PmWiki | Robots / Wheels

Lab 2 Question 3

Name: Allison Fidler (blue cohort)

Purpose: The purpose of Question 3 was to determine the sensitivity of Create's bump wheel drop sensors as well as the IR sources and virtual wall and docking station. To test the sensitivity of the bump sensors, we placed nickels on the front bumper of the Create to test the mass that is needed to activate the sensor. To test the bump sensor, we applied various amounts of pressure to the wheels until the sensor was activated. To test the IR sources, the virtual wall, and docking station, we tested the IR signal strength from various distances using different forms of IR light to see if the sensors were activated.

Results:

Wheel drops: The Create iRobots only sends commands qualitatively. If the wheel is raised, the value is 1. If the wheel is dropped, the value is 0. Wheel dropped means that the wheel is not fully pressed into the robot while wheel raised means that the wheel can't retract any more. From our tests, we learned that you barely have to apply pressure to the wheels for the sensors to be activated. When we lifted one half of the robot and left the right wheel barely touching the table, the robot sensed this and sent back a return command of 4. This means that the right wheel drop sensor was activated.

bump sensors: The bump sensors sensitivity vary depending on the solidity of the object and the speed at which the robot hits the object. Since the bump sensor is operated by a spring that holds the robot's bumper, when the spring compresses the sensor is turned on. If the robot hits a solid object, (such as a wall), at a high speed, then the sensitivity would be greater than if the robot hit a soft object, (such as a pillow) at the same speed.

IR sensors: When using IR sensors found around the household, we discovered that you can't get the IR sensors to change values. When attempted, the robot sent back a return command of 255, which means that it wasn't picking up any infared signal. This is because the IR command only senses codes from the IR remote because it looks for a certain frequency that only the remote seems to have

We also discovered that the docking station uses the electrodes on the bottom of the robot to charge the robot. When you cover up one of the electrodes, the circuit is broken so the robot doesn't sense that it is in the docking station. We also learned that the distance that you are away from the docking station doesn't usually affect the sensor readings. One possible reason by why the readings may vary though, is the robot's environment. The more objects around the robot, the more scattered the infared signal will be which will affect your readings

The virtual wall only works when you cover either both the infared receiver on the virtual wall and the infared receiver on the robot with electrical tape or just cover the receiver on the robot.If you don't cover the receivers, the virtual wall will send infared signals in one direction and the robot will not be able to detect where the signals are coming from because it is looking in all directions and can't process the information By covering the receiver on the robot with electrical tape, you are restricting the sending of infared signals so that it only sends a line of infared light that will detect the signals from the virtual wall. When these signals intersect, the robot can then follow the signal to detect where the virtual wall really is.