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Disturbance Observer-based Trajectory Following Control of Robot Manipulators
Mohamadreza Homayounzade,Amir Khademhosseini 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.1
Robotic manipulators are usually subject to different types of disturbances. If the effects of such disturbancesare not taken into account, it can lead to unsatisfactory tracking performance of the robot and may evendestabilize the robot control system. In this paper a novel nonlinear disturbance observer-based controller is designedfor robotic manipulators. Previous disturbance observer-based controllers which are designed for roboticsystems undergo the restricting assumption that the external disturbance is constant. In this paper a novel two-stageprocedure is proposed to design a disturbance observer that improves disturbance attenuation ability of current disturbanceobserver-based controllers. The proposed method can cope with non-constant disturbance. Furthermore,it is shown that even for the fast time varying disturbance, the controller achieves satisfactory tracking performance. The proposed controller guarantees semi-global asymptotic position and velocity tracking and moreover, removesrestrictions of previous studies on the number of degrees of freedom (DOFs), joint types, and manipulator configuration. The effectiveness of the proposed method is verified against different types of external disturbance appliedon the robot manipulator and the results are compared with the results of previous methods. Furthermore, the resultssupport the theoretical conclusions.
Benchtop fabrication of PDMS microstructures by an unconventional photolithographic method
Hwang, Chang Mo,Sim, Woo Young,Lee, Seung Hwan,Foudeh, Amir M,Bae, Hojae,Lee, Sang-Hoon,Khademhosseini, Ali IOP Pub 2010 Biofabrication Vol.2 No.4
<P>Poly(dimethylsiloxane) (PDMS) microstructures have been widely used in bio-microelectromechanical systems (bio-MEMS) for various types of analytical, diagnostic and therapeutic applications. However, PDMS-based soft lithographic techniques still use conventional microfabrication processes to generate a master mold, which requires access to clean room facilities and costly equipment. With the increasing use of these systems in various fields, the development of benchtop systems for fabricating microdevices is emerging as an important challenge in their widespread use. Here we demonstrate a simple, low-cost and rapid method to fabricate PDMS microstructures by using micropatterned poly(ethylene glycol) diacrylate (PEGDA) master molds. In this method, PEGDA microstructures were patterned on a glass substrate by photolithography under ambient conditions and by using simple tools. The resulting PEGDA structures were subsequently used to generate PDMS microstructures by standard molding in a reproducible and repeatable manner. The thickness of the PEGDA microstructures was controllable from 15 to 300 µm by using commonly available spacer materials. We also demonstrate the use of this method to fabricate microfluidic channels capable of generating concentration gradients. In addition, we fabricated PEGDA microstructures by photolithography from the light generated from commonly available laminar cell culture hood. These data suggest that this approach could be beneficial for fabricating low-cost PDMS-based microdevices in resource limited settings.</P>
Integrin-Mediated Interactions Control Macrophage Polarization in 3D Hydrogels
Cha, Byung-Hyun,Shin, Su Ryon,Leijten, Jeroen,Li, Yi-Chen,Singh, Sonali,Liu, Julie C.,Annabi, Nasim,Abdi, Reza,Dokmeci, Mehmet R.,Vrana, Nihal Engin,Ghaemmaghami, Amir M.,Khademhosseini, Ali Wiley (John WileySons) 2017 Advanced healthcare materials Vol.6 No.21