Unmanned underwater vehicles are expected to play a critical role in future U.S. Navy operations and industrial endeavors. The UUV community, and in particular, the U.S. Navy’s acquisition organization responsible for littoral and mine warfare has recognized that standards are necessary for cost-effective development and acquisition of various vehicles and payloads and to enable commonality across systems.
The need for a UUV to operate without direct human intervention and with flexibility based on its payload and mission places unique requirements on UUV developers. Because the UUV community is expected to expand both its developer base and its user base in the next several years, it recognizes that success lies with well-written standards that provide a framework to assure utility and yet simultaneously encourage innovation. This article describes the general direction in which the UUV community is moving to adopt a set of standards that will ensure flexibility, modularity, and the ability to economically implement future upgrades.
The UUV community, in conjunction with ASTM International, has identified several areas as critical for standardization and has created ASTM Committee F41 on Unmanned Undersea Vehicle Systems. The main committee consists of three subcommittees:
• F41.01 on Autonomy and Control Architecture;
• F41.02 on Communications; and
• F41.03 on Mission Payload Interface.
Committee F41 will balance the procurement needs of industry with the research community’s desire for exploratory freedom by providing standards that define today’s products and focus tomorrow’s technologies. ASTM’s standards development processes will be important to establishing standards for UUVs, allowing the systems to benefit from commonality and modularity in an open-architecture framework.
Both the U.S. Navy and commercial industries have recognized that UUVs have the potential to greatly enhance the capabilities of manned platforms by providing access to otherwise unreachable or dangerous areas without putting personnel at risk. While tethered remotely operated vehicles may provide many of the same capabilities, the need for a physical connection between the vehicle and the host platform limits both range and payload and requires a dedicated platform for the duration of the mission. Elimination of the human-in-the-loop distinguishes UUVs from other unmanned vehicles (such as aircraft and surface vehicles) that to date rely on high bandwidth radio frequency communication for remote human control. This drives the need for vehicle autonomy to execute multiple, complex tasks with minimal to no human intervention.
UUV applications include the Navy’s need to survey an underwater mine field, an oil company’s need to examine an oil rig, or a communication company’s need to inspect an underwater cable. For Navy applications, UUVs have been grouped into four classes based on size: man-portable (3 to 9 inches diameter), lightweight (12.75 inches), heavyweight (21 inches) and large (greater than 36 inches).
Modular, interchangeable sensors and payloads between these classes will enable the economical development of UUVs to meet the anticipated variety of applications. An effective autonomy standard, or set of standards, must balance the need for modularity with the need for reliable and safe vehicle control, and be flexible and scalable so that future innovation is not stifled.
The term autonomy and its associated components often have different interpretations. A first step in the standards process is to converge on terminology (see Table 1).
Required High-Level Capabilities
The capabilities required for autonomy include:
• Reconfigurability to support multiple missions;
• Standard interfaces to facilitate interconnection with various vehicle, sensor, and payload modules;
• Functionality to permit extended periods of unmonitored operation;
• Modular structure to minimize test and retest as functions are added, expanded, or modified;
• Throughput to assure tactical value; and
• Robust control to handle unforeseen situations.
Committee F41 will develop standards that ensure these high-level autonomy capabilities are achieved. It is important that these standards support the specific capabilities and attributes identified below.
Varying Levels of Autonomy
Autonomy must support interactions between vehicles having different levels of autonomy. Not all missions require the same degree of autonomy. This may occur within or among vehicle classes. For short range, noncomplex missions, autonomy could be limited to autonomous attitude control with a communication link to a human operator. On longer, complex missions, the autonomy function may be required to supplant the human operator. In such cases, the UUV may need to return to a specified location at a predetermined time after having accomplished multiple tasks with only high-level mission instructions in an area with incomplete environmental data. This may occur among different vehicles of the same class or among different vehicle classes.
Multi-UUV collaboration should increase the likelihood of achieving mission objectives of the system over and above that achievable by a base capability of UUVs acting independently. In this case, “independently” refers to a vehicle acting without any collaboration (e.g., communication, coordination, or sharing of information) with other vehicles. The future of autonomy will doubtlessly require interactions among vehicles. Whether among similar vehicles with different capabilities (for example, all the same class but each with a different payload), or among different vehicle classes (large vehicles interacting with smaller vehicles having different endurance and payload capabilities), the vehicle team should be able to behave autonomously in concert.
The physical configuration of a UUV should not drive the autonomy module and vice versa. It is desirable to have core autonomy software that can be ported to any vehicle class. Then, specifics for that vehicle can augment that autonomy core. The result is an autonomy capability that is platform- or vehicle-independent.
Autonomy software should be designed using standard interfaces and be flexible enough to accommodate the introduction of new sensors and payloads. Typical payloads may include forward- and side-looking sonars, satellite communication systems, a global positioning system, extendable masts, recovery mechanisms, homing and docking arrays, and supporting electronics. Energy, propulsion, ballast, and similar vehicle control components of UUVs also require common interfaces to the autonomy software. In a similar fashion, autonomy software interfaces should be able to accommodate future, undefined modular sensors and payloads.
The autonomy module will likely perform the situational awareness, assessment, monitoring, and planning functions as well as related support functions such as input and output handling, data logging, and enabling feedback to off-board or onboard clients. It should be structured for multi-processing and background tasking to take maximum advantage of reserve processor capacity. In addition, it should support off-board pre-sortie planning.
The interfaces to autonomy can be described by functional groups of logical physical interfaces representing the major external systems and subsystems. A general schematic is shown in Figure 1.
The physical interfaces will be largely dependent on the characteristics of specific UUV classes, however, independent of the physical layer, the autonomy interface can be largely the same. This would mean that although there might be different and evolving physical interfaces, the same information can be passed in a standardized format, permitting interconnection with a wide variety of systems and subsystems. Initially, as disparate systems are federated, these interfaces may require individual interface modules to handle the specifics of the pre-existing real-time interfaces. However, with the unification enabled by standardization, such translation modules will become unnecessary over time and systems will be less complex and have fewer components, resulting in higher reliability and lower cost.
The recently formed ASTM Committee F41 will focus the development of standards and guidance materials for unmanned undersea vehicle systems to facilitate an interoperable, modular, and multi-functional family of platforms. The work of this committee will be coordinated with other ASTM committees and organizations having mutual interests.
Subcommittee F41.01 on Autonomy and Control Architecture will generate standards to support UUV developers in the area of autonomy and to assure that autonomy modules can interface with the numerous disparate vehicles and vehicle subsystems being developed. Conversely, the standards developed will enable vehicle developers to readily interface with autonomy modules that:
• Support open architecture and open source code development;
• Allow extension of capabilities via modular architectures;
• Provide automated situational awareness, assessment, and plan generation;
• Are portable, reconfigurable, platform independent, with well- defined interfaces;
• Support synchronous and asynchronous inputs and outputs;
• Dynamically generate and execute plans and support real-time re-planning;
• Generate internal representations of the external world (world model);
• Satisfy multiple, simultaneous objectives;
• Support multi-vehicle coordinated operations; and
• Support safe operations in dynamic environments without human intervention.
The generation, use, and adoption of standards by the UUV community will facilitate future technology insertion, ease the incorporation of advanced sensors and payloads, enable capability growth, and control costs. //