3,037 research outputs found
Designing a parallel manipulator for a specific workspace
We present an algorithm to determine all the possible geometries of Gough-type 6 D.O.F. parallel manipulators whose workspace has to include a desired workspace. This desired workspace is described by a set of geometric objects, limited here to points, segments and spheres, describing the location of the center of the moving platform, the orientation of the platform being kept constant for each given object. This algorithm takes into account the leg length limits, the mechanical limits on the passive joints and interference between links
Workspace Analysis of the Parallel Module of the VERNE Machine
The paper addresses geometric aspects of a spatial three-degree-of-freedom
parallel module, which is the parallel module of a hybrid serial-parallel
5-axis machine tool. This parallel module consists of a moving platform that is
connected to a fixed base by three non-identical legs. Each leg is made up of
one prismatic and two pairs of spherical joint, which are connected in a way
that the combined effects of the three legs lead to an over-constrained
mechanism with complex motion. This motion is defined as a simultaneous
combination of rotation and translation. A method for computing the complete
workspace of the VERNE parallel module for various tool lengths is presented.
An algorithm describing this method is also introduced
A new methodology for designing PID controllers
It is known that it is impossible to select fixed gains for a PD controller that will critically damp the response to disturbances for all configurations of a given robot system. Because of this the potential for overshoot is always present and cannot be avoided unless the system is severely overdamped. This is not necessarily a practical solution and can be an economically unacceptable approach. On the other hand, however, if overshoot is permissible to some degree for some systems in the case of conventional Serial robots it is still prohibited in the case of Parallel robots as it may easily bring the robot to one of its possible singular configurations, causing damage to the system. This paper introduces a new algorithm for the design of PD controllers that ensures uniform and fast dynamic responses, which are free from overshoots for all robot configurations. The technique also satisfies general stability requirements for the system
Non-singular assembly mode changing trajectories in the workspace for the 3-RPS parallel robot
Having non-singular assembly modes changing trajectories for the 3-RPS
parallel robot is a well-known feature. The only known solution for defining
such trajectory is to encircle a cusp point in the joint space. In this paper,
the aspects and the characteristic surfaces are computed for each operation
mode to define the uniqueness of the domains. Thus, we can easily see in the
workspace that at least three assembly modes can be reached for each operation
mode. To validate this property, the mathematical analysis of the determinant
of the Jacobian is done. The image of these trajectories in the joint space is
depicted with the curves associated with the cusp points
Miniaturized modular manipulator design for high precision assembly and manipulation tasks
In this paper, design and control issues for the development of miniaturized manipulators which are aimed to be used in high precision assembly and manipulation tasks are presented. The developed manipulators are size adapted devices, miniaturized versions of conventional robots based on well-known kinematic structures. 3 degrees of freedom (DOF) delta robot and a 2 DOF pantograph mechanism enhanced with a rotational axis at the tip and a Z axis actuating the whole mechanism are given as examples of study. These parallel mechanisms are designed and developed to be used in modular assembly systems for the realization of high precision assembly and manipulation tasks. In that sense, modularity is addressed as an important design consideration. The design procedures are given in details in order to provide solutions for miniaturization and experimental results are given to show the achieved performances
Reuleaux: Robot Base Placement by Reachability Analysis
Before beginning any robot task, users must position the robot's base, a task
that now depends entirely on user intuition. While slight perturbation is
tolerable for robots with moveable bases, correcting the problem is imperative
for fixed-base robots if some essential task sections are out of reach. For
mobile manipulation robots, it is necessary to decide on a specific base
position before beginning manipulation tasks.
This paper presents Reuleaux, an open source library for robot reachability
analyses and base placement. It reduces the amount of extra repositioning and
removes the manual work of identifying potential base locations. Based on the
reachability map, base placement locations of a whole robot or only the arm can
be efficiently determined. This can be applied to both statically mounted
robots, where position of the robot and work piece ensure the maximum amount of
work performed, and to mobile robots, where the maximum amount of workable area
can be reached. Solutions are not limited only to vertically constrained
placement, since complicated robotics tasks require the base to be placed at
unique poses based on task demand.
All Reuleaux library methods were tested on different robots of different
specifications and evaluated for tasks in simulation and real world
environment. Evaluation results indicate that Reuleaux had significantly
improved performance than prior existing methods in terms of time-efficiency
and range of applicability.Comment: Submitted to International Conference of Robotic Computing 201
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