(Georgia Institute of Technology, 2013-06)
Dantam, Neil; Stilman, Mike
We present the Motion Grammar: an approach to
represent and verify robot control policies based on Context-Free
Grammars. The production rules of the grammar represent a
top-down task decomposition of robot behavior. The terminal
symbols of this language represent sensor readings that are
parsed in real-time. Efficient algorithms for context-free parsing
guarantee that online parsing is computationally tractable. We
analyze verification properties and language constraints of this
linguistic modeling approach, show a linguistic basis that unifies
several existing methods, and demonstrate effectiveness through
experiments on a 14-DOF manipulator interacting with 32 objects
(chess pieces) and an unpredictable human adversary. We provide
many of the algorithms discussed as Open Source, permissively
licensed software. ¹
(Georgia Institute of Technology, 2013-06)
Dantam, Neil; Hereid, Ayonga; Ames, Aaron; Stilman, Mike
We present a software synthesis method for speed-
controlled robot walking based on supervisory control of a
context-free Motion Grammar. First, we use Human-Inspired
control to identify parameters for fixed speed walking and for
transitions between fixed speeds, guaranteeing dynamic stability.
Next, we build a Motion Grammar representing the discrete-
time control for this set of speeds. Then, we synthesize C
code from this grammar and generate supervisors¹ online to
achieve desired walking speeds, guaranteeing correctness of
discrete computation. Finally, we demonstrate this approach on
the Aldebaran NAO, showing stable walking transitions with
dynamically selected speeds.
(Georgia Institute of Technology, 2013-04)
Grey, M .X.; Dantam, Neil; Lofaro, Daniel M.; Bobick, Aaron F.; Egerstedt, Magnus B.; Oh, Paul; Stilman, Mike
Humanoid robots require greater software reliability than traditional mechantronic systems if they are to
perform useful tasks in typical human-oriented environments.
This paper covers a software architecture which distributes the
load of computation and control tasks over multiple processes,
enabling fail-safes within the software. These fail-safes ensure
that unexpected crashes or latency do not produce damaging
behavior in the robot. The distribution also offers benefits for
future software development by making the architecture modular
and extensible. Utilizing a low-latency inter-process communication protocol (Ach), processes are able to communicate with
high control frequencies. The key motivation of this software
architecture is to provide a practical framework for safe and
reliable humanoid robot software development. The authors test
and verify this framework on a HUBO2 Plus humanoid robot.