RU2701674C1 - Control method of electric drive of excavator bucket opening - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to electrical engineering and is intended for use on quarry excavators to improve the reliability of the excavator bucket opening mechanism when loading rock. In electric DC drive by means of setting device 17 angular speed setting equal to rated angular speed of electric motor is always set. In the initial moment of the drive operation, a restriction corresponding to the cable pulling current is installed in the controlled limitation unit 11. When control button 7 in unit 11 is switched on, maximum current limitation value is set. As a result, current and electromagnetic motor torque proportional to it increase sharply. This results in withdrawal of retainer 23 and opening of bottom 22 of bucket 24 of excavator. Current of armature winding 16 is increased up to value exceeding moment of resistance of mechanism holding retainer 23. Sharp reduction of load and, hence, current of electric motor is performed after pulling of retainer 23. Bottom 22 of ladle 24 opens under action of content and rock is unloaded. At that, electric drive only winds cable 20 on drum 19 at low load. When the current reaches the threshold level specified by threshold element 2, a constraint corresponding to the pull-up current of the cable is set in the controlled limitation unit 11.

EFFECT: loading of excavator bucket bottom opening mechanism takes place only when retainer is pulled.

1 cl, 2 dwg

Description

The present invention relates to electrical engineering and is intended for use on excavators in order to increase the reliability of electrical equipment and the opening mechanisms of the bottom of the excavator bucket.

Known methods for controlling the electric drive to open the bottom of the excavator bucket, in which the cable is tensioned, connected through a system of levers with a latch, by winding it onto the drum using a DC motor in two modes: pulling the cable and opening the bucket bottom by increasing the moment developed by the engine to constant the maximum value of one or successively two steps of setting the current (RF Patent No. 20112741, IPC E02F 9/020, 1994; Drozdova L.G., Kurbatova A.A. Single-bucket excavators: Design, installation and repair. - Vladivostok, DVGTU Publishing House, 2007, pp. 53-56; Efimov V.N., Tsvetkov V.N., Sadovnikov E.M. Career excavators: Worker's Handbook. - M., Nedra, 1994, S . 120-128; GM Yartsev et al. Excavators EKG-4.6A and EKG-4.6B. Design and operation. - M.: Mechanical Engineering, 1970, p. 15-21).

During the operation of the excavator, the cable is always pre-tensioned by setting the initial value of the motor current for the drive. When the driver’s team acts to open the bottom of the bucket by pressing a button on the joystick, a stepwise increase in the motor current occurs. With increasing current to a value corresponding to the first stage, accelerated rotation of the motor begins, providing additional pulling of the cable and the choice of gaps in kinematic gears. When the current increases to the value corresponding to the second stage, there is a sharp increase in torque and pulling out the bolt of the bottom of the bucket of the excavator. When the control button is released, the circuit returns to its initial state corresponding to the action of the cable pull-up current in the electric drive. At the same time, an additional current overload acts in the electric drive after pulling out the bolt until the control button is turned off. When setting a current of large magnitude, there is a strong cable tension and loading of the mechanical elements of the system, reducing their reliability and durability.

Thus, the disadvantage of the known method of controlling the electric drive to open the bottom of the excavator bucket is the low reliability of the opening mechanism due to the action of a large moment in the time interval after pulling the bolt until the control button is turned off.

Of the known technical solutions, the closest to the proposed method is a method for controlling an electric drive for opening the bottom of an excavator bucket, in which a cable is tensioned, connected through a lever system with a latch, by winding it onto a drum using a DC motor in two modes: pulling the cable and opening the bottom bucket by increasing the moment developed by the engine to a constant maximum value (Malafeev S.I., Mamai BC Electric drive for opening the bottom of the excavator bucket / Prom Industrial Energy, 1994, No. 4, pp. 9-10).

To implement the known method, a direct current electric drive with current feedback is used. During the operation of the excavator, the cable is always pre-tensioned by setting the initial current value for the drive. When the driver’s command to open the bottom of the bucket by pressing the button on the joystick, the current task increases. When the current increases to a value corresponding to the specified maximum value in the opening mode, there is a sharp increase in the mechanical moment and pulling out the bolt of the bottom of the excavator bucket. When the control button is released, the circuit returns to its initial state corresponding to the action of the cable pull-up current in the electric drive. At the same time, an additional current overload acts in the electric drive after pulling out the bolt until the control button is turned off. When setting a current of large magnitude, there is a strong cable tension and loading of the mechanical elements of the system, reducing their reliability and durability.

Thus, the disadvantage of the known method of controlling the electric drive to open the bottom of the excavator bucket is the low reliability of the opening mechanism due to the action of a large moment in the time interval after pulling the bolt until the control button is turned off.

The purpose of the proposed invention is to increase the reliability of the opening mechanism by reducing the time of the action of a large moment in the process of opening the bottom of the excavator bucket.

This goal is achieved by the fact that in the known method of controlling the electric opening of the bottom of the excavator bucket, in which the cable is tensioned, connected through a system of levers with a bolt, winding the cable onto the drum using a DC motor in two modes: pulling the cable and opening the bottom of the bucket by increasing the moment developed by the engine, in addition to the electric drive, the nominal angular speed is set, in the mode of pulling up the cable, the motor current limit is set at sufficient to select the slack of the cable, in the mode of opening the bottom of the bucket, the current limit is increased to a predetermined maximum value, the current of the motor is measured, compared with a threshold level, when the current is reduced to a threshold level in the drive, the current limit corresponding to the mode of pulling the cable is set.

Compared with the closest similar technical solution, the proposed method has the following new features:

- for the electric drive set the nominal angular velocity;

- in the mode of pulling the cable set the current limit of the motor at a level sufficient to select the slack of the cable;

- in the mode of opening the bottom of the bucket increase the current limit to a predetermined maximum value;

- measure the current of the motor;

- compare the measured current with a threshold level;

- when reducing the current to a threshold level in the electric drive, a current limit is set corresponding to the mode of pulling the cable.

Therefore, the claimed technical solution meets the requirement of "novelty."

For each of the distinguishing features, a search is made for well-known technical solutions in the field of electrical engineering, automation and mining electrical equipment.

Operations:

- for the electric drive set the nominal angular velocity;

- measure the current of the motor;

- compare the measured current with a threshold level,

electric drives for various purposes are known and used (Anuchin S.A. Electric drive control systems / M., MEI Publishing House, 2015 - 373 p.). The use of these operations in electric drives to open the bottom of the excavator bucket was not found.

Operations:

- in the mode of pulling the cable set the current limit of the motor at a level sufficient to select the slack of the cable;

- in the mode of opening the bottom of the bucket increase the current limit to a predetermined maximum value;

- when the current is reduced to a threshold level in the electric drive, a current limit is set corresponding to the cable pulling mode,

in known technical solutions of a similar purpose are not found.

Thus, these features provide the claimed technical solution according to the requirement of "significant differences".

When implementing the proposed technical solution, the reliability of the mechanism for opening the bottom of the excavator bucket is increased. As a result of the command to open the bottom of the bucket, the drive current limit increases. The current of the anchor winding increases to a value exceeding the moment of resistance of the mechanism holding the bolt. After pulling the bolt there is a sharp decrease in the load and, consequently, the current of the electric motor. The bottom opens under the action of the contents of the bucket and the rock is unloaded. The electric drive only carries out the winding of the cable on the drum at low load. When the current decreases to a preset value, a current limit is set corresponding to the cable pulling mode. Thus, loading of the mechanism for opening the bottom of the excavator bucket occurs only when pulling the bolt.

Therefore, the claimed technical solution meets the requirement of "positive effect".

The essence of the alleged invention is illustrated by drawings. In FIG. 1 shows a simplified diagram of an electric drive for opening the bottom of an excavator bucket, illustrating the proposed method. The diagram indicates:

1 - electric current regulator; 2 - threshold element; 3 - OR element; 4 - initial installation unit; 5 - power amplifier; 6 - RS-trigger; 7 - button for controlling the opening of the bottom of the bucket; 8 - signal amplifier of the current sensor; 9 - power converter of the field winding of the motor; 10 - current sensor; 11 - controlled block limiting the job current of the electric drive; 12 - field winding of the motor; 13 - voltage sensor; 14 - filter; 15 - voltage regulator; 16 - angular velocity regulator; 17 - angular velocity adjuster; 18 - working body of the excavator (arrow and handle with a bucket); 19 - a drum; 20 - cable; 21 - lever mechanism; 22 - bottom of the bucket; 23 - deadbolt, 24 - bucket. Other mechanisms of the working bodies of the excavator and electrical equipment of the excavator to simplify the drawing are not shown.

The electric drive for opening the bottom of the bucket contains a DC motor with an armature winding 16 and an excitation winding 12. The excitation winding is connected to the output of the inverter 9 of the power supply of the excitation winding 12. The motor is controlled by regulating the voltage on the anchor winding using a power amplifier 5. The electric drive is implemented using the principle of slave regulation coordinates. The main feedback is closed by voltage on the armature winding of the motor 16 using a series-connected voltage sensor 13 and filter 14. The angular speed of the motor is set using the adjuster 17 (the angular speed of the DC motor is proportional to the voltage on the armature winding). The voltage regulator 15 compares the signal for setting the angular velocity and the feedback signal acting on the output of the filter 14 and converting the error signal in accordance with the proportional (or proportional-integral) regulation law.

The output signal of the voltage regulator 15 is fed to the input of a controlled unit for setting the current limit of the electric drive 11.

The restriction block 11 is controlled by the output signal of the RS flip-flop 6: when the output signal of the RS-flip-flop corresponds to the logic zero level, the restriction block 11 is set to the limit corresponding to the rope pulling current; when the output signal of the RS-flip-flop corresponds to the level of a logical unit, the restriction block 11 sets the limit corresponding to the opening current of the bottom of the bucket. The state of the RS-trigger is determined by the action of the signals of the initial installation unit 4, the control button 7 by opening the bottom of the bucket and switching the threshold element 2.

The slave current control loop of the electric drive is organized using a current sensor 10 and a signal amplifier of the current sensor 8 and current regulator 1, which implements a proportional-integral control law. The reference signal for the current regulator 1 comes from the output of the adjustable limiting unit 11. The output signal of the current regulator 1 acts on the input of the power amplifier 5.

The operation of the electric drive opening the bottom of the excavator bucket is as follows. With the help of the adjuster 17, the angular speed reference corresponding to the nominal angular speed of the electric motor is always set in the electric drive. At the initial moment of operation of the drive, an output is applied to the output of the installation unit 4 through the OR element 3 to the R-input of the RS-flip-flop 6 and sets this RS-flip-flop into a state of logical zero at the output with a negative edge. At the same time, in the controlled block of restriction 11, a restriction is established corresponding to the current of pulling up the cable 20. The current limit of the armature winding 16 corresponds to the minimum value sufficient to create the electromagnetic moment of pulling of the cable 20 (the electromagnetic moment of the motor is proportional to the current of the armature winding 16 of the motor). When the cable is tensioned 20, the current of the armature winding 16 is equal to the set limit, the angular speed of the motor is 0.

When the control button 7 is turned on, the RS-trigger 6, due to the action on its S-input pulse, goes into a state with the level of a logical unit at the output. In this case, in block 11, the maximum value of the current limit is set. As a result of this, the current and the proportional electromagnetic moment of the motor increase sharply. This leads to pulling the bolt 23 and the opening of the bottom 22 of the bucket 24 of the excavator. After pulling the bolt 23, the load of the electric drive decreases sharply and the motor current decreases. When the current reaches the threshold level specified by the threshold element 2, the threshold element 2 is switched and RS-trigger 6 is set to a state with a logic zero level at the output. As a result of this, in the controlled block of restriction 11, a restriction is established corresponding to the current of pulling the cable.

With the considered algorithm of the electric drive, the current of the armature winding 16 of the motor is determined by the load corresponding to the mechanical force of holding the bolt 23, and only acts when pulling the bolt. Thus, loading of the mechanism for opening the bottom of the excavator bucket occurs only when pulling the bolt. The result is an increase in the reliability of the mechanism for opening the bottom of the excavator bucket.

In order to confirm the positive effect achieved by using the proposed technical solution, a simulation of the electric drive for opening the bottom of the excavator bucket using MATLAB was performed. During the simulation, the data of the drive and the mechanism of the EKG-10 excavator were used. DPM-31 engine with parameters: rated power 12 kW; rated voltage 110V; rated current 131 A; rotation speed 1300 rpm; rated torque 88 N⋅m. In a Simulink model constructed in accordance with the circuit depicted in FIG. 1, used P-voltage regulator with transfer function

H _pH (s) = k _pH ;

where k _ph - gear coefficient of the voltage regulator, k _ph = 10;

PI - current regulator with transfer function

where k _rt is the transfer coefficient of the current regulator, k _rt = 10;

T _RT - time constant of the current regulator, T _RT = 0.05 s;

power amplifier with a transmission coefficient k _y = 25.

In the controlled block of restriction 11, the following values of current limitation are set: in the mode of pulling up the cable 5A, in the mode of opening the bottom of the bucket 100 A.

In FIG. Figure 2 shows the waveform for current I, speed V and displacement Z of the cable when opening the bottom of the excavator bucket. Until time 1 s, in the controlled block of restriction 11, the current limit is set at 5 A. The motor current is maintained at a given level. The moment created by the engine at this current is not sufficient to pull out the bolt, so the rotor of the engine is inhibited (angular velocity is 0). At time 1 s, button 7 is turned on. In the controlled block of restriction 11, a current limit of 100 A is set. The motor current rises to a value corresponding to the resistance of the bolt 23. After pulling the bolt 23, the motor load decreases sharply, the current decreases. At a time of 1.4 s, the current reaches the trigger level of threshold element 2, after which a current limit of 5 A is set in the controlled block of restriction 11. The engine brakes. In this case, under the influence of the rock, the bottom of the bucket 22 is opened and the rock is unloaded. After unloading the rock (after time 2 s) due to the action of the return mechanism, the bottom of the bucket 22 is closed and it is locked with a bolt 23.

Therefore, the use in the known method of controlling the electric drive of opening the bottom of the bucket of the excavator, in which the cable is tensioned, connected through a system of levers with a latch, winding it onto the drum using a DC electric drive in two modes: pulling the cable and opening the bottom of the bucket by increasing the moment developed by the engine, in addition of the following operations: for the electric drive, the nominal angular speed is set, in the mode of pulling the cable, the current limit of the motor is set the user at a level sufficient to select the slack of the cable, in the mode of opening the bottom of the bucket, increase the current limit to a predetermined maximum value, measure the current of the motor, compare it with a threshold level, when reducing the current to a threshold level, set the current limit corresponding to the mode of pulling the cable, increases reliability the operation of the mechanism for opening the bottom of the excavator bucket by reducing the time of the action of a large moment in the process of opening the bottom of the excavator bucket.

As a result of the simulation, it was determined that the maximum motor current is 90 A, i.e. less than the established limit of 100 A. In this case, a large current is valid only for the duration of pulling the bolt.

Using the proposed method on mining excavators will improve the reliability and quality of electrical equipment.

Claims (1)

A method of controlling an electric drive for opening the bottom of an excavator bucket, in which a cable is tensioned, connected through a system of levers with a latch, winding it onto a drum with a direct current electric drive in two modes: pulling the cable and opening the bottom of the bucket by increasing the moment developed by the engine, characterized in that, in addition, the nominal angular speed is set for the electric drive, in the pull-up mode, the motor current limit is set at a level sufficient to select ENCLOSURE rope in the ladle bottom opening mode to increase the current limit to a predetermined maximum value, motor current is measured, it is compared with a threshold level, when the current to the threshold current limit level is set corresponding to mode pulling rope.

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