Note on ‘Construction of Double Sampling s‐Control Charts for Agile Manufacturing’

He and Grigoryan (Quality and Reliability Engineering International 2002; 18 :343–355) formulated the design of a double‐sampling (DS) s control chart as an optimization problem and solved it with a genetic algorithm. They concluded that the DS s control charts can be a more economically preferable alternative in detecting small shifts than traditional s control charts. We explain that, since they only considered the average sample size when the process is in control, their conclusion is questionable. Copyright © 2006 John Wiley & Sons, Ltd.     

Robustness of VS-MRAC with respect to unmodelled dynamics and external disturbances

A variable structure model reference adaptive controller (VS-MRAC) using only input and output measurements was recently proposed and shown to be globally asymptotically stable with superior transient behaviour and disturbance rejection properties. In this paper a singular perturbation approach is used in order to establish the robustness of the controller in the presence of unmodelled dynamics (parasitics) and disturbances. We develop a new Lyapunov-based technique to analyse the overall system and show that for sufficiently small parasitics the system remains stable and the output error is small in some sense.     

The material properties of sulphonated phenolic resin reinforced cement mortars

The material properties of new sulphonated phenolic resin (SP) reinforced cement mortars have been investigated. SP was found to promote the dispersion of cement particles and to interact with Ca(OH)₂. As a result, the resulting mortars exhibit better workability, more compact structure and higher compressive strength than plain mortars. The mortar with 1 wt% SP present after 28 days curing exhibits a compressive strength of 66MPa, which is about 18% higher than that of plain mortar.     

Onset of gas self-induction and power consumption after gas induction in an agitated tank

The behavior of inducted gas from liquid surface and the; power requirements in an agitated tank using a mechanical agitator are studied in order to increase the amount of gas self-induction and the gas retention time for gas absorption. A 45° six-blade downward impeller turbine was utilized in this study. Air and water, air and 40 wt% 60 wt%, and 80 wt% of glycerin water, and air and 106 cP silicon oil were employed as gas and liquid phases. Variables which were studied included geometrical factors (immersed depth of impeller, baffle with and diameter of impeller) and the physical properties of the liquid (viscosity, density, and surface tension). The correlations for the onset speed of impeller and power consumption after gas induction in the agitated tank are established from our experimental results. The amount of gas self-induction from the liquid surface in the agitated tank increases with increasing impeller diameter and speed and decreases with increasing baffle width, depth of impeller and viscosity of liquid.     

A theoretical study of pulsed laser sampling photon amplifiers

Theoretical studies point to significant improvements in the performance of semiconductor laser amplifiers by injecting carriers with pulsed electric currents of sub-nanosecond duration. A pulsed Fabry-Perot amplifier (FPA) is most sensitive to input lightwave at the instant the carrier density is crossing the critical region, and gives a sharply pulsed sampling effect on the input lightwave signal. Compared with a FPA operating at subcritical electron density, the pulsed amplifier gives much higher gain, peak power, and bandwidth. In fact, pulsed operation of a FPA is also expected to give significantly higher gain and about the same peak output power as a traveling wave amplifier. Pulsed operation also improves the performance of a traveling wave amplifier by attenuating its internally reflected waves     

An experimentally verified hybrid Cassie-Mayr electric arc modelfor power electronics simulations

This paper presents an electric arc model that can approximately represent both the static and dynamic characteristics of an arc load controlled by a power electronic circuit. The proposed model was developed from the combination and modifications of the classical Cassie and Mayr equations. The model equations have been expressed in a form suitable for incorporation into circuit simulators employing the nodal analysis method of equation solving. The model has been test-implemented in the Saber circuit simulator. Simulated and experimental results appear to be in good agreement     

Least mean p-power error criterion for adaptive FIR filter

An adaptive FIR filter based on the least mean p-power error (MPE) criterion is investigated. First, some useful properties of MPE function are studied. Three main results are as follows: 1) MPE function is a convex function of filter coefficients; so it has no local minima. 2) When input process and desired process are both Gaussian processes, then MPE function has the same optimum solution as the conventional Wiener solution for any p. 3) When input process and desired process are non-Gaussian processes, then MPE function may have better optimum solution than Wiener solution. Next, a least mean p-power (LMP) error adaptive algorithm is derived and some application examples are presented. Consequently, when the signal is corrupted by an impulsive noise, the adaptive algorithm with p=1 is preferred. Furthermore, when the signal is corrupted by noise or interference, the adaptive algorithm with proper choice of p may be preferred     

An observer-based robust adaptive controller for permanent magnet synchronous motor drive with initial rotor angle uncertainty

An observer-based robust adaptive nonlinear position and speed tracking controller is developed for a permanent magnet synchronous motor with initial rotor angle uncertainty. The unknown initial rotor position is treated as a constant motor parameter in the development of the controller. An incremental encoder, which provides relative position variation of the rotor, is used along with stator current signals to achieve stable control. However, the controller does not require the knowledge of motor parameters and it only assumes friction, external disturbances, and model uncertainties are bounded. By using state observers, the measurement of acceleration and load torque, which is required usually in the nonlinear controller design with high tracking performance, is avoided. The stability of the control system and tracking convergence are guaranteed using Lyapunov theory. Finally, the stability and efficacy of the proposed drive system are verified by experimental results.