| SuperREGIS Technical Overview | |
| Introduction | SuperREGIS is one of four ongoing robotics projects of mine. SuperREGIS was built primarily to explore vision-based navigation techniques and landmark recognition. It was also intended as an experiment in simple internet telepresence. Currently, SuperREGIS is running a simple program enabling to act as a remotely controlled roving webcam. The robot features two RF links allowing it to communicate with a remote host computer, a wireless video camera, sonar and IR ranging sensors, a multi-processor controller, prototyping area and more. SuperREGIS is of moderate size, and carries a total of about 12AH (at 12 volts) in lead-acid batteries. |
| Chassis | SuperREGIS stands about 24 inches tall,
and 16 inches in diameter. The chassis and motors come from Zagros Robotics. I have slightly modified the chassis to elevate it somewhat to give more room to work. I replaced the carriage bolts included with the kit with threaded rod to give the robot more height and cut new spacers from a length of PVC pipe. The platform as sold by Zagoros has difficulty traversing even small bumps on the floor, as the front and rear casters are the same height. This means that when the front caster encounters a low obstacle (such as a door threshold) it has a tendency to lift the drive wheels off the ground, causing the robot to lose traction and stall. This can be remedied by shortening the front caster using smaller spacers than are included with the kit. I just used a few 1/2" nuts. The "Stay the hell out of my way" paint job was done using masking tape and bright yellow paint. The Zagoros unit with the mods above works fairly well, although I haven't used the included motor controller and other odds and ends. The ABS plastic bases are 1/4 inch thick, and very easy to work with (They drill quite nicely). They do flex a bit under weight -- The bottom deck of REGIS, upon which rest its batteries could probably use some reinforcement. The motors are quite powerful but don't draw an unreasonable amount of current. |
| Locomotion | REGIS's motors are controlled via a
fairly simple FET and DPDT relay combination.
Optoisolators isolate the PWM signal from the CPU. Power
to the motors is pulsed through the FET, and the polarity
of the current to the motors is controlled via the DPDT
relay. I don't have a schematic -- I pretty much just did
the PCB layout directly and built the board, but there
are a number of schematics of this type floating around
on the Ne sensorst. Gordon McComb's excellent book, Robot Builder's Bonanza
also has some good places to start for motor controller
ideas. The DPDT relay design is a good bit simpler than an H-bridge, and can easily carry a lot of current.The only real disadvantage is that the relays click when they switch, and have a presumably finite lifetime, being mechanical. |
Sensors |
SuperREGIS uses an array of eight Sharp GP2D12 infra-red rangers, along with Devantech SRF-04 sonar units. The Sharp sensors output an analog voltage that varies inversely with distance. The signal fom the Sharp units is multiplexed via a simple 4051-based circuit. The combination of sonar and IR gives fairly good obstacle detection and ranging information to the main controller, although there is a large blind area beneath the lower deck. |
| Controller | The main controller board consists of a motherboard with SIMM sockets for up to 4 PIC16F877 SIMM Stick boards from Don Macenzie electronics. The 16F877s are networked via IC2. Bootloaders and on each chip make programming a simple matter. The board also provides a power bus for both 12 and 5 volts for use by peripheral devices. The controllers are programmed generally in a combination of PIC assembler and CCS 'C'. |
| Video | The robot carries a BW camera with a 90 degree field of view. The signal from the camera is transmitted via a 2.4 ghz transmitter from www.supercircuits.com. I have tried a number of video transmitters, including the ubiquitous X10 wirelass cams, and the semi-legal 433 mhz units, and have had best results with this model. The drawback is that the camera and transmitter together consume almost 450ma. Fortunately, SuperREGIS's electronics are powered by a 5ah battery, giving decent run time. |
| RF Link | SuperREGIS carries two RF links. The main link is an OCI/LAWN-II RF Modem. Range about 300 feet indoors, with a maximum bit rate of 38,400 baud. The modem is highly reliable, but consumes about 300ma. An auxilliary 433mhz unit based on a SIL-16 unit from Abacom Technologies and a PIC front-end is also installed. This unit uses far less power than the LAWN modem, but is significantly slower and less reliable. |
| Speech | SuperREGIS is equipped with a text-to-speech board from RC Systems. The board supports both parallel and serial interfaces up to 9600 baud. Speech quality is excellent, and the board supports playback of pre-recorded audio and music. An on-board amplifier is included.. |
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