61 lines
1.9 KiB
Markdown
61 lines
1.9 KiB
Markdown
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# Move Straight With Gyro
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## Introduction @fullscreen
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Rotating using a wheel is not precise. The wheel can slip or the motors
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can be slightly different.
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With the help of the gyro you can detect and correct deviations in your trajectory.
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* [EV3 Driving Base](https://le-www-live-s.legocdn.com/sc/media/lessons/mindstorms-ev3/building-instructions/ev3-rem-driving-base-79bebfc16bd491186ea9c9069842155e.pdf)
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* [EV3 Driving Base with Gyro](https://le-www-live-s.legocdn.com/sc/media/lessons/mindstorms-ev3/building-instructions/ev3-gyro-sensor-driving-base-a521f8ebe355c281c006418395309e15.pdf)
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## Step 1 Calibration
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Add a ``||sensors:calibrate gyro||`` block in a ``||brick:on button enter pressed||`` block so that you can manually start a calibration process. Run the calibration
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at least once after connecting the gyro.
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```blocks
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brick.showPorts()
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sensors.gyro2.calibrate()
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```
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## Step 2 Compute the error
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Make a new **error** variable and drag the ``||sensors:gyro rate||``
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and multiply it by -1. Since the rate shows the rotation rate, we will
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counter it by negating it.
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```blocks
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let error = 0
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brick.showPorts()
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sensors.gyro2.calibrate()
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while (true) {
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error = sensors.gyro2.rate() * -1
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}
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```
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## Step 3 Steer with feedback
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Drag a ``||motors:steer motors||`` block under the variable and pass
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the **error** variable into the turn ratio section.
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If the robot is turning right, the gyro will report a positive rotation rate
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and the turn ratio will be negative which will the turn the robot left!
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```blocks
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let error = 0
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brick.showPorts()
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sensors.gyro2.calibrate()
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while (true) {
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error = sensors.gyro2.rate() * -1
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motors.largeBC.steer(error, 50)
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}
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```
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## Step 4 Run it!
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Download to your brick and test out if the robot is going straight.
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This kind of technique is called a proportional controller;
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it corrects the inputs (motor speed) with a feedback proportional to the output (rotation rate).
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