In the absence of the material,theblades rest in the zero-positionT,(Fig. 1)waiting forthe accelerationcommand.At the instant to, the control logic 9receives a signal from the photosensor F indicating the appearance of the material.The desiredcutting length of theusually deformedfrontofmetalSf enlargedbythe distance LF between the photosensorFand the axis of theflying shear is enterd into the material path counter 7.and the condition for the acceleration command safis computed according to (27).At the instant t1.when the content of the material path counter sm decreases below Safthe control logicgives the acceleration command, thereby starting the acceleration algorithm(21)(block10). Accelerationof thebladesresultsinanincreaseinthebladeyositioncounter contentdue to pulses from the blade encoder 4. Atthe instant t2when the content of the bladeposition counter becomessbzso/2+Sbl, the blades reach point Tin(Fig.1),and via block14the controllogicswitches off the accelerationalgorithm andstartsthe algorithm(5)for theblades enteringthe
material(block11).Atthe instant t3,the blades are in point Tc (the deformed front of
thematerialhas beencutoff),andasynchronizing pulse C from the blade encoder 4
appears.The content ofthe bladeposition counter 8is set to zero,the desired length
of the next section (Smr)is entered into thematerial path counter 7,and the condition for
theaccelerationcommandSaiscomputed according to(24)and(25)using the given Smr value. After that the control logic starts the algorithm(6)for the blades emerging from the material(block 12).Atthe instant t4,when the blades cometo point To,the contentofthe bladeposition counter becomesSb=So/2- sbl,and thecontrollogic (viablock14) switches off the algorithm(6)and starts the deceleration algorithm (13)(block13 in Fig. 2). The blades decelerate until the Content Of the material path counter S,becomes less than Sa,oruntil the blades stop in thezero- position. Both cases are illustrated in Fig. 3. As may beseen,the desired length of the first section Smriis longer than the boundary section smb definedby(28),sothat the blades stopin the zero-positionwhere they waitfor theaccelerationcommand (discontinuous mode).On the other hand,the desired length ofthesecond section S,2is shorter than the boundary section Smb,sothat the acceleration command appears beforethe bladesreachthezero-position (continuous mode).
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