A motion platform using Power Steering Racks !!!

[pk_volt]

Hi Everyone

I'm new here.

Anyways, just a bit about myself. I recently graduated from a mechatronics program in a technology institute. Having gained so much knowledge, I figured, why not put it to use. This is when a motion simulator comes in. I've always been fasicanted by simulators, which was the whole reason why I went into a mechatronics program.

Judging from some of the work people have done around here, I guess most of you have already surpassed my knowledge.


Anyways, I just wanted to add a few links to some motion simulators out there just to get some more ideas of possibilities flowing.

unfortunately, this project was discontinued becuase the system wasn't stiff enough, so it always oscillated. Looking further into their provided information, they seemed to have integrated some complicated feedback system

http://www.cadsoftusa.com/people/kls/fltsim/index.htm

here is another 6 dof simulator using Festo's Msucle fluidic system

http://members.shaw.ca/bokinator/X6.jpg

sorry, I don't have the link to their simulator as it seems to be down

[Matt Olieman]

pk_volt, thanks for the info (links) and welcome aboard. I think we're always open to new and old ideas. Thanks for sharing the links.

[CWFlightsim]

Gidday fellow simmers, I have just given my web page a bit of a face lift, some new photos and some more info, the motion system is working great and
I am making panels at the minute so will include photos as I go, the light is at the end of the tunnel now!

http://homepages.paradise.net.nz/cwarner/flightsim.htm

[Roland]

Hi Craig,
Good job on the website, lots of good info available there.

Keith is currently tweaking his portdrv utility, lot's of posibilities! so we're busy testing and tweaking the roll axis drive of the platform drive. Since I use software driven DA converters that drive the roll and pitch servo, there are lots of options to get the best results.

In my experiments I started with the roll angle movement derivative (roll drive based on New - Old value), and when I did tests with the Extra, it was maybe OK, (Red Bull Race effect) but for cessna's and bigger planes, you hardly have the jolt when starting a roll, but your head will give you this funny out of balance rotation feeling during the roll from 0 - 30 degrees. I found that when adding the actual roll signal to the drive, it simulated this feeling, but I needed to do something to get the back to center washout.

As far as I can tell, you and Jim are using the following system: When the readings new - old become > 1 you start to move the platform in (say positive) direction with a certain fixed speed. When new - old become < 1 you enable the back to center drive.

In my case I could make the platform speed dependend on the the value of new - old. To avoid overdrive when the platform drive seems to come close to the extremes, this positive roll drive has to gradually flatten out.
I tend to believe that this roll action does not need to be fast: Maybe the actual roll signal to the servo drive will do.

Then when new - old becomes 0 we start the washout back to center. I think the start of the washout has to have soft-start, so it is not a sudden motion back to center, and the washout movement has to be slow, (how slow?) as the occupant should not notice the washout.

Washout going completely back to zero? --> Actually in a steep turn (like a glider) I found that having the platform still slightly tilted to one side is helping you to get that "being in a turn" feeling (together with pitch up for back pressure)

Do you have any advice on the above? Roll speed, washout speed, start and stop of washout, combination effects, ect.

Thanks!

Roland

[Jim NZ]

Hi Craig,
Just checked out your new, updated website and its brilliant.
The wiring panel has certainely grown since the first biuld !!! but it goes to prove, start simple, get it going, and develope from there.

I had a quick look at the gwbasic code and you certainly got the hang of that pretty quick .. well done !!

I havent yet been able to view the diagrams as I cant see a ppt file with anything I've got... I would guess I'm not the only one with this problem.
Any chance of a doc or a jpg of them ???

Good on the old Kiwi's eh?? (Might have to make Roland an honary Kiwi though ??)

Anyway, great stuff Craig.

Jim NZ
www.jimspage.co.nz

[CWFlightsim]

Gidday, fella's
Hey, Jim, I have changed my PPT to JPG for your perusal.
Also, if Roland can tell us what to do with a piece of number 8 fencing wire, we should make him an honarary Kiwi!
Roland, your return to centre,
you are right, when 1 becomes 0 or when the aircraft hasnt changed roll angle, my roll relay switches off and allows the return to centre relay to take over and allow the motor to move in the opposite direction until the centre microswitch stops it all, in other words the platform will always want to be in the centre unless the PC has other ideas by sending a roll signal. I have my soft start wired up so that the power that makes the sim R.T.C (washout) also changes (via a relay) the pot VR1 on the softstart unit.Therefore with 3x 5K pots and two DPDT relays I can control the activation speed and RTC in either direction (Made for that fat co-pilot) or only me on one side of the sim.I set the speed of washout so it is slow enough that the brain doesnt notice it, the only unfixable problem I have is that there is no 'soft stop' and you can feel when the sim stops moving. I deal with pitch a bit different and have wired in a return to centre inhibitor to stop RTC over a certain pitch angle, I feel that on climb or steep dive you should be 'back in your seat' or 'hanging by your seatbelt', I am still experimenting on the proper angle I am on 13 degrees down and 10 up at the minute anything under that the platform will return.I like the idea of not returning completely to centre but with no feedback I cant really impliment that, I now would like an interface that is more than 8 bit, I am fast running out of channels to use as ideas come to mind. I reackon I have probably halved the sim speed since it was first run, the brain pick up the movement just the same and it is more controllable, I also am not getting airsick any more, that I feel is a good indication that the motion cues are what my eyes expect to see.

Cheers.

[Roland]

Hi Guys,

First thing that comes to mind is fixing that "give" in the roll-pulley key-way: number 8 fencing wire should just do the trick.

Craig, thanks for the explanation and hints on the roll and pitch. It's a pretty clever system you have worked out with the various softstart actions. For the return to center soft-stop, maybe a second set of microswitches on both sides before the center switch, coupled with a resistor to slow the motor somewhat. Or maybe a very big capacitor across the switch? Just thinking out loud. Have a look at my power up softstart relay sequence.

I have the feeling that we all tend to overdo the motion in the beginning of testing, then scaling back to get things more realistic. Can you give me some numbers on the platform roll speed (seconds / degrees) during the change in angle, and the washout? This could give us some clues on what target to program for.

Thanks,

[TronicGr]

Hello to all, I'm building a motion cockpit based on the Joyrider design. Right now I'm in the process attaching the motors (car wiper motors).

Here is an early weight test video:

http://www.ptyxiouxos.net/greekbotic..._ride_mfs1.zip

I'm a beta tester of the Portdrvr (dll) by Keith Daniel and right now I'm testing its modifications to add some washout. This is the software I'm going to use to move my cockpit soon. Roland is with us on this too.

Here some interesting videos I took when tested the code with some small hobby servos:

http://www.ptyxiouxos.net/greekbotic...esna1_test.zip

http://www.ptyxiouxos.net/greekbotic...ftoff_test.zip

Regards, Thanos (Greece)

[Roland]

Hi Thanos,

Welcome to the motion forum! Your videos are showing real progress.
Some explanation for the others:

Thanos and I are the testers for the new version of Portdrvr utility. Thanos has a Basic Stamp unit that drives two servos to prove and test the concept. The data comes in via serial link from the FS PC. As you can see, Keith is aiming at getting two very speedy output data streams, pitch and roll, that also contain all needed cues and washout effects to drive a servo based platform with position feedback. Not an easy task to be sure, but very interesting!

Roland

[CWFlightsim]

Gidday Thanos,
Great videos, I like the servos and programs ability to pick up ground bumps, and acceleration, it looks really reponsive and fast, I would like to see the program again after you and Roland have tweaked and tested it,

Roland I have done a bit of a measure up, the figures are as follows:

my roll axis pivot from centre (each side) is 530 and pitch is about 580, these are based on the gears ability to lift the mass happily without the P/S pump going. I can (and did ) speed it all up by moving the pivots in, but I felt sick, so I guessed this wasnt right, the angles are between 18 and 20 degrees pitch and roll and it takes about three seconds to move from centre to full and about 7 seconds back to centre on washout, the rack movement is about 140 mm. One thing I have observed (IMO)is that the speed of the sim is less important than the movement (say roll) acceleration. In other words if the plane is increasing or decreasing bank the sim should be moving and it would appear that speed really plays a small part in the sensation (to a point)

hope that helps,

Cheers.

CW