A Case for Feedforward Control with Feedback Trim to Mitigate Time Transfer Attacks

Abstract Zero phase error tracking (ZPET) control has gained popularity as a simple yet effective feedforward control method for tracking time varying desired trajectories by the plant output. In this paper, we will show that the zero-order hold equivalent of continuous time transfer function, i.e. pulse transfer function, naturally has a property to realize zero phase effort tracking. This property is exploited to realize a simple implementation of zero phase error tracking control. The effectiveness of the proposed approach is demonstrated by simulations.

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Dysarthria Profiles in Adults With Hereditary Ataxia

American Journal of Speech-Language Pathology ◽

10.1044/2018_ajslp-msc18-18-0114 ◽

2019 ◽

Vol 28 (2S) ◽

pp. 915-924 ◽

Cited By ~ 2

Author(s):

Kristie A. Spencer ◽

Mallory Dawson

Keyword(s):

Rating Scales ◽

Feedforward Control ◽

Hereditary Ataxia ◽

Severity Rating ◽

Visual Analog Scales ◽

Speech Characteristics ◽

Ataxic Dysarthria ◽

Preliminary Study

Purpose This preliminary study examined whether speech profiles exist for adults with hereditary ataxia based on 2 competing frameworks: a pattern of instability/inflexibility or a pattern of differential subsystem involvement. Method Four dysarthria experts rated the speech samples of 8 adults with dysarthria from hereditary ataxia using visual analog scales and presence/severity rating scales of speech characteristics. Speaking tasks included diadochokinetics, sustained phonation, and a monologue. Results Speech profiles aligned with the instability/inflexibility framework, with the pattern of instability being the most common. Speech profiles did not emerge for the majority of speakers using the differential subsystem framework. Conclusions The findings extend previous research on pure ataxic dysarthria and suggest a possible framework for understanding the speech heterogeneity associated with the ataxias. The predominance of the instability profile is consistent with the notion of impaired feedforward control in speakers with cerebellar disruption.

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Use of vent stack temperature as a feedforward variable for dissolver total titratable alkali (TTA) control

TAPPI Journal ◽

10.32964/tj17.05.261 ◽

2018 ◽

Vol 17 (05) ◽

pp. 261-269

Author(s):

Wei Ren ◽

Brennan Dubord ◽

Jason Johnson ◽

Bruce Allison

Keyword(s):

Feedback Control ◽

Current Practice ◽

Feedforward Control ◽

Control Variable ◽

Indirect Measurement ◽

Tight Control ◽

Transfer Lines ◽

Green Liquor ◽

Process Dynamics ◽

Downstream Processes

Tight control of raw green liquor total titratable alkali (TTA) may be considered an important first step towards improving the overall economic performance of the causticizing process. Dissolving tank control is made difficult by the fact that the unknown smelt flow is highly variable and subject to runoff. High TTA variability negatively impacts operational costs through increased scaling in the dissolver and transfer lines, increased deadload in the liquor cycle, under- and over-liming, increased energy consumption, and increased maintenance. Current practice is to use feedback control to regulate the TTA to a target value through manipulation of weak wash flow while simultaneously keeping dissolver density within acceptable limits. Unfortunately, the amount of variability reduction that can be achieved by feedback control alone is fundamentally limited by the process dynamics. One way to improve upon the situation would be to measure the smelt flow and use it as a feedforward control variable. Direct measurement of smelt flow is not yet possible. The use of an indirect measurement, the dissolver vent stack temperature, is investigated in this paper as a surrogate feedforward variable for dissolving tank TTA control. Mill trials indicate that significant variability reduction in the raw green liquor TTA is possible and that the control improvements carry through to the downstream processes.

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