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The feedback upon which operators in teleoperation tasks base their control actions differs substantially from the feedback to the driver of a vehicle. On the one hand, there is often a lack of sensory information; on the other hand, there is additional status information presented via the visual channel. Haptic feedback could be used to unload the visual channel and to compensate for the lack of feedback in other modalities. For collision avoidance, haptic feedback could provide repulsive forces via the control inceptor. Haptic feedback allows operators to interpret the repulsive forces as impedance to their control deflections when a potential for collision exists. Haptic information can be generated from an artificial force field (AFF) that maps environment constraints to repulsive forces. This paper describes the design and theoretical evaluation of a novel AFF, i.e., the parametric risk field, for teleoperation of an uninhabited aerial vehicle (UAV). The field allows adjustments of the size, shape, and force gradient by means of parameter settings, which determine the sensitivity of the field. Computer simulations were conducted to evaluate the effectiveness of the field for collision avoidance for various parameter settings. Results indicate that the novel AFF more effectively performs the collision avoidance function than potential fields known from literature. Because of its smaller size, the field yields lower repulsive forces, results in less force cancellation effects, and allows for larger UAV velocities. This indicates less operator control demand and more effective UAV operations, both expected to lead to lower operator workload, while, at the same time, increasing safety.

In a free-flight airspace environment, pilots have more freedom to choose user-preferred trajectories. An onboard pilot support system is needed that exploits travel freedom while maintaining spatial separation with other traffic. Ecological interface design is used to design an interface tool that assists pilots with the tactical planning of efficient conflict-free trajectories toward their destination. Desired pilot actions emerge from the visualization of workspace affordances in terms of a suitable description of aircraft (loco)motion. Traditional models and descriptions for aircraft motion cannot be applied efficiently for this purpose. Through functional modeling, more suitable locomotion models for trajectory planning are analyzed. As a result, a novel interface, the state vector envelope, is presented that is intended to provide the pilot with both low-level information, allowing direct action, and high-level information, allowing conflict understanding and situation awareness.

We propose a novel gaze-control model for detecting objects in images. The model, named act-detect, uses the information from local image samples in order to shift its gaze towards object locations. The model constitutes two main contributions. The first contribution is that the model’s setup makes it computationally highly efficient in comparison with existing window-sliding methods for object detection, while retaining an acceptable detection performance. act-detect is evaluated on a face-detection task using a publicly available image set. In terms of detection performance, act-detect slightly outperforms the window-sliding methods that have been applied to the face-detection task. In terms of computational efficiency, act-detect clearly outperforms the window-sliding methods: it requires in the order of hundreds fewer samples for detection. The second contribution of the model lies in its more extensive use of local samples than previous models: instead of merely using them for verifying object presence at the gaze location, the model uses them to determine a direction and distance to the object of interest. The simultaneous adaptation of both the model’s visual features and its gaze-control strategy leads to the discovery of features and strategies for exploiting the local context of objects. For example, the model uses the spatial relations between the bodies of the persons in the images and their faces. The resulting gaze control is a temporal process, in which the object’s context is exploited at different scales and at different image locations relative to the object.

In an attempt to model regular variations of the ionosphere, the least-squares harmonic estimation is applied to the time series of the total electron contents (TEC) provided by the JPL analysis center. Multivariate and modulated harmonic estimation spectra are introduced and estimated for the series to detect the regular and modulated dominant frequencies of the periodic patterns. Two significant periodic patterns are the diurnal and annual signals with periods of 24/n hours and 365.25/n days (n = 1, 2, …), which are the Fourier series decomposition of the regular daily and yearly periodic variations of the ionosphere. The spectrum shows a cluster of periods near 27 days, thereby indicating irregularities at this solar cycle period. A series of peaks, with periods close to the diurnal signal and its harmonics, are evident in the spectrum. In fact, the daily signal harmonics of xi = 2pi are modulated with the annual signal harmonics of xj = 2pj/365.25 as xijM = 2pi(1 ± j/365.25i). Among them, at low and midlatitudes, the largest variations belong to the diurnal signal modulated to the semiannual signal. Some preliminary results on the modulated part are presented. The maximum ranges of the modulated daily signal are ±15 TECU and ±6 TECU at high and low solar periods, respectively. A model consisting of purely harmonic functions plusmodulated ones is capable of studying known regular anomalies of the ionosphere, which is currently in progress

This paper aims to contribute to research on biologically inspired micro air vehicles in two ways: (i) it explores a novel repertoire of behavioral modules which can be controlled through finite state machines (FSM) and (ii) elementary movement detectors (EMD) are combined with a center/surround edge detection algorithm to yield improved edge information used for object detection. Both methods will be assessed in the context of the IMAV 2011 pylon challenge.

Personal air transportation utilizing small aircraft is a market that is expected to grow significantly in the near future. However, seventy times more accidents occur in this segment as compared with the commercial aviation sector. The majority of these accidents is related to handling and control problems. In commercial aviation, Fly-By-Wire (FBW) technology is used to prevent these types of accidents. Instead of downscaling advanced and high-cost FBW platforms, a low-cost solution should be considered for the general aviation market. In the European project “Small Aircraft Future Avionics Architecture”, a FBW platform is developed specifically for small aircraft. In this environment, Flight Control Law (FCL) designs are needed that have robustness against model uncertainties, sensor bias, sensor noise and time delays, while being fast and accurate enough to accommodate the relatively agile dynamics of a small aircraft. FCL designs that meet these requirements are called practical FCL designs in this thesis. Based on a dynamic model of a Diamond DA 42 and a description of the dynamic properties of the FBW platform, two different FCL designs are synthesized and analyzed in this thesis. The first design uses classical control theory and the second design uses a newly developed nonlinear design method, based on backstepping, singular perturbation theory and approximate dynamic inversion. This latter method, called Sensor-Based Backstepping (SBB), uses no dynamic model information and relies solely on measurements. Both FCL designs are compared on sensitivity to parametric uncertainty, sensor noise, disturbances, time delays, handling qualities, design effort, certifiably and the option to add flight envelope protection. In the scope of this thesis, SBB is selected as the preferred FCL design. This method produces good aircraft responses without knowing the exact dynamic behavior of the aircraft during FCL synthesis, as long as the system is minimum phase, controllable and sufficiently time-scale separated.

In many cockpits, control display units (CDUs) are vital input and information devices. In order to improve the usability of these devices, Barco, in cooperation with TU-Delft, created a touch screen control unit (TSCU), consisting of a high-quality multi-touch screen. The unit fits in the standard dimensions of a conventional CDU and is thus suitable for both retrofit and new installations. The TSCU offers two major advantages. First, the interface can be reconfigured to enable consecutive execution of several tasks on the same display area, allowing for a more efficient usage of the limited display real-estate as well as a potential reduction of cost. Secondly, advanced graphical interface design, in combination with multi-touch gestures, can improve human-machine interaction. To demonstrate the capabilities of this concept, a graphical software application was developed to perform the same operations as a conventional CDU, but now using a direct manipulation interface (DMI) of the displayed graphics. The TSCU can still be used in a legacy CDU mode, displaying a virtual keyboard operated with the touch interface. In addition, the TSCU could be used for a variety of other cockpit functions. The paper concludes with a report of pilot and non-pilot feedback.

The sensor-based approach of Incremental Backstepping is applied to flight control law design in this research project. It allows the usage of the same control law on different types of aircraft without the need for redesign. Apart from full state availability, the derivation of Incremental Backstepping assumes instantaneous control action. Due to actuator lags and delays, the implementation of control commands cannot necessarily be considered instantaneous. This mitigates the stability guarantee provided by Lyapunov theory. Therefore, a novel technique to estimate the time delay margins of the Incremental Backstepping controlled systems is proposed in the thesis. This provides an important stability measure for possible certification and widens the application range of Incremental Backstepping. This simple, yet effective, Lyapunov-based control technique shows positive robustness properties with respect to model uncertainties, unknown parameters, external disturbances and time delay effects. It is applied to the DA 42 aircraft as a (pilot-in-the-loop) rate controller in the scope of this thesis. The implementation requires measurements of the aircrafts angular accelerations and control surface deflections. If the latter is not available, it is shown that filters can still be used in the control system. However, the usage of filters mitigates the highly favorable robustness properties of the closed-loop system. Moreover, a controller evaluation strategy is proposed. It rates the performance and stability properties of the Incremental Backstepping controlled system in terms of the flight control system requirements. Evaluation of the Incremental Backstepping controller shows allowable input multiplicative uncertainties of up to 40% of the nominal value at the worst-case excitation frequency for a controller update rate of 100Hz. When no reference shaping is applied, the handling qualities of the incremental rate controller show to be less desirable than that of a conventional linear controller designed specifically for the DA 42. However, it is possible to improve handling characteristics by reference shaping. Furthermore, the handling characteristics of the incremental controller remain fairly constant along the flight envelope and in adverse flight conditions.

In order to meet requirements in terms of robustness, stability, and performance for future generations of advanced attitude control systems, a sensor-based approach using Incremental Backstepping control is developed and proposed in this thesis. Assuming full state availability and fast control action, the resulting time-scale separation between the state of the system and the state of the controller allows to consider an incremental form of the attitude dynamics, where backstepping controllers can be designed to achieve stability and convergence with incremental inputs. This results in integral-control action where information of angular acceleration and actuator output measurements is required. The robustness and the full potential of Incremental Backstepping are evidenced in face of external disturbances, uncertainties, and unknown parameters. External disturbances are well suppressed in contrast with conventional backstepping and Lyapunov-based (non)linear controllers. Furthermore, the attitude stabilization results to be insensitive to parametric uncertainties and robust against model uncertainties. However, this comes at the expense of higher control effort. Moreover, with the influence of model and parametric uncertainties the resulting closed-loop dynamic performance can be better accounted for by studying the convergence and stability properties in terms of Lyapunov theory. This methodology results in a simple, yet effective, family of robust nonlinear attitude controllers which aims to meet demanding requirements in terms of robustness, stability and performance, which in turn, close the gap towards the development of future advanced attitude control systems.