Abstract

Self-driving cars use a variety of sensors to evaluate and navigate their environment. Each type of sensor has advantages and disadvantages. In this project you will evaluate two common types of distance sensor (ultrasonic and infrared) and compare their performance in different scenarios.

Objective

Evaluate the performance of two different types of sensors for an autonomous vehicle.

Introduction

Self-driving cars, also called driverless cars or autonomous vehicles, are cars that can drive without input from a human driver. They therefore cannot rely on human senses like sight and sound to steer—they must use electronic sensors instead. Electronic sensors detect things like lane lines, traffic lights, road signs, pedestrians, and other cars and obstacles in the road. Examples of electronic sensors used by driverless cars include:

• Lidar (light detection and ranging) uses lasers to measure the distance to objects in the environment by measuring the amount of time it takes a laser pulse to bounce off an object and come back to the sensor.
• Radar (radio detection and ranging) is similar to Lidar but uses radio waves instead of light.
• Sonar or ultrasonic sensors emit bursts of sound and measure how long they take to reflect and travel back to the sensor. This is similar to how animals like bats use sound for echolocation.
• Cameras record video of the environment around the car and use image-processing algorithms to identify objects in the field of view.

Different sensors might work better under different conditions. For example, some might not work as well at night or in the rain. Some might not do a good job detecting small objects. Some might detect some surfaces or materials better than others. Engineers have to evaluate the pros and cons of different sensors when deciding which ones to use for a self-driving car.

In this project you will compare two types of distance sensors that are commonly used with robotics projects involving an Arduino®: an ultrasonic sensor and an infrared sensor (Figure 1). The ultrasonic sensor sends out a burst of ultrasonic sound and measures how long it takes this sound to bounce back to the sensor. You can then calculate the distance to the target object using the speed of sound. The infrared sensor emits infrared light and measures the amount of reflected light, which decreases as the target object gets farther away. You can find the corresponding distance using a graph in the sensor's datasheet.

If you wanted to build your own autonomous car using an Arduino, this project will help you evaluate which sensor(s) you might want to use.

Terms and Concepts

• Self-driving car
• Driverless car
• Autonomous vehicle
• Sensor
• Lidar
• Radar
• Sonar
• Ultrasonic
• Camera
• Infrared

Questions

Look at the datasheets for both sensors linked in the bibliography and answer the following questions.

• What is each sensor's range?
• What are each sensor's power requirements (supply voltage and current)?
• What is each sensor's communication or output type?
• What external factors can affect the performance of each sensor or cause inaccurate readings?

Read the articles about self-driving cars linked in the bibliography and answer the following questions.

• What types of sensors do real-world self-driving cars use?
• What are the advantages and disadvantages of each type of sensor?

Materials and Equipment

• Science Buddies Electronics Kit for Arduino, available from our partner Home Science Tools.
• Computer with:
  • Access to the Arduino IDE (either installed local version or web-based editor). See the Use Arduino with Chromebook page if you have a Chromebook.
  • USB port. The Science Buddies kit comes with a USB-A to B cable. The "B" end plugs into the Arduino and the "A" end plugs into your computer. You will need an adapter or different cable if your computer only has USB-C ports.
• You will also need to gather the following items, not included in the kit:
  • Sharp IR distance sensor
  • 3-pin JST cable with breadboard pins
  • Tape measure or meterstick
  • Small box or cup to prop the sensors up on
  • Tape to hold the sensor in place
  • Assorted objects to test with the sensors. Your objects should be a range of shapes, sizes, and textures. Here are a few examples:
    • Paper (different colors)
    • Hard materials like metal or plastic
    • Soft or porous materials (cloth, fabric, clothing, sponges, foam, stuffed animals, etc.)
    • Irregularly-shaped objects (e.g. toys)
    • Small or narrow objects (pencil, paperclip, pushpin, etc.)
  • Lab notebook

Experimental Procedure

Global Connections

Variations

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Related Links

• Science Fair Project Guide
• Other Ideas Like This
• Robotics Project Ideas
• Self-Driving Cars Project Ideas
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