28 research outputs found
Disseny microelectrnic de circuits discriminadors de polsos pel detector LHCb
The aim of this thesis is to present a solution for implementing the front end system of the Scintillator Pad Detector (SPD) of the calorimeter system of the LHCb experiment that will start in 2008 at the Large Hadron Collider (LHC) at CERN. The requirements of this specific system are discussed and an integrated solution is presented, both at system and circuit level. We also report some methodological achievements. In first place, a method to study the PSRR (and any transfer function) in fully differential circuits taking into account the effect of parameter mismatch is proposed. Concerning noise analysis, a method to study time variant circuits in the frequency domain is presented and justified. This would open the possibility to study the effect of 1/f noise in time variants circuits. In addition, it will be shown that the architecture developed for this system is a general solution for front ends in high luminosity experiments that must be operated with no dead time and must be robust against ballistic deficit
Fault tolerant drives for safety critical applications
PhD ThesisThe correct operation of adjustable speed drives, which form part of a larger system, is
often essential to the operation of the system as a whole. In certain applications the
failure of such a drive could result in a threat to human safety and these applications are
termed 'safety critical'. The chance of a component failure resulting in non-operation of
the drive can be dramatically reduced by adopting a fault tolerant design. A fault tolerant
drive must continue to operate throughout the occurrence of any single point failure
without undue disturbance to the power output. Thereafter the drive must be capable of
producing rated output indefinitely in the presence of the fault.
The work presented in this thesis shows that fault tolerance can be achieved without
severe penalties in terms of cost or power to mass ratio. The design of a novel permanent
magnet drive is presented and a 'proof of concept' demonstrator has been built, based on
a 20 kW, 13000 RPM aircraft fuel pump specffication. A novel current controller with
near optimal transient performance is developed to enable precise shaping of the phase
currents at high shaft speeds. The best operating regime for the machine is investigated
to optimise the power to mass ratio of the drive.
A list of the most likely electrical faults is considered. Some faults result in large fault
currents and require rapid detection to prevent fault propagation. Several novel fault
sensors are discussed. Fault detection and identification schemes are developed,
including new schemes for rapid detection of turn to turn faults and power device short
circuit faults. Post fault control schemes are described which enable the drive to continue
to operate indefinitely in the presence of each fault. Finally, results show the initially
healthy drive operating up to, through and beyond the introduction of each of the most
serious faults.EPSR