Design methodology for the servo control of high speed multi-axis machinery (BL): decoupling and synchronisation of a generic machine by blockwise decentralised MIMO control

Traditional machinery for manufacturing processes are characterised by actuators powered and co-ordinated by mechanical linkages driven from a central drive. Increasingly, these linkages are replaced by independent electrical drives, each performs a different task and follows a different motion profile, co-ordinated by computers. A design methodology for the servo control of high speed multi-axis machinery is proposed, based on the concept of a highly adaptable generic machine model. In addition to the dynamics of the drives and the loads, the model includes the inherent interactions between the motion axes and thus provides a Multi-Input Multi-Output (MIMO) description. In general, inherent interactions such as structural couplings between groups of motion axes are undesirable and needed to be compensated. On the other hand, imposed interactions such as the synchronisation of different groups of axes are often required. It is recognised that a suitable MIMO controller can simultaneously achieve these objectives and reconciles their potential conflicts. Both analytical and numerical methods for the design of MIMO controllers are investigated. At present, it is not possible to implement high order MIMO controllers for practical reasons. Based on simulations of the generic machine model under full MIMO control, however, it is possible to determine a suitable topology for a blockwise decentralised control scheme. The Block Relative Gain array (BRG) is used to compare the relative strength of closed loop interactions between sub-systems. A number of approaches to the design of the smaller decentralised MIMO controllers for these sub-systems has been investigated. For the purpose of illustration, a benchmark problem based on a 3 axes test rig has been carried through the design cycle to demonstrate the working of the design methodology.

Mitigation of patterning effects at 40 Gbits/s by skewed channel pre-encoding

Through direct modeling, a reduction of pattern-dependent errors in a standard fiber-based transmission link at 40 Gbits/s rate is demonstrated by application of a skewed data pre-encoding. The trade-off between the improvement of the bit error rate and the loss in the data rate is examined.

Mitigation of patterning effects at 40 Gb/s by skewed channel pre-encoding

Through modelling of direct error computation, a reduction of pattern- dependent errors in a standard fiber-based transmission link at 40 Gb/s rate is demonstrated by application of a skewed data pre-encoding. The trade-off between the bit-error rate improvement and the data rate loss is examined.

Recent advances in antidiabetic drug therapies targeting the enteroinsular axis

The enteroinsular axis (EIA) constitutes a physiological signalling system whereby intestinal endocrine cells secrete incretin hormones following feeding that potentiate insulin secretion and contribute to the regulation of blood glucose homeostasis. The two key hormones responsible are named glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). Recent years have witnessed sustained development of antidiabetic therapies that exploit the EIA. Current clinical compounds divide neatly into two classes. One concerns analogues or mimetics of GLP-1, such as exenatide (Byetta) or liraglutide (NN2211). The other group comprises the gliptins (e.g. sitagliptin and vildagliptin) which boost endogenous incretin activity by inhibiting the enzyme dipeptidyl peptidase 4 (DPP 4) that degrades both GLP-1 and GIP. Ongoing research indicates that further incretin and gliptin compounds will become available for clinical use in the near future, offering comparable or improved efficacy. For incretin analogues there is the prospect of prolonged duration of action and alternative routes of administration. This review focuses on recent advances in pre-clinical research and their translation into clinical studies to provide future therapies for type 2 diabetes targeting the EIA. © 2009 Bentham Science Publishers Ltd.

Two-axis accelerometer based on multicore fibre Bragg gratings

We report an accelerometer based upon a simple fibre cantilever constructed from a short length of multicore fibre(MCF) containing fibre Bragg gratings (FBGs). Two-axis measurement is demonstrated up to 3 kHz.

Mitigation of patterning effects at 40 Gbits/s by skewed channel pre-encoding

Through direct modeling, a reduction of pattern-dependent errors in a standard fiber-based transmission link at 40 Gbits/s rate is demonstrated by application of a skewed data pre-encoding. The trade-off between the improvement of the bit error rate and the loss in the data rate is examined. © 2007 Optical Society of America.

Mitigation of patterning effects at 40 Gb/s by skewed channel pre-encoding

Through modelling of direct error computation, a reduction of pattern- dependent errors in a standard fiber-based transmission link at 40 Gb/s rate is demonstrated by application of a skewed data pre-encoding. The trade-off between the bit-error rate improvement and the data rate loss is examined.

Patterning effects in a WDM RZ-DBPSK SMF/DCF optical transmission at 40 Gbit/s channel rate

Through extensive direct modelling we quantify the error statistics and patterning effects in a WDM RZ-DBPSK SMF/DCF fibre link using hybrid Raman/ EDFA amplification at 40 Gbit/s channel rate. We examine the BER improvement through skewed channel pre-coding reducing the frequency of appearance of the triplets 101 and 010 in a long data stream. © 2007 Elsevier B.V. All rights reserved.

Patterning effects in WDM RZ-DBPSK SMF/DCF optical transmission at 40 Gbit/s channel rate

Summary form only given. In this paper an important new example of a system with strong and nontrivial patterning effects is presented. There has been much interest lately in the implementation of the differential phase shift-keying (PSK) modulation format for long-haul and ultra long-haul fibre communications and, in particular, the differential binary PSK (DBPSK) modulation format, where data is encoded into the optical phase. The results of a direct computation of the error statistics for an SMF/DCF RZ-DBPSK 5-channel WDM RZ-DBPSK link with hybrid Raman/EDFA amplification at 40 Gbit/s per channel, with a channel separation of 100 GHz are presented. The statistics of bit triplets and quantify strong pattern-dependent ISI are obtained.

Dynamic two-axis curvature measurement using multicore fiber Bragg gratings interrogated by arrayed waveguide gratings

We describe the use of arrayed waveguide gratings (AWGs) in the interrogation of fiber Bragg gratings (FBGs) for dynamic strain measurement. The ratiometric AWG output was calibrated in a static deflection experiment over a ±200 με range. Dynamic strain measurement was demonstrated with a FBG in a conventional single-mode fiber mounted on the surface of a vibrating cantilever and on a piezoelectric actuator, giving a resolution of 0.5 με at 2.4 kHz. We present results of this technique extended to measure the dynamic differential strain between two FBG pairs within a multicore fiber. An arbitrary cantilever oscillation of the multicore fiber was determined from curvature measurements in two orthogonal axes at 1125 Hz with a resolution of 0.05 m-1. © 2006 Optical Society of America.

Analysis of femtosecond laser surface patterning on bulk single-crystalline diamond

Preliminary work is reported on 2-D and 3-D microstructures written directly with a Yb:YAG 1026 nm femtosecond (fs) laser on bulk chemical vapour deposition (CVD) single-crystalline diamond. Smooth graphitic lines and other structures were written on the surface of a CVD diamond sample with a thickness of 0.7mm under low laser fluences. This capability opens up the opportunity for making electronic devices and micro-electromechanical structures on diamond substrates. The fabrication process was optimised through testing a range of laser energies at a 100 kHz repetition rate with sub-500fs pulses. These graphitic lines and structures have been characterised using optical microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy. Using these analysis techniques, the formation of sp2 and sp3 bonds is explored and the ratio between sp2 and sp3 bonds after fs laser patterning is quantified. We present the early findings from this study and characterise the relationship between the graphitic line formation and the different fs laser exposure conditions. © 2012 Taylor & Francis.

Two-axis bend measurement with Bragg gratings in multicore optica fibre

We describe what is to our knowledge the first use of fiber Bragg gratings written into three separate cores of a multicore fiber for two-axis curvature measurement. The gratings act as independent, but isothermal, fiber strain gauges for which local curvature determines the difference in strain between cores, permitting temperature-independent bend measurement.

Numerical estimate of BER in optical systems with strong patterning effects

A statistical approach to evaluate numerically transmission distances in optical communication systems was described. The proposed systems were subjected to strong patterning effects and strong intersymbol interference. The dependence of transmission distance on the total number of bits was described. Normal and Gaussian distributions were used to derive the error probability.