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Jafari, Aghil,Nabeel, Muhammad,Ryu, Jee-Hwan IEEE 2017 IEEE TRANSACTIONS ON ROBOTICS Vol.33 No.4
<P>Passivity has been a major criterion for designing a stable haptic interface due to its numerous advantages. However, passivity-based controllers have suffered from the design conservatism of the passivity criterion, particularly when users want to increase the maximum apparent impedance. Based on the input-to-state stable (ISS) criterion and an analogy between haptic interfaces and systems with hysteresis, this paper proposes a control framework that is less conservative than passivity-based controllers. The proposed ISS approach allows a non-predetermined finite amount of output energy to be extracted from the system. Therefore, the proposed method can increase the maximum apparent impedance compared with passivity-based approaches. The focus of this paper is on how the proposed approach is designed to satisfy the input-to-state stability criterion in real time without prior knowledge of the system. This paper also extends the primary single-port ISS approach to a two-port ISS approach for multiple-degree-of-freedom generalization. The experimental and numerical results demonstrate that the proposed ISS approach is able to stabilize a higher impedance range than the time-domain passivity approach. The experimental results also confirm that the proposed approach provides higher actual apparent impedance to the operator compared with the energy-bounding and force-bounding approaches.</P>
Hybrid Force-Motion Control of Coordinated Robots Interacting With Unknown Environments
Aghil Jafari,Jee-Hwan Ryu 제어로봇시스템학회 2014 제어로봇시스템학회 국제학술대회 논문집 Vol.2014 No.10
This paper presents a unified framework for system design and control in cooperative robotic systems. It introduces a highly general cooperative system configuration involving any number of manipulators grasping a rigid object in contact with a deformable working surface whose real physical parameters are unknown. Dynamics of the closed chain mechanism is expressed based on the object’s center of mass, and different robust controllers are designed for position and force control subspaces. The position controller is composed of a sliding mode control term, and involves the position and velocity feedback of end-effector, while the force control is developed based on the highest derivative in feedback methodology. The force controller does not use any derivation of the force signal as well as the internal force controller induced in the system, and it appears to be very practical. Simulation results for two three joint arms moving a rigid object are presented to validate the theoretical results.
A De-risked Bio-inspired Condylar Prosthetic Knee Joint for a Robotic Leg Test Rig
Subham Agrawal,Chathura Simasinghe,Aghil Jafari,Appolinaire Etoundi,Jun Jie Chong 제어로봇시스템학회 2020 제어로봇시스템학회 국제학술대회 논문집 Vol.2020 No.10
The design of the human knee joint has been a challenging task due to the presence of intricate parts, complex mechanisms and their interdependence which joins them together. A bio-inspired design for the condylar knee joint has been proposed in earlier publications [1], [2]. However, the manufacturing limitation of the design was not considered. This paper introduces a de-risked and optimised design through the use of standard design and manufacturing techniques based on the gathered data from a robotics leg test bench. Moreover, this paper presents an optimised design derived from a state-of-the-art artificial intelligence tool. The optimized design using conventional methods is tested against real-world loading conditions during finite element analysis and the results are presented.
Hossein Esmaeili,Rauf Foroutan,Dariush Jafari,Mohammad Aghil Rezaei 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.5
The removal efficiency of phosphate ion from aqueous media using magnesium oxide/iron molybdate (MgO/Fe2(MoO4)3) nanocomposite was investigated. MgO nanoparticles were chemically modified by ferric molybdate. Then, the structure and morphology of the nanocomposite was completely investigated using different analyses such as SEM, EDX/Map, FTIR, XRD, TGA, BET, and TEM. The TEM analysis demonstrated that the particles in the mentioned nano-composite were on a nanoscale. BET analysis proved that the nanocomposite was mesoporous with mean pore size of 9.4 nm. The sorption outcomes demonstrated that the highest phosphate sorption yield was achieved at 98.38%, exhibiting remarkable sorption efficiency. Carbonate ions showed to have the highest interfering impact compared to sulfate and nitrate ions, since phosphate ion removal efficiency decreased significantly when carbonate and phosphate ions were simultaneously available in the solution. The thermodynamic studies demonstrated that the current sorption process was spontaneous, possible, and exothermic. The sorption equilibrium investigation showed that the Freundlich isotherm model can describe the adsorption of phosphate ion better than can the Langmuir model, and the maximum sorption capacity was obtained as 30.21mg/g. Additionally, the adsorbent was successfully regenerated four times and was able to perform the sorption and desorption process well.
Panashe Sabau,Jun Jie Chong,Aghil Jafari,Subham Agrawal,Chathura Semasinghe,Appolinaire Etoundi 제어로봇시스템학회 2020 제어로봇시스템학회 국제학술대회 논문집 Vol.2020 No.10
In the past century many medical advancements in prosthetics have been achieved, however, discomfort in prosthetic socket remains one of the toughest challenges faced by both amputees and prosthetists. Wearing an uncomfortable socket can lead to users discontinuing use of their socket and subsequently reducing their long-term mobility; negatively impact their psychological health; and prolong rehabilitation. This paper continues the research conducted in earlier publications [1], [2], which introduced the concept of an automated ISO standard robotic testing rig to test a full artificial limb prosthesis (a bio-inspired transfemoral prosthetic socket attached to robotic prosthetic joints and an ankle joint). This paper presents an automated method of designing the bio-inspired socket using artificial intelligence to reduce discomfort and the design time of new or existing full artificial lower limbs using qualitative and quantitative data. The socket will be tested in a gait simulation shown in the figure 7, to safely achieve desirable walking velocities, step length, safety and comfort while consequentially reducing the physical testing on patients and consequentially reduce physical testing on patients.