CN101898681A - Belt Conveyor Load Prediction Control Method - Google Patents

Abstract

The invention discloses a belt conveyor load prediction control method, which includes cascading an upper-level belt conveyor and a lower-level belt conveyor, wherein the load prediction control method includes the following steps: detecting the rotational speed and operating current of each motor of the upper-level belt conveyor, and passing Calculate the real-time transportation volume of the upper-level belt conveyor; detect the speed and operating current of each motor of the lower-level belt conveyor, and obtain the real-time transportation volume of the lower-level belt conveyor through calculation; compare the real-time transportation volume of the upper-level belt conveyor with the real-time transportation volume of the lower-level belt conveyor , if the preset load change threshold is exceeded, the speed value of each motor of the lower belt conveyor is adjusted and set according to the real-time transportation volume of the upper belt conveyor. The load predictive control method of the belt conveyor provided by the invention can perform predictive control on the load of the belt conveyor, and the control is simple and accurate, thereby reducing energy consumption and saving costs.

Description

Belt Conveyor Load Prediction Control Method

technical field

The invention relates to a load prediction control method, in particular to a belt conveyor load prediction control method.

Background technique

The belt transmission system is the main equipment to ensure high production and high efficiency in modern coal mines. Due to the special production conditions of coal mines, the amount of coal transported by the belt conveyor system is uneven. Under light load or no load, the high-speed operation of the belt conveyor system will cause serious wear and tear on the mechanical transmission system, and at the same time, the power consumption is also higher than that of low-speed operation. much larger.

At present, most of the motor systems of the domestic coal mine belt transportation system often work at full voltage and full speed, but not at full load, but also at no-load for part of the time. After the belt conveyor realizes speed regulation operation, due to the transportation characteristics and safety requirements of the coal mine belt conveyor , The belt conveyor is still running at a constant speed, and the running speed of the belt conveyor is not adjusted in real time, which greatly reduces the use effect of the frequency converter. Therefore, it is particularly important to adjust the speed of the belt conveyor in real time and realize the predictive control of the speed according to the load situation.

For example, due to the limitation of environmental conditions, the belt conveyor in the underground mining area generally has the phenomenon of under-load operation, and the energy waste is very serious. Occasionally, the belt conveyor has a large amount of coal passing through, forming a coal pile phenomenon. Therefore, the reasonable operation mode of the belt conveyor is to adjust the running speed of the belt conveyor according to the amount of coal passing, so that the speed is fast when the amount of coal is large, and the speed is slow when the amount of coal is small, so that the system can run safely and smoothly. achieve maximum energy utilization.

Coal mine belt conveyors are generally belt groups. A main coal flow transportation system is often composed of several belt conveyors, coal feeders and scraper conveyors, and a pithead is composed of several main coal flow transportation systems. The transportation work from the mining area to the pit mouth can only be completed through several or even dozens of belt conveyors. Therefore, it is necessary to carry out predictive control on the load of the belt conveyor to achieve the purpose of safe, stable and efficient operation of the belt conveyor.

"Electrical Application" 2006 Volume 25 No. 9 "Mine Underground Belt Conveyor Intelligent Control System" proposes to use the current signal of the previous belt conveyor as the control parameter. For a belt conveyor system running at a constant speed, the running current of the motor can reflect the transportation volume of the belt conveyor, but for the variable frequency belt conveyor system, the current can only reflect the torque of the upper belt conveyor, and cannot represent the transportation volume of the belt conveyor. Therefore, the control method mentioned in this document is only suitable for the variable frequency speed regulation predictive control of the upper belt conveyor in the constant speed operation mode, and the predictive control is not accurate enough. In addition, the current mentioned in this document is to directly connect the current acquisition signal to the control device through acquisition, and the connection line is complicated.

Contents of the invention

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Figure 1 is a schematic diagram of the tension analysis of a belt conveyor with a single driving pulley.

Please refer to Fig. 1, the belt conveyor generally includes a driving pulley 1 and a driven pulley 2 connected by a belt, and an idler roller 4 is arranged on the belt, and a tensioning pulley 3 may also be provided on the belt conveyor to adjust the tension of the belt.

1) Calculation of belt traction force

F=F _Z2 -F _Z1 = (F _t1 …+F _tn )+F _x (2)

According to the basic principles of mechanics:

F _t1 …+F _tn = μ(Mg+M _P g)COSθ (3)

F _x = MgSINθ (4)

In the formula: F _t1 is the friction force of the first roller, F _tn is the friction force of the nth roller, F _x is the sliding force of the material.

F=μ(Mg+M _PJ g)COSθ+MgSINθ (5)

In the formula: M is the total mass of the material, M _pJ is the total mass of the tight side belt, μ is the friction coefficient between the belt and the roller, θ is the inclination angle of the belt conveyor, and g is the acceleration of gravity.

2) Calculation of motor torque

The belt conveyor is generally driven by a three-phase asynchronous motor, so the belt conveyor driven by a three-phase asynchronous motor is taken as an example below.

The drive torque of the drive motor is:

T _d = (μCOSθ+SINθ) Mg D/2 /i + T _s (6)

In the formula: i is the transmission ratio of the belt conveyor, T _s is the no-load torque of the belt conveyor, and D is the diameter of the driving pulley.

Due to the effect of the frequency converter, the slip rate of the motor does not change much at any speed, so according to the torque formula of the motor:

          (7)

(7)

In the formula: T _m is the output mechanical torque of the motor, and P _m is the input electric power of the motor.

基本不变，电机运行的功率因数也变化不大，因此电机的输出机械转矩于电机的输入电流成正比例关系，因此可以通过检测电机的输入电流来计算电机的输出机械转矩:It can be seen that when the motor efficiency does not change much, the output torque of the motor is proportional to the input current of the motor, and the torque of the motor is proportional to the square of the input voltage of the motor. power on hold

Basically unchanged, the power factor of the motor operation does not change much, so the output mechanical torque of the motor is proportional to the input current of the motor, so the output mechanical torque of the motor can be calculated by detecting the input current of the motor:

(8)

In the formula: T _me is the rated mechanical torque output by the motor, and I _e is the rated current of the motor.

3) Calculation of real-time transportation volume of belt conveyor

From the above analysis, it can be seen that the torque of the belt conveyor can be obtained by detecting the input current of the belt conveyor and the operating speed of the motor during the operation of the belt conveyor, and the thickness of the coal seam of the belt conveyor can be known through the torque. The calculation method is as follows:

From formula (6) we can see

Mg=(T _d - T _s )/( (μCOSθ+SINθ) D/2 /i) (9)

The no-load torque of the belt conveyor can be obtained by detecting the no-load operating power of the belt conveyor. The load torque of the belt conveyor should be equal to the output torque of the motor.

So substituting (8) into (9) can get:

Mg=(I/I _e T _me - T _s )/ ( (μCOSθ+SINθ) D/2 /i) (10)

The rated torque of the motor can be obtained from the basic parameters of the motor or the data of the type test of the motor.

The above formula (10) has calculated the weight of the material on the belt conveyor, then the mass of coal per unit length can be obtained, namely:

ρ= Mg/L=(I/I _e T _me - T _s )/( (μCOSθ+SINθ) D/2 /i) /L (11)

In the formula: ρ is the material weight per unit length, and L is the length of the belt conveyor.

The real-time transportation volume of the belt conveyor is:

MgV=πD ² n/i ² (I/I _e T _me - T _s )/ (μCOSθ+SINθ) /L (12)

In the formula: n is the motor speed, Mgv is the real-time transport volume of the belt conveyor.

Fig. 2 is a schematic diagram of the working principle of the belt conveyor load prediction control of the present invention.

Please refer to Figure 2. In order to realize the load prediction control of the belt conveyor and meet the requirement of adjusting the running speed of the belt conveyor in real time according to the load situation, it is sufficient to ensure that the real-time transport volumes of the lower belt conveyor 6 and the upper belt conveyor 5 are equal. In practical applications In order to ensure safety, generally the transport capacity of the lower belt conveyor 6 is slightly greater than the transport capacity of the upper belt conveyor 5; if there are two or more upper belt conveyors, it is only necessary to make the transport capacity of the belt conveyor slightly greater than all the belts of the upper level The transport capacity of the machine and can be.

If the belt conveyor is driven by multiple motors, the transportation volume of the belt conveyor can be calculated according to the calculation method of (12) according to the operating current and speed of each motor of the belt conveyor, and the sum of the calculation results is the real-time transportation of the belt conveyor quantity.

Since the real-time transport volume of the belt conveyor is related to the running speed and current of the motor, by implementing constant torque control on the belt conveyor, the given value of the controlled load torque can be set. In order to achieve a better energy-saving effect, generally set The given value of the load torque should be as large as possible, so as to reduce the running speed of the belt conveyor as much as possible and improve the energy efficiency of the belt conveyor. However, for safety, a certain margin should be left when setting.

During the actual load predictive control operation, since the load increase of the upper belt conveyor starts from the front end of the belt conveyor, the load increase of the lower belt conveyor will have a lagging process. Therefore, according to the length and running speed of the belt conveyor, it is only necessary to delay the increase of the rotational speed of the lower belt conveyor for a certain period of time; similarly, when the load decreases and the rotational speed is reduced, the same delay is also required.

The specific delay time is:

t=L/(πDn/i) (13)

The delay time is calculated by the parameters of the upper belt conveyor. In actual operation, the motor speed changes in real time but the speed does not change suddenly. Therefore, it is only necessary to perform delay control according to the real-time speed calculation results to meet the requirements.

The belt conveyor automatically adjusts the rotation speed according to the load condition, which reduces the running speed of the belt conveyor as much as possible, reduces the loss of the belt conveyor, improves the energy efficiency of the belt conveyor, and prolongs the life of the belt conveyor. User feedback is good.

The same method can realize the predictive control of the belt group. Before the load changes, the predicted speed of the belt conveyor is given. Combined with the constant torque control of the belt conveyor, the energy-saving control of the belt Accidents such as instantaneous overload of the belt conveyor caused by torque control, broken belt caused by torque mutation, etc.

The upper-level belt conveyor can directly transmit the real-time transportation volume of the upper-level belt conveyor to the lower-level belt conveyor through communication (suitable for belt group transformation together) or motor operating current and motor speed (suitable for only one belt conveyor). If multi-level belt conveyors are cascaded, the belt conveyors at each level will calculate the transport volume of the belt conveyors at each level and then transmit them to the next level. However, it is not necessary to transform all the belt conveyors at the same time, so the motor of the upper belt conveyor can also be replaced. The operating current and motor speed are transmitted to the lower-level belt conveyor, and the transport volume is calculated by the modified belt conveyor control system, so that the control program of the upper-level belt conveyor does not need to be modified. The communication method can adopt the serial port, industrial Ethernet, field bus, wireless communication and other methods commonly used in the industry.

In the above belt conveyor load prediction control method, wherein, the lower belt conveyor can adjust the motor speed by means of frequency conversion. During control, the maximum torque allowed for long-term operation of the motor of the lower belt conveyor can be set according to safety and other regulations. The control system keeps the torque constant and controls the motor’s running speed at this value to ensure system safety and keep safety regulations. margin.

Fig. 3 is a flow chart of the belt conveyor load prediction control in the present invention.

Please refer to Fig. 3, the belt conveyor load prediction control method provided by the present invention includes a cascaded upper belt conveyor and a lower belt conveyor, wherein the load prediction control method includes the following steps:

Step S301: Detect the rotational speed and operating current of each motor of the upper belt conveyor, and obtain the real-time transportation volume of the upper belt conveyor through calculation;

Step S302: Detect the rotational speed and operating current of each motor of the lower belt conveyor, and obtain the real-time transportation volume of the lower belt conveyor through calculation;

Step S303: compare the real-time transportation volume of the upper-level belt conveyor with the real-time transportation volume of the lower-level belt conveyor, if it exceeds the preset load change threshold, go to step S304, otherwise return to step S301 for loop control;

Step S304: adjusting and setting the rotational speed values of the motors of the lower belt conveyor according to the real-time transportation volume of the upper belt conveyor.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be defined by the claims.

Claims (5)

1. a belt conveyor load forecasting control method, comprising cascading upper-level belt conveyor and lower-level belt conveyor, is characterized in that, described load forecasting control method comprises the steps: Detect the speed and operating current of each motor of the upper belt conveyor, and obtain the real-time transportation volume of the upper belt conveyor through calculation; Detect the speed and operating current of each motor of the lower belt conveyor, and obtain the real-time transportation volume of the lower belt conveyor through calculation; Comparing the real-time transportation volume of the upper belt conveyor with the real-time transportation volume of the lower belt conveyor, if the preset load change threshold is exceeded, the speed value of each motor of the lower belt conveyor is adjusted and set according to the real-time transportation volume of the upper belt conveyor; The formulas for calculating the real-time transport volume and motor speed of belt conveyors at all levels are as follows: MgV=πD ² n/i ² (I/I _e T _me - T _s )/ (μCOSθ+SINθ) /L; Among them, Mgv is the real-time transportation volume of the belt conveyor, D is the diameter of the driving drum of the motor, n is the motor speed, i is the transmission ratio of the belt conveyor, I is the running current of the motor, I _e is the rated current of the motor, and T _me is the rated mechanical rotation speed of the motor output. Moment, T _s is the no-load torque of the belt conveyor, θ is the inclination angle of the belt conveyor, μ is the friction coefficient between the belt and the roller, and L is the length of the belt conveyor. 2. belt conveyor load prediction control method as claimed in claim 1, is characterized in that, described lower belt conveyor delays for a period of time and adjusts and sets the rotational speed value of each motor of lower grade belt conveyor, and the delay time calculation formula is as follows: t =L/(πDn/i), where t is the delay time, L is the length of the upper belt conveyor, D is the diameter of the driving drum of the upper belt conveyor motor, n is the speed of the upper belt conveyor motor, and i is the transmission ratio of the upper belt conveyor. 3. The load prediction control method for belt conveyors according to claim 1 or 2, wherein the upper belt conveyor directly transmits the real-time transportation volume of the upper belt conveyor to the lower belt conveyor through communication. 4. The belt conveyor load predictive control method as claimed in claim 1 or 2, characterized in that, the upper belt conveyor transmits the motor operating current and the motor speed of the upper belt conveyor to the lower belt conveyor through communication, and the lower belt conveyor Calculate the real-time transportation volume of the upper belt conveyor. 5. The load predictive control method for belt conveyors according to claim 1 or 2, characterized in that, the lower belt conveyor adopts a frequency conversion method to adjust the motor speed.

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