GB2121560A - A control system for two relatively movable members - Google Patents

A control system for two relatively movable members Download PDF

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Publication number
GB2121560A
GB2121560A GB08311830A GB8311830A GB2121560A GB 2121560 A GB2121560 A GB 2121560A GB 08311830 A GB08311830 A GB 08311830A GB 8311830 A GB8311830 A GB 8311830A GB 2121560 A GB2121560 A GB 2121560A
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GB
United Kingdom
Prior art keywords
value
control system
movable members
target value
parameter
Prior art date
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Granted
Application number
GB08311830A
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GB2121560B (en
GB8311830D0 (en
Inventor
Ronald Corbett Wainwright
Nicholas Martin Goy
John Douglas Anderson
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PA Management Consultants Ltd
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PA Management Consultants Ltd
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Publication date
Application filed by PA Management Consultants Ltd filed Critical PA Management Consultants Ltd
Priority to GB08311830A priority Critical patent/GB2121560B/en
Publication of GB8311830D0 publication Critical patent/GB8311830D0/en
Publication of GB2121560A publication Critical patent/GB2121560A/en
Application granted granted Critical
Publication of GB2121560B publication Critical patent/GB2121560B/en
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/19—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
    • G05B19/21—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path using an incremental digital measuring device
    • G05B19/25—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path using an incremental digital measuring device for continuous-path control
    • G05B19/251—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path using an incremental digital measuring device for continuous-path control the positional error is used to control continuously the servomotor according to its magnitude
    • G05B19/253—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path using an incremental digital measuring device for continuous-path control the positional error is used to control continuously the servomotor according to its magnitude with speed feedback only
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/34—Director, elements to supervisory
    • G05B2219/34215—Microprocessor
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/35—Nc in input of data, input till input file format
    • G05B2219/35436—Means, manual input, input reference, hand wheel
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/42—Servomotor, servo controller kind till VSS
    • G05B2219/42186—Master slave, motion proportional to axis
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/45—Nc applications
    • G05B2219/45178—Zoom, focus lens

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  • Engineering & Computer Science (AREA)
  • Human Computer Interaction (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Lens Barrels (AREA)

Abstract

Two members such as two movable lens groups in a multiple element zoom lens are moved in response to first and second information signals relating to the target value of a first parameter (largely dependent upon the position of a second of the two movable members) and a target value for the rate of change of a second parameter (largely dependent upon the position of the first of the two movable members). Target values are computed, depending on the last computed target value of the first parameter and the rate of change of the second parameter, and stored. A central processor unit is responsive to the stored values, and to information signals relating to the actual positions of the first and second movable members, to produce error signals which control a velocity servo control system error signals to adjust the rate of movement and direction of movement of the first and second movable members.

Description

SPECIFICATION An improved control system Field ofinvention This invention concerns control systems and in particular a system for controlling two independently movable members the positioning of one of which is dependent on the position of the other. Such a control system is of primary application in the field of zoom lenses but the invention is not in any way limited to this application.
Background to the invention It is known to provide electrical control of moving elements in zoom lens systems and United States Patent 4043642 is one example of an automated zoom lens system.
The control system described in specification 4043642 has two movable lens devices described as the first and second movable lenses and for photographing which involves zooming first the second movable lens is displaced along the axis of the lens for focusing and as the first movable lens is displaced, the amount of displacement is detected by a first detecting means and the second movable lens is then displaced based on the detected value of the movement of the first movable lens. The amount of displacement of the second movable lens is determined by a functional equation which is set up as the optical system is designed while the positional adjustment of the second movable lens is controlled by lens displacement means and second detecting means.Magnification variation is performed as a result of displacement of the first movable lens and of the second movable lens and the result is that no change in the focus condition of the final image takes place.
It is an object of the present invention to provide an alternative control system which can be used inter alia with the two movable lens groups of a zoom lens and which can be used to control the relative position of two movable elements such as the two movable lens groups in a zoom lens, in response to two control signals one of which dictates the position of one of the relatively movable members and the other of which corresponds to the rate of change of a parameter which is dictated by the position of the other relatively movable member, and in which the movement of the second movable member dictates a small change to be effected in the position of the first movable member for the criterion associated with the first movable member to be maintained.
As distinct from the control system described in the aforementioned U.S. Patent, the invention povidesfortargetvaluesto be fed into a drive system for moving the relatively movable members so that the drive system does not need to provide feedback signals to the control system but simply moves the movable members until the target positions are achieved whereupon the drive is terminated.
Such a system obviates the backlash and hunting characteristics associated with closed loop systems where the movement of one member interferes with the setting required for the other member.
Summary of the invention According to the present invention a control system for moving two relatively movable members comprises: (1) Means for generating first and second information signals relating to the target value of a first parameter (the first parameter value being largely dependent upon the position of a second of the two movable members) and a target value for the rate of change of a second parameter (the second parameter value being largely dependent upon the position of the first of the two movable members), (2) computing circuit means for computing a traget value of X for the position of the first of the said two movable members depending on the last computed target value and the rate of change of the second parameter, (3) signal storage means for storing the computed value of X for a given period of time, (4) further computing circuit means for computing from the stored value of X a target value for the position to which the second movable member is to move in the said period of time for which the value of X is stored, the second computer target value being denoted byY, (5) further computing circuit means responsive to the computed target value of Y and the desired parameter value from the first information signal means for computing a revised value of Y (Yr), (6) second signal storage means for storing the Yr signal for the same period of time as the X signal, (7) a central processor unit responsive to the store values of X and Yr and to information signals relating to the actual positions of the first and second movable members adapted to produce error signals Ex and Ey corresponding to any discrepancy between the actual positional value of the movable members and the target positional values, (8) a velocity servo control system responsive to the two error signals for controlling the rate of movement and direction of movement of the first and second movable members depending on the value and size of the error signals Ex and Ey respectively, and (9) means for generating stop signals to inhibit the velocity servo system when the actual position of each said member corresponds to the position determined by the target value for the time being for that member.
Conveniently the velocity servo system comprises a velocity servo, drive means controlled thereby, a tachometer for counting the number of revolutions to determine the rate of movement of the servo system and feedback means for combining the output of the tachometer with the control signal to the velocity servo.
Where the stored values of X and Yr are in digital values and/or the error signals Ex and Ey from the central processor unit are in digital form, digital to analogue converters are preferably provided for converting the error signals to analogue signals before they are supplied to the velocity servo systems.
Conveniently the stop signals are generated by the central processor unit from information relating to the actual positions of the movable members and the target positional values determined by the values X and Yr supplied thereto.
Conveniently the position of each movable member is determined by a transducer which converts the position of the movable member into an electrical signal preferably a pulse count for indicating absolutely relative to a reference position, the actual position of the movable member relative to the fixed position.
Where a high level of accuracy is required, an optical system is associated with each movable member for generating Moire fringes and a Moire fringe detector is provided for counting the Moire fringes as the member is moved relative to the optical system. By arranging that the detector produces electrical pulses corresponding to the number of Moire fringes counted, so a pulse count output signal is obtainable which can be accumulated by a pulse counter and delivered as an information signal of numerical value into the central processor unit for processing with the X and Yr signals.
The value of Yr may be computed using an algorithm built into the computing circuit means and conveniently the latter is adapted to produce an error information signal which is to be added to or subtracted from the target value of Y to produce the value of Yr.
Alternatively a so-called look-up table may be employed and a memory or store is provided in which a large number of different values of correction signal are stored for different values of X and Y and the appropriate correction signal is obtained by looking up appropriate values of X and Y.
The invention will now be described by way of example with reference to the accompanying drawing which illustrates by way of example only one form of control system for controlling two relatively movable lens groups in a four element zoom lens only in which the two other lens groups are fixed.
Detailed description of drawing In the drawing the two lens groups are denoted by 10 and 12 and are movable by means of drive means controlled by velocity servo systems 14 and 16 respectively. Associated with each servo system is a tachometer 18 and 20 respectively and the outputs from the tachometers 18 and 20 are supplied to input gates 22 and 24 respectively to control the velocity servo systems 14 and 16.
The absolute position of each lens group 10 and 12 relative to a fixed position is determined using Moire fringe counters comprising Moire fringe detector units 26 and 28 and counters 30 and 32 respectively.
The pulse count value corresponding to the absolute position of each of the lens groups 10 and 12 from the counters 30 and 32 are supplied to a central processor unit 34 which is programmed so as to compare the absolute pulse count values from counters 30 and 32 with target positional values supplied along data highways 36 and 38 so as to produce error signals along lines 40 and 42 denoted by Ex and Ey respectively.
The central processor unit 34 is typically a digit device so that the error signals Ex and Ey along lines 40 and 42 will also be digital signals and to convert these into analogue form, digital to analogue converters 44 and 46 are provided for supplying the other input signals to the gates 22 and 24.
Stop signals derived from the central processor unit are supplied along lines 48 and 50 to the digital to analogue converters 44 and 46 respectively, the stop signals being generated by the central processor unit whenever the pulse count value from 30 or 32 corresponds to the target value X or Yr along data highways 36 and 38 respectively.
The invention provides for the generation of the values X and Yr from two input signals derived from potentiometers 52 and 54. The first is adjustable by means of control 56 and the second by means of control 58 and the first is set to produce a voltage level the value of which corresponds to the focus distance at which an object is to be infocus in the image piane of the zoom lens.
The second potentiometer is set to produce a positive or negative polarity voltage from a mid position which zero voltage is produced, so as to produce a voltage whose polarity and magnitude determines the direction and rate at which the movement of the two movable lens assemblies is to occur. A large voltage is intended to correspond to a high rate of zoom and a small voltage to a low rate of zoom and the zero voltage at the centre of the control is intended to indicate no movementtherefore no zooming.
Preferably the control is centred by spring means so as to normally produce a zero voltage from the potentiometer. Zooming can then be achieved by moving the control to the left or to the right either by a small amount or a larger amount depending on the rate of zoom which is required. As soon as the required zooming has been achieved, the control is released to allow it to centre and produce a zero signal.
The voltages from the two potentiometers 52 and 54 are supplied to two read circuits 60 and 62 respectively to produce digital signals corresponding to the analogue values from the potentiometers for inputting via data highways 64 and 66 into a computing circuit 68. This may form part of the central processor unit 34 if required.
The computing circuit 68 produces a value of X along data highway 70 which is derived from the sum of the last stored value of X derived from a store 72 and a value derived from the rate of zoom called for by the second potentiometer control 58.
It will be seen that if a high rate of zoom is called for, then the second term will be greater than if a lower zoom rate is called for since in a given unit of time, if a high zoom rate is called for, the first lens elementwill have to be have moved much further than if only a low zoom rate is called for, over the same period of time.
The updated value of X is made available for insertion into the store 72.
The updated value of X is also supplied via data highway 74 to a further computing circuit 76 (which may also form part of the central processor unit 34) which is set to compute a target value of Y i.e. a target position for the second lens group.
The definition of Y is the position of the second lens group so as to obtain focus of an object at infinity for any particular value of X supplied to the computing circuit 76.
The final value of Y (Yr) is then computed by determining a correction signal AY. AY is computed from the target value of Y computed by the circuit 76 and the actual focus requirement (F) from the first potentiometer 52.
To this end a digital value corresponding to the desired focusing distance is supplied along data highway 78 to the further computing circuit means 80 (which may also form part of the central processor unit 34).
The correction AY is computed either by using a look-up table (i.e. a memory containing a large number of values of AYfor given values of X and Y, or by using an algorithm built into the computing function of the stage 80.
The value of AY is supplied to a further computing stage 82 via data highway 84 and the value of Y is supplied via data highway 86 then the computing circuit 82 is set to combine the two values of Y and AYso as to produce a revised Y signal Yr along data highway 88 for storage in a further store 90 (which may form parts of the stores 80 to 72 and both stores may form part of the central processor unit 34).
The output from the store 90 (when addressed) constitutes the Yr signal required for the central processor unit 34 along line 38 and the output from store 72 constitutes the X signal along data highway 36 for the central processor unit 34.
If the zoom rate control 58 is left at the zero position, a value of AY will be computed such that the value of Yr will achieve an infocus image in the focal plain of the zoom lens of an object placed at a distance from the zoom lens determined by the setting of the focus control 56. (This governs the value of the focus control signal from the potentiometer 52 and therefore from the read circuit 60).
The central processor unit 34 will thus be provided with a constant value of X and a value of Yr which will produce an error signal Ey until such time as the positional information from the Moire fringe counter 32 indicates that the second lens means is at the correct position required by the value Yr.
A zoom lens system incorporating the control system of the present invention is described in corresponding British Patent Application No.
8213361.
Reference is made to published US patent Specification 4368955 for information relating to a multiple element lens assembly to which a control system of the present invention may be applied.

Claims (9)

1. A control system for moving two relatively movable members comprising: (1) Means for generating first and second information signals relating to the target value of a first parameter (the first parameter value being largely dependent upon the position of a second of the two movable members) and a target value for the rate of change of a second parameter (the second parameter value being largely dependent upon the position of the first of the two movable members); (2) computing circuit means for computing a target value of X for the position of the first of the said two movable members depending on the last computed target value and the rate of change of the second parameter; (3) signal storage means for storing the computed value of X for a given period of time;; (4) further computing circuit means for computing from the stored value of X a target value for the position to which the second movable member isto move in the said period of time for which the value of X is stored, the second computer target value being denoted by Y; (5) further computing circuit means responsive to the computed target value of Y and the desired parameter value from the first information signal means for computing a revised value of Y (Yr); (6) second signal storage means for storing the Yr signal for the same period of time as the X signal;; (7) a central processor unit responsive to the store values of X and Yr and to information signals relating to the actual positions of the first and second movable members adapted to produce error signals Ex and Ey corresponding to any discrepancy between the actual positional value of the movable members and the target positional values; (8) a velocity servo control system responsive to the two error signals for controlling the rate of movement and direction of movement of the first and second movable members depending on the value and size of the error signals Ex and Ey respectively, and, (9) means for generating stop signals to inhibit the velocity servo system when the actual position of each said member corresponds to the position determined by the target value for the time being for that member.
2. A control system as claimed in claim 1 wherein the velocity servo system comprises a velocity servo, drive means controlled thereby, a tachometer for counting the number of revolutions to determine the rate of movement of the servo system and feedback means for combining the output of the tachometer with the control signal to the velocity servo.
3. A control system as claimed in claim 1 or 2 wherein the stored values of X and Yr are in digital form and/or the error signals Ex and Ey from the central processor unit are in digital form and digital to analogue converters are provided for converting the digital signals to analogue signals before they are supplied to the velocity servo systems.
4. A control system as claimed in any of claims 1 to 3 wherein the stop signals are generated by the central processor unit from information relating to the actual positions of the movable members and from the target positional values determined by the values X and Yr supplied thereto.
5. A control system as claimed in any of claims 1 to 4 wherein the position of each movable member is determined by a transducer which converts the position of the movable member into an electrical signal for indicating relative to a reference position, the actual position of the movable member.
6. A control system as claimed in any of claims 1 to 5 wherein an optical system is associated with each movable member for generating Moire fringes and a Moire fringe detector is provided for counting the Moire fringes as the member is moved relative to the optical system.
7. A control system as claimed in any of claims 1 to 6 wherein the value of Yr is computed using an algorithm built into the computing circuit means.
8. A control system as claimed in claim 7 wherein a memory is provided in which a large number of different values of Y determining informations are stored for different values of X.
9. A control system as claimed in claim 1 constructed and arranged to operate substantially as herein described with reference to the accompanying drawings.
GB08311830A 1982-05-08 1983-04-29 Control system for two relatively movable members Expired GB2121560B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08311830A GB2121560B (en) 1982-05-08 1983-04-29 Control system for two relatively movable members

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8213359 1982-05-08
GB08311830A GB2121560B (en) 1982-05-08 1983-04-29 Control system for two relatively movable members

Publications (3)

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GB8311830D0 GB8311830D0 (en) 1983-06-02
GB2121560A true GB2121560A (en) 1983-12-21
GB2121560B GB2121560B (en) 1985-10-30

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2141260A (en) * 1983-06-09 1984-12-12 Barr & Stroud Ltd Zoom lens assembly
US4653878A (en) * 1983-03-22 1987-03-31 Olympus Optical Co., Ltd. Microscope equipped with an electric device for driving revolver and stage
EP0241883A2 (en) * 1986-04-14 1987-10-21 International Business Machines Corporation Plural robotic drive

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4653878A (en) * 1983-03-22 1987-03-31 Olympus Optical Co., Ltd. Microscope equipped with an electric device for driving revolver and stage
GB2141260A (en) * 1983-06-09 1984-12-12 Barr & Stroud Ltd Zoom lens assembly
EP0241883A2 (en) * 1986-04-14 1987-10-21 International Business Machines Corporation Plural robotic drive
EP0241883A3 (en) * 1986-04-14 1989-08-16 International Business Machines Corporation Plural robotic drive

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Publication number Publication date
GB2121560B (en) 1985-10-30
GB8311830D0 (en) 1983-06-02

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