A Five Minute Primer on Rotating Sphere Motion Simulators


A Simple Concept

The idea of using a spherical capsule to carry a passenger for motion simulation is more than 60 years old. Figures 5 and 2 below show a flight simulator from U.S. patent 2,344,454 filed by Loyd D. Plotner in 1942. The appeal of a spherical capsule design is that rotation around any combination of three axes (roll, pitch, and yaw) might be realized in an unlimited amount. Unfortunately, it appears that the Plotner design was never developed into a flight simulator.


  
 
Figure 2 showing drive mechanism and water supporting the capsule.

  

Space Race

Jumping ahead to the nineteen-sixties, the high rate of rotation that might occur during space flight prompted the development of the Rotational Flight Simulator.  This 6,400 pound spherical capsule measured 10 feet in diameter. This simulator could rotate a captive astronaut trainee up to 50 revolutions per minute. Now an artifact of the space race, the rotational flight simulator is currently stored at the USAF Museum of Aerospace Medicine at Brooks AFB.
 
 

Entertainment in Mind

Issued in 2000 to Elson et al., U.S. patent 6,017,276 uses rotary actuators that are orthogonal (at right angles) to each other. In order to rotate the capsule around an arbitrary axis, the actuators (item 31 in drawing) must provide transverse slippage. This means that the actuators provide traction along one axis only, and allow slippage in all other directions. How well this system might work on a full size, multi-seat simulator as shown in the patent is uncertain. Apparently, no simulator has been built to date using the Elson patent.
 

Drawing from Elson Patent – Item 7 is the access hatch

      

X1 Prototype –The First Xenosphere™

In 2001, a patent application was filed for the “Nimble virtual reality capsule using rotatable drive assembly”.  This resulted in U.S. patent 6,629,896. Figure 1A shows the most ambitious version of the simulator design. The single seat capsule is supported by compressed air pumped into air chamber (53).  Capsule roll and pitch is controlled by eight motors (48) driving rubber wheels (46). Capsule yaw is generated by rotating the entire drive assembly. The 1A version was not attempted, but a prototype similar to figure 6A below was built and evaluated.
  
 

Figure 6A shows a simulator with roll and pitch control.  The capsule was fabricated from composite materials and measured slightly under 8 feet in diameter.  The capsule shell, without contents, weighted approximately 300 pounds. The performance of roll and pitch rotation proved to be good. The ability to modify the axis of capsule rotation was also quite satisfactory. However, due to the fact that steel was used in the motor support structure, and that this weight would  prevent any sort of reasonable yaw performance, the decision was made to switch to the X2 prototype for further Xenosphere development.

The X1 prototype proved that a small, lightweight spherical capsule ringed by drive wheels is a viable design for motion simulation. It also reinforced the facts that the design, weight, and power of external drive components are all critical.

X2 Prototype – “Vertical Ring Simulator” (patent pending)

The X2 prototype is presently under active development. The drawing below shows the core principle. The horizontal motor “ring” of the X1 has been rotated to vertical, providing roll, yaw, and structural support for the capsule. The ring itself is rotated for capsule pitch control. Using the vertical ring for structural support eliminates the compressed air requirement of the X1.  It is hoped that the second generation Xenosphere will result in substantial improvement in the  capabilities of high performance motion simulation.


 

 

by Steve Jones
First edition
Copyright © 2006 Simulation Kinetics, Inc. all rights reserved.
Xenosphere™ Simulation Kinetics, Inc.