Jean-Paul Lallemand

The 6-Dof 2-Delta parallel robot

In this paper, we will present a new 6-DOF parallel robot using a set of two Delta structures. An effective method is proposed to establish explicit relationships between the end effector co-ordinates and the active and passive joint variables. A simulation of the 2-Delta robot on a C.A.D. Robotics system will also be presented. This simulation will allow us to validate the cohesion of our calculations, and to show the workspace depending on the mechanical limits on passive joints variables. Finally, an approach is proposed to study the influence of small clearances of the passive joint on the precision of the position and rotation of the effector. This approach is based on a concept similar to that of Yoshikawas manipulability.

A new insight into the duality between serial and parallel non-redundant and redundant manipulators

This paper describes detailed velocity kinematics and the statics of serial and parallel robots. Without resorting to the screw theory, the duality between these two types of robots is demonstrated. This duality concerns operational speeds of serial robots and operational forces of parallel robots, as well as internal speeds in redundant serial robots and internal forces in redundant parallel robots. This approach allows a deeper understanding of the duality between these two types of robots, particularly when they are redundant.

Separation of isochromatics and isopachics using a Faraday rotator in dynamic-holographic photoelasticity

A method is presented that allows the simultaneous separation of isochromatic- and isopachic-fringe patterns for transient-plane stress problems. Isopachic fringes are obtained by means of holography with a Faraday cell and a pulsed ruby laser flashing dual pulses. As usual isochromatic whole-order fringes are recorded in a circular-light polariscope. The shock generator (air-gun) and its synchronizing system with the ruby laser is described. The procedure is applied to the recording of the isochromatic- and isopachic-fringe patterns in a disk under radial dynamic loads.

Synchronization problems in dynamic holographic photoelasticity

An analysis of synchronization problems encountered when recording transient-fringe patterns which are dependent on the light source and the method of shock generation is presented. The analysis is specifically designed to be valid on a photoelastic material having either a high or low Youngs modulus when the shock generator is an air gun and the light source is a Q-switched ruby laser. Synchronization is performed using integrated circuits in T.T.L. logic which give a triggering order to the ruby laser under the control of the projectile velocity.

A peculiar flip-flop actuator for an in-pipe microrobot

The work presented here concerns the design and manufacturing possibility of a polymodular autonomous microrobot moving like an earthworm. The study consists of the development of a new locomotion actuator based on shape memory alloys. This actuator is formed by a flexible frame forced in post-buckling by its assembly on a rigid skeleton cage. This mechanical structure, forming a knot in the microrobot chain, uses its two post-buckling equilibrium positions to achieve first the support and second the local lengthening enabling the movement of the microrobot. Initially, we present the technical solution designed for the locomotion actuator and the mechanical characterization of its malleable structure. Then, we present the instrumentation by educated SMA of a malleable structure and the capability of microrobot locomotion task in a vertical tube.