DOUBLE-END CHAIN TENSION FORCE CONTROL SYSTEM FOR CROSS SIDE-DUMPING TYPE FLIGHT CONVEYOR AND CONTROL METHOD THEREFOR

Description

TECHNICAL FIELD

The present invention belongs to the technical field of coal transportation on fully mechanized mining faces, and particularly relates to a double-end chain tension force control system for a cross side-dumping type flight conveyor and a control method therefor.

BACKGROUND

A flight conveyor is a “spine” of fully mechanized mining faces, and is not only a key equipment for coal flow loading and transportation, but also a core equipment for guiding a shearer and pulling a hydraulic support. In the process of cutting coals from a coal rib and transporting same in the head direction, the tension force of chains needs to be adjusted in real time. By adjusting the flight conveyor to an appropriate tension force, the service life of the chains can be prolonged effectively, thereby avoiding accidents such as chain stacking and chain breakage. At present, the dynamic compensation of elastic deformation of the chains is mainly achieved by adopting a tail tensioning system. However, the tail tensioning system has had various disadvantages since the arising, an automatic control system cannot work normally after being used for a year or even 2-3 months, and it needs to manually tension the chains. However, the effect of manual tensioning is not as good as that of automatic tensioning.

It has been found in research that, in the process of transporting coals by the flight conveyor, the tail tensioning system expands and contracts hydraulic cylinders too long in order to achieve the dynamic compensation of chain extension, resulting in aggravated wear and structural deformation of the tail tensioning system, eventually resulting in that the hydraulic cylinders are stuck and cannot expand and contract normally, so an automatic tension force control system is disabled. When the tail cannot work normally, only shutdown maintenance can be made, greatly affecting the efficiency of coal mining.

Currently, most advanced flight conveyors are all cross side-dumping type. Therefore, on such basis, in order to solve the described problem of tension force control, the present invention invents a double-end chain tension force control system for a cross side-dumping type flight conveyor and a control method therefor, where the telescopic quantity of hydraulic cylinders is halved by means of simultaneous tensioning of head-tail ends, thereby reducing the risk of structural deformation and ensuring normal extension and retraction of the hydraulic cylinders. Furthermore, when one of the head and tail systems has a fault, the other system can still work normally, thereby shortening the time of shutdown maintenance. The invention is of great significance for guaranteeing the efficient coal transportation of the flight conveyor and prolonging the service life.

SUMMARY

The present invention provides a double-end chain tension force control system for a cross side-dumping type flight conveyor and a control method therefor, in order to effectively control a chain tension force, prolong the service life of the flight conveyor, and achieve efficient coal transportation.

The present invention adopts the following technical solutions: a double-end chain tension force control system for a cross side-dumping type flight conveyor, includes:

• • a tail tensioning system, connected to a reversed loader at a tail of the flight conveyor;
  • a head tensioning system, connected to a head of the flight conveyor,
  • wherein the tail tensioning system and the head tensioning system together achieve double-end coordinated control of a chain transmission system on the flight conveyor to adjust a tension force; and
  • a control system, collecting information about the tail tensioning system and the head tensioning system and controlling same.

In some embodiments, the head tensioning system includes:

• • a transition part, cross-lapped with the reversed loader; and
  • a movable part, sliding in a conveying direction of the flight conveyor to adjust a chain tension force.

In some embodiments, the transition part includes:

• • a transition frame, two ends of the transition frame being connected to a middle groove of the flight conveyor and the movable part respectively;
  • an S coal falling plate, fixed to the transition frame; and
  • a coal guiding plate and a flow guiding plate, fixed above the S coal falling plate, the flow guiding plate being arc-shaped and being vertically arranged at a front side of the coal guiding plate and used for changing a flow direction of coals.

In some embodiments, the movable part includes:

• • a movable frame;
  • a telescopic middle groove assembly, mounted on the movable frame and capable of sliding on the movable frame, two sets of motor reducer assemblies being mounted and fixed on the telescopic middle groove assembly and jointly driving driving sprockets, and the driving sprockets being used for being connected to a flight conveyor chain; and
  • hydraulic assemblies, driving the telescopic middle groove assembly to slide on the movable frame in the conveying direction of the flight conveyor.

In some embodiments, the tail tensioning system includes the movable part.

In some embodiments, the motor reducer assemblies include permanent magnet motors and reducers, the permanent magnet motors driving the reducers.

In some embodiments, the control system includes:

• • current sensors, used for collecting input currents of the permanent magnet motors;
  • torque sensors, used for collecting output torques of the reducers;
  • hydraulic cylinder oil pressure sensors, used for collecting a pressure of hydraulic cylinders;
  • hydraulic cylinder displacement sensors, used for monitoring a pressure and a telescopic quantity of the hydraulic assemblies; and
  • an industrial personal computer, an input end of the industrial personal computer being connected to the current sensors, the torque sensors, the hydraulic cylinder oil pressure sensors and the hydraulic cylinder displacement sensors to acquire a load signal of the chain transmission system, and to complete processing and analysis of control signals, thereby controlling an action of the hydraulic cylinders to complete automatic adjustment of the tension force.

A control method for the double-end chain tension force control system for a cross side-dumping type flight conveyor, includes:

• • S1: the industrial personal computer fuses data of a current signal I and a torque signal F_torque in real time by using a deep learning algorithm to jointly judge a pressure change F and a displacement x of the hydraulic cylinders corresponding to a current coal flow rate of the flight conveyor;
  • S2: intelligent collaborative control is performed on the head tensioning system and the tail tensioning system by using a deep reinforcement learning algorithm;
  • S3: when the hydraulic assemblies are stuck or a structure of a tensioning system has faults such as bending and deformation, the system is unable to adjust a tension force of the chain transmission system normally, a tension force of a head or tail tension force control system is found to reach a set value F/2, but a telescopic stroke of the control system is found not to reach a specified stroke distance x/2 due to the faults, the control system is capable of judging that there is a fault at the end, and the hydraulic cylinders are unable to extend and retract normally; at this time, an output force of the hydraulic cylinders is partially offset due to structural components subjected to bending deformation and being stuck, so that the output force of the hydraulic cylinders is unable to be fully transmitted to the chain transmission system; and if, at this time, an output force of the end is F/2 and a displacement is x′, a telescopic quantity of the hydraulic cylinders of the tension force control system with the end faulted is transferred to the tension force control system at the other end that is capable of working normally, and an output displacement of the other end is x/2+(x/2−x′), so that coal transportation work is capable of proceeding normally;
  • S4: if a tension force and a telescopic stroke of one end are unable to reach specified values, control over the end will be abandoned, and all tension force control will be transferred to the other end to complete tension force adjustment; and
  • S5: an alarm is raised to remind workers to carry out scheduled shutdown maintenance.

The step S1 includes:

• • S11: only the tail tensioning system is allowed to work, to collect a complete signal process of the current signal I and the torque signal F_torque of the flight conveyor in n coal transportation cycles, and a minimum pressure F₀ and a minimum displacement x₀ of the hydraulic cylinders are calibrated manually when no load; and a maximum pressure F₁ and a maximum displacement x₁ are calibrated manually when a coal flow rate is maximum;
  • S12: pressures are linearized, that is, a pressure change throughout the process satisfies F=k₁×(F₁−F₀), k₁∈[0, 1]; and a displacement change throughout the process satisfies x=k₂×(x₁−x₀), k₂∈[0, 1]; and
  • S13: collected data are subjected to pre-processing and neural network training, and a trained neural network is deployed to the industrial personal computer.

The step S2 includes:

• • S21: mathematical models of the head tensioning system, the tail tensioning system and the chain transmission system of the flight conveyor are established;
  • S22: during training of tension force adjustment, deep reinforcement learning training is performed by taking minimum chain tension force fluctuation, a most stable adjustment speed of the hydraulic cylinders, and smooth control quantity switch as reward values and taking a required tension force that the hydraulic cylinders are unable to reach and a large tension force fluctuation amplitude as penalty terms, and finally trained models are deployed to the industrial personal computer; and
  • S23: in a real environment, when the tail tensioning system (1) and the head tensioning system (2) work normally, the tail tensioning system (1) and the head tensioning system (2) respectively output a tension force of F/2 under control of deep reinforcement learning, two ends extend and retract simultaneously, at the same time, whether telescopic strokes of the two ends are x/2 is monitored, and if a telescopic distance is reached, the tensioning systems work normally, and the tension force is adjusted to be appropriate.

Compared with the prior art, the present invention has the following beneficial effects:

• • 1. According to the present invention, a telescopic head mechanism for the cross side-dumping type flight conveyor is designed, and the double-end coordinated control of the chain transmission system can be achieved to rapidly adjust the tension force.
  • 2. According to the present invention, by using a method for tensioning two ends simultaneously, the extension and retraction stroke of the hydraulic cylinders can be halved, thereby effectively reducing the risk of structural deformation and improving the service life of the tensioning systems.
  • 3. The tension force control system of the present invention shortens the response time of adjusting the tension force by a multiple, thereby improving the responsivity of the system.
  • 4. According to the present invention, a fault can be judged, and when the tensioning system at one end has a fault and cannot work normally, the tension force control system at the other end can still work normally for coal transportation, thereby improving the mining efficiency and reducing a nonscheduled shutdown rate.
  • 5. Judgment is less prone to errors based on a deep learning tension force determination method for data fusion, and control is more intelligent and flexible based on a control strategy for deep reinforcement learning. The accuracy and robustness of the system are improved overall.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an overall structure of the present invention;

FIG. 2 is a schematic structural diagram I of a head tensioning system of the present invention;

FIG. 3 is a schematic structural diagram II of the head tensioning system of the present invention;

FIG. 4 is a schematic structural diagram III of the head tensioning system of the present invention;

FIG. 5 is a schematic structural diagram IV of the head tensioning system of the present invention;

FIG. 6 is a schematic structural diagram I of a movable part of the head tensioning system of the present invention;

FIG. 7 is a schematic structural diagram II of the movable part of the head tensioning system of the present invention;

FIG. 8 is a schematic structural diagram of a telescopic part of the head tensioning system of the present invention;

FIG. 9 is a structural section diagram of the telescopic part of the head tensioning system of the present invention;

FIG. 10 is a schematic diagram of cooperation of an upper telescopic plate and a lower telescopic plate of the present invention;

where:

• • 1—Tail tensioning system,
  • 2—Head tensioning system,
  • 21—Motor reducer assembly,
  • 22—Connection gasket frame,
  • 231—Upper protective cover,
  • 232—Side protective cover,
  • 24—Coal guiding plate,
  • 241—Coal guiding plate fixing plate,
  • 242—Cross beam,
  • 25—Flow guiding plate,
  • 26—Reversed loader,
  • 261—Reversed loader chain,
  • 262—Reversed loader flight bar,
  • 263—Reversed loader sprocket,
  • 27—Connection pin,
  • 28—Bottom plate,
  • 281—Slide rail,
  • 291—Flight conveyor chain,
  • 292—Flight conveyor flight bar,
  • 293—Driving sprocket, 294—Sprocket shaft,
  • 31—Hydraulic cylinder connection block, 33—Hydraulic cylinder,
  • 41—Transition part, 42—Movable part,
  • 411—S coal falling plate,
  • 412—Transition frame,
  • 51—Lower telescopic plate,
  • 511—Lower telescopic plate supporting plate,
  • 512—Guide lug,
  • 52—Upper telescopic plate,
  • 521—Upper telescopic plate fixing frame,
  • 522—Fixing frame supporting plate,
  • 53—Tongue plate,
  • 54—Wing plate,
  • 55—Side stop plate,
  • 56—Upper press plate,
  • 57—Movable frame,
  • 58—Derailleur.

DETAILED DESCRIPTION OF THE EMBODIMENTS

To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following clearly and completely describes the technical solutions in the embodiments of the present invention. Apparently, the described embodiments are a part rather than all of the embodiments of the present invention. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

As shown in FIG. 1 and FIG. 2, a double-end chain tension force control system for a cross side-dumping type flight conveyor, includes:

• • a tail tensioning system 1, connected to a reversed loader 26 at a tail of the flight conveyor;
  • a head tensioning system 2, connected to a head of the flight conveyor,
  • wherein the tail tensioning system 1 and the head tensioning system 2 together achieve double-end coordinated control of a chain transmission system on the flight conveyor to adjust a tension force; and
  • a control system, collecting information about the tail tensioning system 1 and the head tensioning system 2 and controlling same.

Specifically, a flight conveyor chain 291 is arranged on the flight conveyor, the flight conveyor chain 291 and a flight conveyor flight bar 292 are mounted in a spaced manner, and the flight conveyor flight bar 292 is used for pushing coal transportation. Two ends of the flight conveyor chain 291 are mounted on different driving sprockets 293 respectively. However, in the present application, the two driving sprockets 293 are fixed to the tail tensioning system 1 and the head tensioning system 2, respectively, and a tension force is adjusted by adjusting the positions of the two driving sprockets 293 of the tail tensioning system 1 and the head tensioning system 2.

The head tensioning system 2 includes:

• • a transition part 41, cross-lapped with the reversed loader 26; and
  • a movable part 42, sliding in a conveying direction of the flight conveyor to adjust a chain tension force.

Specifically, the transition part 41 and the reversed loader 26 are cross-lapped, and connected by a connection pin 27. Coals conveyed to the head are transferred to the reversed loader 26 under the drive of the flight conveyor chain 291, the flight conveyor flight bar 292 and the driving sprockets 293, then coal transportation is completed through the cooperation of a reversed loader chain 261, a reversed loader flight bar 262 and a reversed loader sprocket 263 of the reversed loader 26, the transition part 41 is fixedly connected to a bottom plate 28, and the movable part 42 is located on an upper side of the bottom plate 28 and can slide on the upper side of the bottom plate 28, so that the chain tension force is adjusted.

The transition part 41 includes:

• • a transition frame 412, two ends of the transition frame 412 being connected to a middle groove of the flight conveyor and the movable part 42 respectively;
  • an S coal falling plate 411, fixed to the transition frame 412; and
  • a coal guiding plate 24 and a flow guiding plate 25, fixed above the S coal falling plate 411, the flow guiding plate 25 being arc-shaped and being vertically arranged at a front side of the coal guiding plate 24 and used for changing a flow direction of coals.

Specifically, one end of the transition part 41 is connected to the movable part 42 of the head tensioning system 2 to achieve tension force control, the other end thereof is connected to the middle groove to complete coal transportation, the S coal falling plate 411 is fixedly connected to the transition frame 412 via a bolt to ensure that the coals are smoothly transferred from the flight conveyor to the reversed loader 26, the coal guiding plate 24 and the flow guiding plate 25 are fixedly connected and located above the S coal falling plate 411, and the flow guiding plate 25 is arc-shaped, so that the flow direction of the coals can be changed smoothly to ensure coal transfer. A coal guiding plate fixing plate 241 on a side surface of the transition part 41 and a cross beam 242 above the transition part are fixedly connected to the coal guiding plate 24 to complete limiting and fixing.

The movable part 42 includes:

• • a movable frame 57;
  • a telescopic middle groove assembly, mounted on the movable frame 57 and capable of sliding on the movable frame 57, two sets of motor reducer assemblies 21 being mounted and fixed on the telescopic middle groove assembly and jointly driving driving sprockets 293, and the driving sprockets 293 being used for being connected to a flight conveyor chain 291; and
  • hydraulic assemblies, driving the telescopic middle groove assembly to slide on the movable frame 57 in the conveying direction of the flight conveyor.

Specifically, as shown in FIG. 5 to FIG. 10, the telescopic middle groove assembly includes: wing plates 54, side stop plates 55, a lower telescopic plate 51, a lower telescopic plate supporting plate 511, an upper telescopic plate 52, an upper telescopic plate fixing frame 521, a fixing frame supporting plate 522, and a tongue plate 53, and the lower telescopic plate 51 is lapped on an upper side of the transition frame 412 and fixedly connected thereto; meanwhile, the lower telescopic plate supporting plate 511 on a lower side of the lower telescopic plate 51 is fixedly connected to the transition frame 412, the upper telescopic plate 52 is located on an upper side of the lower telescopic plate 51 and cross-lapped therewith, and the upper telescopic plate 52 can slide on an upper surface of the lower telescopic plate 51, so that main actions of extension and retraction are achieved; the lower telescopic plate 51 is provided with two guide lugs 512 which are connected to the upper telescopic plate 52 in an inserted manner, so that the function of guiding can be provided for the upper telescopic plate 52 when extending and retracting; furthermore, upper surfaces of the guide lugs 512 and an upper surface of the upper telescopic plate 52 are on the same plane, and the upper telescopic plate and the lower telescopic plate are provided with chamfers.

A side surface of the upper telescopic plate 52 is fixedly connected to the movable frame 57, a lower side thereof is connected to the upper telescopic plate fixing frame 521, the upper telescopic plate fixing frame 521 is provided with the fixing frame supporting plate 522 and fixedly connected to the movable frame 57, a derailleur 58 is fixedly connected to the upper telescopic plate fixing frame 521 via a bolt, the tongue plate 53 is fixedly connected to the upper telescopic plate 52 via a bolt and located on the upper surface of the upper telescopic plate 52, the tongue plate 53 is a consumptive part and can be updated and replaced, the two wing plates 54 are located on two sides of the transition frame 412 and fixedly connected to the transition frame 412, and chamfers are designed on the wing plates 54, so that the reversal of the flight conveyor can be achieved; the side stop plates 55 are fixedly connected to the wing plates 54, and an upper press plate 56 is fixedly connected to the movable frame 57 and presses on the wing plates 54 and the side stop plates 55.

The hydraulic assemblies include hydraulic cylinders 33 and hydraulic cylinder connection blocks 31.

The hydraulic assemblies are located on a lower side of a connection gasket frame 22, one is on a left side, and the other one is on a right side; one end of the hydraulic cylinders 33 is rotationally connected to the bottom plate 28 via connection pins, and the other end thereof is rotationally connected to the hydraulic cylinder connection blocks 31; and the hydraulic cylinder connection blocks 31 are rotationally connected to the movable frame 57, so that power of the hydraulic cylinders 33 is transferred to the movable frame 57.

Slide rails 281 are arranged on the bottom plate 28, one is on a left side of the movable frame 57, and the other one is on a right side thereof, so that the movable frame 57 can move forward and backward along the slide rails 281 under the action of pushing of the hydraulic cylinders 33.

The tail tensioning system 1 includes the movable part 42.

Specifically, the structure of the tail tensioning system 1 is the same as that of the movable part 42 in the head tensioning system 2, and the tail tensioning system 1 is arranged at the tail of the flight conveyor.

The motor reducer assemblies 21 include permanent magnet motors and reducers, the permanent magnet motors driving the reducers. The head tensioning system and the tail tensioning system each have the two sets of motor reducer assemblies, which are located on left and right sides of the tensioning system and fixedly connected to one side of the connection gasket frame, and the other side of the connection gasket frame is fixedly connected to the movable frame.

The control system includes:

• • current sensors, used for collecting input currents of the permanent magnet motors;
  • torque sensors, used for collecting output torques of the reducers;
  • hydraulic cylinder oil pressure sensors, used for collecting a pressure of hydraulic cylinders;
  • hydraulic cylinder displacement sensors, used for monitoring a pressure and a telescopic quantity of the hydraulic assemblies; and
  • an industrial personal computer, an input end of the industrial personal computer being connected to the current sensors, the torque sensors, the hydraulic cylinder oil pressure sensors and the hydraulic cylinder displacement sensors to acquire a load signal of the chain transmission system, and to complete processing and analysis of control signals, thereby controlling an action of the hydraulic cylinders to complete automatic adjustment of the tension force.

The current sensors, the hydraulic cylinder oil pressure sensors, the torque sensors and the hydraulic cylinder displacement sensors are each four, the current sensors are connected to a power cord of the permanent magnet motors to measure input currents of the four motors, and the hydraulic cylinder oil pressure sensors and the hydraulic cylinder displacement sensors are connected to the hydraulic cylinders to monitor the pressure and telescopic quantity of the hydraulic cylinders. The input end of the industrial personal computer is connected to the current sensors, the torque sensors, the hydraulic cylinder oil pressure sensors and the hydraulic cylinder displacement sensors to acquire a load signal of the chain transmission system, and to complete processing and analysis of control signals, thereby controlling an action of the hydraulic cylinders to complete automatic adjustment of the tension force.

The current sensors can be Hall current sensors from FULLKON, the oil pressure sensors can be NS-P-I series pressure transmitters from Tianmu, the displacement sensors can be non-contact magnetostrictive displacement sensors from Germanjet, and the industrial personal computer can be IPC series from Advantech.

A control method for the double-end chain tension force control system for a cross side-dumping type flight conveyor, includes:

• • S1: the industrial personal computer fuses data of a current signal I and a torque signal F_torque in real time by using a deep learning algorithm to jointly judge a pressure change F and a displacement x of the hydraulic cylinders corresponding to a current coal flow rate of the flight conveyor;
  • According to the actual working process, the coal flow rate is directly proportional to the current and the torque, and therefore the two signals can reflect the coal flow rate.

Firstly, only the tail tensioning system is allowed to work, to collect a complete signal process of the current signal I and the torque signal F_torque of the flight conveyor in n coal transportation cycles. A minimum pressure F₀ and a minimum displacement x₀ of the hydraulic cylinders are calibrated manually when no load; and a maximum pressure F₁ and a maximum displacement x₁ are calibrated manually when a coal flow rate is maximum.

Pressures are linearized, that is, a pressure change throughout the process satisfies F=k₁×(F₁−F₀), k₁∈[0, 1]; and a displacement change throughout the process satisfies x=k₂×(x₁−x₀), k₂∈[0, 1].

In the present invention, n=3, and the current signal I, the torque signal F_torque, and the total pressure change F are averaged. Deep learning is performed by taking the current signal I and the torque signal F_torque as inputs and taking the total pressure change F and the total displacement change x as outputs, to complete signal mapping.

The deep learning algorithm is preferably a convolutional neural network. The pre-processing of data includes normalization and normalization. 80 percent of the data are training sets and 20 percent thereof are test sets. During training, network parameters are optimized by a back propagation algorithm to minimize a loss function. The performance of models is evaluated on the test sets, to adjust a network structure, an activation function, etc. by taking the maximum accuracy as a target, to determine an optimal mapping relationship finally. Thus, the network is deployed to the industrial personal computer.

S2: intelligent collaborative control is performed on the head tensioning system and the tail tensioning system by using a deep reinforcement learning algorithm.

Firstly, the algorithm needs to be trained as follows:

• • mathematical models of the head tensioning system, the tail tensioning system and the chain transmission system of the flight conveyor are established, the models can accurately reflect the physical process of tension adjustment, and a training environment of deep reinforcement learning is built based on the mathematical models.

The chain transmission system is simplified based on a discrete element method, to be discretized into 2n mass blocks. The more n after discretization is, the more accurate the models are, but the larger the calculation amount is. Values need to be taken multiple times according to a specific working condition for verification determination. The adjacent mass blocks are connected by a Kelvin-Voigt model, and the mathematical models are constructed and solved based on a Newton-Euler method. The number of the mass block at a head sprocket is 1, the number of the mass block at a tail sprocket is n+1, the chain mass blocks on the upper side are 2 to n, and the chain mass blocks on the lower side are n+1 to 2n.

The mathematical model of the head tensioning system is:

{ 1 2 ⁢ m ? ⁢ R ? ⁢ θ ? ? + k 1 ( R ? ⁢ θ ? - x 2 ) + c 1 ( R ? ⁢ θ . ? - x . 2 ) + k 2 ⁢ n ( R ? ⁢ θ ? - x 2 ⁢ n ) + c 2 ⁢ n ( R ? ⁢ θ . ? - x . 2 ⁢ n ) = T ? R ? - f ? m ? ⁢ x ¨ ? = F ? - F 1 - F 2 ⁢ n ? indicates text missing or illegible when filed

• • where m_t: a mass of the head tensioning system, kg; R_t: a radius of the head sprocket, m; {umlaut over (θ)}_t: an angular acceleration of the head sprocket, rad/s²; {dot over (θ)}_t: an angular speed of the head sprocket, rad/s; θ_t: an angle of rotation of the head sprocket, rad; k_i: a stiffness coefficient of the chain mass blocks, i∈[1, 2n], N/m; c₁: a damping coefficient of the chain mass blocks, i∈[1, 2n], N s/m; x_j: a speed of the chain mass blocks, j∈[1, 2n], m/s; x_j: a displacement of the chain mass blocks, j∈[1, 2n], m/s; T_t: an input torque of the head sprocket, N·m; f_t: a rotational resistance of the head sprocket, N; F_t: a head tension force, N; F₁: a tension force of the chain mass block 1, N; F_2n: a tension force of the chain mass block 2n, N.

The mathematical model of the tail tensioning system is:

{ 1 2 ⁢ m ? ⁢ R ? ⁢ θ ¨ ? + k n + 1 ( R ? ⁢ θ ? - x n + 2 ) + c ? ( R ? ⁢ θ . ? - x . ? ) + k ? ( R ? ⁢ θ ? - x ? ) + c ? ( R ? ⁢ θ . ? - x . ? ) = T ? R ? - f ? m ? ⁢ x ¨ ? = F ? - F ? - F n - 1 ? indicates text missing or illegible when filed

where m_w: a mass of the tail tensioning system, kg; R_w: a radius of the tail sprocket, m; {umlaut over (θ)}_w: an angular acceleration of the tail sprocket, rad/s²; {dot over (θ)}_w: an angular speed of the tail sprocket, rad/s; θ_w: an angle of rotation of the tail sprocket, rad; k₁: a stiffness coefficient of the chain mass blocks, i∈[1, 2n], N/m; c_i: a damping coefficient of the chain mass blocks, i ∈[1, 2n], N s/m; x_j: a speed of the chain mass blocks, j∈[1, 2n], m/s; x_j: a displacement of the chain mass blocks, j∈[1, 2n], m/s; T_w: an input torque of the tail sprocket, N·m; f_w: a rotational resistance of the tail sprocket, N; F_w: a head tension force, N; F_n: a tension force of the chain mass block n, N; F_n+1: a tension force of the chain mass block n+1, N.

The mathematical model of the chain transmission system (total 2n−2 equations) is:

{ m 2 ⁢ x ¨ 2 + k 2 ( x 2 - x 3 ) + c 2 ( x . 2 - x . 3 ) + k 1 ⁢ ( x 2 - R ? ⁢ θ ? ) + c 1 ⁢ ( x 2 - R ? ⁢ θ . ? ) = - f 2 … m 2 ⁢ n ⁢ x ¨ 2 ⁢ n + k 2 ⁢ n ( x 2 ⁢ n - R ? ⁢ θ ? ) + c 2 ⁢ n ( x . 2 ⁢ n + R ? ⁢ θ . ? ) + k 2 ⁢ n - 1 ⁢ ( x 2 ⁢ n - x 2 ⁢ n - 1 ) + c 2 ⁢ n - 1 ( x . 2 ⁢ n - x . 2 ⁢ n - 1 ) = - f 2 ⁢ n ? indicates text missing or illegible when filed

where a mass of the chain mass blocks, y∈[2, n]∪[n+1, 2n], kg; x_j: an acceleration of the chain mass blocks, j∈[1, 2n], m/s; x_j: a speed of the chain mass blocks, j∈[1, 2n], m/s; x_j: a displacement of the chain mass blocks, j∈[1, 2n], m/s; R_t: a radius of the head sprocket, m; θ_t: an angle of rotation of the head sprocket, rad; {dot over (θ)}t: an angular speed of the head sprocket, rad/s; f_y: a running resistance of the chain mass blocks, y∈[2, n]∪[n+1, 2n], N; k₁: a stiffness coefficient of the chain mass blocks, i∈[1, 2n], N/m; c_i: a damping coefficient of the chain mass blocks, i∈[1, 2n], N s/m.

During training of tension force adjustment, by taking minimum chain tension force fluctuation, a most stable adjustment speed of the hydraulic cylinders, and smooth control quantity switch as reward values and taking a required tension force (tension force is F/2 or F, F/2 being a training tension force when two ends can work normally, and F being a tension force only when a single end can work normally) that the hydraulic cylinders are unable to reach and a large tension force fluctuation amplitude as penalty terms, the deep reinforcement learning algorithm is trained, so that the algorithm is constantly iteratively updated in the environment to achieve the best effect. Training is preferably performed using multi-agent deep deterministic policy gradients (MADDPG). Finally, the trained algorithm is deployed to the industrial personal computer.

In a real environment, when the head and tail systems work normally, the head tensioning system and the tail tensioning system respectively output a tension force of F/2 under control of deep reinforcement learning, two ends extend and retract simultaneously, at the same time, whether telescopic strokes of the two ends are x/2 is monitored, and if a telescopic distance is reached, the tensioning systems work normally, and the tension force is adjusted to be appropriate.

S3: when the hydraulic assemblies are stuck or a structure of a tensioning system has faults such as bending and deformation, the system is unable to adjust a tension force of the chain transmission system normally, a tension force of a head or tail tension force control system is found to reach a set value F/2, but a telescopic stroke of the control system is found not to reach a specified stroke distance x/2 due to the faults, the control system is capable of judging that there is a fault at the end, and the hydraulic cylinders are unable to extend and retract normally. At this time, an output force of the hydraulic cylinders is partially offset due to structural components subjected to bending deformation and being stuck, so that the output force of the hydraulic cylinders is unable to be fully transmitted to the chain transmission system. If, at this time, an output force of the end is F/2 and a displacement is x′, a telescopic quantity of the hydraulic cylinders of the tension force control system with the end faulted is transferred to the tension force control system at the other end that is capable of working normally, and an output displacement of the other end is x/2+(x/2−x′), so that coal transportation work is capable of proceeding normally;

• • S4: if a tension force and a telescopic stroke of one end are unable to reach specified values, control over the end will be abandoned, and all tension force control will be transferred to the other end to complete tension force adjustment; and
  • S5: an alarm is raised to remind workers to carry out scheduled shutdown maintenance.

Finally, it should be noted that: the above embodiments are only used to describe the technical solutions of the present invention, but not to limit them. Although the present invention is described in detail with reference to the above embodiments, persons of ordinary skill in the art should understand that: the technical solutions recorded in the above embodiments still can be modified, or part or all of the technical features can be replaced equivalently; however, those modifications or replacements do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.