Neural conduction delay is a serious issue for organisms that need to act in real time. Perceptual phenomena such as the flash-lag effect (FLE, where the position of a moving object is perceived to be ahead of a brief flash when they are actually colocalized) suggest that the nervous system may perform extrapolation to compensate for delay. However, the precise neural mechanism for extrapolation has not been fully investigated. The main hypothesis of this dissertation is that facilitating synapses, with their dynamic sensitivity to the rate of change in the input, can serve as a neural basis for extrapolation. To test this hypothesis, computational and biologically inspired models are proposed in this dissertation. (1) The facilitatory activation model (FAM) was derived and tested in the motion FLE domain, showing that FAM with smoothing can account for human data. (2) FAM was given a neurophysiological ground by incorporating a spike-based model of facilitating synapses. The spike-based FAM was tested in the luminance FLE domain, successfully explaining extrapolation in both increasing and decreasing luminance conditions. Also, inhibitory backward masking was suggested as a potential cellular mechanism accounting for the smoothing effect. (3) The spike-based FAM was extended by combining it with spike-timing-dependent plasticity (STDP), which allows facilitation to go across multiple neurons. Through STDP, facilitation can selectively propagate to a specific direction, which enables the multi-neuron FAM to express behavior consistent with orientation FLE. (4) FAM was applied to a modified 2D pole-balancing problem to test whether the biologically inspired delay compensation model can be utilized in engineering domains. Experimental results suggest that facilitating activity greatly enhances real time control performance under various forms of input delay as well as under increasing delay and input blank-out conditions. The main contribution of this dissertation is that it shows an intimate link between the organism-level problem of delay compensation, perceptual phenomenon of FLE, computational function of extrapolation, and neurophysiological mechanisms of facilitating synapses (and STDP). The results are expected to shed new light on real-time and predictive processing in the brain, and help understand specific neural processes such as facilitating synapses.

Switched reluctance motors (SRMs) are becoming popular in motor drive applications due to their simple construction, fault tolerance, and cost-effectiveness, making them well-suited for electric vehicles. However, SRMs face operational challenges at high speeds, where controller and position feedback delays may hinder smooth operation and efficiency. These challenges might limit the adoption of SRM in high-performance applications. This thesis addresses high-speed SRM control issues, focusing on delay compensation in both motoring and generating modes. Gain-scheduling PWM controller improvements and delay compensation strategies are presented to reduce the impact of position and switching delays at high-speed operation. Additionally, a four-quadrant SRM controller is proposed to enable smooth operation mode transitions and improved regenerative braking capability. A dedicated experimental setup with a three-phase 12/8 SRM connected to an electric dynamometer machine is built to validate the proposed techniques and demonstrate the improvements in the phase excitation accuracy and balance in phase currents at high speeds. The experimental results support the potential of these control methods to enhance SRM performance in high-speed applications, providing valuable insights for further improvement in electric vehicle drive train applications. / Thesis / Master of Applied Science (MASc)

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / In many test ranges, it is often required to acquire a number of telemetry streams and to process the data simultaneously. Frequently, the streams have different delay characteristics, requiring temporal alignment before the processing step. It is desired to have the capability to align these streams so that the events in each stream are coincident in time. Terawave Communications has developed technology to perform temporal alignment for a number of streams automatically. Additionally, the algorithm performs the delay compensation independent of the source data rate of each stream. Terawave will present the algorithm and share the results of their testing in a test installation.

International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / A system to generate a contiguous high speed time division multiplexed (TDM) spacecraft downlink data stream has been developed. The 25 MBPS downlink data stream contains high rate real time imager data, intermediate rate subsystem processor data, and low rate spacecraft housekeeping data. Imager data is transferred directly into the appropriate TDM downlink data window using control signals and clocks generated in the central data formatter and distributed to the data sources. Cable and electronics delays inherent in this process can amount to several clock periods, while the uncertainty and variations in those delays (e.g. temperature effects) can exceed the clock period. Unique (patent pending) electronic circuitry has been included in the data formatter to sense the total data gathering delay for each high speed data source and use the results to control series programmable delay elements to equalize the delays from all sources and permit the formation of a contiguous output data stream.

Advances in computer networks and rendering systems facilitate the creation of distributed collaborative environments in which the distribution of information at remote locations allows efficient communication. Particularly challenging are distributed interactive Virtual Environments (VE) that allow knowledge sharing through 3D information. In a distributed interactive VE the dynamic shared state represents the changing information that multiple machines must maintain about the shared virtual components. One of the challenges in such environments is maintaining a consistent view of the dynamic shared state in the presence of inevitable network latency and jitter. A consistent view of the shared scene will significantly increase the sense of presence among participants and facilitate their interactive collaboration. The purpose of this work is to address the problem of latency in distributed interactive VE and to develop a conceptual model for consistency maintenance in these environments based on the participant interaction model. A review of the literature illustrates that the techniques for consistency maintenance in distributed Virtual Reality (VR) environments can be roughly grouped into three categories: centralized information management, prediction through dead reckoning algorithms, and frequent state regeneration. Additional resource management methods can be applied across these techniques for shared state consistency improvement. Some of these techniques are related to the systems infrastructure, others are related to the human nature of the participants (e.g., human perceptual limitations, area of interest management, and visual and temporal perception). An area that needs to be explored is the relationship between the dynamic shared state and the interaction with the virtual entities present in the shared scene. Mixed Reality (MR) and VR environments must bring the human participant interaction into the loop through a wide range of electronic motion sensors, and haptic devices. Part of the work presented here defines a novel criterion for categorization of distributed interactive VE and introduces, as well as analyzes, an adaptive synchronization algorithm for consistency maintenance in such environments. As part of the work, a distributed interactive Augmented Reality (AR) testbed and the algorithm implementation details are presented. Currently the testbed is part of several research efforts at the Optical Diagnostics and Applications Laboratory including 3D visualization applications using custom built head-mounted displays (HMDs) with optical motion tracking and a medical training prototype for endotracheal intubation and medical prognostics. An objective method using quaternion calculus is applied for the algorithm assessment. In spite of significant network latency, results show that the dynamic shared state can be maintained consistent at multiple remotely located sites. In further consideration of the latency problems and in the light of the current trends in interactive distributed VE applications, we propose a hybrid distributed system architecture for sensor-based distributed VE that has the potential to improve the system real-time behavior and scalability.

In this thesis, an optimal multivariable current control method is presented for the highspeed permanent magnet synchronous motor (HS-PMSM). The HS-PMSMs have growing applications in the industry. One of their major challenges is the low switching to fundamental frequency ratio (SFR). At high speed and low SFR, the control time delays including the digital, the PWM, and sensor delays become more pronounced and lead to oscillations and even instabilities. A well-known method for delay compensation is to advance the phase angle of control input for a known amount. In practice, the exact delay is unknown, and mismatch in the compensating angle causes deteriorating effect on the system. In the proposed method, the digital and PWM delays are modelled and integrated with an optimal multivariable controller. This method improves the stability margin and achievable speed margin compared to the traditional phase advancing delay compensation (PADC) method. Combining the proposed delay modeling and the PADC method further improves the response, as the uncertain sensor delays can be compensated greatly. Besides the delay, the cross-coupling between ���� axis affects the dynamic performance of the machine. The proposed multivariable approach considers and directly addresses the coupling. Dynamic performance of the PMSM with the proposed method is thoroughly compared with the conventional delay compensation method. The proposed method is validated through extensive simulation studies on a 2 kW high-speed machine.

A novel hybrid pulse-width modulation (PWM) update method is proposed to eliminate the effect of the one-step control time delay Td one without losing the full duty cycle range. Without the Td one to cause linear phase shifts that limit the control bandwidth and affect closed-loop stability, a very high quality digital current control can be achieved, such as a high closed current loop bandwidth, strong robustness against disturbances, ability to reach a very high fundamental frequency compared to switching frequency, etc. In a conventional digital control implementation, a sampling period (Tsamp) is allocated for the execution of samplings and computations, and the update of PWM outputs is delayed until the beginning of the following sampling period. This delayed PWM update method is the cause of the Td one. Instead of the delayed PWM update, if the PWM outputs are updated immediately after algorithm computations, then the effect of the Td one can be eliminated; however, the computation time delay Td comp from the current sampling instant through algorithm computations to the PWM update instant causes a reduced duty cycle range. Each of these two conventional PWM update methods has some shortcomings. A hybrid PWM update method is proposed to circumvent the aforementioned shortcomings and to incorporate only the advantages. The proposed method improves the performance by updating the PWM outputs multiple times during a Tsamp, whereas the PWM outputs are updated only one time during a Tsamp in the conventional methods. In spite of the simplicity of the proposed method, the performance improvements in stability, robustness and response characteristics are significant. On the other hand, the proposed method can be easily applied to many PWM based digital controls because of its simplicity. Additional to the hybrid PWM update method, a hybrid control method is proposed to optimize the sequence of control operations. It maximizes the current loops' robustness and minimizes the delay from the sampling of outer control loops' variables, such as voltage and speed, to the duty cycle update instant. The minimum delay enables the maximization of the outer control loops' bandwidth. Additionally, a corrective neutral offset voltage injection method is proposed to correct small PWM output deviations that may occur with the hybrid PWM update method. Utilizing a three-phase voltage source inverter with a permanent magnet synchronous machine as the platform, a deadbeat current control and a high speed ac drive experiments have been conducted to demonstrate the feasibility and validity. Notable results include a closed current loop response of one Tsamp with the deadbeat control and a 500 Hz current fundamental frequency with 1 kHz switching frequency in the high speed ac drive. / Ph. D. / A novel hybrid pulse-width modulation (PWM) update method is proposed to improve the performance of power electronics applications. PWM is a modulation technique that is typically used in power electronics to encode a control signal. A delayed PWM update method and an immediate PWM update method are two conventional PWM update methods, and each of these conventional methods has shortcomings. The delayed PWM update method, as the name implies, delays the update of PWM outputs until the beginning of next cycle. This delayed update ensures that PWM signals have the full range; however, it causes an update delay in control loops, which degrades the control loops’ response speed. On the other hand, the immediate PWM update method, as the name implies, the update of PWM outputs is executed as soon as the control signals are available to be updated. This immediate update eliminates the update delay, but it loses the full range of PWM signals. The hybrid PWM update method is proposed to combine the delayed and immediate PWM update methods, in which the combination can eliminate the update delay without the loss of the full signal range. The proposed method is quite simple; however, the performance improvements in stability, robustness, and response characteristics are significant. On the other hand, the proposed method can be easily applied to many PWM based digital controls because of its simplicity. The proposed method is implemented on a three-phase voltage source inverter with a permanent magnet synchronous machine, and the feasibility and validity are demonstrated with a deadbeat current control algorithm and a high speed ac drive experiment. In the experiments, a very high quality digital current control is achieved, such as a high closed current loop bandwidth, strong robustness against disturbances, ability to reach a very high fundamental frequency compared to switching frequency, etc.

L’efficacité du système visuel est permise par un complexe réseau d’élaboration, qui s’appuie sur des structures corticales, sous-corticales et périphériques. Le but de la présente recherche est de mieux comprendre le processus de perception visuelle du mouvement, et réaliser un modèle computationnel capable de reproduire les fonctionnalités humaines du tracking (suivi) d'un objet en mouvement. Ce travail de thèse comprend une ample recherche bibliographique, ainsi qu’une série d’expérimentations ; la thèse se compose de deux parties :La première partie a pour objet la détermination des performances dans l’inférence « vers le passé », d’un mouvement partiellement visible. Il s’agit de définir l’implication des informations exogènes (les signaux rétiniens) et endogènes (les modèles internes de l’action observée) dans la reconstruction de la cinématique d’une cible en mouvement et partiellement occultée. Nos résultats supportent l’hypothèse que le Système Nerveux Central adopte un mécanisme basé sur le recours aux modèles internes dans la reconstruction du passé de cinématiques biologiques. La deuxième partie complémente la première, et vise à identifier la structure et les caractéristiques fonctionnelles du système de poursuite, ainsi que à comprendre l’origine des erreurs systématiques présentes dans la localisation d’une cible chez l’homme. Nous avons développé un modèle computationnel en langage Matlab, basé sur le mécanisme d’extrapolation du mouvement, qui est capable de reproduire les données expérimentales dans la tâche de localisation / The effectiveness of the visual system is permitted by a complex processing network, which relies on cortical, sub-cortical and peripheral structures. The purpose of this research is to improve the knowledge of the process sustaining the visual perception of motion, and to produce a computational model able to reproduce the features of human visual tracking of a moving object.This work includes an extensive bibliographic research, and a series of experiments. The thesis consists of two parts:The first part pertains to the determination of performance in the "backward" inference of a partially visible movement. It consist of defining the involvement of exogenous information (retinal signals) and endogenous information (internal models of observed action) in the kinematic reconstruction of a partially hidden trajectory of a moving target. Our results support the hypothesis that the CNS adopts a mechanism based on the use of internal models in the reconstruction of past biological kinematics.The second part complements the first one, and aims to identify the structure and the functional characteristics of the tracking system; it also aims to understand the origin of systematic errors present in the location of a target, in humans.We developed a computational model in Matlab, based on the extrapolation mechanism of movement, which is capable of reproducing the experimental data for the localization task

This study investigates whether different stereo techniques used as a main array influences the preferred level from spot microphones when combined in a mix. Time delay compensation and its influence on spot microphone level was also examined. A clarinet soloist and a violin & piano duo were recorded as stimuli. A listening test was conducted where subjects were asked to set the level on spot microphone channels of a clarinet, and violin in combination with several stereo techniques. A/B, X/Y, ORTF, and Blumlein were examined. In general, results suggested that there wasn’t a significant difference in preferred spot microphone level between stereo techniques. Time delay compensation could not be proven to significantly influence the preferred spot microphone level.

Many control algorithms for ABS systems have been proposed in the literature since the introduction of this equipment by Bosch in 1978. In general, one can divide these control algorithms into two different types: those based on a regulation logic with wheel acceleration thresholds that are used by most commercial ABS systems; and those based on wheel slip control that are preferred in the large majority of academic algorithms. Each approach has its pros and cons [Shida 2010]. Oversimplifying, one can say that the strength of the first ones is their robustness; while that of the latter ones their short braking distances (on dry grounds) and their absence of limit cycles. At the midpoint of this industry/academy dichotomy, based on the concept of extended braking stiffness (XBS), a quite different class of ABS control strategies has been proposed by several researchers (see, e.g., [Sugai 1999] and [Ono 2003]). This concept combines the advantages from both the industrial and academic approaches. Nevertheless, since the slope of the tyre characteristic is not directly measurable, it introduces the question of real-time XBS estimation. The first part of this thesis is devoted to the study of this estimation problem and to a generalization of the proposed technique to a larger class of systems. From the technological point of view, the design of ABS control systems is highly dependent on the ABS system characteristics and actuator performance. Current ABS control algorithms on passenger cars, for instance the Bosch ABS algorithm, are based on heuristics that are deeply associated to the hydraulic nature of the actuator. An interesting observation is that they seem to work properly only in the presence of a specific delay coming from the hydraulic actuation [Gerard 2012]. For brake systems that have different delays compared to those of hydraulic actuators, like electric in-wheel motors (with a smaller delay) or pneumatic trailer brakes (with a bigger delay), they might be no longer suitable [Miller 2013]. Therefore, adapting standard ABS algorithms to other advanced actuators becomes an imperative goal in the automobile industry. This goal can be reached by the compensation of the delays induced by actuators. The second part of this thesis is focused on this issue, and to the generalization of the proposed technique to a particular class of nonlinear systems. Throughout this thesis, we employ two different linearization techniques: the linearization of the error dynamics in the construction of model-based observers [Krener 1983] and the linearization based on restricted state feedback [Brockett 1979]. The former is one of the simplest ways to build an observer for dynamical systems with output and to analyze its convergence. The main idea is to transform the original nonlinear system via a coordinate change to a special form that admits an observer with a linear error dynamics and thus the observer gains can be easily computed to ensure the observer convergence. The latter is a classical method to control nonlinear systems by converting them into a controllable linear state equation via the cancellation of their nonlinearities. It is worth mentioning that existing results for observer design by error linearization in the literature are only applied to the case of regular time scalings ([Guay 2002] and [Respondek 2004]). The thesis shows how to extend them to the case of singular time scalings. Besides, the thesis combines the classical state feedback linearization with a new method for the input delay compensation to resolve the output tracking problem for restricted feedback linearizable systems with input delays.