Overcoming non-determinism in testing smart devices: how to build models of device behaviour

Justification of smart instruments has become an important topic in the nuclear industry. In practice, however, the publicly available artefacts are often the only source of information about the device. Therefore, in many cases independent black-box testing may be the only way to increase the confidence in the device. In this paper we provide a set of recommendations, which we consider to be the best practices for performing black-box assessments. We present our method of testing smart instruments, in which we use the publicly available artefacts only. We present a test harness and describe a method of test automation. We focus on the analysis of test results, which is made particularly complex by the inherent non determinism in the testing of analogue devices. In the paper we analyse the sources of non-determinism, which for instance may arise from inaccuracy in an analogue measurement made by the device when two alternative actions are possible. We propose three alternative ideas on how to build models of device behaviour, which can cope with this kind of non-determinism. We compare and contrast these three solutions, and express our recommendations. Finally, we use a case study, in which a black box assessment of two similar smart instruments is performed to illustrate the differences between the solutions

Mid-Lift-To-Drag Ratio Rigid Vehicle 6-DOF EDL Performance Using Tunable Apollo Powered Guidance

The Mid-Lift-to-Drag ratio Rigid Vehicle (MRV) is a candidate in the NASA multi-center effort to determine the most cost effective vehicle to deliver a large-mass payload to the surface of Mars for a human mission. Products of this effort include six-degree-of-freedom (6DoF) entry-to-landing trajectory performance studies for each candidate vehicle. These high fidelity analyses help determine the best guidance and control (G&C) strategies for a feasible, robust trajectory. This paper presents an analysis of the MRV's G&C design by applying common entry and descent associated uncertainties using a Fully Numerical Predictor-corrector Entry Guidance (FNPEG) and tunable Apollo powered descent guidance

S-4B orbital workshop attitude control system study

Saturn S-4B orbital workshop attitude control system analysi

On the Implementation of OPF-Based Setpoints for Active Distribution Networks

In the context of active distribution networks, AC Optimal Power Flow (OPF) has shown great potential to calcu-late setpoints for controllable devices. Although considerable literature exists, temporal aspects that may affect the actual exe-cution of these setpoints are rarely investigated. Due to the di-verse operating characteristics of controllable devices (i.e., de-lays, ramp rates and deadbands), when these setpoints are exe-cuted by multiple devices without adequate considerations, the resulting outcome can differ drastically from what is expected; leading to violations of network constraints and excessive control actions. Therefore, this work proposes a series of necessary adap-tations within the controllers of existing devices as well as in the OPF formulation to cater for the diversity in operating charac-teristics, ensuring that calculated setpoints are adequately im-plemented by controllable devices. This involves the direct con-trol of conventional devices and enforcing a new ramping behav-ior for inverter-interfaced devices. Furthermore, a linear, mixed-integer formulation is proposed to handle discrete devices and improve scalability in large networks. Co-simulation results (us-ing a UK test network with the objective of maximizing renewa-ble energy production and considering 1s time-step) demonstrate that, by catering for the operating characteristics of controllable devices, the expected outcome from OPF-based setpoints can be achieved

Space station structural dynamics/reaction control system interaction study

The performance of the Reaction Control System is impacted by the extreme flexibility of the space station structure. The method used to analyze the periodic thrust profile of a simple form of phase plane logic is presented. The results illustrate the effect on flexible body response of the type of phase plane logic utilized and the choice of control parameters: cycle period and attitude deadband

Orion Orbit Control Design and Analysis

The analysis of candidate thruster configurations for the Crew Exploration Vehicle (CEV) is presented. Six candidate configurations were considered for the prime contractor baseline design. The analysis included analytical assessments of control authority, control precision, efficiency and robustness, as well as simulation assessments of control performance. The principles used in the analytic assessments of controllability, robustness and fuel performance are covered and results provided for the configurations assessed. Simulation analysis was conducted using a pulse width modulated, 6 DOF reaction system control law with a simplex-based thruster selection algorithm. Control laws were automatically derived from hardware configuration parameters including thruster locations, directions, magnitude and specific impulse, as well as vehicle mass properties. This parameterized controller allowed rapid assessment of multiple candidate layouts. Simulation results are presented for final phase rendezvous and docking, as well as low lunar orbit attitude hold. Finally, on-going analysis to consider alternate Service Module designs and to assess the pilot-ability of the baseline design are discussed to provide a status of orbit control design work to date

Pathfinder autonomous rendezvous and docking project

Capabilities are being developed and demonstrated to support manned and unmanned vehicle operations in lunar and planetary orbits. In this initial phase, primary emphasis is placed on definition of the system requirements for candidate Pathfinder mission applications and correlation of these system-level requirements with specific requirements. The FY-89 activities detailed are best characterized as foundation building. The majority of the efforts were dedicated to assessing the current state of the art, identifying desired elaborations and expansions to this level of development and charting a course that will realize the desired objectives in the future. Efforts are detailed across all work packages in developing those requirements and tools needed to test, refine, and validate basic autonomous rendezvous and docking elements

Initial Investigation of Reaction Control System Design on Spacecraft Handling Qualities for Earth Orbit Docking

A program of research, development, test, and evaluation is planned for the development of Spacecraft Handling Qualities guidelines. In this first experiment, the effects of Reaction Control System design characteristics and rotational control laws were evaluated during simulated proximity operations and docking. Also, the influence of piloting demands resulting from varying closure rates was assessed. The pilot-in-the-loop simulation results showed that significantly different spacecraft handling qualities result from the design of the Reaction Control System. In particular, cross-coupling between translational and rotational motions significantly affected handling qualities as reflected by Cooper-Harper pilot ratings and pilot workload, as reflected by Task-Load Index ratings. This influence is masked but only slightly by the rotational control system mode. While rotational control augmentation using Rate Command Attitude Hold can reduce the workload (principally, physical workload) created by cross-coupling, the handling qualities are not significantly improved. The attitude and rate deadbands of the RCAH introduced significant mental workload and control compensation to evaluate when deadband firings would occur, assess their impact on docking performance, and apply control inputs to mitigate that impact

Faulty Operation of Coils’ and Humidifier Valves in a Typical Air-Handling Unit: Experimental Impact Assessment of Indoor Comfort and Patterns of Operating Parameters under Mediterranean Climatic Conditions

Data-driven Automated Fault Detection and Diagnosis (AFDD) are recognized as one of the most promising options to improve the efficiency of Air-Handling Units (AHUs). In this study, the field operation of a typical single-duct dual-fan constant air volume AHU is investigated through a series of experiments carried out under Mediterranean (southern Italy) climatic conditions considering both fault-free and faulty scenarios. The AHU performances are analyzed while artificially introducing the following five different typical faults: (1) post-heating coil valve stuck at 100% (always open); (2) post-heating coil valve stuck at 0% (always closed); (3) cooling coil valve stuck at 100% (always open); (4) cooling coil valve stuck at 0% (always closed); (5) humidifier valve stuck at 0% (always closed). The measured faulty data are compared against the corresponding fault-free performance measured under the same boundary conditions with the aim of assessing the faults’ impact on both thermal/hygrometric indoor conditions, as well as patterns of 16 different key operating parameters. The results of this study can help building operators and facility engineers in identifying faults’ symptoms in typical AHUs and facilitate the related development of new AFDD tools