Frontiers of Mechanical Engineering

ISSN 2095-0233

ISSN 2095-0241(Online)

CN 11-5984/TH

Postal Subscription Code 80-975

2018 Impact Factor: 0.989

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, Volume 7 Issue 2

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EDITORIAL
RESEARCH ARTICLE
Planar jumping with stable landing through foot orientation design and ankle joint control
Qilong YUAN, I-Ming CHEN
Front Mech Eng. 2012, 7 (2): 100-108.  
https://doi.org/10.1007/s11465-012-0318-3

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This paper introduces a method to generate the planar jumping motion for biped robot. In this work, through determining the upper body posture trajectory in the flight phase, the foot landing posture is made to be flat while landing. Together with properly designing the trajectory for local center of gravity and the foot landing velocity, the soft landing trajectory is generated. A controller on the ankle joint is added to avoid significant impact with the ground and stabilize the robot after landing. Jumping motion with stable landing is achieved in a dynamic simulation environment based on this method.

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A method to calculate working capacity space of multi-DOF manipulator and the application in excavating mechanism
Baochen WEI, Feng GAO
Front Mech Eng. 2012, 7 (2): 109-119.  
https://doi.org/10.1007/s11465-012-0323-6

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Working capacity refers to the velocity output and force output of a manipulator. It is usually be represented by output capacity space. In this paper, the method of Linear Programming and a geometric method are proposed to calculate working capacity spaces in different situations. With the consideration of gravity effect of every component, the output force capacity space of heavy duty manipulators is calculated. The results show that the effect of the gravity is a translation of the capacity space. This paper gives a method for the output capacity express especially for heavy duty manipulators. The output capacity space can be helpful to the driving parameters selection. With the consideration of the gravity effect of every component and the friction at the joints, the excavating force capacity space of the heavy-load excavating mechanism is calculated and is represented as a multi-dimensional polytope. The results show that the effect of the gravity and friction is to translational act on the capacity space.

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Influence of kinematic redundancy on the singularity-free workspace of parallel kinematic machines
Jens KOTLARSKI, Bodo HEIMANN, Tobias ORTMAIER
Front. Mech. Eng.. 2012, 7 (2): 120-134.  
https://doi.org/10.1007/s11465-012-0321-8

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In this paper the effect of kinematic redundancy in order to reduce the singularity loci of the direct kinematics and to increase the operational, i.e., singularity-free, workspace is demonstrated. The proposed approach consists of additional prismatic actuators allowing one or more base joints to move linearly. As a result, a selective reconfiguration can be performed in order to avoid singular configurations. Exemplarily, kinematically redundant schemes of four structures, the 3RRR, the 3RPR, the 6UPS, and the 6RUS, are considered. The relationship between the redundancy and the operational workspace is studied and several analysis examples demonstrate the effectiveness of the proposed concept. Furthermore, the additional benefit of an increasing number of redundant actuators is discussed.

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Contribution to the design of robotized tele-echography system
T. ESSOMBA, M. A. LARIBI, J. P. GAZEAU, S. ZEGHLOUL, G. POISSON
Front Mech Eng. 2012, 7 (2): 135-149.  
https://doi.org/10.1007/s11465-012-0326-3

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This paper introduces the design of a master-slave robotized system for tele-ultrasound application. The objective of these researches is to design the slave manipulator of this system and its control device (master part). The specification process of the architecture kinematic is based on the analysis of expert’s gesture during ultrasound examinations. These studies have been carried out using a motion capture system. The medical gestures were analyzed in terms of ultrasound probe attitude and used in the definition of the kinematics specifications of the proposed manipulator. The Spherical Parallel Mechanism is selected because its characteristics meet the constraint requirements. The optimal synthesis of spherical parallel manipulators is performed using a real-coded Genetic Algorithm based method. Simulations on the actuator responses of the structure allowed us the validate it. In order to control this robot, we have also designed a haptic device that provides easiness to use as well as force feedback. Its orientation control strategy is based on a use of an adaptative kalman filter which efficiency was demonstrated during experimentations.

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Synthesis of spherical parallel manipulator for dexterous medical task
Abdelbadia CHAKER, Abdelfattah MLIKA, Med Amine LARIBI, Lotfi ROMDHANE, Sa?d ZEGHLOUL
Front Mech Eng. 2012, 7 (2): 150-162.  
https://doi.org/10.1007/s11465-012-0325-4

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This paper deals with the design and the analysis of a spherical parallel manipulator (SPM) for a haptic minimally invasive surgery application. First the medical task was characterized with the help of a surgeon who performed a suture technique called anastomosis. A Vicon system was used to capture the motion of the surgeon, which yielded the volume swept by the tool during the anastomosis operation. The identified workspace can be represented by a cone with a half vertex angle of 26°. A multi objective optimization procedure based on genetic algorithms was then carried out to find the optimal SPM. Two criteria were considered, i.e., task workspace and mechanism dexterity. The optimized SPM was then analyzed to determine the error on the orientation of the end effector as a function of the manufacturing errors of the different links of the mechanism.

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Singularity and workspace analysis of three isoconstrained parallel manipulators with schoenflies motion
Po-Chih LEE, Jyh-Jone LEE
Front Mech Eng. 2012, 7 (2): 163-187.  
https://doi.org/10.1007/s11465-012-0324-5

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This paper presents the analysis of three parallel manipulators with Schoenflies-motion. Each parallel manipulator possesses two limbs in structure and the end-effector has three DOFs (degree of freedom) in the translational motion and one DOF in rotational motion about a given direction axis with respect to the world coordinate system. The three isoconstrained parallel manipulators have the structures denoted as CuuUwHw-//-CvvUwHw, CuRuuUhw-//-CvRvvUhw and CuPuUhw-//- CvPvUhw. The kinematic equations are first introduced for each manipulator. Then, Jacobian matrix, singularity, workspace, and performance index for each mechanism are subsequently derived and analysed for the first time. The results can be helpful for the engineers to evaluate such kind of parallel robots for possible application in industry where pick-and-place motion is required.

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Design and preliminary evaluation of an exoskeleton for upper limb resistance training
Tzong-Ming WU, Dar-Zen CHEN
Front Mech Eng. 2012, 7 (2): 188-198.  
https://doi.org/10.1007/s11465-012-0327-2

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Resistance training is a popular form of exercise recommended by national health organizations, such as the American College of Sports Medicine (ACSM) and the American Heart Association (AHA). This form of training is available for most populations. A compact design of upper limb exoskeleton mechanism for home-based resistance training using a spring-loaded upper limb exoskeleton with a three degree-of-freedom shoulder joint and a one degree-of-freedom elbow joint allows a patient or a healthy individual to move the upper limb with multiple joints in different planes. It can continuously increase the resistance by adjusting the spring length to train additional muscle groups and reduce the number of potential injuries to upper limb joints caused by the mass moment of inertia of the training equipment. The aim of this research is to perform a preliminary evaluation of the designed function by adopting an appropriate motion analysis system and experimental design to verify our prototype of the exoskeleton and determine the optimal configuration of the spring-loaded upper limb exoskeleton.

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Modular design of typical rigid links in parallel kinematic machines: Classification and topology optimization
Xinjun LIU, Xiang CHEN, Zhidong LI
Front Mech Eng. 2012, 7 (2): 199-209.  
https://doi.org/10.1007/s11465-012-0315-6

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Due to the demand of reconfigurable system in parallel kinematic machines (PKMs), modular design technology is significant and necessary. However, in earlier research, the core joint modules have been concerned about rather than the customized link modules. The modular design to the typical customized links from the point of seeking optimal structures with best mechanical performances is analyzed and processed in two steps: classification and optimization. Firstly, a brief introduction to the current research status and the aims of this paper are outlined. And then, how the typical customized links classified is proposed. Next, the technology method and the iterative formula derivation process of topology optimization are described in detail. Finally, calculation models for each group of classified ones are set up and their optimal structures are achieved through topology optimization technique. The results provide useful references for reconfigurable and modular design in engineering cases.

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Parasitic rotation evaluation and avoidance of 3-UPU parallel mechanism
Haibo QU, Yuefa FANG, Sheng GUO
Front Mech Eng. 2012, 7 (2): 210-218.  
https://doi.org/10.1007/s11465-012-0317-4

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Based on the prototype of 3-UPU (universal-prismatic-universal joint) parallel mechanism proposed by Tsai [1], the parasitic rotation evaluation is performed and calculated the bound of instability of SNU Seoul National University 3-UPU parallel mechanism. Through analysis of the terminal constraint system of the 3-UPU parallel mechanism, the equation about the parasitic rotation and limited clearance is presented. Then the norm of possible parasitic rotation is employed to evaluate the mechanism stability with limited clearance. The higher this number the worst is the pose, the lower it is the best it is. And the contour atlas of parasitic rotation is obtained, which can be used for further analysis and design. With the practice experiment result of SUN 3-UPU parallel mechanism, we find it’s bound of instability, which indicates there will appear the parasitic rotation when the number exceeds the bound. Finally, the method for avoidance of possible parasitic motions is presented by adding redundantly actuated limbs.

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A total torque index for dynamic performance evaluation of a radial symmetric six-legged robot
Kejia LI, Xilun DING, Marco CECCARELL
Front Mech Eng. 2012, 7 (2): 219-230.  
https://doi.org/10.1007/s11465-012-0320-9

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This article focuses on the dynamic index and performance of a radial symmetric six-legged robot. At first the structure of the robot is described in brief and its inverse kinematics is presented. Then the dynamic model is formulated as based on the Lagrange equations. A novel index of total torque is proposed by considering the posture of the supporting legs. The new index can be used to optimize the leg’s structure and operation for consuming minimum power and avoiding unstable postures of the robot. A characterization of the proposed six-legged robot is obtained by a parametric analysis of robot performance through simulation using the presented dynamic model. Main influences are outlined as well as the usefulness of the proposed performance index.

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11 articles