Week2ProjectReport

=Week 2 Progress=

For the second week of the project, we started building the robotic arm using a few hardware and software components. A list of the parts is listed below.

1. Dynamixel AX-12a servos which have sensors and potentiometer inside them. 2. Dynamixel compatible 3pin Cables. 3, USB2Dynamixel adapter which is used for the serial communication between the computer and the servos. 4. Frames which were used to connect the servos together. 5. USB extension cable which plugs into the USB2Dynamixel adapter and then into the PC. 6. 9-12 Volt adapter that connects directly into the USB2Dynamixel adapter to power the servos. 7. Urbiscript by Gostai together with the bioloid library.

At first we tried out different methods to see which one would be most efficient to use for the arm. Both Dean and Thibault designed a different arm to see which one was the closest to a real human arm. The first version was designed by Thibault, however we did not take any photos since the second version of the arm was rebuilt using his version. It was working well and we were able able to move the shoulder as the ball join was simulated by three servos, but the shape did not completely corresponds to the human arm shape. The second version, the one designed by Dean using the first version, seemed better because the functionalities where the same and the design was closer to our arm. As a final decision we stuck to the second version.

As you can see, we have listed the hardware and software components that we needed for our robotic arm. The project required only 4 servos, where 3 of them were used for the shoulder and 1 of them for the elbow. The first servo that we have used was for the Y axis which lifted the whole arm up and down. The first servo required and used more torque since all other servos and frames were attached to it. At first we thought it would be a problem because when we connected all the servos together, the arm would just go back down if it was lifted up because it required more torque, however that wasn't an issue because once we plugged it into the power supply, all servos became more stable and harder to move which allowed the arm to stay in one position, but the best thing was that once the servo had executed a command, it would lock that servo so that it can no longer be moved manually.

The second servo had to deal with the X axis which was able to lift the arm up and down again, but this time using the X axis. this basically gave us the simple arm movement of a human arm which was the same as the robotic arms that only have the X and Y degree of freedom. However once the X and Y Axis servos were joined together, we were able to connect the Z axis servo which was able to rotate the arm itself using the Z axis. A photo of the picture has been provided below to show what exactly we mean because it is difficult to explain what function each axis does. The last servo that we have used was the elbow. To be able to provide an efficient example of human-like movements we needed to have an elbow. however we did not add a wrist and a grabber since it would have required 2 more servos, and we wouldn't have had enough time to deal with all. However this is not an issue, because the 4 servos provide enough proof that our arm can mimic the human arm movements, maybe not perfectly, but very close to it.

In the below image, we have drawn a few letters to show each servo in order and we have also drawn a small example to show in which direction each servo moves. As you can see servo A is the main servo which holds all other servos. This servo moves along the Y axis because it moves up and down. Servo B is the second servo used and it uses the X axis because it moves right(to go up) and left(to go back down). Servo C is used as the Z axis because it allows us to rotate it left and right which would be used mainly for servo D which is the elbow which goes only up and down just like a normal servo does. Without servo C, the Z axis, servo D the elbow will only move in one direction like the other robotic arms we have shown, but since we have servo C to serve as the Z axis, we can now move servo D to face in another position. By using all four servos combined together, we are able to get a human-like arm movement.