Patent GB-855655-A (GB)
Title: Improvements relating to interpolating or extrapolating devices for automatic machine tools
Inventor: VOLES ROGER
IPC: G05B19/4105
Filed: 1956-03-14
Abstract: 855,655. Electric analog calculating. ELECTRIC & MUSICAL INDUSTRIES Ltd. Feb. 28,1957 [March 14,1956]. No. 7907/57. Addition to 796,994. Class 37. General Apparatus for interpolating or extrapolating between electrical signals comprises two interpolating or extrapolating devices according to any of Claims 1 to 9 of the parent Specification and means for cascading said devices so that signals from the output terminals of the first device are applied in groups of at least three to the input terminals of. the second device, thereby to provide curvilinear interpolation between the amplitudes of the output signals from the first device. Construction In Fig. 1 a tape output reader and storage circuit 1 has six output points A.,B.,C., D.,E.,F.on which appear signals representing the values of a co-ordinate at successive reference points of a required locus; points A, C energizing the ends of a six section lineraly tapped autotransformer 2 whose intermediate taps are respectively connected to windings 3, 4, 5, 6, 7 of a.second transformer whose winding 5 is connected to the centre tap of 2 and with respect to which the other windings are symmetrically disposed and quadratically related in turns ratios so as to constitute a quadratic interpolator circuit as set forth in the parent Specification. Point B is connected to the end winding 5 remote from the centre tap of 2, while the point A, the free ends of windings 3, 4, 5, 6, 7, and the point B are respectively connected over leads a, b, c to threeway relay contacts rs7; over leads e, f. g to threeway relay contacts rs8; and from lead c, d, e to threeway relay contacts rs4. The output points D, E, F are connected in similar manner to tapped linear autotransformer 8 associated with quadratic interpolating windings 9 to 13; the points D and F are the free ends of windings 9 to 13 being respectively connected over the outlet leads h, i, j to threeway relay contacts rs9; over leads l, m, n to threeway relay contacts rs10; and over leads j, k, I to threeway relay contacts rs3. The outputs of rs7, rs8, rs9, rs10 are respectively parallelled to threeway relay contacts rs1, rs6, while output points A.,B.,C., D.,E.,F., are respectively connected to threeway relay contacts rs2, rs5. Tapped linear autotransformers 14, 20 provided with quadratic interpolating windings 15 to 19 and 21 to 25 similarly to transformers 2 and 8 are respectively energized at their ends and at the centre interpolating windings 17, 23 from the combined outputs of threeway relay switches rs1, rs2, rs3 and rs4, rs5, rs6; while the ends of the winding of transformer 14 are connected to half contacts at either end of a semicircle of contacts b 1  1 of a rotary switch, and the ends of transformer 20 are similarly connected to half contacts at either end of a semicircle of contacts b 2 ; intermediate. contacts being connected to the corresponding free ends of windings 15 to 19 and 21 to 25 of the interpolation transformers. Make before break contact 32 is rotatably traversed across the contact semicircles b 1 , b 2  by shaft 28, which is geared down 3:1 to drive a make before break contact 33 rotating over a circle of fixed contacts C  1  to C  6  to successively energize relays R 1  and R  7 ; R 4 ; R 1  and R 8 ; R 6  and R 9 ; R  3 ; R 6  and R  1   0  = from positive lead 31 over normally closed contact rsl of relay R11 =, while shaft 28 is also coupled mechanically to a control switch 26 receiving control signals from tape reader 1 over lead 34 to determine the operation of relay R11 and to control over line 35 the frequency at which groups of signals are read out from the recording tape. The tape reader and storage circuit 1 comprises (Fig. 3 not shown) five analog stores in the form of reference energized autotransformers with taps movable to positions representing signals to be stored, which are communicated from the tape reader together with recorded control signals which operate a sequence controller of the kind described in Specification 830,462 to selectively condition the respective-analog stores to receive each the appropriate signal. A selector switch is responsive to the sequence controller to connect selected groups of three of the analog stores to the respective outlets corresponding to A,B,C, D,E,F, (Fig. 1); the tape reader being operated at the required instants to read out groups of three signals in response to auxiliary signals from control switch 26 over lead 35. Operation Initially, signals representing successive values y  1,  y  2,  y  3  of a displacement y (e.g. of a machine tool element) for discrete equally spaced values X 1  X 2 , X  3  of a displacement x (or time parameter t) (Fig. 2) are applied to output points A, B, C of the tape reader, while signals representing successive values Y 3 , Y4, Y 5  are applied to points D, E. F, for discrete values of X 3 ,  X 4 , X 5  The resultant signals appearing on leads a, b, c, d, e, f, g of transformer 2 thus represent points Y 1 , Y 2 , y 3 , y 2 , y 5 , y 6 , Y 3  (Fig. 2) interpolated along a quadratic curve intersecting the points represented by signals  Y 1 , Y 2 , Y 3  at terminals A, B, C, while similarly the resultant signals appearing on leads h, i, j, k, l, m, n of transformer 8 represent points Y 3 , y 8 , y 9 , Y 4 , y 11 , y 12 , Y 5  interpolated between points represented by signals Y 3 , Y 4 , Y 5  at terminals D.,E.,F. An auxiliary signal from the tape record operates control switch 26 to de-energize relay R11, which changes over contacts rsl to energize relays R2, R5 closing contacts rs2, rs5. Signals at A, B, C are connected directly to the inputs of interpolation transformer 14 and signals at D, E, F directly to the inputs of interpolation transformer 20, so that rotating contact 32 derives interpolated signals on a quadratic curve passing through the points represented by A, B, C and D, E, F during one revolution. On receipt of a further signal from lead 34, control switch 26 releases R11 so that rs11 falls back and signals A,B,C, D,E,F, energize interpolation transformers 2, 8 directly. With rotating contact 33 on contact C  1  as shown, relays R 1 , R 7  are energized to close contacts rs1, rs7 and connect the outputs a, b, c of interpolating transformer 2 to the input points of the interpolating transformer 14; the rotating contact 32 interpolating over the output taps thereof connected to the semicircle of contacts b  1  to produce quadratically interpolated signals representing Y co-ordinates of points disposed along a parabola intersecting points represented by the already interpolated a, b, c signals. After a semi-circular rotation has been completed, contact 33 has moved to contact C 2  whereby relays R  1 , R 7  release, and' relay R  4  is excited to close switch rs4 whereby the outputs c, d, e of transformer 2 are connected to the input points of interpolating transformer 20; the contact 32 interpolating over the output taps thereof connected to the semicircle contacts b 2 , as before. On completion of the second semicircular rotation of 32, contact 33 has move to contact C  3  to release relay R  4  and excite relays R  1  and R 8. Switches rsl, rs8 close to connect outputs e, f, g of transformer 2 to the inputs of interpolating transformer 14, whose semicircularly disposed output contacts b  1  are again scanned in sequence by contact 32, until contact 33 engages contact C  4  to release relays R  1 , R  8  and energize relays R  6 , R9 so that contacts rs6, rs  9  are closed and outputs h, i, j of transformer 8 energized from inputs- D, E, F, are connected to energize interpolating transformer 20, whose outputs connected . to contacts b 2  are similarly scanned by contact 32. Subsequently for traversals of contact 32 over contacts b  1 , b 2  in sequence, contact 33 engages contacts c5, 5, c 6 in sequence to engergize relays R  3 , R  6  and R  1   0 , by which outputs j, k. l and l, m, n are successively applied to transformers 14 and 20, whereby semicircular contacts b 1 , b 2  are correspondingly energized. Thus when inputs A, B, C, D, E, F, are received from tape reader 1, sets of three interpolated signals' a,b,c; c,d,e, e, f,g; h,i, j; j,k,l; lm,n are successively derived, and are again in turn interpolated quadratically in response to the rotation of the shaft 29; a further range of A,B,C inputs being switchably derived from the tape reader while the D,E,F, inputs are being interpolated and vice versa, successively in a continous operation. Modifications Further linear subinterpolation may be' provided between the output signals derived from contact 32 as set forth in the parent Specification. Uniselectors may be employed in place of the relay switches and rotary contact switches. The number of interpolated input signals comprised in each switchable group may be greater than three. The interpolation circuits 2, 8 may each comprise (Fig. 4, not shown) an autotransformer having end connections and nine intermediate taps each connected to a contact over a quadratic interpolation winding; the inputs A.B,C and D,E,F being respectively connectible through multiple contact selector switches to selected groups of three contacts, and the outputs connected switchably in successive groups of three signals to interpolators 14, 20; thus enabling interpolation to be effected over the span of the input signals divided by factors of 1, 2, 3, 4 or 5 determined by the selector switch setting.