Introduction. Increased attention is paid to safety issues during the operation of elevator equipment1, 2, 3. About 500 thousand passenger, hospital and freight elevators are being used in the Russian Federation. According to the statistics of elevator accidents, their prime causes are insufficient quality of elevators and components, as well as improper maintenance and repair.

Analysis of elevator accidents has shown that about 30 % of incidents are directly or indirectly related to the technical condition of the ropes [1]. Extremely dangerous are defects, whose growth causes elevator car fall. Passenger elevator accidents, especially tragedies with victims, are very resonant events. Administrative4 and criminal5 liability is provided for violation of safety requirements during operation of elevators.

Timely and high-quality control of the technical condition of steel ropes provides preventing dangerous incidents [2–5].

Damage to the ropes occurs due to their poor quality and errors during installation. The consequence of incorrectly performed work may be unacceptable interaction with elements of the elevator equipment, including electrical ones.

Steel ropes can be considered an indicator of the technical condition of elevator equipment. Their defects signal the pulley groove wear, rope slip on a pulley (including due to excessive lubrication), skewed winch mounts, backlash in the elements of the drive gears, etc. Possible malfunctions of the elements of the mechanical part of the elevator, depending on the defective parameters of the ropes, are presented in Table 1.

There is a significant difference in the rejection indicators and the standards for the rejection of ropes of various lifting structures6, 7 and elevators. In the latter case, the criteria are included in the operating manual of the specific elevator. This approach reduces the number of defect indicators, which, specifically, does not contribute to improving operational safety. In [1], the criteria and norms of rejection are given.

Materials and Methods. Ropes are products of deep processing of steel. If their safety margin is reduced to a critical value, operation is unacceptable.

The control of ropes of lifting structures by magnaflux method is widely known. It is used in the diagnosis of passenger cable cars, cargo cranes, lifters. This approach makes it possible to recognize internal defects invisible to the eye, measure the loss of the cross-sectional area of the rope, and detect local inconsistencies. As a rule, the method is used to control steel ropes with a diameter of more than 20 mm.

The average service life of elevator ropes is regulated and does not exceed five years. During this time, loading cycles do not cause loss of cross-sectional area and fatigue damage to the wires of the inner layers. For this reason, magnetic flaw detection is not used for elevator installations.

The most common method of assessing the technical condition of elevator ropes is visual inspection control (VIC)8. It provides assessing the technical condition of the operated elevator ropes, which are evaluated according to the following standards of rejection:

Here, t — current operating time of the elevator.

The rejection rate is understood as the value of Pi(t):

Pi(t) = Pio + Pi'(t). (1)

Here, Pio — scleronomous part, it does not depend on t and is associated with a single application of loads; Pi'(t) — rheonomic part, which accumulates in the process of elastoplastic cyclic deformation.

When assessing the technical condition of the rope during operation, the loss of its strength is calculated according to at least one of the rejection criteria:

Pi(t) ≤ [Pi], (2)

where i = 1/12.

Under the maintenance of passenger elevators, VIC of steel ropes is performed at intervals specified in the operations manual (as a rule, once a month).

VIC of steel ropes consists of two stages:

The quality of VIC under maintenance of steel ropes is associated with the physiological capabilities of human visual perception [4–6]. The elevator can have from three to twelve parallel ropes with a complex balancing system. The quantity depends on the height and load capacity. Health assessment of ropes, balancing units and sealing off involves working at height, under difficult conditions, in tight working space, in low light9. The possibilities of human vision are limited. It is known that after watching a moving steel rope for more than ten minutes, the eyes get tired and perceive the numerous rejection indicators worse. High-quality, objective control of elevator ropes requires automation of the process. Analysis of literature sources, accidents and incidents, has shown that it is reasonable to use solutions based on computer vision and artificial intelligence technologies for automation [5–10].

The authors set a goal to create a program apparatus complex (PAC) of VIC for the practical implementation of visual and measurement control based on computer vision and artificial intelligence technologies10.

Research Results. In elevators, defects in steel ropes and their attachments are automatically detected and identified using special means of photo and video recording. Machine vision and artificial intelligence process images of defects. An integral assessment of the types and parameters of the detected defects in the form of a color indication is transmitted to the mobile device. PAC VIC automates and combines two control methods: visual and instrumental.

The basic functions of the PAC VIC are listed below.

The complex consists of three elements.

Six IP cameras with a resolution of 640.480 are used to photograph sections of movable steel ropes. They are fixed in the housing installed in the elevator shaft. The number of cameras depends on the number of ropes on which the elevator car is suspended. The cameras are connected via a wired or wireless communication channel to a single-board computer that processes images and generates a batch message for forwarding to the server. A single-board computer generates a batch message. It is transmitted via an Ethernet cable or a wireless communication channel through a modem router to the server. The latter classifies defects, determines their number and metrological parameters, outputs an integral assessment of the technical condition of the rope, interprets it as a color indicator, and in this form transmits it to the user through a mobile application.

Figures 1–3 shows the PAC VIC modules for elevator installations, the functional diagram and the hardware component of the complex.