Realistic Maneuvers Research Articles

Cognitive Workload of Tugboat Captains in Realistic Scenarios: Adaptive Spatial Filtering for Transfer Between Conditions.

Changing and often class-dependent non-stationarities of signals are a big challenge in the transfer of common findings in cognitive workload estimation using Electroencephalography (EEG) from laboratory experiments to realistic scenarios or other experiments. Additionally, it often remains an open question whether actual cognitive workload reflected by brain signals was the main contribution to the estimation or discriminative and class-dependent muscle and eye activity, which can be secondary effects of changing workload levels. Within this study, we investigated a novel approach to spatial filtering based on beamforming adapted to changing settings. We compare it to no spatial filtering and Common Spatial Patterns (CSP). We used a realistic maneuvering task, as well as an auditory n-back secondary task on a tugboat simulator as two different conditions to induce workload changes on professional tugboat captains. Apart from the typical within condition classification, we investigated the ability of the different classification methods to transfer between the n-back condition and the maneuvering task. The results show a clear advantage of the proposed approach over the others in the challenging transfer setting. While no filtering leads to lowest within-condition normalized classification loss on average in two scenarios (22 and 10%), our approach using adaptive beamforming (30 and 18%) performs comparably to CSP (33 and 15%). Importantly, in the transfer from one to another setting, no filtering and CSP lead to performance around chance level (45 to 53%), while our approach in contrast is the only one capable of classifying in all other scenarios (34 and 35%) with a significant difference from chance level. The changing signal composition over the scenarios leads to a need to adapt the spatial filtering in order to be transferable. With our approach, the transfer is successful due to filtering being optimized for the extraction of neural components and additional investigation of their scalp patterns revealed mainly neural origin. Interesting findings are that rather the patterns slightly change between conditions. We conclude that the approaches with low normalized loss depend on eye and muscle activity which is successful for classification within conditions, but fail in the classifier transfer since eye and muscle contributions are highly condition-specific.

Unmanned Aerial Vehicle Mid-Air Collision Detection and Resolution Using Avoidance Maps

Collision avoidance for fixed-wing unmanned aerial vehicles (UAVs), using a novel methodology of avoidance map, is addressed in this work. Avoidance map is defined as a mapping in the control input space of a pair of UAVs, which partitions the control space into avoidance and collision regions, respectively. The choice of maneuvers to execute successful avoidance can be effectively obtained by using the avoidance map. The duration of control application is determined by a simple method that is time optimal and computationally efficient. Different versions of the map portraying the evolution of the concept are also given. Precision control, defined as a gradual reduction in control, is discussed to reduce the control input demand for the entire duration of avoidance. The concept is extended to multiple UAVs, and the additional requirement of the UAVs to return to nominal trajectory after avoidance, using Dubins paths, is also addressed. Finally, simulation results using realistic UAV models are considered, and some needed modifications to the basic avoidance strategy, made necessary by realistic maneuver models, are discussed. Several illustrative simulation results are given to support the applicability of the proposed method.

Performance analysis of α- β- γtracking filters using position and velocity measurements

This paper examines the performance of two position-velocity-measured (PVM) α- β- γ tracking filters. The first estimates the target acceleration using the measured velocity, and the second, which is proposed for the first time in this paper, estimates acceleration using the measured position. To quantify the performance of these PVM α- β- γ filters, we analytically derive steady-state errors that assume that the target is moving with constant acceleration or jerk. With these performance indices, the optimal gains of the PVM α- β- γ filters are determined using a minimum-variance filter criterion. The performance of each filter under these optimal gains is then analyzed and compared. Numerical analyses clarify the performance of the PVM α- β- γ filters and verify that their accuracy is better than that of the general position-only-measured α- β- γ filter, even when the variance in velocity measurement noise is comparatively large. We identify the conditions under which the proposed PVM α- β- γ filter outperforms the general α- β- γ filter for different ratios of noise variance in the velocity and position measurements. Finally, numerical simulations verify the effectiveness of the PVM α- β- γ filters for a realistic maneuvering target.

Sliding-Mode Propulsion-Control Tests on a Motion Flight Simulator

This paper describes a fault-tolerant sliding-mode control allocation scheme capable of coping with the loss of all control surfaces resulting from a failure of the hydraulics system, during which time the scheme only uses the engines to control the aircraft. The paper presents tests of the scheme implemented on a six-degree-of-freedom motion research flight simulator at Delft University of Technology, using a realistic maneuver involving an emergency return to a near-landing condition on a runway in response to the failure. The simulator results show that not only does the controller provide high tracking performance during nominal fault-free conditions, this performance is also maintained after the total loss of all control surfaces. This shows the capability of the proposed sliding-mode control allocation scheme to achieve and maintain desired performance levels using only propulsion by redistributing the control signals to the engines when failures occur.

A unified seakeeping and maneuvering analysis of ships in regular waves

The behavior of a ship in regular waves during maneuvering was studied by using a two-time scale model. The maneuvering analysis was based on Soding’s (Schiffstechnik 1982; 29:3–29) nonlinear slender-body theory generalized to account for heel. Forces and moments due to rudder, propeller, and viscous cross-flow follow from the state-of-the-art procedures. The developed unified theory of seakeeping and maneuvering was verified and validated for calm water by comparing it with experimental and calculated zigzag and circle maneuvers. Linear wave-induced motions and loads were determined by generalizing the Salvesen-Tuck-Faltinsen (Trans SNAME 1970; 78:250–287) strip theory. The mean second-order wave loads in incident regular deep water waves in oblique sea conditions were estimated by the potential flow theories of Faltinsen et al. (Proc 13th Symp Naval Hydrody 1980), Salvesen (Proc Intl Symp Dynam Mar Vehicl Struct Wave 1974), and Loukakis and Sclavounos (J Ship Res 1978; 22:1–19). The considered theories cover the whole range of important wavelengths. Comparisons between the different mean second-order wave load theories and available experimental data were carried out for different ship hull forms when the ship was advancing forward on a straight course. The mentioned methods have been incorporated into the maneuvering model. Their applicability from the perspective of the maneuvering ability of the selected types of ships was investigated in given wave environments. The wave conditions are valid for realistic maneuvering cases in open coastal areas. It was demonstrated that the incident waves may have an important influence on the maneuvering behavior of a ship. The added resistance, mean second-order transverse force, and yaw moment also play important roles.

Application of the Kalman-Levy Filter for Tracking Maneuvering Targets

Among target tracking algorithms using Kalman filtering-like approaches, the standard assumptions are Gaussian process and measurement noise models. Based on these assumptions, the Kalman filter is widely used in single or multiple filter versions (e.g., in an interacting multiple model (IMM) estimator). The oversimplification resulting from the above assumptions can cause degradation in tracking performance. In this paper we explore the application of Kalman-Levy filter to handle maneuvering targets. This filter assumes a heavy-tailed noise distribution known as the Levy distribution. Due to the heavy-tailed nature of the assumed distribution, the Kalman-Levy filter is more effective in the presence of large errors that can occur, for example, due to the onset of acceleration or deceleration. However, for the same reason, the performance of the Kalman-Levy filter in the nonmaneuvering portion of track is worse than that of a Kalman filter. For this reason, an IMM with one Kalman and one Kalman-Levy module is developed here. Also, the superiority of the IMM with Kalman-Levy module over only Kalman-filter-based IMM for realistic maneuvers is shown by simulation results.

Near Real-Time Simulation of Rotorcraft Acoustics and Flight Dynamics

In this paper, a near-real-time rotorcraft flight dynamics-acoustics prediction system is presented. The highfidelity PSU-WOPWOP rotor noise prediction code is coupled with the GENHEL flight simulation code, which provides low-fidelity blade loading and motion. This system is an initial step intended to investigate the feasibility of real-time rotorcraft noise prediction and to demonstrate the utility of such a system. Limited acoustic validation is shown for a contemporary-design four-bladed main rotor in level flight. A complex 80-s maneuver was used to demonstrate the potential of the coupled system. This realistic maneuver includes a climb, coordinated turn, and level flight conditions. The noise predictions show changes in main rotor noise radiation strength and directivity caused by maneuver transients, aircraft attitude changes, and the aircraft flight—but do not include the effect of blade-vortex-interaction noise. A comparison of the total noise with the thickness and loading noise components helps explain the noise directivity. The computations for a single observer were very fast, although the algorithm is not currently organized as a real-time computation.

Maneuvering performance of high-speed ships with effect of roll motion

Equations of yaw, sway, roll and rudder motions are formulated to represent realistic maneuvering behavior of high-speed ships such as destroyers. Important coupling terms between yaw, sway, roll and rudder were included on the basis of recent captive model test results of a high-speed ship. A series of computer runs was made by using equations of yaw, sway, roll and rudder motions. Results indicate substantial coupling effects between yaw, roll, and rudder, which introduce changes in maneuvering characteristics and reduce course stability in high-speed operation. These effects together with relatively small GM (which is typical for certain high-speed ships) produce large rolling motions in a seaway as frequently observed in actual operations. Results of digital simulations and captive model tests clearly indicate the major contributing factors to such excessive rolling motions at sea.

Representation of Realistic Evasive Maneuvers by the Use of Shaping Filters

Shaping filters can be used in the analysis of physical systems because they allow a system with a random input to be replaced by an augmented system (the original system plus the shaping filter) excited only by the white noise. This paper shows how shaping filters can be used to represent various realistic aircraft evasive maneuver policies. The shaping filter approach leads to efficient methods of performance evaluation without resorting to Monte Carlo techniques. The effectiveness of various realistic maneuver policies are compared in a simplified example in which the pursuing missile employs proportional navigation guidance.