How we made the neuron stare at the damage to the steel cable. Part 1


AND

Application interface

We were inspired by the guys from PHYGITALISM and their article “How we made a neuron stare at rust”, and the topic was thrown by the customer. We are a company Alter Ego and specializes in the intersection of machine vision technologies, simulation and data mining for indestructible inspection tasks. The task was set – the detection of steel cables (by the way, the term “ropes” is more often used) of civil elevators for damage. The pitfalls were not long in coming – it turns out that there is no type of damage or their classification (so where does such wealth come from – with them the elevator “will not be released into the raid”). To our sorrowful sighs that there was nothing to train neurons on, they gave the document RD ROSEK 012-97 “Steel ropes, control and culling standards” and, judging by the face of the chief technologist, mentally crossed themselves.

In the above document, the damages were listed and their detailed description, black and white, was given. Here it is:

Rice.  1 Fragment of the description of one cable damage (breakage of the wires of the cross-lay rope)

Rice. 1 Fragment of the description of one cable damage (breakage of the wires of the cross-lay rope)

Realizing that neurons cannot be trained in this way, they decided to simulate damage in Unity on three GOST cables, but realizing that the customer would not wait, and they made a neural expert network as a stub, later, when they typed another dataset with grief in half, based on Yolo 3, about all our plans (in the end, everything worked out as planned) – in the following publications.

So let’s force it. Elevators are technical objects of increased danger, one of the main structural elements of which is a cable-block system. The safety of elevator operation is largely determined by the technical condition of the ropes, although the term “cable” is more often used. Steel cables in elevators are used as traction and balancing elements, as well as to actuate the elevator’s speed limiter.

The choice of steel cables of elevator systems, control and culling are carried out in accordance with the requirements of a number of regulatory documents. The need to control the technical condition of the cables is due to the results of their numerous tests carried out both in laboratory and in production conditions. Of the more than 8,000 ropes that were replaced, about 10% had a loss of strength of more than 15%, about 2% of the ropes lost more than 30% of their nominal strength. On the other hand, more than 70% of the ropes taken out of service had minor defects and could still be used.

The latest figures indicate that if there was a smart video analytics system, then the cables would still hang.

The safety rules define the criteria and norms for rejecting ropes due to surface and internal abrasive wear, corrosion, the number of breaks in the outer and inner wires along the length of the rope lay pitch. In addition to quantitative criteria for rope rejection, qualitative ones should also be taken into account: deformations of various types, damage as a result of temperature exposure or electric arc discharge. So, by the way, the main reason for the breakage of the traction ropes and the rope of the speed limiter of the Ostankino tower elevator during the fire on August 27, 2000 was the effect of high temperature.

The structure of the cable includes the following components: core, strand, wire, center wire, which is shown in Figure 2. Most often, each individual wire is located around the center wire, forming a core of wire.

The strands are formed around a central core to form a rope. Depending on the number of strands, the thickness of the cables is determined, there are quite a lot of them, but there is a limit on the number of threads – 25. The size and number of wires in each strand, as well as the size and number of strands in the rope, greatly affect the characteristics of the rope.

Rice.  2 Steel cable device

Rice. 2 Steel cable device

Steel cables made according to:

  • GOST 2688-80 with linear touch wires. The product uses an organic core, which gives it flexibility and fracture strength. Also, the acquisition of these properties is facilitated by the different thickness of the wires in the outer layer of the strands;

  • GOST 3077-80 – a product with a double weave and a linear touch of the wires. With a sufficient diameter, it is actively used in the assembly and repair of elevators, lifts, suspended cradles. Differs in good flexibility, wear resistance, ability to work in an aggressive environment;

  • GOST 7665-80 also has a double lay and an organic core. High flexibility and strength make the product suitable for elevators in the absence of aggressive environments.

There was no classification at all, they made their own:

  • corrosive changes;

  • violation of the external geometry (external contour) of the cable;

  • violation of the internal geometry (internal contour or lay) of the cable.

Corrosive type damage in terms of detection by image analysis is primarily a change in the color of the cable and the area of ​​this change. Depending on the type of chamber, it is possible to detect both the initial stage of corrosion with a small area of ​​damage (the spot is limited to one lay step), and significant ones, as in Figure 3.

Rice.  3 Significant corrosion changes

Rice. 3 Significant corrosion changes

Violation of external geometry refers to several types of damage at once:

  • breakage of wires of the outer lay;

  • loop-like exit of the lay wires in one or more strands;

  • bilateral reduction or increase in the diameter of the cable;

  • unilateral reduction or increase in the diameter of the cable;

  • waviness of the cable;

  • a crease (kink) of the cable;

  • extruding a strand of the outer lay;

  • extrusion of the core;

  • rope twisting.

All of the above damages are detected by calculating the area of ​​the rope projection standard (standards are of two types: a small standard containing 5 lay strands and a large one containing 8 strands) and the percentage deviation from the standards. Figure 3 shows damage – extrusion of a strand of the outer lay.

Rice.  4 Rope damage type "catching strands of the outer lay"

Rice. 4 Damage to the rope of the type “catching strands of the outer lay”

Under the violation of the internal geometry (not to be confused with internal damage that occurs inside the rope) of the cable, the following types of damage are meant:

  • uneven gap between the strands;

  • twist of the strand;

  • strand break;

  • lack of strand;

  • extrusion of wire from a strand;

  • extrusion of strands of the core;

  • wire break (effect “Burunda”);

  • extrusion of strands of the outer lay.

It is worth noting that a number of damages can be classified as two types of damage, depending on the fact of fixing the image – if a wire break in the image does not violate the external boundaries of the image (rope projection in this image), then the damage is classified as internal damage, if a break or other damage fixed on the border of the image is external. Internal damages are fixed due to the formation of a cable lay projection standard, deviations from the areas and “guides” of the standard.

Below (Fig. 5) shows an example of damage detection – deviation (increase / excess) of the area from a small projection standard, which allows us to speak of a loop-like multiple exit of strands. Also, there is a calculation not only by area, but also as a percentage of the height of the triangle described over the damage to the rope section. The manufacturers themselves, as well as those who operate steel ropes, mainly use only the loss in diameter as a percentage of its value and the breakage of the outer wires also as a percentage of the diameter of the rope.

Rice.  5 Rope damage areal deviation analysis example

Rice. 5 Rope damage areal deviation analysis example

It is worth noting that today the methods of checking steel ropes are either visual or magnetic flaw detection, although the capabilities of machine vision technology are sometimes not inferior, but in logic – 24/7 and surpass them. There are point practices for the implementation of machine vision detection tasks for both civilian elevators and other lifting mechanisms where there are steel cables. We sincerely believe and do what we can to create and implement such systems not just pointwise, but as a well-established practice for the tasks of indestructible control in production, and not only.

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *