Tekkotsu (see www.Tekkotsu.org)
is an application development framework for mobile robots. It was
originally developed for the Sony AIBO robot dog, but now supports
many other platforms. ("Tekkotsu" literally means iron bones
in Japanese, and refers to a metal framework, such as the skeleton of
a building.) At its lowest level, Tekkotsu provides primitives for
sensory processing, smooth control of effectors, and event-based
communication. Higher level facilities include a hierarchical state
machine formalism for managing control flow in the application, a
vision system, and an automatically maintained world map. Tekkotsu
also provides housekeeping and utility functions useful to application
developers, such as timers and profilers, and a set of remote
monitoring tools to permit real-time monitoring of what's going on
inside the robot.
Tekkotsu is object-oriented, making extensive use of C++ templates,
multiple inheritance, and polymorphism (operator overloading). This
makes it easy for application developers to create their own
customized facilities without having to change the Tekkotsu source
code. They simply define subclasses that inherit from the Tekkotsu
base classes, and override any member functions requiring
customization.
A Tekkotsu application is organized as a collection of Behavior and
MotionCommand classes. Their member functions run in two cooperating
processes, "Main" and "Motion". Separate processes are used because
they require different execution styles. Main handles perception and
decision making; these are deliberative processes where each operation
can potentially take a substantial amount of time. Motion is
concerned with realtime control of effectors: all operations must be
guaranteed to complete quickly, because several may have to be
performed within the current 32 msec timeslice. (If a Motion process
doesn't run quickly enough, the robot might fall over, or its actions
might appear jerky.) A third process, SoundPlay, handles audio
output, and operates under the same realtime constraints as Motion.
The processes are labeled MainObj, MotoObj, and SoundPlay in the
diagram below:
Behaviors are instantiated in and run exclusively in the Main process'
address space (green hatching in the
diagram above). MotionCommands are instantiated in shared memory
(solid blue in the diagram). Most of
their computation is done in the Motion process (orange hatching), but certain member
functions run in Main. A clever mutual exclusion mechanism called an
MMAccessor provides Behaviors running in Main with a safe way to
update shared memory structures while they are in use by the
MotionManager running in Motion.
