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Development of an active suspension control strategy for a forestry machine with pendulum arms
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Utveckling av en styrstrategi för enpendelarmsskotare med aktiv fjädring (Swedish)
Abstract [en]

The forest industry depends on the cut to lenght method for production. The forwarder

is one of the machines used in this process. These machines currently have

no suspension, which leads to big problems such as lower productivity and higher

soil damage.

A relatively new approach to solve these problems is to use pendulum arms

actuated by hydraulic cylinders. This solution turns out to be complex, since there

are more actuators than variables controlled. This paper discusses several strategies

to control such a system in order to minimize pitch and roll, while decoupling from

vertical accelerations.

A solution based on a nonlinear car model is suggested, and an implementation

based on this model and using a pole placement technique is developed and compared

in simulink with the same model with no suspension.

Results show that this strategy is able to reduce pitch and roll considerably,

while offering the possibility of adding a vertical displacement controller with little

coupling between each other. The next steps towards implementation are to integrate

the dynamics of the actuator, to consider robustness and noise interference, as well

as the effects of discretization.

Abstract [sv]

Skogsindustrin idag använder i stor utsträckning skördar/skotar metoden för att

producera. Skotaren är en av de maskiner som används i processen. Dessa maskiner

har i dagsläget inngen fjädring, vilket leder till stora problem som exempelvis lägre

produktionstakt och markskador.

En relativt ny lösning för att lösa problemet är att använda pendelarmar med

hydrauliska cylindrar som hjulupphängning. Lösningen visar sig snabbt vara komplex,

eftersom det finns fler ställdon än de variabler som skall regleras. I den här

rapporten diskuteras flera strategier för att få bukt med problemet och minimera

roterande och vertikala rörelser.

En lösning som baseras på en olinjär dynamisk modell tas fram, och en implementation

som bygger på en polplacerings teknik utvecklas och jämförs med den

olinjära modellen, utan fjädring, i Simulink.

Resultaten tyder på att strategin reducerar de roterande rörelserna avsevärt,

medans möjligheten att styra den vertikala rörelsen är stor och påverkar rotationerna

minimalt. Nästa steg i utvecklingen av fjädringssystemet är att även ta till hänsyn

den hydrauliska cylinderns dynamik, och undersöka hur robust systemet är och ta i

beakt det faktum att systemet skall verka i diskret tid.

Place, publisher, year, edition, pages
2014. , 81 p.
Series
MMK 2014:47 MDA 474
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-157416OAI: oai:DiVA.org:kth-157416DiVA: diva2:769945
Supervisors
Examiners
Available from: 2014-12-09 Created: 2014-12-09

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