LINKÖPINGS TEKNISKA HÖGSKOLA. Fluid and Mechanical Engineering Systems

Transcription

1 (6) Fluid nd Mechnicl Engineering Sytem ) Cvittion in orifice In hydrulic ytem cvittion occur downtrem orifice with high preure drop. For n orifice with contnt inlet preure of p = 00 br cvittion will trt when the outlet preure i reduced to p = 7 br. Aume tht the inlet preure i chnged to p = 80 br. For which vlue of p cn cvittion now be expected? A wy to void cvittion i to plit the preure drop over two or more orifice in eril connection. Decribe with eqution, which of two eril connected orifice cn tke the highet preure drop without ny rik for cvittion. (Aume tht the outlet preure for the econd orifice i zero). (4p) b) Servo vlve with buhing The min tge in n dvnced ervo vlve conit of pool nd vlve buhing. Decribe qulittively the benefit of uing buhing compred to vlve without buhing it the preure level i high. c) Flow force on pool vlve in contnt preure ytem The figure below how 4port criticl centre ervo vlve connected to contnt preure controlled pump. A digrm how the meured flow force veru vlve diplcement, x v. p p q p q v Dp v x v F 65 N n p p T = 0 F 0 0,6*x vmx x vmx x v Aume tht the mx pump flow (q pmx ) i increed to the me level the mx flow cpcity of the vlve with the me preure drop, Δp v for the meured ce. Show in digrm nd clculte the mximum flow force for tht ce.

2 3(6) Fluid nd Mechnicl Engineering Sytem ) Vlve wer nd it influence on vlve coefficient Wer on the orifice edge in zerolpped ervo vlve will cue chnge in the tedy tte chrcteritic round neutrl pool poition (x v = 0). Which of the vlve coefficient will be mot ffected by wer nd how i the cloed loop tiffne in poition ervo with proportionl controller gin influenced by thi? b) Direct driven ervo vlve in poition ervo A direct driven vlve, ccording to the figure below, i ued in poition ervo with proportionl controller. Decribe qulittively how the flow force will influence the tbility of the ervo ytem. A B Proportionlmgnet P T (p) c) Vlve controlled nd pump controlled poition ervo The figure below how vlve controlled nd pump controlled motor. Both ytem re ued rotting poition ervo with proportionl control. Volume, bulk modulu, motor diplcement nd lod inerti re equl in both ytem. Aume tht in the mot criticl operting point both ytem hve the me flow/preurecoefficient (K ce = C t ) nd the me mplitude mrgin, A m = 6 db. Show with eqution which of the ytem will given the highet tedy tte tiffne, ΔT L /Δθ m 0. (The tiffne of the cloed loop ytem i ked for). V e p p V V J t T L D m J t T L w p D p p m = kont p V D m

3 4(6) Fluid nd Mechnicl Engineering Sytem Poition ervo with 3port ervo vlve nd n ymmetric cylinder The figure how n electrohydrulic poition ervo with 3port vlve nd n ymmetric cylinder loded by m nd n externl force. The ervo h proportionl poition control with feedbck gin of x nd controller gin of K reg. The ervo vlve i zerolpped nd it h ymmetric nd mtched orifice nd the nullcoefficient re K qi0 nd K c0. The vlve h high bndwidth but h threhold, i T. The upply preure, p i contnt. The piton re i A, the re on the piton rod ide i A / nd the cylinder volume on the piton ide i V. The cylinder i umed to hve no lekge nd friction. The bndwidth of the cloed loop ervo ytem i b (with the mplitude 3 db, for given opertion point). Prmeter vlue: A =, m M t = 00 kg β e = 00 MP V = 0, m 3 p = 4 MP K qi0 = 0,03 m 3 /A K c0 = 8,0. 0 m 5 /N x = 5 V/m b = 5 rd/ i T = 0,4 ma ) Stedy tte poition error Clculte the mximum poition error (ΔX p ) which cn be cued by lod diturbnce ΔF L = 000 N nd together with the threhold of the vlve, i T. b) Lgcompention of the control loop Aume tht the proportionl poition controller (K reg ) i extended by lg filter / LC with the trnfer function GLC ( ) = α. The tedy tte gin α =,0. α / Clculte for thi ce the poition error cued by lod diturbnce only, (ccording to tk ). c) Influence from ervo vlve with low repone Dicu in generl how the bndwidth of the ervo ytem will be influenced if the vlve repone i lower tht the dynmic of the ctutor nd lod. (p) LC

4 5(6) Fluid nd Mechnicl Engineering Sytem Angulr poition ervo with dynmic preure feedbck G reg G p () p p L J t T L V V The figure how n elektrohydrulic poition ervo with vlve controlled motor. The proportionl controller h the gin G reg = K = 0,04 A/V. In order to incree the hydrulic dmping dynmic lod preure feedbck with the gin function G p ()= K pf. /( /f ) i implemented. The ervo vlve i of 4port type, zerolpped, with high bndwidth nd it zerocoefficient re K qi0 = 0,03 m 3 /A nd K c0 =,0. 0 m 5 /N. The volume between vlve nd motor re V = V = 0,5 litre nd it bulk modulu i β e = 000 MP. The motor diplcement i D m = 6, m 3 /rd, the lekge flow coefficient i C tm = 8, m 5 /N nd the vicou friction coefficient B m = 0. The motor hft inerti i J t = 0,5 kgm. ) Adjutment of the preure feedbck for given hydrulic dmping Clculte the ttic gin K pf for the lod preure feedbck, which give the hydrulic dmping δ h = 0,35 t the frequency h. The brek frequency in the preure feedbck filter i f = h /. (7p) b) The preure feedbck nd it influence on tedy tte tiffne Show with eqution tht the dynmic preure feedbck h mrginl effect on the tedy tte tiffne of the cloed loop ytem.

5 6(6) Fluid nd Mechnicl Engineering Sytem Lod dynmic for vlve controlled hydrulic cylinder The figure below how vlve controlled hydrulic cylinder loded by the me M nd M. The connection between the me include pring nd dmper (pring contnt K L nd vicou friction coeff B L ). The piton poition x p i fed bck to proportionl regultor with the gin G reg = K. x p M K L M p C C p Poition trnducer B L x L u c u f Servo mplifier K i P = cont. A u () The block digrm from vlve input ignl (i) to piton velocity (X p ) i: K qi i P L A V t p K ce X p GLX () (M M ) 4b e The trnfer function of the mechnic i G LX ( ) = δ δ, ( < ) ) Block digrm, frequency nd dmping of the poition ervo Reduce the feedbck in the bove block digrm nd drw new one for the complete poition ervo. Define the hydrulic reonnce frequency nd the dmping ( h, δ h ). b) Poition ervo loop gin for K h << K L Derive from the block digrm n expreion of the poition ervo loop gin A u () when the hydrulic pring contnt K h = 4β e A p /V t i much lower thn the mechnicl pring contnt K L ( h << ).