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Introduction
This site (which is still under construction) contains information about my hobby activities on gyroscopically stabilised vehicles. It is based on the "Gyroscopic Monorail" invented by Louis Philip Brennan as described in his patents of 1903 onwards. A good resume' of his work can be found in the book "Louis Brennan Inventor Extraordinaire" by Norman Tomlinson and published by John Hallewell publications in 1980 (ISBN 0 905540 18 2). Early scientific accounts of his gyro monorail can be found in the technical documents referenced later.
Further inspiration for my work on this topic came from seeing the excellent models recently produced by Mr. MORI Hiroshi, in Japan,
http://www.youtube.com/watch?v=K6uEcjdjc4Q&feature=related,
 
I have produced my own version of the Brennan's model Monorail; see... 
http://www.youtube.com/watch?v=czlhQcmXuHc (apologies for poor quality of
video). It is only a basic platform so far (without wheels), but I hope to make a self
contained vehicle in the near future.
 
System Description
The image below shows the various parts of my system. Unlike Brennan's model, I have the two gyros arranged along the vehicles roll-axis, I am also using electronic means of sensing gimbal motion and generating the controlling torque. Nevertheless, the basic principle is the same.
 
 

The two gyros are ex aircraft directional gyros (DGs) and operate on a 3-phase variable frequency power supply I constructed using an 8-bit PIC Microcontroller and H-bridge drivers. The gyros are brought up to speed slowly using ramped-frequency square waves (the same for each phase) whist the drive current is monitored in order to find the operating frequency giving the lowest drive current. Both gyros run on the same driver but are orientated to spin in opposite directions. Feedback control, to accelerate gyro precession and make the system stable, is accomplished with a second PIC Microcontroller employing gimbal angle and gimbal rate monitoring via a simple potentiometer. The potentiometer signal is filtered by a 2nd order Bessel filter with a cut-off frequency of about 60Hz. The controller output drives a small dc motor via an H-bridge using pulse-width-modulation in order to vary the motor speed and acceleration. The feedback coefficients are adjusted via an RS232 interface to a PC running HyperTerminal then stored in the Microcontroller's EEPROM. All code was developed using Microchip's MPLAB Integrated Development Environment (IDE) and HI-TECH's C compiler operating in lite-mode. The whole system runs off a 12V power supply. This setup is being used to validate my theoretical modelling and control systems analysis. Once this is completed a larger self-contained model will be constructed.

 

Theory

One of the most reliable (and unbiased) sources of gyro theory relevant to this application, that I have found, is in a book by Professor Andrew Gray FRS: "A Treatise on Gyrostats and Rotational Motion - Theory and Applications", published by Dover Publications Inc, New York in 1918. The articles published by Brennan's co-worker, Mr. H. Cousins in the "Engineering" magazine issues of November 21 1913 pages 678-681, November 28 pages 711-712, and December 12 pages 781-784 are also extremely helpful. However, a number of more recent theoretical studies (for example; J.F.S. Ross in: "The Gyroscopic Stabilization of Land Vehicles" Published in 1933 by Edward Arnold & Co, London) although well worth reading, are less helpful since they suggest that the above method of stabilisation would not work. Doing this work, and using the same feedback principles as Louis Brennan and described by Mr. H. Cousins, (albeit with more modern technology) has really made me appreciate the engineering genius of these early pioneers.

 

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