Tuesday, June 15, 2021

737-800 Sim 6dof Motion Platform

Just wanted to highlight Mike's 6DOF platform project and share here his words about it:

Regarding the design of the 6dof Motion Platform:   There is nothing super complex about its design.  It is modeled after the typical hexapod type design.   What is critical however, is deciding on the orientation/layout of the hexapod components.  These factors largely determine the size, complexity, and cost of the Motion Platform system.

I decided to use a Gearbox/Lever system to drive the hexapod actuators.   The main reason for this was ease of construction and low cost.   In my case, I purchased a 160:1 dual-reduction gearbox made by Grove Gear.   This gearbox incorporates a 1st stage Helical reduction, followed by a 2nd stage Worm reduction.  The Worm reduction prevents any “back drive” movement for safety reasons.  These gearboxes are very robust, having about 10 times the needed torque requirement.

Both the Motion Platform structure and the upper Flight Deck structure are weldments made with steel tubing.   The six Actuators are made using thick wall steel tubing, with 1” size steel Rod Ends on each Actuator.   I decided to use a 6” radius for the Actuator Lever on the output shaft of the gearbox.

There are many ways to design a Hexapod, and the approach that I have taken represents just one way of accomplishing the design and construction of a 6dof Motion Platform.  My approach to the design challenge was mainly constrained by my personal resources to build such a system.  Fortunately, I have my own personal machine shop, so machining and welding, etc. was not a problem.  As far as cost is concerned, I have about $15,000 invested in the motion platform material and system components.   This is relatively inexpensive compared to buying a commercial 6dof Motion Platform.   My Motion Platform is more of an experiment to see if I could build such a motion system on a “beer budget” that would yield an incremental level of Sim immersion to give a realistic sense of motion for ground/air flight operations using the 737-800 flight model.   I am very pleased with the results thus far, and I consider the time and cost worth the investment.

The input drive to the gearboxes is accomplished with six Servo motors.  These are very powerful servo systems, with high resolution encoders.  Each Servo motto is rated at 2.2 KW.  The Servo system is controlled by the Thanos AASD-15A Servo Controller, which in my case, is fed by the BFF 6dof Motion Control-software for outputting motion cues from the P3D flight simulator.   The Servo system is so powerful that careful “tuning” of the motion cues are required to prevent radical platform movements and related jolts that can induce extreme shock and vibration into the motion platform and related structures.  

Because people ride in the Sim Cockpit, it is to be considered a “life support system”, with related precautions and safety measures applied anytime the Motion Platform is in a “Powered ON” mode.  This type of setup needs to be taken seriously to prevent injury or worse.  I never work under the Motion Platform when it is powered is applied to the Servo Systems.  When starting and/or shutting down the Motion Platform, I always use a Check List to ensure it is done correctly each time.

I should also mention that when I first started this 737-800 Sim Project, I knew from experience with other big projects, that I wanted to fast-track the Sim build as much as possible.  In that regard, I chose Flight Deck Solutions for all the main Panel instruments and MIP structure.   Flight Deck Solutions are known for their high quality Sim components and systems.  I am proud to be a FDS customer, and from my personal experience, FDS customer service and product reliability is outstanding.

I also purchase the FDS Nose Section and Interior Panels.  All this gave me a huge head start on the 737-00 Sim construction.  Then I got the bright idea to add a 6dof Motion Platform to the Sim.  Designing and fabricating the Motion Platform greatly complicated the Sim Project.  However, I am now in the final stages of building the Sim, and expect to have it fully completer this year 2020.   This has been a 4+ year project.

San Diego, 2021

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