Steering rig start

[h106frp]

Nice idea, but probably a bit complex for a safety device.

Just thinking out loud, but trying to get a handle on motor gearing/power/ and torque for a controller.

Referencing consumer items..

From an owners practical tests.....
G27 wheel 3Nm
T500 Wheel 6Nm, 30 cm wheel, 65 watt motor - i guess its quite a high gear ratio 60:1 or so for this torque from a small motor

My smaller steering axis motor is 150 watt and should be 12 to 14Nm  at about the equivalent to a 600mm 'wheel' using just the 25:1 gearbox with no extra pulley belt gearing... It is feasible to add another 2:1 on the gearbox output to raise it to about 25Nm but i would rather the response does not get too lethargic.

Be nice to get it all mocked up and see how it feels for real but i need to manufacture an adapter between motor and box first  then i can get a real feel for the response profile of the bars steer axis

So.. it should feel similar to the T500 wheel for force/torque with just the gbox, does anyone have a t500 wheel, and if so, how does it feel for torque? sufficient for gameplay?

Thanks

[teeds]

For the kill switch maybe think about the jet ski kind of thing. A short cord and peg from wrist to a sprung switch, remove your hand from the grip and it dies.

I have a T500 and turn it down for anything but a demo of the FFB, it's a real work out on full but nothing a grown man couldn't overpower.


Looking sweet btw 

[h106frp]

Thanks for that info, measuring up the actual span of the bars at around 500mm i'm probably the equivalent to another 25% better in torque than i first estimated  so with your impressions of the T500 i feel a bit more confident with going direct drive from the box which will simplify things

I had not considered a lanyard, that may be a very good quick acting solution, thanks.

[Ddinit]

For the kill switch maybe think about the jet ski kind of thing. A short cord and peg from wrist to a sprung switch, remove your hand from the grip and it dies.

Hi teeds maybe you think something like that ? 

[doubledragoncc]

The lanyard is not quick enough to stop an injury from happening it has to be far quick response than that. You need a physical limiter switch for rotational direction and speed of rotation. It depends on how the actual framework is designed and the end points of movement. If I had a pic of the framework design and the motion directions I could say more.

DD

[h106frp]

Hi DD,
Both axis (will) have large physical travel stops and limit switches, what i am after is a way of making it stop if it has a software 'fit'. The scenario i can see is that something happens in the sim software (where i have no control) to generate an extreme cyclic range of movement - the moving rig contained safely within the physical stops and travelling between servo limits- and i really want to stop the motors as soon as you let go of the bars as with no restraining force the movement could suddenly become more excessive. The lanyard idea seems ideal for this as it physically connects the user action with the kill function.

As for the framework that idea is still evolving  its a bit 'make it up as you go along' and waiting until i have sourced all the big bits to decide. I could not really draw it up as i am just using whatever materials come to hand at the moment to keep the costs down Sort of getting there now though and a proper frame may be the best way to sort out the horizontal drive motor mount (it still look huge  ) as i suspect this might need to be strong but lightweight.

Got the steer axis motor and box joined together and i am quite pleased with the result. Seems powerful but fairly compact. Hopefully get it 'in-situ' soon and finally get a feel for the bar forces  Just hope it works as i am expecting after all this effort.

[HornetMaX]

At the risk of being Cpt. Obvious, 2 trivial things:

• Put a limit on the current that can be delivered to the motor. Ideally, this should be in the hardware/firmware.
• In GPB output plugin, there's an indicator (m_iCrashed) that tells when the rider is no longer on the bike: as soon as this goes to 1, just stop everything.

MaX.

[h106frp]

Current is controllable in hardware so i can limit the force but we will probable need to operate with high torque (current) for a convincing steering rig model in torque steer mode as discussed previously. For simple FF mode the torques could be set lower.

I will add software controls, but it is dependent on totally bug free software which will not happen until it been debugged, so i need a solution for this phase at least.

I think the lanyard will work, i can safely limit rig travels, its just that transition from hands on to hitting the e-stop that might cause problems. Its not such an issue with a wheel, it just spins but with bars and levers on 2 axis it could become a bit of a 'flail' and thats why i am being cautious. I am confident that once its built and the software sorted it will be fine and safe - its mainly during testing/development that i have concerns.

[doubledragoncc]

The lanyard would be good but I would suggest making it to the right wrist to reduce the amount of movement needed as one to the body will have to much play to be safe, also your throttle wrist is the least likely part of your body you would move away from the system during use.

DD

[h106frp]

Got the steer motor and box onto the steer shaft, i think it looks quite  .




After a rather 'uncontrolled'  experiment (just could not resist) i am now quite happy that this is more than powerful enough for initial tests, but it does need the steer axis to motor base plate sorting before i try anymore powered tests. This thing can 'whip' the bars across just as fast as suspected - looks like it could be lot of fun when its done
Balance feels good so far and the load (inertia) on the roll axis shaft is very low  .

[h106frp]

After deciding (being informed ) that having hydraulic fluid in the house was a bad idea and struggling to fit in all the cylinders/pipes/sensors etc anyway  i have revisited the brake sensor concept and remembered DD suggesting fitting something directly into the master cylinder space itself - inspiration .

Dismantling the brake levers i have found plenty of space in the radial type design and replaced the 12mm diameter pistons with home made load cells using silicon strain sensors. I added a small sprung section to the top of each cell to give a little bit of initial travel made from the original piston parts - it felt odd being solid at the initial lever travel. The wires lead out through the opened out fluid outlet port. Another small spring keeps the radial lever push rod in light contact with the sensor. Rest of the mechanism works as originally intended and retains the adjustable lever reach mechanism.


Instrumented load cells designed to replace master cylinder piston 12mm dia

Feels great, and has that familiar brake like feel, small initial start and then loading the sensor directly. The sensors are giving about a 10 ohm change for a sensible lever pull so the electronics should be straight forward using a simple bridge and op-amp.

[HornetMaX]

Sorry for being hardware noob, I'm not sure I get it.

Essentially, your "piston" is not moving and you're measuring the strain on it ?

MaX.

[h106frp]

That how it works - the fixed load cell replaces the piston and is squashed between the end of the cylinder and the push rod that comes down from the lever. The radial master cylinder and lever seems ideal for this approach. The little pin and spring are fitted into the end of the cell to allow a little lever movement with only the spring rate loading the cell, once this bottoms out all the lever load is applied directly to the top of the load cell - it just allows for a more natural lever action.

It is just a very simple column load cell so its just measuring the compressive strain applied by the push rod - the silicon gauges give about 50* the resistance change for a given strain than the more familiar foil gauge so the electronics are a bit simpler.

[HornetMaX]

OK, thanks.

Sounds very good. GPB even has a "gain" slider, that could be handy to tune the whole thing.

Very promising !

MaX.

[doubledragoncc]

Thats pretty clever H. Can you give more info on the silicon strain sensors or a link pretty please. It sounds interesting. I found this site from UK company and has some great free PDF docs on measuring pressure, torque etc so thought I would post the link here

HBM UK Measuring torque correctly 261 page reference book  http://www.hbm.com/en/menu/tips-tricks/torque-measurement/reference-book/

DD