Koh Hosoda Pengarang

Normal contact stiffess identifiation-based force compensation for a hardwarein-the-loop docking simulator Qian Wang a, Chenkun Qia, Feng Gaoa, Xianchao Zhaoa, Anye Ren b and Yan Hu a astate Key Laboratory of Mechanical system and vibration, school of Mechanical engineering, shanghai Jiao tong University, shanghai, china; binstitute of Aerospace system engineering shanghai, shanghai, china ABSTRACT Docking is a very important and challenging space operation. To ensure the safety and reliability of the docking, the thorough ground verifiation is necessary. Hardware-in-the-loop (HIL) simulation is a good choice, especially when the geometric structure of the docking device is complex. However, the HIL simulation suffrs from energy increase and instability since time delay in the system is unavoidable. In this study, a six degree-of-freedom (DOF) parallel robot is used as the motion simulator to physically perform the contact in the simulation. To achieve system stability and high fielity, a normal contact stiffess identifiation-based force compensation method is proposed. The contact force is compensated through identifying the time-varying stiffess along the normal direction of the contact surface. The 6-DOF force-moment compensation algorithm for the HIL parallel robot system is presented in detail. Simulations and experiments are both carried out, and the results show that the proposed compensation method is effctive. KEYWORDS Hardware-in-the-loop simulation; space docking; contact; time delay; delay compensation; 6-doF parallel robot Quadtree-based ancestry tree maps for 2 D scattered data SLAM Ilari V allivaara , Katja Poikselkä, Anssi Kemppainen and Juha Röning Computer Science and Engineering (CSE), U niversity of Oulu, O ulu, Finland ABSTRACT In a typical Rao-Blackwellized particle filter Simultaneous localization and mapping (SLAM), each particle carries its own map. Ancestry tree maps are proposed in the literature to handle occupancy grid maps with a large memory footprint, allowing very large particle counts. This paper describes how quadtrees can be used to implement ancestry tree maps in scattered data SLAM. We introduce a logarithmic-time query method to provide a natural neighborhood-like local polygonal neighborhood. Further, we propose an efficient and simple-to-implement local interpolant utilizing the polygonal neighborhood, and show that the interpolant RMSE is comparable to Sibson interpolant. We combine the query method with an ancestry tree consisting of quadtrees to obtain an effective map representation for scattered data SLAM. With map size of n and number of particles P, we obtain an average case time complexity of O( P( log n + log P log log P)) per time step. The introduced approach is experimentally validated on magnetic field SLAM with real-world data, showing that the performance is in line with the derived time complexity. The literature suggests that with ancestry trees the memory consumption drops from O( nP) to O( n+ P) in practice. Empirical data confirm that this seems to be the case also with scattered data SLAM. KEYWORDS SLAM; quadtree; ancestry tree; scattered data; R BPF Robust adaptive admittance control of an exoskeleton in the presence of structured and unstructured uncertainties Hossein Shahia, Aghil YousefiKomaa and Majid Mohammadi Moghaddam b acenter of Advanced systems and technologies (cAst), school of Mechanical engineering, college of engineering, University of tehran, tehran, iran; bMechatronics Laboratory, department of Mechanical engineering, tarbiat Modares University, tehran, iran ABSTRACT In this paper, an admittance control scheme for a user-in-charge exoskeleton is presented. The controller basically consists of a composite adaptive controller implementing a feedback law to estimate the structured uncertainties and to modify the apparent dynamics of the robot, and an LWPR estimator which tries to give an appropriate approximation of unmodeled uncertainty along with a robust term aiming to overcome the approximation residue. The control scheme offrs a unifid general control structure that explains the effct of each control component on the others. It is proved that based on the developed controller, the tracking and estimation errors converge to small boundaries with ultimate boundedness property due to the presence of the unstructured uncertainty. Based on simulations of a 2-DOF leg, the effctiveness of the controller is investigated. The results show the effctiveness of employing a universal approximator alongside a robust adaptive control and the success of the recommended approach in estimating model parameters and unmodeled dynamics simultaneously. KEYWORDS Admittance control; composite adaptive control; Lyapunov redesign; mixed structured and unstructured uncertainties; locally weighted projection regression (LWPR); lower limb exoskeleton Statistically optimized FOPID for output force control of SEAs Somayeh Norouzi Ghazbi, Alireza Akbarzadeh and Iman Kardan center of excellence on soft computing and intelligent information Processing (sciiP), Mechanical engineering department, Ferdowsi University of Mashhad, Mashhad, iran ABSTRACT Fractional order PID (FOPID) controllers have recently found an increasing application in diffrent filds of control. Comparing to traditional PID algorithms, FOPID controllers provide more flxibility and better performances. The simple and non-model-based structure of FOPID controllers has boosted their usage in real-world applications. However, due to having two more control parameters than regular PID controllers and the non-linear structure of FOPID controllers, the tuning procedure of these controllers is still a challenge. The authors of the present paper have recently proposed a Taguchi-based gain tuning algorithm for tuning of control parameters of FOPID controller. The present paper is an experimental evaluation of the proposed method. A custom made SEA, FUMLSEA, is used as the test bed in this study. Deriving a dynamic model of the FUM-LSEA, feed-forward terms are added to the controller to compensate for disturbances from motions of the output block. Optimal gains and orders of the controller are obtained through a set of experiments suggested by the Taguchi method. The Taguchi optimized controller is also compared to a Ziegler–Nichols tuned controller. The experimental results indicate 45% improvements in force tracking error. KEYWORDS seA; FoPid; taguchi; tuning; AnovA