Joysticks with circular motion

[Tom Line]

We are using our joystick to control our turret. However, like most joysticks manufactured today, the joystick has a square restrictor that forces a square motion. Short of opening the joystick and machining a restrictor to allow only circular motion, is there another joystick currently on the market that is set up this way for USB and is a reasonable price?

The square motion causes issues with aiming the turret - when you are in one of the corners you have fine control and your amplitude is larger. When you are in either the x or y axis, however, the turret is more sensitive because your distance from center is smaller and a change creates a larger actual angle change (we convert the joystick to polar coordinates).

We really don't have time to change what we have, but perhaps we can be ready for next season.

[Jared Russell]

May I ask why you need two joystick axes for turret control?

For example, our turret is controlled solely by the X axis of the operator's joystick. Alternatively, you could use a stick with a yaw axis (Z or twist).

[Tom Line]

Because we have our joystick set up to handle the turret similar to how crab is programmed - push in a direction and the turret turns to that direction.

[Jared Russell]

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.

[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 .

[Bob Steele]

I would suggest that you use one of the joystick controllers that allows yaw control by twisting the joystick.

We use this to control our crab/swerve drive... twist one way turn that way
twist the other way and turn the other way...

Just make sure and find one that will work with the present system.

[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.

[Lil' Lavery]

Originally Posted by Bob Steele

I would suggest that you use one of the joystick controllers that allows yaw control by twisting the joystick.

We use this to control our crab/swerve drive... twist one way turn that way
twist the other way and turn the other way...

Just make sure and find one that will work with the present system.

I concur, a three-axis joystick with the z "rotational" axis being used to "throttle" would seem like an ideal method. The problem is that 3-axis joysticks are often made for industrial purposes, and tend to be pricey. A quick google search only yielded a few results for 3-axis USB joysticks.

edit: see below.

[Cory]

Originally Posted by Lil' Lavery

I concur, a three-axis joystick with the z "rotational" axis being used to "throttle" would seem like an ideal method. The problem is that 3-axis joysticks are often made for industrial purposes, and tend to be pricey. A quick google search only yielded a few results for 3-axis USB joysticks.

Really?

I have a Microsoft Sidewinder from ~10 years ago that has the twist function on the Z. It couldn't have been more than $50 then.

I'd have imagined that would only be more widespread now than in 1999.

[Joe Ross]

Originally Posted by Lil' Lavery

I concur, a three-axis joystick with the z "rotational" axis being used to "throttle" would seem like an ideal method. The problem is that 3-axis joysticks are often made for industrial purposes, and tend to be pricey. A quick google search only yielded a few results for 3-axis USB joysticks.

We're using the Logitech 3D pro. The joystick Brian linked to earlier has it too.

[Lil' Lavery]

Hmm, perhaps I should have searched amazon/best buy/etc instead of google. I see that there are a number that I was unable to find.

[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.