Project : coprin
Section: New Results
Keywords : wires robot, static analysis, kinematic analysis, interval analysis, parallel robot.
Parallel wires robots
We intend to build a wire robot that will be used as a force-feedback haptic device for the workbench of the research unit. Although several wires robots have been developed in many laboratories we have the following objectives:
mechanical design: the wire actuation system should be designed to allow for fast and easy changes in the geometry of the robot, precise evaluation of the wire lengths (for an optimal measurement of the platform location) and of the force applied at the end-effector level
modularity: the performances of a parallel robot are very sensitive to the geometry of the robot. We intend to develop algorithms allowing to determine the optimal geometry (i.e. location of the actuation system) being given the task requirements. For that purpose it is necessary to better understand the specificities of wire robots and we have already addressed the workspace problem 
Keywords : optimal design, wires robot.
Workspace is an important task criteria and a design strategy must address this performance index. Compared to classical parallel robot the workspace of wires parallel robot is deeply influenced by the additional constraints that the wire tension must be positive (to avoid slack wires) and lower than a pre-defined threshold. The relationship between the wrench applied on the end-effector, the location X of the end-effector, the wires tension and the kinematics parameters defines an under-constrained system of equations that is linear in the wires tension and in the end-effector wrench. We have applied interval analysis methods to determine an approximation of the allowed region for the end-effector such that, being given the wrench , the wires tension satisfied the tension constraints. This approximation is constituted of a list of possible ranges for X, that allows the design of an efficient trajectory verifier/planner.
Mechanical design of a modular parallel wires robot
Keywords : wires robot, mechanical design, modularity, parallel robot.
Our work has focused on the mechanical design of a modular wires robot which should allow:
to change easily the location of the attachment points of the wires for adapting the robot's performances (workspace, accuracy, ...) to the task at hand
to drive and control the end-effector with a very good accuracy
to allow for the measurement of the forces/torques applied on the end-effector
to minimize the influence of internal and external disturbances on the positioning of the end-effector
Our design is based on independent reconfigurable driving modules that include electrical motor, modular hoist, elastic element, and tension sensor.