11,050 research outputs found
Éloge de la naïveté
No full textMerlet Pierre. Éloge de la naïveté. In: Autres Temps. Les cahiers du christianisme social. N°1, 1984. pp. 45-47
F. Merlet, Seigneur des Pyrénées, l'ours
No full textPéchoux Pierre-Yves. F. Merlet, Seigneur des Pyrénées, l'ours. In: Revue géographique des Pyrénées et du Sud-Ouest, tome 43, fascicule 2, 1972. Actes du premier colloque sur la science du paysage. p. 292
Correspondance
No full textMerlet Pierre, Grojeanne Paul, Minot Clémence. Correspondance. In: Autres Temps. Les cahiers du christianisme social. N°20, 1988. pp. 78-79
Correspondance
No full textMerlet Pierre, Grojeanne Paul, Minot Clémence. Correspondance. In: Autres Temps. Les cahiers du christianisme social. N°20, 1988. pp. 78-79
Jean-Pierre Merlet
No full textthis paper we consider the problem of trajectory verification for a classical GoughStewart platform i.e. we want to verify if a given trajectory obeys various criteria which define its validity, for example that the trajectory lies fully inside the workspace of the robot and is singularity-free. We propose an almost real-time method that may deal with almost any trajectory and any validity criterion and can manage uncertainties on the specified trajectory, for example to take into account control error
On the accuracy of wire-driven parallel robots
No full textA wire-driven parallel robot is a robot for which all the
wires are connected at the same point of the platform, allowing to
control the location of this point. We are
interested in the positioning accuracy of such a robot. If the wires
are not elastic we show that the influence on the accuracy of the co-location
errors of the
wire anchor points on the platform is moderate, although
a full analysis is a very difficult task. If the wires
are elastic we study the influence of the
the wire lengths measurement errors and inaccurate
estimation of the stiffness of the wires. Again we show a
moderate influence but very large changes in the tensions in the
wires that probably prohibit the use of the redundancy to optimize the
tension in the wires.
In all cases the complexity of the forward kinematics of such a robot
makes accuracy analysis a very demanding task that requires an in-depth
investigation
Further analysis of the 2-2 wire-driven parallel crane
No full textThe 2-2 wire-driven parallel crane is the most simple planar parallel crane
actuated by wires with two wires connected at two different points on
the platform. We present original contributions on the kinematics of
such robot, namely full inverse kinematics,
trajectory, static and singularity analysis in the joint
space
The kinematics of the redundant wire driven parallel robot
No full textWe address the kinematics of the redundant wire-driven parallel
robot, i.e. a robot with wires connected at the same point on the
platform. The redundancy allows one to increase the workspace
size. But we show, both theoretically and experimentally that if the
wires are not elastic, then the redundancy cannot be used to control
the wire tensions. Indeed we show that whatever are the number of
wires there will always be only at most 3 wires in tension, while the oth
er
wires will be slack. We then show that if the wires are elastic,
then the platform positioning will be very sensitive to stiffness
identification and wire lengths control. Hence classical redundant
control schemes are difficult to use for such robot and alternate use of
the
geometry of redundant wires have to be considered
Comparison of actuation schemes for wire-driven parallel robots
No full textThere are two main systems that can be used to coil and uncoil the
wires of a wire-driven parallel robots: a rotary motor that turns a
drum on which the wire is coiled or a linear motor with a pulley
system. The rotary category may be divided into two sub-categories:
the system with a spiral guide for the coiling, allowing only layer
for the wire and the system without guide, that allows for several
wire layers with the drawback that the amount of coiled wire for one
motor turn depends upon the number of layer. All three systems are
compared in terms of accuracy and compacit
Homokinetic Transmission of Rotational Motion via Constant-Velocity Joints in Closed-Chain Wrists
No full textThis paper investigates how the motion of a rotating body can be actuated by frame-located motors via homokinetic transmissions based on constant-velocity joints. The general functioning of such joints is surveyed and their application to the set forth problem is examined. It is shown that their incautious use may lead to unworkable designs, while some viable solutions, leading to innovative two- and three-degrees-of-freedom closed-chain wrists, are presented
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