Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Rigid vs compliant contact: An experimental study on biped walking   Contact modeling plays a central role in motion planning, simulation, and
control of legged robots, as legged locomotion is realized through contact. The
two prevailing approaches to model the contact consider rigid and compliant
premise at interaction ports. Contrary to the dynamics model of legged systems
with rigid contact (without impact) which is straightforward to develop, there
is no consensus among researchers to employ a standard compliant contact model.
Our main goal in this paper is to study the dynamics model structure of bipedal
walking systems with a rigid contact and a \textit{novel} compliant contact
model and to present experimental validation of both models. For the model with
rigid contact, after developing the model of the articulated bodies in flight
phase without any contact with the environment, we apply the holonomic
constraints at contact points and develop a constrained dynamics model of the
robot in both single and double support phases. For the model with compliant
contact, we propose a novel nonlinear contact model and simulate the motion of
the robot using this model. In order to show the performance of the developed
models, we compare obtained results from these models to the empirical
measurements from bipedal walking of the human-sized humanoid robot SURENA III,
which has been designed and fabricated at CAST, University of Tehran. This
analysis shows the merit of both models in estimating dynamic behavior of the
robot walking on a semi-rigid surface. The model with rigid contact, which is
less complex and independent of the physical properties of the contacting
bodies, can be employed for model-based motion optimization, analysis as well
as control, while the model with compliant contact and more complexity is
suitable for more realistic simulation scenarios.

20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th