Page 1 of 2

4 wheel steer with 9x

Posted: Wed Jan 16, 2013 1:50 pm
by MadScientist
Hey guys, I posted in another forum but I think I posted in the wrong section. I need some help with getting my 9x setup to handle a 4 wheel steer setup for my senior engineering technician project. Ive attached a picture of the control mapping that I need. The original thread is viewtopic.php?f=27&t=2558

if at all possible, Id like to change some of the menu "titles" inside the firmware, to more replicate the car steering environment, but the main thing i need help with is the mixing. I saw some You tube videos where the guys used curves and other things, so I think the below map is possible but im not sure.

also, is there any where i can program on the PC using a graphical interface then upload to the trasmitter?

thanks for any help you can provide.

Re: 4 wheel steer with 9x

Posted: Wed Jan 16, 2013 7:15 pm
by gohsthb
What custom firmware did you upgrade to? If it was Er9x then use eepe. If it was open9x then use companion9x. Both of these programs allow you to program a model on the computer and write it into the radio.

You can go in and change the labels in the source code, it is open.
open9x available here
er9x available here

Here is my implementation of your diagram. The only change I made was to put the speed sensitive rear steering on the RUD switch. My file will only work in eepe.


Re: 4 wheel steer with 9x

Posted: Wed Jan 16, 2013 10:26 pm
by MadScientist
thanks alot. im downloading all that stuff now. i spent the last couple hours reading up and watching youtube. im rying to learn this stuff as quickly as possible.

Re: 4 wheel steer with 9x

Posted: Wed Jan 16, 2013 10:38 pm
by MadScientist
useless info...deleted

Re: 4 wheel steer with 9x

Posted: Thu Jan 17, 2013 3:38 am
by MadScientist
useless info...deleted

Re: 4 wheel steer with 9x

Posted: Thu Jan 17, 2013 9:34 am
by MadScientist
whew... man long night.. i think ive got this software down now.. at least enough where i feel comfortable making some changes.. check the movements out now. the steering stick is more based on a bias now. and when the rud switch is on, its in "racemode" the steering input is directly linked to the throttle. the faster it goes, the less it will let the wheels turn together.

I still need to add 1 more mix in though to fix something. when in "race mode" i used a curve to limit it to60% max movement with no throttle..curving to 20% max servo movement for both sets of wheels at full throttle . (which will actually produce a nice smooth track around a race track) but now i have a problem. The problem came from the mixing i used to bias the front/rear steer percentage when in manual mode (or rud switch "off". if I move the bias stick to full front steer while in "race mode", then i end up with only that same 20% front steer, but no rear steer.. and like wise if i bias full rear steer, i only have 20% rear and no front (again this is at full throttle) this simply wont work. I need to figure out how to ignore the bias when im in "racemode" so that my steering to throttle mapping will still work correctly..any ideas on how to do that?

here is new version.. i think im done for the night.

ps. i cant WAIT till i get some money saved up. This has definately got me wanting to mess with some airplanes. the possibilities!!!!

Re: 4 wheel steer with 9x

Posted: Thu Jan 17, 2013 10:10 pm
by MadScientist
useless info....deleted

Re: 4 wheel steer with 9x

Posted: Fri Jan 18, 2013 12:55 am
by Rob Thomson
Have you considered trying open9x?

The flight mode options may help you a achieve what you want between the different modes.

The modes can me triggered by custom switches... Making them very flexible.

Sent from my Nexus 7 using Tapatalk 2

Re: 4 wheel steer with 9x

Posted: Fri Jan 18, 2013 1:27 am
by MadScientist
no i didnt consider that.. and to be honest as much time as i have in this one, i dont think i want to change lol. I think what i want to do is possible. i just need to figure out how to do it. everything is done except one simple problem.

Re: 4 wheel steer with 9x

Posted: Fri Jan 18, 2013 2:17 am
by MadScientist
useless info....deleted

Re: 4 wheel steer with 9x

Posted: Fri Jan 18, 2013 2:55 am
by MadScientist
oh MAN!!! haha. i didnt realize that the posistion of the mix in the list would affect how it was applied. i just moved the switches for the lane jump down the the bottom of each list, and now lane jump is functioning correctly regarless of controller mode or bias posistion.

NOW the bias is still affecting the race mode (even after being moved to the proper place in the list) so thats the last thing i need to figure out and Im DONE.

Re: 4 wheel steer with 9x

Posted: Fri Jan 18, 2013 4:19 am
by MadScientist
FIXEDDD!! MIXING DONE :D :D :D that was fun!! I still think i may need to go back and change some of my values for example i may need to change !RUD to RUD, or !AIL to AIL, but without the controller, I am not sure if its correct. Its easy to change though later if i need to.

Now.. time to make the alarms work. I need this thing start beeping like crazy if someone picks up the controller and starts flipping switches. guess ill need to get to that section in the manual.

Basically what I have done, is set the controller up so that if all the switches are off, you are in ATR and throttle limited mode.and of course all the switches have to be set the way i want for the beeping to stop when you cut the TX on :) that way someone cant just pick the controller up and start flying away with it and roll it over 15 times and break something. 4 wheel steer is notorious for flipping.. even with all the suspension work I'm doing to it.

Ive also went back in and added some throttle limitations. Remember this thing is going to be getting played with by a bunch of kids around a booth.. "I" know how to turn it wide open, but they wont. to be honest, any time 4wheel steering is enabled, you would be better off with throttle limitations anyways.

That said, I'm not sure if i like the way i have the ATR and throttle limits set up now. But to change it to the way i WANT, then i would need telemetry so it could be based off of speed and not throttle % as it is now. (maybe gps???) Now, you could just go 35 mph, let off the throttle and turn it quickly and you will still have enough speed to cause it to flip, and no limit on the steering angle since you let off the throttle. Additionally, i think it might still be a little hard to drive. if you command it full left and its not tight enough, your going to have to remember to slow down to tighten up the turn.. where-as if throttle was mixed off of steering angle, (backward of how it is now) then the more you turn, the more it will automatically slow down. you could just hold it wide open and turn, and let the controller do the work, after thinking about it..i think i should change it... but anyways...Ive had enough of this for a day or so. haha.

also remember below, when you see the term ATR active (automatic turning radius) that means !RUD is selected on the !RUD/RUD switch. and likewise ATR disabled means RUD is selected.


Start-up mode (also know as ATR mode - automatic turning radius)- no switches in "on" position: 4 wheel steer angle locked at 1:1 bias, and limited to max 80% servo travel at 0 throttle. 10% at full throttle. Max throttle limited to 84% This is "idiot proof" mode

ID0 - wheels turn in opposite directions
ID1 - wheels turn in same direction. (ID1 is affected by ATR when ATR is on. Contrary, Steering bias does not function when switched to ID1, regardless of mode or AIL switch positions. )
ID2 - overrides and turns off all ATR, throttle restrictions, lane jump, and biasing. Completely locks out rear steer. This mode replicates factory out of box settings with no rear steering and 100% throttle allowed.
** Unless otherwise stated, ID0 and ID1 functions perform identically with the exception of different direction steering angles; functions that don't apply to ID1 are noted **


!RUD- ATR mode active
RUD - Shuts down ATR mode, and gives full range of travel to both sets of wheels.

!AIL - Steering bias Enforced. (unless ATR is active which overrides bias settings) Elevator control position determines how much front or rear bias is applied to the commanded position. Example: elevator 0 = full front and rear steer 1:1 ratio; Elevator 100 = full front steer 1:0 ratio; Elevator -100 = full rear steer 0:! ratio.
The % of input is progressive through the elevator stick travel 2 exceptions:
1) the middle 50% of the elevator range gives 1:1 bias. (this allows a little play in the stick that will naturally occur)
2) the top and bottom 25% of the elevator stick travel are reserved for 1:0, and 0:1 ratios, respectively. (again, this ensures the user has a little "play" in the stick movement and rids unwanted inputs"
AIL - Bias not active

Examples (switch settings)

RUD OFF/ AIL OFF - ATR on, biasing overidden
RUD OFF/ AIL ON - ATR on, Bias overidden+disengaged
RUD ON / AIL OFF - ATR OFF, Bias Functioning
RUD ON / AIL ON - ATR OFF, Bias Disengaged

RUD OFF/ AIL OFF - ATR on, biasing not applied
RUD OFF/ AIL ON - ATR on, biasing not applied
RUD ON / AIL OFF - ATR OFF, biasing not applied
RUD ON / AIL ON - ATR OFF, biasing not applied

Throttle limits explained

Throttle limits are set up in a manner that will allow best operation of vehicle by inexperienced users. In conjunction with ATR, the car will be safe, reliable, and very easy to handle. Variations of switching modes will allow you to achieve different throttle levels if desired.

First - !THR is default selection at start up. moving this switch to THR will allow 100% throttle regardless of mode (with the exception of mode ID2 which has its own 100% limit in place) !THR/THR switch can be considered the master speed switch.... !THR = limits are on; THR = limits are off.

!THR - throttle limited to 76% **overridden to 84% when ATR (!RUD) is active; overridden to 100% when in ID2 mode**
THR - Max Throttle Allowed (regardless of ATR setting)

We will assume that we are still in Startup mode. Normal start-up mode requires !RUD, and !THR to be selected. This ensures ATR and throttle limits will be engaged. Anytime ATR is active the throttle will be limited to 84%. **UNLESS THR is selected; which allows 100%. Assuming !THR is selected: This ATR active 84% throttle limit will override the !THR throttle limit of 76%. The ATR throttle limit does override !THR 76% limit, but does not override the THR 100% master limit.**

At this point the TX is in Startup / ATR mode with an 84% throttle limit and steering that reduces as speed increases. By switching off ATR, you will gain the ability to steer the car 100% lock to lock. Due to the instability this will cause, the Throttle will now be limited to 76%. (again we are still in !THR mode) If the user feels they would like the 100% throttle, they can simply switch to THR.

**the AIL setting ( bias settings) does not affect the throttle limits in any way. This, however, may be changed in a later version.**

Examples (switch settings)

!RUD / !THR --- ATR active - throttle limited to 84%
RUD / !THR --- ATR Disabled- throttle Limited to 76%
!RUD / THR --- ATR active - throttle limit = 100%
RUD / THR --- ATR Disabled - Throttle limit 100%
ID2 ---- Throttle limit 100% regardless of any other settings.

**Each switch and the function built into it is completely independent of the other switches with a few exceptions.***
1) When ATR is activated, steering bias is not functional regardless of AIL switch position, or Elevator Control stick Position. Car will steer with all 4 wheels at 1:1 bias whenever ATR is engaged.
2) when in ID2 mode All ATR, Lane Jump, Throttle limts, and rear steering are cut off or overridden
3) any time ATR is on, the throttle will be limited to 84% unless THR is switched on. THR is the override to Force 100% throttle regardless of mode.

and here is the latest version... btw.. i dont expect you guys to read all this.. this is more so that anyone who comes behind me to work on this car will have a record of how things work.. lol.

Re: 4 wheel steer with 9x

Posted: Fri Jan 18, 2013 6:13 am
by jbeebo
Good job dude! Good luck on your school project!

Re: 4 wheel steer with 9x

Posted: Fri Jan 18, 2013 6:34 am
by MadScientist
thanks! i cant wait to get it done. we have alot of work to do, this is just the beggining, but i figured id get it out the way now before we have to really start making parts and worrying about deadlines. This little bit of mixing i did has really got me interested in the power of these radios and what can be done with them. Im hooked! Im sure ill be posting more and ill get some pictures posted to as we get stuff done.

Re: 4 wheel steer with 9x

Posted: Fri Jan 18, 2013 12:09 pm
by jhsa
please let us know how it came out, with pics and videos.. that is a cool project..

Re: 4 wheel steer with 9x

Posted: Sat Jan 19, 2013 8:50 am
by MadScientist
Def will. Talked with a carbon fiber company earlier, and he said he is going to donate all our parts we need made out of carbon fiber as well! its getting better and better! cant wait to get some real design work done on this thing and start going with it.

Re: 4 wheel steer with 9x

Posted: Sat Jan 19, 2013 6:23 pm
by MadScientist
found my answer....on to the next task..

again im back to implementing more safety functions and "idiot proofing" the controller.

so far

added a reverse speed limiter
determined i HAVE to get voice module (fun!)
found out that im getting a 9xr and not a 9x (thats a good thing)
am trying to figure out a simple way to set the limits of the steering angles using P1/P2 and a bump on the stick. working on this one. i dont know if its possible, but trying.

Re: 4 wheel steer with 9x

Posted: Sat Jan 19, 2013 10:31 pm
by MadScientist
going into detail on that last item... i have one switch left... the ELE switch. I want to use this as the switch that turns on a limit set function. So when !ELE is selected, preprogrammed limits are used.

ill go through it below step by step and put in quotations, what i invision the voice module will say. This i think will give the best representation of what i want to happen.
Remote turned on first first startup.
Front wheels reach full travel at 50% aileron stick travel. Need to adjust limits

!ELE switched to ELE voice prompt "Limit Setting Mode Activated."
P1 controls front wheels. Starting from middle position, turn pot counter clockwise until full steering angle is reached. (left direction)

Hold TRN switch and Command AIL stick full left to "lock in" the limit...voice prompt "limit set"
release TRN switch
repeat for right direction, commanding stick full right for right limit. voice prompt "limit set"

Repeat for rear wheels, but using P2.

switch ELE to !ELE voice prompt. "Limits Programmed"

soo.. is it possible?? ive seen variable rates with pots, but never seen limits set with the controls. so far i think you have to have a 3 input setup like this because if you dont, how will the controller know to differentiate a left limit from a right? or perhaps you could use logic switching and just command the ail stick full left to lock in the left limit (with no TRN switch requirement) i also have to assume this wont affect any of my other mixing, since that is all % based anyways.

Re: 4 wheel steer with 9x

Posted: Sun Jan 20, 2013 3:48 am
by jhsa
MadScientist wrote: determined i HAVE to get voice module (fun!)
found out that im getting a 9xr and not a 9x (thats a good thing)
No it's not. 8-)
The 9XR doesn't have much space inside for the sound module or anything else.. :roll:

Re: 4 wheel steer with 9x

Posted: Sun Jan 20, 2013 10:59 pm
by MadScientist
its a good thing because i dont have to spend more money for boards, backlights etc.. im sure there is somewhere to fit a module in that thing!

Re: 4 wheel steer with 9x

Posted: Mon Jan 21, 2013 12:21 am
by jhsa
ok.. :)

Re: 4 wheel steer with 9x

Posted: Mon Jan 21, 2013 6:27 pm
by MadScientist
where there is a will, ther is a way.. hell this time last week i didnt know ape c**p about er9x or anything else about a transmitter. and now i feel perfectly confident programming one. where there is a will there is a way

Re: 4 wheel steer with 9x

Posted: Mon Jan 21, 2013 6:41 pm
by jhsa
I really hope you can do it.. we are all very interested.. ;)
I do wish you all the luck with your project, can't wait to see the results. It's a good test to the custom firmwares :P

Re: 4 wheel steer with 9x

Posted: Mon Jan 21, 2013 8:50 pm
by MadScientist
well im basically done programming the controller.. i would really love to have the firmware mod i discussed in the firmware part of the forum but if that doesnt happen.. no biggy.

but aside from that.. now im just waiting for my controller to come in the mail. after that the carbon part gets built. i already have all the new shocks, turnbuckles, aluminum steering blocks etc.. i only need to design and build 1 more part and its basically going to bolt together and run..

i do have one issue i just noticed, and that is that the front of the car is more narrow than the rear of the car. Im not sure if thats because the last group that tried this (and failed miserably lol) maybe changed something, or if thats how it came out of the box. so Im either gonna have to do some mixing to make the front track the same as the rear, OR im gonna have to widen the front. we'll see. but we should start seeing some good progress in the next couple weeks.

Stay tuned.. pictures will start popping up once i have something to show you guys!

Re: 4 wheel steer with 9x

Posted: Mon Jan 21, 2013 9:01 pm
by jhsa
Great, thanks ;)

Re: 4 wheel steer with 9x

Posted: Thu Jan 24, 2013 11:13 pm
by MadScientist
got the main supporting brackets designed in solidworks, and printed on the 3d printer today. completely forget to get pictures but i will monday. its actually not quite right, so doing a redo, then if its correct, making the mold and shipping out to be carbon fibered... still havent got my controller and tx/rx modules yet.. hurry up and wait...damn hobby king.

Re: 4 wheel steer with 9x

Posted: Sun Apr 14, 2013 1:27 am
by MadScientist
well guys its been a long time since i gave you an update but it has been extremely busy around here.

i FINALLY got my 9xr in the mail. Ill be hooking it up to the servos hopefully next week (wednesday) and making sure everything works like i want.

The carbon fiber bracket will be done next week also. we had to wait to the last minute on it, to make sure everthing mounts up correctly. THEN after we were happy, the USPS lost our molds, so we had to spend another 2 days making new ones, and then wait 2 days after that to get more CNC machine time. But thats all done now and the Carbon bracket should be here soon

The only thing we have left on the car is the shocks. we have everythign else done and designed EXCEPT location of the shock. we made new control arms as well. The problem is that there really just is no room for shocks. the steering parts all get in the way! and if they dont, the upper control arm, or drive shafts do. But, i digress, im sure we can figure something out.

We also redesigned the rear control arm setup, so that we could use all TRAXXAS parts for the steering. (except control arms) simple fact of the matter was that it was just simpler for us to do this and the parts fit.

Pics in the next week or so! I promise! cant give to much of the design process away! :D

Re: 4 wheel steer with 9x

Posted: Fri Apr 19, 2013 10:46 am
by MadScientist
some pics of the progress.. none of these are the final parts, but give you an idea how we are doing it.

Re: 4 wheel steer with 9x

Posted: Sun Jun 02, 2013 1:21 am
by Stano71
Hi, looks like a tough machine, just wondering if you have any updates and if you would be willing to share your setup file for the 9x (er9x), cheers, regards Brendon

Re: 4 wheel steer with 9x

Posted: Thu Mar 06, 2014 7:27 pm
by Measuredpath
I can't wait to try this on my buddies CR-01 he just picked up as I offered to let him use my spare 9X that normally gets heli service :lol: