Robustness, Control, and Contact-based Mechanics in Robotics

Tan Chen
Postdoctoral Research Associate
University of Illinois Urbana-Champaign
Professor Dejan Milutinovic

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Description:  Locomotion and manipulation are complementary robotic applications related through their shared
goal of controlling physical interaction with an environment. This work focuses on robustness,
control, and contact-based mechanics in these two fields. In biped locomotion, the robustness of
underactuated bipeds is limited because the underactuation indicates less control authority. This
talk presents a nonlinear mechanical coupling metric for quantifying the robustness of
underactuated bipeds and guiding robust biped design. An important problem in unstructured
natural environments is system stability for locomotion on slippery surfaces. This is an open
problem requiring switching events among different control modes and system states during slip,
and the contact between foot and ground must be modeled explicitly. In simulations modeling
contact-based mechanics and control, this works finds small step length, moderate gait speed, and
swing-leg retraction before touch-down improve robustness for a biped introduced to a slippery
surface. Similarly, the manipulation problem lives in a contact-rich environment where noise in
pose estimates and kinematic models create additional uncertainty. This talk also presents some
recent results from a current ongoing project on robotic manipulation for assembly, with more focus
on experiments and industrial application. Due to difficulty in analytically modeling such contact
at assembly, this work applies machine learning on the force/torque contact data to improve the
assembly. In addition, calibration with data post-processing and synthetic vision data are applied
to achieve improved robustness for this industrial robotic assembly application.

Speakers Bio:  Dr. Tan Chen is a Postdoctoral Research Associate affiliated with the Coordinated Science
Laboratory at the University of Illinois Urbana-Champaign. He received his PhD degree in
Aerospace and Mechanical Engineering from the University of Notre Dame. Prior to that, he
received his BS degree in Mechanical Engineering from Shanghai Jiao Tong University (SJTU),
China, and a joint MS degree from SJTU and École des Mines de Douai, France. He was an Eiffel
Scholarship recipient in France and received the outstanding graduate student teaching award at
the University of Notre Dame. He was selected as a DAAD AInet fellow for the Postdoc-NeT-AI
in AI and robotics. His research interests include applied mechanics, nonlinear control, robotics,
and Artificial Intelligence (AI) with health care and smart manufacturing applications. His current

work focuses on developing a flexible and collaborative robotic manufacturing cell for high-
precision assembly.