Dominick Andrisani

A Nonlinear Tracker Using Attitude Measurements

The subject of this paper involves tracking the present position of a maneuvering aircraft as well as predicting its future position. A tracking filter is developed that uses aircraft attitude angles (yaw, pitch, roll) in addition to the usual radar measurements. Computer simulation of tracker performance when tracking violently maneuvering aircraft indicates that a dramatic improvement is obtained by using attitude information. The approach taken is to develop a 12-or 15-state extended Kalman filter that models both translational and rotational degrees of freedom. By measuring and estimating attitude it is possible to approximately determine the magnitude and direction of the force system acting on the vehicle and therefore determine vehicle linear acceleration. Knowledge of acceleration is then used to improve the estimate of present and future position of the vehicle being tracked. Simulation of a T-38 aircraft performing a 5 g turn indicates that the new tracker produces maximum trajectory prediction errors that are 36 percent of the errors experienced by more conventional trackers.

Intent Inference with Path Prediction

In todays air-traffic management system, the intent of an aircraft is revealed in its flight plan and a pilots adherence to published navigation routes. In a future free-flight environment, aircraft might be allowed to fly any route they choose. Intent will likely be broadcast in the form of trajectory change points (TCPs), for instance, up to four TCPs in an automatic dependent surveillance-broadcast message. However, if broadcast TCPs do not accurately represent intent, do not exist, or do not get received, then a nearby aircraft or ground-monitoring system has a need to infer the pilots intent in real time. In this paper, a method of inferring intent, which is based on artificial intelligence models and a process for best fitting an intent model to observed aircraft motion, is investigated. Horizontal, vertical, and speed dimensions are first investigated independently, and then combined, including sequences of actions, to fully explain the three-dimensional guidance and navigation plan of an aircraft. Finally, the inferred intent is used as a basis to predict a path from the current location of the aircraft into the future.

A nonlinear helicopter tracker using attitude measurements

Extended-Kalman-filter-based trackers are discussed for maneuvering helicopters that use body angle and rotor tip-path-plane angle measurements in addition to the usual radar position measurements. Improvements were found in tracker performance when the body rotation and rotor tip-path-plane degrees of freedom were modeled within the extended Kalman filter. Tracker performance was further improved when measurements of body angles and rotor tip-path-plane angles were made available to the tracker. >

Intelligent path prediction for vehicular travel

A method for predicting the motion of an observed vehicle by reasoning about the actions taken by the operator of the vehicle is presented. Reasoning about action is pursued by investigating decision-making strategies that might replicate the motion of the vehicle. Tracking a vehicle performing a transit mission, a mission that proceeds from a start location to a goal location guided by an intelligent planning strategy, is considered. The start location is assumed to be known, the goal location is assumed to be in a given set of candidate goal locations, and an intelligent planning criterion is assumed to be guiding the vehicle. Given the history of the observed vehicles path, the objectives are to select the cost criterion that best explains the observed motion, predict the goal location of the vehicle, and predict the future path leading to the goal location. In solving this problem, search pointer information provided by reverse graph searches is exploited. >

Navigation path planning for autonomous aircraft: Voronoi diagram approach

The present technique for generating a search graph depicting topologically unique paths around mountain boundaries at constant altitudes involves a description of mountain boundaries as polygons; the search graph is then generated on the basis of a geometric construct. All nodes and arcs of the search graph are guaranteed to lie in free space, thereby ensuring an autonomous aircrafts avoidance of mountain obstacles. The solution path is generated by searching the graph for the optimal path from a start location to a finish location.

Intelligent /spl epsiv/-optimal path prediction for vehicular travel

This paper addresses the problem of predicting the path of a vehicle performing a transit mission. Such a mission proceeds from a start location to a goal location guided by an intelligent planning strategy. Given the history of a path from a start location to a current location, the objectives are: 1) to estimate the cost criterion guiding the travel; 2) to predict the goal location; and 3) to predict the future path leading to the predicted goal location. First, a cost criterion explaining the decision-making strategy of the observed vehicle is estimated using a correlation measure comparing the observed path data to optimal path search information. This correlation is expressed in terms of the tolerance /spl epsiv/ of an /spl epsiv/-optimal path. Next, a region of plausible goal locations is predicted assuming that the vehicle will proceed using either optimal decisions or /spl epsiv/-optimal decisions in the future. The predicted goal location of the vehicle is determined by selecting the point in the region of plausible goal locations that has the highest heuristic merit, as determined by a proposed ranking system. Finally, from auxiliary search information, the future path is predicted. This problem is generalized to predicting the future path of a point vehicle traveling in an arbitrary dimensional space. >

Attitude based trackers for airplane, helicopter and ground targets

Abstract A class of aircraft and ground‐vehicle trackers is described that uses imaging sensors and image processing techniques to increase the tracking and prediction accuracy of target tracking systems. The image information is used to obtain the roll, pitch and yaw orientation angles of the target, and this aspect data is shown to be a significant supplement to the position data used by present‐day systems. This paper demonstrates that target aspect angle information as obtained from an image processing system is important in target tracking for the following reasons: for aircraft targets, aspect angle information is directly related to the magnitude and direction of the target acceleration vector; for ground targets, aspect angle gives direct information about the direction of the target velocity vector. Equations of motion are presented that specifically show the relationships between aspect angles and vehicle motion for fixed‐wing aircraft, helicopters, and ground vehicles. Sample results show that ...

Flexible Tube-Based Network Control

One of the most restrictive aspects in today’s Air Traffic Management (ATM) system is that aircraft are still largely limited to flying routes defined by fixed, ground-based navaids. With current air travel experiencing increasing amount of delay, it is evident that this inflexible jet route system will not be able to handle future demand, especially when jet routes get closed by hazardous weather constraints. However, not having any route structure in the AS might not be a viable approach either as it could lead to high complexity and low traffic pattern predictability. For use in the ext Generation ATM system ( extGen), the etwork Flow Organizer ( FO) has been designed as a Traffic Management Initiative (TMI) to control the topology of the air traffic flow network and its flow properties. The FO alleviates en route congestion by creating airspace capacity through dense, automatically monitored traffic flows. This is in contrast to other TMIs that restrict capacity, such as Airspace Flow Program, miles-in-trail, ground delays and ground stops. The FO forms and dissolves flows based on demand and the necessity to resolve demand-capacity imbalances, thus providing structure only when needed without unnecessarily constraining traffic. Such flows allow parallel lanes of traffic, creating high traffic throughput with low complexity and workload. The flows are dynamically relocated throughout the day to be safe from weather hazards and to avoid Special Use Airspace. A concept for protected slot templates is established to allow conflict free intersection of flows and turning at intersections.

Longitudinal Flying Qualities Prediction for Nonlinear Aircraft

An analysis tool is presented that predicts longitudinal e ying qualities of a piloted aircraft subject to elevator rate limiting and nonlinear stick gradient. The method produces an explicit mathematical pilot model for the pitch attitude tracking task. By performing pilot-in-the-loop simulation, e ying qualities metrics are computed for evaluationofthelevelof e ying qualities.Theproposedmethodisvalidated using thee ightexperimentcalledHAVE LIMITS e own at the U.S. Air Force Test Pilot School. Good agreement was obtained between our analytical e ying qualities prediction and Cooper ‐Harper pilot ratings obtained in-e ight for elevator rate limits of 10 ‐157 deg/s.

Constant gain analysis for discrete tracking filters

An analysis of discrete constant gain alpha - beta - gamma tracking filters is presented. Through the use of a symbolic manipulation program, a steady-state closed-form solution is obtained for key error covariance elements. This in turn allows for a straight-forward calculation of the tracking filter gains without resorting to solving a discrete matrix Ricatti equation until steady-state values have been achieved. Gain variation as a function of process noise, measurement noise, and sampling time is also investigated.<<ETX>>