 has detected the test body 12 can be determined, for example by means of the measuring device 40 on the frame device 38 .

Basically, the testing device 10, 10a and 10b is designed to validate both the detection of the test body 12 itself and the distance b and compliance with a minimum detection distance a of a distance sensor 1. By means of the pressure sensor system 26 and the force sensor system 30 in the case of the test device 10b, the test device 10b is also able to enable the validation of distance sensors 1 on protective devices, with the approach to the test body 12 to be detected and the area 52 to be protected, or in the event of contact, the residual risk, such as the kinetic effect between the area 52 and the test body 12, is evaluated.

To validate the detection of the test body 12, the test body 12 and the area to be at least monitored by the distance sensor 1 are spatially brought into overlap. The distance sensor 1 must now detect the test body 12 . In order to check the desired function of the distance sensor 1, the test body 12 and the area of the distance sensor 1 that is at least not to be monitored must be spatially aligned. The distance sensor 1 must not determine any detection of the test body 12 now. If the function is to be checked for the entire area of distance sensor 1 to be monitored, several positions of distance sensor 1 must be checked in the respective areas. If necessary, influencing parameters that influence the detection capability of the distance sensor 1 (for example humidity, electrical interference fields, etc.) must be taken into account empirically and analytically.

To validate the distance b of the test body 12 by the distance sensor 1, the test body 12 and the distance sensor 1 are brought closer to one another. The end of the approach can either be coupled automatically (with the shortest possible minimum stopping distance) to the triggering of a detection of the test body 12 by the distance sensor 1 . In the case of detection, the distance b can be measured using the measuring device 40 .

The test device 10a with the spacer body 25 is preferably used to validate a minimum detection distance a. In this case, the test body 12 together with the spacer 25 is brought closer to the area 52 to be protected or the distance sensor 1 until the area 52 and the spacer 25 touch. In this case, the distance sensor 1 must generate a corresponding signal about the detection of the test body 12.

In the case of protective devices that have distance sensors 1 for detecting the test body 12 or the reference body, a distinction must be made between non-contact and tactile protective devices. For the validation of a non-contact protective device, the test body 12 and the area 52 to be protected are brought closer together. For the validation of a machine to be safeguarded with any areas monitored by the distance sensors 1, such as a collaborative robot, the machine is preferably to be brought up to the test body 12 at the maximum speed v that can be expected. After reaching the safe state (for example an emergency stop of the robot), the minimum distance b between the area 52 to be protected and the test body 12 is to be measured. If the response time of the distance sensor 1 is monitored and corresponds to the longest case to be expected, and if all the parameters influencing the transition to the safe state correspond to the worst case, the safety of the system can be certified if the distance value is positive.

If the parameters do not correspond to the most unfavorable state or if the response time is not monitored, but if the relationship between the parameters and the time it takes for the system to transition to the safe state is known analytically or sufficiently empirically, the potentially necessary additional stopping distance can be calculated and with the minimum Distance b between the area to be protected and the specimen 12 are compared.

If the minimum distance b is greater than or equal to the potentially additionally required path, the security of the system can also be certified. If the relationships between the parameters and the duration of the transition to the safe state are not known, the approach of the test body 12 and the area 52 to be protected against contact can be repeated several times until a statistically significant probability of the safety of the system corresponding to the requirements of the system is reached system can be attested. For this purpose, for example, an analog calculation method according to ISO/TS 15066 and EN ISO 13855 Referenced Appendix D.

To validate a tactile protective device, based on a sensor system having distance sensors 1, in which the minimum distance between the area 52 to be protected and the test body 12 assumes the value zero, there is thus contact between the area 52 to be protected and the test body 12. Test device 10b can be used to evaluate this contact, for example when used to protect people from moving machine parts. As in the case of non-contact validation, the test body 12 and the area 52 to be protected are brought closer together. After the safe state has been reached (e.g. emergency stop), in the case of a tactile protective device, the pressure and/or force curves acting on the test body 12 determined by means of the pressure sensor system 26 or the force sensor system 30 are to be evaluated. If these are within specified limits, the security of the system can also be certified.

In addition, it is mentioned that the use of tactile protective devices with other residual hazards, such as an electrical hazard from voltages, a hazard from high temperatures or pollutants, etc., can also be used in an analogous manner for the validation. For this purpose, a corresponding sensor (ammeter, temperature sensor, pollutant sensor, etc.) is attached to the test body 12, which measures the residual risk when touched and thus makes it possible to assess it.

The testing devices 10, 10a and 10b described so far can be modified in many ways without departing from the spirit of the invention.

It is conceivable, for example, that for the validation of multi-channel systems, the testing devices 10, 10a and 10b are equipped with the possibility of logically ANDing the safety channels to trigger the transition to the safe state of the system to be tested.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102010064328 A1 [0002]
• DE 102016206480 B4 [0003]

Non-patent Literature Cited

• ISO/TS 15066 [0035]
• DIN EN ISO 13855 [0035]

Claims (12)

Testing device (10; 10a; 10b) for checking capacitive distance sensors (1) or protective devices having capacitive distance sensors (1), with a test body (12) for simulating a reference object, the test body (12) being connected via at least one capacitor (20). a reference potential (22) is coupled, the capacitance of the at least one capacitor (20) corresponding to the capacitance of the reference object with respect to the reference potential (22). test device claim 1 , characterized in that the reference potential (22) corresponds to a reference potential (22) of the distance sensor (1) to be tested or of the protective device to be tested. test device claim 1 or 2 , characterized in that at least one electrical resistor (24) connecting the test body (12) to the reference potential (22) is provided parallel to the capacitor (20), the resistance value of the at least one resistor (24) being that of the reference object compared to the reference potential ( 22) corresponds. Test device according to one of Claims 1 until 3 , characterized in that the permittivity and / or the geometry and / or the projected geometry of the test body (12) corresponds to that of the reference object. Test device according to one of Claims 1 until 4 , characterized in that the test body (12) is at least indirectly connected to a force sensor system (30) for detecting forces (F) acting on the test body (12), the time profile of the determined forces (F) preferably being recorded by means of an evaluation device (36 ) is detectable. Test device according to one of Claims 1 until 5 , characterized in that the test body (12) is at least indirectly connected to a pressure sensor system (26) for detecting mechanical pressures acting on the test body (26), the time profile of the determined pressures preferably being able to be detected by means of a further evaluation device (34). Test device according to one of Claims 1 until 6 , characterized in that at least the test body (12) is arranged on a frame device (38) which can be adjusted in and/or about at least one spatial axis (x, y, z) of a Cartesian coordinate system and is preferably provided with distance measuring means (40). test device claim 7 , characterized in that the test body (12) is connected to an adjustment drive (42), which is preferably programmable with regard to its adjustment speed, for approaching the distance sensor (1) to be checked. Test device according to one of Claims 1 until 8th , characterized in that at least one further sensor for detecting a hazard is arranged on the test body (12). Test device according to one of Claims 1 until 9 , characterized in that a spacer (25) with a thickness (d) is arranged on the test body (12) which corresponds to a minimum detection range (a) of the distance sensor (1), the material of the spacer (25) preferably having a relative permittivity has a value close to one. Method for checking capacitive distance sensors (1) or capacitive distance sensors (1) having protective devices by means of a test device (10; 10a; 10b) according to one of Claims 1 until 10 is designed, comprising at least the following steps: - setting at least the capacitance of the capacitor (20) between the test body (12) and the reference potential (22) according to the capacitance of the reference object compared to the reference potential (22) - positioning the test body (12) to the Distance sensor (1) at a distance outside the detection range of the distance sensor (1) - reducing the distance between the test body (12) and the distance sensor (1) until the test body (12) is detected by the distance sensor (1) or until it is reached a safe operating state of the safety function implemented with the protective device - recording the distance (b) or a minimum detection distance (a) between the test object (12) and the distance sensor (1) when the test object (12) is detected or when the safe operating state is reached safety function implemented with the protective device procedure after claim 11 , characterized in that the reduction of the distance between the test body (12) and the distance sensor (1) and the detection of signals from the distance sensor (1) takes place automatically.

Images