Autonomous external pipe crawling robot for offshore inspection

Uth, Esben Thomsen ; Edling, Mikkel ; Larsen, Jannic Schurmann

4. semester

Sustainable Energy Engineering, Master

2024

2024-05-31

189 pages

Målet med denne rapport er at reducere mængden af hjulspin under offshore missioner med SubC Partner's Crawler. Andre mål for rapporten er at øge mængden af autonomitet af robotten samt at sænke mængden af kompleksitet omkring missionerne. Crawleren blev delvist opgraderet med tre elektriske motorer til at drive den. To LQR-tunede kontrolsystemer blev designet til at følge en referenceposition og hastighed, baseret på gain scheduling. For at reducere mængden af hjulspin blev et hjælpeslipkontrolsystem udviklet, baseret på en sliding mode observer. For at overkomme forhindringer blev et logikkontrolsystem udviklet til at reducere mængden af klemmetryk i Crawleren. Kontrolsystemerne blev afprøvet i forskellige simulationsscenarier på en udviklet ikke-lineær model. Her blev det vist, at de elektriske drev kan levere en fuld rotation på et testrør med en radius på 0,54 m, selv med et hjul, der laver hjulspin. I fysiske tests blev det vist, at de implementerede kontrolsystemer havde svært ved at håndtere den lave hastighedsreference på 0,016 rad/s. Det blev konkluderet, at med en yderligere gearreduktion på 3 kan opnås et lavere hastighedsområde. Dette, sammen med et kontrolscenarie, der gør brug af gain scheduling, kan opnå de kriterier, der er sat af SubC Partner. Samtidig vil den øgede mængde af tilgængelig torque muliggøre reduktionen af antallet af elektriske motorer til to. Mikkel Edling er også med.

The goal of this report is to reduce the effect of wheelspin in offshore operations using the SubC Partner crawler. Further goals were set to reduce the complexity of these operations as well as increase the autonomy of the robot. The crawler was partly upgraded with a drivetrain consisting of three electric motors, for which two LQR tuned controllers were designed to track position or velocity based on gain scheduling. To reduce wheelspin, a supervisory slip controller was developed based on a sliding mode disturbance observer. To overcome obstacles, a logic controller was developed to reduce the clamp pressure of the crawler. The controllers were tested in various conditions on a developed non-linear model. Here, it was found that the electric drive is capable of obtaining one full rotation of the offshore member of 0.54 m radius even with one wheel slipping. In physical tests, it was found that the implemented controllers had difficulty handling the low reference velocities of 0.016 rad/s. It is concluded that with a further gear reduction of 3, a lower speed range can be obtained. This together with a control scheme using gain scheduling can meet the velocity and position requirements posed by SubC Partner. The increase in available torque would also reduce the number of motors needed for the electric drive to two.

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