Wheelchair Motion Simulator

I am trying to build a 2DOF motion simulator for people (my father with advanced ALS) who are in a power wheelchair (~400-600lbs est). I've been reading everything I can get my eyes on about the subject, but I have a few questions.

#1. What is the average range of motion for pitch and roll? It seems like it is between 12 and 18 degrees, maybe 20-24 on the high end ones, but I do want to keep the person in their wheelchair and can't really do a 5 point harness!

#2. How quickly should the platform be able to go from roll min to roll max, pitch min to pitch max? I've seen everything between 2 seconds and .5 seconds.

#3. Ideal center of rotation…wouldn't this be WAY lower than most simulators to emulate the feel of a real car? Most of the 2DOF simulators have the center point of rotation a few inches below the chair. Does this matter? It sure matters for me because it could potentially help me balance the weight of a 450lb wheelchair and it's 150lb person.

If I could get some advice on those that help me a lot!

P.S. This project is to allow the handicap person to drive a remote control car with stereoscopic POV through an oculus rift. It's a big project, but I want to move fast because I don't know how much longer my father with ALS will be able (or willing!) to "try" it. If he can't, won't, doesn't, then I will just allow other people to play with it in his recognition. I know I will have to come up with a dummy chair for able bodied people to try it out. : )

P. P. S. I already have a high end self tightening wheelchair restraint and seatbelt setup that I bought for a handicap school bus motor home conversion, so within some reason we'll be OK with the platform...

I cannot help with what the perfect settings for motion should be but I can tell you that it is possible to build with a heavy weight in mind. I am 6'4" and 350lbs, my rig is around 250 lbs. With winch motors it moves around very well indeed.

Please do continue to share your ideas and build and welcome to the forums.

Thanks for the input guys! My plan is very similar to what you've outlined in the sketch. I had planned on using chain drive of a large wooden disc instead of a large sprocket since it doesn't need to turn more than 30 degrees I can just pin the chain. I like this idea because I could pitch the platform more than normal for loading and offloading of people.

I hadn't considered using a connecting rod like the windshield wiper guys use as you have shown. I will definitely consider one of those for the roll axis.

Currently I'm planning to prototype this with a 25lb NEMA 42 size stepper motor with about 20 foot pounds of holding torque…the biggest one I could get from aliexpress and still get a cheap aliexpress gearbox for it. : ) I've been estimating all of my figures with a load of 10 foot pounds on the motor and my CG 0" off of the "chair platform" floor. I'm hoping that with the full developed torque of the motor and real CG a lot higher than 0" : ) that I will have the acceleration and deceleration that I want. For feedback I'm just planning on "zeroing" the platform using an IMU or AHRS sensor and then checking it during operation for drift. If the motors are sized properly then it shouldn't ever get off.

My current gear ratio of 30:1 (4:1 from a planetary gear head) should be able to swing the 0" COG 600lb wheelchair (pivot point around 30" from the base) from +15 to -15 degrees in one second. This is trying to keep the stepper motor operating at 150 RPM or slower to maximize torque output. Probably MUCH faster than the average chair bound person would want…especially my father with his breathing tube! He makes painful looking facial expressions when going from a sitting to laying position on his hospital bed.

Some of those resources are confusing to me. It seems like someone tried hard to explain it all in simple terms. 200-700mm/s doesn't mean too much to me unless I know where the actuators are attached to the chair. Maybe I'm missing something simple. I would have preferred just knowing the ideal angular velocity.

12v boat winch motors, and set them like @noorbeast suggested in the diagram. if you are using VR headset, you do not need much angular velocity. As he said, just enough to give you the feeling of motion. So 150mm per second would be fine. How to calculate that, I will sugegst @Historiker help here.

I still don't see how mm/s actuator velocity has anything to do with the final angular velocity. 200mm/s near the fulcrum and 700mm/s further away could result in the same angular velocity, and that is all we care about at the end of the day, right? The actuator torque and speed would determine it's ideal connection point. The end effector here is the chair, so why is so much attention paid to the connecting rods to the actuator? Even two arms on a given actuator and two different connection points could result in different linear velocities but the same angular, right?

I'm not trying to argue here, I just want to understand!

I looked at my dad's wheelchair (covertly) and measured the seat location at my kneecap. It was lower than I'd remembered, so I need to adjust some of my rough calculations. I sure have a lot less room to build my contraption than I thought. The gearbox I chose may not be ideal anymore! That's OK since I will need another one anyway having only bought one for testing. Worst case is I have something for the toy box...

One of the things I do for a living is mechatronics. I've done several large 6 axis projects, the biggest one involving an Atlas rocket…so maybe I'm just not in the right frame of mind for the average DIY. ; )

I have a question… I've been looking at tons of videos of motion simulators and games. I've noticed these two of the same game:





The second one has what looks like 5-10x the range of motion of the first. I feel sorry for the rift motion sensor on the first one flapping around on the top of the monitor…it must be angry.

Which is better? The fast jerky movements of the first one or the large movements of the second one? Is the second guy making up for slower actuators by exaggerating the movements?

for race, shorter faster movements
For flight, longer slower movements

So for the racing game the one on top is the best?

If the bottom guy can't make his setup do fast movements, are his larger movements better than short slow movements?

My 25lb stepper motor is supposed to be delivered tomorrow!

larger movements are not actually better, although some will disagree. But generally, for race, shorter sharper movements

I received the 25lb NEMA 42 3 stack stepper motor. Wow, what a motor. : ) The biggest stepper I used previously was a NEMA 23. I use Kollmorgen AKM series industrial servo motors for my day job and mistakenly thought the AKM4x series was NEMA 42. Guess it is closer to 34!

I broke down and bought the parts to build a gaming computer. I have a Z820 with a Xenon 2.xGHz and a Quadro K5000, but it is pretty bad with the oculus rift. I bought a 4GHz i7, DDR4-2666 16GB, 980TI, etc. I've never cared about computer games before and as long as netflix, hulu, or a blu-ray played smoothly I was happy.

The last video game system I had before my dad got ALS was a SuperNintendo, bought used with the money I made selling my NES almost two decades ago. When my dad got sick I started looking around myself looking for things that I could help him use, including this project. ALS is a disease of "lasts", the last time you tie your shoes, eat pizza, walk up stairs, dance, chase a kid, pick up a kid, scratch your nose, wipe yourself, EVERYTHING will eventually go if you choose or are lucky to live long enough. Getting pneumonia and dieting is pretty easy with ALS.

It is very exciting to create something that he never would have imagined doing before ALS, and would never imagine doing now!

I should mention that I did buy a WiiU last year, but we are working out the kinks for him to control a little robot holding a wiimote with his eyes. : )

Another thing we want to use this motion platform for is a quadcopter/boat/rock crawler system we developed using parts of the video game system. Our plan is to mount an accelerometer and stereo cameras/transmitters to the RC "toys" to drive them around FPV style with an oculus rift on the motion platform. This motion platform is the current step in a multiple year thousands of hours project to enable him to do as much as he can.

Hey Eissug, just noticed your location. I went to East High School, lived in Mountain View, and Hillside area.

I've lived in South Anchorage and Hillside. I went to Service. I hope I don't have to move. I really like my one highway with (mostly) two lanes… : ) I went to Chicago and thought I had seen a big city, then I went to Seoul, then Bejing… I think Alaska is my home!

I ran some tests on the NEMA 42 monster stepper motor. I never got a torque curve from the seller, so I can't complain. I get about 150-120W of power within the reasonably usable RPM range of the motor even with running the poor thing on rectified 120vAC! I'm looking for at least a peak of 400w, if not constant output!

I just bought (a cheaper!) 400w servo motor and a 40:1 planetary gearbox to go with it. I will change my chain drive method a little and hopefully that will do it. The motor is supposed to be capable of 1200w peak, but since I will have a 1200w power supply for 2 or 3, I won't be using that range! I'd really like an AC input drive, but they are either expensive from the US or run on 220v. I haven't even built the prototype and I'm already worried about the cost of goods to make the poor thing!

Does having a third axis for traction loss add a lot? Should I try to fit one in somehow?

Forgot to mention that I did do some work with the Arduino and stepper motors. I was pretty surprised to see that there aren't really any decent stepper motor libraries out there! But, maybe I'm just coming from the world of Kollmorgen/Elmo and Galil. Maybe I'm way too spoiled! : ) The 400w servo motor and drive I bought from aliexpress can use a step/direction input like a stepper motor amplifier, so I might drive it that way. If the drive accepts RS-232 commands for motion, I will probably just use that straight into the computer.

Traction loss add's quite a bit Yes, When tuned properly you dont see it much, or should i say When you drive properly you dont feel it much, BUT BUT BUT when you do have a "moment" that feeling of catching it is Utter JOY.....for example my Jordan 191 video @ Monza, Im sure you can imagine the Gut feeling you get when you Counter steer with ALL your Might, and you catch it in time. Its rather exhilarating.

Does anyone have a recommendation for a power supply that's 24v 30+ amps, that's affordable. I found a few but their recommended use is for an LED light strip...Not sure if they'll work for my 720w motor

720w is nominal or stall(peak) ?
Keep in mind that stall value is almost three times the nominal rated .

it's listed as a 3/4hp 720w 24v-29a 56c

if he's recommended them for 200w use, can i assume that he wouldnt recommend them for over 200w use?