Gyro tutorials (#930)

* gyro tutorials

* tutorials

* fix gyro simulator

* images

* updated image

* fix svg errors

docs/tutorials/calibrate-gyro.md

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+# Calibrate Gyro
+
+## Introduction @fullscreen
+
+The gyroscope is a very useful sensor in the EV3 system. It detects the rotation rate
+which can be very useful to correct the trajectory of the robot and do precise turns.
+
+However, the sensor can be imprecise and subject to drifting. It is recommend to
+calibrate your sensor at least once after starting your brick. You don't have to 
+recalibrate on every run.
+
+* [EV3 Driving Base](https://le-www-live-s.legocdn.com/sc/media/lessons/mindstorms-ev3/building-instructions/ev3-rem-driving-base-79bebfc16bd491186ea9c9069842155e.pdf)
+* [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)
+
+
+## Step 1 Show ports
+
+Add the ``||brick:show ports||`` to see the status of the gyroscope.
+
+```blocks
+brick.showPorts()
+```
+
+
+## Step 2 Calibration
+
+Add a ``||sensors:calibrate gyro||`` block to calibrate the gyro. The block
+detects if the sensor is present and does a full reset of the sensor if necessary.
+
+```blocks
+brick.showPorts()
+sensors.gyro2.calibrate()
+```
+
+## Step 3 Download and run @fullscreen
+
+Download this program to your brick and press the ENTER button.

docs/tutorials/gyro.md

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+# Gyro tutorials
+
+## Tutorials
+
+```codecard
+[{
+  "name": "Calibrate",
+  "description": "Make sure you gyro sensor is ready to use",
+  "cardType": "tutorial",
+  "url":"/tutorials/calibrate-gyro",
+  "imageUrl":"/static/tutorials/calibrate-gyro.png"
+}, {
+  "name": "Move Straight",
+  "description": "Use the gyro to correct the trajectory of the robot",
+  "cardType": "tutorial",
+  "url":"/tutorials/move-straight-with-gyro",
+  "imageUrl":"/static/tutorials/move-straight-with-gyro.png"
+}]
+```

docs/tutorials/move-straight-with-gyro.md

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