Motion Platform Possibilities

[TheFearow]

Hi,

I'm in the design and planning stages of a cockpit, and I'm currently considering an offer I had for motion.
I originally planned for no motion, due to the complexity and difficulty involved, but I've had an offer from a friend of mine who works with motion simulator systems for entertainment uses (e.g. theme park stuff). He's offered to give me copies of designs for a few of the systems he works with, if I'd like to use them. I'm just not sure what system would be best, and what would be the most useful for flight simulation.

All the systems have Roll, Pitch, and Yaw, all nearly unlimited rotation (limited only by the amount of turns before the thing wears through, so tens of thousands of rotations). I know of course the limitations and that things like inversion won't feel like the real thing in most ways, but I'm sure flying upside down would be a new challenge (especially for sim construction, I'm sure most aren't designed to be suspended upside down).

What my main question is at this point is whether more than 3DOF is worth it. I can optionally add a rotationally-adjusted surge (e.g. moving forward/backward in the direction the pit is facing) with between 0.5m and 1m travel and/or a real-orientation heave (up and down, in line with the earth not the sim) with 1m travel. There are limitations, mainly that both those extra movements would be limited depending on pitch, due to design and height limits. At horizontal they have full movement, vertical is 0.1m (or 0.2, I can't recall) movement, and just beside vertical is no movement, with it then becoming full movement again just after that. So for about 80 degrees on each side it's full movement (if that makes any sense).

I'm both not sure whether these would add anything, and especially for the heave, whether it's remotely feasible to interface them. It also adds complexity to the design, and construction. With the surge axis I then require extra high-strength actuators, which would add more cost. The heave axis is not much more cost, and makes entry/exit easier, although it may not end up being used for anything except lowering the sim for entry/exit. I'm not sure whether it'd be feasible to interface a real-world oriented axis with the sim, if that's the only translational axis I'm implementing.

The benefits of this system are no hydraulics, entirely powered by electric motors, and a lot of freedom of movement. It also requires a small area (5.5m x 5.5m, and my sim design is 4.5m long). It's biggest downside compared to a stewart platform or such is that it requires (precisely) 6.25m vertically. Which isn't too hard, I plan on spreading it across two stories (standard floor height is 2.5m including dividers here, so just sink it down slightly).

For now, my skills aren't really an issue, I'm a computer network engineer with a lot of background experience in electrical engineering (mostly microprocessor-based systems) and some mechanical engineering, so the building side shouldn't be that bad. And I've got help

Anyway, sorry for the long post, I thought I'd try and cover all of what I wanted to say. Any advice/stories/ridicule is welcome!

Thanks,
Matt

[kermit]

I think besides contruction limitions of your house/building also eletricwise,
You have to know what kind of cockpit are you building, what are the parameters of the plane,
a f 15 figther will have very different parameters then lets say a 737 or Cessna ,
I can`t find pictures of 737 do a 360 degree roll with holidaymakers on board
If you building a 737 or other airliners a 3 dof is all your need but if you have 6 dof within reach why not.
Also if your are planning on 360 degree rolls or high speed pitch/bank, you have to calculate the strengh of the material used.
Things can get very wrong when parts starts snapping off during a high speed S-turn.
Also you have to know your budget and planning, will you make motionparts yourself or are you planning on buying shelfstuff.
Before you start planning , its advisable to search the internet and get things clear in your head before starting this major event.
But when you start have a nice time and think of the end result
greetz
please make pictures during building , so we can follow you progres

[TheFearow]

I think besides contruction limitions of your house/building also eletricwise,
You have to know what kind of cockpit are you building, what are the parameters of the plane,
a f 15 figther will have very different parameters then lets say a 737 or Cessna ,
I can`t find pictures of 737 do a 360 degree roll with holidaymakers on board

I've seen one do it without passengers, but would make an interesting holiday if you were on board . The cockpit is a semi-custom long-range trijet, low capacity (business-jet kind of seating).

If you building a 737 or other airliners a 3 dof is all your need but if you have 6 dof within reach why not.
Also if your are planning on 360 degree rolls or high speed pitch/bank, you have to calculate the strengh of the material used.
Things can get very wrong when parts starts snapping off during a high speed S-turn.

I can imagine, and that would especially be a problem inverted (don't want my pedestal falling onto my overhead). The motion system provides a metal framed box, that's about the right size for the cockpit, so most of it was going to be built off that and I was going to use either metal or some strong wood for the internal cockpit structure.
Also a note, it would be an approximate either 4DOF or partial 5DOF system, since the heave isn't quite "normal" heave.

Also you have to know your budget and planning, will you make motionparts yourself or are you planning on buying shelfstuff.
Before you start planning , its advisable to search the internet and get things clear in your head before starting this major event.

I've done a reasonable amount of searching, and I'll certainly be doing more before construction, as the area which I plan to build it in isn't ready for a couple months. Most will be made myself, which is partially why I like this design as easy to build (relatively).

But when you start have a nice time and think of the end result
greetz
please make pictures during building , so we can follow you progres

I'll be certain to set up a blog and such with progress once I get going, probably even before then with plans and models. And I'll make sure to take lots of photos.

-Matt

[kermit]

Hi,
I wouldn`t advise you , not to use wood , if you are intending to do 360 degree rolls,
as it is a natural component and the platform structure endures a lot of forces in all directions,
you are better off using aluminium ( you could use wood for light lining offcourse).
If you have extra dof features you could rebuild a line to get heave action,
do you have a picture of the platform you are going to use?
greetz

[TheFearow]

I was mainly thinking of using wood for some internal stuff, e.g. instrument frames (MIP etc). Do you think even for that aluminium is a better choice?

I've thrown together a quick diagram of approximately how it works, although the details of the mechanics are left out, it's just an overview. I've attempted to label it for a better explanation.

Just as a note, I was looking at the wrong height in my original post, the actual specs for size would be:

• Total Height: 6.5m
• Maximum Width (either direction): 4.5m

Note that this doesn't account for the method of getting in/out, which would be separate (I'm guessing a fold-down set of basic steps would be best).

-Matt

[kermit]

Hi Matt, Nice picture
what are you going to use as main current?
I don`t want to put you down, but looking at your answer regarding internal structures and the use of wood,
I`m really wonder if you know anything about quality characteristics of materials
and how to calculate forces and other mechanical characteristics .
I wouldn`t be in your cockpit when a heavy Mip shears off and starts coming down on you while sitting up side down.
Do you know the maximum weight the platform can lift and the speeds,
and I would advise you to use aluminium(popped and glued if you can`t weld alluminium) instead of wood but steel would be better.
But only if you really want to go upside down, if you are going for a 3 dof you can use wood provided you use quality. just my 2 cents

Do you already have all the components for the flightsim itself like seats, mip, screens ,overhead and so one?
The design itself looks great, you can add heave iff you rebuild the colums .
In that case you have to use limit switches or program your software ,
as it will cut off banking at a certain height or you will slam into the concrete.
What will you be using for controlls like PLC /programmes
all in all I`m very interested in the end result
greetz

[TheFearow]

Hi,

Not sure what you mean by "Main Current" there.

Regarding materials, maybe I'm being unclear. I don't mean I'm using wood for anything strongly weight-(or load-)bearing, just surface and instrument frames etc. The main body, and the joints to attach everything to the body, would be metal (aluminium or steel, not sure which). Certainly wouldn't want a MIP falling on me, so I'd make sure everything was held in place well.

The weight the platform can lift I'm not sure exactly, from the original specs I'm basing off it's pretty reasonable, as they are made to lift simulator rooms with 6-8 people in them, including seats, railings, projectors, and effects systems. From what I've seen of them they'd be about the weight of a simulator. Speeds are an issue, and would depend on the motors and gearings I use. I'd probably experiment on what worked best, and I've seen sims based on the design I'm basing mine off go pretty fast. They'd be able to handle most aircraft activities fine.

The column plans I have come in two designs, one with heave (where the pitch pivots are mounted on track that moves up/down), and one without. I'm not sure whether the added complexity is worth it though. Software limits wouldn't be that bad, and I'd include some hardware ones as well. Certainly wouldn't want to be flung into concrete (or through the roof).

As for cockpit parts, not yet, as I don't have too much space right now. This setup is going to be in a dedicated space in a new building, along with my new workshop areas etc. So I don't have much constructed yet (although I have a lot of plans lying around).

For controls, I'd plan to run the whole thing off a modified PC, running a real time OS most likely. The motors themselves would be controlled through an I/O bus carried through the slip rings, with custom microcontrollers and motor controllers at each axis. I've got plenty of experience with those sorts of setups, and should be the best option. Not sure about running digital I/O through slip rings, does anyone know if I'd have a problem with interference/losses/wear/etc? Rotary transformers as used in VCRs etc might be another option, although I've never really used them before.

Thanks for the help/advice/discussion kermit, it's helping me very much

Thanks,
Matt

[kermit]

Hi,
I sorry some times I translate one on one with dutch sayings,
I mean Electric power
Maybe we can use both expertise, I`m working in the winches and capstansfield, and have a mechanical degree.
I`m know how to build things and know some things about pulling heave and stuff, and I can get every motor and gearbox I need
On the other hand I`m a complete noob about software and implenting software/plc to drive motion platforms.
still looking for motorcontrollers and plc to drive my motion platform 2 dof,
I want to use 220v 1.5 kw 1500 rpm 1 ph motor with a gearbox I=35,6 ratio ,
it will drive my platform easily at a rate of 36m/min both directions(as its only weighing about 300 kilo or 700lbs in total.
But can`t find a suitable plc and motorcontrollers for the setup
greetz

[TheFearow]

Hi,

For electric power, I'm not quite sure. DC is easier and cheaper to get through the slip rings and to control (I have experience with DC motor controllers) and I have a cheap source of DC motors, although AC motors seem more common. Not really my area of expertise. My house is already wired up for DC supply (very little AC buses), so that's a better option from an efficiency perspective. I have about 200A of 12VDC planned to be available in the new simulator room, and I may run a bar from the 24VDC bus into that rooom as well, which would give about 100A max. I have no idea if this is enough, but it should be if used properly. I'll also probably have 20A of 230VAC as well, although I could extend that and remove most of the DC buses.

It'd be great to share experience, software and networking are my main fields and I'm sadly lacking in the engineering and construction areas, although I do have some experience.
First of all I'm assuming by the fact you say 1 phase and 220v that you mean AC, not DC.
Assuming by motor controller you want a variable-speed controller, you're probably better off with a three-phase motor if you can, as far as I know. Almost all the controllers I have seen are for three-phase, and I remember reading somewhere that it's a lot harder to electrically control the speed of a single-phase motor. If you're not looking for variable speed, or would accomplish that non-electrically, then contactors would do.
For the software side, I'd recommend that you either go for a more powerful microcontroller (e.g. one of the higher-end PICs) or some sort of high-speed control from a PC. You want to reduce latency (lag) on the motion as much as possible. Do you plan to calculate all motion values etc in the sim software then send them to the microcontroller, or simply send the desired angles and have the microcontroller work out the values? (by values I mean actual sim orientation, taking into account the various tricks to fool your brain).

If you're looking for specs and/or good quality automation components (e.g. motor controllers, motors themselves, control circuits) I can recommend RS Components as a good place to start looking, although they are quite expensive.

Just out of curiosity, what is the standard AC frequency where you are? It would affect what controllers you can use.

Hope any of that helps, I tend to ramble on and get distracted sometimes, and it's late. If I've misunderstood what you mean, blame the time I wrote this .

-Matt

[Roland]

Just my experience: Heave is a great addition to pitch and roll. It is more difficult to implement, but definitely worth it, both for GA and Airliner flying. For airpocket "stomach" feeling, you'll need at least 0.3m travel, and it needs to be fast (0.6m/sec actuator speed). for the small turbulence, (smooth) touch-down and ground bumps, small 5 ~ 10cm excursions are sufficient, but still need to be fast.

Measured total electrical power levels for fast heave step with 160kg payload: ~ 1.6kW peaks. Average power (in balanced system): ~ 120W. Power delivered by 3x12V batteries, driving PM DC motors in a 3-point setup.