Experimental Comparison of Kinematic Task-Priority Control Methods for an Articulated Intervention-AUV
Bjørn Kåre Sæbø, Markus H. Iversflaten, Kristin Y. Pettersen, Jan Tommy Gravdahl
AI summary
Problem
Classical task-priority control methods lack experimental validation for free-floating articulated underwater vehicles, where body-frame placement and overlapping task dependencies critically influence controller behavior.
Approach
The authors theoretically analyze two kinematic control formulations using a new task-compatibility taxonomy and body-velocity sharing concept, then validate their predictions through open-water field trials with the Eelume-M AIAUV.
Key results
- Formalization of body-velocity sharing and task-compatibility taxonomy
- Demonstration that body-frame placement directly dictates controller performance
- Experimental confirmation that projected-residual law enhances secondary-task tracking but suffers from algorithmic singularities
- Experimental confirmation that post-projection law ensures singularity robustness with reduced secondary-task accuracy
Why it matters
Provides actionable guidelines for selecting control laws and body-frame configurations for engineers and researchers developing free-floating underwater intervention robots.
Abstract
This work revisits two classical closed-loop inverse kinematics (CLIK) formulations for hierarchical control and investigates their differences in the context of articulated intervention-autonomous underwater vehicles (AIAUVs). The class of AIAUVs consists of free-floating, slender, multi-link vehicles with distributed thrusters and no distinct base, allowing the entire vehicle to be modeled and controlled as a manipulator. The concept of body-velocity sharing, a phenomenon where different tasks depend on overlapping body-frame motions, is introduced and formalized through the notion of body- sensitivity subspaces. Changing the location of the system’s body-frame is shown to directly affect both controllers’ closed- loop performance, and it shown that due to body-velocity sharing, tasks for AIAUVs most often fall into an intermediate regime between orthogonal and strictly incompatible tasks, causing the two task-priority formulations to differ. The theory is validated through open-water field trials with the Eelume-M, a 6-meter-long AIAUV, comparing the two control laws. The experiments confirm the theoretical predictions: the projected- residual law improves secondary-task tracking but is more sen- sitive to algorithmic singularities, whereas the post-projection law remains robust to such singularities at the cost of reduced secondary-task performance. These results provide practical guidelines for selecting kinematic task-priority control laws and body-frame placement for AIAUVs.