Olaf Stroosma

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

Fault Tolerant Sliding Mode Control Design with Piloted Simulator Evaluation

This paper considers sliding mode allocation schemes for fault tolerant control. The schemes allow redistribution of the control signals to the remaining functioning actuators when a fault or failure occurs. The paper analyzes the schemes and determines conditions under which closed-loop stability is retained for a certain class of faults and failures. It is shown that faults and even certain total actuator failures can be handled directly without reconfiguring the controller. The results obtained from implementing the controllers on a research flight simulator, configured to represent a B747 aircraft, show good performance in both nominal and failure scenarios, even in wind and gust conditions.

Measuring the Performance of the SIMONA Research Simulator's Motion System

A hardware and software system is presented that is used to measure the motion performance of Delft University’s SIMONA Research Simulator. It uses the simulator’s operational software environment and an onboard Inertial Measurement Unit to measure motion performance metrics that are based on AGARD report no. 144. The metrics can be used to assess the simulator’s motion capabilities, but can also serve to evaluate different control algorithms for the motion base. An example of this last use is presented in this paper. The measured data shows that the effort put into the lightweight design of the simulator cab and the advanced motion control algorithms, has resulted in good motion performance in terms of time delay and bandwidth. Also, increased motion performance is expected to be possible with further tuning of the control algorithms and enhancements in the driving software.

Evaluation of Vestibular Thresholds for Motion Detection in the SIMONA Research Simulator

This paper presents the results of an experiment in which motion perception thresholds in the SIMONA Research Simulator are measured. Selfmotion perception is the result of perceived visual, vestibular, tactile, and proprioceptive cues. In this experiment, motion perception is based on vestibular cues only. Below a certain value, the vestibular cues will not be perceived by humans. This value is called the threshold for motion perception. Two different thresholds exist, an upper threshold and a lower threshold. The upper threshold is the stimulus value at which the stimulus switches from not perceived to perceived. The lower threshold is the value the stimulus reaches when the stimulus changes from perceived to not perceived, i.e. with decreasing stimulus amplitude. Knowledge of these thresholds is important for the use of motion simulators. The motions presented to the subject in this experiment are linear or angular accelerations in all six motion directions. The results from the experiment correspond well with known motion perception thresholds and vestibular models.

OPTIMISATION OF THE SIMONA RESEARCH SIMULATOR'S MOTION FILTER SETTINGS FOR HANDLING QUALITIES EXPERIMENTS

The first handling qualities experiment to be performed in the SIMONA Research Simulator (SRS) is a replication of evaluations previously performed in the U.S. Air Force Total In-Flight Simulator (TIFS) and NASA Ames Vertical Motion Simulator (VMS). In order to match the results from the TIFS and VMS as closely as possible, great attention has been given to providing the pilots the salient effects of the cues available in the TIFS and VMS. This required the optimisation of the SRSs motion filters for the specific task and vehicle used in the previous evaluations. An approach to optimise the filters was developed that reduces qualitative piloted evaluation time through the use of off-line simulation providing a graphical representation of allowable motion filter settings in this task. A limited flying qualities experiment was performed to appraise this design approach and to select an optimised motion filter for the subsequent evaluations in the SRS. Initial results demonstrated the successful application of the filter design approach, and provided insight into its potential for future application. The approach shows promise for aiding future researchers with less expertise in the field of motion cueing.

Evaluation of a Sliding Mode Fault Tolerant Controller for the EL-AL Incident

This paper presents piloted flight simulator results associated with the EL-AL flight 1862 scenario using a model reference–based sliding mode control allocation scheme for fault tolerant control. The proposed controller design was carried out without any knowledge of the type of failure, and in the absence of any fault detection and isolation strategy. This is motivated by the fact that the flight crew were unaware of the loss of the right engines. For this reason, the control allocation scheme which is proposed uses (fixed) equal distribution of the control signals to all actuators (for both nominal situations and when a fault or failure occurs). The paper analyzes the scheme and determines the conditions under which closed-loop stability is retained. The results represent the successful real-time implementation of the proposed controller on the SIMONA motion flight simulator configured to represent a B747 aircraft. The evaluation results from the experienced pilots show that the proposed controller has the ability to position the aircraft for landing in both a nominal and the EL-AL failure scenario. It is also shown that actuator faults and failures which occured during the EL-AL incident can be handled directly without reconfiguring the controller.

Piloted Simulator Evaluation Results of New Fault-Tolerant Flight Control Algorithm

A high fidelity aircraft simulation model, reconstructed using the Digital Flight Data Recorder (DFDR) of the 1992 Amsterdam Bijlmermeer aircraft accident (Flight 1862), has been used to evaluate a new Fault-Tolerant Flight Control Algorithm in an online piloted evaluation. This paper focuses on the piloted simulator evaluation results. Reconfiguring control is implemented by making use of Adaptive Nonlinear Dynamic Inversion (ANDI) for manual fly by wire control. After discussing the modular adaptive controller setup, the experiment is described for a piloted simulator evaluation of this innovative recon- figurable control algorithm applied to a damaged civil transport aircraft. The evaluation scenario, measurements and experimental design, as well as the real-time implementation are described. Finally, reconfiguration test results are shown for damaged aircraft models including component as well as structural failures. The evaluation shows that the FTFC algorithm is able to restore conventional control strategies after the aircraft configuration has changed dramatically due to these severe failures. The algorithm supports the pilot after a failure by lowering workload and allowing a safe return to the airport. For most failures, the handling qualities are shown to degrade less with a failure than the baseline classical control system does.

Piloted Simulator Evaluation of New Fault-Tolerant Flight Control Algorithms for Reconstructed Accident Scenarios

A research initiative within the framework of the Group for Aeronautical Research and Technology in Europe (GARTEUR) co-operation program examined the application of multiple fault-tolerant flight control (FTFC) algorithms in a realistic aircraft accident scenario. An aircraft model, reconstructed using the Digital Flight Data Recorder (DFDR) of the 1992 Amsterdam Bijlmermeer aircraft accident (Flight 1862), was used to evaluate the algorithms in an offline benchmark and an online piloted evaluation. This paper focuses on the experiment development for a piloted simulator evaluation of innovative reconfigurable control algorithms applied to a damaged civil transport aircraft. The evaluation scenario, measurements and experimental design, as well as the real-time implementation are described. The evaluation showed that the FTFC algorithms were able to restore conventional control strategies after the aircraft configuration has changed dramatically due to severe failures. The algorithms supported the pilot after a failure by lowering workload and allowing a safe return to the airport. For some failures, the handling qualities were shown to degrade less with a failure than the baseline classical control system.

Real-Time Implementation of an ISM Fault-Tolerant Control Scheme for LPV Plants

This paper proposes a fault-tolerant control (FTC) scheme for linear parameter-varying (LPV) systems based on integral sliding modes (ISMs) and control allocation (CA) and describes the implementation and evaluation of the controllers on a 6-degree-of-freedom research flight simulator called SIMONA. The FTC scheme is developed using an LPV approach to extend ideas previously developed for linear time-invariant systems, in order to cover a wide range of operating conditions. The scheme benefits from the combination of the inherent robustness properties of ISMs (to ensure sliding occurs throughout the simulation) and CA, which has the ability to redistribute control signals to all available actuators in the event of faults/failures.

Piloted Sliding Mode FTC Simulator Evaluation for the ELAL Flight 1862 Incident

This paper considers a model reference based sliding mode control allocation scheme for fault tolerant control. The scheme uses equal distribution of the control signals to all actuators even when a fault or failure occurs, and assumes no FDI is available. The paper analyzes the scheme and determines conditions under which closed{loop stability is retained for a certain class of faults and failures. It is shown that faults and even certain total actuator failures can be handled directly without reconflguring the controller. The results obtained from implementing the controller on the SIMONA research ∞ight simulator, conflgured to represent a large transport aircraft under the ELAL ∞ight 1862 scenario, shows good performance in both nominal and failure scenarios.