Our goal is to get the robot to move forward as it follows the line.
This has the undesireable effect of making the robot possibly move backwards. The problem is that: Any values of Steering greater than 40 or less than -40 will result in the robot wheels moving in opposite directions. If the values returned by the light sensor range from 0 to 100, then the Midpoint is 50. The Midpoint of the light range for a calibrated light sensor has the value of 50. Method 2: Steering in the Move block Adjusted by a Factor Problem: There is a potential problem if you use the above programs with a robot that has calibrated light sensors. The power level for the Motor block should be set to a low value at first and then gradually increase this to see how well the robot is able to follow the line And the combination of light sensor, Subtraction with k, and Motor block should be placed within an infinite loop. The duration of the Motor block should be sent to infinity. For example, if the value of the light sensor on the white background is 50 and the value of the light sensor on the black line is 25, then the value of the constant (k) should be the midpont of those two values (50+25)/2 which equals 37.5. The "light range" is the difference between the lowest and highest values obtained from the light sensor. In general, the value of the constant (k) should be set to the midpoint of the light range. The other part of the formula you need to determine is the value for the constant (k). Constant (k) minus the Light Sensor Value equals the new steering amountWhich formula you decide to use will depend on whether you want the robot to follow the left side or the right side of the line.Light Sensor Value minus a constant (k) equals the new steering amount.There are two basic ways of creating the formula. The basic idea in using this block for line following is that you want to get the robot to steer in one direction if the light sensor sees the black line and to steer in the other direction if the light sensor sees the white surface background.
If the value is equal to 0 then the robot will drive straight. Values greater than 0 will steer the robot in the other direction. Values less than 0 will steer the robot in one direction.
#ROBOTC CODE SOFTWARE#
Method 1: Steering in the Move block The Mindstorms NXT software provides a Move block which allows you to specify the amount of Steering in the form of an amount that varries between -100 and +100. Programs with "Calibrated" light sensors may work in different environments and under different conditions without modification-all that needs to be done is to re-calibrate the sensors. Some programs may work better with un-calibrated sensors-especially those that pass values directly to the steering option of the Move block.
The are practical advantages and disadvantages to each. Principle: If the robot has only one light sensor, the line following program will instruct the robot to follow only one side of the line (left or right depending on the formulas used in the program and the orientation of the motors in the robot design).For NXT, many of the programs below use either " Calibrated" or " Un-Calibrated" light sensors. Several of the various programs are discussed and illustrated below. There are dozens (probably hundreds) of different programs that can be written to help the robot follow a line. Whether the line is straight, curved, or a combination of both, the robot will use a simple formula to determine its position in relation to the line and how it should move in order to stay on the line. Most line following programs utilize some formula for determining if the robot should move to the left, or right, in order to stay on the line. Line Following Methods (Example Programs)
#ROBOTC CODE CODE#
The code below is more of a pseudocode than any actual code you can copy-and-paste into your program. The getLightPercent() and getLightPortion() functions below may need to be created by you. Once the condition has been met in the until function, then stop the line following task to stop following the line. The purpose of using a separate task for line following is so you can break from the line following based on the use of existing until functions such as untilSonar(), untilTouch(), untilDistance(), wait(), etc. This exercise walks you through the different steps in setting up a line following task and running it from within the main task. If you have RobotC, here is a good exercise in the task of LineFollowing. Line Following RobotC Include File Exercise in Line Following (for RobotC) A Non-Functioning EV3 (i.e., frozen or dead).
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