Object Detection & Avoidance

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Purpose

As a result of the increasing frequency of disasters, at global and community levels, we came in need of our team’s robot to be able to avoid many hazards when going into dangerous situations and how the function of avoiding objects was decided upon.

Design Objective

The primary purpose of this subsystem is to collect information on the robot’s surroundings, relaying information either to a remote operator or an onboard processor for decision making. This will allow the controller to navigate unknown environments and make decisions on the robot’s next steps. Various technologies can be utilized to meet this goal, including:

Lidar and Radar

Lidar A method for determining ranges by targeting an object with a laser and measuring the time for the reflected light to return to the receiver. It works as follows: Laser signals are emitted and reach an obstacle it then reflects back and the signal returns to the receiver and a pulse is generated.  Advantages: Short-wavelength allows for detection of smaller objects Can construct an exact 3D monochromatic image of an object Disadvantages: Limited Usage in nighttime and cloudy weather Expensive Limited operating altitudes; may be more easily affected by pressure changes

Radar A method used to detect objects at a distance and define their speed. Relatively the same process as Lidar but the main difference is that they use different types of signals to detect objects.  Advantages: Can operate in cloudy weather conditions and at night Longer operating distance Disadvantages: Cannot detect as small of objects; not as precise as Lidar

Ultrasonic Sensors

• An instrument that measures the distance to an object using ultrasonic sound waves. An ultrasonic sensor uses a transducer to send and receive ultrasonic pulses that relay back information about an object’s proximity.
• ​​Advantages of ultrasonic sensors include:
  • Immune to target color, reflectivity, and transparency
  • Unaffected by environmental light conditions 
  • Performs well in dirty and wet environments

Infrared

• Works by sending an infrared light with some frequency, and then detecting if some of the light has reflected back to the sensor. 
• Disadvantages:
  • Infrared frequencies are influenced by hard articles (for example dividers, entryways), smoke, dust, haze, daylight, etc and may falsely report an obstruction
  • Very easily affected by the color of the object and may fail to report an obstruction
  • Cannot provide distance information

Cameras & Constant RC Control

Another possible option to avoid objects is to manually control the robot to move around obstacles in its path. Users can do this by controlling the robot with RC. RC Technology uses radio waves to communicate from a distance. The transmitter on the controller sends a specific number of electrical pulses to the receiver on the robot, to make it perform various actions. Incorporating this type of mechanism onto our robot along with its self-driving would allow for an easier and more efficient way of ensuring the robot product avoids objects.

Critical parts of an RC controller:

• Transmitter
  • The remote control contains a radio transmitter that operates on a particular frequency that the receiver is designed to receive.
• Receiver
  • The receiver is fixed within the remotely operated device and constantly receives signals from the transmitter. When a transmission is identified, it translates the number of electrical pulses from the radio wave into action.

Here it is also important to remember that along with the robot’s battery powering the receiver, the transmitter requires its own source of power. Thus the controller would also depend on power, usually in the form of a 9 – Volt battery.

Metrics

Distance from object related to when and how to avoid the obstacle(s) What/ how will we avoid it… (up, down, left, or right) Ultrasonic: Phase delay Peak value of the echo Echo time Data polling rate

Infrared sensors measurements may include: Frequency Range Wavelength Range Sensing reach or distance Data rate RC Mechanisms: Radio frequency in Hertz (Hz) Effectual angle Power consumption

Constraints

Size of sensors Accuracy (at high speed, clouded conditions, etc.?) Degree affected by different operation mediums (smoke, murky water, etc.) Temperature compensation Minimum object detection size

Upper bound on cost Water-resistant Minimum detection distance Distance between transmitter and receiver for an RC option

Potentially Relevant Codes and Standards

• Robotics – Performance criteria and related test methods for service robots – Part 2: Navigation

Next Steps

• Understanding of what it will take for the robot to be able to avoid obstacles on land or submerged in water to choose the most applicable sensor for each scenario.
• Propeller knowledge, and understanding of the necessary components of what each sensor has to offer.
• The math and physics behind distance calculations and relate it to the robots movement allowing it to avoid the obstacle or  hit the obstacle with no sufficient damage.
• Determine sizing and amount of sensors needed.

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Citations

1. Yaguang Zhu, Baomin Yi, Tong Guo, “A Simple Outdoor Environment Obstacle Detection Method Based on Information Fusion of Depth and Infrared“, Journal of Robotics, vol. 2016, Article ID 2379685, 10 pages, 2016, from https://www.hindawi.com/journals/jr/2016/2379685/
2. Dunbar, B. (2015, May 6). What are radio waves? NASA. Retrieved October 5, 2021, from https://www.nasa.gov/directorates/heo/scan/communications/outreach/funfacts/what_are_radio_waves.
3. Long range RC transmitter XPAD2 with built-in GPS and video receiver. Ekofastba. (2014). Retrieved October 5, 2021, from https://ekofastba.com/shop/long-range-rc-transmitter-xpad2-with-built-in-gps-and-video-receiver/.
4. How to choose the best sensor for clear object detection. Banner Engineering. (n.d.). Retrieved October 5, 2021, from https://www.bannerengineering.com/us/en/company/expert-insights/selecting-clear-object-detection-sensors.html.