Design Bridge robot

Mechanical parts

Wheels

There are two driving "k'nex" wheels for the motion of the robot and a castor wheel for the support. It was easier to use the "k'nex" wheels because we already had them, so there was no need to print or buy different ones. However, an adaptor had to be created to fix them to the motors. Two models of adaptator was created and finally, it was the white one (see on the picture) which was chosen. Regarding the castor wheel, it was bought in a shop. It had to be raised because otherwise the robot would be leant to the front (see on the picture).

                   

Support for the PCB and the Arduino

The PCB-Arduino block is placed above the castor wheel. Indeed, there is a laser cut bridge where both the PCB and the Arduino can be put on. This bridge is also the place where the castor wheel is fixed, allowing to raise it.

Arm and gripper

The arm is composed of three parts: the support of the pyramids, the cylinder and the main plate.

The first one is composed of two pyramids and an electromagnet in between them. Indeed, for the gripping task, rather than using a classic gripper (like a clamp) to take the bridge, it was decided to put a little metal part in the bridge so it can be gripped with an electromagnet. The use of an electromagnet was an easy solution to lift the arm because then the robot only needs one motor to move the arm.. To avoid that the bridge slips or turns when it is attached to the arm, two pyramids were printed in order to fix the bridge in the right place. These pyramids go in square holes made on the bridge.

The second part is the cylinder, which is the base of the arm. It is a printed piece and it is the connection between the arm and the motor. Also, since the width of the arm is long and its weight is high (as it must carry the bridge), the cylinder need to be supported by a bearing on the other side.

The principal plate allows to link the electromagnet to the cylinder (and also to the motor). Its length is 128mm and it was also laser cut.

           

Support of the distance sensors

As the distance sensor measured only from 10 cm to 80 cm, they had to be raised of 10 cm of the floor. That is why a support for the distance sensors longed of at least 10 cm had to be laser cut.

Bridge

The bridge is composed of two plates: a bigger one with two color lines at the two end tips and a smaller one which is glued on the first one. They both have a thickness of 4 mm and two square holes where the pyramids of the arm are placed. Moreover, the little part has a circular hole where the metal part for the electromagnet goes. These two parts were laser cut.

Assembly of the robot

After having commanded, cut, printed and received all the components necessary for the robot, the assembly could start. For that, the principal used tools are bolts and nuts. Brackets are used to reinforce some structure parts and to attach them easily. There are also some parts of the bridge that are glued.