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Jinkui Chu - One of the best experts on this subject based on the ideXlab platform.

  • Non-integer-period motion generation of a planar Four-Bar Mechanism using wavelet series
    Mechanism and Machine Theory, 2018
    Co-Authors: Jianwei Sun, Wenrui Liu, Wang Peng, Jinkui Chu
    Abstract:

    Abstract In this paper, on the basis of the theory of the Haar wavelet series, the early proposed method, which is used to solve the problem of planar Four-Bar path synthesis, is extended to motion generation synthesis of a planar Four-Bar Mechanism. By analysing the wavelet coefficients between the rigid-body rotation angle and the connecting rod rotation angle of its corresponding basic dimensional type, the internal relationships are determined. Based on this finding, an output feature parameters database of planar Four-Bar motion generation including 101,408 sets of the basic dimensional type was established. Using the fuzzy identification method and theoretical formulas to compute the actual size and installing positions parameters of a planar Four-Bar Mechanism, the synthesis of a planar Four-Bar motion generation Mechanism can be achieved using the established numerical atlas, fuzzy identification method and theoretical formulas.

  • Motion generation of spherical Four-Bar Mechanism using harmonic characteristic parameters
    Mechanism and Machine Theory, 2016
    Co-Authors: Jianwei Sun, Lu Chen, Jinkui Chu
    Abstract:

    Abstract In an earlier work, we presented a method to address the path generation problems associated with spherical Four-Bar Mechanism. In this paper, we seek to extend this approach to the synthesis of spherical Four-Bar linkages for motion generation. Through harmonic analysis, the output characteristics of a spherical Four-Bar Mechanism is observed to be dependent on the rigid body rotation angle operator μp(t). Subsequently, a database that contains 221,968 sets of basic rotation angle dimensional types for a spherical Four-Bar Mechanism was constructed. The theoretical formulas to calculate the actual dimension and installation parameters of spherical Four-Bar Mechanism are deduced from the harmonic parameters for position output and the harmonic parameters for the rigid body rotation angle operator. On the basis of the theoretical formulas and the numerical atlas database, the motion generation problem for a spherical Four-Bar Mechanism was solved. Finally, two examples are provided to demonstrate the validity of this method.

  • Dimensional Synthesis of Open Path Generator of Four-Bar Mechanisms Using the Haar Wavelet
    Journal of Mechanical Design, 2015
    Co-Authors: Jianwei Sun, Wenrui Liu, Jinkui Chu
    Abstract:

    This paper presents a synthesis method for the open path generation of a Four-Bar Mechanism using the Haar wavelet. The synthesis method utilizes the wavelet transform and normalization to extract the wavelet output feature parameters (WOFP) of the open path. Analysis of the WOFP reveals a particular characteristic: for the same Four-Bar Mechanism, not only do variations of the Mechanism origin and angles and the proportional scaling of the linkage lengths have no influence on the details of the WOFP but the same holds true for the position of the point that generates the coupler curve. Based on this finding, a numerical atlas database comprises 192,596 groups of basic dimensional types was established and a method of matching recognition was proposed as well. According to the internal relationship of the wavelet characteristic dimension parameters (WCDP), the actual Mechanism parameter values and position parameters of an objective Four-Bar Mechanism can be calculated. Four examples are presented to verify the accuracy and practicality of the proposed theory.

  • Synthesis of a non-integer periodic function generator of a Four-Bar Mechanism using a Haar wavelet
    Inverse Problems in Science and Engineering, 2015
    Co-Authors: Jianwei Sun, Wenrui Liu, Jinkui Chu
    Abstract:

    In this study, a synthesis method for a non-integer periodic function generator of a Four-Bar Mechanism using a Haar wavelet is presented. Using wavelet theory, the mathematical model for the output of a Four-Bar Mechanism is established. Next, the characteristics of the Four-Bar Mechanism output variable are described by the wavelet feature parameters; the relationship of the wavelet feature parameters between the output and its translation or dilation is also investigated. Based on this finding, three numerical atlas databases comprising of 203,500 groups of basic dimensional types of planar Four-Bar Mechanisms, 148,995 groups of basic dimensional types of spherical Four-Bar Mechanism and 11,175 groups of basic dimensional types of planar slider–crank Mechanism are compiled. According to the internal relationship between the wavelet feature parameters, the sizes of the objective Mechanism can be obtained using fuzzy recognition. Based on a genetic algorithm, optimization of the link parameters can be re...

  • Numerical atlas method for path generation of spherical Four-Bar Mechanism
    Mechanism and Machine Theory, 2010
    Co-Authors: Jinkui Chu, Jianwei Sun
    Abstract:

    In this paper, the relationship between the harmonic component of the coupler curves and the harmonic component of the rotation-angle function is discovered. Based on this finding, a numerical atlas database comprising of more than 6 million of basic dimensional types is built up. The formulas which can compute the position for coupler point, real size and installing dimensions of the spherical Four-Bar Mechanism are deduced. Based on those theoretical formulas and the numerical atlas database of the harmonic characteristic parameters, the problem of path synthesis of spherical Four-Bar Mechanism is solved. Finally, an example is given to show the feasibility of this approach.

Jon Juel Thomsen - One of the best experts on this subject based on the ideXlab platform.

  • kinematics of roller chain drives exact and approximate analysis
    Mechanism and Machine Theory, 2016
    Co-Authors: Niels Fuglede, Jon Juel Thomsen
    Abstract:

    Abstract An exact and approximate kinematic analysis of a roller chain drive modeled as a Four-Bar Mechanism is presented. The span connects the sprockets such that they rotate in the same direction, and the sprocket size, number of teeth, and shaft center distance can be arbitrary. The driven sprocket angular position, velocity and acceleration, as well as span length, are calculated and their (discontinuous) variation with driver angular position and main design parameters is illustrated. Kinematic predictions for the chain span motion are compared to results of multibody simulation, and there is seen to be very good agreement. All together this gives new insights into the characteristics of chain drive kinematics and the influence of main design parameters.

  • Kinematics of roller chain drives — Exact and approximate analysis
    Mechanism and Machine Theory, 2016
    Co-Authors: Niels Fuglede, Jon Juel Thomsen
    Abstract:

    Abstract An exact and approximate kinematic analysis of a roller chain drive modeled as a Four-Bar Mechanism is presented. The span connects the sprockets such that they rotate in the same direction, and the sprocket size, number of teeth, and shaft center distance can be arbitrary. The driven sprocket angular position, velocity and acceleration, as well as span length, are calculated and their (discontinuous) variation with driver angular position and main design parameters is illustrated. Kinematic predictions for the chain span motion are compared to results of multibody simulation, and there is seen to be very good agreement. All together this gives new insights into the characteristics of chain drive kinematics and the influence of main design parameters.

Murray E. Maitland - One of the best experts on this subject based on the ideXlab platform.

  • Crossed Four-Bar Mechanism for improved prosthetic grasp.
    Journal of rehabilitation research and development, 2009
    Co-Authors: Issa A. Ramirez, Craig P. Lusk, Rajiv Dubey, M. Jason Highsmith, Murray E. Maitland
    Abstract:

    INTRODUCTION Prosthetic hands (terminal devices) should be simple for persons with amputations to use and should contribute to their performance in grasping tasks. Different terminal devices are beneficial to activities of daily living (ADL) to varying degrees. Some terminal devices are specific to a narrow scope of applications, e.g., kayaking [1] or weight lifting [2], while others, like conventional hook terminal devices, can be used across a wide variety of activities. Like any tool, a terminal device might enhance performance in some situations but be neutral or detrimental in others. The purpose of this study was to measure the enhancement or detriment caused by the introduction of passive Four-Bar Mechanisms at the point of contact between a hook terminal device and a grasped object. DESCRIPTION OF Four-Bar Mechanism Normal anatomical human hands have a compliant surface on the fingers: the finger pulp that is the finger-object interface. The interface for typical hooks is a rigid, nonadaptive surface. In our prototype, we used a crossed Four-Bar linkage system as a rigid adaptive interface. The links are labeled [L.sub.1], [L.sub.2], [L.sub.3], and [L.sub.4] (Figure 1) and their respective lengths are given in Table 1. [L.sub.3], the grasp surface, was coated with a high-friction material. We analyzed the stability of the Four-Bar Mechanism by using the principle of virtual work in Ramirez et al. [3]. In this analysis, we found that the fingertip Mechanism adapts to the location and direction of the applied force, achieving a stable L3 orientation for a wide variety of contact points and loading directions through which the force might be applied, and that the stability of the link is indifferent to the magnitude of the force applied to it (assuming that the force does not damage/deform the Mechanism). [FIGURE 1 OMITTED] METHODS Subjects The study was a within-subject repeated-measures design. The protocol was approved by the University of South Florida Institutional Review Board. As in Lake [4], the subjects in our study did not have amputations; thus, they could complete the protocol under three different conditions: normal anatomical hand, hook prosthesis, and Four-Bar linkage prosthesis. The subjects' use of prosthetic hooks was accomplished by means of a pseudoprosthesis that allows subjects without amputations to open and close a prosthetic hand located just past their closed fist while wearing the same body-power harness worn by persons with amputations. In using subjects without amputations, we could avoid significant within-subject differences in upper-limb amputation level and function. The effect, studied by Lake, of a subject's previous experience with a specific terminal device could also be minimized [4]. For this research, 10 subjects (8 males and 2 females) between the ages of 18 and 25 were selected and proper informed consent was obtained. Personal history was collected from each person, including age at time of the assessment, race/ethnicity, and sex. The selected age interval was convenient in the university setting: a normative database has been established as the benchmark of normal hand function in that age range [5] and the age range reduces potentially significant variations within the group. A previous study has shown a slight increase in the time to complete the task with age [6]. Southampton Hand Assessment Procedure The Southampton Hand Assessment Procedure (SHAP) determines the effectiveness of a terminal device in grasp and manipulation by evaluating unilateral upper-limb performance. The SHAP consists of 26 timed tasks: 12 tasks involve grasping abstract objects such as spheres and prisms and 14 tasks simulate ADL. The tasks are performed by seated subjects in a standard order under the observation of an assessor, who records time to completion. The SHAP is designed to be a standardized and objective method of evaluating pathological hand function. …

Jia-yi Wang - One of the best experts on this subject based on the ideXlab platform.

  • A variational approach for the design of spatial Four-Bar Mechanism
    Mechanics of Structures and Machines, 1997
    Co-Authors: Hong-liu Zou, Karim Abdel-malek, Jia-yi Wang
    Abstract:

    ABSTRACT An analytical formulation for computing kinematic sensitivity of the spatial Four-Bar Mechanism is presented. The experimental code developed is used to compute an assembled configuration for the Mechanism that accounts for the effect of a design variation. The Mechanism is modeled using graph theory, in which a body is defined as a node and a kinematic joint is defined as an edge. The spherical joint is cut to convert the model into a tree structure by cutting an edge and introducing constraints. The effect of variation in Mechanism design using concepts of virtual displacement and rotation is introduced. The variation of the spherical constraint is computed, maintaining joint-attachment vectors and orientation matrices as variables. A system of equations that has a greater number of design variables than equations is then solved using the modified Moore-Penrose pseudo inverse. A recursive formulation is introduced, which can be used to obtain the state variation of a body in terms of the state ...

  • Kinematic Sensitivity Analysis of the Spatial Four-Bar Mechanism
    Volume 3: 22nd Design Automation Conference, 1996
    Co-Authors: Hong-liu Zou, Karim Abdel-malek, Jia-yi Wang
    Abstract:

    Abstract An analytical formulation for computing kinematic sensitivity of the spatial Four-Bar Mechanism is presented. The experimental code developed is used to compute an assembled configuration for the Mechanism due to a design variation. The Mechanism is modeled into a graph where a body is defined as a node and a kinematic joint is defined as an edge. The spherical joint is cut to convert the model into a spanning tree structure. Cutting an edge introduces the spherical constraint. The variation of this constraint is computed while maintaining the joint-attachment vectors and orientation matrices as variables. The variation of these variables determine the new kinematic design of the system. A recursive formulation is introduced to obtain the state variation of a body in terms of the state variation of a junction body and of the relative coordinates along the chain. The Jacobian matrix is then transformed from Cartesian coordinate space to joint coordinate space using velocity transformation matrices. Kinematic sensitivity analyses due to changing a joint-attachment vector and an orientation are presented.

Philip A. Voglewede - One of the best experts on this subject based on the ideXlab platform.

  • Mechanical Redesign of a Transtibial Prosthesis With Active and Passive Components and a Four-Bar Mechanism
    Volume 10: 44th Mechanisms and Robotics Conference (MR), 2020
    Co-Authors: Devon K. Plata, Jessica B. Thayer, Philip A. Voglewede
    Abstract:

    Abstract This paper proposes a redesign of a Four-Bar Mechanism for an active transtibial prosthesis created by Bergelin 2010 and modified by Klein 2009. Bergelin utilized a Four-Bar Mechanism, motor, and spring to match the prosthesis ankle moments to the ankle moments of a healthy ankle. Bergelin’s prosthesis did succeed in matching ankle moments closely, but with excessive motor energy expenditure when the prosthesis was in a neutral position. Klein proposed a redesign of the Mechanism to change the motor-spring connection from parallel to series to eliminate the energy requirement when the device is in neutral position, which allowed for the application of impedance control of Mechanism. This paper proposes a reoptimization of the series motor-spring Mechanism configuration proposed by Klein, which further reduces the energy input configuration of the active prosthesis.

  • Synthesis of a Reconfigurable Four-Bar Mechanism with Variable Joints
    Volume 5A: 38th Mechanisms and Robotics Conference, 2014
    Co-Authors: Brian J. Slaboch, Philip A. Voglewede
    Abstract:

    This article introduces a reconfigurable Four-Bar Mechanism. The Mechanism uses a rotational-translational variable joint to switch between a RRRR Four-Bar and a RRRP1 Four-Bar. The ability to transition between two types of Four-Bar Mechanisms allows the reconfigurable Four-Bar Mechanism to complete a rigid body guidance task not possible by either a RRRR Four-Bar Mechanism or a RRRP Four-Bar Mechanism. The reconfigurable Mechanism reduces the number of required actuators in the Mechanism.Copyright © 2014 by ASME

  • Design of an Active Ankle-Foot Prosthesis Utilizing a Four-Bar Mechanism
    Journal of Mechanical Design, 2012
    Co-Authors: Bryan J. Bergelin, Philip A. Voglewede
    Abstract:

    This article discusses the design and testing of a powered ankle prosthesis. This new prosthesis mimics nonamputee (normal) ankle moments during the stance phase of gait through the use of an optimized spring loaded Four-Bar Mechanism. A prototype prosthesis based on the optimization was designed, fabricated, and tested. The experimental results achieved 93.3% of the simulated theoretical ankle moment giving substantial evidence that this approach is a viable in designing powered ankle prostheses.

  • Design for Improved Trans-Tibial Prosthetic Devices Using Four Bar Mechanisms
    Volume 7: 29th Mechanisms and Robotics Conference Parts A and B, 2005
    Co-Authors: Joseph G. Wells, Philip A. Voglewede, David N. Rocheleau
    Abstract:

    Currently available prosthetic devices for trans-tibial (below the knee) amputees allow a great deal of mobility, but they do not allow amputees to walk with a normal gait. Most designs utilize passive elements to approximate the complex nonlinear response of the foot and ankle. This paper outlines early work in the design of a hybrid passive/active prosthesis that uses the inherent nonlinearity of a four bar Mechanism and the power of numerical optimization to more closely duplicate the function of the human foot/ankle complex during walking.