How do autonomous competition robots sense balls?

So, we’re doing some mini vex competitions in our school to prepare for the actual nationals, etc… We’ve made a maze and a follow line circuit… but we’d like to in addition to using a bumper sensor / distance sensor to get through a maze… be able to sense a ball and pick it up… is that possible with VEX? And with what sensors?

It is possible, but not always very reliable.

Option 1. Light sensor with a color filter. I have never personally done this, but i have seen it done to some small level of success. Make sure the color of the ball is significantly different from the surroundings.

Option 2. Ultra sonic sensors inside the grip to try and detect if there is a ball in the gripper. In our experience, the Ultra Sonic sensors are very reliable in test environments, but when introduced to the random noise of an actual competition, they can give a lot of garbage data.

Option 3. Limit Switch in claw to detect ball. Least likely to fail, but also does almost nothing for locating, only for identifying if it has or has not been located. Likewise with 2.

@Robo_Eng_13 Just thinking of VEX Worlds, I wonder how in the autonomous section of competitions how even in the first place they can even find a ball or cone!

Well a lot of teams don’t use the sensors to “find” the ball. Since the field is always set up in the same way, they know where the objects will be. They just usually program the robot to go and get the object and do whatever with it, since they already know where it is or will be

The cones start in predetermined positions and the robots are usually programmed to move to the position rather than find it

THERe are college teams that have used Lidar tofind object like balls, but not many use that technique

You can use a combo of sonar, touch, and color to try to find stuff, but there really just aren’t enough sensor ports on a vex cortex to use full on Lidar.

The amount of sensor ports is really not an issue. This was entirely done with a Lidar plugged into a cortex. And the sensor was around 80$. The code to read the sensor and detect cones / balls is explained here and is fully open source

https://vexforum.com/t/wpi-lidar-explanation/35017/1

Wait, so lidar is a single sensor? I thought it was a word describing the sum of all the sensors on your bot.

its like a radar that uses lasers

So I’d assume it’s not vex legal though

Not VRC legal but definitely VEXU legal.