Advanced Locomotion Control of Exoskeleton Systems: The Role of Active and Passive Compliance
by Barkan Uğurlu
(Özyeğin University, Department of Mechanical Engineering)
DATE : October 26, 2018 (Friday)
TIME : 14:00-15:00

The exoskeleton market is exponentially growing as its market size is estimated to surpass 3.4 billion USD by 2024. Likewise, R&D activities for wearable robots and exoskeletons show a significant increase. These systems are increasingly playing an important role in robot-aided walking support, elderly care, and SCI rehabilitation. Since these systems are in physical contact with humans, adjustable physical compliance, transparency and high fidelity control techniques are of importance to shape the next-gen exoskeletons of tomorrow. With this view in mind, the first segment of my talk will succinctly address my earlier research regarding the legged locomotion control of humanoids and quadrupeds.  In the second segment of my talk, I will share my hands-on experiences on two different exoskeleton systems: i) TTI-Exo, a whole body exoskeleton built in Toyota Technological Institute, Japan, ii) XoR, the first self-balancing lower limb exoskeleton with adjustable physical compliance and active disturbance rejection capability, built at the Dept. of Brain-Robot Interface, CNS-ATR, Japan. I will emphasize how the prior hands-on experience on legged locomotion enabled me to create exoskeleton systems that have distinguishable characteristics from the others. The third segment of my talk will disclose my vision concerning the next-generation exoskeleton robots and a roadmap to realistically develop such systems.
Short Biography:

Barkan Ugurlu received his Ph.D. degree in Electrical and Computer Engineering from Yokohama National University, Yokohama, Japan, in March 2010. From May 2010 to March 2013, he was a Post-Doctoral Researcher, at the Istituto Italiano di Tecnologia, Genova, Italy, and Toyota Technological Institute, Nagoya, Japan. Between March 2013 and February 2015, he was a Research Scientist at the Computational Neuroscience Laboratories, Advanced Telecommunications Research Institute International (ATR), Kyoto, Japan. He currently holds an Asst. Prof. position at the Dept. of Mechanical Engineering, Ozyegin University, Istanbul, Turkey. His research interests include active orthoses and exoskeletons, robot-aided rehabilitation, humanoid/quadruped locomotion control, and human-centered manipulation. He is a Marie Skłodowska-Curie Fellow.

Autonomous Mobile Vehicles and String Stability of Interconnected Vehicles
by Sinan Öncü
(Ford Otosan, Istanbul Sancaktepe R&D Center)
DATE : October 19, 2018 (Friday)
TIME : 14:00-15:00
Part 1-Overview of Past Research Projects on Autonomous Mobile Vehicles

In this introductory part of the presentation, an overview of past research experiences on autonomous mobile vehicle platforms will be presented with some example applications within the field of automotive and robotics. Some design considerations such as sensor and actuator selections besides the different modelling and control approaches for the realizations will be discussed on the following automated vehicle platforms:
- Autonomous Parallel Parking of a Car-Like Mobile Robot,
- Yaw Stability Control of a Car with Active Steering,
- A Man-portable Rover Operating on Rough Terrains,
- Cooperative Automated Maneuvering Vehicles,
- EcoTwin: Truck Platooning on Highways,
- Clara: A Warehouse Robot with Robust Multi-Sensor Localization,
- Wasteshark: An Aqua-Drone for Cleaning Plastic Waste from the Harbors and Rivers.
Part 2-String Stability of Interconnected Vehicles: Network-aware Modelling, Analysis and Experiments

The ever-increasing demand for mobility in today’s life brings additional burden on the existing ground transportation and logistic infrastructure, for which a feasible solution in the near future lies in more efficient use of currently available means of transportation. For this purpose, development of Cooperative Intelligent Transportation Systems (C-ITS) technologies that contribute to improved traffic flow stability, throughput, and safety is needed. Cooperative Automated Vehicles (CAVs) being one of the promising C-ITS technologies, extends the currently available Advanced Driver Assistance Systems technologies with the addition of information exchange between vehicles through Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) wireless communication.A particularly interesting application is the vehicle platooning concept. The general objective of vehicular platooning is to pack the driving vehicles together as tightly as possible in order to increase traffic throughput while preventing amplification of disturbances throughout the string, the latter of which is known as string instability. This technology relies on longitudinal control known as Cooperative Adaptive Cruise Control (CACC). In the scope of CACC, control over a wireless communication network is the enabling technology that makes this realizable; however, given the fact that multiple nodes (vehicles) share the same medium with a limited bandwidth and capacity, wireless communication introduces network-induced imperfections such as transmission delays and packet losses. The impact of these imperfections on string stability requires a careful analysis and tradeoffs between control performance and network specifications need to be made for achieving desired performance under these network-induced constraints. Therefore, in this study we present the design of a CACC system from a Networked Control System (NCS) perspective and a novel modelling framework is introduced. This modelling framework is extended with analysis tools for string stability in the presence of network effects. These analyses can provide the designer with guidelines for making multidisciplinary design tradeoffs between control and network specifications and support the design of CACC systems that are robust to uncertainties introduced by wireless communication. Moreover, the validity of the presented analysis framework is demonstrated via experimental results performed with CACC-equipped prototype vehicles. Experimental results show that the developed NCS modelling framework captures the dependency of string stability on network-induced effects and confirm the string stable operation conditions obtained by model-based analyses.
Short Bio:

Sinan Öncü received the B.Sc. degree in electronics and telecommunications engineering and the M.Sc. degree in mechatronics engineering from Istanbul Technical University, Istanbul, Turkey, in 2005 and 2008, respectively, and the Ph.D. degree in mechanical engineering from the Eindhoven University of Technology, Eindhoven, The Netherlands, in 2014. From 2013 to 2016, he was affiliated with the Netherlands Organization for Applied Scientific Research (TNO), The Netherlands, where he worked as a research scientist on the realization of cooperative automated vehicle technologies and their demonstrations with prototype vehicles to governmental institutes, industrial partners, and stakeholders; amongst which are most notably: the first automated driving demo in the Netherlands on public roads in 2013, and The European Truck Platooning Challenge in 2016. Since December 2017, he works as a Senior Software Engineer at Ford Otosan in Istanbul Sancaktepe R&D Center and leads the Horizon2020 project “Optimal fuel consumption with Predictive Power Train Control and calibration for intelligent trucks” (optiTruck). His current research focuses on the development of optimization-based predictive power management control systems for heavy duty trucks. Besides his professional research activities, he is enthusiastic about motorcycles and their dynamics. He combines this interest with travelling, camping, and photography. He enjoys going on long trips with his self-instrumented motorcycle and collects road data for his hobby project on developing an advisory system for safety improvement for motorcyclists.

Bio-resorbable sensors and MEMS energy harvesters for next-generation    transient and self-powered implants
by Levent Beker
(Stanford University, Department of Chemical Engineering)
DATE : March 28, 2018 (Wednesday)
TIME : 13:00-14:00
PDF version


Implantable medical devices and the concept of integrating  sensors/electronics into the human body have been intriguing curiosities especially in medicine for many decades. Recent developments in microfabrication and materials science finally have enabled development of sub-mm-sized implants for monitoring of critical parameters such as blood
pressure for heart arrhythmia, pH for GI tract complications, and neural activity for prosthetic applications. However, such devices have energy related problems so that patients need to go through a risky surgery for battery replacement periodically. This talk will cover potential approaches to eliminate this problem and realize next-generation transient/self-powered implants by utilizing bio-resorbable materials or energy harvesting microsystems.

In the first part of the seminar, a bio-resorbable and battery-free implant for wireless artery pulse monitoring will be presented. Design and fabrication of the proposed implant will be detailed by emphasizing particular diseases and surgical operations that require short-term vascular monitoring. Then, the focus will be on energy harvesting implants
which can generate electrical energy within the human body for long-term implants. Widely used neural and cochlear implants increase the quality of life of patients considerably by giving them the ability to move freely and hear. However, because of their power requirement, neural implant users must undergo surgery every 2-3 years just for battery replacement, and cochlear implant users need to change battery at least twice a day. Implantable    micro-electromechanical systems (MEMS) energy harvesters can help to reduce or eliminate the battery replacement problem. In the second part of the seminar, harvesting cerebrospinal fluid (CSF) flow pressure fluctuations within lateral ventricles of the brain using an  aluminum nitride-based piezoelectric-MEMS harvester will be detailed. Concentric ring-boss
diaphragm type harvester design will be introduced, and fabrication and characterization results will be presented. In addition to the MEMS-based harvester, studies on a PVDF-based flexible energy harvester array will also be presented. Then, in the final part, converting eardrum vibrations to electrical signals to stimulate auditory nerves inside cochlea using a PZT/Si cantilever-type resonant harvester to realize a self-powered cochlear implant will be discussed briefly.

Short Bio:

Levent Beker received B.Sc. and M.Sc. degrees in Mechanical Engineering and Micro/Nanotechnology from Middle East Technical University in 2010 and 2013, respectively. During his master’s he worked on fully-implantable cochlear implants. Then, he obtained his Ph.D. in Mechanical Engineering from University of California, Berkeley in 2017 where he worked on energy harvesting from cerebrospinal fluid (CSF) flow inside the brain and pressure sensors for harsh environment applications. He is currently a post-doctoral    research fellow working with Professor Zhenan Bao in Chemical Engineering at Stanford University. His current research focuses on bio-resorbable wireless implants, flexible/stretchable sensors for electronic-skin applications. He received Postdocs at the Interface award from Stanford University, Howard Hughes Medical Institute (HHMI) International Researcher Fellowship, Best poster award at Berkeley Sensor Actuator Center’s Industry Advisory Board Conference, Outstanding presentation award at Transducers 2013 Barcelona, and Best Thesis award from Middle East Technical University.

Non-Schmid slip behavior in shape memory alloys
by Sertan Alkan
(University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering)
DATE : November 17, 2017 (Friday)
TIME : 13:00-14:00
PDF Version
The plastic deformation mechanisms degrading the functional properties of ordered shape memory alloys will be discussed. In particular, tension-compression slip asymmetries and anisotropic glide resistances will be interrogated on both experimental and theoretical grounds for NiTi alloy. The interplay between the atomistic scale dislocation core displacements and the applied stress tensor components will be demonstrated to play a decisive role in the deviations from the critical resolved shear stress rule, also known as non-Schmid effects.  
The theoretical predictions will be compared with the experimental glide resistance measurements on single crystals within the framework of high magnification in-situ Digital Image Correlation (DIC) technique. Physical insights from the electronic structure will be provided to build a comprehensive understanding on the underlying mechanisms for non-Schmid behavior. The theoretical and experimental anisotropic glide resistance levels will bridged to the macro-scale crystal plasticity models by generating generalized yield surfaces which can embrace the dislocation core - applied stress tensor interactions.
Short Bio: Sertan Alkan received B.S. (2010) and M.S. (2013) diplomas from Department of Mechanical Engineering at Bogazici University. He is currently a PhD. student in Mechanical Science and Engineering Department at University of Illinois at Urbana-Champaign. During his M.S., he worked on modelling mechanical response of edge cracks in shape memory alloys particularly focusing on the martensitic transformation induced toughening. His PhD. studies involve characterization of fatigue crack growth behavior in nanotwinned Ni-Co alloys via Digital Image Correlation (DIC) technique and establishing a multiscale (continuum and atomistic) theoretical model encompassing the interaction of the crack-tip emitted dislocations with the grain and twin boundaries. Currently, his research mainly focuses on characterization of the slip mediated plasticity and twinning in shape memory alloys and high entropy alloys via DIC technique and atomistic scale simulations within the framework of Density Functional Theory and Molecular Dynamics/Statics.

Rechargeable Next-Generation Magnesium/Oxygen Batteries
 by Gülin Vardar
(Massachusetts Institute of Technology, Nuclear Science and Engineering)
DATE : November 25, 2016 (Friday)
TIME : 11:00-12:00
PDF Version
Electrochemical energy storage devices that are robust, energy-dense, and cheap will accelerate the commercialization of electric vehicles.  
Magnesium/Oxygen (Mg/O2) batteries are a promising system with the potential for very high energy densities. Furthermore, a rechargeable
Mg/O2 battery could be a cheaper and potentially safer alternative to lithium Li-ion batteries currently in use. The goal of this talk is to explore candidate magnesium electrolytes for use in Mg/O2 batteries,  
and to assess the reaction mechanisms and performance of Mg/O2 cells   
that employ these electrolytes.
Short Bio: Gülin Vardar received B.S. diplomas from Boğaziçi University in Mechanical Engineering and Physics in 2010. She received M.S. and PhD. diplomas from the University of Michigan (Ann Arbor) in Materials Science and Engineering. She is currently a postdoctoral research associate in Massachusetts Institute of Technology.

Electrothermal Modeling of AlGaN/GaN Heterostructure Field Effect Transistors
by Nazlı Dönmezer
(Middle East Technical University, Department of Mechanical Engineering)
DATE : October 7, 2016 (Friday)
TIME : 14:00-15:00
Nitride-based semiconductors and materials have been promising candidates for wide variety of technological applications such as nitride based power electronics, satellite communication, and light    emitting diodes. AlGaN/GaN based Heterostructure Field Effect Transistors (HFETs), that are used in high power and frequency applications have been intensively used due to their high-efficiency    power switching and large current handling capabilities. In these devices the high power densities and localized heating form small, high temperature regions called hotspots. Analysis of the heat removal from hotspots and temperature control of the entire device is necessary for the reliable design of HFET devices. Due to the resolution limits of the current experimental characterization    techniques and the geometry of the device that limits the accurate temperature measurement, thermal simulations are necessary. The aim is to build an accurate yet efficient electro-thermal model for the analysis and improvement of HFETs.
Short Bio: Dr. Nazli Donmezer is an Assistant Professor in the Mechanical Engineering Department of Middle East Technical University. She received her PhD. from Woodruff School of Mechanical Engineering   at the Georgia Institute of Technology and her M.S. from Middle East   Technical University in 2013 and 2009 respectively. During her PhD  she  worked on the development of a multiscale model  to simulate the   thermal response of devices with nanometer sized hotspots under the   supervision of Dr. Samuel Graham. She was a recipient of the   Schlumberger "Faculty for the Future" (FFTF) scholarship during her   PhD. studies. Dr. Donmezer joined the faculty at METU in Fall 2014.   She is currently leading a research group  where the goal is to   characterize the electro-thermal behavior of  the nitride devices and materials.