RU2080647C1 - Method for automatic functional diagnostics of controlled equipment which is checked at regular intervals - Google Patents

Abstract

FIELD: automatic control systems which monitors discrete states of objects to be controlled. SUBSTANCE: method involves detection of operating conditions and wear level of controlled equipment which is checked at regular intervals by means of automatic monitoring of wear alternation in equipment during its service life. Method is coincided with control actions on equipment and requires measurement of time interval between sending a control action for state transition and receiving a response that equipment is in required state. Difference between this interval and interval which was detected during last control action is used for decision about fault conditions of this equipment; difference between this interval and interval which was detected during first control action on new equipment is used for judging wear conditions of equipment. This results in possibility to detect fault conditions which are caused by premature wear and developing fault in equipment. EFFECT: detection of developing fault conditions, possibility to check equipment simultaneously with normal control operations without need for special test actions.

Description

 The invention relates to automated process control systems (ACS TP) that implements the functions of automatic control of discrete states of technological equipment.

 Technological equipment with discrete states means devices with movement of the regulatory body (taps, valves, gate valves, gates, valves, etc.), aggregate type equipment (pumps, fans, smoke exhausters, etc.) and other technological equipment translated by filing control actions from one discrete state (or operating mode) to another.

 In existing automatic control systems, for monitoring the operability of discrete actuators and units with discrete states, the control execution time is used. For example, in [1], the control response time of the taps was taken to be 60 s, and the start and exit to the pump mode were 30 s.

 The disadvantages of this method are the need for preliminary expert evaluation of the control response time, usually with one and a half to twofold margin, and the lack of an individual approach to each specific instance of a discrete actuator or unit with discrete states.

A known method of removing transient characteristics used to diagnose hydraulic drives of construction vehicles. The method is based on the analysis of the response of the hydraulic system to instantaneous pressure changes in it [2, p. 531]
The disadvantages of this method are the need for a test effect on the object and the use of additional overhead or built-in sensors for continuous removal and recording the response of the object to the disturbance.

 Closest to the proposed technical solution is the method implemented in the technical means of bench diagnostics of construction machines for measuring the braking time of cranes' brakes: the time interval between the start of braking when the speed of the brake pulley corresponds to the rated speed and the end of braking when the speed of rotation of the brake pulley is close to zero [2, p. 547] As a speed sensor, a direct current tachogenerator is used, the shaft of which is connected through a contact roller during diagnosis with a brake pulley. The moment of the beginning of braking, as well as in the electromechanical counter of the braking distance [2, p. 546] is fixed by relieving stress from the brake electromagnet or electrohydro pusher.

 The disadvantage of this method is the need for special bench equipment for test diagnosis of the object.

 The purpose of the invention is operational functional (working) diagnostics of serviceability and wear rate of periodically controlled technological equipment having discrete states.

 This goal is achieved by automatically controlling the wear curve of such process equipment during its service life. The control is combined with each control action on the given technological equipment and is conducted according to the time interval between the moment the control action is applied to the state change and the moment the technological equipment arrives at the required discrete state. By the degree of deviation of this time interval from the time interval determined during the previous control action, the pre-failure of the technological equipment is judged, and by the deviation from the time interval determined during the very first control action on still new worn-out technological equipment, the degree of wear of this equipment is judged.

 The proposed method allows timely detection of pre-emergency situations associated with premature deterioration and brewing failure of periodically controlled technological equipment having discrete states. In this case, the diagnostics are combined with the process of working control and do not require the exclusion of equipment from the technology for special test tests.

To implement the proposed method, for example, in industrial control systems with respect to discrete actuators (DIM). The following operations are performed:
at each working control action on the DIM, the time interval between the moment the control action is applied to the state change and the moment the DIM arrives at the required discrete state is automatically controlled (by position, state, or indirect indicators);
during the service life of a periodically controlled DIM, automatic accounting of the initial, previous and current DIM response time intervals (transition of DIM from one discrete state to another) is kept;
when the current interval of the DIM response time deviates from the previous one over the allowable limits, the emergency condition of this DIM instance is automatically signaled;
during normal operation of a DIM, the degree of its deterioration is estimated by the deviation of the current interval of the DIM operation time from the time interval determined during the very first control action on a still new unworn DIM.

 The permissible deviation limits of the current DIM response time interval from the previous such interval are either rigidly set or automatically adjusted as a result of mathematical processing of statistical data on the indicated deviations, which are received during the whole life of the DIM.

 The fundamental possibility of implementing the proposed method is confirmed by data on the reliability and diagnosis of technical objects.

In all technical objects, irreversible random measurements of the determining parameters are observed during wear, aging or deregulation [3, p. 66] Any sudden failure is preceded by the accumulation of certain changes within the technical object (wear of parts, aging of materials, deregulation) [4, p. 12] Over time, the failure rate of technical objects increases due to their wear [4, p. 245] The rate of change of the defining parameters of a technical object decreases or increases exponentially with the course of operating time and tends to a stationary value [4, p. 265]
To date, gigantic experimental material has been accumulated on the forms of wear curves. Typical wear curve [4, p. 232] consists of three sections: the initial period of running-in of elements to specific operating conditions (the defining parameter of the object decreases gradually), the main period of the element (the defining parameter of the object is approximately constant) and the period of "aging" of the element (the rate of change of the parameter dramatically increases).

The practical measurability of modern software and hardware of an automated process control system of the time it takes for executive teams (MI) to execute control commands is not in doubt when they become acquainted with their dynamic characteristics [5, p. 716-788]
So, the nominal time of the full stroke of the output shaft of single-turn electromagnetically MI type MEO and MEO-K is from 10 to 160 s, depending on version. And the nominal full-stroke time of the output shaft of multi-turn electric IM type MEM is from 25 to 400 s. Linear electric IM type MEP have a nominal full-stroke time of the rod from 10 to 160 s.

 Valves, rotary, shut-off and shut-off valves, control and mixing valves, valves of industrial pipe fittings with electric control, in particular shut-off valves of type 22s934r, have an opening time of up to 40 s and a closing time of up to 1 s.

 Pneumatic and electro-pneumatic actuators and fittings with a pneumatic actuator, in particular piston straight-through pneumatic cylinders, with a piston stroke of up to 60-400 mm and a rod speed of not more than 0.5-1 m / s have a full stroke time of about 0.06-0.8 s, and electropneumatic IM type MPP-125-DKE up to 8 s.

 The time variation is performed by the MI of the control command submitted to it also actually exists during operation and can be caused by the following reasons.

 In single-turn electric IMs like MEO and MEO-K, it is possible to brake the output shaft with a load [5, p. 716-788] and on valves, even switches are installed that give a discrete signal when the torque or force exceeded on the output organ. To communicate with the position signaling unit, some MI designs contain an auxiliary gearbox, the gears of which can also seize and fail.

The following types of failures are characteristic of the electrical part of the MI control: failure (break) in the presence of a control signal; operation (short circuit) in the absence of a control signal; maintaining a closed state when removing the control signal ("welding" of contacts); spontaneous open circuit in the presence of a control command and the initial correct operation [6, p. one hundred]
MI failures can be associated with stem jamming, clogging, valve failure, failure of the motor or limit switches [6, p. 119]
A study of the reliability of electrical controls in operating conditions in various industries shows the following main types of failures: sticking, burning or skewing of contacts of magnetic starters, burning or open windings, short circuits, damage to mechanical elements, jamming or breakage of gears of gearboxes, breakage or misalignment of limit switches , violation of contacts in the limit switch or position sensors, “jamming” (tight running) of the regulatory body [6, p. 211-212]
Information sources:
1. Management of executive mechanisms. Description of the problem statement of Tsa. 17705.029 ЗВ2 (Techno-working project "Automated process control system for gas treatment facilities of Karachaganak NGKM")

 Krasnodar. SPKB Promavtomatika, 1988.

 2. Technical means of diagnosis. Reference book / Klyuev V.V. Parkhomenko P.P. Abramchuk V.E. and others under the general. ed. V.V. Klyueva. M. Engineering, 1989.

 3. Glazunov L.P. Smirnov A.N. Design of technical diagnostic systems. L. Energoatomizdat. Leningrad Department, 1982.

 4. Druzhinin G.V. Reliability of automated production systems.

 4th ed. reslave. and add. M. Energoatomizdat, 1986.

 5. Industrial devices and automation equipment, Reference / Baranov V. Ya. Beznovskaya T.Kh. Beck V.A. and others under the general. ed. V.V. Cherenkov. L. Engineering, Leningrad. Department, 1987.

 6. Yastrebenetsky M.A. Ivanova G.M. Reliability of automated process control systems: Textbook. Manual for universities. M. Energoatomizdat, 1989.

Claims (1)

 A method for automatic functional diagnostics of periodically controlled technological equipment having discrete states by determining the time interval between the moment the control action is applied to the state change and the moment the technological equipment arrives at the required discrete state, characterized in that the determination of the specified time interval is combined with each control action on the technological equipment and the degree of deviation of this time interval from the interval la of time determined in the previous control actions judged preemergencies process equipment, and the deviation from the time interval defined by the first control action on the process equipment, judge the degree of wear of the equipment.