Fly-by-wire systems

A personal automobile has a profound effect on a persons mobility and ability to participate in society. A wheelchair is suitable for short distances, and for many situations where an unimpaired person would walk. Modifications to vehicles maybe as simple as a lever attached to the brake and accelerator pedals or as complex as a complete joystick controlled fly-by-wire system. Modifications to other components of the vehicle may be required to provide wheelchair access. An automobile may not be appropriate for some people who travel distances too long to be convenient with a wheelchair, but not long enough to warrant an adapted automobile. Micro-cars, enlarged wheelchairs which travel at bicycle speeds, are convenient for many people who wish only to travel to the local grocery store or post office. Micro-cars are also useful for people who like to travel along bicycle paths or drive short distances off-road. 

Aperiodic real-time events may occur at random, may occur in rapid succession, and may overlap in time in unpredictable ways. A process is in competition with others for processing time and, yet, must complete within some specified time, which may be extremely short (the mechanical movement of an aileron in a fly-by-wire system, for example, must be initiated within microseconds of the process detecting the command from the pilot to do so). Where deadlines are involved, an earliest-deadline-first (EDF) scheduling algorithm may be used. Another algorithm is called least-slack-time first the process with the least available waiting time left is scheduled first. Either of these may also be used to schedule periodic processes. EDF will tend to favor high-frequency processes. 

With the introduction of the Fly-By-Wire system in commercial aviation in the late 1980s, automation surprise has been considered as one of the major contributing factors in aircraft incidents and accidents. In the wake of Air France s Airbus A330 crash in 2009 (where temporary blockage of the pitot tubes by icing started it off and the... 

Depending upon the status of the fly-by-wire system, three sets of control laws are provided Normal Law, Alternate Law and Direct Law. Under most circumstances, the airaaft is operated in Normal Law. Normal Law is designed to accommodate single system failures. Normal Law provides five different protections ... 

Meanwhile, in the area of remote manipulation, electrohydraulic, or electromechanical, bilateral master-slave systems were developed for the nuclear power industry to reduce the mental burden placed on the operator by providing force reflection. Aircraft controls for large planes and some high-performance military aircraft, building on work from the field of teleoperation or remote manipulation, have done away with the direct physical interconnection of the pilot and flight surfaces and now use fly-by-wire systems. 

The HEAT/ACT project consists of replacing the conventional mechanical flight control system on a helicopter with a fly-by-wire system (see Staple Handcock 2002). It involves extensive re-engineering of the aircraft systems, including ... 

The circumstances leading to the above events are quite complicated and need some detailed introduction, and there are a lot of acronyms for the different parts of the control systems. Like all modem Boeing and Airbus civil airliners, the Airbus A330 has a digital electronic flight control system, a fly-by-wire system which monitors and controls flight parameters continuously and enables the pilot and... 

Dependable Avionies Architeetures Example of a Fly-by-Wire system... 

Since the diseontinuation of the A300 and A310 in 2007, all Airbuses have fly-by-wire systems, all with electronically controlled surfaces, hydraulically or... 

YEH 04] Yeh Y.C., Unique dependability issues for commercial airplane fly-by-wire systems , IFIP World Computer Congress, Toulouse, August 2004. 

A traditional approach to fault diagnosis in the wider application context is based on hardware i.e. physical) redundancy methods which use multiple lines of sensors, actuators, computers and software to measure and/or control a particular variable. Typically, a voting scheme is applied to the hardware redundant system to decide if and when a fault has occurred and its likely location amongst redundant system components. The use of multiple redundancy in this way is common, for example with digital fly-by-wire flight control... 

Aircraft The entire control instrumentation and fly by wire flight systems. 

It is our contention that safety assessments should ideally be quantitative. For a fly-by-wire airliner, we need to know that the flight control system has an acceptably low failure rate for an air traffic control system there might be a similar requirement with, in addition, a need for high availability for a reactor protection system, the probability of failure on demand must be sufficiently low. We believe it is inevitable that these quantitative requirements for the safety of such systems be expressed in probabilistic terms, because of the inherent uncertainty about the behaviour of ail real systems during operational use. 

The first electrical flight-control system (Fly-by-Wire FBW) for civilian aircraft was designed by Aerospatiale and installed on Concorde. It was a full authority analog system for all control surfaces, surface position being the sum of the pilot controllers position and of some stabilization orders. A mechanical backup system was available on all three axes. 

Regarding dissimilar redundancy dissimilarity can be both in hardware and software. Software dissimilarity is achieved by producing two separate software lequirements/solutions and by the use of two separate teams. Increased workload is countered by being able to limit the amount of testing hy virtue of the replication of computation. The two software lines run asynchronously in two processes and their outputs are added or compared to ensure that no demand is made incorrectly. This achieves high integrity hut at the expense of avaUahUity, so that where passivity cannot be tolerated (e.g. fly-by-wire control systems) such architectures must have an alternative central lane in the event of a failure. 

Many techniques have been used to measure the velocity of a projectile. The most widely used systems are instantaneous, discrete techniques such as sensors or chronographs. Impact or residual velocity of a projectile is calculated from the distance between two sensors divided by the time taken by the projectile flying between the sensors. Sensors currently employed in the ballistic range include light-emitting diodes, laser beams, thin wires, or infrared beam. Impact and residual velocities obtained from the rig are used to calculate the projectile kinetic energy loss AE ... 

Another very sensitive detection scheme is based on resonant two- or three-photon ionization of atoms and molecules in the gas phase (Sect. 1.3). With this technique even liquid or solid samples can be monitored if they can be vaporized in a furnace or on a hot wire. If, for instance, a heated wire or plate in a vacuum system is covered by the sample, the atoms or molecules are evaporated during the pulsed heating period and fly through the superimposed laser beams Li- -L2(-f-L3) in front... 

Another very sensitive detection scheme is based on resonant two- or three-photon ionization of atoms and molecules in the gas phase (Sect. 6.3). With this technique even liquid or solid samples can be monitored if they can be vaporized in a furnace or on a hot wire. If, for instance, a heated wire or plate in a vacuum system is covered by the sample, the atoms or molecules are evaporated during the pulsed heating period and fly through the superimposed laser beams L1+L2 (+L3) in front of the heated surface (Fig. 15.2). The laser LI is tuned to the resonance transition /> - k) of the wanted atom or molecule while L2 further excites the transition k) f). Ions are formed if Ef is above the ionization potential IP. The ions are accelerated toward an ion multiplier. If L2 has sufficient intensity, all excited particles in the level / ) can be ionized and all atoms in the level [/ flying through the laser beam during the laser pulse can be detected single-atom detection) [15.10-15.12]. If... 

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