CN103611767B - Method for controlling position of sliding block of electro-hydraulic double-cylinder bending machine - Google Patents

Method for controlling position of sliding block of electro-hydraulic double-cylinder bending machine Download PDF

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Publication number
CN103611767B
CN103611767B CN201310692114.2A CN201310692114A CN103611767B CN 103611767 B CN103611767 B CN 103611767B CN 201310692114 A CN201310692114 A CN 201310692114A CN 103611767 B CN103611767 B CN 103611767B
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slide block
sliding block
action
point
control
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CN201310692114.2A
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Chinese (zh)
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CN103611767A (en
Inventor
冯日月
范中华
齐丹丹
张得礼
扶文树
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南京埃斯顿自动化股份有限公司
南京航空航天大学
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Abstract

The invention discloses a method for controlling the position of a sliding block of an electro-hydraulic double-cylinder bending machine. The method includes the steps of process improvement and pressure maintaining. When the sliding block does not reach an effective position point of an integral action, the magnitude of the action is adjusted through a proportional gain; when the sliding block moves to the effective position point of the integral action, the magnitude of the action is adjusted through an integral gain; when the sliding block continues to move to a switching position point of the integral action, the controlled quantity threshold value u(Y2) at the moment is recorded; when the sliding block continues to move downwards to a dead point, the integral action of a controller is reduced from the u(Y2) to 0. According to the method, in the whole operation process that the sliding block makes contact with a workpiece, is formed through compression moulding, is steered and leaves from the workpiece, the action of the controller continuously changes in a self-adaptive mode, a system is free from impact and sudden changes due to stressing, the motion trail of the sliding block is smooth, and moving parts are little in loss. Compared with a conventional method, the method has the advantages that the parameter action scope is enlarged, not only can steady accuracy of the system be guaranteed, but also responsiveness of the system is quickened, the sliding block can reach a target location more quickly, and machining efficiency is greatly improved.

Description

A kind of electric liquid twin-tub slider of bender position control method

Art

The invention belongs to bender technical field of automatic control, relate to electric liquid bender control technology, be specially a kind of electric liquid twin-tub slider of bender position control method.

Background technology

Electricity liquid twin-tub bender is widely used in sheet fabrication field, and the quality of sheet fabrication depends on the stability and accuracies that control slide position.

Electricity liquid twin-tub bender is by two proportional servo valve hydraulic control cylinders, hydraulic cylinder is equipped with displacement transducer for Real-Time Monitoring and feedback physical location, the signal that displacement transducer collects after filtering, controller is sent in the process such as signal conversion, controller includes special control software design, according to movement command signal and the feedback signal of setting, the control signal of system is tried to achieve after analytical calculation, give two proportional servo valves respectively, the opening flow of control ratio servo valve is carried out according to the power of the signal of telecommunication, thus control the position of two hydraulic cylinders, band movable slider runs up and down.

According to the requirement of technique, Forging Process comprises following step:

Under fast: controller forward opens proportional servo valve, opens prefill valve, and cylinder upper cavity oil is oil-filled, cavity of resorption is discharged fluid and is flowed to epicoele through differential circuit, and hydraulic cylinder relies on deadweight to decline fast, makes slide block run to speed change point fast from top dead-centre.

Work is entered: controller is after receiving speed change point signal, and close prefill valve, open proportional pressure valve, differential circuit remains unchanged, and the forward opening of proportional servo valve reduces, and makes slide block slow running to bottom dead centre.

Pressurize: after receiving bottom dead centre signal, controller passing ratio pressure valve is pressurizeed to systems stay, and differential circuit remains unchanged, and the position of slide block continues to be controlled by proportional servo valve, the output of system closing proportional servo valve, system reaches poised state and maintains a period of time.

Off-load: controller control ratio servo valve reverse opening, sets up buffer brake in oil circuit simultaneously.

Backhaul: proportional servo valve opening continues to increase, and under the effect of buffer brake, slide block fast movement returns top dead-centre, and after receiving top dead-centre signal, valve Close All, completes a bending work period.

Due to the hysteresis quality of hydraulic circuit, in system, there is tracking error always.Based on this kind of characteristic, current Forging Process controls extensively to adopt PI control method, namely control deviation is formed according to the tracking error between given position and physical location, the ratio (P) of deviation, integration (I) are formed controlled quentity controlled variable by linear combination, control controlled device, the control law of discretization is:

u ( k ) = K P e ( k ) + K I Σ j = 0 k e ( j ) (formula 1)

Wherein:

K is sampling sequence number, k=0,1,2

K pfor proportional gain;

K ifor storage gain;

E (k) is the deviate of kth time sampling instant input;

E (j) is the deviate of jth time sampling instant input;

The controlled quentity controlled variable that u (k) exports for kth time sampling instant controller.

The effect of each correction link of PI controller is as follows:

Proportional component: the deviation signal e (t) of proportional reflection control system, deviation is once produce, and controller produces control action immediately, to reduce deviation.The power of proportional action depends on proportional gain, and proportional gain is larger, and proportional action is stronger, otherwise then more weak.

Integral element: be mainly used in eliminate static difference, improve system without margin.The power of integral action depends on storage gain, and storage gain is larger, and integral action is stronger, otherwise then more weak.

In whole Forging Process, the proportional gain of system by adjustment PI controller and the size of storage gain, regulating the controlled quentity controlled variable exported, by changing the openings of sizes of proportional servo valve, realizing the position control to slide block.

Enter process for the work in bending technique, because it is contact workpiece and the committed step of bending and molding, therefore, the position control accuracy of this step is determined to the precision of whole Forging Process.The conventional PI controller of current employing, its proportional action can make slide block follow given trace operation; But when system is in positioning stage, owing to there is tracking error between slide block physical location and given position, therefore the accumulative action of integration causes system to export lasting increase, when slide block arrival impact point needs holding position motionless, the output of controller is not 0, and system cannot enter stable state.For this situation, existing two kinds of processing modes: the output of mode one, immediately closing controller, now system is stressed suddenlys change appearance, and cause slide block to rock, processing work is of low quality; Mode two, reduce the output of controller gradually, output due to controller is reduced to 0 needs a period of time, during this period of time continuation runs by slide block, until it is 0 that controller exports, but now the stop position of slide block has exceeded target location, the overshoot phenomenon that caused processing work to occur, bending angle changes, and cannot meet processing request.

Summary of the invention

Technical problem to be solved by this invention is: slide block location difficulty in controlling for existing bender, the problem that processing work precision is low, the invention provides a kind of electric liquid twin-tub slider of bender position control method, high accuracy can control slide position, effectively can improve the problems referred to above that prior art exists, realize the accurate positioning control to slide block under dynamic operation condition.The inventive method adopt improve PI and control+based on the Front feedback control of model, wherein, improve PI controller in the control structure of conventional PI controller, self-adaptative adjustment is carried out to integral action, the adjustment problem repeatedly that the conventional PI controller of effective solution exists at system positioning stage, avoids the overshoot phenomenon of processing work; Based on the Front feedback control of model, first the relationship model of slide position, system pressure and proportional servo valve is set up, then the feedback signal of system is utilized, obtain corresponding compensation rate, continuous Correction and Control amount, accelerate system responsiveness, thus improve position control accuracy, improve workpiece processing quality.

The general principle of the present invention's electricity liquid twin-tub slider of bender position control method: the control software design of PI controller has trajectory planning module and position control module.Trajectory planning module, for giving the movement locus order of the left cylinder of fixed slider and right cylinder.Position control module, for regulating the opening of proportional servo valve, realizes the accurate control to slide position.

The control method of PI location of controls control module adopts improves PI control (further prioritization scheme also add the Front feedback control based on model).Improve PI controller and comprise proportional action and integral action.Proportional action, namely carries out ratio control to the position deviation of system, integral action, namely controls the accumulation of position deviation, it realizes principle: based on the storage gain preset, according to the target location of slide block, when the trajectory planning module of the control software design of integral action active position point Y1(PI controller assigns slide block arrival dead point order, true location point Y1 residing for slide block), integral action switching position point Y2(sets a slide position threshold value S in advance according to different application occasion, when the physical location of slide block and the distance of bottom dead centre equal this threshold values, now the residing true location point of slide block is exactly integral action switching position point Y2), and the current actual positions of feedback, self-adaptative adjustment is carried out to integral action.Enter and pressure maintaining period specific to work: slide block is from the downward dead-centre motion of speed change point, and when slide block does not arrive integral action active position point Y1, proportional action exports effectively, and effect size is regulated by proportional gain, that is: u (k)=K pe (k) (formula 2), when slide block movement arrives integral action active position point Y1, integral action exports effectively, and effect size is regulated by storage gain, and now due to the existence of tracking error, the cumulative system control amount that makes of integral action continues to increase, that is: (formula 3), when slide block continues motion arrival integral action switching position point Y2, system control amount starts adaptive change, its variation tendency is reduce to the reduction of bottom dead centre distance with slide block, be implemented as: when slide block arrives integral action switching position point Y2, record controlled quentity controlled variable threshold value u (Y2) now, when slide block continues to run to bottom dead centre, the integral action of controller is no longer cumulative, on the contrary, about integral action switching position point Y2, controlled quentity controlled variable threshold value u (Y2), the function of location following error e (k), namely slide position moves to bottom dead centre from Y2, integral action is reduced to 0 from u (Y2), that is: u (k)=K pe (k)+u (Y2) * e (k)/S(formula 4).When slide block finally arrives bottom dead centre, because now tracking error is zero, therefore proportional action is zero, and meanwhile integral action is also adjusted to zero, therefore system control amount synchronous self-adapting is changed to 0, and system reaches poised state, starts pressurize; Until arrive the dwell time, top dead-centre is got back in slide block counter motion.

The so-called Front feedback control based on model, it realizes principle: first based on theory analysis and test data of experiment, set up the relationship model of slide position, system pressure and proportional servo valve opening, then the feedback signal of system is utilized, the cutout structural amount of the proportional servo valve that Real-time Obtaining and slide position, system pressure are corresponding, it revises rule is nonlinear curve about system pressure and slide block tracking error:

u comp ( k ) = K comp e ( k ) / Press (formula 5)

Wherein:

U compk () is the cutout structural amount of kth time sampling instant proportional servo valve;

K compit is the regulating parameter of default;

Press is current system pressure.

Based on the controlled quentity controlled variable that the Front feedback control module of model is exported by continuous modifier controller, early response system mode, regulates in advance before system puts in place, improves the response of system.

For left cylinder or the right cylinder of twin-tub bender, after the movement locus order of the given left and right cylinder of trajectory planning module, improve PI control by adopting+based on the Front feedback control algorithm of model, the oil cylinder of both sides can reach to the accurate tracking of given movement locus.Because the movement locus order of two cylinders is consistent, therefore slide block arranged on left and right sides is also consistent relative to the tracking error of movement locus, and this just fundamentally solves the problem of slide block arranged on left and right sides position synchronism.Therefore, adopt algorithm of the present invention, system also achieves the synchronism control of two cylinder positions while ensureing positioning precision.

The present invention adopts the Front feedback control algorithm based on model improving PI and control and optimize further, even if when two hydraulic cylinder characteristics slightly process by difference or unbalance loading, also the stability of slide block at running can be ensured, and the accuracy of locating during slide block arrival bottom dead centre, eliminate the overshoot phenomenon adding man-hour.Slide block touch workpiece, compressing, commutation leave in the whole course of work of workpiece, the effect self adaptation consecutive variations of controller, system stressed without impact, without sudden change, slide block movement smooth trajectory, moving component loss is low.Control method of the present invention, expands parameter role territory compared to conventional method, can not only ensure systematic steady state precision, and accelerates the response of system, makes slide block arrive target location more quickly, substantially increases working (machining) efficiency.High precision position control method provided by the invention, real-time, control effects good, be applicable to industry spot application.

Accompanying drawing explanation

Fig. 1 is the inventive method control flow chart.

Fig. 2 is existing methodical control effects figure.

Fig. 3 is the control effects figure of the inventive method.

Detailed description of the invention

Application of the present invention is electric liquid twin-tub bender, and this electric liquid twin-tub bender comprises with lower component: two proportional servo valve hydraulic control cylinder motions, and band movable slider pumps; Stroke detection parts, detect and feed back the physical location of slider of bender.Electricity liquid twin-tub bender carrys out the opening flow of control ratio servo valve by the power of the given signal of telecommunication of response controller, realize the positioning control to slide block.

Work is entered with in pressure maintaining period, the inventive method:

Trajectory planning module is to the process of movement locus order.The parameter that controller sets according to machining, comprising: slide block target location, system maximal rate and Acceleration and deceleration time, the running orbit of planning slide block, and by the data information memory planned in controller main control chip.

Stroke detection component retrieval slide block arranged on left and right sides is relative to the physical location of workbench reference point.

Position control module calculates the deviation between the track of planning and the slide block physical location of feedback.

Improve PI location of controls control module, calculate the aperture needed for proportional servo valve respectively according to slide block position.

Forging Process specific to electric liquid twin-tub bender plate: slide block is from the downward dead-centre motion of speed change point, and when slide block does not arrive integral action active position point Y1, proportional action exports effectively, and effect size is regulated by proportional gain, that is: u (k)=K pe (k); When slide block movement arrives integral action active position point Y1, integral action exports effectively, and effect size is regulated by storage gain, that is: when slide block continues motion arrival integral action switching position point Y2, record controlled quentity controlled variable threshold value u (Y2) now, when slide block continues to run to bottom dead centre, the integral action of controller is no longer cumulative, on the contrary, be the function about integral action switching position point Y2, controlled quentity controlled variable threshold value u (Y2), location following error e (k), namely slide position moves to bottom dead centre from Y2, integral action is reduced to 0 from u (Y2), that is: u (k)=K pe (k)+u (Y2) * e (k)/S is when slide block finally arrives bottom dead centre, because now tracking error is zero, therefore proportional action is zero, meanwhile integral action is also adjusted to zero, therefore system control amount synchronous self-adapting is changed to 0, system reaches poised state, starts pressurize; Until arrive the dwell time, top dead-centre is got back in slide block counter motion.

Front feedback control module, according to the relationship model of the slide position set up, system pressure and proportional servo valve opening, provide the correction of proportional servo valve opening, the size of correction calculates according to formula (5).Correction rule is the nonlinear curve about system pressure and slide block tracking error, that is: system pressure is larger, and Front feedback control amount is less; Slide block tracking error is larger, and Front feedback control amount is larger.According to revising rule above, Front feedback control module exports controlled quentity controlled variable and revises.

The actuating quantity improving PI controller is added with the actuating quantity of Front feedback control module, forms the final controlled quentity controlled variable needing to export.Proportional servo valve corresponding to slide block arranged on left and right sides revised controlled quentity controlled variable given respectively, carry out the opening flow of control ratio servo valve according to the power of the signal of telecommunication, thus control the position of slide block.

By above step, system realizes controlling the high accuracy of slide position.The method applied in the present invention, the process that slide block arrives bottom dead centre effectively can be predicted, and the deceleration control carried out in advance, solving system control amount controlled quentity controlled variable when slide block arrives bottom dead centre is not 0 overshooting problem produced, and meets the requirement of bender high accuracy processing.

As shown in Figure 2, because system does not have Automatic adjusument, slide block creates overshoot phenomenon after arriving target location.Fig. 3 is the control effects figure after algorithm improvement, indicate the change procedure of system control amount with slide position, comprise dynamic tracking phase, controlled quentity controlled variable add up the stage, stage that self-adaptative adjustment stage and system reach stable state, the Automatic adjusument function of algorithm makes slide block have accurate positioning precision.

Claims (2)

1. an electric liquid twin-tub slider of bender position control method, comprises work and enters and pressure holding step, it is characterized in that:
Described work progress is rapid, and when slide block does not arrive integral action active position point (Y1), proportional action exports effectively, and effect size is regulated by proportional gain:
u(k)=K Pe(k)
Wherein: k is sampling sequence number, k=0,1,2 ..., K pfor proportional gain, e (k) is the deviate of kth time sampling instant input, the controlled quentity controlled variable that u (k) exports for kth time sampling instant controller;
When slide block movement arrives integral action active position point (Y1), integral action exports effectively, and effect size is regulated by storage gain:
u ( k ) = K P e ( k ) + K I Σ j = 0 k e ( j )
Wherein: K ifor storage gain, e (j) is the deviate of jth time sampling instant input, and j is sampling sequence number, j=0,1,2
When slide block continues motion arrival integral action switching position point (Y2), record controlled quentity controlled variable threshold value u (Y2) now;
When slide block continues to run to bottom dead centre, the integral action of controller is reduced to 0 from u (Y2):
u(k)=K Pe(k)+u(Y2)*e(k)/S
Wherein: S is slide position threshold value;
When slide block finally arrives bottom dead centre, start pressurize.
2. a kind of electric liquid twin-tub slider of bender position control method according to claim 1, is characterized in that: the U obtained according to the following formula compk () is revised the controlled quentity controlled variable that controller exports:
u comp ( k ) = K comp e ( k ) / Press
Wherein: U compk () is the cutout structural amount of kth time sampling instant proportional servo valve, K compbe the regulating parameter of default, Press is current system pressure.
CN201310692114.2A 2013-12-16 2013-12-16 Method for controlling position of sliding block of electro-hydraulic double-cylinder bending machine CN103611767B (en)

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CN105573245B (en) * 2015-12-24 2019-01-11 马鞍山市中亚机床制造有限公司 A kind of numerical control bender precision debugging method
CN108435856B (en) * 2018-04-13 2020-03-17 吉林长光启元自动化控制有限公司 Bender slider positioning compensation method, system, equipment and numerical control system

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CN102430680B (en) * 2011-10-25 2013-06-26 中南大学 Super-slow hydraulic system for synchro-driven die-forging hydraulic press
CN102513413B (en) * 2011-12-03 2013-11-06 南京埃尔法电液技术有限公司 Hydraulic control system for novel servo pump control bending machine
CN102410272A (en) * 2011-12-03 2012-04-11 南京埃尔法电液技术有限公司 Electrohydraulic servo bending machine hydraulic system
CN102529148B (en) * 2011-12-29 2015-04-15 南京埃斯顿自动化股份有限公司 Method for controlling bottom dead center of slider of oil press

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