CN101452278A - On-line dynamic stiffness test method for hydraulic press down system for hot-rolled finishing mill AGC - Google Patents

Abstract

The invention discloses an on-line dynamic rigidity testing method for an AGC hydraulic pressure down system of a hot rolling finishing mill. The method comprises the following steps: firstly, a rolling force signal F(t) and an oil cylinder displacement signal S(t) of the hot rolling finishing mill are synchronously sampled; the acquired signals are subjected to physical quantity conversion; a voltage signal is converted into engineering quantity and are shown by Newton (N) and micron (mu m) respectively; the engineering quantity is subjected to Fast Fourier Transform (FFT), and is converted into amplitude spectrum for calculation so as to obtain rolling force F(Omega) and oil cylinder displacement S(Omega); dynamic rigidity G(Omega) is equal to F (Omega)/S(Omega) and is calculated; and a BODE graph tool is adopted to analyze amplitude-frequency property of a transfer function so as to analyze the dynamic property of the system. The method can rapidly analyze fault cause, carry out fault diagnosis and achieve the aims of reducing unplanned equipment downtime and improving production efficiency.

Description

The online dynamic stiffness test method of hydraulic press down system for hot-rolled finishing mill AGC

Technical field

The present invention relates to the dynamic characteristic test and the analytical approach of on-line hydraulic equipment, relate in particular to the method for the online dynamic rate test of metallurgy industry hydraulic press down system for hot-rolled finishing mill AGC.

Background technology

Rolling mill hydraulic AGC system is mechanical, electrical, liquid system ensemble, owing to adopt the electro-hydraulic servo technology, the hydraulic AGC dynamic responding speed is greatly improved, and the required time of THICKNESS CONTROL shortens greatly.Just because hydraulic AGC has quick response, so it has very big realistic meaning to the precision that improves finished strip in the THICKNESS CONTROL process.Because hydraulic AGC system is realized the dynamic adjustments of mill stiffness, can accomplish that so not only the actual gap values between rollers in the operation of rolling immobilizes, i.e. " permanent roll gap control ", thus guaranteed that actual rolling thickness is constant.The rolling mill hydraulic AGC dynamic perfromance is related to the significant problem of equipment operation, production safety, product quality, and is by the hot-rolled finishing mill AGC dynamic analysis, all significant to equipment condition monitoring, fault diagnosis and Performance Evaluation.

Summary of the invention

Technical matters to be solved by this invention provides the online dynamic stiffness test method of a kind of hydraulic press down system for hot-rolled finishing mill AGC.On-line testing reflection equipment running status by dynamic rate.

For solving the problems of the technologies described above, the online dynamic stiffness test method of hydraulic press down system for hot-rolled finishing mill AGC of the present invention, comprise milling train, roll and electrohydraulic servo-controlling system, the displacement transducer of surveying the oil cylinder displacement signal, the pressure transducer of surveying the roll-force signal and the thickness measurement sensor of measuring tape steel thickness are arranged in control system, it is formed three backfeed loops and forms closed-loop control system, described method comprises the steps

Step 1, by roll-force signal F (t) and the oil cylinder displacement signal S (t) of described electrohydraulic servo-controlling system at cycle time inter-sync sampling milling train;

Step 2: roll-force signal F (t) and the oil cylinder displacement signal S (t) that is gathered carried out the physical quantity conversion, voltage signal to measured displacement and pressure transducer is converted to quantities, rolling force F is with unit of force newton (N), and displacement S represents with long measure micron (μ m);

Step 3, the rolling strength changed and oil cylinder displacement are carried out fast Flourier (FFT) be transformed to amplitude spectrum and calculate, draw rolling force F (ω) and oil cylinder displacement S (ω);

Step 4, according to rolling force F (ω) and oil cylinder displacement S (ω), calculate dynamic rate G (ω)=F (ω)/S (ω);

Step 5, according to the dynamic rate that calculates, adopt the amplitude-frequency and the phase-frequency characteristic of BODE figure tool analysis transport function, record the hydraulic natural frequency ω of system by the amplitude versus frequency characte of dynamic rate _h, corner frequency 2 ω _hξ _hWith the hydraulic spring grease cup stiffness K _hEtc. systematic parameter, ξ wherein _hBe the hydraulic damping ratio, and these parameters and equipment failure are closely related, reflect the state of equipment by the on-line testing of dynamic rate.

Because the online dynamic stiffness test method of hydraulic press down system for hot-rolled finishing mill AGC of the present invention has adopted technique scheme, by analysis to original signal, adopt data computation method targetedly, operating mode and state that the precision of analyzing more can reflect system's reality have truly been improved, utilize the parameter of BODE figure dispatch control system analysis tool quantitative test AGC system, help further the AGC hydraulic control system being carried out fault diagnosis.But utilize the method express-analysis failure cause, reach minimizing equipment nonscheduled down time, enhance productivity.

Description of drawings

The present invention is described in further detail below in conjunction with drawings and embodiments:

Fig. 1 is a hot-rolled finishing mill AGC control system principle of work block scheme,

Fig. 2 is a hot-rolled finishing mill AGC control system open-loop transfer function calcspar,

Fig. 3 is hot-rolled finishing mill AGC control system dynamic rate BODE figure,

Fig. 4 is the online dynamic stiffness test method process flow diagram of this hydraulic press down system for hot-rolled finishing mill AGC.

Embodiment

As shown in Figure 4, the online dynamic stiffness test method of hydraulic press down system for hot-rolled finishing mill AGC of the present invention, comprise milling train, roll and electrohydraulic servo-controlling system, displacement transducer, the pressure transducer of surveying the roll-force signal of surveying the oil cylinder displacement signal and the roll gap sensor of surveying the roll gap signal are arranged in control system, it is formed three backfeed loops and forms closed-loop control system, described method comprises the steps

Step 1, by roll-force signal F (t) and the oil cylinder displacement signal S (t) of described electrohydraulic servo-controlling system at cycle time inter-sync sampling milling train;

Step 2: roll-force signal F (t) and the oil cylinder displacement signal S (t) that is gathered carried out the physical quantity conversion, voltage signal to measured displacement and pressure transducer is converted to quantities, rolling force F is with unit of force newton (N), and displacement S represents with long measure micron (μ m);

Step 3, the rolling strength changed and oil cylinder displacement are carried out fast Flourier (FFT) be transformed to amplitude spectrum and calculate, draw rolling force F (ω) and oil cylinder displacement S (ω);

Step 4, according to rolling force F (ω) and oil cylinder displacement S (ω), calculate dynamic rate G (ω)=F (ω)/S (ω);

Step 5, according to the dynamic rate that calculates, adopt the amplitude-frequency and the phase-frequency characteristic of BODE figure tool analysis transport function, record the hydraulic natural frequency ω of system by the amplitude versus frequency characte of dynamic rate _h, corner frequency 2 ω _hξ _hWith the hydraulic spring grease cup stiffness K _hEtc. systematic parameter, ξ wherein _hBe the hydraulic damping ratio, and these parameters and equipment failure are closely related, reflect the state of equipment by the on-line testing of dynamic rate.

The hot-rolled finishing mill AGC press down system generally is made up of the multimachine frame, and many frames are formed a complete control system in the rolling process, but every frame control principle and working method unanimity promptly adopt electrohydraulic servo valve directly to control roll gap.Its principle of work: on the memorial archway of milling train fore side and transmission side, a depress oil cylinder is arranged respectively, both sides respectively have one not only be related, but also the control system that can work alone.In system, form three backfeed loops and form closed-loop control system by surveying oil cylinder displacement signal, survey roll-force signal and thickness measuring signal etc.Fig. 1 is a hot-rolled finishing mill AGC control system functional-block diagram.

Derive according to classical kybernetics, the hot-rolled finishing mill AGC control principle can be reduced to system's open-loop transfer function block scheme, as shown in Figure 2.The expression formula of its transport function is:

$Y=\frac{\frac{K_q}{A_a}{X}_v-\frac{K_{\mathrm{ce}}}{A_a^2}(\frac{{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="A200710171983E00083.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}{{\mathrm{\&beta;}}_e\&CenterDot;K_{\mathrm{ce}}}s+1)F}{[(1+\frac{K_L}{K_h})s+\frac{K_{\mathrm{ce}}\&CenterDot;K_L}{A_a^2}]\&CenterDot;(\frac{s^2}{{\mathrm{\&omega;}}_0^2}+\frac{{2\mathrm{\&xi;}}_0}{{\mathrm{\&omega;}}_0}s+1)}$

ω in the formula ₀-comprehensive natural frequency, ${\mathrm{\&omega;}}_0={\mathrm{\&omega;}}_{\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="A200710171983E00082.png"\; state="\{\{state\}\}">h</figure-callout>}}\sqrt{1+\frac{K_L}{K_h}};$

ξ ₀-comprehensive damping ratio, ${\mathrm{\&xi;}}_0=\frac{1}{2{\mathrm{\&omega;}}_0}[\frac{{\mathrm{\&beta;}}_e\&CenterDot;K_{\mathrm{ce}}}{V_0(1+\frac{K_L}{K_h})}+\frac{B_c}{M_T}]$

K _Ce-total flow-pressure coefficient, K _Ce=K _c+ C _i(m ⁵/ Ns);

K _h-hydraulic spring grease cup rigidity, $K_h=\frac{A_a^2\&CenterDot;{\mathrm{\&beta;}}_{\mathrm{<figure-callout\; id="0"\; label="e\; V"\; filenames="A200710171983E00083.png"\; state="\{\{state\}\}">e</figure-callout>}}}{V_{}};$

ω _h-hydraulic natural frequency, ${\mathrm{\&omega;}}_h=\sqrt{\frac{K_h}{M_T}}=\sqrt{\frac{A_a^2\&CenterDot;{\mathrm{\&beta;}}_{\mathrm{<figure-callout\; id="0"\; label="e\; V"\; filenames="A200710171983E00083.png"\; state="\{\{state\}\}">e</figure-callout>}}}{V_{}}};$

ξ _h-hydraulic damping ratio, ${\mathrm{\&xi;}}_h\&ap;\frac{K_{\mathrm{ce}}}{2A_a}\sqrt{\frac{{\mathrm{\&beta;}}_e\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="M\; T\; V"\; filenames="A200710171983E00083.png"\; state="\{\{state\}\}">M</figure-callout>}}_T}{V_{}}},$ $\frac{{2\mathrm{\&xi;}}_h}{{\mathrm{\&omega;}}_h}=\frac{K_{\mathrm{ce}}\&CenterDot;M_T}{A_a^2};$

M _T-milling train equivalent mass (kg);

B _c-milling train equivalent ratio of damping (Ns/m);

K _L-loading spring rigidity (N/m);

F-outer load force (N);

A _a-depress cylinder rodless cavity area (m ²);

C _i-depress cylinder internal leakage coefficient (m ⁵/ Ns);

V ₀-export to the original volume (m that depresses the cylinder piston from the servo-valve main valve ³);

Y-depress cylinder displacement (m);

β _e-fluid useful volume modulus (N/m ²).

Following formula learns that the displacement of depress oil cylinder (Y) is subjected to valve core of servo valve displacement (X _v) and roll-force (F) two parts function influence.Transport function can be expressed as respectively:

$\frac{Y_v}{X_v}=\frac{\frac{K_q}{A_a}}{[(1+\frac{K_L}{K_h})s+\frac{K_{\mathrm{ce}}\&CenterDot;K_L}{A_a^2}]\&CenterDot;(\frac{s^2}{{\mathrm{\&omega;}}_0^2}+\frac{{2\mathrm{\&xi;}}_0}{{\mathrm{\&omega;}}_0}s+1)}$

With $\frac{Y_F}{F}=\frac{-\frac{K_{ce}}{A_a^2}(\frac{{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="A200710171983E00083.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}{{\mathrm{\&beta;}}_e\&CenterDot;K_{\mathrm{ce}}}s+1)}{[(1+\frac{K_L}{K_h})s+\frac{K_{\mathrm{ce}}\&CenterDot;K_L}{A_a^2}]\&CenterDot;(\frac{s^2}{{\mathrm{\&omega;}}_0^2}+\frac{{2\mathrm{\&xi;}}_0}{{\mathrm{\&omega;}}_0}s+1)}$

Y＝Y _v+Y _F

Derive according to above-mentioned transport function, the dynamic perfromance of AGC position control is subjected to servo-valve and roll-force acting in conjunction; Roll-force can be seen the interference of system as when analyzing; Its dynamic analysis is made up of two parts, and one is the dynamic perfromance of AGC hydraulic part, has reflected the intrinsic characteristic of system itself; Two is dynamic flexibility, and its inverse is a dynamic rate, and its dynamic perfromance is presented under the roll-force interference effect, the positional precision characteristic of system.Dynamic rate has reflected position closed loop control system antijamming capability.The desirable closed loop rigidity characteristic of position control servo-drive system curve as shown in Figure 3.Otherwise if system has fault to take place, its dynamic rate characteristic also can change thereupon.

Each parameter of AGC screwdown gear hydraulic pressure mathematical model all is that the characteristic of system itself determines, can handle by emulation, signal analysis and numerical evaluation and try to achieve.But in theoretical derivation, owing to omitted a lot of links, and quite a few parameter can't accurately measure, so theoretical analysis and real system state differ bigger.Major technique characteristics of the present invention are the quantitiess that directly record the displacement of roll-force and AGC hydraulic cylinder with the on-the-spot test method, and analysis instruments such as employing FFT frequency-region signal disposal route and BODE figure, the duty and the fault analysis of online detection and judgement AGC system.

When actual online dynamic rate is tested, consider that AGC is a position closed loop control system, sting steel and throwing steel moment, the variation of rolling force F (t) reaches setting value fast from zero can be reduced to a step signal, utilizes this step change triggers to rolling force F (t) and AGC oil cylinder displacement S (t) synchronized sampling.Step signal has ergodic characteristic in frequency domain, F (t) and S (t) can obtain the transport function relation of dynamic rate in frequency domain by fast Flourier FFT conversion.In signal Processing and in analyzing, if adopt the power spectrum solution by diplomatic method, because the voltage signal of measurement is very little, hydraulic cylinder displacement and roll-force signal have only 10 ^-3～10 ^-2V, and energy becomes quadratic relationship with voltage again, and the value of power trends towards littler value.And the roll-force class signal subtracts characteristic according to step signal in the serious sorrow of frequency domain scope energy greater than 10Hz like step signal, therefore can produce the bigger error of calculation in the conversion of power spectrum and correlation operation, has influence on the analysis precision of dynamic rate.This method is converted to quantities with the voltage signal of being surveyed, roll-force (F) is with unit of force newton (N), displacement (S) is represented with long measure micron (μ m), fast Flourier (FFT) is transformed to amplitude spectrum and calculates, as shown in the formula expression, reduced the error of calculation effectively to the analysis to measure of dynamic rate.

G(ω)＝F(ω)/S(ω)

Because the steel of stinging of hot finisher arrives steady rolling transient process generally in the 0.2-0.3S time, is the precision that guarantees analysis, sample frequency is generally greater than 2KHz; Can analyze the amplitude-frequency and the phase-frequency characteristic of transport function with BODE figure instrument, AGC hydraulic pressure is depressed electro-hydraulic servo control and is typically designed to minimum phase system, but therefore with the amplitude versus frequency characte figure dynamic perfromance of analytic system just.

Can record the hydraulic natural frequency ω of system by the amplitude versus frequency characte of dynamic rate _h, corner frequency 2 ω _hξ _hWith the hydraulic spring grease cup stiffness K _hEtc. systematic parameter, and these parameters and equipment failure are closely-related.The state that therefore, can reflect equipment by the on-line testing of dynamic rate.

Claims (1)

1, the online dynamic stiffness test method of a kind of hydraulic press down system for hot-rolled finishing mill AGC, comprise milling train, roll and electrohydraulic servo-controlling system, the displacement transducer of surveying the oil cylinder displacement signal, the pressure transducer of surveying the roll-force signal and the thickness measurement sensor of measuring tape steel thickness are arranged in described control system, it is formed three backfeed loops and forms closed-loop control system, it is characterized in that: described method comprises the steps

Step 1, by roll-force signal F (t) and the oil cylinder displacement signal S (t) of described electrohydraulic servo-controlling system at cycle time inter-sync sampling milling train;

Step 2: roll-force signal F (t) and the oil cylinder displacement signal S (t) that is gathered carried out the physical quantity conversion, voltage signal to measured displacement and pressure transducer is converted to quantities, rolling force F is with unit of force newton (N), and displacement S represents with long measure micron (μ m);

Step 3, the rolling strength changed and oil cylinder displacement are carried out fast Flourier (FFT) be transformed to amplitude spectrum and calculate, draw rolling force F (ω) and oil cylinder displacement S (ω);

Step 4, according to rolling force F (ω) and oil cylinder displacement S (ω), calculate dynamic rate G (ω)=F (ω)/S (ω);

The dynamic rate that step 5, basis calculate, the amplitude-frequency and the phase-frequency characteristic of employing BODE figure tool analysis transport function; Record the hydraulic natural frequency ω of system by the amplitude versus frequency characte of dynamic rate _h, corner frequency 2 ω _hξ _h, ξ is compared in hydraulic damping _hWith the hydraulic spring grease cup stiffness K _hEtc. systematic parameter, and these parameters and equipment failure are closely related, reflect the state of equipment by the on-line testing of dynamic rate.

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