Victor H. L. Cheng

Real-time computational methods for SDRE nonlinear control of missiles

Computational speed and performance issues arising in the practical implementation of the state dependent Riccati equation (SDRE) technique are discussed. A software package for real-time implementation of the SDRE technique was developed during the present research. The execution of this software at speeds up to 2 kHz sample rates on problems of the size commonly encountered in missile flight control applications is then demonstrated on commercial off-the-shelf processors.

Considerations for Automated Nap-of-the-Earth Rotorcraft Flight

In this paper, we consider nap-of-the-earth (NOE) rotorcraft flight as one of the applications in which obstacle avoidance plays a key role, and investigate the prospects of automating the guidance functions of NOE flight. Based on a proposed structure for the guidance functions, we identify obstacle detection and obstacle avoidance as the two critical components requiring substantial advancement before an automatic guidance system can be realized. We discuss the major sources of difficulties in developing these two components, including sensor requirements for which we provide a systematic analysis.

Concept development of automatic guidance for rotorcraft obstacle avoidance

The automatic guidance of rotorcraft for obstacle avoidance in nap-of-the-earth flight is studied. The author considers a hierarchical breakdown of the guidance components to identify the functional requirements. These requirements and anticipated sensor capabilities lead to a preliminary guidance concept, which has been evaluated via computer simulations. >

Automatic guidance and control laws for helicopter obstacle avoidance

The authors describe the implementation of a full-function guidance and control system for automatic obstacle avoidance in helicopter nap-of-the-earth (NOE) flight. The guidance function assumes that the helicopter is sufficiently responsive so that the flight path can be readily adjusted at NOE speeds. The controller, basically an autopilot for following the derived flight path, was implemented with parameter values to control a generic helicopter model used in the simulation. Evaluation of the guidance and control system with a 3-dimensional graphical helicopter simulation suggests that the guidance has the potential for providing good and meaningful flight trajectories.<<ETX>>

Technologies for Automating Rotorcraft Nap-of-the-Earth Flight

This paper discusses the technologies required for automating rotorcraft nap-of-the-earth flight, where the use of natural obstacles for masking from the enemy is intentional and the danger of undesirable obstacles such as enemy traps is real. Specifically, the automatic guidance structure is modeled by three decision-making levels: the far-field mission planning and the mid-field terrain-masking trajectory shaping are both driven by prestored terrain data, whereas the nearfield obstacle detection/avoidance is driven by real-time on-board sensor data. This paper summarizes the far-field and mid-field accomplishments, and reports on the status of the more-recent efforts in obstacle detection and avoidance development. Obstacle detection is based primarily on passive imaging sensors for the desirable properties of covertness and wide field of view, although active sensors are included in the structure to provide the much needed high resolution for thin-wire detection.

Evaluation Plan for an Airport Surface-Operation Automation Concept

The predicted growth in air travel demands capacity enhancement in the National Airspace System, and congestion at key airports has been recognized as one of the most prominent problem areas. With flights operating at limits dictated by operational requirements associated with current airport configurations, airport expansion plans involving addition of new runways and taxiways are being realized to increase the airports’ capacities. However, the expansion plans necessarily increase the complexity of the airport configurations, which tends to penalize the efficiency of the system, partially offsetting the capacity-related benefits of the investments. The Surface Operation Automation Research (SOAR) concept has been proposed as a collaborative concept to provide automation for surface-traffic management and the flight deck to enhance the operational efficiency in complex airport environments, thus reversing the penalties to fully realize the capacity benefits sought by the airport expansion plans. Development and evaluation of the SOAR concept is being pursued in a 5-year program, and this paper describes the experiments being designed for an initial evaluation during the second year of this program.

A Queuing Framework for Terminal Area Operations

As a part of NASA’s NextGen research effort, the focus area of Airspace Super-Density Operations (ASDO) performs research pertaining to highly efficient operations at the busiest airports and terminal airspaces. It is expected that multiple ASDO concepts will be interacting with one another in a complex stochastic manner. This research effort developed a high-fidelity queuing model of the terminal area suitable for the design and analysis of NextGen ASDO concepts, as well as to perform time-varying stochastic analysis of terminal area operations with regards to schedule and wind uncertainties. A unique aspect of the current approach is the discretization of terminal airspace routes into 3-nmi servers for enforcing separation requirements. The current research effort developed high-fidelity queuing models of the San Francisco International Airport (SFO) terminal airspace, based on published airspace geometry. A discrete-event simulation framework was developed to simulate the temporal evolution of flights in the terminal area. The queuing simulation framework was used in different case studies involving various phenomena in the terminal area such as compression, conflict and delay analysis, runway reconfiguration and variable inter-aircraft separation. In addition to being a useful analysis tool, the proposed simulation framework shows potential as a real time stochastic decision support tool due to its low computational cost.

Information Requirements for Pilots to Execute 4D Trajectories on the Airport Surface

*† ‡ Trajectory-based operations constitute a key mechanism considered by the Joint Planning and Development Office (JPDO) of the U.S. for managing traffic in high-density or highly complex airspace in the Next-Generation Air Transportation System (NextGen). With this concept applied to surface operations at major airports, current research has been exploring the use of surface 4-dimensional (4 D) trajectories, which use required times of arrival (RTAs) at selected locations along the taxi route. The research has explored the use of collaborative automation systems in the control tower and on the flight deck to plan and execute these 4D trajectories to achieve safe and efficient surface operations, and prototype experimental systems for these automation systems have been developed. This paper reports on a study with human-in-the-loop experiments performed using prototype designs of the flight-deck automation system display to achieve two primary objectives: identify information requirements for the pilot to execute 4D trajectories, and investigate usability of the flight-deck display. More specifically, the findings help to identify the information requirements for the pilots, to discover issues related to the general interface design and properties of the display, and to recommend specific improvements that could be made to the design of the display and how it communicates information to the user.

Air Traffic Estimation and Decision Support for Stochastic Flow Management

** † ‡ Development of a decision support system that uses real-time track data to estimate statistical parameters describing the stochastic traffic flow is described. Modern statistical decision theory is applied to optimize traffic flow. An advanced estimation algorithm provides the parameter estimates based on queuing network models of traffic flow. A hypothesis testing approach is developed for triggering traffic flow management initiatives in the terminal area, and a stochastic quadratic programming methodology is advanced to achieve flow control objectives such as runway load balancing. The use of this methodology is demonstrated using multi-day track data in the San Francisco terminal area. It is shown that the methodology can correctly identify the need for restricting the traffic flow into the terminal area, and provide decision support to balance the traffic flow at the runways under uncertain traffic flow conditions. The present approach can be extended to the creation of decision support tools for a wide variety of stochastic air traffic flow control situations.

Helicopter Trajectory Planning using Optimal Control Theory

A methodology for optimal trajectory planning useful in the nap-of-the-earth guidance of helicopters is presented. This approach employs an adjoint-control transformation along with a one-dimensional search scheme for generating the optimal trajectories. In addition to being useful for helicopter nap-of-the-earth guidance, the trajectory planning solution is of interest in several other contexts such as robotic vehicle guidance and terrain following guidance for cruise missiles and aircraft. A distinguishing feature of the present research is that the terrain constraint and the threat envelopes are incorporated in the equations of motion. Second order necessary conditions are examined.