Seven is the UP EEE Mobot Lab's first microcontroller-brained mobile robot, hence giving it the advantage of re-programmability. The fact that it currently uses a fairly generic 68HC11-board with 32K of RAM makes it easy to use readily-available C Interpreters like Interactive C (God bless those people at MIT!). This convenience, helps free the researcher (to some extent) from the often times cumbersome process of implementing assembly language routines, and instead concentrate on the design of behaviors with less effort in the translation from algorithm to code.
Seven also has enough sensors so that with the proper programming, its survivability in real environments like hallways or offices is greatly increased. Basic low-level functions like obstacle avoidance, bump detection and recovery, even light-following and wall-following can be implemented in the robot. Furthermore, closed-loop speed control is also achievable.
Seven was originally constructed as a project in one of the author's graduate courses (Intro to Mobile Robotics). It took a week to construct and/or piece together its basic parts including it's body, brain-board, and interface board which originally consisted of the motor drivers (forward-backward and turning). At this point Seven could already be programmed to do basic movements. Two weeks later, infrared sensors were added to help the mobot achieve wall-following behavior (which was also a requirement in the course). After the course, Seven was tasked with being the Lab's test robot, so that in a span of a few months (of sporadic working), Seven was outfitted with its current supply of sensors: infrared (IR) sensors, bump sensors, light (LDR) sensors, and a shaft encoder. With this relatively adequate hardware, what was left was to write and test the programs that would define Seven's behaviors. These programs would not only be useful to Seven's survival in its surroundings, but would also help researchers gain insight into what other (future) robots may need to do well in their environments with minimal or no human intervention.
As of May 2000, successful programs have already been written using IC which utilize basic low-level behaviors that allow Seven to wander (aimlessly) and follow a light source in a long corridor or a cluttered office with almost no human intervention at all (alas Seven is not yet self-charging). Subsequent programs will address higher-level behaviors like navigating to an assigned/preferred location or doing a catch-and-fetch task. Some additional sensors may need to be added though.
SEVEN's TIMELINE (construction to May 2000)
25 September 1999
Start of construction (required in course)
01 October 1999
Basic mechanical, electronics finished, simple movements implemented (required in course)
05 October 1999
Programmed open-loop half-turning for the wheels (required in course)
18 October 1999
Specialized wall-following behavior implemented (required in course)
08 April 1999
SEVEN modified for Mobot Lab Duty :)
- sensor array: left and right IR emitter + center receiver
- left and right LDRs shaft encoder (in rear motor assembly)
- still used original brain-board but upgraded the sensor-interface board
April - May 2000
IC programs written for lower-layer behaviors. A relatively 'successful' emergent behavior is (aimless) wandering while avoiding obstacles and recovering from bumps. SEVEN is also able to follow light-sources like flashlights.
PICTURES
