The design of multi-fingered robotic hands can follow a kinematic synthesis approach, in which a trajectory or set of points and higher derivatives are defined for each fingertip. The output of the dimensional synthesis is a set of joint axes, effectively defining the basic kinematic structure and the motion of the hand. In the case of spatial motion, there seems to be a big gap between the results of the dimensional synthesis and a real and effective detailed design of the robotic hand, this being one of the reasons why synthesis is not regularly used in the design of robotic hands.
This work aims to reduce the gap from kinematic synthesis to detailed, computer-aided design of robotic hands. In order to do so, the output of the dimensional synthesis is first used as the input of a link-based optimization process, aiming to bring to reasonable values requirements such as link lengths, internal friction forces and obstacle avoidance, including self-intersection. The optimized results are automatically imported to a popular solid modeling software (SolidWorks), creating reference geometry for parts, and joint axes and anchor points for the final hand assembly. At the same time, a database of hand parts is presented to the user to select and adapt in order to create an automatic, realistic assembly of the robotic hand.
The output of the process is a first detailed design of the robotic hand, which can be a good starting point for the designer to implement transmission and actuation in further stages.
How it works
The figures show the design process for a 1-(3,3,3) hand, with one joint at the wrist and three fingers. The initial output from the kinematic solver ArtTreeKS, where wireframe links connect the axes at the common normal lines, is shown first. In the macro, the hand topology and the type of parts of the library are selected. The macro takes a CSV file with points on the axes and automatically draws the joints at the reference configuration. The selected parts are imported and mated to obtain the output of the automatic CAD hand drawing process, which is a fully assembled, movable solid model of the hand.
Output from ArtTreeKS solver.
Link-based optimization to find optimal anchoring
points on axes.
Run CAD software macro.
Points required by the macro are indicated.
SolidWorks macro windows.
The joint axes are drawn in the solid modeling software, with anchoring points on each axis.
Library parts are imported, fitted to joint axes and assembled for the final design.
The draft paper below contains the summary of the method and was used as base for the paper presented at the IDETC 2015 conference.
Draft: A Design Implementation Process for Robotic Hand Synthesis
Implementation: This SolidWorks macro is to be used in conjunction with the library of parts and an excel file containing the points of the axes. An example excel file is provided here .
The link anchoring points can be manually selected or they can be optimized using for instance our link-based optimization technique. The following Mathematica file can be used to create the Matlab functions to optimize those points.
Or you can watch the video tutorial below for information on the automatic process.
More information: Visit PhD candidate Neda Hassanzadeh webpage.