An ABS control logic based on wheel force measurement

The paper presents an anti-lock braking system (ABS) control logic based on the measurement of the longitudinal forces at the hub bearings. The availability of force information allows to design a logic that does not rely on the estimation of the tyre-road friction coefficient, since it continuously tries to exploit the maximum longitudinal tyre force. The logic is designed by means of computer simulation and then tested on a specific hardware in the loop test bench: the experimental results confirm that measured wheel force can lead to a significant improvement of the ABS performances in terms of stopping distance also in the presence of road with variable friction coefficien

Autonomous rendezvous and capture system design

Marshall Space Flight Center has a long history of involvement in the design of Autonomous Rendezvous and Capture (AR&C) systems. The first extensive studies were begun in the late seventies, incrementally leading to the development of an assortment of Guidance, Navigation, and Control (GN&C) concepts and algorithms suitable for a variety of mission requirements and spacecraft capabilities, with a strong emphasis placed upon flexible system-level design. These efforts have led to the development of sophisticated algorithms for docking with tumbling targets, and simple but efficient algorithms for stabilized spacecraft; each has been tested and validated using dynamic system simulation, with hardware in the loop when practical. Recent investigations include the use of neural networks for video image interpretation, and fuzzy logic for control system implementation

A.I.-based real-time support for high performance aircraft operations

Artificial intelligence (AI) based software and hardware concepts are applied to the handling system malfunctions during flight tests. A representation of malfunction procedure logic using Boolean normal forms are presented. The representation facilitates the automation of malfunction procedures and provides easy testing for the embedded rules. It also forms a potential basis for a parallel implementation in logic hardware. The extraction of logic control rules, from dynamic simulation and their adaptive revision after partial failure are examined. It uses a simplified 2-dimensional aircraft model with a controller that adaptively extracts control rules for directional thrust that satisfies a navigational goal without exceeding pre-established position and velocity limits. Failure recovery (rule adjusting) is examined after partial actuator failure. While this experiment was performed with primitive aircraft and mission models, it illustrates an important paradigm and provided complexity extrapolations for the proposed extraction of expertise from simulation, as discussed. The use of relaxation and inexact reasoning in expert systems was also investigated

Development of a Hardware-in-the-loop Simulation Platform for Safety Critical Control System Evaluation

During the lifetime of a nuclear power plant (NPP) safety electronic control system components become obsolete [7]. It is difficult to find replacement components qualified for nuclear applications [50]. Due to strict regulations, replacement components undergo extensive verification and operational analysis [70]. Therefore, the need for a platform to evaluate replacement safety control systems in a non-intrusive manner is evident. Verifying the operation or functionality of potential replacement electronic control systems is often performed through simulation [71]. To enable simulation, a physical interface between potential control systems and computer based simulators is developed. System connectivity is establish using Ethernet and standard industrial electrical signals. The interface includes a National Instruments (NI) virtual instrument (VI) and data acquisition system (DAQ) hardware. The interface supports simulator controlled transmission and receipt of variables. The transmission of simulated process variables to and from an external control system is enabled. This is known as hardware-in-the-loop (HIL) simulation [49]. Next, HIL interface performance is verified and the following are identified; a measure of availability; the effect of varied configurations; and limitations. Further, an HIL simulation platform is created by connecting a NPP simulator and a programmable logic controller (PLC) to the interface, Canadian Deuterium Uranium (CANDU) reactor training simulator and Invensys Tricon version nine (v9) safety PLC respectively. The PLC is programmed to operate as shutdown system no. 1 (SDSl) of a CANDU reactor. Platform availability is verified and the response of the PLC as SDSl and is monitored during reactor shutdown. Proper execution of the steam generator level low (SGLL) logic on the PLC and variable transmission are observed. Thus, a platform and procedure for the evaluation of replacements for obsolete electronic control system components is demonstrated

Modeling the acquisition front-end in high resolution gamma-ray imaging

Proceeding of: 2004 IEEE Nuclear Science Symposium Conference Record, Rome, Italy, 16-22 October 2004The availability of synthetic realistic data enables design optimization, algorithm evaluation and verification of any digital system where a significant amount of digital signal processing is performed. The evolution of positron emission tomography cameras towards continuous sampling of individual position-sensitive photomultiplier anodes with processing algorithms implemented on digital programmable logic devices creates a new framework where new approaches to the γ-event detection are possible. We have developed a system model of the acquisition chain, including multi-layer phoswich, photomultiplier, front-end analog electronics, data acquisition and data processing. This processing includes estimation algorithms for the most relevant event parameters: energy, layerof- interaction, time picking-off and event location. The selected simulation platform couples gently to digital hardware simulation tools, in such a way that implemented models may generate reallike stimuli for the digital system under development. The modeling of the whole front-end electronics enables deeper understanding and tuning of different system trade-offs and provides a rapid and soft transition between specification and hardware development