Analytical and experimental approach to damage and residual strength of fibreglass composite automotive frame rails during manufacturing

The use of composite materials in the construction of various structural components of the car body has gained an increasing interest in the automotive industry. In relation to this, the crashworthy ability of an automotive frame rail of hour glass cross-section, made of a glass fiber/ vinylester composite and designed for use in the apron construction of the car, when subjected to axial collapse and bending, has been extensively investigated in this paper.

An important problem arose, dealing with the delamination observed at the corners and curved parts of the hourglass section which may be attributed to the manufacturing processing, resulting in severe limitations in the load-carrying capacity of this structural component. The effect of the residual stress and strain fields induced during fabrication was examined both theoretically and experimentally and possible failure mechanisms observed were investigated and discussed.     

Design of an adaptive interference reduction system for nerve-cuff electrode recording

This paper describes the design of an adaptive control system for recording neural signals from tripolar cuff electrodes. The control system is based on an adaptive version of the true-tripole amplifier configuration and was developed to compensate for possible errors in the cuff electrode balance by continuously adjusting the gains of the two differential amplifiers. Thus, in the presence of cuff imbalance, the output signal-to-interference ratio is expected to be significantly increased, in turn reducing the requirement for post-filtering to reasonable levels and resulting in a system which is fully implantable. A realization in 0.8-/spl mu/m CMOS technology is described and simulated and preliminary measured results are presented. Gain control is achieved by means of current-mode feedback and many of the system blocks operate in the current-mode domain. The chip has a core area of 0.4 mm/sup 2/ and dissipates 3 mW from /spl plusmn/ 2.5V power supplies. Measurements indicate that the adaptive control system is expected to be capable of compensating for up to /spl plusmn/5% errors in the tripolar cuff electrode balance.     

2.8 V asynchronous high-speed current comparator for sequencedetection applications

A low voltage, low power current-mode comparator is described. The circuit features a wide dynamic range and very high-speed asynchronous operation and is intended for use in maximum likelihood sequence detection (MLSD) applications     

High-Power Integrated Stimulator Output Stages With Floating Discharge Over a Wide Voltage Range for Nerve Stimulation

Two integrated nerve stimulator circuits are described. Both generate passively charge-balanced biphasic stimulating pulses of 1 to 16 mA with 10-$mu $s to 1-ms widths from 6- to 24-V supplies for implanted book electrodes. In both circuits, the electrodes are floating during the passive discharge anywhere within the range of the power rails, which may be up to 24 V. The first circuit is used for stimulation only. It uses a floating depletion transistor to enable continuous discharge of the electrodes, except when stimulating, without using power. The second circuit also allows neural signals to be recorded from the same tripole. It uses a modified floating complementary metal–oxide semiconductor (CMOS) discharge switch capable of operating over a range beyond the gate-to-source voltage limits of its transistors. It remains off for long periods using no power while recording. A 0.6-$mu $m silicon-on-insulator CMOS technology has been used. The measured performance of the circuits has been verified using multiple tripoles in saline.      

Vestibular prosthesis design for restoring balance

Over the last decade significant progress has been made in developing neuroprosthetic devices to restore balance. However, there still remain major challenges to overcome before an advanced clinical implant is created. These include efficient wireless power and data transmission, multichannel stimulation with minimal crosstalk, effective and safe stimulation, an accurate modulation scheme, dynamic and adaptive feedback, device miniaturization, electrode fabrication and packaging. This paper provides a review of the development in vestibular prostheses to date, and uses a specific example to demonstrate the problems in designing the implantable circuits for such a neuroprosthetic device.     

On cuff imbalance and tripolar ENG amplifier configurations

Electroneurogram (ENG) recording techniques benefit from the use of tripolar cuffs because they assist in reducing interference from sources outside the cuff. However, in practice the performance of ENG amplifier configurations, such as the quasi-tripole and the true-tripole, has been widely reported to be degraded due to the departure of the tripolar cuff from ideal behavior. This paper establishes the presence of cuff imbalance and investigates its relationship to cuff asymmetry, cuff end-effects and interference source proximity. The paper also presents a comparison of the aforementioned amplifier configurations with a new alternative, termed the adaptive-tripole, developed to automatically compensate for cuff imbalance. The output signal-to-interference ratio of the three amplifier configurations were compared in vivo for two interference signals (stimulus artifact and M-wave) superimposed on compound action potentials. The experiments showed (for the first time) that the two interference signals result in different cuff imbalance values. Nevertheless, even with two distinct cuff imbalances present, the adaptive-tripole performed better than the other two systems in 61.9% of the trials.     

Reduction of effects of signal-dependent errors in current-modeanalogue Viterbi decoders

Current-mode analogue techniques can be employed to realise high-speed, low-power Viterbi decoders. However, signal dependent errors due to charge injection tend to limit the application of these methods to small decoders. A technique is presented for reducing the effects of charge injection on the system performance     

Energy absorption capability of fibreglass composite square frusta subjected to static and dynamic axial collapse

The crashworthy behaviour of square frusta of fibreglass composite material subjected to axial compression at various strain rates is reported. The effect of specimen geometry and the loading rate on the energy absorbing capability was experimentally studied. The mechanics of the axial crumbling process from macroscopic and microscopic points of view were also investigated theoretically and experimentally. The collapse modes at macroscopic and microscopic scale during the failure process were observed and analysed. A theoretical analysis of the observed stable collapse mechanism of the components crushed under axial compression, for calculating crushing loads and energy absorbed during collapse, is proposed. A good agreement between theoretical and experimental results was obtained indicating the efficiency of the theoretical model in predicting the energy absorbing capacity of the collapsed shell.     

“Sweet Spots” in Moderate Inversion for MOSFET Squarer Transconductors

Two "sweet spots" are analytically identified to enable MOSFET squarer differential transconductors to efficiently operate in moderate inversion. Measurements at low frequencies demonstrate the practicality of using moderate inversion when input signals are limited to about 200 mV_pk-pk. At the first sweet spot, very low distortion of significantly less than 0.5% total harmonic distortion is possible. For comparison, the sweet spot for the third harmonic is shown for the linear differential transconductor. This brief also discusses the effect of the variations in threshold voltage on the location of the sweet spots, and demonstrates that this sensitivity can be greatly reduced using an appropriate biasing circuit. The proposed approach is of particular interest for low voltage and low current squarer transconductance applications.     

Compact low-voltage CMOS four-quadrant analogue multiplier

A compact architecture for a four-quadrant analogue multiplier circuit is presented. The circuit is formed by connecting common source amplifiers with a pair of differential flipped voltage followers. This results in a novel cancellation of the nonlinear terms in the sub-currents, leading to the desired four-quadrant analogue multiplier. The circuit combines low complexity with low-voltage operation and low static power consumption. Simulated results using a 0.35 mum CMOS process are provided