144 lines
4.5 KiB
Markdown
144 lines
4.5 KiB
Markdown
# Object Detection
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Design ways to avoid accidents between vehicles and objects in the road.
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## Connect
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Think about:
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* In what driving situations can a car hit an obstacle?
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* What do you need to be aware of to avoid collisions with obstacles?
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* What causes traffic jams in high density areas?
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## Construct
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### Build
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Build a @boardname@ vehicle that can avoid accidents between vehicles and objects in the road. Start by constructing this model:
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[](https://le-www-live-s.legocdn.com/sc/media/lessons/mindstorms-ev3/building-instructions/ev3-ultrasonic-sensor-driving-base-61ffdfa461aee2470b8ddbeab16e2070.pdf)
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Build an obstacle for your robot to detect. You can build the **cuboid model** out of LEGO bricks or an obstacle of your choice.
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[](https://le-www-live-s.legocdn.com/sc/media/lessons/mindstorms-ev3/building-instructions/ev3-cuboid-dc93b2e60bed2981e76b3bac9ea04558.pdf)
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### ~hint
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If clicking the above images doesn't open the instructions, right-click on the image and choose "Save link as..." to download the PDF.
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### ~
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### Check
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Before you program, check:
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* Are all the wires correctly connected from the motors to ports B and C?
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* Are the wheels correctly installed?
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* Are the wheels rotating freely?
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* Are the wires connected from the Ultrasonic Sensor to port 4?
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### Program
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* Program your robot to detect any obstacles that might appear while the robot is moving forward (or backward).
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* Make the robot stop when it detects an object that is less than 20 cm away.
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Before you program, think about:
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* How will you program the robot to detect obstacles?
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* How will you program the robot to stop at obstacles?
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* Which programming blocks will you use?
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### ~hint
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Consider using these blocks in your solution:
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```block
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brick.buttonEnter.onEvent(ButtonEvent.Pressed, function () {
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})
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motors.largeBC.steer(0, 50)
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pauseUntil(() => true)
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let near = sensors.ultrasonic4.distance() < 20
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motors.stopAll()
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```
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### ~
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### Sample Solution
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1. Start the program when EV3 ``enter`` button is pressed.
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2. Turn motors ``B`` and ``C`` on at speed ``50``.
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3. Wait until Ultrasonic Sensor detects an obstacle at a distance of less than ``20`` cm.
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4. Stops all motors.
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```blocks
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brick.buttonEnter.onEvent(ButtonEvent.Pressed, function () {
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motors.largeBC.steer(0, 50)
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pauseUntil(() => sensors.ultrasonic4.distance() < 20)
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motors.stopAll()
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})
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```
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### Download and test
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Click **Download** and follow the instructions to get your code onto your EV3 Brick. Press the ``center`` button on the EV3 Brick to run the program.
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## Contemplate
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On the road, when a driver sees and object, they slow their car down before coming to a full stop.
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Program your EV3 Driving Base to do the same.
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If the Ultrasonic Sensor:
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* Detects an object less than `10` cm away, make the robot stop.
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* Detects an object between `10` and `20` cm away, make the robot slow down.
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* Does not detect any object, continue to move at full speed.
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### ~hint
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Consider using this block in your solution:
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```block
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if (true) {
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}
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```
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### ~
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### Sample Solution
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```blocks
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loops.forever(function () {
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motors.largeBC.steer(0, 50)
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if (sensors.ultrasonic4.distance() < 10) {
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motors.stopAll()
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} else if (sensors.ultrasonic4.distance() < 20) {
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motors.largeBC.steer(0, 10)
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}
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})
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```
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### Download and test
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Click **Download** and follow the instructions to get your code onto your EV3 Brick. Press the ``center`` button on the EV3 Brick to run the program.
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## Continue
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* Get together with other building teams and make a traffic jam by placing all of your robots in a line with varying amounts of space between them.
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* Have everyone start their robots at the same time and see what happens.
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* Refine your programs so that all of the robots continue driving at the same speed with equal distances between them.
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* Click on the JavaScript tab and experiment with changing the values in the code.
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* Add a custom image or sounds from the Brick or Music menus.
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### Share
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* Share what you think “efficiency in programming” means.
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* Explore the different solutions other programmers came up with.
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* Create a video of your project, especially your final presentation and your robot’s performance. Explain some important features of your software program.
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* Include an image of your program with comments.
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* Add a team photograph!
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Congratulations! What will you design next?
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