Introduction
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Reference trajectories for walking robots
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(C. Chevallereau, Y. Aoustin, A. Formal'sky, D. Tlalolini Romero)
For walking robots, the evolution for each of the joint during the
walking is not unique for a given gait. A largely used criterion to define a reference
trajectory is to try to minimise the energy used for cyclic walking of the robot.
The definition of the reference trajectory is important for the design of the walking
robot, the choice of the actuators and the definition of the control law. This aim can
be achieved by at least two different strategies :
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By optimisation techniques (as LSIIT Strasbourg, LAG in France, in Germany and
United States),
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By the studying of ballistic motion (as LMS Poitiers, INRIA Sophia-antipolis
and Grenoble in France, or Mc Geer, Mc Mahon, Formal'sky ... abroad).
In the framework of the first strategy, we have studied walking
and running motion of biped; motion of quadruped with synchronous motion of two legs
: "bound", "amble" and "trot" gaits, these gaits can include flight phases or not.
A joint motion is defined by polynomial function of the time, and the coefficients
of the polynomial function are defined to minimise the energy for periodical motion.
Classical optimisation is used and some constraints as the actuator limits are taken
into account. The under actuated phase which appears in the gait are taken into account.
Start and stop motion and introduction of double support phase for biped motion
are in progress.
In the framework of the second strategy, after the definition of
ballistic motion for "bound", "amble" and "trot" gait of quadruped, current studies
are devoted to the running of biped with instantaneous or non instantaneous single
support phase. A decoupled model of the joint variable and mass centre position have
been introduced, the ballistic motion is easier to obtain. For the robots studied,
convenient ballistic motions exist but cyclic motion on horizontal ground can not
be achieved without impulsive torque. When the robot has a surface contact with the
ground (complete sole on the ground) a strategy is proposed to define reference
trajectory partially ballistic and corresponding to finite torque pour walking
and running.
Moreover, for the under-actuated phase of the walking gait,
we have studied reference trajectories such that a desired final configuration
is achieved in spite of disturbance.
Main publications of the topic
Control of walking robots
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