Motion Platform Possibilities

[TheFearow]

Ahh, I can imagine Heave would be great especially for those. If I follow the heave addon for the original design, it simply moves the pitch pivots and mechanism up and down on a chain lift, which can go reasonably fast, although I'm not sure on exact specs. It has about 1m travel (each way, so total of 2m distance) at 0 pitch, and about 0.15-0.2m travel at 90 pitch. Somewhere around 80 pitch there's a zone with no ability for it, but that should be fine.
Would you recommend sticking with that system, or going an actuator-driven approach? I'd rather stick with what I'm familar with, although I can imagine speed etc might be a problem.

The amount of power may be a bit annoying, that's a lot of amperage going to one motor. I would probably want a bigger supply then, for Heave at least. The other axis aren't really doing much lifting (ideally), so they should be fine (except maybe Pitch, if I don't balance that well). Out of curiosity, how long were the peaks in your experience? For the duration of sharp movements or mainly rush current at the start of movements? I'm thinking of putting some large supercaps on the motors to cushion some of those spikes from hitting my supply, although that won't be helpful if they keep pulling for a while.

[Roland]

A chain lift construction can be build strong, and makes it easy to add a weight balance system. (lots of bungee)
But the pivots need to be super strong, and need to run in some kind of rail system to avoid wiggling. Building a structure with sufficient stiffness can be quite tricky.

But keep in mind that heave acceleration needs to be fast to be able to feel anything. With higher payload, the forces will increase according F=m*a. same for power.
For DC motors, using higher voltage motors (i.e. 50V in stead of 12V types) will help reducing current and reduce conduction losses considerably.
Note that all high power DC motor control are based on switch-mode PWM . They rely on motor inductance, so adding supercaps across the motor will result in smoke.

Acceleration duration is normally short, around 0.2sec. Of course longer travel makes longer acceleration possible.
Some scope plots on current during heave step :http://www.simprojects.nl/platform_d...ations_iii.htm

[TheFearow]

The original I'm basing this off had the pivots mounted on four metal bars running vertically as rails, which were very sturdy, and the lift itself had brakes and locks for when there was no heave needed. I can imagine the stiffness would be hard, especially since the columns themselves are turning on the yaw. It may help that the system is well secured at both the top and bottom, although I'd still need solid supports.

As for motors, I'll look into options for higher voltage - my main reason for wanting 12V is that my house is primarily 12VDC supply, although there are 24VDC buses. For payload, would counterbalancing the heave system (similar to how it's done with elevators) be helpful? It might be possible, and I can imagine it would help reduce some load, although the benefit might make it not worth it.

I meant supercaps on the motor supply, so for motor controllers on the voltage input of the controller, not the motor itself. Although now you mention it, the other way might work well as a cheap fog machine replacement, no fluid needed .

Good to know about normal duration, and with longer travel (I'm looking at 1m at straight and level) basic turbulence and dips and things could probably be reconstructed truly, which would be nice.
That's great to read, and a lot of interesting information. I've had a bit of a read around, and a very nice site .

Thanks for all the help/suggestions/feedback!

-Matt

[Roland]

For payload, would counterbalancing the heave system (similar to how it's done with elevators) be helpful? It might be possible, and I can imagine it would help reduce some load, although the benefit might make it not worth it.

Counter balancing with counter weight like in elevators will double the mass that needs to be moved. Using bungee is light weight, and won't add extra mass.
Using air-pistons and expansion vessel is another low mass solution, and more flexible for tuning the force. Succesfully applied by HI6sim http://www.xs4all.nl/%7Ejippes/hi6sim/index.html

[hca]

Hi Matt,

Based on a scan of the topic I suspect you are heading toward building a sim similar to what I have been working on nearly every day for the last 4 months.

If so, i can relate a bit as to where you are headed, not to frighten you off, but to assist you if you are deviating from the normal plus minus 30 degree type motion platform. I will describe what i have been doing and mention the additional s that crop up.

Briefly my sim 2 stated out as a rotating motion assembly into which i would transplant plant my single seat generic sim 1 now in the lounge room which is built with a steel frame with a view to motion

My sim 2 consists of a rotating platform 3 meters in diameter, on top of which sits a gimbal frame 1.7 metre above the rotating table (as in gyro), in this gimbal frame (just under 3*2 mtrs), sits the cockpit it self. The original scope was for a full Boeing size cockpit but for now to take the sim1 single pilot cockpit.

So we have unlimited pitch, roll and yaw for 360 degrees. Yaw in the rotating base, roll in the gimbal on the base then pitch with the cockpit inside the gimbal. Power flows and data through sliprings on the 3 bearing axis's.
I considered heave and surge but the shed is just not big enough and nor is the mains supply.

For a start without the cockpit and the access stairway and retracting walkway, there is 400 kg of 50mm*100mm steel box, and quite a few 6 mtr lengths of assorted size steel bar. 10 1 inch flange bearings, 5 1 inch custom machined shafts, 5 custom machined 1 inch boss/flanges plus the sliprings and 8 steel roller wheels.

I calced out wheelchair motors would move every thing fast enough via a suitable reduction drive from 24volts. only problem was switch mode supplies i could find were not really up to providing the required peak 40 plus amps. Add 2 truck batteries to the weight on the rotating platform. I figured one motor on each axis to be enough as long as the sim was balanced but worked on using 2. So far one motor rotates the gimbal and platform 360 degrees in just under 2 seconds(no cockpit installed as yet). Here in Bali there is no source of suitable reduction drives, but motor bikes are dirt cheap. it turns out they run 15 to about 40 teeth to drive the back wheel, fabricate a boss for the motor and weld on a 15, then an idler with a 15 and a 42 tooth, then another custom made 1inch boss with 42 tooth and 2 chains. and its more than mobile enough for a flightsim, probably even a fighter but thats not the aircraft dynamics I plan to simulate. Dont forget you might want to stop and reverse this moving mass quickly.

Ok the cost of those machined parts here in Bali probably ran to 300 plus USD , but we are adding kilos all the time, and these are moving kilos that the motors must be able to control safely while the weight is moving fast and has a lot of leverage. ( ie upto 2 meters from the rotation axis). Consider flex and torsion in you plans, also metal fatigue and stress points. I think you will ditch wood and ally if you are building some thing similar to me.

Based on the results achieved with 1 wheelchair motor for the rotating platform and 1 for roll on the gimbal which are both mounted on the platform, I figured i would go with 1 on the gimabal frame for the cockpit roll. Thus 2 meters of 50mm*100mm steel box filled with scrap steel and concrete (28KG)is added diagonally opposite the pitch motor to restore the balance on the gimbal frame in lei of the second motor and drive.

Balance is important and difficult to perfect in a spheroidal machine with out huge motors, buy an electronic scale!

If you don't have a hoist in the roof, i recommend you plan on building some kind of removable lifting system in the towers that hold the gimbal to lift it and later the cockpit into the gimbal. 6mm steel rope, steel gate rollers and a 1 ton chain hoist worked for me.

Next consider how the sim will be kept stable on both axis when getting in and out. add more electric actators and steel locking pins complete with the mechanisms to move them and the (dueled for safety) sensors to control them.

Also how to get into and out of if? I ended up with a 2 metre high staircase and retracting walkway, add the other half of the double garage and another electric actuator plus 30 metres of 1 inch steel box and a few more sheets of 15mm plywood . Hand rails? add another 30 metres of steel rod and a bit more box.

All of this stuff needs to be made strong and safe, over engineer the steel work and lots of interlocks, you plan to ride in this thing, and probably take your kids, it need to be safe. This kind of machinery can take your fingers off, break your arms, or crush your body, or dice your kids while you fly. Big weights, powerful motors and lots of mass moving fast. Its a no go zone in the immediate vicinity

Obviously this kind of kit is not entrusted to Microsoft. every thing here is controlled by microchip pics and linux.

Also a balance adjust system is required unless you use huge motors, add another 100kg of steel and concrete a dozen more steel roller wheels and a few more actuators.

For linear actuators I have used a lot of 18 inch satellite dish positioning actuators, i anticipate a total of 10 complemented with 7 12v wiper motors and a handfull of electric car door lock motors. Why satellite actuators,? here they are very cheap complete with the 220v power supply/controller (50USD) which is controllable via the antenna socket with DISQ? which is easily generated on the pin of a pic. The same pic can monitor the sensor in the actuator to confirm commands are performed. Plus they can be cut down from 18 inches and are better than anything I can fabricate locally to do the same job. Possibly a bit slow but if you want fast up goes the weight, power requirements, and cost.

So now it stands in the double garage which also had to be modified to give height clearance, in all its glory waiting to have the sim 1 modified and dropped in. along the wat i realised sim 1 was only built with1.5 inch anle was not up to the grade. So now i am building a new sim base and frame to renovate the old sim 1 up to strength and dual pilot. ie, full rebuild. The last 4 weeks, and over 40 bearings have gone into the dual rudder pedals with force feedback, centering units and auto pilot control. currently working on the dual yokes which will be a similar setup, but thats another strory


As for the cockpit, aircraft style adjustable seats subwoffers, and modified genuine instruments add up in Kilos very quickly, I think the ally TQ is over 15 kilos, then add a couple of fat guys and a case of beer!

Fortunately all of the pics and half a dozen PC motherboards are pretty nominal in the weight game. Ah plan to run your PC code and OS of thumb sticks in ram, HDs dont like this kind of motion!

Any way there a few out dated pics on my site in the sim 2 album if you are interested.
http://www.bali-gold.com/Avionics/th...ls.php?album=8

Also, theres no drawings, except the acad of octagons for the motion base to cut the steel.

reg Harry

[TheFearow]

Hi Matt,

Based on a scan of the topic I suspect you are heading toward building a sim similar to what I have been working on nearly every day for the last 4 months.

If so, i can relate a bit as to where you are headed, not to frighten you off, but to assist you if you are deviating from the normal plus minus 30 degree type motion platform. I will describe what i have been doing and mention the additional s that crop up.

Briefly my sim 2 stated out as a rotating motion assembly into which i would transplant plant my single seat generic sim 1 now in the lounge room which is built with a steel frame with a view to motion

My sim 2 consists of a rotating platform 3 meters in diameter, on top of which sits a gimbal frame 1.7 metre above the rotating table (as in gyro), in this gimbal frame (just under 3*2 mtrs), sits the cockpit it self. The original scope was for a full Boeing size cockpit but for now to take the sim1 single pilot cockpit.

I'm still planning for a similar-to-Boeing cockpit, with quite a few customizations, to be a sort of custom-designed aircraft.

So we have unlimited pitch, roll and yaw for 360 degrees. Yaw in the rotating base, roll in the gimbal on the base then pitch with the cockpit inside the gimbal. Power flows and data through sliprings on the 3 bearing axis's.
I considered heave and surge but the shed is just not big enough and nor is the mains supply.

I'm thinking mostly the same, except the sliprings would only carry power and emergency stop signals, the motors themselves would be controlled wirelessly (although I may switch to a 2-pin bus for controlling them through the sliprings). At this point I think I am going to add Heave, but Surge is out, I don't want the complexity. And it's not one of the most important ones, at least not during flight. I'll use tightening seatbelts as I've seen on some designs to get a braking effect.

For a start without the cockpit and the access stairway and retracting walkway, there is 400 kg of 50mm*100mm steel box, and quite a few 6 mtr lengths of assorted size steel bar. 10 1 inch flange bearings, 5 1 inch custom machined shafts, 5 custom machined 1 inch boss/flanges plus the sliprings and 8 steel roller wheels.

There's a lot of stuff that goes into this. I'm not the best metalworker, is it worth studying into this more as well?

I calced out wheelchair motors would move every thing fast enough via a suitable reduction drive from 24volts. only problem was switch mode supplies i could find were not really up to providing the required peak 40 plus amps. Add 2 truck batteries to the weight on the rotating platform. I figured one motor on each axis to be enough as long as the sim was balanced but worked on using 2. So far one motor rotates the gimbal and platform 360 degrees in just under 2 seconds(no cockpit installed as yet). Here in Bali there is no source of suitable reduction drives, but motor bikes are dirt cheap. it turns out they run 15 to about 40 teeth to drive the back wheel, fabricate a boss for the motor and weld on a 15, then an idler with a 15 and a 42 tooth, then another custom made 1inch boss with 42 tooth and 2 chains. and its more than mobile enough for a flightsim, probably even a fighter but thats not the aircraft dynamics I plan to simulate. Dont forget you might want to stop and reverse this moving mass quickly.

I've got less of a problem on supply, with the house wiring being DC at 12/24v, and offering a lot of amperage. Reduction drives etc I can get through an engineer friend, nice and cheaply hopefully. Or rip them out of other things as you did . And for stopping, then plan was to use brakes (the same ones used in the safety system) assist the motors in direction changes by slowing the mass in the direction it's going.

Ok the cost of those machined parts here in Bali probably ran to 300 plus USD , but we are adding kilos all the time, and these are moving kilos that the motors must be able to control safely while the weight is moving fast and has a lot of leverage. ( ie upto 2 meters from the rotation axis). Consider flex and torsion in you plans, also metal fatigue and stress points. I think you will ditch wood and ally if you are building some thing similar to me.

I think the strength of the design in my case is improved since it's attached to the solid building at both top and bottom, but I can see what you mean by having to use stronger materials.

Based on the results achieved with 1 wheelchair motor for the rotating platform and 1 for roll on the gimbal which are both mounted on the platform, I figured i would go with 1 on the gimabal frame for the cockpit roll. Thus 2 meters of 50mm*100mm steel box filled with scrap steel and concrete (28KG)is added diagonally opposite the pitch motor to restore the balance on the gimbal frame in lei of the second motor and drive.

Balance is important and difficult to perfect in a spheroidal machine with out huge motors, buy an electronic scale!

With what I'm looking at, the motors would be in pairs and evenly spread across, so balance of them isn't a problem. Balancing the sim will be, so I'll have to counterweight that somehow.

If you don't have a hoist in the roof, i recommend you plan on building some kind of removable lifting system in the towers that hold the gimbal to lift it and later the cockpit into the gimbal. 6mm steel rope, steel gate rollers and a 1 ton chain hoist worked for me.

It's going to be in a purpose-built room, so I will probably add a hoist in the center of the assembly on the roof, and probably two separate lesser ones on either side, to make moving the simulator and such into place a lot easier.

Next consider how the sim will be kept stable on both axis when getting in and out. add more electric actators and steel locking pins complete with the mechanisms to move them and the (dueled for safety) sensors to control them.

I had planned for locking pins as well as friction brakes on all the chains, which would be safety locked, with a wired AND on safety switches as well as intelligent control for during operation.

Also how to get into and out of if? I ended up with a 2 metre high staircase and retracting walkway, add the other half of the double garage and another electric actuator plus 30 metres of 1 inch steel box and a few more sheets of 15mm plywood . Hand rails? add another 30 metres of steel rod and a bit more box.

My idea was to use a simple staircase on rails, with a pulley system to move it towards/away from the sim. If heave is added, which at this point I want to do, then the sim's height off the ground wouldn't be that much during park (at maximum negative heave).

All of this stuff needs to be made strong and safe, over engineer the steel work and lots of interlocks, you plan to ride in this thing, and probably take your kids, it need to be safe. This kind of machinery can take your fingers off, break your arms, or crush your body, or dice your kids while you fly. Big weights, powerful motors and lots of mass moving fast. Its a no go zone in the immediate vicinity

Since it's planned for a dedicated room, I'll have it integrated into my house locks (all doors use electronic locks) to prevent access while operating, as well as a multitude of sensors and cutoff switches to prevent anyone getting near it. I'll also have a camera system so I can monitor the simulator room while flying, if need be.

Obviously this kind of kit is not entrusted to Microsoft. every thing here is controlled by microchip pics and linux.

For control, I plan on controlling it with dedicated hardware, a bit more than PICs, most likely a customized real-time server, and probably running a customized real-time OS, although I'd use one based on Linux. Software is my specialty, so I know the requirements and best options there.

Also a balance adjust system is required unless you use huge motors, add another 100kg of steel and concrete a dozen more steel roller wheels and a few more actuators.

What exactly do you mean by balance adjust system? Do you mean like moving counterweights?

For linear actuators I have used a lot of 18 inch satellite dish positioning actuators, i anticipate a total of 10 complemented with 7 12v wiper motors and a handfull of electric car door lock motors. Why satellite actuators,? here they are very cheap complete with the 220v power supply/controller (50USD) which is controllable via the antenna socket with DISQ? which is easily generated on the pin of a pic. The same pic can monitor the sensor in the actuator to confirm commands are performed. Plus they can be cut down from 18 inches and are better than anything I can fabricate locally to do the same job. Possibly a bit slow but if you want fast up goes the weight, power requirements, and cost.

I'll have a look at those - they could be useful for a few things in my design, not just the motion system. Most of the motion in the design I have so far is done by geared-down motors directly, not linear actuators though.

So now it stands in the double garage which also had to be modified to give height clearance, in all its glory waiting to have the sim 1 modified and dropped in. along the wat i realised sim 1 was only built with1.5 inch anle was not up to the grade. So now i am building a new sim base and frame to renovate the old sim 1 up to strength and dual pilot. ie, full rebuild. The last 4 weeks, and over 40 bearings have gone into the dual rudder pedals with force feedback, centering units and auto pilot control. currently working on the dual yokes which will be a similar setup, but thats another strory

I've got plenty of space, from a dedicated room, and my sim design is being coordinated with motion system design from the start, so shouldn't be many problems there.

As for the cockpit, aircraft style adjustable seats subwoffers, and modified genuine instruments add up in Kilos very quickly, I think the ally TQ is over 15 kilos, then add a couple of fat guys and a case of beer!

I can see how much the average cockpit would weigh - as well as the fact that the cockpit design itself that I'm using is complex, various effect devices and such that I'm using certainly won't help the weight. Although I can't imagine it would get too ridiculous.

Fortunately all of the pics and half a dozen PC motherboards are pretty nominal in the weight game. Ah plan to run your PC code and OS of thumb sticks in ram, HDs dont like this kind of motion!

I'm going to be using customized low-profile and low-partcount computers off of SSD's, so no problem with motion causing problems there. And fans for everything, because convection cooling isn't the best when you tip everything upside down.

Any way there a few out dated pics on my site in the sim 2 album if you are interested.
http://www.bali-gold.com/Avionics/th...ls.php?album=8

Also, theres no drawings, except the acad of octagons for the motion base to cut the steel.

Very interesting, I've had a quick look and I'll be sure to read it in a bit more detail later. Looks good .

reg Harry

Thanks for the help/advice/suggestions/etc. I'm starting to get a much better idea of what I need to do etc. It's not a small job . I've got about 6 months before work can fully start anyway, so plenty of planning time!

-Matt

[kermit]

There's a lot of stuff that goes into this. I'm not the best metalworker, is it worth studying into this more as well?

Hi Matt,
Again , what do you know about materials?
If you want to throw a few hunderd pound of weight in all kind of directions,
You have to know about them.
Putting weight between 2 collums with a lengh of about 6.5 meter you will encounter flex, putting a lot of strain of joints and welds.
If you don`t know much about metalwork or gearing, you have to read and learn.
How do you want to make construction drawings without knowing what your joints,profiles,matrials can or can`t do?
Also if you can calculate the materials you know,
how much certain constructions will weigh and what you must use to be safe.
People have died or got into accidents ,
because they didn`t know how to make good welds or know how to secure joints or constructions.
I have a lot of experience in enginering but I don`t know no much about electronics so I have to learn or stay away.

May`be you can start to learn how to make good welds or make simple constructions just to know what you will encounter.
It won`t cost much, but you gain experience

What budget do you have,
greetz

[TheFearow]

Hi Kermit,

I know the basics about engineering and materials, strengths, flex, etc. What I'm not the best at, at least yet, is actually building things. I'm planning on doing a lot of study in my period before main construction/proper designwork starts, which is about 6 months, and I'll be doing scale tests etc. I also know a couple engineers who've said I can run designs past them if need be, which I'll definately do. They also offered to help with design and to help me learn things I'm not sure about, which will be helpful.
I'm also going to work on a few smaller projects in the mean time, which will help a lot I'm guessing.

As for budget, I'm not one of the people that expects a full motion system for $100. I've worked on similar projects professionally (although my job was never in the mechanical side), so I know the sort of money it takes to make them. Factoring in the amount I'm doing myself, or that I'm scavenging, It's still not a cheap hobby. I'm not sure on exact figures, but I know what I'm in for.

-Matt

[kermit]

Hi Matt,
I will follow your progress in your project.
Maybe you can explain the software you will be using,
As I`m working on a 2 dof with a option for 3 dof , for now I `m in contact with a inverter specialist.
To drive my platform with 220 volt AC motors and gearboxes, also still thinking about hydraulics
greetz

[simcraft]

Matt, based on your designs your cockpit seems very similar to the center of mass architecture we use for our motion systems. There is an interesting article that address the benefits (or lack of rather) of additional DOF beyond 3 (either RPY or RPH).

Basically the abstract is that professional airline pilots reported in almost all cases, that 3DOF sims produced motion simulation quality comparable to that produced by the much more expensive and complex 6 DOF Steward platform. The study was conducted using nine combinations of architecture and motion algorithms designed to provide a study of a broad range of motion simulating low and high frequency accelerations in all degrees of freedom.

Good luck with your project, correctly adding motion to your cockpit is a very rewarding experience.

Michael Boardman
SimCraft Information Officer