Adaptive Control of Underwater Snake Robot
Master thesis
Date
2019Metadata
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- Institutt for marin teknikk [3318]
Abstract
Ideen om bruk av slangeroboter til undervannsoperasjoner handler om dens fleksibilitet ogfordelaktige evne til å bevege seg rundt og inne i installasjoner under vann. Slangeroboterer antatt mer egnet for komplekse operasjoner enn mer konvensjonelle undervannsfarkoster.
Hovedfokuset i denne oppgaven er implementasjon av algoritmer for både adaptiv regulering og invers kinematikk for en slangerobot-simulator i MATLAB. Grunnen for atman vil bruke adaptiv regulering for slangeroboten er at den kan ha en veldig varierende dynamikk, da den kan innta flere ulike konfigurasjoner. Det er vanskelig å modellerekreftene på en kompleks robot som har en stadig varierende konfigurasjon. Derfor er detønskelig å ha en regulator som kan tilpasse seg den stadig varierende dynamikken. Slangeroboter skal kunne utføre ulike oppgaver under vann. Invers kinematikk er viktig for åkunne generere referansene for hvordan slangen faktisk skal bevege seg for å gjennomføreoppgavene den blir satt til å løse.
Et kort litteraturstudie har blitt skrevet om både slangerobotikk, adaptiv regulering oginvers kinematikk. Teorien som er nødvendig for implementasjon av algoritmene for inverskinematikk og adaptiv regulering er presentert, etterfulgt av en metodisk gjennomgåelseav hvordan systemet er definert.
Det implementerte systemet har blitt simulert og testet for fire ulike scenarioer. Utfradisse simuleringene kan det konkluderes med at den adaptive reguleringen fungerer sværtbra for de aller fleste oppgavene, men har en liten svakhet. Den implementerte inverskinematikken fungerer best for de enkleste scenarioene, men har problemer med å løseflere oppgaver samtidig. The idea of using underwater snake robots for subsea operations comes from their abilityto perform a wide range of missions, due to the slender and flexible body. Because ofthese advantages, they are expected to perform more complicated tasks than the moreconventional remotely operated vehicles.
The main focus of this thesis is the implementation of an adaptive control algorithmtogether with an inverse kinematics algorithm to control an underwater snake robot simulator in MATLAB. The need for an adaptive controller is identified as the snake robotmight take a range of configurations and interfere with objects subsea. This means that thedrag forces, among others, can vary a lot and change rapidly. Such changes are difficult tomodel and the idea is to have a controller which adapts to these changes. The underwatersnake robot should also perform several tasks. By defining the relationship between thesnake robot’s controllable states and the actual task, the inverse kinematics should be ableto calculate the desired motion for the snake robot to achieve the task.
Relevant background on these topics have been presented through a literature review.An adaptive control law has been implemented for the snake robot simulator in this thesis, along with an inverse kinematics algorithm. The theory behind these algorithms ispresented, and the process of implementing them is described. To implement these algorithms correctly, theory on kinematics for the snake robot have also been presented.
At last, the system has been simulated for four different cases. Each case defined oneor several tasks that should be achieved. The results showed that the adaptive controllerworked very well for most cases but had a small issue when the weight of the snake robotwas changed to simulate changed dynamics. The inverse kinematics also performed wellfor the simplest cases but could not always find a feasible solution to achieve several tasks.The conclusion is that the implemented adaptive controller and inverse kinematics couldwork well for the snake robot, but they need to be further investigated and modified.