Abstract: Dynamic
and agile locomotion performed by legged animals demonstrates a feasible but still very challenging style of locomotion to be exhibited on
artificial legged platforms. How animals evolved to their present
forms and how they coordinate their high degree-of-freedom (DOF)
active/passive joints for dynamic maneuver are still puzzles to be
explored. Here, with the goal of exciting dynamic behaviors
on empirical robots, we at Bio-inspired Robotics Laboratory, National
Taiwan University, would like to address this problem by exploring
simple reduced-order dynamic models and linking their behaviors to these
of the complex robot platforms.
Two
types of robots will be introduced in this talk. One is the leg-wheel
transformable robot. It is implemented with a unique leg-wheel
transformation mechanism that directly switches the morphology of
the driving mechanism between wheels (i.e., a full circle) and 2-DOF
leg (i.e., combining two half circles as a leg), so that the same
actuation system can be efficiently utilized in both wheeled and legged
modes. The robot is also implemented with coupled oscillators, which
act as the main mechanism to coordinate four leg-wheel motions for
leg-wheel transformation as well as generation and transition of the
legged gaits. The robot can be regarded as having “leg-level” dynamics.
The other
robot introduced in this talk is the well-known RHex-style robot, where
several new reduced-order models are constructed to excite the “gait level”
dynamics on the robot. A simple reduced-order model, the
rolling spring-loaded inverted pendulum (R-SLIP), is developed and
served as the running template of the RHex-style robot. Experimental
validation confirms that by merely deploying stable running gaits of
the R-SLIP model on the physical robot with a simple open-loop
control strategy, the robot can easily initiate its dynamic
running behaviors with a flight phase and can move with similar body
state profiles to those of the model, in all five speeds that were tested.
By using the same methodology, a two-leg sagittal-plane model is
constructed that serves as the fundamental multi-leg gait-level template.
It successfully excites the bounding and pronking behaviors of the “quadruped
version” of the RHex-style robot. In addition to these two
models, two three-leg planar models are also constructed to develop
leaping behavior and climbing behavior of the RHex-style
robot, respectively.