Continuous-time envelope constrained filter design via orthonormalfilters

The envelope constrained (EC) filtering problem is concerned with designing a filter which minimises the gain to input noise while its response to a given signal fits into a prescribed envelope. This problem had been formulated as a constrained optimisation problem in Hilbert space. By restricting these filters to the span of a finite orthonormal set, the EC filtering problem can be posed as a finite dimensional optimisation problem with a continuum of constraints. The constrained problem is approximated by an unconstrained problem which is then solved by descent direction based algorithms. It is shown that these algorithms converge globally, and one in particular has a quadratic rate of convergence. Numerical examples using the orthonormal Laguerre series approximation are studied     

Generalized interface handler and multi-tasking operation in MS/DOS for PC-based SCADA system

This paper describes a generalized interface handler implemented on a PC-based SCADA system which can handle up to a total of 512 digital points and 512 analog points. It is aimed to provide a standard structure for SCADA application program to be independent from the interfacing hardware. Using the same data structure, a multi-tasking operation has also been implemented under the single-tasking operating system MS/DOS. The prototype SCADA system employing four different types of hardware interface is demonstrated.     

Neighbouring extremals for nonlinear systems with control constraints

In this paper, we consider a class of nonlinear optimal control problems subject to control constraints. We assume that an initial condition for the dynamical system is specified. Then, we can easily compute an openloop optimal control using any convenient optimal control software package. Now, suppose the optimal trajectory is perturbed due to a change in initial conditions or uncertainty in the model equations. If the perturbations are not too large, it is known that the neighbouring extremal approach can be used to obtain a feedback law which adjusts the open-loop optimal control accordingly provided there are no bounds on the control variables. In this paper, our aim is to develop a computational method for the more general case of fixed-time problems with control constraints.     

On initial instantaneous jumps of singular systems

This paper is concerned with instantaneous jumps in the state trajectory of a singular system. It is shown that such jumps generically exist at the initial time due to inconsistent initial states. The formula for the jumps is derived, which indicates that the jumps linearly depend on the initial state. Moreover, the set of all initial states which do not cause any state jumps for any output feedback is characterized and is revealed to be a linear subspace. In the meantime, the necessary and sufficient conditions are given for the existence of an output feedback to suppress completely the jumps for a given initial state. Finally, we formulate the problem of designing an output feedback not only to stabilize the plant but also to achieve minimum initial jumps as a minimization problem     

A study of shock characterization for protective packaging design

Cushioning buffers made of expandable polystyrene, a white polymeric granulated material, are commonly used to protect goods from damage. Current design practices tend to be simplistic and general, resulting in either overdesigned buffers or inadequate product protection. The objective of this paper is to identify the main parameters affecting shock absorption so that products can be better protected. An investigative study reveals that the types of impact surfaces, material densities, geometric features, and configurations contribute significantly to the amount of shock that a product experiences.     

Application of knowledge-based systems for fault diagnosis and supply restoration

A knowledge-based system (KBS) for fault diagnosis and supply restoration in an electrical power distribution system is introduced to complement the teaching of the related theory in a senior-year course. The KBS communicates with a power-system simulator which enables the setup of various scenarios. Through the KBS, the students strengthen their understanding of generic diagnostic rules, restoration algorithms, knowledge acquisition and inference mechanisms. Six training scenarios are described to illustrate how the concepts of fault diagnosis, supply restoration and various features of the KBS can be taught.     

Prediction of the modal characteristics of the human spine at resonant frequency using finite element models

To understand the dynamic characteristics of the human spine, a detailed three-dimensional finite element model of the lower thorax to pelvis segment, T12-pelvis, was developed based on actual vertebral geometry. After modal analysis, the resonant frequencies of different spinal segments were obtained. The vibration mode of T12-pelvis shows that the human upper body mainly performs the vertical motion during whole-body vibration and the lumbar spine segment conducts translation and rotation in the sagittal plane. The lower segments of the lumbar spine move in flexion and the upper lumbar segments move in extension. This investigation may be helpful in understanding further the biomechanical behaviour of the human spine under the condition of whole-body vibration and to offer potential references for spinal disease treatments and product design in industry.     

A comparison of scanning methods and the vertical control implications for scanning probe microscopy

This article compares the imaging performance of non‐traditional scanning patterns for scanning probe microscopy including sinusoidal raster, spiral, and Lissajous patterns. The metrics under consideration include the probe velocity, scanning frequency, and required sampling rate. The probe velocity is investigated in detail as this quantity is proportional to the required bandwidth of the vertical feedback loop and has a major impact on image quality. By considering a sample with an impulsive Fourier transform, the effect of scanning trajectories on imaging quality can be observed and quantified. The non‐linear trajectories are found to spread the topography signal bandwidth which has important implications for both low and high‐speed imaging. These effects are studied analytically and demonstrated experimentally with a periodic calibration grating.     

Improving Robustness Filter Bandwidth in Repetitive Control by Considering Model Mismatch

Repetitive control (RC) is used to track and reject periodic signals by including a model of a periodic signal in the feedback path. The performance of RC can be improved by including an inverse plant response filter, but due to modeling uncertainty at high frequencies, a low‐pass robustness filter is also required to limit the bandwidth of the signal model and ensure stability. The design of robustness filters is presently ad‐hoc, which may result in excessively conservative performance. This article proposes a new automatic method for designing the robustness filter based on convex optimization and an uncertainty model. Experimental results on a nanopositioning system demonstrate that the proposed method outperforms the traditional brick‐wall filter approach.     

Psychological paradox of game software trial

Game software trial versions, as the scaled-down versions of the software through imposing restrictions on functionality and/or usage of a grace period, are often given to users for free evaluation. Such a move is intended to encourage the eventual purchase of the full version software. Offering a trial version could psychologically influence an individual (i.e., arousing emotions as joy from playing the game), thereby heightening his or her willingness to pay (WTP) for the full version software, for which the individual’s fundamental nature of self-control might avert him or her from doing so — the psychological paradox. Considering that a game software trial version is usually restricted through the permitted grace period (time restriction) or the extent of functionality available for use (functionality restriction), this research examines the psychological effects of these two forms of trial restrictions on users by anchoring on the opponent-process theory. Results from an online study involving 128 users reveal that imposing functionality restriction could lead to strong negative consequences on users’ cognitive absorption but heighten users’ self-control outcomes. Interestingly, imposing time restriction does not have an observable effect on these two variables. These findings provide insightful theoretical and practical implications.