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Open Access Publications from the University of California

Scholarly Works (6 results)

  • Article
  • Peer Reviewed
UC Irvine Previously Published Works (2015)
This paper presents a design system for planar and spherical six-bar linkages, which is integrated with a solid modeler. The user specifies a backbone 3R chain in five task configurations in the sketch mode of the solid modeler and executes the design system. Two RR constraints are computed, which constrain the 3R chain to a single degree-of-freedom six-bar linkage. There are six ways that these constraints can be added to the 3R serial chain to yield as many as 63 different linkages in case of planar six-bar linkages and 165 in case of spherical six-bar linkages. The performance of each candidate is analyzed, and those that meet the required task are presented to the designer for selection. The design algorithm is run iteratively with random variations applied to the task configurations within user-specified tolerance zones, to increase the number of candidate designs. The output is a solid model of the six-bar linkage. Examples are presented, which demonstrate the effectiveness of this strategy for both planar and spherical linkages.
    Cover page: A Design System for Six-Bar Linkages Integrated With a Solid Modeler
    • Article
    • Peer Reviewed
    UC Irvine Previously Published Works (2014)
    This paper formulates a methodology for designing planar eight-bar linkages for five task positions, by adding two RR constraints to a user specified 6R loop. It is known that there are 32 ways in which these constraints can be added, to yield as many as 340 different linkages. The methodology uses a random search within the tolerance zones around the task specifications to increase the number of candidate linkages. These linkages are analyzed using the Dixon determinant approach, to find all possible linkage configurations over the range of motion. These configuration trajectories are sorted into branches. Linkages that have all the five task configurations on one branch, ensure their smooth movement through the five task positions. The result is an array of branch-free useful eight-bar linkage designs. An example is provided to illustrate the results.
      Cover page: Synthesis of Useful Eight-Bar Linkages as Constrained 6R Loops
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2016)
      This paper explores an automated methodology to design eight-bar linkages for five positions, by constraining the user defined 4R open chain and 6R closed chain using RR dyads. The application in focus is that of rectilinear motion. The paper lays down the rules for systematic selection of link pairs for the application of RR constraints, that help automate the synthesis of eight-bar linkages. The methodology performs a random search within the user specified tolerance zones around the task specifications to increase the number of candidate linkage solutions. These linkages are then subjected to forward kinematic analysis using the Dixon determinant elimination procedure to find all possible linkage configurations over the range of motion of the input link. Linkages that have all the task configurations on one branch ensure their smooth movement through them. The result is an array of defect-free eight-bars that can perform approximate rectilinear motion. This method provides increased flexibility and control over the synthesized linkage compared to other known rectilinear motion linkages, owing to the ability to specify the backbone chain. A couple of examples are presented to illustrate the results.
        Cover page: DESIGN OF EIGHT-BAR LINKAGES WITH AN APPLICATION TO RECTILINEAR MOTION
        • Article
        • Peer Reviewed
        UC Irvine Previously Published Works (2016)
        This paper presents a design system for planar eight-bar linkages that adds three RR constraints to a user-specified 4R serial chain. R denotes a revolute, or hinged, joint. There are 100 ways in which these constraints can be added to yield as many as 3951 different linkages. An analysis routine based on the Dixon determinant evaluates the performance of each linkage candidate and determines the feasible designs that reach the task positions in a single assembly. A random search within the user-specified tolerance zones around the task specifications is iterated in order to increase the number of linkage candidates and feasible designs. The methodology is demonstrated with the design of rectilinear eight-bar linkages that guide an end-effector through five parallel positions along a straight line.
          Cover page: A Design System for Eight-Bar Linkages as Constrained 4R Serial Chains
          • Thesis
          • Peer Reviewed
          UC Irvine Electronic Theses and Dissertations (2015)

          This dissertation describes research into an automated methodology for designing eight-bar linkage systems for specialized tasks. The user specifies the desired motion as five discrete task positions, and a backbone chain robot that can achieve those task positions. The design algorithm then uses the graph theory approach to find all the different ways of constraining the robot using mechanical constraints, which are rigid binary links (RR constraints), to generate single degree of freedom linkages.

          Linkage solutions synthesized using this method are only guaranteed to reach the five positions. They can exhibit branch defects which results in discontinuities during their motion in between the task positions. An analysis algorithm is used to discard the defective solutions and ensure that the filtered solutions will move the end-effector smoothly through all the five desired task positions. Once the original task positions are explored for finding linkage solutions, the design system runs the algorithm iteratively over randomized task positions, within acceptable variations provided by the user. This results in the generation of large number of defect-free linkage solutions. These solutions are further checked for a minimum and maximum allowed link length criteria to further filter out linkages. The result is a list of successful linkage solutions that are presented to the user.

          The RR constraining strategy for the user specified robot has provided some useful insights in to linkage design. It has been observed that as we increase the complexity of the starting serial or closed chain robot, the number of linkage solutions that could be synthesized increases rapidly. This increases the probability of finding useful solutions and hence more design options can be presented to the designer for selection. The design system has been implemented in a computer aided linkage software system called MechGen for four-bar and six-bar linkages, and has demonstrated its effectiveness to design better devices for several applications.

            Cover page: Computer Aided Design of Eight-bar LinkagesCreative Commons 'BY-NC-SA' version 4.0 license
            • Article
            • Peer Reviewed
            UC Irvine Previously Published Works (2013)
            This paper presents a software system for the kinematic synthesis of useful spherical Watt I six-bar linkages that can guide a body through five task positions. The design procedure begins with the specification of a spherical 3R open chain that reaches five specified task positions. The six-bar linkage is designed by constraining the 3R spherical chain to the topology of a Watt I spherical six-bar linkage. The CAD software SolidWorks is used to specify the 3R chain and the five spherical task positions. We describe the SolidWorks Add-In MechGen that reads the Solid- Works data and generates candidate linkages. Included in the task specification are tolerance zones that allow random adjustments to the task positions to search for defect-free linkages. An example is provided that demonstrates the five position synthesis of a useful spherical Watt I six-bar linkage. Copyright © 2013 by ASME.
              Cover page: Computer Aided Design of Useful Spherical Watt I Six-Bar Linkages
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