Photographs at: http://www.mediagab.it/lazona/cibernetica/SamRobot/SamRobot.html Sam was a modular system. Every called module ("agent") had a simple and precise task (which was strongly motivated from reading the book "The Society of Mind" by Marvin Minsky). Many years later, a friend was successful in summarizing in simple words a concept that has always fascinated me. He said: "the control would have to be the exception and not the rule".. In the article "A robust layered control system for a mobile robot" by Rodney A. Brooks (MIT Press A.I. Memo 864 September, 1985) that I got much later, after the construction of the robot, thanks to the Internet, the architecture of a similar system is described. In the plan of Sam, there were modular agents for the movement, navigation, the survey of obstacles, the ultrasonic sight, the mapping of space and the coordination between modules. The agents had a life of their own and worked alone until receiving stimuli from other agents. In that moment they only modified their behavior based on the type and the importance of the stimulus. Therefore, in truth a central controller did not exist. Every agent communicated its state and the others reacted consequently. This architecture has been demonstrated to be very robust, a simple one to implement, and at times "unforeseeable" because the robot did numerous things that I had not minimally forseen. The movement of the robot happened through two drive wheels with motors separated so that they also served for steering. A third free wheel served to balance the structure (3 points of support). The drive wheels had sensors made of spinning discs with holes and photo sensors attached. The sensors allowed calculation of movement with one rotation every 10 millimeters and also served as a third party arrangement for obstacles (the other two were an ultrasonic telemeter and a group of infrared sensors in the perimeter of the base that reflected objects). The driver for the motors drove the wheels, using a transistor, they allowed 3 ways of working: forward, reverse, or stopping. The combination of the three states for each motor, allowed 9 types of maneuvers possible. In order to prevent damage to the two motors, especially in phase departure, the connection between motor and wheel was made through rubber straps. The head of the robot, contained the ultrasonic telemeter and 2 photoelectric sensors. It could turn 270 degrees thanks to a continuous turning motor with gear reduction. Also here, an attached sensor indicated the relative position of the head. Therefore, the robot in initilization phase, had to turn the head until it found the start position made with a reed switch in order to calculate the position based on the impulses from the sensor. The analog circuit of the telemeter was made with operational amplifiers and used a specific technique that consisted, after the transmission, in progressively increasing the sensitivity of the receiver in order to avoid undesired false readings due to echoes or resonance in the design. Other analog circuits served to control the photosensors used for proximity, for energy management (two large 6V acid lead batteries were used) and for the photoelectric cells in the head. The robot had also passive IR, one of the first products on the market for sensing people, used currently in nearly all antitheft systems. The main control card was made with a Z80 microprocessor with 8K of RAM and 8K of ROM. Besides the devices necessary for the operation of the micro, a second card mounted on the tower had in/out ports, timers, ADC and a chip for serial communication. For testing the robot and program development I had to construct a special connected module to call the computer SIPCOM that can be seen in one of the photographs in the website. The difficult part was the programming of EPROM memories, made with discreet circuits (I still did not know the microcontrollers). It had eleven TTL chips and a timer in order to allow the programming of the memories with modes for microimpulses (?). After many years of absence, after my return from travels around Argentina, I found the robot in my relatives' house. The batteries were missing and, worse still, the computer memories had probably lost their programming because I was not successful in making it work. The original program was found on cassette tapes used in MSX computers and impossible to read today. Incredible is the age of computer science. The problem was not just to restore the information but to be able to read it and interpret it after several years. It was all fine that only the printout remained accessible because fortunately our eyes do not have a "new version". (?) The complete article for SAM is found at: http://www.mediagab.it/lazona/cibernetica/SamRobot/SamRobot.html ©(2001) Gabriel Rapetti Email: gabriel@mediacomm.it Translation from Italian to English © 2002 by Popeye Theophilus Barrnumb. Popeye@P-t-B.com http://P-t-B.com