Browsing by Author "Healey, M."

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    Diffraction gratings - their principles and applications to machine tools
    (College of Aeronautics, 1963-12) Healey, M.
    The use of diffraction gratings as measuring elements on machine tools is nowadays an accepted procedure. Part I of this paper therefore sets out to give a brief understanding of the principles of diffraction gratings, and the ways in which they have been utilised commercially. In addition, comparisons are made with other reference elements and some consideration is given to manufacturing techniques. Part II of the paper deals in more detail with the pure theory of crossed diffraction gratings.
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    Hydraulic test rig
    (College of Aeronautics, 1964-08) Healey, M.
    Hydraulic Test Rig The rig comprises a grinding wheel head spindle driven by a motor and carrying an inertia load made up of detachable steel discs. On the opposite end of• the shaft to the motor is mounted a radial diffraction grating and a d.c. tachogenerator (see Fig. 1). Three motors are currently available, all with there own mounting brackets for easy changing: a) Vickers-Sperry, 6 axial pistons motor type MF-3906-30. b) Boulton Paul; 9 radial pistons with shaped cam track. c) Hartmann Rol-vane H.T.10 (Telehoist). Two types of spool valve are available: a) Dowty Moog, Series 22 b) Pegasus type 120. A manifold block is available to make the two Moog valves interchangeable. The Bolton Paul and Telehoist motors both have double ended shaft so that a tachometer can be mounted direct onto the motor. The tacho used in a Servo tech. (5 rads/sec./volt). The other tacho (mounted on the test rig) is an Evershed-Vignoles (7.9 rads/sec./volt). The Evershed is about 50% less noisy … [cont].
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    An investigation into high precision control of the relative angular position of two shafts over a range of speeds and ratios
    (College of Aeronautics, 1964-05) Healey, M.
    SUMMARY The paper sets out to describe how a servo mechanism may be applied to generative gear grinding machines and an appropriate specification is drawn up. The system involves separate motor drives to the two shafts, the angular positions of which are monitored with radial diffraction gratings. One of the signals is frequency divided to achieve the speed ratio between the two shafts, the resultant similar frequency signals being phase compared, any difference producing an error signal thus completing the servo loop. Hydraulic motors are used as prime movers. The transfer functions of the loop are developed and compared with measured open loop results. It is clearly shown that with the components at present available the loop cannot be made stable. The specification of more appropriate hardware is discussed and future work outlined, but the conclusion is reached that this system cannot be used for its primary purpose on a generative gear grinding machine.