OTTER: Ocean Technology Testbed for Engineering Research
In line with the lab philosophy that a human/machine team will perform better than either alone, the OTTER vehicle will be controlled by a person at a high level. The onboard control system is intelligent enough to maintain all system functions and to provide an intuitive, easy-to-use interface to the operator. In this manner, instead of requiring a high skill level brought about by years of training and experience, the end-user, whether a marine scientist or commercial geologist, can direct the vehicle's actions with simple, intuitive commands. This concept of Object-Based Task-Level Control (OBTLC), pioneered by ARL, allows the user to focus his or her attention on decisions based on the manipulation of objects of interest (e.g. rock specimen or sampling equipment) and not on the control the vehicle to manipulate the objects.
In OBTLC, humans usually interface at the top level, doing what they do best-interpreting sensor data, making decisions, and reacting to events-while machines are used to process data and keep tight control of the low-level servos. However, because the system is designed to be vertically integrated, a person will be able to operate the system at all levels, perhaps directly controlling a thruster to help maneuver the vehicle out of a crevice.
This program is truly a microcosm of the lab. Research is being accomplished at all levels of control, including the architecture that binds the low servo level to the high task level. At the low level, the precise, high-speed control of a robotic arm underwater is being formulated for use in the autonomous retrieval of undersea specimens. Understanding and then controlling arm/vehicle dynamical interactions are important steps for that task as well. While much research has been performed in the general community on steady-state operations of thruster motors, the understanding of the control of thrusters operating under dynamic conditions is lacking. And it is this understanding which is required to provide thrust for precise positioning of a submersible.
These two basic research areas represent the lab's commitment to develop a basic understanding of the dynamics of electro-mechnical systems and the formulation of controllers to regulate them.
Another area of research in this program focuses on the architecture required to program the vehicle to perform complex tasks autonomously. This research builds upon and will expand the existing structure used throughout the lab to control robotic systems at a task level. Programming a system to react to events and to execute actions associated with events can become quite complex without a formal methodology. Previous and current research take formalisms found in computer science theory and extends them to controlling a real system.
Thus, the OTTER vehicle is not only a testbed for new ideas in systems integration and control, but is also a representative of how the ARL approaches system design with research at all levels of a vertical hierarchy.
For questions or comments contact: www@arl.stanford.edu
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