Control and Experimental Evaluation of Speed-variable Switched Differential Pump Concept
Translated title
Kontrol og Eksperimentel Evaluering af Hastighedsvariabel Skiftende Differential Pumpe Koncept
Authors
Rahn, Henrik ; Grønkjær, Morten
Term
4. term
Education
Publication year
2015
Submitted on
2015-06-11
Pages
150
Abstract
Speed-variable Switched Differential Pump (SvSDP) er en videreudvikling af det energieffektive Speed-variable Differential Pump (SvDP) koncept, som oprindeligt blev foreslået af Bosch Rexroth A/S. I SvSDP er tre gearpumper drevet af en enkelt elektrisk motor koblet direkte til ind- og udløbsportene på differentielle hydraulikcylindre (cylindre med forskelligt areal på stempel- og stangside). Denne opbygning har til formål at styre cylindrenes bevægelse effektivt. I specialet bliver et SvSDP-system designet og dimensioneret, og der bygges en alsidig testbænk til hydrauliske systemer for at muliggøre en generel evaluering af konceptet. Der udvikles en detaljeret, ikke-lineær dynamisk model af systemet, og modellens parametre bestemmes ud fra eksperimenter. Modellen lineariseres, og Relative Gain Array (RGA) analyse bruges til at vurdere, hvor stærkt styresløjferne påvirker hinanden (krydskoblinger). Analysen viser, at simpel decentraliseret regulering—hvor hver styresløjfe behandles uafhængigt—ikke er velegnet, og derfor undersøges afkoblingsstrategier. Selvom de udformede lukkede reguleringskredse ikke er afprøvet eksperimentelt, viser simuleringer, at den afkoblede regulering giver konsistent og acceptabel ydeevne: den lukkede sløjfes positionssporing har fejl under 3 mm, selv for rampekommandoer, der er svære at realisere i praksis.
The Speed-variable Switched Differential Pump (SvSDP) is a continuation of the energy-efficient Speed-variable Differential Pump (SvDP) concept originally proposed by Bosch Rexroth A/S. In SvSDP, three gear pumps driven by a single electric motor are connected directly to the inlet and outlet ports of differential hydraulic cylinders (cylinders with unequal piston areas). This setup is intended to control cylinder motion efficiently. In this thesis, an SvSDP system is designed and sized, and a multi-purpose hydraulic test bench is built to enable general evaluation of the concept. A detailed, nonlinear dynamic model of the system is developed, and its parameters are identified from experiments. The model is then linearized, and Relative Gain Array (RGA) analysis is used to assess how strongly the control loops interact (cross-couplings). The analysis shows that simple decentralized control—treating each control loop independently—is not suitable, so decoupling strategies are explored. Although the designed closed-loop controllers were not tested experimentally, simulations indicate that the decoupled control approach provides consistent, acceptable performance: closed-loop position tracking errors remain below 3 mm, even for ramp commands that are difficult to realize in practice.
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