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Institute Talks

Human Tactile Afferent Responses during the Onset of Slip

  • 28 January 2020 • 11:00—12:00
  • Benoit Delhaye
  • MPI-IS Stuttgart, Heisenbergstr. 3, Room 2P4

During manipulation, humans adjust the amount of force applied to an object depending on friction: they exert a stronger grip for slippery surfaces and a looser grip for sticky surfaces. However, the neural mechanisms signaling friction remain unclear. To fill this gap, we recorded the response of human tactile afferent during the onset of slip against flat surfaces of different frictions. We observed that some afferents responded to partial slip events occurring during transition from a stuck to a slipping contact, and potentially signaling the impending slip.

Organizers: Katherine J. Kuchenbecker Ilona Jacobi

  • Nataliya Rokhmanova
  • MPI-IS Stuttgart, Heisenbergstr. 3, Room 2P4

Wearable sensing and feedback devices are becoming increasingly ubiquitous for measuring human movement in research laboratories, medical clinics, and in consumer goods. Advances in computation and miniaturization have enabled sensing for gait assessment; these technologies are then used in interventions to provide feedback that facilitates changes in gait or enhances sensory capabilities. This talk will focus on vibration as the primary method of providing feedback. I will discuss the use of vibrotactile arrays to communicate plantar foot pressure in users of lower-limb prosthetics, as a synthetic form of sensory feedback. Wearable vibrating units can also be used as a cue to retrain gait, and I will describe my preliminary work in gait retraining as a conservative treatment for knee osteoarthritis. This talk will cover the development and evaluation of these haptic devices and establish their impact within the greater context of clinical biomechanics.

Organizers: Katherine J. Kuchenbecker Ilona Jacobi

Search-Based Planning for High-Dimensional Robotic Systems

  • 24 January 2020 • 11:00—12:00
  • Maxim Likhachev
  • MPI-IS Stuttgart, Heisenbergstr. 3, Room 2P4

Search-based Planning refers to planning by constructing a graph from systematic discretization of the state- and action-space of a robot and then employing a heuristic search to find an optimal path from the start to the goal vertex in this graph. This paradigm works well for low-dimensional robotic systems such as mobile robots and provides rigorous guarantees on solution quality. However, when it comes to planning for higher-dimensional robotic systems such as mobile manipulators, humanoids and ground and aerial vehicles navigating at high-speed, Search-based Planning has been typically thought of as infeasible. In this talk, I will describe some of the research that my group has done into changing this thinking. In particular, I will focus on two different principles. First, constructing multiple lower-dimensional abstractions of robotic systems, solutions to which can effectively guide the overall planning process using Multi-Heuristic A*, an algorithm recently developed by my group. Second, using offline pre-processing to provide a *provably* constant-time online planning for repetitive planning tasks. I will present algorithmic frameworks that utilize these principles, describe their theoretical properties, and demonstrate their applications to a wide range of physical high-dimensional robotic systems.

Organizers: Katherine J. Kuchenbecker Ilona Jacobi

Cyber security and privacy in networked control systems

  • 20 January 2020 • 14:00—15:00
  • Prof. Karl H. Johansson
  • MPI-IS Stuttgart, Heisenbergstr. 3, seminar room 2P4

Security and privacy is of growing concern in many control applications. Cyber attacks are frequently reported for a variety of industrial and infrastructure systems. For more than a decade the control community has developed techniques for how to design control systems resilient to cyber-physical attacks. In this talk, we will review some of these results. In particular, as cyber and physical components of networked control systems are tightly interconnected, it is be argued that traditional IT security focusing only on the cyber part does not provide appropriate solutions. Modeling the objectives and resources of the adversary together with the plant and control dynamics is shown to be essential. The consequences of common attack scenarios, such denial-of-service, replay, and bias injection attacks, can be analyzed using the presented framework. It is also shown how to strengthen the control loops by deriving security and privacy aware estimation and control schemes. Applications in building automation, power networks, and automotive systems will be used to motivate and illustrate the results. The presentation is based on joint work with several students and colleagues at KTH and elsewhere.

Organizers: Sebastian Trimpe Dominik Baumann

Kirigami-Inspired Metamaterials - from Morphable Structures to Soft Robots

IS Colloquium
  • 09 January 2020 • 16:00—17:00
  • Katia Bertoldi
  • Room 2P04 in Stuttgart and broadcast to room N0.002 in Tübingen

In the search for materials with new properties, there have been great advances in recent years aimed at the construction of mechanical systems whose behaviour is governed by structure, rather than composition. Through careful design of the material’s architecture, new material properties have been demonstrated, including negative Poisson’s ratio, high stiffness-to-weight ratio and mechanical cloaking. While originally the field focused on achieving unusual (zero or negative) values for familiar mechanical parameters, more recently it has been shown that non-linearities can be exploited to further extend the design space. In this talk Prof. Katia Bertoldi will focus on kirigami-inspired metamaterials, which are produced by introducing arrays of cuts into thin sheets. First, she will demonstrate that instabilities triggered under uniaxial tension can be exploited to create complex 3D patterns and even to guide the formation of permanent folds. Second, she will show that such non-linear systems can be used to designs smart and flexible skins with anisotropic frictional properties that enables a single soft actuator to propel itself. Finally, Prof.Bertoldi will focus on bistable kirigami metamaterials and show that they provide an ideal environment for the propagation non-linear waves.

Organizers: Metin Sitti

Dynamics of Decisions

IS Colloquium
  • 09 January 2020 • 10:00—11:00
  • Moritz Hardt
  • Room N0.002 in Tübingen and broadcast to room 2P04 in Stuttgart

Machine learning increasingly supports consequential decisions in domains including health, employment, and criminal justice. Consequential decision making is inherently dynamic: Individuals, their outcomes, and entire populations can change and adapt in response to classification. Traditional machine learning, however, fails to account for such dynamic effects. In this talk, I will highlight three different vignettes of dynamic decision making. The first is about how classification changes populations and how this perspective is essential to questions of fairness in machine learning. The second is about how classification incentivizes individuals to adapt strategically. The third is about how predictions are often performative, that is, they influence the very outcome they aim to predict. I will end on the contours of a theory that unifies these three settings and its connections to questions in causality, control theory, economics, and sociology.

Organizers: Metin Sitti

  • Dr. Ksenia Keplinger
  • 2P4

Recent economic, technological, and societal changes (e.g., the shift from large organizations to decentralized networks of individuals/small businesses, #metoo movement) require organizations to adapt to the transforming nature of work by altering the way work is performed and the roles that workers play. Due to globalization and advanced communication technologies, modern organizations are also characterized by a diverse workforce that needs to be carefully managed. Therefore organizational leaders must take on the challenge of unleashing the true potential of diversity and inclusion by challenging assumptions and changing corporate cultures. Using qualitative and quantitative methods, my research explores the implications of the ongoing transformation of work in terms of worker’s identity and their perspective on time and place, and looks into the main competencies workers need to successfully adapt to the new way of working. In addition, I examine how modern organizations can promote a diverse and inclusive workplace and how they deal with one the major barriers to the career development of professional women – sexual harassment in the workplace. Finally, I explore the role of leaders in creating a diverse and inclusive community. On a larger scale, my research aims to help leaders and organizations clarify how they can contribute to a more tolerant, diverse, and inclusive society.

Organizers: Katherine J. Kuchenbecker

  • Ye Zhao
  • MPI-IS Stuttgart, Heisenbergstr. 3, room 2P04

The demand for safe, robust, and intelligent robotic systems is growing rapidly, given their potential to make our societies more productive and increase our welfare. To achieve this, robots are increasingly expected to operate in human-populated environments, maneuver in remote and cluttered environments, maintain and repair facilities, take care of our health, and streamline manufacturing and assembly lines. However, computational issues limit the ability of robots to plan complex motions in constrained and contact-rich environments, interact with humans safely, and exploit dynamics to gracefully maneuver, manipulate, fly, or explore the oceans. This talk will be centered around planning and decision-making algorithms for robust and agile robots operating in complex environments. In particular, Dr. Zhao will present novel computational approaches necessary to enable real-time and robust motion planning of highly dynamic bipedal locomotion over rough terrain. This planning approach revolves around robust disturbance metrics, an optimal recovery controller, and foot placement re-planning strategies. Extending this motion planning approach to generalized whole-body locomotion behaviors, He will introduce our recent progress on high-level reactive task planner synthesis for multi-contact, template-based locomotion interacting with constrained environments and how to integrate formal methods for mission-capable locomotion. This talk will also present robust trajectory optimization algorithm capable of handling contact uncertainties and without enumerating contact modes. Dr. Zhao will end this talk with current research directions on distributed trajectory optimization and task and motion planning.

Organizers: Metin Sitti

  • Fernanda Bribiesca
  • 5H7 MPI-IS Stuttgart

Fernanda Bribiesca-Contreras' doctoral research investigates the form and function relationship of the wing muscles and its implication with aerial and underwater flight.

Organizers: Alexander Badri-Sprowitz

  • Dr. Katherine J. Kuchenbecker
  • MPI Campus in Tübingen - Lecture hall in the Max Planck House

Our scientific understanding of haptic interaction is still evolving, both because what you feel greatly depends on how you move, and because engineered sensors, actuators, and algorithms typically struggle to match human capabilities. Consequently, few computer and machine interfaces provide the human operator with high-fidelity touch feedback or carefully analyze the physical signals generated during haptic interactions, limiting their usability. The crucial role of the sense of touch is also deeply appreciated by researchers working to create autonomous robots that can competently manipulate everyday objects and safely interact with humans in unstructured environments.