Passivity Degradation In Discrete Control Implementations: An Approximate Bisimulation Approach

In this paper, we present some preliminary results for compositional analysis of heterogeneous systems containing both discrete state models and continuous systems using consistent notions of dissipativity and passivity. We study the following problem: given a physical plant model and a continuous feedback controller designed using traditional control techniques, how is the closed-loop passivity affected when the continuous controller is replaced by a discrete (i.e., symbolic) implementation within this framework? Specifically, we give quantitative results on performance degradation when the discrete control implementation is approximately bisimilar to the continuous controller, and based on them, we provide conditions that guarantee the boundedness property of the closed-loop system.Comment: This is an extended version of our IEEE CDC 2015 paper to appear in Japa

A review of advances in pixel detectors for experiments with high rate and radiation

The Large Hadron Collider (LHC) experiments ATLAS and CMS have established hybrid pixel detectors as the instrument of choice for particle tracking and vertexing in high rate and radiation environments, as they operate close to the LHC interaction points. With the High Luminosity-LHC upgrade now in sight, for which the tracking detectors will be completely replaced, new generations of pixel detectors are being devised. They have to address enormous challenges in terms of data throughput and radiation levels, ionizing and non-ionizing, that harm the sensing and readout parts of pixel detectors alike. Advances in microelectronics and microprocessing technologies now enable large scale detector designs with unprecedented performance in measurement precision (space and time), radiation hard sensors and readout chips, hybridization techniques, lightweight supports, and fully monolithic approaches to meet these challenges. This paper reviews the world-wide effort on these developments.Comment: 84 pages with 46 figures. Review article.For submission to Rep. Prog. Phy

Trust-Based Control of (Semi)Autonomous Mobile Robotic Systems

Despite great achievements made in (semi)autonomous robotic systems, human participa-tion is still an essential part, especially for decision-making about the autonomy allocation of robots in complex and uncertain environments. However, human decisions may not be optimal due to limited cognitive capacities and subjective human factors. In human-robot interaction (HRI), trust is a major factor that determines humans use of autonomy. Over/under trust may lead to dispro-portionate autonomy allocation, resulting in decreased task performance and/or increased human workload. In this work, we develop automated decision-making aids utilizing computational trust models to help human operators achieve a more effective and unbiased allocation. Our proposed decision aids resemble the way that humans make an autonomy allocation decision, however, are unbiased and aim to reduce human workload, improve the overall performance, and result in higher acceptance by a human. We consider two types of autonomy control schemes for (semi)autonomous mobile robotic systems. The first type is a two-level control scheme which includes switches between either manual or autonomous control modes. For this type, we propose automated decision aids via a computational trust and self-confidence model. We provide analytical tools to investigate the steady-state effects of the proposed autonomy allocation scheme on robot performance and human workload. We also develop an autonomous decision pattern correction algorithm using a nonlinear model predictive control to help the human gradually adapt to a better allocation pattern. The second type is a mixed-initiative bilateral teleoperation control scheme which requires mixing of autonomous and manual control. For this type, we utilize computational two-way trust models. Here, mixed-initiative is enabled by scaling the manual and autonomous control inputs with a function of computational human-to-robot trust. The haptic force feedback cue sent by the robot is dynamically scaled with a function of computational robot-to-human trust to reduce humans physical workload. Using the proposed control schemes, our human-in-the-loop tests show that the trust-based automated decision aids generally improve the overall robot performance and reduce the operator workload compared to a manual allocation scheme. The proposed decision aids are also generally preferred and trusted by the participants. Finally, the trust-based control schemes are extended to the single-operator-multi-robot applications. A theoretical control framework is developed for these applications and the stability and convergence issues under the switching scheme between different robots are addressed via passivity based measures

Chemical Bionics - a novel design approach using ion sensitive field effect transistors

In the late 1980s Carver Mead introduced Neuromorphic engineering in which various aspects of the neural systems of the body were modelled using VLSI1 circuits. As a result most bio-inspired systems to date concentrate on modelling the electrical behaviour of neural systems such as the eyes, ears and brain. The reality is however that biological systems rely on chemical as well as electrical principles in order to function. This thesis introduces chemical bionics in which the chemically-dependent physiology of specific cells in the body is implemented for the development of novel bio-inspired therapeutic devices. The glucose dependent pancreatic beta cell is shown to be one such cell, that is designed and fabricated to form the first silicon metabolic cell. By replicating the bursting behaviour of biological beta cells, which respond to changes in blood glucose, a bio-inspired prosthetic for glucose homeostasis of Type I diabetes is demonstrated. To compliment this, research to further develop the Ion Sensitive Field Effect Transistor (ISFET) on unmodified CMOS is also presented for use as a monolithic sensor for chemical bionic systems. Problems arising by using the native passivation of CMOS as a sensing surface are described and methods of compensation are presented. A model for the operation of the device in weak inversion is also proposed for exploitation of its physical primitives to make novel monolithic solutions. Functional implementations in various technologies is also detailed to allow future implementations chemical bionic circuits. Finally the ISFET integrate and fire neuron, which is the first of its kind, is presented to be used as a chemical based building block for many existing neuromorphic circuits. As an example of this a chemical imager is described for spatio-temporal monitoring of chemical species and an acid base discriminator for monitoring changes in concentration around a fixed threshold is also proposed

Integrated chirped Bragg gratings for dispersion control

In this work, the need for an integrated optical dispersive device is discussed, with particular reference to pulse compression of semiconductor mode-locked laser (MLL) pulses that exhibit temporal chirp and therefore, worse than transform limited behaviour. It is shown that current techniques in fibre and integrated dispersion control do not overlap the dispersion regime presented, making it necessary to design a new integrated device for this purpose. A monolithic chirped Bragg grating is presented with dispersion and bandwidth characteristics coinciding with the previously mentioned regimes. The device, based on a deeply etched tapered waveguide design, may be fabricated fully post-growth, lending it a significant advantage over current grating designs that require the pattern to be written into the core material and the upper cladding layers subsequently overgrown. The deeply etched sidewall grating structures provide the requisite high coupling coefficients, and the ability to induce arbitrary apodisation profiles, while the tapered waveguide design allows the same freedom the grating Bragg condition profile. The coupled-mode analysis for a chirped grating structure is presented and used as a basis for a Transfer Matrix Method (TMM) representation of the device. This simulation tool allows modelling of the arbitrary Bragg condition and apodisation profiles for steady state analysis of passive grating devices, Distributed Feedback (DFB) and Distributed Bragg Reflector (DBR) lasers. The fabrication of low loss passive grating devices and DFB lasers is described with particular attention paid to lithography and reactive ion etching methods. In addition, work is presented on a wet chemical oxidation technique for reduction of sidewall roughness in A1GaAs based waveguides. Deeply etched waveguides were shown to exhibit losses reduced by up to 4dBcm[superscript-1] after application of this procedure. The fabricated passive grating devices exhibit transmission and grating phase profiles closely matching those predicted by the simulations, with control shown over both Bragg condition and coupling coefficient. The DFB lasers, again in agreement with simulation, show unique multi-mode behaviour, closely related to the chirped grating modulation profile. Also presented is a method by which sub-100 [m] tapers for transitions between shallow etched and deep etched waveguides may be fabricated for quasi-adiabatic propagation. These tapers provide a means by which integration may be achieved between optical systems with different mode profiles, these being defined by device properties, for example integration of small radius bends and waveguide gain structures. A simulation tool based on teh TMM is derived and a set of optimised tapers are fabricated, their results matched to the simulations. Low loss, low reflectivity tapers are exhibited with properties in close agreement with teh TMM and Finite Difference Time Doain (FDTD) simulations