Improving Dwell-Based Gaze Typing with Dynamic, Cascading Dwell Times

This work presents an investigation of the minimum dwell time during the precision cylindrical-plunge grinding process. According to the model of acoustic emissions proposed in earlier work, two estimation algorithms of the dwell time, focused on the size error and the surface roundness of the machined workpiece, are deduced from the models of the material removal and the surface roundness, respectively. Based on the proposed estimation algorithms, an on-line estimation method of the minimum dwell time is developed using the measurement and analysis of the acoustic emission signal. A series of experiments of grinding C45 steel are conducted to confirm the validity of the proposed estimation algorithms and determine the model coefficient. The ability of the estimation algorithms to predict the minimum dwell time is deemed necessary for optimal control of the grinding process. In addition, the proposed model provides a new approach to estimate the machined qualities of a workpiece such as the surface roughness and size error using the dwell time of the grinding process.

Explicit conditions on the minimum dwell time that guarantees the asymptotic stability of switched linear systems are given. To this aim, methods that have been proposed for non-defective stable subsystem matrices are generalized to arbitrary stable subsystems matrices. Admissible switchings between subsystems are assumed to be in a general form, namely switchings respect a given directed graph. It is shown that logarithmic norm of matrix exponentials and Lambert-W functions can be used to bound the solutions of switched linear systems in case of defective subsystem matrices. Using a generalized version of Jordan form, dwell time bound can be found for any set of stable subsystem matrices.

In this paper, switched linear systems are considered and dwell and average dwell time for their global asymptotic stability is examined. Dwell and average dwell time are determined based on the condition number for the global asymptotic stability of switched linear differential systems. Numerical examples which show the effect of the results obtained are given with the new dwell and average dwell times.

Cyclic shear zone cataclasis and sintering during lava dome extrusion: Insights from Chaos Crags, Lassen Volcanic Center (USA)

Ensuring constraint satisfaction is distinctly challenging for externally switched systems. Previous work addressing these challenges has focused on cases where the time between switches is longer than some minimum dwell time. While this admits assurances of feasibility, it precludes uncontrollable modes. Further, the presence of poorly behaved modes, where the control actions only narrowly overcome instability, can greatly decrease the size of the switched system's persistently feasible regions. To surmount these issues, this work examines systems with transient modes that will only be active for some maximum dwell time. Corresponding feasible regions, represented by safe-sets are developed that make use of these transient modes. Not only does this permit feasibility assurances in systems with uncontrollable modes, but this also limits the impact poorly behaving modes. These benefits are demonstrated in two numerical examples. Further, the implementation of these results in model predictive control is discussed.

In this paper, the consensus problem of a class of linear multi-agent systems is analysed. In our model, switching between subnetworks and competition between agents is considered simultaneously. We suppose that all subnetworks cannot achieve a consensus and switching signal has a minimum dwell time. By using the time-dependent quadratic Lyapunov function and the average dwell time method, a consensus condition of switched networks is obtained. By using the sum of squares (SOS) programming in the software package SOSTOOLS of Matlab, these resulting conditions can be implemented. The results obtained are also extended to uncertain linear multi-agent systems. Finally, a simulation example is given to illustrate the validity of our results.

Robust stability of switched positive linear systems with interval uncertainties via multiple time-varying linear copositive Lyapunov functions

SummaryThis article is concerned with the quasi‐time‐dependent asynchronous filter design problem for a class of discrete‐time switched systems via the event‐triggering mechanism. Applying the quasi‐time‐dependent Lyapunov functions and the mode‐dependent average dwell time technique, an asynchronous filter is designed with a weighted performance index; the filter parameter matrices are quasi‐time‐dependent in each event‐triggering‐dependent sampling interval; both cases (Case 1: no more than one switching, Case 2: multiple switchings) are taken into account in this sampling interval, by which the assumption, that the maximal asynchronous period is not larger than the minimal dwell time, is relaxed in this article. Simulation examples are given to show the less conservatism and effectiveness of the proposed results.

Compression-induced destabilization was investigated in various celecoxib amorphous solid dispersions containing hydroxypropyl methylcellulose (HPMC), poly(vinylpyrrolidone)/vinyl acetate copolymer (PVP/VA), or poly(vinylpyrrolidone) (PVP) at a concentration range of 1-10% w/w. Pharmaceutically relevant (125 MPa pressure with a minimal dwell time) and extreme (500 MPa pressure with a 60 s dwell time) compression conditions were applied to these systems, and the changes in their physical stability were monitored retrospectively (i.e., in the supercooled state) using dynamic differential scanning calorimetry (DSC) and low-frequency Raman (LFR) measurements over a broad temperature range (-90 to 200 and -150 to 140 °C, respectively). Both techniques revealed similar changes in the crystallization behavior between samples, where the application of a higher compression force of 500 MPa resulted in a more pronounced destabilization effect that was progressively mitigated with increasing polymer content. However, other aspects such as more favorable intermolecular interactions did not appear to have any effect on reducing this undesirable effect. Additionally, for the first time, LFR spectroscopy was used as a viable technique to determine the secondary or local glass-transition temperature, Tg,β, a major indicator of the physical stability of neat amorphous pharmaceutical systems.

Thanks to recent technological advances in the field of eye tracking, eye typing provides means of communication for people with severe disabilities. Typing with gaze using dwell time has been made possible by the development of eye tracking technologies. Recent research indicates that pupil size is viewed as a subtle cue of people is making a decision. Therefore, it may help to infer users’ willing of typing. The present study describes the design process for improving eye typing by adding pupil size index into dwell time triggering. Experimental evaluations showed that the approach was effective; design considerations for such optimization of the gaze typing interfaces are discussed.

Non-weighted H∞ performance for 2-D FMLSS switched system with maximum and minimum dwell time

Tailored Mixed-Integer Optimal Control policies for real-world applications usually have to avoid very short successive changes of the active integer control. Minimum dwell time (MDT) constraints express this requirement and can be included into the combinatorial integral approximation decomposition, which solves mixed-integer optimal control problems (MIOCPs) to epsilon -optimality by solving one continuous nonlinear program and one mixed-integer linear program (MILP). Within this work, we analyze the integrality gap of MIOCPs under MDT constraints by providing tight upper bounds on the MILP subproblem. We suggest different rounding schemes for constructing MDT feasible control solutions, e.g., we propose a modification of Sum Up Rounding. A numerical study supplements the theoretical results and compares objective values of integer feasible and relaxed solutions.

Dwell time is one of the main parameters influencing heat seal quality and process efficiency in flexible packaging. In this study, the rheological behaviour of polypropylene (PP)/low‐density polyethylene (PE‐LD)‐based compound films containing different ratios of talc was examined. The minimum dwell time required to supply a sufficient sealing was estimated based on heat conduction time and reptation time. Reptation is a rheological concept used to described the behaviour of a polymer melt, and the reptation time is the time required for a molecule to escape from its surrounded entangled structure. The results showed that increased levels of talc are associated with elevated complex viscosities, storage and loss modulus as well as an increased seal strength. The estimated minimum required dwell time at the seal initiation temperature (SIT) dropped sharply with the initial introduction of 10 wt% talc. However, increasing the talc ratio to 30 wt% did not create any major change in the estimated time value. Also, observed T‐peel strength values for 0.1 and 0.5 s dwell time at SIT confirmed the predicted minimum required dwell time values. On the other hand, when the seal temperature is increased to the higher end of the operation window, time estimations did not match with the observed seal strengths. Here, the melting already starts and the molecules diffuse up to a certain distance before the interface temperature reaches the desired level. Recalculation of the average diffusion distance by including this pre‐melting situation can present a better approach for the temperatures above SIT. When the molecules diffused around halfway along the sealant thickness observed, seal strengths reached a sufficient level (2.5 N/25 mm) for both SIT and the highest end of the operation window. In conclusion, it has been revealed that knowing the reptation time and the required time for the heat conduction during the sealing process can help to predict the minimum required dwell time to achieve quality sealing, especially at low sealing temperatures. Additional surface characterizations also helped to elaborate on the influence of changing insoluble filler ratio on the seal initiation properties. It has been showed that the added talc increases the surface free energy and supplies easier wetting at the seal interface. Therefore, adding talc or a similar insoluble filler can help to make the heat sealing process more efficient.

Stability analysis of switched cellular neural networks: A mode-dependent average dwell time approach

Gaze interaction is a promising input modality for people who are unable to control their fingers and arms. This paper suggests a number of new metrics that can be applied to the analysis of gaze typing interfaces and to the evaluation of user performance. These metrics are derived from a close examination of eight subjects typing text by gazing on a dwell-time activated onscreen keyboard during a seven-day experiment. One of the metrics, termed “Attended keys per character”, measures the number of keys that are attended for each typed character. This metric turned out to be particularly well correlated to the actual numbers of errors committed (r = 0.915). In addition to introducing metrics specific for gaze typing, the paper discusses how the metrics could make remote progress monitoring possible and provides some general advice on how to introduce gaze typing for novice users.