Intake, “Out-takes” & Early System Integration

There’s a number of different ways to intake and manipulate Minerals in Rover Ruckus, and every one of them has its pros and cons. A big cliche we’ve been echoing around here is the concept of “touch to possess” or “touch it, own it,” which is a way of saying “once my robot touches this Mineral, this Mineral is mine.” This philosophy is especially important for games with non-alliance-specific objects, since robots on opposing alliances may end up battling for the same Mineral (and we always want to be the robot that drives away with the contested Mineral).

So, how do you do this? In our experience, the answer is always “something with a lot of grip spins, touches the object, and sucks it in.” Yes, there are other (and more elegantly described) ways to intake a Mineral, including (but not limited to) pinching, suctioning, and scooping. However, these generally do not gain active control as quickly as a roller intake. When using a roller intake, you typically do not have to care about orientation or size of the object, which is a big place where teams struggle. A well designed roller intake will intake Minerals as quickly as the robot can move while many other intakes require a second motion, such as closing a pincher or adjusting the drivetrain after contact has been established.

One commonly overlooked concept of intake design is active control. This is where the object’s position in space is controlled at all times by the robot. This generally means lots of rollers or conveyor belts, since you never want to lose contact with the object after you have gained control of it. (Losing contact with the Mineral can mean wasting time trying to shake the Mineral out of your scoring mechanism or robot as a whole.)

The third thing to understand when designing an intake is compliance. Something (either the object or the wheel) will have to have compliance or you end up with only two points of contact and a difficult time imparting energy to direct the object into your robot.

For soft objects like foam, we could use a hard wheel like a mecanum wheel or a traction tire. For hard objects like Minerals, we need to have compliant wheels such as VEXpro Flex Wheels.

Knowing all this, we began prototyping. First, let’s look at our list of requirements for our intake:

Intake

  • Touch to possess
  • Can pick up both Gold and Silver Minerals
  • Can hold at least 2 Minerals at a time

The most basic of all roller intakes is going to be a single wheel (or long bar of wheels) and a wall (or floor) to react against. This works, but Minerals acquired from a horizontal roller intake would still need to be funneled later in the robot-Mineral path. However, funneling is always precarious and can require a lot of tweaking and tuning to get just right. Another option would be for a wide, dedicated part of the robot to be used as a conveyor belt that dumps the Minerals out of the back of the robot. This would also work, but that’s a lot of space dedicated for something that needs to hold 2 minerals.

A simpler option is to funnel with the intake. This reduces complexity in the robot, helps us keep the weight down, and also makes designing the scoring mechanism easier since the Minerals will be neatly lined up inside the robot, ready for another wheel or something to pop them out the other end.

We did this by putting two 3”, 40A Flex Wheels on a spring loaded bar. This helps keep things center because the bars attached to the wheels always come back to center. Another thing this helps with is providing extra compliance to adapt to different object orientations. For example, if a cube (Gold) isn’t exactly square to the robot, the flexible arms can adjust to the wider shape of the object. This is pretty simple to do using some rubber bands and some hex standoffs.

We wanted to keep the acquisition zone as large as possible, so we decided to keep our intake wheels as exposed as possible. More wheel exposure = more likely to touch a Mineral = more likely to drive away with that Mineral in our possession. This means that objects that aren’t exactly centered to the intake opening can still be acquired as long as they touch part of the Flex Wheel.

This intake works pretty well! The compliance in the wheel and the intake arms absorb the sharp corners on the Gold, and the backstop forces the Gold to “square up” and form a neat line. We will have to experiment with the number of rubber bands we use and the hardstop location for the intake arms to get the perfect “pinch to flex” ratio.

If we look back at our list of requirements, this intake does everything we want:

Intake

  • Touch to possess (Check)
  • Can pick up both Gold and Silver Minerals (Check)
  • Can hold at least 2 Minerals at a time (Check)

Now that the intake is done, it’s time to focus on the Mineral Scoring mechanism. Our requirement for the Mineral Scoring mechanism was:

Mineral Scoring

  • Depot-only
  • Scores from the opposite side of intake

We weighed a couple of ideas for this. We first looked at using a number of Flex Wheels through the robot. However, we were concerned that this would end up being a lot of unnecessary weight for not a lot of gain. In addition, this type of a system would require more pinch on the object which means more load on the motors. Remember, we’re trying to get away with 4x motors and 8x VEX EDR 393 Motors. So we were worried that this type of a mechanism would require us jump to regular motors.

So we looked at using the VEX EDR Tank Tread system and the flaps that are available with the Tank Tread Upgrade Kit. The benefit of these is that they easily integrate with a VEX EDR 393 Motor and the flaps don’t have to compress the object as much to use it. This means that there’s less load on the 393 motor.

Out initial concept was to use two sets of tank treads side by side, with the Mineral sitting between them. Then we realized that this could be achieved with even less weight with a single over-the-top tank tread.

We mounted it on our drivetrain to see how this type of system would work:

One cool thing we found with this setup is that we could actually roll balls from the Crater to the Depot. This isn’t going to be very effective as someone could easily stop a ball as it’s rolling. However, this could come in handy late in a match when you don’t have enough time to leave the Crater and hang. Instead, you could roll a couple balls for some last second points and still get 25 points for parking completely inside the Crater.

Next it was time to integrate the intake and the Mineral Scoring mechanisms. This took some tweaking, but the early results look promising: IMG_1486
(Sorry, we can’t embed this particular video. WordPress can be a pain sometimes)

That’s 47 Minerals out of the Crater in a minute. Yes, there were a few times we had more than 2 Minerals in the robot, but this is a promising start for our robot. Next we need to get a control system on the robot so we can run the entire robot and see how it can be improved.

As you’ve noticed in our two other posts from today we use a lot of parts from the VEX EDR and VEX IQ systems. The reason we’re doing this is because we’re trying to quickly iterate through ideas. As the final robot comes together, we will start integrating in more VEXpro parts to strengthen and reinforce weaker parts of the robot. Our goal is to try and get a robot up and running quickly so we can spend more time iterating and fine tuning the robot’s performance.