Alba Perez Gracia - Research


Links to related research


Screw system for RPRP linkage


Workspace of RPRP linkage

Exact kinematic synthesis for workspaces

For those linkages whose workspace can be expressed as a linear system, it is easy to span the whole workspace by using a set of generators. Performing finite-position kinematic synthesis using these generators allows for the complete description of the workspace as the input for the synthesis process.
This method has been applied to the RPRP overconstrained linkage. Its application to the RCCR linkage is being explored.
Some information about this project:
- Perez-Gracia, A., "Synthesis of Spatial RPRP Closed Linkages for a Given Screw System", ASME Journal of Mechanisms and Robotics, 2011.
- Create the workspace of screws corresponding to relative displacements and perform the dimensional synthesis.


A 3-(2,2,2) tree chain


Multifingered 3-(2,2,2) hand
for a door-opening task

Kinematic Synthesis of Tree-like Articulated Chains

Articulated systems with a tree structure appear naturally when grasping and manipulation are involved; the best example are multi-fingered robotic hands. We are developing a synthesis theory for these kinematic chains. New issues and results appear when dealing with them. For instance, we can do exact synthesis for serial chains with more than six joints.
This method is being developed with Edgar Simo-Serra at the IRI Robotics Institute in Barcelona, Spain.
Some information about this project:
- Simo-Serra, E., Moreno-Noguer, F. and Perez-Gracia, A., "Design of Non-anthropomorphic Robotic Hands for Anthropomorphic Tasks", ASME IDETC/CIE 2011 Conference, 2011.


Smart Hand Prosthesis,
Prototype II

Smart Prosthetic Hand Project

The Smart Prosthetic Hand is a multi-disciplinary project with researchers from the School of Engineering, the Department of Physical Therapy and the College of Pharmacy at Idaho State University.
The aim is to develop a highly functional prosthetic hand driven by EMG signals.
The robotics team has been developing the prototype prosthetic hand and the method to capture and analyze hand motion. Some information about this project:
- Crawford, A.L. and Perez-Gracia, A., "Design of a Robotic Hand with a Biologically-Inspired Parallel Actuation System for Prosthetic Applications", Proc. of the ASME 2010 IDETC/CIE Conferences, Montreal, Quebec, Canada, August 15-18, 2010.


Finger exoskeleton, ICORR


Thumb and selected exoskeleton linkage
trajectory comparison

Design of a Finger Rehabilitation Device

I am collaborating with Eric Wolbrecth at University of Idaho and David Reinkensmeyer at University of California, Irvine in the development of an exoskeleton for finger-thumb rehabilitation.
There is an adaptable prototype for the finger motion, the thumb exoskeleton is under development. Some information about this project:
- Wolbrecht, E.T., Reinkensmeyer, D.J., and Perez-Gracia, A., "Single Degree-of-Freedom Exoskeleton Mechanism Design for Finger and Thumb Rehabilitation", Proceedings of the ICORR 2011, Zurich, Switzerland, June 29-July 1, 2011.


See a Bennett's net


Mathematica animation of a heterogeneous network mechanism by RaNae Isaak (QuickTime, big)

Network mechanisms

Network mechanisms with one degree of freedom can be created using parallel overconstrained spatial and planar linkages. In particular, we have studied the simplest closed linkage, composed of four revolute joints, which is movable only in three particular cases: planar four-bar linkage, spherical four-bar linkage and Bennett linkage. We have created some movable structures using a homogeneous network of Bennett linkages and heterogeneous networks of both Bennett and planar four-bar linkages.

Some information about this project:
- Isaak, R., "A Study of Overconstrained Linkage Networks", Master's Thesis, College of Engineering, Idaho State University, June, 2006.
- Construct and visualize a Bennett's linkage.

These results are for a simplified definition of a human skeleton consisting of five serial chains with revolute and spherical joints.

Kinematic identification of structures from visual data

- We applied the dual quaternion synthesis theory to identify the kinematic structure underlying moving images. Graphic data from human subjects can be used to identify the kinematic skeleton. This may be used to create a 3d movable avatar representing the subject. This research was developed as a main researcher by Mari Cruz Villa Uriol, at the Department of Electrical Engineering and Computer Science at the University of California, Irvine.

- Current research project in the same direction involves the identification of human hand motion

Implementation in Synthetica1.0 of the dual quaternion synthesis for the RPC robot (Main developer of the Synthetica software: Hai Jun Su).

Dual quaternion synthesis of constrained serial robots

- The following Mathematica notebooks can be adapted to design any serial robot with less than six degrees of freedom. These are the results of the research developed in my dissertation. I include here several examples.
Spatial RR Robot,
Spatial RPP Robot,
Spatial RRP Robot,
Spatial RRRR Robot

- I developed a general solver (Java) for the finite-position dimensional synthesis of serial robots with up to five joints and up to ten degrees of freedom.

- We added this solver to Synthetica 2.0. Go to the Synthetica webpage to download the latest version of Synthetica, which can be used in Mac, Unix and Windos O.S. Synthetica was developed at the Robotics Lab of the Univ. of California, Irvine. Contact also Hai Jun Su, at Iowa State University, for questions or comments about Synthetica.