The Role of Computer Simulations in Optimization Exoskeletons

Monday May 12th 2025 at 14:00 

Wolfson Building of Mechanical Engineering, Room 206

Abstract:

The design of exoskeletons poses a complex challenge that goes beyond traditional robotic systems, as the interaction between humans and exoskeletons must be taken into account. In contrast to controlled robots, exoskeletons must be seamlessly integrated into the human musculoskeletal system, which requires appropriate control strategies and an understanding of human motion dynamics. In this talk, I will review the three main methods for developing exoskeletons: 1) Test and rebuild, 2) Human in the loop, and 3) simulation. I will mainly focus on simulation, which includes models of both the electromechanical system and the biomechanics of the human user. The advantages and limitations of the simulation method will be demonstrated using several exoskeletons that we have built in our lab: (1) biomechanical energy harvester, designed to produce electricity without increasing the user’s effort; (2) exoskeleton for vertical jumping that allows explosive movements at high speed, unlike most exoskeletons that are designed for continuous use in aerobic tasks (e.g., walking, running, lifting). Thus, we have developed the first exoskeleton that increases the user's jumping height and investigated the interactions between humans and exoskeletons. While traditional simulation uses experimental trajectories without the actual exoskeletons, we have developed a simulation for jumping exoskeletons that enables motion adaptation for improved utilization. We also compared the simulation results with experimental data using an actual exoskeleton. This framework was extended to also create a simulation for a running exoskeleton. The results of our studies reveal similarities and important discrepancies between experiments and simulations and shed light on the limitations of current modeling techniques.

Bio:

Raziel Riemer is an Associate Professor at the Department of Industrial Engineering and Management at Ben-Gurion University of the Negev. He holds a B.Sc. in Mechanical Engineering and an M.Sc. in Industrial Engineering, both from Ben-Gurion University of the Negev, and a Ph.D. in Mechanical and Industrial Engineering from the University of Illinois at Urbana-Champaign, USA. His research interests are in the areas of human motion analysis, modelling and simulation and wearable robotics. Prior to his academic career, Raziel worked in industry for six years as a mechanical and industrial engineer, primarily at Intel. In the distant past, he was a competitive swimmer (Israel champion and record holder) and enjoys using his knowledge of biomechanics to improve the performance of athletes.

Experimental optimization of a 3-element high-lift system with active flow control

Monday April 28th 2025 at 14:00 

Wolfson Building of Mechanical Engineering, Room 206 

Abstract:

The Seminar will present the experimental investigation of the efficiency of Active Flow Control (AFC) as a means of enhancing the aerodynamic performance of aircraft wings. The overarching goal is to demonstrate its economic viability and potential for widespread use in the aviation industry. By actively generating several forms of oscillatory blowing and suction, the airflow around various wing models is manipulated to augment the aerodynamic characteristics of the airfoils.

The research encompasses three experimental studies, each employing wind tunnel experiments to assess the effectiveness of AFC in diverse scenarios. The first study experimentally examines the feasibility of replacing a conventional leading-edge slat with an AFC system that integrates suction and oscillatory blowing, aiming to achieve comparable aerodynamic benefits with reduced weight and complexity. The second study focuses on mitigating local flow separation induced by integrating ultra-high bypass ratio engines with the wing, utilizing suction and pulsed blowing to redirect and re-energize the flow in the affected region. The final study experimentally investigates the potential of AFC for controlling flutter, a detrimental aeroelastic phenomenon, by implementing a closed-loop control system based on fluidic oscillators.

The findings of these studies collectively highlight the capability of AFC to increase lift, delay stall, and mitigate flow separation, thereby contributing to improved aerodynamic efficiency and reduced fuel consumption in aircraft. The research also includes an in-depth discussion on the energy efficiency of the AFC systems, emphasizing the importance of minimizing energy consumption for practical implementation. The thesis underscores the promise of AFC as a practical and effective solution for enhancing the performance and sustainability of future aircraft designs, supported by concrete experimental evidence. The research also delves into the complexities of implementing AFC in real-world scenarios, addressing system integration, control algorithms, and scalability challenges. The thesis concludes by highlighting the potential of AFC to revolutionize aircraft design and operation, enabling the development of more efficient, quieter, safer, and environmentally friendly aircraft.

Bio:

Shay Monat is a PhD student in the Meadow Aerodynamics Laboratory under the former guidance of Prof. Avi Seifert (R.I.P) and currently under the guidance of Prof. Alex Liberzon and Prof. Oksana Stalnov.

Biocomposite Reinforced with Soft Coral Collagen Fibers: Towards Bio-inspired Cardiovascular Tissue Therapies

Monday April 7th 2025 at 14:00 

Wolfson Building of Mechanical Engineering, Room 206 

Abstract:

Cardiovascular diseases (CVDs) are the leading cause of death worldwide, with coronary artery disease (CAD) and aortic stenosis (AS) being among the most prevalent conditions requiring surgical intervention. While synthetic grafts are effective for large blood vessels, they often fail in small-diameter applications. Similarly, current mechanical and bioprosthetic aortic valves have inherent limitations, such as the need for lifelong anticoagulation therapy and the risk of structural deterioration, respectively, highlighting the need for advanced biomaterials that mimic the mechanical properties and microstructure of the native tissues.

This research aims to develop novel biocomposites reinforced with ultra-long collagen fibers extracted from soft coral for use in small-diameter blood vessels (SDBVs) and aortic valve (AV) replacements. Experimental and computational studies were conducted to evaluate their mechanical behavior. Multi-scale micromechanical tissue models were developed and calibrated for both native and coral-collagen-based media. Finite element (FE) models were developed to predict the mechanical response of biocomposite constructs, demonstrating good agreement with experimental data. The proposed AV prosthetic leaflet designs are bioinspired by native microstructure. These and the entire AV were modeled using a structural parametric FE model. The results showed improved stress distribution and reduced mechanical fatigue risk.

Fluid-structure interaction (FSI) simulations provided additional hemodynamic insights into the biomechanical performance of the biocomposite AV, revealing comparable systolic flow behavior to native valves. However, differences in closure dynamics, compared to native AV, suggest that optimizing fiber volume fraction and matrix stiffness could enhance valve function. This research pioneers coupling experimental and computational approaches to advance biocomposite cardiovascular implants, offering significant promise for addressing the complex challenges associated with AV and SDBV replacements.

Bio:

Shir is a Ph.D. candidate at the School of Mechanical Engineering, Tel Aviv University, under the supervision of Prof. Rami Haj-Ali. Her research focuses on computational biomechanics and experimental mechanics of biocomposites, aiming to design and develop novel biocomposite materials reinforced with soft coral collagen fibers, inspired by the native cardiovascular tissues. Her M.Sc. research, also conducted in Prof. Haj-Ali's lab, focused on developing a novel biocomposite material for engineered small-diameter blood vessel grafts. Shir has been awarded a fellowship from the Ministry of Science to support her Ph.D. studies. She holds a B.Sc. in Biomedical Engineering and an M.Sc. in Mechanical Engineering, both from Tel Aviv University.

פרטים בהמשך..