Vision Tracking and Movement

[Triapod]

Autonomous -
Our programming team has not yet programmed using vision, but have taken a look at the default code given to track circular objects. We think that this system works great and are wondering how to move forward to program movement towards the ball. We wish to move towards the ball but not hit it (stop right before it) then activate the pneumatic kicking system.

We are wondering if we would be able to be able to determine distance to drive, or have to use a sensor.

Thank you

[DavidGitz]

We experimented with using the camera to detect distance to the target/ball, but it just isn't accurate enough (can someone correct me?). You can use dead reckoning, i.e. drive for a certain period of time and then stop since you can place the ball where you want, or you can use a sensor. Some teams are using ultrasonic sensors or IR sensors. The control system documentation goes into how to use an ultrasonic sensor for this purpose.

[Triapod]

Won't this system (timing/distance) be highly inaccurate because the distance we place the balls apart may vary? Using a sensor places near the kicking system may work but being near the high power area may cause damage to the delicate machinery like the limit switches.

[Triapod]

Have you tried using the ultrasonic sensor. How accurate was it in determining the distance of the ball. Dead reckoning seems to be too inaccurate in that the distance between the balls could vary making the effectiveness of the kicker less. The ball could also roll.

[nathanww]

If you're really worried about accuracy, a three-stage hybrid system might be useful

1.The robot tracks the ball using the camera
2.When the ball becomes too close to track, or if the camera loses it, the robot moves into dead-reckoning mode
3.When a broken-beam sensor is tripped, the robot stops, kicks, and can start the cycle over again if neccesary.

That said, the balls don't move that much after they're placed. Dead reckoning is very susceptible to random variations in hardware, but a good encoder or inertial nav system can fix this.