Is lifting worth it?

This year is interesting, because you need a completely separate mechanism to achieve bonus points.
In tossup and roundup, you could just use your normal lift to pull yourself up, and in sack attack, you just needed to go back to your starting tile. Most teams this year need all 12 motors just to keep up in ball scoring, so sacrificing 2-4 motors, a lot space, and 20 seconds at the end of the match, could diminish scoring significantly. Currently, I think that a really fast low lift that doesn’t get in the way of scoring would be better in most situations. I’m sure that the higher level teams will have a 1 motor high lift that only takes 10 seconds, and doesn’t have any of the drawbacks of a ramp by worlds. But for the rest of us, is it worth it?
The only evidence that I have is that back in tossup, if both alliances were tied with 20 seconds left, the 2 second low hangers normally beat 10 second high hangers because they had more time to keep scoring.

At high level competitions it will be worth it.

Care to add to that very thorough point? :stuck_out_tongue:

Lifting is mostly a back-up plan. We used 4 motors for our x-drive, 1 for our intake, 4 for our flywheel, and 2 for our lift.

We think so. We are finishing a mechanism on our robot that will allow us to either low or high elevate depending on the need of the match. We are able to do it without any additional motors, so we feel like we didn’t really make any “trade offs”. The hardest part was getting it to fit on our current robot but we are almost done. We will probably make a reveal right before our state competition (Mid January)

You don’t necessarily need power, much space, or 20 seconds.

I know, this thread is about the average teams, not about the best, most experienced teams.
That’s why I included the part about the best teams all having 1 motor high lifts that only take 10 seconds.

Well then I guess we might just have slightly differing views on average. I mentor IQ teams. It has taught me to never call any team average, simply because virtually all teams have tremendous potential if only 1 or 2 members are passionate enough about robotics to the point that it invades virtually every second of their life.

In my opinion, any team can have a viable fast high elevation.

I completely agree with everything with what you said. When I say average, I don’t mean that they’re any less determined. I mean less experienced, I think that I have potential (maybe), but I don’t have enough experience to win a competition. By my definition, everyone is average until they begin to dominate. I know that it isn’t the correct definition. I joined vex this year, so did my teammate, and it has taken over my every waking thought. I consider my team to be average, because we can’t dominate on the court.
I’m sorry if what I said was in any way demeaning to anyone.

I understand what you are saying about average teams and I completely agree with you. There are some schools at all of the competitions I have gone to that seem like they (at least a few members) have the compassion to do well, but their lack of experience holds them back.

To get back to the original question, I think lifting will be very effective at the state/regional level at determining important matches such as some elimination matches. I currently am trying to create a low lift that will not take up motors or pneumatics. I feel like if I get paired with someone that can high lift I will be compatible with most of them so as a back up option I will try and low lift (especially in Qual matches in which the partner is random)

From a theoretical standpoint, if you want to be #1 on qualifications at worlds in the high school level, I would argue no, you don’t want a lift. Instead, if you’re trying to be that #1 team, you should do excellent scouting to find that team with a compatible lift system.

In this game, there are only 2 tiebreakers: The autonomous bonus, and the field balls. Whatever alliance can dominate the majority of these points are guaranteed to win under the scenario all independent points (both loads and lifting) are earned.

Of the autonomous bonus and field balls, field balls takes priority. From an engineering perspective however, that means that you need to build a robot with superior speed to get to balls, collect balls, and shoot the balls out.

However, every robot can only be built with so much power, and theoretically, every robot can be created equal. However, the moment that you sacrifice some power towards a lift system, you sacrifice power from the drivetrain, intake, shooter, or some combination of those systems, which then lowers your performance in collecting the field balls. This point is proven in matches where neither team elevates, and all preloads can be scored. Assuming both teams have the same accuracy shooting the driver control loads, we see that teams who score more field balls win. With 2 extra motors on the drivetrain and a lighter system due to no lift, and since most teams use a 4 motor drive, your robot should be 1.5 times faster, giving you the edge in elimination rounds

Now back to the tiebreaking perspective. Tiebreakers only matter if the case is a tie: That means elevation points are canceled out, and loading is canceled out. So that means one assumption i’m making is that a majority of teams can first meet a draw.

However a complicated scenario comes up if you end up not having an elevation alliance partner and face someone with an elevation partner in qualifications. Now assuming everyone is at their theoretical best, (that means that since you and your alliance partner doesn’t have elevation, your alliance partner also specializes in collecting field balls), Your alliance will collect 6 stacks, and your opposing alliance will collect 4 stacks, what the match will come down to is autonomous bonus or a tie.

Though theory is nice, I would stop the debate at whether an autonomous elevation is viable vs shooting 2 more stacks is viable. From a practical scenario, I don’t think an autonomous elevation will happen because of how difficult it’ll be to predict your alliance partner, instantly de-elevate, and even develop autonomous programs for each other

Other things to consider are skills rounds. There, a partner lift is pointless

That was exactly what I was trying to say, but @DracoTheDragon put it so much better then me.

I’d say lifting is definitely worth it. 50 points is a big deal. First, consider not using 12 motors if you are going to go for a quick lifting robot. Use 10 motors and pneumatics. From what I’ve seen pushing is not a big factor in this game–maneuverability is. So a holonomic drive (x-drive) would be great–it adds both speed and maneuverability to your robot, in addition to more accurate turning for programming, which is especially important for this game where you need to be pointing the right way when you launch. That’s 4 motors–6 motors doesn’t work with nearly all holonomic configurations and 8 is too many. And having a super fast robot is not as awesome as it sounds–you have less control over small movements–another thing important in aiming; and you shouldn’t be driving back and forth across the field to pick up and score balls, that’s wasted time and power. 4 motors for a launcher–plenty for any flywheel and single catapult/puncher, maybe for a double catapult, that’s not something I’ve seen teams in my area try. That leaves 2 motors for an intake/ball sorting–again, plenty. Now you’re lifting mechanism can be completely pneumatic–there’s no reason to rely on two motors (unless of course your team doesn’t own pneumatics, but we’re assuming they do) when pneumatics provide faster and stronger actuation.

So I guess this is my ideal robot with elevating capabilities: 4 motor holonomic drive, 4 motor launcher (probably a flywheel), 2 motor intake, and a pneumatic lift. Elevating shouldn’t take more than 5-10 seconds or it’s not worth it with teams that have good launching capabilities

Building Vex-U bots, I’m just adding the two extra motors onto the launcher to reduce time between launches.

Pushing can be important when defending against teams that can only shoot from certain positions on the field. A quick push/bump can throw off a shot and make them waste time realigning. A fast robot that can shoot from anywhere on the field can be devastating by quickly clearing the field balls. There have been a few matches at recent competitions where all the balls were scored or off the field with 25 seconds left. At that point lifting is definitely important.

Use a gyro for turning and you can make accurate turns with any type drive.

Though this is not completely on topic, we should note that Vex U regulations completely change the engineering challenge. In Vex U, we are not under the standard power limitations of high school, meaning that we can use pneumatic PTOs and transmissions to change the entire power game. The problem with pneumatics and 10 motors is that it sacrifices your ability to have a superior subsystem for the development of an add on. You can’t build a 6 motor drive without taking 2 motors from your shooter, etc.

As mentioned before, a gyro is what makes things accurate. The accuracy of a gyro is not dependent on the configuration of a drivetrain. A drivetrain is simply a configuration of how you choose to set your forces. It’s up to your programmer to tune that.

That is true if you simply have “motor[drive]= vexRT”. Teams do not need the in between power. Because of this you want to implement a power curve. This will make it so the last values will give you full speed while a majority of the joystick is tuned for medium to low power

Which is true. However, the best field oriented robots don’t need to drive back and forth. They can simply shoot from where they are positioned, which again, is programming (or driver practice).

Pneumatics are faster, but I would debate stronger. A motor has an effective 7.3 inch pounds of torque (14.6 stall), but you usually gear them around 5:1 for an application like this for about 36 inch pounds. A piston is equipped with 12 pounds of force which is difficult to apply mechanical advantage because of the limited 2 inch actuation. Even then, you have to be careful not to bend the piston itself. If you bring elastic into the equation, they both are equal since usually that means either component is used in a locking system.

The problem with your argument is that it uses a bottom up basis. By taking the assumption that lifting is worth it, you then try to prove it with what you know. Instead, you have to take what is certain (scoring methods, physics, math) and use those to discover what the theoretical is.

Of course, there are practicalities you have to consider to get the most accurate result. This makes things hard because we have to gauge what the average team can do

At this current point in the season, I do not feel that lifting is worth it for most teams. This is because the time used to lift in a match can be used for scoring balls, and the time used to develop a lift can be used to improve a shooting mechanism. 5 balls in the high goal will offset the high elevation bonus. If a high elevation takes 10 seconds, then the other team needs to average .5 balls per second to counter your high elevation bonus, which most teams can do. If you can score while remaining high elevated, perhaps with a turret and driver loads in 30 seconds, then it’s worth it, but that time, again, can probably be better spent improving the shooting mechanism’s rate of fire or accuracy. However, by state championships, fields will be cleared most of the time with enough time to lift, so lifting won’t reduce time spent scoring. We are already starting to see this at some competitions. Also, to solve the issue of not enough motors, remember, rubber bands are free power (that is, or was, someone’s signature, but I don’t remember whose it was, so thanks for the advice).

VexU rules do not change the game as much as you might think. What do you mean with the standard power limitations of high school? VexU teams are still only allowed 12 motors, two batteries, and two pneumatic reservoirs. Why can’t high school teams use PTOs and transmissions? My argument is that teams do not need a “superior subsystem,” and the point that I was making with that comment is that I’m using pretty much the same strategy in VexU.

So how the robot is built doesn’t affect precision and accuracy? Gyro’s do not inherently make a robot’s programmed course more accurate–they require a decent amount of programming and accounting for drift–something gyros have a lot of. In addition, how you “set your forces” has a very large influence on how accurately that force will be directed. Similar to how a holonomic drive moves forward inherently faster than a straight-wheel drive, holonomic drives will turn slower than a straight-wheel drive, thus giving more control. Forces are also in line with the net direction of movement and have a more direct ratio of input power to output movement.

Even with a power curve, a robot with geared-up drive train will have less control, which is the point I am trying to make.

Unless, like team 323z, you have a way to measure your location on the field relative to the net, teams are only going to have between something like 1 to 4 shooting distances. It’s impractical to have a different button to set the correct launching distance for each spot on the field. Again, you’re missing my point. Balls tend to collect in certain areas of the field and teams should just collect, turn, shoot, turn, collect, turn, shoot, and so on.

Pneumatics can be put on levers to gain a mechanical advantage. Also, you can use as many pneumatic pistons as you like, each one providing 12 pounds of force. So say you have 6 pistons each with 12 pounds of force for a total of 72 pounds of force. 2 motors would have 14.6 pounds of force total. 72 > 14.6 I think. Add more pistons as needed, you only need to elevate once.

Not sure what you’re talking about. I put forth my thesis then supported it with evidence and analysis. What is “certain” is different for each person.

Are we making the assumption that we are working with an “average” team? What is “average?” I was talking about what I expected a team who wanted to be above average to do.

I Agree

I have seen many good teams not waste their time on building an elevating system because they did not see it an essential task to win matches (and it wasn’t). We will have to wait to see more robot designs that can score effectively and elevate quickly.
Although, I have seen a few matches here in Texas recently of teams winning high scoring matches due to elevating. I don’t think it will be long till we see elevating being a key factor in winning the match.

My bad. By power limitations, I meant that high schoolers can’t use both 12 motors and pneumatics

Correct, however I am arguing that they do need a superior subsystem because it will give them the edge in elimination rounds if they have an alliance partner that can lift. However, a superior subsystem is not possible without 12 motors

Yes you are correct in the manner that how you set your forces will change how fast or how slow your drivetrain will be. However, your limiting factor on how accurate is not based on speed/force/power. It is based on how the gyro is programmed, which is what you said (bolded). What you could be implying is the speed which it takes to get to the angle, but not how consistently it gets to that angle.

However, you continued on to say that drivetrain power matters. It does not, assuming the robots have the capabilities of moving.
For example, let’s say we want to aim for 45 degrees. You create a PID loop and tune it to get to 45 degrees. If the robot overshoots, then it corrects itself using drivetrain power. If your robot is using too much power, then you change the actual power values. Eventually, you will change the values enough that despite the set up of the drivetrain, accuracy remains the same (even though the difficulty will vary). Similarly, if you want to program a flywheel velocity, It does not matter if you have 6 motors, 4 motors, or 2 motors, nor does the gear ratio matter (plus or minus backlash). As long as you have an encoder which can record the values you are aiming for, it’s up to programming to determine how accurate you can get, not the power of the system.

I don’t see why a geared-up drivetrain would have less control with a power curve. Theoretically, due to the power curve, it would move with the same speed a driver would have with a lower gear. Is my assumption that control is only dependent on the speed of the robot wrong?

Not sure where you first mentioned balls accumulate in one area. But either way, then apply 323z’s code.

Hmm… I did not consider multiple pistons. However, let’s say a majority of the competition is heavier than 12 pounds. So neglecting friction, you would need 2 pistons. Each piston is only capable of 2 inches of actuation, and to get a high elevation (to tie with a superior subsystem), you would need 10.5" of actuation. So that means you need 6 sets, making 12 pistons total. I’m not too familiar with pneumatics, but I think that would take every digital port in the cortex. I’m not sure if you can y-cable solenoids. If you can’t, then you lose your encoders.
Not to mention, 12 pistons? You might as well save money, apply a motor, and gear it for the torque you need, or just rely on elastics.

In my post earlier though, you might need to elevate multiple times in order to get the autonomous bonus, and actually get the 50 points at the end of the game. But as I mentioned before, that scenario is really foggy.

My assumptions were using the theoretical best. However we don’t know what the target audience’s skill is.

Why does it give them an edge in eliminations?

What do you mean accuracy remains the same while difficulty varies?

The robot is still going to be faster; I did not mean that the power curve gives the driver less control. It does give the driver more control, and should probably be used on both slower and faster drives. I’m saying faster robots are harder to control in general. You’re assumption is completely correct.

I didn’t actually mention that at first. And it’s not in just one area, there are areas on the field where balls accumulate–they vary between matches, but it’s often the corners and in front of the goals. And it’s not just as simple as applying a code; that’s not something most teams have the capability of effectively implementing. It also has yet to prove itself (from what I’ve seen).

Why 10.5 inches? High elevation is 12 inches. You need to make 2 inches translate to 12 inches. So a lever that is 6 inches long on the side lifting the robot and 1 inch long on the side attached to the pistons (Because attachment points have to be at least a quarter inch from the ends, the lever would actually be like 6.5 inches and 1.5 inches on each respective side). Also, couple rubber bands with double-acting pistons and you probably only need 6 pistons. Assuming 6 double-acting pistons with rubber bands provides 72 pounds of force (it would actually be a little less, but adding one or two more pistons wouldn’t such a big deal) that would provide 12 pounds of force on the end of that lever. Technically you could y-cable all 6 of those solenoids to one port and it work fine, but Vex has this stupid rule that says you can only y-cable 2 solenoids to each port. So that would only take up 3 ports. That’s actually a pretty small mechanism that only takes up 3 digital ports. If you really needed digital ports, all 6 of those pistons could be run off one solenoid, meaning it would require 1 digital port.