GB1459746A - Positioning systems for work-tables - Google Patents

Abstract

1459746 Automatic positioning control PYE Ltd 27 Dec 1973 [23 Dec 1972] 59578/72 Headings G3N and G3R [Also in Division H2] In the positioning of a member 10 for the, or each degree of translational freedom there is provided a retroactive control system, the actuator 12 being of the type wherein a control current derived from an error signal is supplied to a coil 12a, movable relative to a magnetic field in which it lies, to move the member. For two, or three degrees of freedom, there is a system for each, Fig. 1 (not shown), corresponding actuators being associated with a mechanical linkage accommodating member movement in those degrees of freedom not pertaining to the particular actuator. For setting the member at given positions, position selector switch 19 is associated with a set of potential dividers 18, see also (Fig. 1) providing equal, or pre-set increments between adjacent settings. For a plurality of degrees of freedom, the switches (19, 20 Fig. 1) may be independently settable, or mechanically coupled by linkage (24) associated with an indicator. A steady current may be supplied to the actuator at each position, the system acting as a holding loop. The switches may be replaced by relays, or solid state switches, or for progressive change of position in time, they may be replaced by required position signal generators whose outputs change continuously. Potentiometer 23 may allow for coarse positioning, or initial position setting. Network 37, 38, 39 provides for system damping. The desired and actual position signals may be in the form of voltages or currents. In use work-table 10 supports a thick film hybrid circuit, to various points on which conductors are to be connected. Actuator, Fig. 3, comprises a trunnion mounted housing supporting a permanent or electro field magnet 63 with pole pieces 63a, there being an annular pole piece 74, output element 68 with threaded bore 69 acting as a former for the coil, connected to terminals 64 and supported for translation by spiders 71, 75, or alternatively by a diaphragm, or rolling bearing arrangement. The body can be adjusted angularly by screw 77, then clamped using screw 76.