M. M. van Paassen

Modeling Human Multimodal Perception and Control Using Genetic Maximum Likelihood Estimation

This paper presents a new method for estimating the parameters of multi-channel pilot models that is based on maximum likelihood estimation. To cope with the inherent nonlinearity of this optimization problem, the gradient-based Gauss-Newton algorithm commonly used to optimize the likelihood function in terms of output error is complemented with a genetic algorithm. This significantly increases the probability of finding the global optimum of the optimization problem. The genetic maximum likelihood method is successfully applied to data from a recent human-in-the-loop experiment. Accurate estimates of the pilot model parameters and the remnant characteristics were obtained. Multiple simulations with increasing levels of pilot remnant were performed, using the set of parameters found from the experimental data, to investigate how the accuracy of the parameter estimate is affected by increasing remnant. It is shown that only for very high levels of pilot remnant the bias in the parameter estimates is substantial. Some adjustments to the maximum likelihood method are proposed to reduce this bias.

Modeling Human Multichannel Perception and Control Using Linear Time-Invariant Models

This paper introduces a two-step identification method of human multichannel perception and control. In the first step, frequency response functions are identified using linear time-invariant models. The analytical predictions of bias and variance in the estimated frequency response functions are validated using Monte Carlo simulations of a closed-loop control task and contrasted to a conventional method using Fourier coefficients. For both methods, the analytical predictions are reliable, but the linear time-invariant method has lower bias and variance than Fourier coefficients. It is further shown that the linear time-invariant method is more robust to higher levels of pilot remnant. Finally, both methods were successfully applied to experimental data from closed-loop control tasks with pilots.

Using the SIMONA Research Simulator for Human-machine Interaction Research

The Delft University of Technology has developed a 6 degree-of-freedom flight simulator, the SIMONA Research Simulator (SRS). The design incorporates several advanced technologies, such as light-weight construction, high performance motion drive algorithms and a flexible, PC-based computer infrastructure. The simulator serves as a testbed for new technologies and as a tool for Human-Machine Interaction (HMI) research. Key components of the simulator that allow high quality Human-Machine Interaction research to be performed, are described. To ensure a sufficient level of accessibility for students and researchers, the software architecture of the SRS uses the Delft University Environment for Communication and Activation (DUECA), a middleware layer that shields the user from the complexities of the communication between PCs and the real-time scheduling of the different simulation modules. Through the use of DUECA, experiments are also easily portable between development workstations and different simulator environments. The concepts behind DUECA and its use in the research environment of SIMONA are discussed. Several research projects with the Faculty of Aerospace Engineering of the Delft University of Technology have been performed successfully using DUECA, on simulators of different fidelity, from standalone PCs, to a fixed base mockup and the SRS. __________________________________ * Associate Researcher, International Research Institute for Simulation, Motion and Navigation. Member AIAA. † Assistant Professor, Control and Simulation Division, Faculty of Aerospace Engineering. Member AIAA. ‡ Assistant Professor, Control and Simulation Division, Faculty of Aerospace Engineering. Member AIAA. INTRODUCTION Several groups within the Delft University of Technology (TU Delft) in the Netherlands have long been involved in research into flight simulation. For instance, the faculty of Design, Construction and Production has extensive experience with the design and control of hydraulic actuators for motion and control loading systems. The faculty of Aerospace Engineering has always been active in the field of modeling and simulation and has operated a threedegree-of-freedom flight simulator up until the early 1990s. At that time, a new co-operative initiative was set up to develop, build and operate an advanced sixdegree-of-freedom research flight simulator. These two faculties, together with the faculty of Information Technologies and Systems, initiated the International Research Institute for Simulation, Motion and Navigation (SIMONA). The SIMONA institute promotes fundamental and applied research in the fields of simulation technology and human-machine interaction. Available and newly generated knowledge on simulation technologies is applied to the development of the full-motion SIMONA Research Simulator (SRS, see Figure 1). This recently completed simulator stands at the heart of the SIMONA institute and provides an experimental facility for human-machine interaction research. An important aspect in both research fields is a close co-operation with industry and academia around the world. Figure 1 SIMONA Research Simulator AIAA Modeling and Simulation Technologies Conference and Exhibit 11-14 August 2003, Austin, Texas AIAA 2003-5525 Copyright

Effects of Heave Washout Settings in Aircraft Pitch Disturbance Rejection

In most moving-base flight simulators, the simulated aircraft motion needs to be filtered with motion washout filters to keep the simulator within its limited motion envelope. Translational motion in particular requires filtering, as the low frequency components of the vehicle motion tend to quickly drive simulators toward their motion bounds. Commonly, linear washout filters are therefore used to attenuate the simulated motion in magnitude and in phase. It is found in many studies that the settings of these washout filters affect pilot performance and control behavior. In most of these studies, no comparison to a case with one-to-one motion cues is performed, as a result of the limited motion envelope of the used simulators. In the current study, an experiment was performed in the SIMONA Research Simulator at Delft University of Technology to investigate the effects of heave washout settings on pilot performance and control behavior in a pitch attitude control task. In addition to rotational pitch motion, heave accelerations at the pilot station that result directly from aircraft pitch were evaluated. This heave motion component could be supplied one-to-one in the simulator due to the modest size of the aircraft model, a Cessna Citation I business jet. The experiment revealed that pilot performance and control activity both increased significantly with increasing heave motion fidelity. An analysis of pilot control behavior using pilot models indicated that the enhanced performance was caused by an increase in the magnitude with which pilots responded to visual and physical motion stimuli and a decrease in the amount of visual lead that was generated by the pilots.

Multimodal Pilot Control Behavior in Combined Target-Following Disturbance-Rejection Tasks

Investigating how humans use their perceptual modalities while controlling a vehicle is important for the design of new control systems and the optimization of simulator motion cueing. For the identification of separate pilot response functions to the different perceived cues, multiple forcing functions need to be inserted into the manual control loop. An example of a task with multiple forcing functions is a combined target-following disturbance-rejection task, where a target and disturbance signal are used to separate the human visual and vestibular motion responses. The use of multiple forcing functions, however, also affects the nature of the control task and how the motion cues are used by the pilot to form a proper control action. This paper presents the results of an experiment where possible effects of using multiple forcing functions on pilot control behavior in an aircraft pitch control task are investigated. The results indicate that pilot performance and control activity are significantly lower when the relative power of the target forcing function is increased. This is caused by a significant change in multimodal pilot control behavior. With an increase in relative target power, the visual-perception gain is reduced and the visual time delay becomes higher. The motion-perception gain reduces if both forcing functions have significant power. It is also found that multimodal pilot control behavior in a pure target or disturbance task can be analyzed by adding a small additional disturbance or target signal, respectively. In this case, the effects on control behavior are found to be minimal, while still being able to accurately estimate the parameters of the multichannel pilot model.

Design of an airborne three-dimensional separation assistance display

In the context of the NextGen and SESAR future airspace programmes, this paper describes a concept for an Airborne Separation Assurance (ASAS) display, that is designed to aid pilots in their task of self-separation, by visualizing the possibilities for conflict resolution that the airspace provides. This work is part of an ongoing research towards an ecological design of a separation assistance interface that can present all the relevant properties of the spatio-temporal separation problem. A work-domain analysis is described from which several perspective projections of traffic properties and travel constraints are derived. A display concept is proposed that presents heading and altitude action possibilities in a flight-path angle - track angle action space. Key issues in the current design are discussed, with recommendations for future work.

A Method to Measure the Relationship Between Biodynamic Feedthrough and Neuromuscular Admittance

Biodynamic feedthrough (BDFT) refers to a phenomenon where accelerations cause involuntary limb motions, which can result in unintentional control inputs that can substantially degrade manual control. It is known that humans can adapt the dynamics of their limbs by adjusting their neuromuscular settings, and it is likely that these adaptations have a large influence on BDFT. The goal of this paper is to present a method that can provide evidence for this hypothesis. Limb dynamics can be described by admittance, which is the causal dynamic relation between a force input and a position output. This paper presents a method to simultaneously measure BDFT and admittance in a motion-based simulator. The method was validated in an experiment. Admittance was measured by applying a force disturbance signal to the control device; BDFT was measured by applying a motion disturbance signal to the motion simulator. To allow distinguishing between the operators responses to each disturbance signal, the perturbation signals were separated in the frequency domain. To show the impact of neuromuscular adaptation, subjects were asked to perform three different control tasks, each requiring a different setting of the neuromuscular system (NMS). Results show a dependence of BDFT on neuromuscular admittance: A change in neuromuscular admittance results in a change in BDFT dynamics. This dependence is highly relevant when studying BDFT. The data obtained with the proposed measuring method provide insight in how exactly the settings of the NMS influence the level of BDFT. This information can be used to gain fundamental knowledge on BDFT and also, for example, in the development of a canceling controller.

Pilot equalization in manual control of aircraft dynamics

In continuous manual control tasks, pilots adapt their control strategy to the dynamics of the controlled element to yield adequate performance of the combined pilot-vehicle system. For a controlled element representing the linearized pitch dynamics of a small jet aircraft, the pilot models described in literature were found to lack the required freedom in the pilot equalization term to accurately model the adopted pilot compensation. An additional lead term in the pilot equalization transfer function was found to significantly increase the accuracy in modeling manual control behavior of aircraft pitch dynamics.

Comparing Multimodal Pilot Pitch Control Behavior Between Simulated and Real Flight

In order to improve the tuning process of flight simulator motion cueing filters and support the development of objective simulator motion cueing requirements, a better understanding of how multimodal pilot control behavior is affected by simulator motion fidelity is required. To this end, an experiment was performed where seven pilots performed a pitch target-following disturbance-rejection task in a simulator under four different motion cueing settings, in addition to performing the task in a real aircraft, which served as the baseline condition. Differences between the simulator and aircraft experiment setup were minimized. Small remaining differences in the display and the sidestick setup slightly affected the experiment dependent measures. However, the effects introduced by the motion cueing settings were far more apparent. When motion fidelity was increased to full aircraft motion, pilots were able to increase performance in attenuating the disturbance signal significantly. In addition, for increased motion fidelity, a change in multimodal pilot control behavior was observed by a decrease in pilot visual lead, while visual and vestibular perception delays increased. Pilot performance and control behavior in the simulator condition with full pitch motion and filtered pitch and c.g. heave motion was most similar to the in-flight condition.

Design and Simulator Evaluation of an Ecological Synthetic Vision Display

A synthetic vision display is generally believed to support pilot terrain awareness. Many studies have shown, however, that the bias in perspective views can cause pilots to make judgment errors regarding the relative location, height, and ultimately the avoidance of terrain obstacles. Therefore, alerting systems are required to keep pilots at safe distances from the terrain. These systems provide explicit guidance commands to circumvent terrain conflicts, which is far from optimal regarding pilot terrain awareness as it fails to present the rationale of the terrain separation problem. Consequently, this can affect the trust in and the reliance on these systems and pose a potential safety risk, especially in events or situations unfamiliar to the alerting system. This paper presents the design and evaluation of an extension to a synthetic vision display that aims to make the constraints of the alerting automation more transparent in order to help pilots better understand why, how, and when they should act. A pilot-in-the-loop experiment, using 16 glass-cockpit pilots in a fixed-based flight simulator, showed that the constraint-based overlays indeed improved the overall pilot terrain awareness compared to a command-based display. The decision-making only improved in the unanticipated events introduced in the experiment. The utility of the energy angle was found to be important for recognizing the offnormal events and to prevent terrain crashes. However, the pilot response time, flight safety in terms of low-altitude flying, and pilot workload are better when using the command display. This indicates that a last-resort alerting and advisory system would still be required in operations at the periphery of safe system performance.