CN101173868A - Material position detecting method and device based on vibration signal of ball grinder rotating cylinder body - Google Patents

Abstract

The invention discloses a material level detecting method and a detection device based on vibration signal of ball mill rotary drum. The invention is characterized in that the method comprises the following procedures: (A) installing a vibration acceleration transducer on the ball mill rotary drum; (B) setting data collection parameters, and calculating a circumferential angle L when the transducer collects a group of data measuring points; (C) determining the circumferential area of the transducer for data collection, and acquiring the relation between the maximum impact point of a steel ball on the ball mill rotary drum and the level; (D) acquiring the impact vibration signal between the steel ball in the drum and the coal, steel ball and steel ball, as well as the steel ball and the drum wall; (E) determining the maximum impact point of the steel ball on the drum; (F) calculating the level value of the ball mill in the state. The detection device comprises a ball mill drum and a vibration accelerator arranged on the ball mill drum. The invention has the advantages of real-time and accurate level detection, and avoidance of influence on measurement results caused by changes of category of coal, water content of coal, particle size of coal and other factors.

Description

Material level detection method and pick-up unit thereof based on bowl mill rotary barrel vibration signal

Technical field

The present invention relates to the detection method of material level in a kind of balling drum, relate in particular to a kind of material level detection method and pick-up unit thereof based on bowl mill rotary barrel vibration signal.

Background technology

Barrel-shaped steel ball mill is a kind of common and typical abrasive dust equipment, and it obtains using the most widely in the mineral aggregate of industries such as metallic ore and nonmetalliferous ore ore dressing plant, building materials, fire resistive material, cement, coal, chemical industry, electric power, light industry and metallurgy is pulverized.In the numerous fuel-burning power plant of China, cartridge type low speed bowl mill is an equipment commonly used in the pulverized coal preparation system, and its effect is with the supply boiler combustion with coal cinder drying, fragmentation of certain size and the coal dust that grinds into certain fineness.For middle bin system, the power consumption of bowl mill is up to about 20% of station service.

In the balling drum the accurate measurement of material level be ensure bowl mill automatically, the crucial and basic place of safety, efficient operation, in recent years, each state all strengthens the research to the material level Automatic Measurement Technique, making every effort to can be in time, stable and detect material level parameter in the cylinder more exactly, thereby realize the Automatic Optimal operation of bowl mill.In the commercial production at present adopt following several detection methods at home and abroad more:

(1) differential pressure method, the differential pressure signal that utilizes balling drum to import and export is measured the material level in the cylinder indirectly, but because differential pressure signal is subjected to all multifactor influences such as material level, ventilation, outlet temperature and bowl mill structure simultaneously, be difficult to set up the function of differential pressure and material level, so measuring accuracy is very limited and unstable.

(2) net horsepower method utilizes the rule of conversion between power and the material level to detect material level, and it is subjected to the influence of surrounding environment smaller, and the factor of power is many, sensitivity is not high but influence, and especially is difficult to judge when power reduces.

(3) Strain Method is installed in the middle part of bowl mill housing STRESS VARIATION maximum to the piezoelectric stress sensor, and the variation that the pressure by measuring the cylindrical shell top and the tension force of cylindrical shell bottom calculate general pressure is estimated material level in the bowl mill with this.But when measuring for a long time, because some limitation of piezoelectric stress sensor itself bring very big error can for the measurement of material level.

(4) air pressure drop level gauging method, the two ends symmetric arrangement of mill has pressure tube, low-pressure air continuous, pressure stability flows into pressure tube and build-up pressure in pipe, when " flooding " material level pressure tube of coal dust part is popped one's head in, the pipe internal pressure raises, produce pressure reduction with prover pipe pressure, this pressure difference signal just can reflect material level.This method has obtained application in the bowl mill that goes with each other all the time, but exist also in Dan Jindan goes out the application of bowl mill how high and low position pressure tube probe is prevented pounding, the determining and a lot of difficult problems such as fixing of air pressure drop meter installation site.

(5) ultrasound examination material level method, this method are to utilize ultrasound wave to penetrate steel plate and certain thickness coal seam, reflect the thickness in coal seam according to the characteristic of acknowledge(ment) signal.But because ultrasound wave is absorbed easily and decays, influenced by environment such as temperature, steam etc., simultaneously it to require the above space of material level be clean, yet in cylinder, be covered with dust, reflection wave is seriously disturbed, can not accurately detect material level.

(6) weight method detects material level by erection stress meter formula LOAD CELLS under the balling drum bearing, and this method can obtain good effect under the general industrial environment, but can't guarantee long reliably working under rugged surroundings.

(7) noise method according to adopting the monitoring noise to differentiate material level, still, because the variation (the especially variation of moisture) of coal can cause very big sound signal error, causes level gauging very big deviation to occur in the actual motion operation.On the other hand, the various mechanical faults of bowl mill all can produce certain influence to sound signal as the vibration of machineries such as tile kilning, big axle fracture, bolt fracture, reductor driver, blimp problem, nearby device noise etc.

(8) vibratory drilling method, sensor installation picks up vibration signal on bowl mill antero posterior axis bearing, measure material level by these data are handled and analyzed, this method can't distinguish all whether bowl mill mechanical fault information is arranged, and also can't distinguish different coals, change of soil water content.

Because bowl mill is a multi-variable system that has non-linear, large time delay, strong coupling and have multiple uncertain disturbances, is adding balling drum internal operating environment complexity, causes present material level to detect and also lack reliable and effective means.The factor that influences the bowl mill coal-grinding in addition is a lot, belongs to having of coal charge aspect: ore grindability, feeding granularity etc.; Belong to having of bowl mill configuration aspects: bowl mill specification, pattern, liner plate shape etc.; What belong to operating aspect has drum's speed of rotation, adds ball system and ratio of grinding media to material.These factors itself interact again, make above-described detection method also have a lot of problems, are difficult to the accurately interior material level of reflection balling drum; Cause in the actual motion of bowl mill for fear of the chute blockage phenomenon occurring, make it often run on extremely uneconomical district, the powder process power consumption is higher; Simultaneously also cause the bowl mill automatic control system to be difficult to come into operation reliably and with long-term, material level still relies on manually-operated.

Summary of the invention

Goal of the invention of the present invention provides a kind of material level detection method and the pick-up unit thereof based on bowl mill rotary barrel vibration signal that can measure material level in the balling drum in real time, exactly, and this method can effectively overcome the water cut of coal, coal, numerous factors such as granularity of coal detect the influence that brings to material level.

The present invention adopts following technical scheme:

A kind of material level detection method based on bowl mill rotary barrel vibration signal, this method may further comprise the steps:

A) vibration acceleration sensor is installed on balling drum,

B) determine the sampling parameter of sensor data acquisition, this parameter comprises sample frequency and sampling number, and gathers the circumferential angle L that one group of data measuring point turns over according to sample frequency and sampling number calculating sensor,

C) determine the circumferential zones of sensor data acquisition on cylindrical shell: the theoretical Point Of Maximal Impulse that at first calculates steel ball in the balling drum, by the material level calibration experiment, and with the steel ball Point Of Maximal Impulse of Theoretical Calculation as the experiment instruction foundation, determine the circumferential zones of the actual Point Of Maximal Impulse of steel ball on the cylindrical shell, and obtain the Point Of Maximal Impulse of steel ball on the cylindrical shell and the relation between the material level simultaneously

Each initial circumferential position when D) circumferential zones of circumferential angle that turns over according to one group of data measuring point of sensor acquisition and data acquisition is determined sensor data acquisition, when bowl mill moves, by sensor impact shock signal between steel ball and coal, steel ball and steel ball and steel ball and the barrel in each circumferential position pickup roller, and this impact shock signal is saved in the collecting computer

E) the impact shock data of analyzing and relatively gathering on the rotary barrel are determined the Point Of Maximal Impulse of steel ball on the cylindrical shell,

F) calculate material level value under this state of bowl mill according to the corresponding relation of Point Of Maximal Impulse and material level.

A kind of material-level detecting device based on bowl mill rotary barrel vibration signal comprises ball mill barrel, is provided with vibration acceleration sensor on ball mill barrel.

Compared with prior art, the present invention has the following advantages:

1, the present invention utilizes the Point Of Maximal Impulse of steel ball on interior material level of cylinder and the cylindrical shell to exist the principle of corresponding relation, by analyzing Point Of Maximal Impulse that circumferential position vibration data on the cylindrical shell obtains steel ball realizing measuring material level, its measurement result is not subjected to the influence of numerous factors such as change of granularity of water cut, the coal of coal, coal.

2, because sensor is to be directly installed on the rotary barrel, significantly reduced the pipeline that crash shock impacts between the interior steel ball of cylinder and coal, steel ball and steel ball and steel ball and the barrel, adding reasons such as the quality of upper shell own is big, therefore be installed in data that bowl mill antero posterior axis bearing measuring point collects and more can reflect the impact events between the steel ball and coal cinder, steel ball and steel ball and steel ball and barrel in the cylinder sensitively than traditional, this vibration data more can reflect material level information exactly.

3, measurement data of the present invention accurately and reliably.Because the ball mill barrel stabilization of speed, each circumferential angular vibration data fluctuations is very little on the cylindrical shell, makes that the level gauging error is little, and is reliable and stable.

4, the present invention is different with noise signal detection material level method, and measurement result of the present invention is not subjected to the influence of surrounding environment.

5, the present invention is widely used.The present invention not only is adapted to the bowl mill unit in the thermal power plant, equally also is applicable at the bowl mill unit of industries such as ore dressing, building materials, cement, coal, chemical industry, light industry and metallurgy, effectively improves its performance driving economy and reliability.

Description of drawings

Fig. 1 is the synoptic diagram of pick-up unit among the present invention, and the left end of figure middle cylinder body is a coal-feeding end, and right-hand member is a coal exit.

Fig. 2 is motion locus of steel ball synoptic diagram, wherein A point and A in the balling drum ₁Point is respectively move in a circle a separation point when finishing of outermost layer and innermost layer steel ball in the cylinder, B and B ₁Point is respectively the contact point when outermost layer and innermost layer steel ball are done the cast and decline movement end cylinder in; The α angle is the disengaging angle of outermost layer steel ball, and β is the Luo Huijiao of outermost layer steel ball.

Fig. 3 is the graph of a relation between material level and the maximum impact angle.

Fig. 4 be on the cylinder during vibration acceleration sensor data acquisition circumferential position represent synoptic diagram, bowl mill is for being rotated counterclockwise, the starting point of circumferential position when the A point is gathered for measuring point in the drawings, calculate the size of circumferential position in the counterclockwise direction from the A point, as the B point then is circumferential 90 °, the C point is circumferential 180 °, and the D point is circumferential 310 °.

The cylinder impact shock data time-domain diagram of Fig. 5 embodiment of the invention.

The cylinder impact shock data spectrum figure of Fig. 6 embodiment of the invention.

Fig. 7 is the variation rule curve of each circumferential position and impact shock under a certain material level.

Embodiment

A kind of material level detection method based on bowl mill rotary barrel vibration signal, this method may further comprise the steps:

A) vibration acceleration sensor is installed on balling drum, in the present embodiment, this vibration acceleration sensor is positioned at the middle part of balling drum,

B) determine the sampling parameter of sensor data acquisition, this parameter comprises sample frequency and sampling number, and gathers the circumferential angle L that one group of data measuring point turns over according to sample frequency and sampling number calculating sensor,

C) determine the circumferential zones of sensor data acquisition on cylindrical shell: the theoretical Point Of Maximal Impulse that at first calculates steel ball in the balling drum, by the material level calibration experiment, and with the steel ball Point Of Maximal Impulse of Theoretical Calculation as the experiment instruction foundation, determine the circumferential zones of the actual Point Of Maximal Impulse of steel ball on the cylindrical shell, and obtain the Point Of Maximal Impulse of steel ball on the cylindrical shell and the relation between the material level simultaneously

Each initial circumferential position when D) circumferential zones of circumferential angle that turns over according to one group of data measuring point of sensor acquisition and data acquisition is determined sensor data acquisition, when bowl mill moves, by sensor impact shock signal between steel ball and coal, steel ball and steel ball and steel ball and the barrel in each circumferential position pickup roller, and this impact shock signal is saved in the collecting computer

E) the impact shock data of analyzing and relatively gathering on the rotary barrel are determined the Point Of Maximal Impulse of steel ball on the cylindrical shell,

F) calculate material level value under this state of bowl mill according to the corresponding relation of Point Of Maximal Impulse and material level.

The definite process of step B in this method is as follows:

B1) sample frequency f _sDetermine to depend on that steel ball is to the frequency of impact of coal in the cylinder, this frequency of impact concentrates in high frequency 2000Hz～15000Hz scope, in order not lose useful information and to solve the frequency aliasing problem, the computation rule of sample frequency is in engineering:

f _s＝(2.56～4)f _m (1)

F in the formula (1) _mBe the frequency of steel ball to the HI high impact frequency content of coal, in the present embodiment, f _m=15000Hz, so sample frequency f _sScope be 40000Hz～60000Hz,

B2) when sample frequency one timing, the too small meeting of sampling number N makes frequency resolution Δ f excessive, causes losing or distorting the information of original signal like this; The too high meeting of sampling number N simultaneously increases Computer Storage amount and calculated amount greatly, according to the needs of sample frequency and calculating, and sampling number N=4096 point,

B3) gather the circumferential angle that one group of data measuring point turns over cylinder according to sample frequency and sampling number calculating sensor,

The sampling length T of one group of data of sensor acquisition is:

T＝N/f _s (2)

Balling drum rotates used time t of a week:

t＝60/n (3)

N is the rotating speed of bowl mill in the formula (3), the r/min of unit,

Can get one group of data measuring point of sensor acquisition by formula (2), (3) with the circumferential angle L that cylinder turns over is:

$L=\frac{T}{t}\×360=\frac{6\mathrm{Nn}}{f_s}---\left(4\right)$

L rounded obtain l, unit is degree.

The definite process of step C in this method is as follows:

C1) calculate the theoretical Point Of Maximal Impulse of steel ball in the cylinder: this point is finished the contact point that falls back and barrel behind the circular motion along para-curve for outermost layer steel ball in the cylinder with cylindrical shell, this point is called the some B of falling back of steel ball, center of circle O with the cylindrical shell xsect is that initial point is set up coordinate system XOY, some B that falls back this moment are positioned at third quadrant, the angle of line segment OB and X-axis negative direction is called the angle β that falls back, wherein the outermost layer steel ball is exactly one deck steel ball of pressing close to barrel most

When bowl mill moves, see that from coal-feeding end bowl mill is for rotating counterclockwise, the outermost layer steel ball moves in a circle with barrel at first, the radius of circular motion is identical with radius roller, be R, when the outermost layer steel ball with cylindrical shell when circular path runs to dispersal point A, the centrifugal force that acts on the steel ball is identical with the radial component of steel ball gravity, this moment the outermost layer steel ball cross the A point then steel ball leave barrel, dish out and move from the horizontal by an angle with initial velocity v along parabolic path, fall the some B that falls back on the barrel at last, the stress balance when a certain steel ball of outermost layer arrives dispersal point A is:

$\frac{m{v}^2}{R}=\mathrm{mg}\cos \mathrm{\α}---\left(5\right)$

In the formula (5):

The quality of m-steel ball

G-acceleration of gravity, its value is 9.8m/s ²

The disengaging angle of α-steel ball is the angle of line segment OA and Y-axis positive dirction in coordinate system XOY

The computation process of v is as follows in the formula (5):

In the formula (6):

The angular velocity of ω-bowl mill

The rotating speed of n-bowl mill, the r/min of unit

The disengaging angle α that contact formula (5), (6) can get steel ball is:

$\mathrm{\&alpha;}=\arccos \frac{n^2\mathrm{<figure-callout\; id="90"\; label="R"\; filenames="S2007101314152E00031.png"\; state="\{\{state\}\}">R</figure-callout>}}{900}---\left(7\right)$

Can determine the position of dispersal point A in coordinate system XOY by breaking away from angle α, the coordinate that A is ordered is:

X _A＝Rsina (8)

Y _A＝Rcosa (9)

Getting dispersal point A is initial point, sets up coordinate system XAY, and then steel ball along the equation of locus of circular motion is:

(x+Rsinα) ²+(y+Rcosα) ²＝R ² (10)

Steel ball is dished out with linear velocity v from dispersal point A, and the horizontal range of projectile motion correspondence and vertical range equation are respectively in coordinate system XAY:

x＝-(vcosα)t (11)

y＝(vsinα)t-1/2gt ² (12)

By formula (11), (12) steel ball along the equation of motion of parabolic path is:

$y=-\mathrm{xtg\&alpha;}-\frac{{\mathrm{<figure-callout\; id="2"\; label="x"\; filenames="S2007101314152E00031.png"\; state="\{\{state\}\}">x</figure-callout>}}^2}{2\mathrm{Rco}{s}^3\mathrm{\&alpha;}}---\left(13\right)$

Fall the back position of some B is exactly the intersection point of two movement locus, and simultaneous formula (10) and (13) can solve the coordinate that B is ordered among the coordinate system XAY and be:

x _B＝-4Rsinαcos ²α (14)

y _B＝-4Rsin ²αcosα (15)

Represent, formula (14), (15) to be rewritten as the coordinate of drop point B for the XOY coordinate system of initial point in order to 0 according to moving axle gauge then:

x _B＝-4Rsinαcos ²α+R?sinα (16)

y _B＝-4Rsin ²αcosα+R?cosα (17)

The angle β that falls back is:

$\sin \mathrm{\&beta;}=\frac{\left|y_B\right|}{R}=4{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="S2007101314152E00031.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\mathrm{\&alpha;}\cos \mathrm{\&alpha;}-\cos \mathrm{\&alpha;}=\sin (3\mathrm{\&alpha;}-\frac{\mathrm{\&pi;}}{2})---\left(18\right)$

So $\mathrm{\&beta;}=3\mathrm{\&alpha;}-\frac{\mathrm{\&pi;}}{2}---\left(19\right)$

By formula (16), (17), (1 9) can learn some B that falls back, the angle β that falls back all can obtain by breaking away from angle α,

C2) slack tank calibration experiment: when bowl mill is in normal operating conditions, stopped coal supply 8～12 minutes, mill is found time, this time is 10 minutes in the present embodiment, make that material level is 0%, and continue to stop coal supply bowl mill is run well that this moment, bowl mill was in the slack tank state always, under this state, gather the impact shock signal

Because the actual Point Of Maximal Impulse position that can't learn steel ball on this state lower shell, therefore with the steel ball Point Of Maximal Impulse of Theoretical Calculation for instructing foundation, on cylindrical shell this position circumferentially ± the 3l regional extent in image data, wherein l is that L rounds and obtains, and L 〉=l, the number of degrees scope of this regional extent in coordinate system XOY is 180 °+β-3l～180 °+β+3l, the circumferential angle that one group of data measuring point of sensor acquisition turns over cylindrical shell is L, therefore only need at six circumferential positions at this circumferential zones inner sensor: 180 °+β-3l, 180 °+β-2l, 180 °+β-l, 180 °+β, 180 °+β+l, 180 °+β+2l place image data, and a data that collect is saved in the collecting computer

Cross the effective value of 1 ° of vibration data that collects according to the impact shock calculated signals that collects at this circumferential zones measuring point revolution in this zone, computation process is as follows:

C21) because sampling number N=4096 point during data acquisition, the circumferential angle that one group of data measuring point of sensor acquisition turns over cylindrical shell is L, so the measuring point revolution is crossed 1 ° of vibration data number n that collects and is:

$n=\left[\frac{N}{L}\right]---\left(20\right)$

C22) existing is that example is presented in the whole zone of 180 °+β-3l～180 °+β+3l to calculate measuring point at the vibration data effective value that 180 °+β-3l of circumferential position turns over 1 ° of collection, and the measuring point revolution is crossed the computing method of 1 ° of vibration data effective value that collects; Because sampling number is the N=4096 point, so sensor comprises 4096 vibration acceleration data x in one group of data that circumferentially 180 °+β of reference position-3l gathers _i, i=1 wherein, 2 ..., N, again since the measuring point revolution to cross 1 ° of vibration data number that collects be n, so measuring point is x at the vibration data that 180 °+β-3l of circumferential position turns over 1 ° of collection _i, i=1 wherein, 2 ..., n, in like manner measuring point is x at 180 ° of cylindrical shell circumferential positions+β-3l+1 ° of vibration data that turns over 1 ° of collection _i, i=n+1 wherein, n+2 ..., 2n, measuring point turn over 1 ° of collection at 180 °+β-3l of circumferential position the computing formula of vibration data effective value is as follows:

$X=n\sqrt{\frac{1}{N}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{x}_i^2}---\left(21\right)$

The vibration effective value of this effective value as 180 °+β-3l of circumferential position, in like manner can try to achieve cylindrical shell vibration effective value on other circumferential positions in the circumferential zones of 180 °+β-3l～180 °+β+3l, and differ 1 ° between adjacent two circumferential positions,

The vibration effective value of cylindrical shell each circumferential position in 180 °+β-3l～180 °+β+3l circumferential zones relatively, the circumferential position S of maximum vibration effective value correspondence ₀As the actual Point Of Maximal Impulse of steel ball on the slack tank state lower shell,

C3) canful calibration experiment: after slack tank is demarcated, start feeder the coal charge of 20% material level correspondence is transported in the balling drum, only advance coal this moment and do not produce coal, keep bowl mill normally to move, stable up to vibration signal, under this state, gather the impact shock signal,

The mode of vibration acceleration data acquisition on cylindrical shell is identical with the slack tank state, and the circumferential zones of cylindrical shell collection is 180 °+β-3l～180 °+β+3l; Calculate the vibration effective value of each circumferential position of gathering 1 ° at every interval in the circumferential zones according to identical method, obtain the actual Point Of Maximal Impulse S of steel ball on the canful state lower shell by comparative analysis ₁,

C4) the Point Of Maximal Impulse position owing to steel ball on the slack tank state cylindrical shell is S ₀, the Point Of Maximal Impulse position of steel ball is S on the canful state cylindrical shell ₁, and S ₀＞S ₁, in order to ensure that the circumferential zones of data acquisition is applicable to various running statuses on the cylindrical shell, and the circumferential zones that reduces data acquisition as much as possible shortens data acquisition time, reduces calculated amount, and the circumferential pickup area of data is decided to be S ₁-l～S ₀+ l,

C5) the Point Of Maximal Impulse position S by steel ball on the slack tank state cylindrical shell ₀Point Of Maximal Impulse position S with steel ball on the canful state cylindrical shell ₁, determine on the cylindrical shell relation between the steel ball Point Of Maximal Impulse on the material level and cylindrical shell.

The definite process of step D in this method is as follows:

D1) zone of sensor data acquisition on cylindrical shell is S ₁-l～S ₀+ l, the circumferential angle that turns over cylindrical shell according to one group of data measuring point of sensor acquisition is L, can obtain each the circumferential reference position in this area data collection,

D2) when bowl mill moves,, and this impact shock signal is saved in the collecting computer by vibration acceleration sensor impact shock signal between steel ball and coal, steel ball and steel ball and steel ball and the barrel in each circumferential reference position pickup roller.

Definite process of the step e in this method is as follows:

E1) according to the method for the vibration effective value of each circumferential position of calculate gathering 1 ° at every interval in the circumferential zones in the material level calibration experiment, calculate circumferential zones S ₁-l～S ₀The vibration effective value of each circumferential position that the interior every interval of+l is 1 °,

E2) the vibration effective value of each circumferential position of comparison is the Point Of Maximal Impulse of the circumferential position of maximum vibration effective value correspondence as steel ball on this state lower shell.

A kind of material-level detecting device based on bowl mill rotary barrel vibration signal comprises the bowl mill rotary barrel, is provided with vibration acceleration sensor on the bowl mill rotary barrel.

In the present embodiment, the model of bowl mill is MG350/600, and the rotating speed of this model bowl mill is 17.57r/min, radius R=1.75m.Sample frequency f during data acquisition _s=40000Hz, sampling number N=4096 point is gathered one group of data measuring point according to rotating speed, sample frequency and the sampling number calculating of bowl mill and is turned over 10.54 ° with cylindrical shell.Can be regarded as to such an extent that the angle that comes off of outermost layer steel ball is a=53 ° according to the parameter of bowl mill, contact angle β=69 °, therefore the Point Of Maximal Impulse of steel ball should be arranged in 249 ° of positions of third quadrant of Fig. 2 XOY coordinate system on Theoretical Calculation; Obtain in slack tank (0% material level) calibration experiment that the Point Of Maximal Impulse of steel ball is arranged in 240 ° (at XOY coordinate systems) on the cylindrical shell, obtain in canful (20% material level) calibration experiment that the Point Of Maximal Impulse of steel ball is arranged in 230 ° (at XOY coordinate systems) on the cylindrical shell, therefore the circumferential zones of data acquisition is 220 °～250 ° (in the XOY coordinate systems) on the cylindrical shell, has also obtained the relation between material level and the steel ball Point Of Maximal Impulse simultaneously.Because the method for expressing of circumferential position is different with the XOY coordinate system when data acquisition, as shown in Figure 4, the starting point of circumferential angle when the A point is gathered for measuring point, calculate the size of circumferential angle in the counterclockwise direction from the A point, as the B point then is circumferential 90 °, the C point is circumferential 180 °, the D point is circumferential 310 °, therefore when bowl mill moves, vibration acceleration sensor is gathered the impact shock signal in 310 ° of-340 ° of scopes of circumferential zones, need sensor respectively at 310 °, 320 °, 330 ° three the circumferential position (D among Fig. 4, E, F 3 points) image data, the vibration data time domain of collection and frequency spectrum master drawing are respectively as shown in Figure 5 and Figure 6.Calculate the vibration effective value of gathering 30 circumferential positions (1 ° at interval) in the circumferential zones respectively, and the vibration effective value of each circumferential position of comparison, Fig. 7 is the graph of a relation between 30 circumferential positions and the vibration effective value, as can be seen from the figure, impact shock on the cylinder is to present to increase earlier the rule that afterwards reduces in circumferential 310 ° of-340 ° of zones, therefore 323 ° of impact shock maximums, locate promptly the Point Of Maximal Impulse of steel ball under the material level for this reason circumferential 323 ° (being 233 ° in the XOY coordinate system) on the cylindrical shell; According to the maximum impact angle that obtains,, can determine the size of material level in the cylinder according to the (see figure 3) that concerns between material level and the maximum impact angle.

Claims (6)

1. material level detection method based on bowl mill rotary barrel vibration signal is characterized in that this method may further comprise the steps:

A) vibration acceleration sensor is installed on balling drum,

B) determine the sampling parameter of sensor data acquisition, this parameter comprises sample frequency and sampling number, and gathers the circumferential angle L that one group of data measuring point turns over according to sample frequency and sampling number calculating sensor,

C) determine the circumferential zones of sensor data acquisition on cylindrical shell: the theoretical Point Of Maximal Impulse that at first calculates steel ball in the balling drum, by the material level calibration experiment, and with the steel ball Point Of Maximal Impulse of Theoretical Calculation as the experiment instruction foundation, determine the circumferential zones of the actual Point Of Maximal Impulse of steel ball on the cylindrical shell, and obtain the Point Of Maximal Impulse of steel ball on the cylindrical shell and the relation between the material level simultaneously

Each initial circumferential position when D) circumferential zones of circumferential angle that turns over according to one group of data measuring point of sensor acquisition and data acquisition is determined sensor data acquisition, when bowl mill moves, by sensor impact shock signal between steel ball and coal, steel ball and steel ball and steel ball and the barrel in each circumferential position pickup roller, and this impact shock signal is saved in the collecting computer

E) the impact shock data of analyzing and relatively gathering on the rotary barrel are determined the Point Of Maximal Impulse of steel ball on the cylindrical shell,

F) calculate material level value under this state of bowl mill according to the corresponding relation of Point Of Maximal Impulse and material level.

2. the material level detection method based on bowl mill rotary barrel vibration signal according to claim 1 is characterized in that the definite process of the step B in this method is as follows:

B1) sample frequency .f _sDetermine to depend on that steel ball is to the frequency of impact of coal in the cylinder, this frequency of impact concentrates in high frequency 2000Hz～15000Hz scope, in order not lose useful information and to solve the frequency aliasing problem, the computation rule of sample frequency is in engineering:

f _s＝(2.56～4)f _m (1)

F in the formula (1) _mBe the frequency of steel ball to the HI high impact frequency content of coal,

B2) when sample frequency one timing, the too small meeting of sampling number N makes frequency resolution Δ f excessive, causes losing or distorting the information of original signal like this; The too high meeting of sampling number N simultaneously increases Computer Storage amount and calculated amount greatly, determines sampling number N according to the needs of sample frequency and calculating,

B3) gather the circumferential angle that one group of data measuring point turns over cylinder according to sample frequency and sampling number calculating sensor,

The sampling length T of one group of data of sensor acquisition is:

T＝N/f _s (2)

Balling drum rotates used time t of a week:

f＝6/n (3)

N is the rotating speed of bowl mill in the formula (3), the r/min of unit,

Can get one group of data measuring point of sensor acquisition by formula (2), (3) with the circumferential angle L that cylinder turns over is:

$L=\frac{T}{t}\&times;360=\frac{6\mathrm{Nn}}{f_s}---\left(4\right)$

L rounded obtain l, unit is degree.

3. the material level detection method based on bowl mill rotary barrel vibration signal according to claim 1 is characterized in that the definite process of the step C in this method is as follows:

C1) calculate the theoretical Point Of Maximal Impulse of steel ball in the cylinder: this point is finished the contact point that falls back and barrel behind the circular motion along para-curve for outermost layer steel ball in the cylinder with cylindrical shell, this point is called the some B of falling back of steel ball, center of circle O with the cylindrical shell xsect is that initial point is set up coordinate system XOY, some B that falls back this moment are positioned at third quadrant, the angle of line segment OB and X-axis negative direction is called the angle β that falls back

When bowl mill moves, see that from coal-feeding end bowl mill is for rotating counterclockwise, the outermost layer steel ball moves in a circle with barrel at first, the radius of circular motion is identical with radius roller, be R, when the outermost layer steel ball with cylindrical shell when circular path runs to dispersal point A, the centrifugal force that acts on the steel ball is identical with the radial component of steel ball gravity, this moment the outermost layer steel ball cross the A point then steel ball leave barrel, dish out and move from the horizontal by an angle with initial velocity v along parabolic path, fall the some B that falls back on the barrel at last, the stress balance when a certain steel ball of outermost layer arrives dispersal point A is:

$\frac{m{v}^2}{R}=\mathrm{mg}\cos \mathrm{\&alpha;}---\left(5\right)$

In the formula (5):

The quality of m-steel ball

G-acceleration of gravity, its value is 9.8m/s ²

The disengaging angle of α-steel ball is the angle of line segment OA and Y-axis positive dirction in coordinate system XOY

The computation process of v is as follows in the formula (5):

In the formula (6):

The angular velocity of ω-bowl mill

The rotating speed of n-bowl mill, the r/min of unit

The disengaging angle α that contact formula (5), (6) can get steel ball is:

$\mathrm{\&alpha;}=\arccos \frac{n^{2}R}{900}---\left(7\right)$

Can determine the position of dispersal point A in coordinate system XOY by breaking away from angle α, the coordinate that A is ordered is:

X _A＝Rsina (8)

Y _A＝Rcosa (9)

Getting dispersal point A is initial point, sets up coordinate system XAY, and then steel ball along the equation of locus of circular motion is:

(x+Rsinα) ²+(y+Rcosα) ²＝R ² (10)

Steel ball is dished out with linear velocity v from dispersal point A, and the horizontal range of projectile motion correspondence and vertical range equation are respectively in coordinate system XAY:

x＝-(vcosα)t (11)

y＝(vsinα)t-1/2gt ² (12)

By formula (11), (12) steel ball along the equation of motion of parabolic path is:

$y=-\mathrm{xtg\&alpha;}-\frac{x^2}{2\mathrm{Rco}{s}^3\mathrm{\&alpha;}}---\left(13\right)$

Fall the back position of some B is exactly the intersection point of two movement locus, and simultaneous formula (10) and (13) can solve the coordinate that B is ordered among the coordinate system XAY and be:

x _B＝-4Rsinαcos ²α (14)

y _B＝-4Rsin ²cosα (15)

Represent, formula (14), (15) to be rewritten as the coordinate of drop point B for the XOY coordinate system of initial point in order to 0 according to moving axle gauge then:

x _B＝-4Rsinαcos ²α+Rsinα (16)

y _B＝-4Rsin ²αcosα+Rcosα (17)

The angle β that falls back is:

$\sin \mathrm{\&beta;}=\frac{\left|y_B\right|}{R}=4{\sin }^2\mathrm{\&alpha;}\cos \mathrm{\&alpha;}-\cos \mathrm{\&alpha;}=\sin (3\mathrm{\&alpha;}-\frac{\mathrm{\&pi;}}{2})---\left(18\right)$

So $\mathrm{\&beta;}=3\mathrm{\&alpha;}-\frac{\mathrm{\&pi;}}{2}---\left(19\right)$

By formula (16), (17), (19) can learn some B that falls back, the angle β that falls back all can obtain by breaking away from angle α,

C2) slack tank calibration experiment: when bowl mill is in normal operating conditions, stopped coal supply 8～12 minutes, mill is found time, make that material level is 0%, and continue to stop coal supply bowl mill is run well that this moment, bowl mill was in the slack tank state always, under this state, gather the impact shock signal

Because the actual Point Of Maximal Impulse position that can't learn steel ball on this state lower shell, therefore with the steel ball Point Of Maximal Impulse of Theoretical Calculation for instructing foundation, on cylindrical shell this position circumferentially ± the 3l regional extent in image data, wherein l is that L rounds and obtains, and L 〉=l, the number of degrees scope of this regional extent in coordinate system XOY is 180 °+β-3l～180 °+β+3l, the circumferential angle that one group of data measuring point of sensor acquisition turns over cylindrical shell is L, therefore only need at six circumferential positions at this circumferential zones inner sensor: 180 °+β-3l, 180 °+β-2l, 180 °+β-l, 180 °+β, 180 °+β+l, 180 °+β+2l place image data, and a data that collect is saved in the collecting computer

Cross the effective value of 1 ° of vibration data that collects according to the impact shock calculated signals that collects at this circumferential zones measuring point revolution in this zone, computation process is as follows:

The circumferential angle that one group of data measuring point of sampling number N and sensor acquisition turns over cylindrical shell during C21) according to data acquisition is L, so the measuring point revolution is crossed 1 ° of vibration data number n that collects and is:

$n=\left[\frac{N}{L}\right]---\left(20\right)$

C22) existing is that example is presented in the computing method that measuring point revolution in the whole zone of 180 °+β-3l～180 °+β+3l is crossed 1 ° of vibration data effective value that collects to calculate measuring point at the vibration data effective value that 180 °+β-3l of circumferential position turns over 1 ° of collection; Because sampling number is N, so sensor comprises N vibration acceleration data x in one group of data that circumferentially 180 °+β of reference position-3l gathers _i, i=1 wherein, 2 ..., N, again since the measuring point revolution to cross 1 ° of vibration data number that collects be n, so measuring point is x at the vibration data that 180 °+β-3l of circumferential position turns over 1 ° of collection _i, i=1 wherein, 2 ..., n, in like manner measuring point is x at 180 ° of cylindrical shell circumferential positions+β-3l+1 ° of vibration data that turns over 1 ° of collection _i, i=n+1 wherein, n+2 ..., 2n, measuring point turn over 1 ° of collection at 180 °+β-3l of circumferential position the computing formula of vibration data effective value is as follows:

$X=\sqrt{\frac{1}{N}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{x}_i^2}---\left(21\right)$

The vibration effective value of this effective value as 180 °+β-3l of circumferential position, in like manner can try to achieve cylindrical shell vibration effective value on other circumferential positions in the circumferential zones of 180 °+β-3l～180 °+β+3l, and differ 1 ° between adjacent two circumferential positions,

The vibration effective value of cylindrical shell each circumferential position in 180 °+β-3l～180 °+β+3l circumferential zones relatively, the circumferential position S of maximum vibration effective value correspondence ₀As the actual Point Of Maximal Impulse of steel ball on the slack tank state lower shell,

C3) canful calibration experiment: after slack tank is demarcated, start feeder the coal charge of 20% material level correspondence is transported in the balling drum, only advance coal this moment and do not produce coal, keep bowl mill normally to move, stable up to vibration signal, under this state, gather the impact shock signal,

The mode of vibration acceleration data acquisition on cylindrical shell is identical with the slack tank state, and the circumferential zones of cylindrical shell collection is 180 °+β-3l～180 °+β+3l; Calculate the vibration effective value of each circumferential position of gathering 1 ° at every interval in the circumferential zones according to identical method, obtain the actual Point Of Maximal Impulse S of steel ball on the canful state lower shell by comparative analysis ₁,

C4) the Point Of Maximal Impulse position owing to steel ball on the slack tank state cylindrical shell is S ₀, the Point Of Maximal Impulse position of steel ball is S on the canful state cylindrical shell ₁, and S ₀＞S ₁, in order to ensure that the circumferential zones of data acquisition is applicable to various running statuses on the cylindrical shell, and the circumferential zones that reduces data acquisition as much as possible shortens data acquisition time, reduces calculated amount, and the circumferential pickup area of data is decided to be S ₁-l～S ₀+ l,

C5) the Point Of Maximal Impulse position S by steel ball on the slack tank state cylindrical shell ₀Point Of Maximal Impulse position S with steel ball on the canful state cylindrical shell ₁, determine on the cylindrical shell relation between the steel ball Point Of Maximal Impulse on the material level and cylindrical shell.

4. the material level detection method based on bowl mill rotary barrel vibration signal according to claim 1 is characterized in that the definite process of the step D in this method is as follows:

D1) zone of sensor data acquisition on cylindrical shell is S ₁-l～S ₀+ l, the circumferential angle that turns over cylindrical shell according to one group of data measuring point of sensor acquisition is L, can obtain each the circumferential reference position in this area data collection,

D2) when bowl mill moves,, and this impact shock signal is saved in the collecting computer by vibration acceleration sensor impact shock signal between steel ball and coal, steel ball and steel ball and steel ball and the barrel in each circumferential reference position pickup roller.

5. the material level detection method based on bowl mill rotary barrel vibration signal according to claim 1 is characterized in that definite process of the step e in this method is as follows:

E1) according to the method for the vibration effective value of each circumferential position of calculate gathering 1 ° at every interval in the circumferential zones in the material level calibration experiment, calculate circumferential zones S ₁-l～S ₀The vibration effective value of each circumferential position that the interior every interval of+l is 1 °,

E2) the vibration effective value of each circumferential position of comparison is the Point Of Maximal Impulse of the circumferential position of maximum vibration effective value correspondence as steel ball on this state lower shell.

6. the material-level detecting device based on bowl mill rotary barrel vibration signal comprises ball mill barrel, it is characterized in that being provided with vibration acceleration sensor on the excircle of ball mill barrel.

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