Joysticks with circular motion

[The Lucas]

Originally Posted by Jared341

Do you need magnitude from the stick, or just direction? In the latter case you could use a continuous pot or encoder with a knob.

Originally Posted by Tom Line

We started out with that as one of our designs. However, we like to simplify the controls system as much as possible, and the joystick's integrated buttons made that chore much easier. We already have a knob for the left hand that sets distance for the turret system .

How about using the joytick's throttle, it will stay in place? If you aren't satisfied with the small throttle on the kit joystick you can buy a better one or just a USB throttle. My team uses the Saitek AV8R (Only $35 w/ free shipping right now) for the past 2 years. Its not circular, but has 5 axis (x, y, twist, dual throttle) and 12 well located buttons.

[JesseK]

Originally Posted by The Lucas

How about using the joytick's throttle, it will stay in place? If you aren't satisfied with the small throttle on the kit joystick you can buy a better one or just a USB throttle. My team uses the Saitek AV8R (Only $35 w/ free shipping right now) for the past 2 years. Its not circular, but has 5 axis (x, y, twist, dual throttle) and 12 well located buttons.

These things looked sick in person We could probably find a practical and intuitive use for all of those axes too, hmm.

[Tom Line]

I think I need to clarify a bit.

Our turret looks at the gyro and initial heading of the robot to determine absolute angle to the field.

If the joystick is pushed to the west - the turret turns and aims west. If the joystick is pushed north - the turret turns and aims north. Regardless of what direction the robot is facing.

That is why I need the circular range of motion joystick. Adjusting the gain of the turret for angles close to the x and y axis result in the turret being very slow in the corners because the joystick is much further from the center. Adjusting for the corners makes it touchy when the joystick is pushed in the direction of x and y axis.

Potentionally we could use an encoder and calibrate it - continous turn pots have too much of a dead zone to be desirable. However we have many functions that are tied to joystick buttons that are simply too late to change.

Perhaps we'll just machine a 2 part collar that will fit around the top of the joystick to limit it to circular motion.

[Jared Russell]

What do you do if (when) the joystick returns to center?

[Lil' Lavery]

Originally Posted by Jared341

What do you do if (when) the joystick returns to center?

Ditto on that question. I'm assuming it stays in whatever the last position it was told to goto was?

A "field-centric" turret control is possibly one of the coolest things I've seen done control wise in FIRST. A number of teams have done field-centric drives (especially holonomic and mecanums), which is perhaps even more daunting, but you're the first I know of to do field-centric turret control.

I don't know of any circular range of motion joysticks, and was unable to find one (although I did run into customizable joysticks designed for arcade machine enthusiasts, which may or may not be useful to you). Depending on how you have your code written (namely the return to center question), it might be possible to use a trackball though. You'd have to fine tune it for the trackball control and your driver would have to relearn the system, but it could potentially work well.

[Al Skierkiewicz]

Why not just use a pot?

[Jetweb]

We are using this joystick this year for our crab drive. It has a circular restrainer and works great. It even has twist.

http://www.logitech.com/index.cfm/ga...s/291&cl=us,en

[Joe Ross]

Originally Posted by Jetweb

We are using this joystick this year for our crab drive. It has a circular restrainer and works great. It even has twist.

http://www.logitech.com/index.cfm/ga...s/291&cl=us,en

Ours definitely moves in a square.

[Tom Line]

With regards to what happens when the joystick returns to center - the turret simply stays at the last angle it was directed to go to. We use the magnitude (the R value coming out of the Labview rect => polar coversion vi) to add a deadzone to the joystick.

Seeing this thing in action the first time (in our room) dropped the jaws of many team members. I have to give all the kudos to the two Junior programmers and the two sophmore programmers who did it. The math is far easier than I thought it would be when we started.

The neatest part of it was when we put the robot on a turntable. You could push the joystick in a direction and release it. From then on, no matter how you turned the robot on the turntable, the turret always pointed in the same direction. I was amazed.

It allows anyone to walk up to our gunner station and have intuitive control. Push the joystick toward the target robot, and you're on target. We're going to let judges play with it to see if they're as startled by the performance as we were .

Al - we considered a pot - like a 10 turn. However, I was concerned about what would happen in the off-instance where the gunner reached the end of the turns in a critical situation and had to spin it around the other way. I like trying to simplify and plan for every eventuality, and that created a problem I didn't want our gunner to have to deal with.

[EricVanWyk]

I'm really liking this idea - I hope I get a chance to try it.

Do you use |R| just for a dead zone, or do you also use it to vary the speed with which it approaches the intended direction?

Again, cool!

[Tom Line]

Originally Posted by EricVanWyk

I'm really liking this idea - I hope I get a chance to try it.

Do you use |R| just for a dead zone, or do you also use it to vary the speed with which it approaches the intended direction?

Again, cool!

We use R as the dead zone. We take the polar angle of the joystick, and compare it to an angle calculated from a 10 turn pot connected to the turret. We feed them into a PID loop that handles pointing the turret. It's generally within a degree of where you push the joystick, and gets full 270 degree rotation in 2 seconds.

Shooter speed is controled by a knob with foot graduations.

Again - I have to credit the programming team. The mentors said "wouldn't it be cool" and the team ran with it. I answered a couple of math questions for them, but I just watched over their shoulders while they figured out the "comparator code" to relate the angles.

I guess I'll spill the beans on the whole control system setup. The camera is mounted on the turret and constantly tries to track anything in the FOV that it can lock on to. However, it doesn't control the turret motions.

The gunner can pull the trigger and fire while aiming - that will fire balls with manual aim. Or pull the trigger and push the top button on the joystick while aiming. That allows the camera to take control of the turret - but only if it has a lock. The assumption is that the gunner continues to aim as best he can, so if the camera loses lock it immediately reverts to the angle the gunner is telling the turret to go to.

It took a lot of programming time to get the transitions between the modes seamless, but now you can barely tell when the gunner is using either method. The neatest part (I think) is that the gyro code that keeps the turret at an angle is tied into the camera code too - so if the bot turns, the camera has little trouble staying on target.

[Joe Ross]

Originally Posted by Tom Line

Al - we considered a pot - like a 10 turn. However, I was concerned about what would happen in the off-instance where the gunner reached the end of the turns in a critical situation and had to spin it around the other way. I like trying to simplify and plan for every eventuality, and that created a problem I didn't want our gunner to have to deal with.

This should work well: http://usdigital.com/products/encode...ary/shaft/ma3/

[Tom Line]

Originally Posted by Joe Ross

This should work well: http://usdigital.com/products/encode...ary/shaft/ma3/

Oh my. Maybe we'll play with implementing that between regionals.

[SmokeTest]

Team 116 uses the MA3. We also use the KOP gyro to give field-centric turret aiming. In addition, we put a simple toggle switch on the OI as a fallback (in case the gyro stops working) which gives our 2nd driver clockwise/counter-clockwise rotate controls. He told us last night that he actually prefers this to the field-centric knob, but I suspect he hasn't tried aiming the turret with the robot heading toward him (which reverses the relative aiming directions).

-Mike Youmans

[AmoryG]

Originally Posted by Tom Line

With regards to what happens when the joystick returns to center - the turret simply stays at the last angle it was directed to go to. We use the magnitude (the R value coming out of the Labview rect => polar coversion vi) to add a deadzone to the joystick.

Seeing this thing in action the first time (in our room) dropped the jaws of many team members. I have to give all the kudos to the two Junior programmers and the two sophmore programmers who did it. The math is far easier than I thought it would be when we started.

The neatest part of it was when we put the robot on a turntable. You could push the joystick in a direction and release it. From then on, no matter how you turned the robot on the turntable, the turret always pointed in the same direction. I was amazed.

It allows anyone to walk up to our gunner station and have intuitive control. Push the joystick toward the target robot, and you're on target. We're going to let judges play with it to see if they're as startled by the performance as we were .

Al - we considered a pot - like a 10 turn. However, I was concerned about what would happen in the off-instance where the gunner reached the end of the turns in a critical situation and had to spin it around the other way. I like trying to simplify and plan for every eventuality, and that created a problem I didn't want our gunner to have to deal with.

Our team uses a system similar to what you guys have, but the joystick doesn't rotate our shooter, but our whole robot's base. We have a crab drive, so our robot can rotate its base without affecting its movement.