Obstacle Detection Module - northern-bites/nbites GitHub Wiki

Our obstacle detection module is composed of three components:

• Vision --> to be replaced with Megan's Robot Detection Module
• Sonars
• Arms

9 directions. First one is none (i.e. no obstacle). 8 Directions: starting at North in front of the robot, going in clockwise direction.

• detects which direction the arms are being pushed in
  
• if both arms pushed backwards, obstacle in front
• if both arms pushed forward, obstacle behind and etc.
• calculates direction based on arm displacement
• only accounts for one obstacle, if arms pushed into opposite discretions we do nothing because we are unable to detect where the obstacle is
• used when running directly into robots, otherwise not very useful.

method: run()

• runs every frame

• obstacleDistance[] -> tells us distance of obstacles from where we are in each of 8 directions

• obstacleDetectors[] -> tells us what module detected the obstacle (sonars, arms, vision) in each of 8 directions

• variables usingArms, usingSonars, usingVision let us turn off methods of detection for particular robots, e.g. V5s have unreliable sonars

• JSON file that sets usingArms, usingSonars, usingVision can be found in ObstacleModule.h

• if usingArms, processArms method is run; returns which direction the obstacle is in (enums in Obstacle.proto). returns position, distance and which detector *Obstacle.proto message used for obstacle detection in general *if usingSonars do the same thing for sonars

Information from Sonars and Arms is combined into one entity, information from vision represents a separate entity.

• if anything is turned off, we will use whatever information we have available

method: processSonars()

• add sonar readings to right and leftSonar lists
  

• if usingRightSonar and size of rightSonars is more than buffer, pop from rightSonars; same logic applies for the left. This is done so that we only look at the most recent 20 readings
  

• if using sonars, set right and left variables to the average value of the respective list. Otherwise the values are the upper sonar threshold and they won't be used
  

• if both left and right within threshold, lastSonar reading (global variable) is the average of left and right
  

• Division by 2 using bitshifts: number>>1
  

• Compute Average with bitshifts: a>>1 + b>>1
  

• then the obstacle is to the north, and distance is average of left and right readings

• if right sonar is picking something up --> obstacle to NorthEast. Distance = right reading

• if left sonar is picking something up --> obstacle is to NorthWest. Distance = left reading

• Once we've updated obstacleDistances and obstacleDetectors from arms, sensors and vision

We set the outportal messages, if distance is zero, ignore it: otherwise we have some obstacle detected

If we have an obstacle we create a temp obstacle and add it to the FieldObstacles message. Set position (i.e. direction) to the current index; set distance to distance at the current index; set detector to detector at current index and then set the message.