A Software Toolchain for Physical System Description and Synthesis, and Applications to Microfluidic Design Automation

Microfluidic circuits are currently designed by hand, using a combination of the designer’s domain knowledge and educated intuition to determine unknown design parameters. As no microfluidic circuit design software exists to assist designers, circuits are typically tested by physically constructing them in silico and performing another design iteration should the prototype fail to operate correctly. Similar to how electronic design automation tools revolutionized the digital circuit design process, so too do microfluidic design packages have the potential to increase productivity for microfluidic circuit designers and allow more complex devices to be designed. Two of the primary software engineering problems to be solved in this space relate to design entry and design synthesis. First, the circuit designer requires a programming language to describe the behaviour and properties of the device they wish to build, and a compiler toolchain to convert this description into a model that can then be processed by other software tools. Second, once such a model is constructed, the remaining portions of the design toolchain must be constructed. It is necessary to implement software that can find unknown design parameters automatically to relieve the designer of much of the complexity that goes into creating such a circuit. Furthermore, automated testing and verification tools must be used to simulate the device and check for correctness and safety requirements before the engineer can have confidence in their design. In this thesis I outline work that has been done towards both of these goals. First, I describe a new programming language that has been developed for the purpose of describing and modelling physical systems, including but not limited to microfluidic circuits. This programming language, called “Manifold”, has been implemented following principles and features of modern functional programming languages, as well as drawing inspiration from VHDL and Verilog, the two industry-standard programming languages for EDA. The Manifold high-level language compiler carries out the process of translating a system description into a domain-agnostic intermediate representation. This representation is then passed to a domain-specific backend compiler which can perform further operations on the design, such as creating simulations, performing verification, and generating appropriate output products. Second, I perform a case study with respect to the creation of such a domain-specific backend for the domain of multi-phase microfluidic circuits. The process involved in taking a circuit description from design entry to device specification has a number of significant steps. I discuss in detail these steps with respect to the design of a multi-way droplet generator circuit. Such a circuit is difficult to design because of the behaviour of the key design parameter, the volume of generated droplets. The design goal is for each droplet generator on the device to produce droplets of a certain specified volume. However, the equation relating the properties of a droplet generator to the predicted droplet volume is complex and contains several nonlinearities, making it very difficult to solve by traditional methods. Recent advances in constraint solvers which can reason about nonlinear equations over real-valued terms make it possible to solve this equation efficiently for a given set of design constraints and goals, and produce many feasible specifications for droplet generators that meet the requirements. Another difficulty in designing these circuits is due to interactions between droplet generators. As the produced droplets have a significant hydrodynamic resistance, they affect the behaviour of the circuit by causing perturbations in the flow rates into the droplet generators. This has the potential to alter the volume of droplets that are being produced. Therefore, a means of regulating or controlling the flow rates must be found. I describe a potential solution in the form of a passive element analogous to a capacitor in an electrical circuit. Once an appropriate value for the capacitor is chosen, it remains to verify that it operates correctly under manufacturing variances in fabrication of the device. To perform this verification, a bounded model checker for real-valued differential equations is employed to demonstrate correctness or discover robustness issues. Furthermore, a simulation file for the MapleSim numerical simulation engine is generated in order to perform whole-design tests for further validation. The sequence in which these steps are performed closely follows the concept of “abstraction refinement” in formal methods, in which successively more detailed models are checked and a failure in one step can invoke a previous step with new information, allowing errors to be caught early and introducing the ability to iterate on the design. I describe such a refinement loop in place in the microfluidics backend that integrates these three steps in a coherent design flow, able to synthesize and verify many specifications for a microfluidic circuit, thereby automating a significant portion of the design process. The combination of the Manifold high-level language and microfluidics backend introduces a new design automation toolchain that demonstrates the effectiveness of constraint solvers in the tasks of design synthesis and verification. Further enhancements to the performance and capabilities of these solvers, as well as to the high-level language and backend, will in the future produce a general-purpose design package for microfluidic circuits that will allow for new, complex designs to be created and checked with confidence

Dual Input Microinverter for Tandem Cells

For every solar panel, there is an inverter which transforms the harvested DC electricity into AC electricity so that it can connect to the grid and power household appliances. In this project, we examined a tandem solar cell being designed by Iris Photovoltaics which has two layers with two distinct outputs, and we explored several solutions to create a microinverter which can handle dual inputs from the tandem PV and combine them into a single AC output. To examine the viability of such a microinverter, we designed and simulated the DC-DC combination portion of the specialized dual input microinverter, resulting in a working circuit simulation using flyback transformers which can take two DC inputs at different voltage and current levels and combine them together into a single high voltage on the DC bus, ready to be transformed into AC. We also purchased an already existing dual input microinverter and tested it by connecting it with two different solar panels and measuring its performance, however we could not obtain useful results because it did not function as intended. Overall the dual input microinverter is an interesting technology involving maximum power point tracking, DC combination, and power electronics. It has a multitude of applications, and it fits perfectly with the 4-terminal tandem solar module being developed by Iris Photovoltaics

Hissin nappikonstruktion suunnittelu lisääville valmistusmenetelmille

Additive manufacturing, with its recent technological developments, has increasingly disrupted how products are designed and manufactured. Within additive manufacturing, there has been a shift from the production of visual models and rapid prototyping applications to direct digital manufacturing of end products. Additive manufacturing provides intriguing possibilities in the design of new and existing products. These radical, pioneering designs have already redefined whole industries. This thesis provides a practical case study for an additive manufacturing redesign together with a literature review of the current additive manufacturing technologies and applications. The target of the redesign was a low volume elevator button assembly. Concepts were prototyped and tested in contrast to the current industry specification. As a result of the thesis, a functional button assembly was produced and tested. The part count, material usage, and costs were reduced compared to the original. However, all industry requirements were not met. A need for a more systematic material and process selection was identified. Nevertheless, additive manufacturing was proven to be a serious alternative in the production of low volume plastic products and should be researched further.Lisäävien valmistusmenetelmien teknologinen kehitys vaikuttaa enenevissä määrin siihen, miten fyysisiä tuotteita valmistetaan. Visuaalisten- sekä pikamallien tulostuksesta ollaan siirtymässä lopputuotteiden suoraan valmistukseen. Geometristen rajoitusten vähyys luo kiinnostavia mahdollisuuksia uusien ja olemassa olevien tuotteiden suunnittelussa. Uudet radikaalit ja uraauurtavat tuotteet ovat jo määrittäneet uudelleen kokonaisia toimialoja. Tämän diplomityön käytännön osuudessa suunnittellaan hissin nappikonstruktio täysin uusiksi lisäävien valmistusmenetelmien näkökulmasta. Työ tarjoaa myös kirjallisen läpileikkauksen lisääviin valmistusteknologioihin sekä käyttökohteisiin. Käytännön työssä etsittiin lisäävien valmistusmenetelmien etuja hyödyntäviä konsepteja, prototypoitiin, sekä testattiin kehiteltyjä ratkaisuja suhteessa toimialan vaatimuksiin. Työn tuloksena valmistettiin ja testattiin toiminnallinen nappikonstruktio. Kokoonpanon osamäärää, materiaalinkäyttöä sekä hintaa saatiin vähennettyä suhteessa alkuperäiseen. Kaikkia vaatimuksia ei kuitenkaan saatu täytettyä. Prosessin aikana tunnistettiin tarve systemaattisemmalle materiaali- sekä valmistusprosessivalinnalle. Tästä huolimatta lisäävät valmistusmenetelmät todettiin vakavasti otettavaksi vaihtoehdoksi matalan volyymin muovituotteiden valmistuksessa

Variable fidelity modeling as applied to trajectory optimization for a hydraulic backhoe

Modeling, simulation, and optimization play vital roles throughout the engineering design process; however, in many design disciplines the cost of simulation is high, and designers are faced with a tradeoff between the number of alternatives that can be evaluated and the accuracy with which they can be evaluated. In this thesis, a methodology is presented for using models of various levels of fidelity during the optimization process. The intent is to use inexpensive, low-fidelity models with limited accuracy to recognize poor design alternatives and reserve the high-fidelity, accurate, but also expensive models only to characterize the best alternatives. Specifically, by setting a user-defined performance threshold, the optimizer can explore the design space using a low-fidelity model by default, and switch to a higher fidelity model only if the performance threshold is attained. In this manner, the high fidelity model is used only to discern the best solution from the set of good solutions, so that computational resources are conserved until the optimizer is close to the solution. This makes the optimization process more efficient without sacrificing the quality of the solution. The method is illustrated by optimizing the trajectory of a hydraulic backhoe. To characterize the robustness and efficiency of the method, a design space exploration is performed using both the low and high fidelity models, and the optimization problem is solved multiple times using the variable fidelity framework.M.S.Committee Chair: Paredis, Chris; Committee Member: Bras, Bert; Committee Member: Burkhart, Roger; Committee Member: Choi, Seung-Kyu

State-of-the-art: AI-assisted surrogate modeling and optimization for microwave filters

Microwave filters are indispensable passive devices for modern wireless communication systems. Nowadays, electromagnetic (EM) simulation-based design process is a norm for filter designs. Many EM-based design methodologies for microwave filter design have emerged in recent years to achieve efficiency, automation, and customizability. The majority of EM-based design methods exploit low-cost models (i.e., surrogates) in various forms, and artificial intelligence techniques assist the surrogate modeling and optimization processes. Focusing on surrogate-assisted microwave filter designs, this article first analyzes the characteristic of filter design based on different design objective functions. Then, the state-of-the-art filter design methodologies are reviewed, including surrogate modeling (machine learning) methods and advanced optimization algorithms. Three essential techniques in filter designs are included: 1) smart data sampling techniques; 2) advanced surrogate modeling techniques; and 3) advanced optimization methods and frameworks. To achieve success and stability, they have to be tailored or combined together to achieve the specific characteristics of the microwave filters. Finally, new emerging design applications and future trends in the filter design are discussed

Automated calculation of device sizes for digital IC designs

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.Includes bibliographical references.by Lennox P. John Hoyte.M.S

Utilizing digital design techniques and circuits to improve energy and design efficiency of analog and mixed-signal circuits

Technology scaling has long driven large growth in the electronics market. With each successive technology generation, digital circuits become more power and area efficient. The large performance increases realized for digital circuits due to digital scaling have not translated to similar performance improvements for analog circuits. First, noise-limited analog circuits are not capable of leveraging the reduced parasitics of advanced processes, since capacitor sizes are generally set by noise requirements. Second, analog circuit performance is closely tied to the achievable device intrinsic gain, which degrades as process sizes shrink. Reduced supply voltages further exacerbate this issue, as the achievable gain per stage is limited by the number of devices that can be stacked while maintaining all devices in saturation. Finally, process variation increases with decreased feature sizes, so analog circuits have deal with increased mismatch and wider variations in threshold voltages, increasing the time required to design a circuit that is robust across process, voltage, and temperature (PVT) variation. This work seeks to address the limitations of analog circuits in advanced technologies by leveraging digital techniques and digital-like circuits that offer improved scalability. The first half of this dissertation investigates replacing the traditional closed-loop residue amplifier in a pipeline analog-to-digital converter (ADC) with an open loop dynamic amplifier. Previous works incorporating dynamic amplifiers have struggled to achieve large gains and have suffered from offset mismatch between the comparator and amplifier, which will only get worse in more advanced technologies. We propose the usage of a residue amplifier that combines an integration stage, to ensure low noise operation, with a positive feedback stage, to ensure high gain and high speed operation. By utilizing this topology, the proposed amplifier was the first dynamic amplifier to achieve a high gain of 32. Additionally, the proposed amplifier can reuse existing comparator hardware in the ADC, removing all offset mismatch between comparator and amplifier. Digital calibration techniques were applied to ensure a constant gain across PVT. The next part of this dissertation tries to overcome the scaling challenges for noise-limited ADCs with band-limited input signals. By leveraging digital filtering techniques to generate a prediction of the band-limited signal, the conversion can be limited to a range that is a fraction of the total ADC input range, allowing for significant decreases in reference and comparator power consumption. This work extends previous works by enabling accurate predictions for any band-limited signal characteristic. Previous works only focused on accurate predictions for low-activity signals. Finally, the large compute power enabled by modern technology scaling is leveraged to improve the design efficiency of analog circuits. A new automated circuit sizing tool is proposed that can achieve better performance than manual designs done by experts in a much shorter amount of time. All of these techniques help to alleviate the power and design efficiency limitations caused by technology scaling.Electrical and Computer Engineerin

Programmable and Modular DC-DC Converter

This project considers the design, implementation, and testing of an open-source dc-dc converter for microgrid prototyping. Unlike conventional dc-dc converters that are proprietary and require specialist knowledge, and are usually designed for a single function, the proposed dc-dc converter will comprise of a programmable MCU and a Raspberry Pi (RPi) interface to allow less-skilled consumers to monitor and modify a power converting system. We will develop an open-source library that contains voltage control, current control, maximum power point tracking, and battery charge control profiles. Each library will be easy to implement through a GUI on the Raspberry Pi and will be controlled using an Atmega328 located on the power conversion unit. C++ and the Arduino IDE will be used for testing and will retain functionality in the finished project for more knowledgeable customers to edit the pre-set profiles. Moreover, the Pi will need to communicate with multiple converters and monitor their set points in applications where more than one dc-dc converter is necessary. The supporting hardware around the microcontrollers is a dc-dc converter, while the connection with the RPi and any external hardware will be open-source and custom designed to accommodate multiple converters on a single system. As a result, the integration of our dc-dc converter will provide a way to easily set up a microgrid system without the use of proprietary voltage converting hardware