Hans Christian Woithe

A programming architecture for smart autonomous underwater vehicles

Autonomous underwater vehicles (AUVs) are an indispensable tool for marine scientists to study the worlds oceans. The Slocum glider is a buoyancy driven AUV designed for missions that can last weeks or even months. Although successful, its hardware and layered control architecture is rather limited and difficult to program. Due to limits in its hardware and software infrastructure, the Slocum glider is not able to change its behavior based on sensor readings while underwater. In this paper, we discuss a new programming architecture for AUVs like the Slocum. We present a new model that allows marine scientists to express AUV missions at a higher level of abstraction, leaving low-level software and hardware details to the compiler and runtime system. The Slocum glider is used as an illustration of how our programming architecture can be implemented within an existing system. The Slocums new framework consists of an event driven, finite state machine model, a corresponding compiler and runtime system, and a hardware platform that interacts with the gliders existing hardware infrastructure. The new programming architecture is able to implement changes in glider behavior in response to sensor readings while submerged. This crucial capability will enable advanced glider behaviors such as underwater communication and swarming. Experimental results based on simulation and actual glider deployments off the coast of New Jersey show the expressiveness and effectiveness of our prototype implementation.

Slocum Glider energy measurement and simulation infrastructure

Autonomous underwater vehicles (AUVs) are indispensable tools for marine scientists to study the worlds oceans. Depending on their missions, AUVs are equipped with advanced sensors (sonar, cameras, acoustic communication, bio-sensors), have on-board computers for data analysis (image analysis, data compression), and are capable of on-board decision making (resource planning, swarming). Since AUVs operate solely on battery power, power and energy management is a crucial issue. Mission-critical tradeoff decisions have to be made between energy consumption and sensing, data processing, and communication activities. Mission planning has to consider these tradeoffs when provisioning resources for expected future events, or when dealing with changing environmental conditions such weather, water currents, and seafloor profiles. Effective power and energy management requires knowledge about the actual energy consumption of each active component within the AUV. Effective planning requires simulators that can predict energy consumptions based on expected future events and environmental conditions. In this paper, we discuss the design and implementation of a power measurement infrastructure for the Teledyne Webb research Slocum glider. This infrastructure can be used for online power/energy management or to better understand the time-dependent energy consumption profile of the active glider components during a particular mission. We also discuss the design of a new simulation environment for the Slocum glider which uses the power/energy data obtained by our measurement infrastructure, in addition to seafloor and coastal radar information. We illustrate the effectiveness of the new tools in the context of planning a glider flight across the continental shelf off the coast of New Jersey.

Improving Slocum Glider dead reckoning using a Doppler Velocity Log

The Slocum Electric Glider is a buoyancy driven Autonomous Underwater Vehicle (AUV) capable of long term deployments typically lasting four to six weeks. During missions execution, the vehicle makes use of the Global Positioning System (GPS) to navigate to its commanded waypoints. GPS, however, can only be used while the vehicle is at the surface. While underwater, the glider uses a simple dead reckoning (DR) algorithm to estimate its location and does not find its true position again until its next periodic surfacing. The Slocum Gliders dead reckoning algorithm estimates its position based on speed and heading calculations; they are derived from measurements from onboard sensors. Specifically, speed is determined by the depth rate change and pitch angle over a period of time. Since there is limited sensory input to the algorithm, the vehicles estimated global position can differ significantly from its true position. Precise location information is important when collecting spatiotemporal sensitive sensor data and for vehicle navigation. In this paper, we will explore the benefits that can be gained if the dead reckoning algorithm makes use of a Doppler Velocity Log (DVL) to improve a vehicles location estimates. Initial results based on a deployment equipped with the DVL on a Slocum Glider show promising results.

Parallelization of path planning algorithms for AUVs concepts, opportunities, and program-technical implementation

Modern autonomous underwater vehicles (AUVs) have advanced sensing capabilities including sonar, cameras, acoustic communication, and diverse bio-sensors. Instead of just sensing its environment and storing the data for post-mission inspection, an AUV could use the collected information to gain an understanding of its environment, and based on this understanding autonomously adapt its behavior to enhance the overall effectiveness of its mission. Many such tasks are highly computation intensive. This paper presents the results of a case study that illustrates the effectiveness of an energy-aware, many-core computing architecture to perform on-board path planning within a battery-operated AUV. A previously published path planning algorithm was ported onto the SCC, an experimental 48 core single-chip system developed by Intel. The performance, power, and energy consumption of the application were measured for different numbers of cores and other system parameters. This case study shows that computation intensive tasks can be executed within an AUV that relies mainly on battery power. Future plans include the deployment and testing of an SCC system within a Teledyne Webb Research Slocum glider.

A lightweight scripting engine for the Slocum Glider

Underwater Vehicle (AUV) capable of deployments lasting several weeks or months. The layered control architecture used by the vehicle is difficult to program and restrictive. As part of previous work we have developed a more flexible programming framework capable of performing dynamic feature tracking. However, the gliders new and more computationally capable Linux Single Board Computer (SBC) results in additional energy demands.

An interactive slocum glider flight simulator

The Slocum Glider is a commercially available autonomous underwater vehicle used in the sensing of the worlds oceans. Its manufacturer-provided simulator uses nearly identical electronics and components as installed in the production glider. The simulator is mainly used to develop and test new hardware and software components in a real-time setting, where for instance, a one-week mission of the glider takes one week to simulate. This limits the types and the complexities of algorithms that can be developed and tested on the vehicle. In this paper, we present our ongoing work on a simulation infrastructure used to fly and operate a Slocum Glider in a virtual ocean environment. We also introduce a new three dimensional companion visualization tool. The effectiveness of the infrastructure and its new visualization tool is illustrated in the context of three applications, namely glider education and training, the replay and analysis of glider missions, and the design and testing of algorithms to be used in future missions.

TrilobiteG: A programming architecture for autonomous underwater vehicles

Programming autonomous systems can be challenging because many programming decisions must be made in real time and under stressful conditions, such as on a battle field, during a short communication window, or during a storm at sea. As such, new programming designs are needed to reflect these specific and extreme challenges. TrilobiteG is a programming architecture for buoyancy-driven autonomous underwater vehicles (AUVs), called gliders. Gliders are designed to spend weeks to months in the ocean, where they operate fully autonomously while submerged and can only communicate via satellite during their limited time at the surface. Based on the experience gained from a seven year long collaboration with two oceanographic institutes, the TrilobiteG architecture has been developed with the main goal of enabling users to run more effective missions. The TrilobiteG programming environment consists of a domain-specific language called ALGAE, a lower level service layer, and a set of real-time and faster-than-real-time simulators. The system has been used to program novel and robust glider behaviors, as well as to find software problems that otherwise may have remained undetected, with potentially catastrophic results. We believe that TrilobiteG can serve as a blueprint for other autonomous systems as well, and that TrilobiteG will motivate and enable a broader scientific community to work on extreme, real-world problems by using the simulation infrastructure.

Comparison of guidance modes for the AUV “Slocum Glider” in time-varying ocean flows

This paper presents possibilities for the reliable guidance of an AUV “Slocum Glider” in time-varying ocean flows. The presented guidance modes consider the restricted information during a real mission about the actual position and ocean current conditions as well as the available control modes of a glider. A faster-than-real-time, full software stack simulator for the Slocum glider will be described in order to test the developed guidance modes under real mission conditions.

DESIGN AND IMPLEMENTATION OF AN ENERGY AWARE PROGRAMMING FRAMEWORK FOR AUTONOMOUS UNDERWATER VEHICLES

OF THE DISSERTATION Design and Implementation of an Energy Aware Programming Framework for Autonomous Underwater Vehicles by Hans Christian Woithe Dissertation Director: Ulrich Kremer Autonomous underwater vehicles (AUVs) have become an indispensable tool for studying the oceans. They allow for the prolonged presence of scientific instruments in the ocean, enabling the collection of samples for several weeks or months at a time for a fraction of the cost of research vessels. These vehicles share common characteristics and constraints with other cyber-physical systems that include concerns for vehicle safety, a limited energy supply, the optimization and trade-off of resources, sporadic communication, and operation in extremely constrained environments. One such AUV is the Slocum Electric Glider. Although AUVs like the Slocum Glider have revolutionized the field of oceanography, many are difficult to program and thus limit their overall utility. A new energy aware, domain specific programming framework for AUVs, called ALGAE (AUV Language for Greater Adaptability and Energy optimization), has been developed on the Slocum Glider. This framework enables scientists to easily create missions that use domain specific features to make trade-offs, such as sacrificing the