Current Issue : April - June Volume : 2019 Issue Number : 2 Articles : 5 Articles
Recently, the number of alpine ski junior players in Japan has drastically decreased.\nThe causes include a decrease in ski areas and instructors, along with difficulty of early childhood\nalpine ski guidance. The alpine ski competition is not simply a glide on a slope. It requires\nunderstanding of ski deflection and skier posture mechanics. Therefore, a passive ski robot without\nan actuator was developed for junior racers of the alpine ski competition to facilitate understanding\nof the turn mechanism. Using this robot can elucidate factors affecting ski turns, such as the position\nof the center of gravity (COG) and the ski shape. Furthermore, a mechanism for changing the COG\nheight, the edge angle and the ski deflection is added to the passive turn type ski robot. The developed\nski robot can freely control the turn by changing those parameters during sliding....
Crack assessment when making fitness-for-service decisions requires a thorough examination\nof crack location and size in critical areas. An ultrasonic transducer is used for such assessments,\nbut traditional methods cannot cope with complex rotators, such as wheel hubs. We present a model\nof robot-assisted crack growth assessment in wheel hubs. We integrate a six-degrees-of-freedom\n(DOF) industrial robot and a turntable to form a robot-assisted ultrasonic testing (UT) system that\ndoes not use traditional UT equipment. Ultrasonic beams are focused at certain depths appropriate\nfor achieving maximum sensitivity.We quantitatively analysed wheel hubs with longitudinal and\ntransverse series of pre-cracks, and concluded that our system autonomously detected cracks....
The force analysis of a pelvic support walking robot with joint compliance is discussed in this paper. During gait training, pelvic\nmotions of hemiplegic patients may be excessively large or out of control; however, restriction of pelvic motions is not likely to\nfacilitate successful rehabilitation. A robot-assisted pelvic balance trainer (RAPBT) is proposed to help patients control the range\nof motion via force field, and force analysis is necessary for the control of the compliant joints. Thus, kinematic model and static\nmodel are developed to derive the Jacobian and the relation between the interaction forces and the pelvic movements, respectively.\nSince the joint compliance is realized through a nontorsional spring, a conventional (linear) Jacobian method and a piecewise\nlinear method are derived to relate the interaction forces with the pelvis movements. Three preliminary experiments are carried\nout to evaluate the effectiveness of the proposed methods and the feasibility of the RAPBT. Theexperiment results indicate that the\npiecewise linear method is effective in the calculation of the interaction forces. Gait with pelvic brace strongly resembles free\noverground walking and partly decreases motion range via force field. The findings of this research demonstrate that the pelvic\nbrace with joint compliance may provide effective interventions....
This research presents Pure Condition approach, which has used in analyzing\nsimultaneously the singularity configuration and the rigidity of mechanism.\nThe study cases analysis is implemented on variable joints orientation of 6R\n(Revolute) Serial Manipulators (SMs) and variable actuated joints position of\n3-PRS (Prismatic-Revolute-Spherical) Parallel Manipulators (PMs) using\nGrassmann-Cayley Algebra (GCA). In this work we require in Projective\nSpace both Twist System (TS) and Global Wrench System (GWS) respectively\nfor serial and parallel manipulators which represent the Jacobian Matrix (J) in\nsymbolic approach to Plücker coordinate vector of lines and unify framework\non static and kinematics respectively. This paper, works, is designed to determine\ngeometrically at symbolic level the vanished points of inverse form of\nthis Jacobian Matrix (J) which called superbracket in GCA. The investigation\nvary to those reported early by introducing GCA approach on the singularity\nof serial robot, variable joints orientation and actuated positions on robot\nmanipulators (RMs) to analyze rigidity frame work and singularity configuration\nwhich involve simultaneously Pure Condition. And the results also revealed\na single singularity condition which contains all particulars cases and\nthree general cases such as the shoulder, elbow and wrist singularity for\nSMs while double, single and undermined singularities respectively for\n3-PRS, 3-PRS and 3-PRS PMs which contain all generals and particulars\ncases....
In order to eliminate the influence of the joint torsional vibration on the system operation\naccuracy, the parameter identification and the elastic torsional vibration control of a flexible-joint\nrobot are studied. Firstly, the flexible-joint robot system is equivalent to a rotor dynamic system, in\nwhich the mass block and the torsion spring are used to simulate the system inertia link and elasticity\nlink, for establishing the system dynamic model, and the experimental prototype is constructed.\nThen, based on the mechanism method, the global electromechanical-coupling dynamic model of\nthe flexible-joint robot system is constructed to clear and define the mapping relationship between\nthe driving voltage of the DC motor and the rotational speed of joint I and joint II. Furthermore,\nin view of the contradiction between the system response speed and the system overshoot in\nthe vibration suppression effect of the conventional PID controller, a fuzzy PID controller, whose\nparameters are determined by the different requirements in the vibration control process, is designed\nto adjust the driving voltage of the DC motor for attenuating the system torsional vibration. Finally,\nsimulation and control experiments are carried out and the results show that the designed fuzzy PID\ncontroller can effectively suppress the elastic torsional vibration of the flexible-joint robot system\nwith synchronization optimization of control accuracy and dynamic quality....
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