Designing control force loading

[WJH308]

Tim,

We are talking about making the yoke actually shimmy and shake with the air pressure hitting the control surfaces of the plane as you fly. Control loading will make it harder to fly unless you trim the plane correctly just like if you were really flying.

Ever hit a serious bump in your car? It makes the steering wheel jump wildly. Same kind of thing.

Not so much as turbulence but when you fly a cessna or a piper, when I do some crazy unusual attitudes, and bring the airplane to a stall, I've had the roll axis on the yoke go completely limp as all airflow over the ailerons stopped, and as you pick up airspeed, the yoke gets much harder to move. And on the elevator, helps you set trim. In fact, I dare say, the pitch in most flight sims is so sensitive and hard to trim correctly simply because no one is using control loading on the controls. If anything, PC simulation should be much easier with proper control loading. This applies to Flight sims and car sims as well. Imagine if your playing R-factor and you can judge how well the front wheels are gripping based on the control loading. The front wheels start to skid, your control forces go down to nothing.
I am going to start out with a simple variant of control loading for the Spoiler lever in my L1011. In real life it is power assisted. If you disable the power assist with the little red button on top of the lever, "Considerable force is required to move it" So with it on, lets say it requires 4lbs of force to move it, and the servo keeps it positioned where I had it. Disable power assist, the loadcell now expects to see a 20lb force to move it, and it returns back to the forward position(Need to ask an L1011 pilot if that is accurate).
I might be able to get away with using a giant scale R/C servo for this. The servo will also drive the lever back and fourth for Direct Lift Control, and automatic ground spoilers.

[Jackpilot]

Like Tim, I have a hard time visualizing/figuring it out. Not the result, but how to achieve it with these neverheard-of-before gizmos.

I think nevertheless that if done , this "real flight" loading would be a terrific improvement (second to none but 3 axis mouvm.) and would make flying without it really "flat" !!

Worth explaining in more details and ,why not, some schematics ???

Very interesting.

[WJH308]

Like Tim, I have a hard time visualizing/figuring it out. Not the result, but how to achieve it with these neverheard-of-before gizmos.

I think nevertheless that if done , this "real flight" loading would be a terrific improvement (second to none but 3 axis mouvm.) and would make flying without it really "flat" !!

Worth explaining in more details and ,why not, some schematics ???

Very interesting.

I will be 100% honest with you all. As a pilot, I need a plan "B" and If I can make certain products for the flight sim community to sell to fall back on in case I ever lose my medical or do something stupid that the FAA does not like, I will NEED a plan "B". The other side of me is a huge champion of Open Source products, and also a champion of "Do It Yourself" projects. Being that I am just brain storming right now and have no products or technologies, just idea's, they are worth discussing so everyone can benefit from each other to strive for better experiences in all of our cockpits.
When I get a chance, I will make drawings in Solid works to post on the forum.

First things first, an MCU is a micro-controller, an integrated chip that is a miniature computer that you can program in either C or assembly language. I prefer the ATMEL AVR series. For this hobby, knowing how to program and implement microcontrollers into your cockpit is a huge benefit.

A load cell is a sensor that you can wire into a MCU that measures pressure. The load cell I purchased from Mouser is rated for 25lbs. Now I will know more when I receive it, but it puts out a voltage in proportion to how much force is applied to it, up to 5v which is standard. The MCU has Analog to digital converters and digital to Analog converters. It can measure the voltage output from the Load Cell and give it a numerical value that can be passed along to Flight Sim or drive other functions such as driving a linear actuators speed control.

A linear actuator is what your garage door opener is. A long worm screw that turns and drives a little trolley along a "way".

Now instead of driving your garage door, use it to move the yoke in and out. Take the yoke, mount it to the linear actuator, but between the linear actuator and the yoke is the load cell to measure force, and mounted to the linear actuator is your Potentiometer to measure location of the trolley. Hook all these things into a micro controller with some fancy programming and interfacing to flight sim, you have the basics for control loading.

Anyhow, the nice thing about programming is that it is FREE to get started.
C++ is fun. For 100$ you can start programming ATMEL AVR's. Buy an Atmel STK500 development board from either digikey or Mouser, a couple of MCU's, AND download the free AVR studio from ATMEL, and the FREE WinAVR IDE for programming.
avrfreaks.net is an excellent resource on ATMEL AVR's.

Other projects I am brainstorming include my own version of cockpit instruments like project magenta, but for the L1011 driven by OpenGL. Guys, if you can conquer this stuff and master it, there is absolutely nothing you CANNOT do for your sim.

[Mike.Powell]

Wittenstein Aerospace makes control loaders http://www.wittenstein.aero/170_580.htm as do Servos & Simulation http://www.servos.com/default.aspx and Moog http://www.moog.com/SimulationAndTes...ntrol_loading/

The sales literature may give you a few ideas.

Immersion http://www.immersion.com/ has a website that has lots of interesting tidbits about "haptics" another word for force feedback.

There had been an Asian company selling inexpensive load cells through Ebay. Some of the race car sim crowd were using them as force sensors for the car pedals. The company listed a broad range of load cells along with, I believe, postal scales. Naturally I can't find any Ebay listings now. I think the search term I used (successfully) in the past was "load cell". Perhaps they will resurface, and offer a low-cost source of load cells.

As an alternative to developing a control loading system using a force feedback loop, you might consider developing an open loop system which uses a force actuator. I wrote about such an approach here: http://www.mikesflightdeck.com/old_stuff.htm in the August 18, 2006 entry.

[Roland]

My method does not use springs, it uses a motor that drives the controls in a closed loop servo. By altering the servo gain, you will have more stiff or more sloppy control feeling. By altering the servo input offset, you can alter the zeroforce center. Another gentleman gave me a simpler idea, by driving the position pickup potmeter in opposite direction. works quite well.

Details can be found on http://www.simprojects.nl/diy_force_...nterfacing.htm

[ak49er]

I was perusing the Hagstrom electronics website today and it looks like they have a card for use with control loading. I didn't look into it much though, it may help.

[AndyT]

Two different kinds of load cells.
I was thinking of the artificial muscle type and you are using the sensor type.

Mine 'creates' the load and yours measures it. Both fit the design. what a weird coincedence.

[rsandor]

Hi everybody!

Just now joined Your forum, and already have to say something:
Load cells, are expensive by nature (those which are already conditioned and outputting voltage in range 0-5V). Unconditioned load cells are outputting extremely low voltage. A whole study required to eliminate problems related to temperature, and so on.
What if we mount a DC motor (with constant magnet as stator) as a constant mechanical load to pitch/roll mechanisms, and short circuit the rotor via a variable current regulator? It is relatively low mechanical load to existing mechanism if the circuit is open (current low), and a much greater load if the motor (a generator this way) is loaded by current. For now don`t know the the values of required motors, as it depends on a lot of factors, but this is an idea only.

Robert

PS: The motor may be a one with short circuited rotor, and a wound stator, but than the load can be regulated by voltage applied to stator.

[WJH308]

Hi everybody!

Just now joined Your forum, and already have to say something:
Load cells, are expensive by nature (those which are already conditioned and outputting voltage in range 0-5V). Unconditioned load cells are outputting extremely low voltage. A whole study required to eliminate problems related to temperature, and so on.
What if we mount a DC motor (with constant magnet as stator) as a constant mechanical load to pitch/roll mechanisms, and short circuit the rotor via a variable current regulator? It is relatively low mechanical load to existing mechanism if the circuit is open (current low), and a much greater load if the motor (a generator this way) is loaded by current. For now don`t know the the values of required motors, as it depends on a lot of factors, but this is an idea only.

Robert

PS: The motor may be a one with short circuited rotor, and a wound stator, but than the load can be regulated by voltage applied to stator.

I though about that, some frasca's use a linear actuator that changes the center position of the spring for simulating the trim setting.

[rsandor]

I though about that, some frasca's use a linear actuator that changes the center position of the spring for simulating the trim setting.

I`m not sure we are talking about same thing. Belove is a sketch. A DC motor free wheeling on the column mechanism gives a light load, but when the rotor of the motor (talking about a permanent magnet motor) is short circuitted by a switch, it will represent a much higher load. If we replace the switch by a current regulator modulated by the sim...

Robert
brakeoncolumn.jpg