Given a swarm of limited-capability robots, we seek to automatically discover the set of possible emergent behaviors. Prior approaches to behavior discovery rely on human feedback or hand-crafted behavior metrics to represent and evolve behaviors and only discover behaviors in simulation, without testing or considering the deployment of these new behaviors on real robot swarms. In this work, we present Real2Sim2Real Behavior Discovery via Self-Supervised Representation Learning, which combines representation learning and novelty search to discover possible emergent behaviors automatically in simulation and enable direct controller transfer to real robots. First, we evaluate our method in simulation and show that our proposed self-supervised representation learning approach outperforms previous hand-crafted metrics by more accurately representing the space of possible emergent behaviors. Then, we address the reality gap by incorporating recent work in sim2real transfer for swarms into our lightweight simulator design, enabling direct robot deployment of all behaviors discovered in simulation on an open-source and low-cost robot platform. 

Electroaerodynamic propulsion, where force is produced via the momentum-transferring collisions between accelerated ions and neutral air molecules, is a promising alternative mechanism for flight at the micro air vehicle scale due to its silent and solid-state nature. Its relatively low efficiency, however, has thus far precluded its use in a power-autonomous vehicle; leveraging the efficiency benefits of operation close to a fixed surface is a potential solution. While proximity effects like the ground and ceiling effects have been well-investigated for rotorcraft and flapping wing micro air vehicles, they have not been for electroaerodynamically-propelled fliers. In this work, we investigate the change in performance when centimeter-scale thrusters are operated close to a "ceiling" plane about the inlet. We show a surprising and, until now, unreported effect; a major electrostatic attractive component, analogous to electroadhesive pressure but instead mediated by a stable atmospheric plasma. The isolated electrostatic and fluid dynamic components of the ceiling effect are shown for different distances from the plane and for different materials. We further show that a flange attached to the inlet can vastly increase both components of force. A peak efficiency improvement of 600% is shown close to the ceiling. This work points the way towards effective use of the ceiling effect for power autonomous vehicles, extending flight duration, or as a perching mechanism. 

In modern Electrical Engineering degree programs, MATLAB is often one of the first coding experiences a student is exposed to. Most introductory robotics courses that combine hardware and software require students to understand C (typically learned during junior year) or require part of the course to teach coding syntax. In order to introduce robotics and cyber-physical systems earlier in the curriculum, we have developed an interface to allow students to remotely control a wireless microcontroller (e.g., Arduino MKR 1010) using MATLAB. This interface comprises two halves: 1) a MATLAB class that abstracts UDP commands transmitted over WiFi, and 2) a custom C++ library for receiving, parsing, and responding to commands over UDP, as well as streaming data back to the client. The interface leverages students’ existing knowledge of MATLAB and bypasses the need for C programming, allowing students to get early exposure to hardware-software integration, signal processing, edge computing, end-to-end platform development, and systems engineering. Our interface facilitates data observation, recording, manipulation, and analysis. Students have access to live data streams, real-time plots of sensor values, and the ability to use the command window to run and test individual commands outside of scripts. We deployed this system in an introductory class where students perform various mechatronic lab exercises and complete a final project where their robot navigates a maze then collects and classifies objects using sensor data and neural networks. We surveyed two semesters of students at the end of the course, and students reported that using this interface enhanced their learning experience despite varied responses about the difficulty of implementation. With the growing importance of data science in electrical engineering, tools like our interface play a crucial role in exposing students to cutting-edge robotics and cyber-physical systems earlier in the degree program. Our interface has been made available on GitHub for any who wishes to implement it.

Electroaerodynamic (EAD) propulsion, where thrust is produced by collisions between electrostatically-accelerated ions and neutral air, is a potentially transformative method for indoor flight owing to its silent and solid-state nature. Like rotors, EAD thrusters exhibit changes in performance based on proximity to surfaces. Unlike rotors, they have no fragile and quickly spinning parts that have to avoid those surfaces; taking advantage of the efficiency benefits from proximity effects may be a route towards longer-duration indoor operation of ion-propelled fliers. This work presents the first empirical study of ground proximity effects for EAD propulsors, both individually and as quad-thruster arrays. It focuses on multi-stage ducted centimeter-scale actuators suitable for use on small robots envisioned for deployment in human-proximal and indoor environments. Three specific effects (ground, suckdown, and fountain lift), each occurring with a different magnitude at a different spacing from the ground plane, are investigated and shown to have strong dependencies on geometric parameters including thruster-to-thruster spacing, thruster protrusion from the fuselage, and inclusion of flanges or strakes. Peak thrust enhancement ranging from 300 to 600% is found for certain configurations operated in close proximity (0.2 mm) to the ground plane and as much as a 20% increase is measured even when operated centimeters away.

Electroaerodynamic propulsion, where force is produced through collisions between electrostatically accelerated ions and neutral air molecules, is an attractive alternative to propellerand flapping wing-based methods for micro air vehicle (MAV) flight due to its silent and solid-state nature. One major barrier to adoption is its limited thrust efficiency at useful disk loading levels. Ducted actuators comprising multiple serially-integrated acceleration stages are a potential solution, allowing individual stages to operate at higher efficiency while maintaining a useful total thrust, and potentially improving efficiency through various aerodynamic and fluid dynamic mechanisms. Here, we investigate the effects of duct and emitter electrode geometries on actuator performance, then show how a combination of increasing cross-sectional aspect ratio and serial integration of multiple stages can be used to produce overall thrusts comparable to state-of-the-art flapping wing robots. A five-stage device is shown to reach a thrust density of about 18 N/m2, an order of magnitude higher than what has previously been achieved at this scale, with the same measured thrust efficiency as reported in prior work. We also show how a high aspect ratio multi-stage ducted thruster could be integrated under the wings of a MAV-scale platform, pointing towards use as a distributed propulsion system in future work.

Microsurgery, wherein surgeons operate on extremely small structures frequently visualized under a microscope, is a particularly impactful yet challenging form of surgery. Robot assisted microsurgery has the potential to improve surgical dexterity and enable precise operation on such small scales in ways not previously possible. Clinical applications of microsurgery include intraocular surgery, fetal surgery, otology, laryngeal surgery, neurosurgery, and urology. Intraocular microsurgery is a particularly challenging domain. Challenges arise, in part, due to the lack of dexterity that is achievable with rigid instruments inserted through the eye. The insertion point introduces a remote center of motion constraint that prevents control over a tool-tip’s full position and orientation for conventional, straight instruments. Continuum robots based on concentric tubes, magnetic actuation, and tendon-actuated stacked disks have been proposed for intraocular microsurgery to overcome this constraint, but are frequently limited in their local curvatures—an important consideration in constrained spaces. Inspired by these works, and to take steps toward overcoming limited local curvature, we present a new design for a millimeter-scale, dexterous tendon-driven continuum wrist and gripper, intended for microsurgery applications. The device is created via a state-of-the-art two-photon-polymerization (2PP) microfabrication technique. The 2PP 3D printing method enables construction via a flexible material, with complex internal geometries and critical features at the micron-scale (Fig. 1). The wrist is composed of a stacked rhombus shape, first proposed at macro scale by Childs et. al. This design introduces torsional rigidity as a byproduct of its geometry. We leverage this design not for its torsional rigidity (although we envision that will aid modeling in future work), but rather due to the fact that the extruded nature of its geometry lends itself to 2PP sub-millimeter scale 3D printing. Building on this concept, we miniaturise the design and integrate a flexible gripper. The wrist has three tendons routed down its length, spaced approximately evenly around its circumference which, when actuated by small-scale linear actuators, enable bending in any plane. The gripper is actuated by a fourth tendon routed down the center of the wrist. We characterize the wrist’s bend-angle, achieving >90° bend in both axes. We demonstrate out-of-plane bending as well as the ability to grip while actuated. Our integrated tendon-driven continuum wrist/gripper design and meso-scale assembly techniques have the potential to enable small-scale robots with more dexterity than has been previously demonstrated. Such a wrist could improve surgeon capabilities during teleoperation with the potential to improve patient outcomes in a variety of surgical applications, including intraocular surgery.

Decentralized control in multi-robot systems is dependent on accurate and reliable communication between agents. Important communication factors, such as latency and packet delivery ratio, are strong functions of the number of agents in the network. Findings from studies of mobile and high node-count radio-frequency (RF) mesh networks have only been transferred to the domain of multi-robot systems to a limited extent, and typical multi-agent robotic simulators often depend on simple propagation models that do not reflect the behavior of realistic RF networks. In this paper, we present a new open source swarm robotics simulator, BotNet, with an embedded standards-compliant time-synchronized channel hopping (6TiSCH) RF mesh network simulator. Using this simulator we show how more accurate communications models can limit even simple multi-robot control tasks such as flocking and formation control, with agent counts ranging from 10 up to 2500 agents. The experimental results are used to motivate changes to the inter-robot communication propagation models and other networking components currently used in practice in order to bridge the sim-to-real gap.

The electrohydrodynamic (EHD) force produced by ions ejected from a corona plasma is a solid state, silent mechanism for accelerating air, useful for applications ranging from electronics cooling to flying microrobots. This paper presents the theoretical motivation and the first implementation of a multi-stage, highly miniaturized EHD device, which can provide both improved absolute power output and power density as compared to single-stage devices. A laser microfabricated, folded electrode design reduces component count and assembly time. Data from one, two, and three-stage devices demonstrates a near linear scaling of output force with stage count, indicating inter-stage ducting successfully reduces losses. Device lifetime is assessed to validate the use of stainless-steel emission electrodes. Areal thrust, force density, and volumetric power density for the three-stage device are among the highest ever measured from an EHD actuator.

Purpose of Review

The goal of this review is to evaluate the current status of multi-robot systems in the context of search and rescue. This includes an investigation of their current use in the field, what major technical challenge areas currently preclude more widespread use, and which key topics will drive future development and adoption.

Recent Findings

Work blending machine learning with classical control techniques is driving progress in perception-driven autonomy, decentralized multi-robot coordination, and human–robot interaction, among others. Ad hoc mesh networking has achieved reliability suitable for safety-critical applications and may be a partial solution for communication. New modular and multimodal platforms may overcome mobility limitations without significantly increasing cost.

Summary

Multi-agent systems are not currently ready for deployment in search and rescue applications; however, progress is being made in a number of critical domains. As the field matures, research should focus on realistic evaluations of constituent technologies, and on confronting the challenges of simulation-to-reality transfer, algorithmic bias in autonomous agents that rely on machine learning, and novelty-versus-reliability incentive mismatch

Modular soft robots combine the strengths of two traditionally separate areas of robotics. As modular robots, they can show robustness to individual failure and reconfigurability; as soft robots, they can deform and undergo large shape changes in order to adapt to their environment, and have inherent human safety. However, for sensing and communication these robots also combine the challenges of both: they require solutions that are scalable (low cost and complexity) and efficient (low power) to enable collectives of large numbers of robots, and these solutions must also be able to interface with the high extension ratio elastic bodies of soft robots. In this work, we seek to address these challenges using acoustic signals produced by piezoelectric surface transducers that are cheap, simple, and low power, and that not only integrate with but also leverage the elastic robot skins for signal transmission. Importantly, to further increase scalability, the transducers exhibit multi-functionality made possible by a relatively flat frequency response across the audible and ultrasonic ranges. With minimal hardware, they enable directional contact-based communication, audible-range communication at a distance, and exteroceptive sensing. We demonstrate a subset of the decentralized collective behaviors that these functions make possible with multi-robot hardware implementations. The use of acoustic waves in this domain is shown to provide distinct advantages over existing solutions.

A swarm of robots can accomplish more than the sum of its parts, and swarm systems will soon see increased use in applications ranging from tangible interfaces to search and rescue teams. However, effective human control of robot swarms has been shown to be demonstrably more diffcult than controlling a single robot, and swarm-specifc interactions methodologies are relatively underexplored. As we envision even non-expert users will have more daily in-person encounters with different numbers of robots in the future, we present a user-defned set of control interactions for tabletop swarm robots derived from an elicitation study. We investigated the effects of number of robots and proximity on the user’s interaction and found signifcant effects. For instance, participants varied between using 1-2 fngers, one hand, and both hands depending on the group size. We also provide general design guidelines such as preferred interaction modality, common strategies, and a high-agreement interaction set.

The limited in-flight battery lifetime of centimeterscale flying robots is a major barrier to their deployment, especially in applications which take advantage of their ability to reach high vantage points. Perching, where flyers remain fixed in space without use of flight actuators by attachment to a surface, is a potential mechanism to overcome this barrier. Electroadhesion, a phenomenon where an electrostatic force normal to a surface is generated by induced charge, has been shown to be an increasingly viable perching mechanism as robot size decreases due to the increased surface-area-to-volume ratio. Typically electroadhesion requires high (> 1 kV) voltages to generate useful forces, leading to relatively large power supplies that cannot be carried on-board a micro air vehicle. In this paper, we motivate the need for application-specific power electronics solutions for electroadhesive perching, develop a useful figure of merit (the “specific voltage”) for comparing and guiding efforts, and walk through the design methodology of a system implementation. We conclude by showing that this high voltage power supply enables, for the first time in the literature, tetherless electroadhesive perching of a commercial micro quadrotor.

Nonholonomic control is a candidate to control nonlinear systems with path-dependant states. We investigate an underactuated flying micro-aerial-vehicle, the ionocraft, that requires nonholonomic control in the yaw-direction for complete attitude control. Deploying an analytical control law involves substantial engineering design and is sensitive to inaccuracy in the system model. With specific assumptions on assembly and system dynamics, we derive a Lie bracket for yaw control of the ionocraft. As a comparison to the significant engineering effort required for an analytic control law, we implement a data-driven model-based reinforcement learning yaw controller in a simulated flight task. We demonstrate that a simple model-based reinforcement learning framework can match the derived Lie bracket control – in yaw rate and chosen actions – in a few minutes of flight data, without a pre-defined dynamics function. This paper shows that learning-based approaches are useful as a tool for synthesis of nonlinear control laws previously only addressable through expert-based design. 

Designing effective low-level robot controllers often entail platform-specific implementations that require manual heuristic parameter tuning, significant system knowledge, or long design times. With the rising number of robotic and mechatronic systems deployed across areas ranging from industrial automation to intelligent toys, the need for a general approach to generating low-level controllers is increasing. To address the challenge of rapidly generating low-level controllers, we argue for using model-based reinforcement learning (MBRL) trained on relatively small amounts of automatically generated (i.e., without system simulation) data. In this paper, we explore the capabilities of MBRL on a Crazyflie centimeter-scale quadrotor with rapid dynamics to predict and control at ≤ 50Hz. To our knowledge, this is the first use of MBRL for controlled hover of a quadrotor using only on-board sensors, direct motor input signals, and no initial dynamics knowledge. Our controller leverages rapid simulation of a neural network forward dynamics model on a GPU-enabled base station, which then transmits the best current action to the quadrotor firmware via radio. In our experiments, the quadrotor achieved hovering capability of up to 6 seconds with 3 minutes of experimental training data.

The Micro Inertial Measurement System (MIMSY) is an open-source wireless sensor node for Internet of Things applications, specifically designed for a small system volume while maintaining functionality and extensibility. MIMSY is a 16mm × 16mm node with an Arm Cortex-M3 microprocessor, 802.15.4 wireless transceiver, and a 9-axis IMU. The system is fully compatible with the OpenWSN wireless sensor networking stack, which enables the straightforward implementation of standards-compliant 6TiSCH mesh networks using MIMSY motes. While the application space of MIMSY is quite vast, we present three sample implementations showcasing the opportunities afforded by a small and relatively low-cost mote with mesh networking and inertial measurement capabilities, including: high granularity areal sensing for sleep monitoring with motes embedded in a foam mattress; high reliability, low latency communication for industrial process automation and control; and long lifetime physical event detection and activity monitoring with minimal setup time.

Microwire and microelectrode arrays used for cortical neural recording typically consist of tens to hundreds of recording sites, but often only a fraction of these sites is in close enough proximity to firing neurons to record single-unit activity. Recent work has demonstrated precise, depth-controllable mechanisms for the insertion of single neural recording electrodes, but these methods are mostly only capable of inserting electrodes which elicit adverse biological response. We present an electrostatic-based actuator capable of inserting individual carbon fiber microelectrodes which elicit minimal to no adverse biological response. The device is shown to insert a carbon fiber recording electrode into an agar brain phantom and can record an artificial neural signal in saline. This technique provides a platform generalizable to any microwire-style recording electrode.

Enabling a future full of insect-scale robots will require progress on a huge number of fronts, one of which is the development of mobility platforms designed to operate beyond the scaling frontier of commercially available solutions. The vast majority of researchers seeking to create functional centimeter-scale flying robots have turned towards biomimetic propulsion mechanisms, specifically flapping wings. In this work I take a very different tack, investigating a propulsion mechanism with no natural analogue — electrohydrodynamic thrust. Electrohydrodynamics (EHD), specifically in the context of corona discharge based systems, has been a long studied and, until relatively recently, often poorly understood phenomenon. The beginning of this dissertation focuses on the theoretical underpinnings of the thrust mechanism. The bulk of my work has focused on developing proof of concept demonstrators for EHD at the meso-scale. Starting with rapidly prototyped materials and quickly moving to microfabricated electrodes, a series of prototypes elucidate the potential for EHD to yield high thrust-to-weight ratio fliers. Initial demonstrations have been backed up by more rigorous investigations of electrode geometric and density effects. Quadrotor systems begin to suffer from decreased performance at and below the centimeter scale, especially with regards to increasing demands on durability of rotory components (which may not exist at scale), efficiency of available DC motors, and propeller figures of merit. Simply replacing the rotors with EHD thrusters, however, allows us to sidestep some of the unfavorable scaling laws of propeller-based propulsion while maintaining the ability to transfer domain knowledge from the rich world of quadcopter design and control. Demonstrating repeatable takeoff and rudimentary (open-loop) attitude control is trivial with external power supplied to the simple quad-thruster design. Through a combination of design and methodology (e.g., with regards to assembly) improvements, functional EHD-based “ionocraft” can now be built in about half an hour, with near 100% success rate. Controlled flight is now within reach. Merely hovering with tethered power and an off-board controller is only the beginning. The final sections of this work outline a variety of paths forward, towards better performance of a meso-scale ionocraft, autonomous operation, and further miniaturization. Ultimately, I believe the future is bright for ionocraft. While electrohydrodynamics may not be the most power efficient mechanism, nor the easiest to grasp conceptually, it is certainly the simplest to design; put two asymmetric electrodes close to eachother, apply a high voltage, and away it goes! In the words of a respected professor, how hard could it be?

This paper demonstrates the first flying microrobot using electrohydrodynamic thrusters, or ionocraft, to successfully take off while carrying an onboard commercial sensor package. The 13.6mg, 1.8cm by 1.8cm ionocraft is shown to take off while carrying a 40mg Flex PCB with 9-axis IMU and associated passives while tethered to a power supply. A new emitter electrode design has decreased corona onset voltage by over 30% and takeoff voltage by over 20% from previous efforts. Thrust density scaling with increasing numbers of emitter wires, continued geometric scaling for decreased operating voltage, device lifetime improvement via thin film deposition, and new assembly techniques are all explored.

The rise in prevalence of Internet of Things (IoT) technologies has encouraged more people to prototype and build custom internet connected devices based on low power microcontrollers. While well-developed tools exist for debugging network communication for desktop and web applications, it can be difficult for developers of networked embedded systems to figure out why their network code is failing due to the limited output affordances of embedded devices. This paper presents WiFröst, a new approach for debugging these systems using instrumentation that spans from the device itself, to its communication API, to the wireless router and back-end server. WiFröst automatically collects this data, displays it in a web-based visualization, and highlights likely issues with an extensible suite of checks based on analysis of recorded execution traces.

This work presents an insect-scale microrobot that flies silently and with no mechanical moving parts, using a mechanism with no analogue in the natural world: electrohydrodynamic thrust produced by ions generated via corona discharge. For the first time, attitude and acceleration data is continuously collected from takeoff and sustained flight of a 2cm x 2cm, 30mg “ionocraft” carrying a 37mg 9-axis commercial IMU on FlexPCB payload, with external tethers for power and data transfer. The ionocraft’s steady state thrust versus voltage profile, dynamic response to a time-varying signal around a high voltage DC bias point, and aerodynamic drag at incident angles around 90 degrees are measured. These experimental measurements, as well as measured IMU sensor noise, are inserted into a Matlab Simulink simulation environment. Simulation shows controlled hovering and planned flight in arbitrary straight trajectories in the X-Y plane. 

The Maker movement has encouraged more people to start working with electronics and embedded processors. A key challenge in developing and debugging custom embedded systems is understanding their behavior, particularly at the boundary between hardware and software. Existing tools such as step debuggers and logic analyzers only focus on software or hardware, respectively. This paper presents a new development environment designed to illuminate the boundary between embedded code and circuits. Bifröst automatically instruments and captures the progress of the user’s code, variable values, and the electrical and bus activity occurring at the interface between the processor and the circuit it operates in. This data is displayed in a linked visualization that allows navigation through time and program execution, enabling comparisons between variables in code and signals in circuits. Automatic checks can detect low-level hardware configuration and protocol issues, while user-authored checks can test particular application semantics. In an exploratory study with ten participants, we investigated how Bifröst influences debugging workflows.

The preponderance of research into flying microrobots has focused on biomimetic flight mechanisms. In this work, we demonstrate an insect-scale robot capable of vertical takeoff using electrohydrodynamic thrust, a mechanism with no natural analogue. The 10mg, 1.8cm by 1.8cm “ionocraft” operates at about 2400 volts and has a thrust to weight ratio of approximately 10. Feasibility of using individually addressable thrusters in a quadcoptor-esque manner for attitude control is demonstrated qualitatively. A combination of design choices in the microfabricated silicon electrodes and a machine-fabricated external fixture allow for reproducible hand-assembly of the microrobot. 

This work presents the locomotion of a ground-based single-legged silicon robot. The robot measures 5mm x 6mm x 0.5mm and weighs 18mg. Fabricated in a silicon-on-insulator (SOI) process, the robot is based on electrostatic inchworm motors that drive a 2 degree-of-freedom (DOF) planar silicon linkage that acts as the leg. The leg sweeps out an area of approximately 500μm x 500μm off the edge of the chip. The chip is connected to power and control by long flexible wires which also act to support the robot upright. The robot exerts over 1.5x its weight in the vertical axis, enough to lift its body and push itself forward. 

Taken together, recent advances in microelectromechanical systems, wireless mesh networks, digital circuits, and battery technology have made the notion of autonomous pico air vehicles viable. In this work we describe the core technologies enabling these future vehicles as well as propose two possible future platforms. We draw on recent research on high thrust density atmospheric ion thrusters, microfabricated silicon control surfaces, and extremely low mass and power mesh networking nodes. Using the same open-source network implementation as we have already demonstrated in larger UAVs, these flying microrobots will open up a new application space where unobtrusiveness and high data granularity are vital. 

Electrohydrodynamic thrust is an emerging propulsion mechanism for flying insect-scale robots. There is a need to both minimize the operating voltage and maximize the output force when designing microfabricated electrodes for use in these robots. In this work, an array of hybrid wire-needle and grid electrode geometries were fabricated and characterized to attempt to minimize both corona discharge onset voltage and thrust loss factor. Statistical analysis of this dataset was performed to screen for factors with significant effects. An optimized emitter electrode decreased onset voltage by 22%. Loss factor was found to vary significantly (as much as 30%) based on collector grid geometric parameters without affecting discharge characteristics. The results from this study can be used to drive further optimization of thrusters, with the final goal of providing a path towards autonomous flying microrobots powered by atmospheric ion engines. 

The bulk of current research in the realm of pico air vehicles has focused on biologically inspired propulsion mechanisms. In this work we investigate the use of electrohydrodynamic thrust produced by a microfabricated corona discharge device as a mechanism to create flying microrobots with no moving parts. Electrodes of various geometries are fabricated from a silicon-on-insulator wafer with a two mask process. Electrical characterization is performed to analyze the effect of inter-electrode gap and emitter electrode width on corona discharge and compare findings to simulation. Outlet air velocity and thrust are directly measured to analyze the effects of collector electrode geometry on performance. A roughly 100 cubic millimeter, 2.5mg thruster is assembled with a thrust to weight ratio exceeding 20.

The recent proliferation of easy to use electronic components and toolkits has introduced a large number of novices to designing and building electronic projects. Nevertheless, debugging circuits remains a difficult and time-consuming task. This paper presents a novel debugging tool for electronic design projects, the Toastboard, that aims to reduce debugging time by improving upon the standard paradigm of point-wise circuit measurements. Ubiquitous instrumentation allows for immediate visualization of an entire breadboard’s state, meaning users can diagnose problems based on a wealth of data instead of having to form a single hypothesis and plan before taking a measurement. Basic connectivity information is displayed visually on the circuit itself and quantitative data is displayed on the accompanying web interface. Software-based testing functions further lower the expertise threshold for efficient debugging by diagnosing classes of circuit errors automatically. In an informal study, participants found the detailed, pervasive, and context-rich data from our tool helpful and potentially time-saving.