This Mechanical arm is quite impressive and interesting to build. (3/18/2006)
This project is originally publicated by LEGO as ProChallenge. It took about two days to assemble it and create the program. I built this robotic arm following the instructions and doing some minor modifications, also the program is different to the original sample located in the CD. I programmed this mechanical arm to look for an object, pick it up and drop it out of the table.
This mechanical arm needs two motors, two touch sensors, the RCX and one light sensor. First, It raises the arm to detect the "initial point". The original program in the CD have a problem, if the arm is raised, the motor continues to run raising the arm and the program does not detect the pressed switch. Second, the arm goes from left to right until the light sensor detects any object. After the object is detected, the arm picks it up and drop it out of the table.
Here is the two sensors that detects the position of the arm. The touch sensors are connected in parallel. The left sensor detectes when the arm is completely raised. The right touch sensor detects when the "hand" is open and, consequently, in the lower position.
The picture shows the "hand" open. The touch sensor is activated. The wheels helps to pick any object. Without the wheels, any object may slip and fall.
The light sensor detects the object when the robotic arm is looking for it. After the object is picked up and lifted, the light sensor detects the edge of the table and the object is dropped.
The robotic arm holding my car keys
This project is interesting but it doesn't have a real application. The movement of the arm is only horizontal and vertical. To create a better robotic arm, I need more sensors and two more motors. With one more motor it will have three axis of movement, also know as "degrees of freedom". With more degrees of freedom, any robotic arm will be able to perform more tasks, inclusive, assemble some items.
Creating and assembling any mechanical device, is a lot of fun and entertainment. It may be also frustrating without any knowledge of mechanics or engineering, however, after a while, things are easy to build.
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