DE102019219521B4 - Foam sensor and method of operating a machine - Google Patents

Abstract

Foam sensor (30) that can be cut into a predetermined shape, the foam sensor (30) comprising a plurality of light sources (32) and light sensors (33), characterized in that the light sources (32) and the light sensors (33) with fan-shaped electrical leads which meet at an exit point (36), characterized in that the foam sensor (30) comprises a blanking area (34).

Description

The present invention relates to a method for operating a machine, a method for manufacturing a machine and a foam sensor.

State of the art

From the DE 698 08 293 T2 a pressure sensor is known which comprises a foam material, a light source and a light sensor. The foam material includes scattering centers and conducts light fed in by the light source located in it, so that the light sensor also located in the foam material can receive the light introduced. The sensor is arranged in such a way that it cannot receive the light from the light source directly, but receives the light after it has been scattered by the foam material. When the foam material deforms, its light conductivity or the density of the scattering centers changes, so that an evaluation of the light intensity received by the light sensor represents a measure of the pressure acting on the foam material. A pressure sensor can thus be formed from the foam material.

From the EP 1 605 240 A1 a textile sensor is known which is formed from a flat, woven electrode and opposite electrodes formed by conductive threads. The flat electrode and the conductive threads are separated by a non-conductive layer and each form a capacitor. The distance changes when pressure is applied, so that the capacitance of the capacitors also changes as a result. The change in capacitance can be measured to give a measure of the pressure applied.

Contact switches are known from the prior art, which are mounted on moving parts of machines in order to switch off the machine for safety reasons when the moving parts come into contact with a foreign object. The contact switches are permanently mounted and often have to be installed inside the machine, for example to detect the deformation of a moving part of the machine. In addition, contact switches are not suitable for classifying the type of contact between the machine and a foreign object.

From the DE 44 28 650 A1 an optical pressure detection device based on an optical waveguide in a mat is known.

From the DE 10 2010 010 873 A1 a flexible safety mat for collision detection is known, the mat having a compressible layer and a pressure-sensitive layer underneath.

From the DE 10 2009 055 121 A1 is a sensing surface element that includes several capacitive sensors.

From the DE 10 2009 029 021 A1 a sensor system for monitoring the surroundings of a mechanical component based on capacitive sensors is known.

From the DE 10 2007 022 871 A1 a tactile sensor with decoupled sensor cells is known, the sensor cells changing their electrical resistance under pressure.

Disclosure of Invention

The method according to the invention for operating a machine, in which part of the machine is covered with a flat foam sensor according to the invention, which is set up to detect pressure, has the advantage that an emergency response is initiated if the foam sensor makes contact between the machine and a foreign object is detected.

It is advantageous that the emergency response is only initiated when the foam sensor detects that the contact between the machine and the foreign object is exerting pressure on the foam sensor that exceeds a threshold pressure. In this way, relevant and irrelevant touches between the machine and the foreign object can be distinguished. For example, if the machine is a rather robust machine, it is not necessary to initiate an emergency response if it is detected that the pressure acting on the foam sensor corresponds to a pressure equivalent to contact with a light object lying around in a machine room, such as a packaging material. The threshold pressure can be applied depending on the design of the machine and foreign objects typically found at its place of use.

It is advantageous that the emergency response is only initiated if the foam sensor detects a two-dimensional pressure distribution on the foam sensor and the detected two-dimensional pressure distribution corresponds to a stored pattern. The stored pattern can in particular be a pattern that typically occurs as a result of the foam sensor coming into contact with parts of a human body, such as a foot. Thus, advantageously safety-relevant collisions of not safe safety-relevant collisions are distinguished, which avoids unnecessary emergency responses.

The method according to the invention for producing a machine has the advantage that a shape of a contact part of the machine is determined, that the shape of a foam sensor according to the invention is derived from the shape of the contact part, and that a foam sensor according to the invention with the derived shape is attached to the contact part of the machine will.

In other words, the machine is initially completed except for the foam sensors that are still missing. It is then checked which surfaces on moving parts of the machine are more likely to come into contact with a foreign object. The surfaces identified in this way can in particular also be external surfaces of a machine that is movable overall, for example a self-propelled robot. The foam sensors are then cut out with a precise fit and attached to the previously identified areas of the machine. A moving machine can thus be secured in a simple and cost-effective manner.

The foam sensor according to the invention has the advantage that it can be cut into a predetermined shape. For this purpose, the foam sensor is prefabricated in the form of a mat, with lines inside the foam sensor, which are available, for example, for supplying light sources or for transmitting signals from light sensors, are arranged in a fan shape inside the foam sensor and meet at a common exit point on the edge of the foam sensor. The foam sensor can be cut to any size while leaving out the exit point, regardless of whether some leads from light sources or light sensors are cut off. For the function of the foam sensor it is only necessary to ensure that not all light sources or all light sensors are cut off. In this way, sensor strips of almost any shape can be produced from the foam sensor.

The foam sensor can be a foam sensor known from the prior art, or one of the foam sensors described in more detail below.

The foam sensor can advantageously comprise a foam element, light sources and light sensors being located within the foam element, so that the light sensors receive light emitted by the light sources, the foam element being designed in such a way that the light intensity received by the light sensors changes as a function of a light acting on the foam element Pressure changes, wherein the foam sensor also comprises electrodes forming a capacitor whose capacity is dependent on the pressure acting on the foam element.

The foam element includes scattering centers, but is otherwise light-conducting. Light coupled into the foam element is scattered at the scattering centers, so that the light sensors located in the foam element receive the light scattered by the scattering centers. When the foam element is compressed as a result of pressure, the local density of the scattering centers in the area of the pressure is increased, so that the light sensors detect an increased light intensity. The light intensity is a clear measure of the intensity of the pressure effect. In addition, the foam sensor can include electrodes that form a capacitor. The capacitor is also compressible, for example due to the use of the compressible foam material as an insulating layer, so that the capacitance of the capacitor changes when local pressure is applied. A measurement of the capacitance of the capacitor therefore provides a clear measure of the pressure acting on the capacitor, so that this embodiment of the foam sensor advantageously enables two independent measurement methods that can be used to detect a pressure redundantly. This is particularly advantageous in applications in which the foam sensor cannot be replaced or serviced over a long product service life, since the two independent measurement methods can also be used to detect long-term sensor drift and to compensate for it as part of an electronic evaluation. This configuration of the foam sensor thus offers a cost-effective, flexible and long-lasting option for measuring pressure.

An electrode of the sensor system is advantageously formed by a flat fabric, which can be formed, for example, from a multiplicity of electrically conductive wires or fibers that are woven together. Alternatively, the flat fabric can also contain non-electrically conductive components, such as commercially available textile fibers. A mechanical or haptic property of the planar fabric can thus advantageously be provided in a desired manner.

It is advantageous if the foam element has a surface, with an electrode being located on the surface of the foam element de. In a particularly advantageous embodiment, the electrode that forms the flat fabric is located on the surface of the foam element. A desired surface property or surface feel can thus be provided. In a further advantageous embodiment, at least one second electrode is located within the foam element.

In a further advantageous embodiment, in which the foam element has two opposite surfaces, the electrodes are located on the two opposite surfaces of the foam element. It is particularly advantageous if both surfaces are covered by electrodes that form flat tissue.

It is advantageous if the electrodes form an electrical line that is connected to the light sources or the light sensors. By using the electrodes as electrical lines, a foam sensor can advantageously be implemented that does not require any separate electrical lines to supply the light sources with electrical energy or to transmit electrical signals provided by the light sensors. In other words, a foam sensor can thus advantageously be provided whose signal lines or supply lines can be used to implement capacitive pressure sensors.

The foam element advantageously forms a mat. The foam sensor comprises a plurality of light sensors, so that a localization of the pressure acting on the foam element can be determined from a distribution of the light intensity received by the light sensors. The mat shape of the foam element offers the advantage that the foam sensor formed in this way can be used flexibly. Thus, the pressure can not only be measured in terms of amount, but also assigned spatially. By appropriately arranging the light sensors, a foam sensor can be provided with a spatial resolution that enables an area affected by the pressure or a two-dimensional pressure distribution to be determined. The foam sensor can also include a plurality of electrodes.

An embodiment of the foam sensor is described in more detail in the following drawings. show:

character list

• 1 a schematic cross section through an exemplary foam sensor;
• 2 a schematic plan view of an exemplary foam sensor;
• 3 a schematic representation of a foam sensor that is suitable for a blank.

1 shows a schematic cross section through a foam sensor (10). A foam element (11) is approximately cuboid, so that the foam sensor (10) forms a mat overall. The foam element (11) is light-conducting and includes scattering centers. On the upper side of the foam element (11) there is a flat fabric (12), which consists at least partially of electrically conductive material and therefore forms an electrode. The flat fabric (12) is thin compared to the thickness of the foam element (11).

The foam sensor (10) comprises a number of light sources (14), which can be, for example, LEDs, and a number of light sensors (16), such as photocells. The light sources (14) and the light sensors (16) are embedded in the foam element (11) and arranged in such a way that the light intensity received by the light sensors (16) has a significant proportion of scattered light that was scattered at the scattering centers. The light sources (14) and the light sensors (16) are each connected to electrical lines (17), the electrical lines (17) being both lines for the voltage supply and signal lines. Advantageously, signals from the light sensors (16) can be transmitted as digital signals via the electrical lines (17). The electrical lines (17), together with the flat fabric (12), each form a compressible capacitor whose capacitance depends on the pressure exerted on the foam element (11). The capacitance of the capacitors can be measured by means of evaluation electronics and the effect of pressure can be determined from this.

2 shows a schematic plan view of the foam sensor (10), the already in the context of the description of 1 elements explained are not described again. The foam sensor (10) can include a further sensor (18), which can be an acceleration sensor, a temperature sensor and/or a humidity sensor.

3 shows a schematic representation of a mat-shaped foam sensor (30) which is suitable for a blank. The foam sensor (30) is essentially as in connection with 1 and 2 described constructed and can optionally include electrodes. The light sources (32) and the light sensors (33) are arranged within the foam sensor (30) in such a way that they form a matrix structure, the electrical lines running from the light sources (32) and light sensors (33) in a fan shape to an outlet point (36). At the outlet point (36), the electrical lines can leave the foam sensor (30) and be connected to readout electronics. The arrangement of the light sources (32) and the light sensors (33) as a matrix and the fan-shaped arrangement of the electrical lines allow the foam sensor (30) to be cut to size without essentially damaging its effect. The foam sensor (30) can be cut to almost any size in a cutting area (34) without all the light sources (32) or light sensors (33) being cut off in the process. The functionality of the foam sensor (30) is thus guaranteed even after a cut.

Claims (6)

Foam sensor (30) that can be cut into a predetermined shape, the foam sensor (30) comprising a plurality of light sources (32) and light sensors (33), characterized in that the light sources (32) and the light sensors (33) with fan-shaped electrical leads which meet at an exit point (36), characterized in that the foam sensor (30) comprises a blanking area (34). A method for manufacturing a machine, characterized in that a shape of a contact part of the machine is determined in that the shape of a foam sensor (30) is calculated from the shape of the contact part claim 1 (30) is derived and that a foam sensor (30) after claim 1 with the derived shape is attached to the contact part of the machine. A method for operating a machine, a part of the machine having a flat foam sensor (30). claim 1 , which is arranged to detect pressure, is covered, characterized in that an emergency response is initiated if contact between the machine and a foreign object is detected by means of the foam sensor (10, 30). procedure after claim 3 , characterized in that the emergency response is only initiated if the foam sensor (10, 30) detects that the contact between the machine and the foreign object exerts a pressure on the foam sensor that exceeds a threshold pressure. Procedure according to one of claims 3 or 4 , characterized in that the emergency response is only initiated if the foam sensor (10, 30) detects a two-dimensional pressure distribution on the foam sensor and the detected two-dimensional pressure distribution corresponds to a stored pattern. Procedure according to one of claims 3 until 5 , characterized in that the emergency response comprises an emergency stop of the machine.

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