International Journal of Mechatronics and Automation (6 papers in press)
An Efficient Rotational Matrix Extraction Scheme for Finite Element Method Based Deformation
by Xiufen Ye, Jianguo Zhang, Peng Li
Abstract: The co-rotational finite element method (co-rotational FEM), which was first introduced in physics-based computer animations, has shown its strengths to be a feasible approach to modeling the process of soft tissue deformation in a virtual surgery simulation system. In this study, we mainly investigated the method of extracting the rotational matrix and the extracted matrix is used to perform stiffness warping assembly at each simulation time step. We first introduced and compared the time-consuming polar decomposition method and the efficient QR decomposition method, and then our hybrid rotational matrix extraction method is described. In addition, the specific situation of a virtual surgery system has been taken into account, in which the deformation usually occurs in a small local area. The final experimental results show that our efficient rotational matrix extraction method can improve the computation efficiency greatly without deformation accuracy losing.
Keywords: Co-rotational FEM, Rotational matrix extraction, Soft tissue deformation, Virtual surgery
Releasing of Micro-Objects based on Local Stream Generation by High-Speed Motion of End Effector
by Eunhye Kim, Masaru Kojima, Kazuto Kamiyama, Mitsuhiro Horade, Yasushi Mae, Tatsuo Arai
Abstract: In the micromanipulation, releasing of micro-object is a challenge work due to a difficulty of controlling adhesion forces. To overcome the adhesion force and place micro-object with the position accuracy, in this paper, local stream generated by high-speed motions of an end effector is proposed. The compacted parallel link creates 3D high-speed motions without uncontrollable vibration, which means local stream can generate enough force with 3D direction for releasing. Applying the local stream created using the right end-effector, micro-objects including 55um microbeads and NIH3T3 cells attached to the left end effector was released. To verify the placing positions of the objects, we compared four motions, 1D motions (X and Z direction) and circular motions (clockwise and counterclockwise direction), by analyzing the trajectory of the objects after the separation. From these results of experiments, we concluded that the circular motion (CCW) detached microobjects at the nearest position from the end-effector.
Keywords: Micromanipulation, Local stream, High speed motion, Releasing task, Adhesion force
Research of the Delaying Crack Propagation on an Aero-Engine Rotor
by Jun Liu
Abstract: Due to the action of alternating loads, the micro defects of rotors materials and the micro traumas in the mechanic processing would easily cause the crack propagation and even the catastrophic accidents. Vibration characteristics of the rotor system of an aero-engine, the cracks breathing states and breathing periods are investigated with different parameters including the rotational speed, the crack angles, the crack depth and nonlinear parameters. By comparing influences of the crack breathing states caused by changes of different parameters, the paper summarized the mutation regulations of the crack breathing states in the synchronous and verified the feasibility of the mechanism on delaying the crack propagation. The paper also proposed a novel method of the delaying crack propagation, in this method the Electro-Magnetic Actuator (EMA) was used to realize the vibration controlling states and to delay crack propagation in the running process of the nonlinear cracked rotor in an aero-engine. The validity of the proposed method was verified through experiments.
Keywords: Delaying Crack Propagation; Nonlinear Cracked Rotor; Electro-Magnetic Actuator; Vibration Control; Crack Breathing State.
Generation of Rotational Flow for Formation of Spheroids by Using Microfluidic and Dielectrophoretic Hybrid Device
by Masaru Kojima, Mitsuhiro Horade, Hirochika Takai, Kenichi Ohara, Tamio Tanikawa, Kazuto Kamiyama, Yasushi Mae, Tatsuo Arai
Abstract: Toroidal-like sheroids are important in the field of tissue engineering. However, the formation processes of toroidal-like spheroids may not be considered efficient, as most of them are manual. In this paper, we suggest the possibility and effectiveness of applying microfluidics for formation of toroidal-like spheroids. The concept of our method is that cells are compressed by rotational flow in a microchannel and dielectrophoretic force. Some types of microchannels that can generate rotational flow were designed and were analyzed with flow analysis software. A superior microchannel was fabricated, and a flow of NIH3T3 cell suspension was supplied to the channel. As the flow rate was changed, the cells were rotated in the microchannel according to our concept, and approximately 30% of them remained in the channel. This result supports our concept: toroidal-like spheroids can be formed under the influence of forces of rotational flow and dielectrophoresis.
Keywords: Microfluidics; Microelectromechanical systems (MEMS); Spheroid; Dielectrophoresis
Error Propagation and Solvability in UAV Localization based on Trilateration with a Multi Robot Formation
by Luis Ruiz, Zhidong Wang
Abstract: This works presents how the propagation of errors from stations affects the trilateration, as seen from the error in the receiver covariance. Also a method to calculate a solvability map in real time is developed. This map is useful to select formations when using trilateration and to choose how a multi robot formation has to move in a given environment. The mathematical tools used are explained and proven in a real time test and a simulation. The multi robot formation consists of omnidirectional wheeled mobile robots and a unmanned aerial vehicle in three dimensions.
Keywords: Trilateration; Solvability; Multi Robot; Localization.
Prototyping and Characterization of a Variable Stiffness Actuation Mechanism Based on Low Melting Point Polymer
by Wenjun Xu, Hongliang Ren
Abstract: With the advent of automation and robotic systems, flexible robotic manipulators are becoming increasingly popular in various applications where safe interaction with surrounding environments is needed. This project aims to investigate stiffness varying technology for a class of flexible manipulators with the aim of online changing manipulator stiffness. We propose and develop a stiffness varying mechanism based on low melting point Polycaprolactone (PCL), characterize it and test out together with extensive experiments. The proposed mechanism is further integrated into a tendon-driven flexible manipulator and it successfully change the overall stiffness of the manipulator. This paper mainly involves design improvement, modeling, characterization and hands-on experiments.
Keywords: flexible manipulator; stiffness varying mechanism; surgical manipulator; stiffness control;.