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Limit cycle stability of systems containing a pulse ratio modulator

Published online by Cambridge University Press:  04 July 2016

W. J. Alldridge
W. J. Alldridge*
Affiliation:
British Aerospace, Dynamics Group, Stevenage-Bristol Division
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Extract

Most spacecraft attitude control systems employing mass-expulsion techniques use some form of pulse modulation at the output from the control system to the gas control valves. In a number of early designs such modulation was introduced almost accidentally by surrounding simple relay-type switching logic with a feedback loop containing a first-order lag to provide ‘derived rate’ damping. This arrangement gives pulse width and pulse frequency modulation (Combined pulse modulation).

Such a modulation scheme was devised by Schaefer in 1962 which he called a Pulse Ratio Modulator (PRM). His main concern was the mechanisation of the quasistatic equations of the modulator and he did not investigate the stability of systems containing a PRM.

Type
Technical Notes
Information
The Aeronautical Journal , Volume 82 , Issue 814 , October 1978 , pp. 440 - 445
Copyright
Copyright © Royal Aeronautical Society 1978 

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References

1. Schaefer, R. A. A new pulse modulator for accurate DC amplification with linear or nonlinear devices. IRE Trans, Vol 1-1l , No 2, pp 34–47, September 1962.Google Scholar
2. Walk, R. and Rootenberg, J. Stability of combined pulse-modulated control systems. Int Journal Control, First Series, Vol 18, No 1, July 1973.Google Scholar
3. Mendel, J. E. On-off limit-cycle controllers for reaction jet controlled systems. IEEE Trans, Vol AC-15, No 3, pp 285–299, June 1970.Google Scholar
4. Alldridge, W. J. Limit cycle stability of systems containing a pulse ratio modulator. University of Bath, MSc Thesis, 1976.Google Scholar