Utilizing Dependencies to Obtain Subsets of Reachable Sets

Reachability analysis, in general, is a fundamental method that supports formally-correct synthesis, robust model predictive control, set-based observers, fault detection, invariant computation, and conformance checking, to name but a few. In many of these applications, one requires to compute a reachable set starting within a previously computed reachable set. While it was previously required to re-compute the entire reachable set, we demonstrate that one can leverage the dependencies of states within the previously computed set. As a result, we almost instantly obtain an over-approximative subset of a previously computed reachable set by evaluating analytical maps. The advantages of our novel method are demonstrated for falsification of systems, optimization over reachable sets, and synthesizing safe maneuver automata. In all of these applications, the computation time is reduced significantly

Wireless extension to the existing SystemC design methodology

This research uses a SystemC design methodology to model and design complex wireless communication systems, because in the recent years, the complexity of wireless communication systems has increased and the modelling and design of such systems has become inefficient and challenging. The most important aspect of modelling wireless communication systems is that system design choices may affect the communication behaviour and also communication design choices may impact on the system design. Whilst, the SystemC modelling language shows great promise in the modelling of complex hardware/software systems, it still lacks a standard framework that supports modelling of wireless communication systems (particularly the use of wireless communication channels). SystemC lacks elements and components that can be used to express and simulate wireless systems. It does not support noise links natively. To fill this gap, this research proposes to extend the existing SystemC design methodology to include an efficient simulation of wireless systems. It proposes to achieve this by employing a system-level model of a noisy wireless communication channel, along with a small repertoire of standard components (which of course can be replaced on a per application basis). Finally, to validate our developed methodology, a flocking behaviour system is selected as a demonstration (case study). This is a very complex system modelled based on the developed methodology and partitioned along different parameters. By applying our developed methodology to model this system as a case study, we can prove that incorporating and fixing the wireless channel, wireless protocol, noise or all of these elements early in the design methodology is very advantageous. The modelled system is introduced to simulate the behaviour of the particles (mobile units) that form a mobile ad-hoc communication network. Wireless communication between particles is addressed with two scenarios: the first is created using a wireless channel model to link each pair of particles, which means the wireless communication between particles is addressed using a Point-to-Point (P2P) channel; the other scenario is created using a shared channel (broadcast link). Therefore, incorporating wireless features into existing SystemC design methodology, as done in this research, is a very important task, because by developing SystemC as a design tool to support wireless systems, hardware aspects, software parts and communication can be modelled, refined and validated simultaneously on the same platform, and the design space expanded into a two-dimensional design space comprising system and communication

Reducing the environmental impact of hydraulic fracturing pumps

This thesis was previously held under moratorium from 01/12/16 to 01/12/21The current approach to hydraulic fracturing requires large amounts of industrial hard-ware to be transported, installed and operated in temporary locations. Typically 70% of the mass of this equipment is comprised of the fleet of truck-mounted pumps required to provide the high pressures and flows necessary for well stimulation. The established design of these pumps were developed for the shale gas extraction industry in North America, where the environmental, geological, regulatory and social constraints are very different from Europe. Consequently the engineering choices made in the current pump designs did not focus on minimising the physical and environmental footprint of the operation. These aspects are of paramount importance for the emerging hydraulic fracturing industry in Europe, so it is timely to address these factors when considering the design of future high-pressure pumps for European shale resources. This thesis develops and applies a methodology for environmental optimisation of the key mechanical design parameters for the high-pressure pumps that are central to hydraulic fracturing operations. Before describing the optimisation methodology the thesis provides an overview of the industrial plant required to carry out a hydraulic fracturing operation, and an estimate of the functional requirements (i.e. pressure and flow) of the equipment. The computational model, central to the optimisation process, is validated by using field data from a hydraulic fracturing site in North America and an experimental test rig. The optimisation analysis concludes that reducing the plunger diameter and running the pump at higher angular velocity, with lower forces, can increase pump efficiency by up to 4.6%. Furthermore the modification of the pump’s parameters would result in several environmental benefits beyond the obvious economic gains of lower fuel con-sumption. Previous studies have shown that over 90% of the emissions of CO2 and other pollutants that occur during a hydraulic fracturing operation are associated with the pumps and their prime movers. Consequently, any increase in pumping efficiency will also reduce the greenhouse gas emissions and improve local air quality (CO2, NOx and other pollutants). Additionaly, the reduction in plunger diameter will reduce the amplitude of fatigue stresses and so increase the life of the units and allow their overall mass to be reduced. More reliable pumps could decrease the number of standby (i.e. backup) units necessary, and so reduce procurement costs and site traffic, including the overall site footprint. The concluding system optimisation study suggests that the highest level of direct on-site emission is due to the inefficient and asynchronous operation of multiple frac-truck assemblies. Reducing the number of frac-truck assemblies subsequently affects pump traffic lowering the nuisance effects to the local community such as noise, road damage and road traffic risk.The current approach to hydraulic fracturing requires large amounts of industrial hard-ware to be transported, installed and operated in temporary locations. Typically 70% of the mass of this equipment is comprised of the fleet of truck-mounted pumps required to provide the high pressures and flows necessary for well stimulation. The established design of these pumps were developed for the shale gas extraction industry in North America, where the environmental, geological, regulatory and social constraints are very different from Europe. Consequently the engineering choices made in the current pump designs did not focus on minimising the physical and environmental footprint of the operation. These aspects are of paramount importance for the emerging hydraulic fracturing industry in Europe, so it is timely to address these factors when considering the design of future high-pressure pumps for European shale resources. This thesis develops and applies a methodology for environmental optimisation of the key mechanical design parameters for the high-pressure pumps that are central to hydraulic fracturing operations. Before describing the optimisation methodology the thesis provides an overview of the industrial plant required to carry out a hydraulic fracturing operation, and an estimate of the functional requirements (i.e. pressure and flow) of the equipment. The computational model, central to the optimisation process, is validated by using field data from a hydraulic fracturing site in North America and an experimental test rig. The optimisation analysis concludes that reducing the plunger diameter and running the pump at higher angular velocity, with lower forces, can increase pump efficiency by up to 4.6%. Furthermore the modification of the pump’s parameters would result in several environmental benefits beyond the obvious economic gains of lower fuel con-sumption. Previous studies have shown that over 90% of the emissions of CO2 and other pollutants that occur during a hydraulic fracturing operation are associated with the pumps and their prime movers. Consequently, any increase in pumping efficiency will also reduce the greenhouse gas emissions and improve local air quality (CO2, NOx and other pollutants). Additionaly, the reduction in plunger diameter will reduce the amplitude of fatigue stresses and so increase the life of the units and allow their overall mass to be reduced. More reliable pumps could decrease the number of standby (i.e. backup) units necessary, and so reduce procurement costs and site traffic, including the overall site footprint. The concluding system optimisation study suggests that the highest level of direct on-site emission is due to the inefficient and asynchronous operation of multiple frac-truck assemblies. Reducing the number of frac-truck assemblies subsequently affects pump traffic lowering the nuisance effects to the local community such as noise, road damage and road traffic risk

Computer Aided Verification

This open access two-volume set LNCS 10980 and 10981 constitutes the refereed proceedings of the 30th International Conference on Computer Aided Verification, CAV 2018, held in Oxford, UK, in July 2018. The 52 full and 13 tool papers presented together with 3 invited papers and 2 tutorials were carefully reviewed and selected from 215 submissions. The papers cover a wide range of topics and techniques, from algorithmic and logical foundations of verification to practical applications in distributed, networked, cyber-physical, and autonomous systems. They are organized in topical sections on model checking, program analysis using polyhedra, synthesis, learning, runtime verification, hybrid and timed systems, tools, probabilistic systems, static analysis, theory and security, SAT, SMT and decisions procedures, concurrency, and CPS, hardware, industrial applications

Dynamic Calibration of EMG Signals for Control of a Wearable Elbow Brace

Musculoskeletal injuries can severely inhibit performance of activities of daily living. In order to regain function, rehabilitation is often required. Assistive devices for use in rehabilitation are an avenue explored to increase arm mobility by guiding therapeutic exercises or assisting with motion. Electromyography (EMG), which are the muscle activity signals, may be able to provide an intuitive interface between the patient and the device if appropriate classification models allow smart systems to relate these signals to the desired device motion. Unfortunately, there is a gap in the accuracy of pattern recognition models classifying motion in constrained laboratory environments, and large reductions in accuracy when used for detecting dynamic unconstrained movements. An understanding of combinations of motion factors (limb positions, forces, velocities) in dynamic movements affecting EMG, and ways to use information about these motion factors in control systems is lacking. The objectives of this thesis were to quantify how various motion factors affect arm muscle activations during dynamic motion, and to use these motion factors and EMG signals for detecting interaction forces between the person and the environment during motion. To address these objectives, software was developed and implemented to collect a unique dataset of EMG signals while healthy individuals performed unconstrained arm motions with combinations of arm positions, interaction forces with the environment, velocities, and types of motion. An analysis of the EMG signals and their use in training classification models to predict characteristics (arm positions, force levels, and velocities) of intended motion was completed. The results quantify how EMG features change significantly with variations in arm positions, interaction forces, and motion velocities. The results also show that pattern recognition models, usually used to detect movements, were able to detect intended characteristics of motion based solely on EMG signals, even during complex activities of daily living. Arm position during elbow flexion--extension was predicted with 83.02 % accuracy by a support vector machine model using EMG signal inputs. Prediction of force, the motion characteristic that cannot be measured without impeding motion, was improved from 76.85 % correct to 79.17 % accurate during elbow flexion--extension by providing measurable arm position and velocity information as additional inputs to a linear discriminant analysis model. The accuracy of force prediction was improved by 5.2 % (increased from 59.38 % to 64.58 %) during an activity of daily living when motion speeds were included as an input to a linear discriminant analysis model in addition to EMG signals. Future work should expand on using motion characteristics and EMG signals to identify interactions between a person and the environment, in order to guide high level tuning of control models working towards controlling wearable elbow braces during dynamic movements

Computer Aided Verification

This open access two-volume set LNCS 10980 and 10981 constitutes the refereed proceedings of the 30th International Conference on Computer Aided Verification, CAV 2018, held in Oxford, UK, in July 2018. The 52 full and 13 tool papers presented together with 3 invited papers and 2 tutorials were carefully reviewed and selected from 215 submissions. The papers cover a wide range of topics and techniques, from algorithmic and logical foundations of verification to practical applications in distributed, networked, cyber-physical, and autonomous systems. They are organized in topical sections on model checking, program analysis using polyhedra, synthesis, learning, runtime verification, hybrid and timed systems, tools, probabilistic systems, static analysis, theory and security, SAT, SMT and decisions procedures, concurrency, and CPS, hardware, industrial applications

Tools and Algorithms for the Construction and Analysis of Systems

This open access book constitutes the proceedings of the 28th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2022, which was held during April 2-7, 2022, in Munich, Germany, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2022. The 46 full papers and 4 short papers presented in this volume were carefully reviewed and selected from 159 submissions. The proceedings also contain 16 tool papers of the affiliated competition SV-Comp and 1 paper consisting of the competition report. TACAS is a forum for researchers, developers, and users interested in rigorously based tools and algorithms for the construction and analysis of systems. The conference aims to bridge the gaps between different communities with this common interest and to support them in their quest to improve the utility, reliability, exibility, and efficiency of tools and algorithms for building computer-controlled systems

A Framework for Learning by Demonstration in Multi-teacher Multi-robot Scenarios

As robots become more accessible to humans, more intuitive and human-friendly ways of programming them with interactive and group-aware behaviours are needed. This thesis addresses the gap between Learning by Demonstration and Multi-robot systems. In particular, this thesis tackles the fundamental problem of learning multi-robot cooperative behaviour from concurrent multi-teacher demonstrations, problem which had not been addressed prior to this work. The core contribution of this thesis is the design and implementation of a novel, multi- layered framework for multi-robot learning from simultaneous demonstrations, capable of deriving control policies at two different levels of abstraction. The lower level learns models of joint-actions at trajectory level, adapting such models to new scenarios via feature mapping. The higher level extracts the structure of cooperative tasks at symbolic level, generating a sequence of robot actions composing multi-robot plans. To the best of the author's knowledge, the proposed framework is the first Learning by Demonstration system to enable multiple human demonstrators to simultaneously teach group behaviour to multiple robots learners. A series of experimental tests were conducted using real robots in a real human workspace environment. The results obtained from a comprehensive comparison confirm the appli- cability of the joint-action model adaptation method utilised. What is more, the results of several trials provide evidence that the proposed framework effectively extracts rea- sonable multi-robot plans from demonstrations. In addition, a case study of the impact of human communication when using the proposed framework was conducted, suggesting no evidence that communication affects the time to completion of a task, but may have a positive effect on the extraction multi-robot plans. Furthermore, a multifaceted user study was conducted to analyse the aspects of user workload and focus of attention, as well as to evaluate the usability of the teleoperation system, highlighting which parts were necessary to be improved

Tools and Algorithms for the Construction and Analysis of Systems

This open access book constitutes the proceedings of the 28th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2022, which was held during April 2-7, 2022, in Munich, Germany, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2022. The 46 full papers and 4 short papers presented in this volume were carefully reviewed and selected from 159 submissions. The proceedings also contain 16 tool papers of the affiliated competition SV-Comp and 1 paper consisting of the competition report. TACAS is a forum for researchers, developers, and users interested in rigorously based tools and algorithms for the construction and analysis of systems. The conference aims to bridge the gaps between different communities with this common interest and to support them in their quest to improve the utility, reliability, exibility, and efficiency of tools and algorithms for building computer-controlled systems