GB2045461A - Servo control system - Google Patents

Servo control system Download PDF

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Publication number
GB2045461A
GB2045461A GB7910188A GB7910188A GB2045461A GB 2045461 A GB2045461 A GB 2045461A GB 7910188 A GB7910188 A GB 7910188A GB 7910188 A GB7910188 A GB 7910188A GB 2045461 A GB2045461 A GB 2045461A
Authority
GB
United Kingdom
Prior art keywords
manipulating device
error
servo
during
work cycle
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB7910188A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
HALL AUTOMATION Ltd
Original Assignee
HALL AUTOMATION Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by HALL AUTOMATION Ltd filed Critical HALL AUTOMATION Ltd
Priority to GB7910188A priority Critical patent/GB2045461A/en
Priority to DE19803010628 priority patent/DE3010628A1/en
Priority to FR8006396A priority patent/FR2452134A1/en
Priority to IT12489/80A priority patent/IT1136160B/en
Publication of GB2045461A publication Critical patent/GB2045461A/en
Withdrawn legal-status Critical Current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
    • G05B19/33—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 analogue measuring device
    • G05B19/35—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 analogue measuring device for point-to-point control
    • G05B19/351—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 analogue measuring device for point-to-point control the positional error is used to control continuously the servomotor according to its magnitude
    • 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
    • G05B2219/41—Servomotor, servo controller till figures
    • G05B2219/41362—Registration, display of servo error

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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)
  • Control Of Position Or Direction (AREA)
  • Numerical Control (AREA)

Abstract

A servo control system controls an automatic manipulating device, so as to enable accurate positioning of the manipulating device and to eliminate residual errors in the positioning system. A data processor (3) outputs position data through a differential amplifier (5) to control a manipulating device (1) through an actuator (2). The actuator also controls a potentiometer (6) whose output feeds the differential amplifier (5) to achieve the servo control and is also fed to the data processor (3) as a signal representative of any residual positioning error in the servo system. This error is detected during the stand-by period of a work cycle of the manipulating device and is processed by the data processor so as to apply error correction during the work period of said work cycle to assist the manipulator to achieve its target position. <IMAGE>

Description

SPECIFICATION Servo control system The present invention relates to a servo control system and more particularly to such a system for controlling an automatic manipulating device, sometimes known as an "industrial robot".
It is an object of the present invention to provide a servo control system which enables accurate positioning of the manipulating member, e.g. an arm, of the manipulating device to be achieved and which seeks to eliminate residual errors in the positioning system.
According to the present invention a servo control system for controlling an automatic manipulating device includes means for detecting errors in the servo system during the stand-by period of a work cycle of the manipulating device and means for applying error correction during the work period of said work cycle.
Preferably the error correction to the servo system is applied during each work cycle of the manipulating device and the error correction applied during any one cycle is based on the error value derived immediately before the commencement of that cycle.
The invention will now be further described, by way of example, with reference to the accompanying drawing, which is a simple block diagram of one embodiment of servo control system according to the invention.
Referring to the drawing, the manipulator arm 1 of an automatic manipulating device is controlled by an actuator 2 which is in turn controlled by signals derived from a data processor 3, e.g. a microprocessor, in accordance with a programme stored in the processor for controlling movements of the manipulator arm 1. The output data from the processor 3 is fed through a digital-to-analogue converter 4 to one input of a differential amplifier 5 whose output voltage is applied to control the actuator 2 for the arm 1. The actuator 2 is also coupled to the slider 6a of a potentiometer 6 which is connected across a source of reference voltage and the voltage derived from the slider, which depends upon the position of the actuator 2 and hence of the arm 1, is fed to the second input of the differential amplifier 5 and is also fed to the processor 3 through an analogue-to-digital converter 7.
In operation, the data processor 3 outputs data representing a target position to be attained by the arm 1 during a work-cycle, under the control of its actuator 2. However, the actual position attained by the arm may not be exactly that of the target position due to a residual error in the servo system, and this actual position is indicated by the voltage derived from the slider 6a of the reference potentiometer 6. Besides applying this voltage to the differential amplifier 5 to achieve the servo control, the voltage is also fed through the analogue-to-digital converter 7 to the data.
processor 3 and this feeds back into the data processor a signal representative of any residual error in the servo system. This error is in fact detected during the stand-by period of the work cycle of the manipulator and is processed by the data processor so as to produce an error compensating value which is applied to the target position to be attained by the manipulator arm during its next work cycle.
More specifically, as will be appreciated, the residual error measurement detected will only be valid when it is known that the manipulator arm has ceased to move towards its target position. In order to ensure that it is this error measurement which is in fact employed, the data processor inspects the manipulator arm position values which are returned tb it until these values have remained steady for a certain period of time, which thus indicates that the arm has ceased to move. Thus the error compensating value employed at any one time is that derived immediately before a next work cycle commences, and this value is then held and used during all of that work cycle and is dependent upon the residual servo error at the moment of initiation of the work cycle.
It will be appreciated that an automatic manipulating device is generally capable of movement in several degrees of freedom, and that an actuator is provided for movement of the manipulating member along each of its axes of movement. In such a case a servo control system according to the invention would be provided for each axis.
The servo control system according to the present invention is an open loop system and therefore avoids the hunting difficulties encountered with closed loop systems and provides first order correction for the residual errors of the servo system.
1. A servo control system for controlling an automatic manipulating device including means for detecting errors in the servo system, and hence in the positioning of the manipulating device, during the stand-by period of a work cycle of the manipulating device and means for applying error correction during the work period of said work cycle.
2. A system as claimed in claim 1, in which the error correction to the servo system is applied during each work cycle of the manipulating device and the error correction applied during any one cycle is based on the error value derived immediately before the commencement of that cycle.
3. A system as claimed in claim 1 or 2, in which errors in the servo system are detected by means of a transducer whose output is applied to a data processor which outputs signals to control the automatic manipulating
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Servo control system The present invention relates to a servo control system and more particularly to such a system for controlling an automatic manipulating device, sometimes known as an "industrial robot". It is an object of the present invention to provide a servo control system which enables accurate positioning of the manipulating member, e.g. an arm, of the manipulating device to be achieved and which seeks to eliminate residual errors in the positioning system. According to the present invention a servo control system for controlling an automatic manipulating device includes means for detecting errors in the servo system during the stand-by period of a work cycle of the manipulating device and means for applying error correction during the work period of said work cycle. Preferably the error correction to the servo system is applied during each work cycle of the manipulating device and the error correction applied during any one cycle is based on the error value derived immediately before the commencement of that cycle. The invention will now be further described, by way of example, with reference to the accompanying drawing, which is a simple block diagram of one embodiment of servo control system according to the invention. Referring to the drawing, the manipulator arm 1 of an automatic manipulating device is controlled by an actuator 2 which is in turn controlled by signals derived from a data processor 3, e.g. a microprocessor, in accordance with a programme stored in the processor for controlling movements of the manipulator arm 1. The output data from the processor 3 is fed through a digital-to-analogue converter 4 to one input of a differential amplifier 5 whose output voltage is applied to control the actuator 2 for the arm 1. The actuator 2 is also coupled to the slider 6a of a potentiometer 6 which is connected across a source of reference voltage and the voltage derived from the slider, which depends upon the position of the actuator 2 and hence of the arm 1, is fed to the second input of the differential amplifier 5 and is also fed to the processor 3 through an analogue-to-digital converter 7. In operation, the data processor 3 outputs data representing a target position to be attained by the arm 1 during a work-cycle, under the control of its actuator 2. However, the actual position attained by the arm may not be exactly that of the target position due to a residual error in the servo system, and this actual position is indicated by the voltage derived from the slider 6a of the reference potentiometer 6. Besides applying this voltage to the differential amplifier 5 to achieve the servo control, the voltage is also fed through the analogue-to-digital converter 7 to the data. processor 3 and this feeds back into the data processor a signal representative of any residual error in the servo system. This error is in fact detected during the stand-by period of the work cycle of the manipulator and is processed by the data processor so as to produce an error compensating value which is applied to the target position to be attained by the manipulator arm during its next work cycle. More specifically, as will be appreciated, the residual error measurement detected will only be valid when it is known that the manipulator arm has ceased to move towards its target position. In order to ensure that it is this error measurement which is in fact employed, the data processor inspects the manipulator arm position values which are returned tb it until these values have remained steady for a certain period of time, which thus indicates that the arm has ceased to move. Thus the error compensating value employed at any one time is that derived immediately before a next work cycle commences, and this value is then held and used during all of that work cycle and is dependent upon the residual servo error at the moment of initiation of the work cycle. It will be appreciated that an automatic manipulating device is generally capable of movement in several degrees of freedom, and that an actuator is provided for movement of the manipulating member along each of its axes of movement. In such a case a servo control system according to the invention would be provided for each axis. The servo control system according to the present invention is an open loop system and therefore avoids the hunting difficulties encountered with closed loop systems and provides first order correction for the residual errors of the servo system. CLAIMS
1. A servo control system for controlling an automatic manipulating device including means for detecting errors in the servo system, and hence in the positioning of the manipulating device, during the stand-by period of a work cycle of the manipulating device and means for applying error correction during the work period of said work cycle.
2. A system as claimed in claim 1, in which the error correction to the servo system is applied during each work cycle of the manipulating device and the error correction applied during any one cycle is based on the error value derived immediately before the commencement of that cycle.
3. A system as claimed in claim 1 or 2, in which errors in the servo system are detected by means of a transducer whose output is applied to a data processor which outputs signals to control the automatic manipulating device in accordance with a programme stored in the processor.
4. A system as claimed in claim 3, in which the automatic manipulating device is controlled by an actuator which also controls the transducer and which is in turn controlled by the output of a differential amplifier having one input fed with the output from the data processor and its second input fed with the output from the transducer.
5. A system as claimed in claim 4, in which the output from the data processor is fed to said one input of the differential amplifier through a digital-to-analogue converter and the output from the transducer which is fed to the second input of the differential amplifier is also fed through an analogue-todigital converter to the data processor.
6. A system as claimed in claim 3, 4 or 5, in which a signal derived from said transducer and representative of any error in the servo system, and hence of an error in the position of the manipulating device, is processed by the data processor during the stand-by period of a work cycle so as to produce an error compensating value which is applied to the data representing the target position to be attained by the manipulating device during its next work cycle.
7. A system as claimed in any of claims 4 to 6, in which the transducer is a potentiometer device connected across a source of reference voltage and whose slider is coupled to the actuator, the output signal from the slider being applied both to said data processor and to said input of said differential amplifier.
8. A servo control system substantially as hereinbefore described with reference to the accompanying drawing.
9. An automatic manipulating device including at least one servo control system as claimed in any preceding claim.
GB7910188A 1979-03-22 1979-03-22 Servo control system Withdrawn GB2045461A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
GB7910188A GB2045461A (en) 1979-03-22 1979-03-22 Servo control system
DE19803010628 DE3010628A1 (en) 1979-03-22 1980-03-20 SERVO CONTROL SYSTEM
FR8006396A FR2452134A1 (en) 1979-03-22 1980-03-21 SERVO CONTROL DEVICE FOR AUTOMATIC HANDLING DEVICE
IT12489/80A IT1136160B (en) 1979-03-22 1980-03-24 SERVO CONTROL OR SERVOMECHANISM DEVICE

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB7910188A GB2045461A (en) 1979-03-22 1979-03-22 Servo control system

Publications (1)

Publication Number Publication Date
GB2045461A true GB2045461A (en) 1980-10-29

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB7910188A Withdrawn GB2045461A (en) 1979-03-22 1979-03-22 Servo control system

Country Status (4)

Country Link
DE (1) DE3010628A1 (en)
FR (1) FR2452134A1 (en)
GB (1) GB2045461A (en)
IT (1) IT1136160B (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0037489A1 (en) * 1980-04-03 1981-10-14 Dr. Johannes Heidenhain GmbH Method for automatic voltage offset compensation for numerically controlled machines
EP0136413A2 (en) * 1983-07-22 1985-04-10 International Business Machines Corporation System for automatically calibrating the space coordinates of a robot gripper in six degrees of freedom

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0057477A3 (en) * 1981-01-30 1982-08-25 Werkzeugmaschinenfabrik Oerlikon-Bührle AG Control circuit with balancing device
FR2572555B1 (en) * 1984-10-31 1987-12-31 Regulation Controle Indl Cie REGULATOR WITH AUTOMATIC COMPENSATION FOR STATISTICAL GAP
CN109278017A (en) * 2018-12-05 2019-01-29 安徽硕威智能科技有限公司 Localization method and its system of the robot in certain tracks

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0037489A1 (en) * 1980-04-03 1981-10-14 Dr. Johannes Heidenhain GmbH Method for automatic voltage offset compensation for numerically controlled machines
EP0136413A2 (en) * 1983-07-22 1985-04-10 International Business Machines Corporation System for automatically calibrating the space coordinates of a robot gripper in six degrees of freedom
EP0136413A3 (en) * 1983-07-22 1985-07-24 International Business Machines Corporation System for automatically calibrating the space coordinates of a robot gripper in six degrees of freedom

Also Published As

Publication number Publication date
IT1136160B (en) 1986-08-27
FR2452134A1 (en) 1980-10-17
DE3010628A1 (en) 1980-09-25
IT8012489A0 (en) 1980-03-24

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)