PASSIVE ATTACHMENTS in Font

Drawer ECC200 in Font PASSIVE ATTACHMENTS

holding the bed in place, and when the trigger is pushed backward, the dump bed becomes unstable and falls forward, as shown in Figure 8 12. The tilt bed needs to be mounted high enough on the robot chassis so that when the robot moves into place for the delivery, the contents of the tilt bed will be able to reach their destination. For example, in the FLL 2008 Climate Connections game, one of the missions was to deliver a number of items behind a short wall of LEGO bricks. In order for a tilt bed to work correctly in delivering the items, it needed to be mounted high enough to reach over the wall of LEGO bricks and still have room for the bed to tilt enough for the contents to land in the proper location.

Figure 8 11. A dump attachment carring a load of small trees with a trigger in place preventing the dump bed from releasing

Figure 8 12. Once the trigger is pushed backward, the dump bed falls forward and releases the load of small trees. The tilting action itself will be done by taking advantage of potential energy that is stored in the tilt bed by locking it in place with a lever or pin.

Note Potential energy is energy that is stored within a system. It exists when there is a force that tends to pull an object back toward some lower energy position. This force is often called a restoring force. For example, when a rubber band is stretched to the left, it exerts a force to the right so as to return to its original, unstretched position. Similarly, when a mass is lifted up, the force of gravity will act to bring it back down. The action of stretching the rubber band or lifting the mass requires energy to perform. The energy that went into lifting up the mass is stored in its position in the gravitational field, and the energy it took to stretch the rubber band is stored in the rubber.

Now, the energy we used to lift the tilt bed in place is storing energy for tilting when the lever or pin holding it in place is removed. The balance of the tilting bed should be designed in such a way that when the bed is in not being held in place by a lever or pin, it will return quickly to the dump state. To adjust the balance of your tilt bed, you just need to move the position of the fulcrum. If gravity is not enough to tilt the bed as desired, a spring can be added by using a LEGO belt attached to the tilting bed. When the bed is in delivery state, the belt is stretched, and once the trigger is pressed, the energy bound in the belt will release and cause the bed to dump its load. The trigger for your dump bed will be located in such a way that when the robot arrives at the desired delivery location, the trigger will be pressed. Just like with other passive attachments, be sure to make the trigger big enough that you have plenty of room for error. You don t want to make the trigger so small or difficult to activate that you decrease your chances of completing the mission correctly each time. Now, for your robot to make the delivery, you load up the items into your tilt bed while the robot is sitting in base. Then, the robot navigates to the desired dumping zone or location. Drive forward until the tilt bed trigger is pushed and the tilt bed releases and dumps its contents in the proper location.