Force Feedback

[Andrew Blair]

Has any team constructed a FIRST legal force feedback system for competition? Obviously the problem is getting the feedback motors to run off the operator interface, if that's legal. I would assume with two accelerometers placed 90 degrees from each other, you could get the feedback relatively easily (the feedback only, I hear the sensors are real pains). The last problem I see would be the charge generated by the motors while you're moving the inputs. Could it affect the system in any way I wonder?

[Tom Bottiglieri]

I'm guessing you mean force feedback as some sort of "rumble" device in the operator's control... thing.

[Rickertsen2]

by force feedback do you mean something that vibrates or something that actually resists your movement. I have thought it might be kind of neat to use either style of feedback to communicate how much current the motors are drawing. An accelerometer could work too. I I definately think its a worthwile endevour.
The only ways to communicate back to the OI are through the dashboard port and the LED outputs.

Reading the data off of the dashboard port isn't hard but you need a microcontroller for it.

The other approach is to use the LED outputs. By themselves, these can't source enuogh current to drive a vibrating motor, but you can easily build and amplifier for them.

Now this brings us to the issue of where to get power. Its not available in a great enough quantity from the OI, so you will need an external power source. A battery will do.

As far as the legality of this goes i don't know for sure but i can't think of any rules off the top of my head that it violates. It seems to me that a vibrating motor is the tactile equivalent of and LED.

There are some people somehwere on this forum that built a playstation controller->gameport adapter. I am waiting for them to release the source for this. Once they do, it would be pretty nifty to add force feedback support.

[Al Skierkiewicz]

Many teams have tried in some way to get around the rules on this but the rule book is pretty specific about hooking things to the OI. I don't think that will change in the future but it would be pretty cool. Of course, one more thing for the electrical and software teams to do. If the OI at some point in the future added a few open collector or opto isolator outputs capable of some current and if the rules committee were to allow a second power source at the OI this would turn out some very interesting ideas.

[ahecht]

Originally Posted by Rickertsen2

Now this brings us to the issue of where to get power. Its not available in a great enough quantity from the OI, so you will need an external power source. A battery will do.

As far as the legality of this goes i don't know for sure but i can't think of any rules off the top of my head that it violates. It seems to me that a vibrating motor is the tactile equivalent of and LED.

Once again, FIRSTSearch comes to the rescue:

5.3.8 - THE ROBOT>ROBOT RULES>Operator Interface Rules
<R69> All equipment connected to the Joystick Ports of the Operator Interface must be powered solely through the power available through the port. External power sources of any type are not permitted on any equipment connected to the Joystick Ports. Portable computing devices may not be connected to Joystick input ports on the Operator Interface.

[Jeff Rodriguez]

Regardless of the electronics and whether or not it can be built, how would it work?
Would it simply resist any movement of the joysticks and push back?
Or would it push back when the robots movement is being opposed, i.e. in a pushing match with another robot? Could you do this by comparing the value from the joystick (what the robot should be doing) with perhaps the accelerometer (what the robot is doing) to come up with how much the stick should be pushing back?
If it did give real feedback, would it be useful or just another obstacle for the driver to overcome?
For example, you are face to face with another robot trying to push each other. If you have true feedback, the joystick would be pushing against the drivers movements. Wouldn't that keep the joystick from staying at it's maximum, essentially giving the robot less power and losing the pushing match for you?
I suppose that you could limit the amount of force feedback, but at what point does it just become a nuisance?

[Rickertsen2]

<edit> fixed misquote </edit>

Originally Posted by ahecht

Once again, FIRSTSearch comes to the rescue:

well, that pretty much rules out any sort of Force feedback. In order to have force feedback, you need power. Without power we are stuck.

Originally Posted by Ogre

If it did give real feedback, would it be useful or just another obstacle for the driver to overcome?

I have a force feedback joystick that i use for certian games and i have never found the force feedback to be a nuisance but rather helps immerse the operator. It never gets soo strong that you cannot overpower it or so that it significangly throws you off course.

[Andrew Blair]

^(Rickertsen2, you got your copy paste screwed up. I think Ogre said that, not me)

Well, even if it can't be done legally, it would still be interesting. First of all, I mean actual, dynamic force feedback that helps show the driver where he's being pushed. Accelerometers would be the device of choice, placed 90 degrees perpendicular to eachother, so as to provide x-vector and y-vector. In the joysticks, there would simply be a small motor attached to the appropriate axis via a belt. When you got hit from the side, the x-axis would jerk accordingly in parrallel. Programming it directly would be very simple, accelerometer_x=x_motor, I think. However, I would think some kind of filter would need to be in place in order to keep the feedback from actually controlling the robot on it's own, to distinguish human inputs from ones just sent to the feedback system. As for it jerking out of your hands, probably not, as it would be a small motor with a belt that would slip against much backpressure.

I'm wondering if you can get power from the joystick outputs/inputs. It would seem to me that you could run a small, albeit small motor off 9 volts, 1.5 amps. Actually, thats quite a bit of power, if we could get to it. If I remember correctly you can run LEDs from them. Correct me if I'm wrong please!

[Alan Anderson]

You're not thinking far enough outside the box, folks. Remember, there's more than joystick ports on the OI.

[Andrew Blair]

Originally Posted by Alan Anderson

You're not thinking far enough outside the box, folks. Remember, there's more than joystick ports on the OI.

Aha! You mean splicing out power from the competition port, then running a motor controller to it, controlled by outputs from the operator interface? Seems complicated, but maybe the only option.

Or maybe not.....


-------------Edit-----------------------------
Nope, no good.

<R69> All equipment connected to the Joystick Ports of the Operator Interface must be powered solely through

the power available through the port. External power sources of any type are not permitted on any

equipment connected to the Joystick Ports. Portable computing devices may not be connected to Joystick

input ports on the Operator Interface.

<R70> The Competition Cable at the Alliance Station must connect directly to the Competition Port on the

Operator Interface. No intermediate connectors, cables, or “pigtails” are permitted.

[Alan Anderson]

Originally Posted by Andrew Blair

Aha! You mean splicing out power from the competition port,...

Nope. As the rules you quoted say, tapping into the competition port is not permitted during competition.

So if you need more power than you can get from a joystick port, and you want to control something on the OI using software on the robot, what's left?

[Billfred]

Originally Posted by Alan Anderson

Nope. As the rules you quoted say, tapping into the competition port is not permitted during competition.

So if you need more power than you can get from a joystick port, and you want to control something on the OI using software on the robot, what's left?

Relays?

[Andrew Blair]

A giant Tesla coil that can transmit electricity through .25" Lexan!! No, I really have no idea.......You can't generate the power while your there, like with a little spinny wheel.

[DonRotolo]

Originally Posted by Andrew Blair

I'm wondering if you can get power from the joystick outputs/inputs. It would seem to me that you could run a small, albeit small motor off 9 volts, 1.5 amps. Actually, thats quite a bit of power, if we could get to it. If I remember correctly you can run LEDs from them. Correct me if I'm wrong please!

According to IFI "The current limit of the +5V Aux from all 4 ports is about 100mA. The Aux Fault Led will start illumination when the current draw from the +5V Aux Outputs total about 120 mA and the +5V Aux voltage will have dropped to about 4.5 volts. Worse case, short condition: after about 30 seconds, the voltage will be at about 300 mV with a current of about 250 mA."

Now, I don't know if that means 100 mA from each port, or 100 mA from all four combined.

Don

[Andrew Blair]

How does storing current on a capacitor work? I know that the voltage out will not exceed the voltage in (ex: 5 volt cap. with 2.5 volts applied will charge to 2.5 volts), but how does current charge?