Safety control with performance guarantees of cooperative systems using compositional abstractions

International audienceIn this paper, the monotonicity property is exploited to obtain symbolic abstractions, in the sense of alternating simulation, of a class of nonlinear control systems subject to disturbances. Both a centralized and a compositional approaches are presented to obtain such abstractions, from which controllers are synthesized to satisfy safety specifications and optimize a performance criterion using a receding horizon approach. Performance guarantees on the trajectories of the controlled system can be obtained with both approaches. The controller synthesis and performance guarantees are illustrated and compared on the temperature regulation in a building

Controllability and invariance of monotone systems for robust ventilation automation in buildings

International audienceThe problem considered is the temperature control in a building equipped with UnderFloor Air Distribution (UFAD). Its 0-D model is derived from the energy and mass conservation in each room, and also presents discrete components to describe the disturbances from heat sources and doors opening. Using the monotonicity of this model, we can characterize two concepts of robust control, the Robust Controllability and the Robust Controlled Invariance introduced in this paper, and determine their limits for control design objectives. The validity of these results is then illustrated in a simulation of a two-room example

Formal Synthesis of Control Strategies for Positive Monotone Systems

We design controllers from formal specifications for positive discrete-time monotone systems that are subject to bounded disturbances. Such systems are widely used to model the dynamics of transportation and biological networks. The specifications are described using signal temporal logic (STL), which can express a broad range of temporal properties. We formulate the problem as a mixed-integer linear program (MILP) and show that under the assumptions made in this paper, which are not restrictive for traffic applications, the existence of open-loop control policies is sufficient and almost necessary to ensure the satisfaction of STL formulas. We establish a relation between satisfaction of STL formulas in infinite time and set-invariance theories and provide an efficient method to compute robust control invariant sets in high dimensions. We also develop a robust model predictive framework to plan controls optimally while ensuring the satisfaction of the specification. Illustrative examples and a traffic management case study are included.Comment: To appear in IEEE Transactions on Automatic Control (TAC) (2018), 16 pages, double colum

Peering In: Improving Existing Buildings with Colorful Increments

Existing office buildings’ embodied energy, history and culture offer something a newly constructed building cannot. On the other hand, new office buildings’ adoption of new technologies and building philosophies offer a range of sustainable efficiencies previously unavailable. Combining these efficiencies with elements that embrace human diversity and well- being offer the opportunity to not only mend our existing buildings’ deteriorating physical bodies but aid in creating workplaces that promote good physical and mental health. This project provides recommendation on how an existing high-rise commercial building can incorporate a number of incremental improvements that continually evolve to meet rapidly changing market demands. This design approach allows for ease of installation and modification to meet the needs of the tenants and the building owner

A study of the characteristics of natural light in selected buildings designed by Le Corbusier, Louis I. Kahn and Tadao Ando

The thesis discusses the characteristics of natural light that are visible inside concrete buildings designed in the late twentieth century. The study addresses three major objectives. First is to identify the characteristics of natural light visible inside these spaces. Second is to understand the use of natural light to illuminate different spaces. Third is to explore the relation between the characteristics of natural light and the overall perception of the space. With these objectives in mind, a comprehensive literature review was done to develop the hypotheses for this thesis. The first hypothesis states that the overall perception of a space is affected by certain basic characteristics of natural light. The second hypothesis suggests that the overall character of a space can be enhanced by emphasizing the source of natural light as a visual element. To test these hypotheses, this thesis studies the effect of natural light in three buildings made out of reinforced concrete in the late twentieth century. The three buildings are the Chapel of Notre Dame du Haut Ronchamp by Le Corbusier, the Kimbell Art Museum by Louis I. Kahn and the Church of the Light by Tadao Ando. The method of analysis is based on the selection of a spatial envelope in each building that helps to provide an ideal framework for studying the effects of light. The method takes into consideration the principles of visual perception and the use of images depicting the varied effects of light inside the spatial envelope. The results of the analysis show that the three projects employ similar design principles to achieve some of the common effects of light, and the listed characteristics of light in relation to the overall perception of the space do not vary to a great extent when moving from one project to another. The emphasis on the source of natural light is a common and recurring theme in all three buildings. The thesis concludes that the results support the hypotheses, and that the quality of a space is dependent upon the way a designer brings natural light into the space

Designing for adaptability in architecture

The research is framed on the premise that designing buildings that can adapt by accommodating change easier and more cost-effectively provides an effective means to a desired end a more sustainable built environment. In this context, adaptability can be viewed as a means to decrease the amount of new construction (reduce), (re)activate underused or vacant building stock (reuse) and enhance disassembly/ deconstruction of components (reuse, recycle) - prolonging the useful life of buildings (reduce, reuse, recycle). The aim of the research is to gain a holistic overview of the concept of adaptability in the construction industry and provide an improved framework to design for, deploy and implement adaptability. An over-arching research question was posited to guide the inquiry: how can architects understand, communicate, design for and test the concept of adaptability in the context of the design process? The research followed Dubois and Gadde s (2002) systematic combining as an over-arching approach that continuously moves between the empirical world and theoretical models allowing the co-evolution of data collection and theory from the beginning as part of a non-linear process with the objective of matching theory with reality. An initial framework was abducted from a preliminary collection of data from which a set of mixed research methods was deployed to explore adaptability (interviews, building case studies, dependency structural matrices, practitioner surveys and workshop). Emergent from the data is an expanded and revised theory on designing for adaptability consisting of concepts, models and propositions. The models illustrate many of the casual links between the physical design structure of the building (e.g. plan depth, storey height) and the soft contingencies of a messy design/construction/occupation process (e.g. procurement route, funding methods, stakeholder mindsets). In an effort to enhance building adaptability, the abducted propositions suggest a shift in the way the industry values buildings and conducts aspects of the design process and how designer s approach designing for adaptability

Formal methods for resilient control

Many systems operate in uncertain, possibly adversarial environments, and their successful operation is contingent upon satisfying specific requirements, optimal performance, and ability to recover from unexpected situations. Examples are prevalent in many engineering disciplines such as transportation, robotics, energy, and biological systems. This thesis studies designing correct, resilient, and optimal controllers for discrete-time complex systems from elaborate, possibly vague, specifications. The first part of the contributions of this thesis is a framework for optimal control of non-deterministic hybrid systems from specifications described by signal temporal logic (STL), which can express a broad spectrum of interesting properties. The method is optimization-based and has several advantages over the existing techniques. When satisfying the specification is impossible, the degree of violation - characterized by STL quantitative semantics - is minimized. The computational limitations are discussed. The focus of second part is on specific types of systems and specifications for which controllers are synthesized efficiently. A class of monotone systems is introduced for which formal synthesis is scalable and almost complete. It is shown that hybrid macroscopic traffic models fall into this class. Novel techniques in modular verification and synthesis are employed for distributed optimal control, and their usefulness is shown for large-scale traffic management. Apart from monotone systems, a method is introduced for robust constrained control of networked linear systems with communication constraints. Case studies on longitudinal control of vehicular platoons are presented. The third part is about learning-based control with formal guarantees. Two approaches are studied. First, a formal perspective on adaptive control is provided in which the model is represented by a parametric transition system, and the specification is captured by an automaton. A correct-by-construction framework is developed such that the controller infers the actual parameters and plans accordingly for all possible future transitions and inferences. The second approach is based on hybrid model identification using input-output data. By assuming some limited knowledge of the range of system behaviors, theoretical performance guarantees are provided on implementing the controller designed for the identified model on the original unknown system

Sustainability in design: now! Challenges and opportunities for design research, education and practice in the XXI century

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