Introduction: Robotrex Robotic Dinasaur
Here is our robotic project; Robotrex. A robotic dinosaur. Its name comes from the words "Robot" and "tyrosaurus-Rex". Inspired from our older projects "Bigfoot" and "the Goggles", this project was built specially for our endtas.com fair stand in 2004 Izmir international fair. Instead of forgetting it around somewhere under dust i worked on a plywood cutting plan and a computer model of it to share the project with our visitors.
Step 1: Constructing Body and the Plywood Cutting Plan
The Robotrex uses the walking principle of the "Bigfoot". But along with the placing of servos to its foot shape and the center of gravity, it has got some important structural improvements which are the results of a careful study which took several days of time before the fair.Just like the Bigfoot, this robot is also powered by two servos. But with one big difference instead of the servo placing scheme of the Bigfoot where the servos were looking towards the outside of the body, (with links also outside) this robot has them all inside the body. The power transferring parts are also placed between the legs, inside the body almost completely hidden. The feet-up-down servo is placed at the back, facing the inside of the robot-body where it used to sit in the front of Bigfoot facing forward. The feet-forward-reward servo is placed at the front bottom, facing backwards into the robot-body where it used to sit at the rear part of The Bigfoot facing down. Where the power of the feet-forward-reward servo is transferred to the legs by means of a iron wire, in Robotrex, a rigid plywood piece is used for the same purpose. And this concludes to a robot which moves more determinently with better balance. The power of the feet-up-down servo is transferred not to the tip of the feet like it is in the Bigfoot but to the mid part of the feet resulting a much more stable standing robot. By means of the improvements like this and a much better center of gravity, the power of the servos are transferred to the legs and ground with more efficiency resulting less power loss due to structure. This also yields a longer battery life. The robotrex can run for hours with its 4 rechargeable AA batteries.
Step 2: Circuitry Etc
As for the circuitry, nothing is different than the one used in our project "The goggles". The sensors of the system:
a- Two sound sensors. Independent two condenser microphone sensors at the right and left. With these sensors, the robot can hear the sounds around it and also differentiate between sounds coming from the left side and right side.
b- Light sensor. This is a photodiode located at the front of the Robotrex facing forward. With this sensor, the robot can sense and measure the light level around it as a 5 bit (0-31) value.
c- Infra Red (IR) obstacle detection. With this microprocessor based (OZZ-IR-DIS chip) dedicated circuitry Robotrex can sense the obstacles on its way as well as obstacles at the right and left sides within a limit of almost 40cms. Sharp's IR sensors can also be used in a similar manner.
Along with the sensors, the Robotrex has got a "Mood" display consisting of a 5x7 dot matrix LED display where it can display its mood as smiling, crying, scary etc faces (16 total). The mood display can also be built and used as a stand-alone module. While the mood display is showing the emotions of the robot the main processor can also produce a variety of sound effects to improve the communication of the robot with the outer world.
Step 3: Brains and the Body
The Robotrex which is powered by three separate microcontrollers, can also be built by using only one micro, the main controller. In this scheme there wil be no mood display and no IR obstacle detection. Moods can be expressed by sounds only and obstacles can be detected by the whisker type touch sensors like we use in our robugs and in Bigfoot.
As the structure, you can use plywood for making the parts as well as mock-up plastics, sheet aluminium etc. You can give organic forms over the finished structure by using polyurethane foam and obtain a smooth surface by sanding and finalizing the shape by applying steel putty & resanding. With these, the robot can become a better looking dinasaur or any creature you like. It is all up to you. The project can be modified in any way you like.
Before starting to build robotrex, don't forget to read more about its ancestors; The Bigfoot and The Goggles. The articles about them can be found at our robotics website http://www.endtas.com/robot. The circuit schematics, photos etc in those articles can be helpfull while building the Robotrex. And if you have questions, just add them to the end of this article as comments. I'll try to repply them as soon as possible. Have fun and build many dinosaurs. :)