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Research/Underwater

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Overview


Our research objective is to develop control algorithms to enable highly precise closed-loop maneuvering of underwater robotic vehicles. Closed-loop control of underwater vehicles is complicated by incompletely understood propulsor and vehicle dynamics, and the difficulty of state measurement (vehicle position and velocity) necessary for closed-loop control. Our methodology is to address these fundamental enabling theoretical issues for the next generation of remotely operated and autonomous underwater vehicles, and to experimentally verify our research results in actual working systems.

Fully-Actuated Control of Underwater Vehicles


Photograph of the JHUROV pitching up 35 degrees while employ our new 6-DOF model-based controller.
We have developed two 6-DOF fixed model-based controllers and one non-model-based 6-DOF controller designed to enable an underwater vehicle to perform 6DOF exact position and velocity tracking of a low-speed, fully actuated and neutrally buoyant underwater vehicle. This research is the first comparative experimental evaluation of both the identification 6-DOF coupled non-linear plant of a low speed, fully actuated, and neutrally buoyant underwater vehicle and the fixed model-based and non-model-based 6-DOF controllers based upon an identified model. We have found that the model-based controllers position and velocity tracking error is significantly smaller than the non-model-based controller.

Previously, we have developed a novel model-based adaptive control algorithms for a 1-DOF underwater vehicle. This research was supported by ONR under ONR Young Investigator Award N0014-97-1-0487 and NSF under CAREER Award BES-9625143.

People: Dr. Stephen Martin, Prof. Louis L. Whitcomb

Alumni: Dr. David Smallwood

Under-Actuated Control of Underwater Vehicles


Plot of JHUROV experimental velocity vs reference x direction postion vs time when employing a model-based underactuated controller.
Typically autonomous underwater vehicle are underactuated in the XY plane, with active actuation in the X and Heading direction. The result of this research will enable a new class of AUV’s capable perform missions presently associated with ROVs and Human Occupied Vehicles.

We have developed two underactuated fixed model-based controllers and one underactuated non-model-based controller designed to enable an underwater vehicle to perform exact position and velocity tracking in the XY plane. We have experimentally validated these controllers using our experimental testbed vehicle the JHUROV. We have found that the model-based controllers position and velocity tracking error is significantly smaller than the non-model-based controller.

People: Dr. Stephen Martin, Prof. Louis L. Whitcomb


Advanced Underwater Vehicle Design


We are presently involved in the design of the following three new underwater vehicles:

  1. JHU ROV#1, a new vehicle developed by Ph.D. students David Smallwood and Ralf Bachmayer, is presently nearing completion. This vehicle is a test-bed for underwater vehicle dynamics and control experiments. Supported by ONR and NSF.
  2. JASON II, a new vehicle developed in collaboration with faculty and engineers of the National Deep Submergence Facility (NDSF) at the Woods Hole Oceanographic Institution (WHOI). Supported by NSF.
  3. LSVII a fully-operational 150 ton ¼ scale-model of the NSSN new fast-attack submarine. We have advised Navy contractors Newport News Shipbuilding and the Electric Boat Division of General Dynamics Corporation on the performance requirements and design of 6-DOF force-torque instrumentation for all control and propulsion surfaces for this vehicle. Supported by Newport News Shipbuilding under contract POM-36700-T.
  4. Nereus Hybrid Remotely Operated Vehicle, a new full ocean depth vehicle developed in collaboration with the faculty and engineers of the National Deep Submergence Facility (NDSF) at the Woods Hole Oceanographic Institution (WHOI). Our laboratory is responsible for the development of the Acoustic Telemetry System, Navigation, High-Level Controller and Low-Level Controller of this vehicle.

Engineering Field Tests of Newly Developed Underwater Vehicle Systems


We strive both to develop new robot navigation and control systems and to experimentally validate them in at-sea oceanographic deployments. To achieve this, we have a highly effective collaboration with the Deep Submergence Operations Group (DSOG) at the Woods Hole Oceanographic Institution (WHOI). To date, we have conducted at-sea experimental validation of systems we have developed in numerous extended oceanographic deployments.

Propulsor Modeling and Control


We have developed the most precise reported finite-dimensional nonlinear model for the unsteady dynamics of marine thrusters, experimentally validated this model, and compared its performance all previously reported dynamical models. We are presently employing our models to develop and experimentally validate model-based adaptive thrust controllers for marine thrusters. To perform this research we have developed a thruster test facility providing precise high-bandwidth 6-axis force/torque sensing and acoustic doppler fluid flow sensing, as shown below. Supported by ONR under ONR Young Investigator Award N0014-97-1-0487 and NSF under CAREER Award BES-9625143.

Vehicle Navigation


Precise vehicle state measurement is an often overlooked antecedent to precision closed-loop control of underwater vehicles. In collaboration with Dana Yoerger and Hanumant Singh (WHOI) we have developed an improved underwater vehicle navigation system that enables closed-loop control in operations where it was previously impractical or infeasible. This system, which combines (a) a conventional long-baseline acoustic navigation, (b) a new bottom-lock doppler multibeam sonar, and (c) Honeywell ring-laser gyroscope heading reference, provides order-of-magnitude improvement in the precision and update rate of deeply submerged vehicle navigation. Supported by ONR and NSF.



This page was last modified on 23 April 2011, at 13:56.