WO1983000834A1 - Procede et moyen de determination de la position d'un bras de travail - Google Patents

Procede et moyen de determination de la position d'un bras de travail Download PDF

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Publication number
WO1983000834A1
WO1983000834A1 PCT/SE1981/000246 SE8100246W WO8300834A1 WO 1983000834 A1 WO1983000834 A1 WO 1983000834A1 SE 8100246 W SE8100246 W SE 8100246W WO 8300834 A1 WO8300834 A1 WO 8300834A1
Authority
WO
WIPO (PCT)
Prior art keywords
arm
unloaded
work
work arm
robot
Prior art date
Application number
PCT/SE1981/000246
Other languages
English (en)
Inventor
Per Goeran Faxoe
Original Assignee
FAXÖ, Per, Göran
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 FAXÖ, Per, Göran filed Critical FAXÖ, Per, Göran
Priority to PCT/SE1981/000246 priority Critical patent/WO1983000834A1/fr
Priority to EP19810902573 priority patent/EP0087414A1/fr
Publication of WO1983000834A1 publication Critical patent/WO1983000834A1/fr

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J9/00—Programme-controlled manipulators
    • B25J9/02—Programme-controlled manipulators characterised by movement of the arms, e.g. cartesian coordinate type
    • B25J9/04—Programme-controlled manipulators characterised by movement of the arms, e.g. cartesian coordinate type by rotating at least one arm, excluding the head movement itself, e.g. cylindrical coordinate type or polar coordinate type
    • B25J9/046—Revolute coordinate type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J18/00—Arms
    • B25J18/002—Arms comprising beam bending compensation means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J19/00—Accessories fitted to manipulators, e.g. for monitoring, for viewing; Safety devices combined with or specially adapted for use in connection with manipulators
    • B25J19/02—Sensing devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J9/00—Programme-controlled manipulators
    • B25J9/16—Programme controls
    • B25J9/1679—Programme controls characterised by the tasks executed
    • B25J9/1692—Calibration of manipulator

Definitions

  • the present invention relates to a new method of determining the position of a work arm, such as a robot or manipulator arm, with high accuracy independently of the load on the work arm.
  • the invention also relates to a work arm, the position of which is determined in this manner.
  • An industrial robot generally comprises a work arm which is movable in one or more degrees of freedom and which in the free end thereof is provided with a grab means or the like for performing a desired operation, e.g. picking, lifting/moving etc.
  • the work arm may consist of several arm members which are pivotally or slidably connected to each other.
  • the position of said grab means is monitored by suitable sensing means, which are arranged at the respective connecting joint.
  • the angle between mutually pivoting , arm members may be determined with an angle sensor arranged at the connecting joint.
  • a location or position determination performed in such manner disregards plays and material deflections in the robot arm itself.
  • the precision of the grab means will hereby be so reduced that operations requiring greater precision, e.g. various processing operations, are rendered difficult.
  • Various approaches have been made to manage this problem.
  • the U.S. patent application 4,119,212 describes a method of eliminating the effect of load deformations of a robot arm having a pivotal joint.
  • two linking elements of known lengths interconnected through a free-floating pivotal joint are used, the free ends of which elements are pivotally coupled to the robot arm hand and mounting end, respectively.
  • the location of the work hand may be determined. Since the linking elements do not support any load the determination will be independent of any deformations of the very robot arm through great loads.
  • This method of position determination has, however, several limitations and may in practice hardly be applied to pivoting in more than one plane.
  • This is made possible by relating the position of the work arm to an ⁇ rl xxY ⁇ O PI unloaded position determining arm which is substantially independent of the work arm and arranged in connection with the work arm.
  • the method of the invention may advantageously be used in all kinds of loaded work arms, where it is necessary to determine the position of the operative end portion of the work arm with great precision. It is, however, particularly suitable for such work arms as robots or manipulators.
  • the unloaded arm is arranged such that the work ar substantially follows the movements of the unloaded arm, or vice versa, said arms having separate drive systems.
  • the unloaded arm may possibly be wholly or partially arranged outside ⁇ iie work arm, but it is preferably arranged within the same and suitably has the corresponding number of joints or pivotal sites as the work arm or the loaded arm.
  • the relative position determination between the loaded and unloaded arms may be made in various ways. Suitably, it is effected by appropriate means arranged in the respective free end portions of the arms which permit an accurate determination of the distance between defined parts of said end portions in the necessary directions.
  • Such devices or systems for sensing small position changes between parts which are movable relative to each other are known per se and may, e.g., be based upon measuring units or sensors of the contact-free as well as non-contactfree type.
  • inductive sensors magnetic sensors, such as, e.g. field-plates (Hall generators), pneumatic sensors, mechanical sensors, such as strain gauges, hydraulic balancing valves, optical sensors, and the like may be mentioned.
  • the position sensing may be arranged such that either the loaded arm o the unloaded arm is the measuring arm, i.e. that the loaded arm senses its position in relation to the unloaded arm, or vice versa.
  • a resulting differentia signal may then be utilized to move one of the two arms, such that a predetermined mutual blancing position of the arms is reset.
  • a position determination of the work arm or the loaded arm i obtained which is not affected by material deflection or plays.
  • the adaptation of the movements of the two arm systems in relation t each other may be effected with known control circuits for the drive means o the two arm systems, which drive means, for example, may be electric o hydraulic.
  • the loaded as well as the unloaded arm may function as the drivin arm, i.e. the arm which is directly actuated to perform the desired movements and to which - in case of a robot arm - the program unit is connected.
  • the drivin arm i.e. the arm which is directly actuated to perform the desired movements and to which - in case of a robot arm - the program unit is connected.
  • a robo or manipulator according to the invention there are thus two separate control o servo-systems, which suitably are stabilized in relation to each other in per s known manner.
  • Figure 1 is a diagrammatical side-view elevation of a robot ar according to the invention
  • Figure 2 is a diagrammatical perspective view of the position deter mining part of the device shown in Fig. 1,
  • Figure 3 is a principal diagram of a servo-system for the slave-unit o the device shown in Fig. 1, and
  • FIG. 1 is a principal diagram of a servo-system for the master-unit o the device shown in Fig. 1.
  • the robot shown in Fig. 1 which is designed to be mounted to a floor, wall or the like, comprises an outer robot arm 1 and a substantially completel self-supporting inner robot arm or master robot 2 therein.
  • the outer robot arm 1 constitutes the loadable work arm of the robot and is therefore dimensioned with regard thereto, while the inner robot arm 2 only is intended to be a "measuring arm" which is not loaded and thereby may have considerably thinner dimensions.
  • the outer robot arm 1 is composed of three arm parts, viz. a base part 3, an intermediate part k and an outer part 5, at the end of which a wrist 6 is mounted which optionally may be pivotal in several degrees of freedom. .
  • the wrist 6 is provided with suitable means for the work moments to be performed by the robot, e.g., a grab means.
  • the base part 3 is pivotally attached to a bottom plate
  • the intermediate part 4 is at one end thereof pivotally mounted to the base part 3 for rotation about .an axis of rotation A. In its opposite end the intermediate part is pivotally connected in the same way to the end of the outer part 5 opposite to the wrist 6 to permit rotation about an axis of rotation
  • the robot wrist 6 shown in the Figure may thus be caused to occupy a desired position by rotation of the arm parts .and 5 about the axes A and B, respectively, and by rotation of the robot arm about its "longitudinal axis" via__ the base part 3.
  • the desired pivotal movements are effected by means of suitable, e.g. hydraulic or electric, actuators arranged in suitable manner at the respective pivotal joints. Said actuators are controlled by a first servo-system, as will be described further below.
  • the inner unloaded robot arm or master robot 2 (which for the sake of clearness is in drawn in dashed lines in the Figure) is, in similar manner to the outer robot 1, in the shown case composed of three pivotally connected arm members, viz.
  • the base part 8 is, in the same way as the base part 3 of the outer robot 1, pivotally mounted about its longitudinal axis in a mounting portion 7a (possibly a part of the mounting plate 7) which in turn is attached to the floor, the wall etc., preferably totally independent of the attachment of the outer robot 1.
  • the base part 8 is pivotally connected to the intermediate part 8 through a pivotal joint .
  • C the intermediate part 9 is at its opposite en pivotally connected to the outer part 10 through a pivotal joint D.
  • the axes of rotation A and B of the outer robot may possibly pass through centre holes i the joints 11a and lib, respectively.
  • the inner robot arm 2 is provided wit suitable drive means, e.g.
  • sensors 11a, lib and lie e.g. potentiometers are arranged at the pivotal joints for sensing the relativ angular position of the arm parts.
  • the control of said drive means is effected b means of a second servo-system, as will described further below.
  • the free en 10a of the outer arm part 10 of the master robot 2 is in suitable manne surrounded by three pairs of sensors 12a - 12c arranged inside the arm part 5 o the outer robot 1. In the shown case the end portion 10a together with th sensors 12a - c form a contact-free three-axled balancing device.
  • th sensor pair 12a is arranged to sense and balance the rotation about the abov mentioned joint D, while the sensor pairs 12b and 12c in corresponding manne sense and balance the rotation about the joint A and about the longitudinal axi of the base part 8, respectively.
  • An embodiment of the above mentione balancing device is shown in Fig. 2.
  • the latter comprises an armature 13 of low remanence iron, which is arranged to be mounted at the free end of the arm par 10 of the inner robot 2, e.g. through bores 14 in a fore mounting portion 15 of th armature 13.
  • the above mentioned senso pairs 12a - 12c are arranged in the form of six horseshoe-formed permanen magnets, at one branch end of which field plates 17a-c of Hall generator type ar arranged, i.e. thin plates .based upon semi-conductor material the output voltag of which in a magnetic field are dependent on the flux density.
  • the horsesho magnets 12a-12c are, as mentioned above, attached to the inner side of the en portion of the outer robot 1 and spaced somewhat, e.g. up to some centimeter to the armature portion 16. For reasons that will appear below the length of th inner robot 2 should be. adjusted such that the outer robot 1 cannot b straightened out completely.
  • Fig. 3 The fundamental construction of the above mentioned servo-system fo the outer robot or slave robot 1 appears from Fig. 3, showing a partial servo system for one of the sensor pairs 12a-c corresponding to movement of the oute robot 1 in one of the sensing directions.
  • the two other partial servo- systems fo movement of the robot arm 1 in the other sensing directions are, of course constructed in identical manner.
  • the shown partial servo-system comprises a per se conventiona measuring bridge IS having two field plates (Hall generators) 17 connected to constant current source 19.
  • the field plates 17 are each connected to an input o an OP-amplifier 20.
  • the output of the latter is connected to a second OP amplifier stage 21, which in turn is connected to a servo-control means 22 fo actuation of the drive means for rotation at the intended pivotal joint.
  • the drive means in question is a hydraulic motor
  • the servo-control mean 22 is a servo-valve.
  • a velocity sensor 24 e.g. a tachometer sensing th relative velocity of movement of the arm parts is connected to the input o amplifier. 22 for introducing a negative compensating or stabilizing signal.
  • a compensating signa controlling the amplification of the amplifier 21 is fed in suitable manner from central program unit 25 for the robot via a digital/analogue-converter 26a.
  • FIG. 4 A corresponding principal diagram for the servo-system of the maste robot 2 is shown in Fig. 4.
  • the above mentioned central program unit 25, whic contains the desired control program for the master robot 2, is connected to servo-amplifier 27 via a digital/analogue-converter 26b.
  • the latter is in tur connected to servo-control means 28, which, e.g., are servo-valves when the drive means for effecting a desired rotation at the pivotal joints of the master robot consist of hydraulic motors.
  • the hydraulics and mechanics actuated by the servo-valve 28 are represented by a block 29.
  • the sensors at the three pivotal joints (11a, l ib, l ie) mentioned in connection with Fig. 1 are represented by an inductosyn measuring scale 30.
  • the latter is for sensing connected to a phase/pulse unit 31 via an amplifier 32 and fed back to the phase/pulse-unit via
  • OMPI an amplifier 33 and a band-pass filter 34.
  • the phase/pulse-convertor 31 is further connected to an Up/Down-counter 35, which in turn is connected to the central program unit 25 for reading. The reading is done periodically by means of a system clock 36.
  • the industrial robot shown in the Figures operates in the following way.
  • the totally unloaded master robot 2 is, as mentioned above, controlled in a predetermined manner through the central program unit 25 (Fig. 4).
  • the digital signals from the program unit 25 are converted in the D/A-converter 26b, amplified in the servo-amplifier 27 and fed to the servo-valve 28, which gives the desired actuation of the hydraulic motors at the pivotal joint or joints in question (C, D or the "rotational joint").
  • the angular position of the sensors 1 la
  • the inductosyn measuring scale 30 lie arranged at the pivotal joints of the master robot 2 are indicated by the inductosyn measuring scale 30.
  • the latter is sensed by the phase/pulse-unit '3i by feeding with a reference signal (e.g. 1-5 kHz), the angular value of the inductosyn measuring scale 30 determining the phase of the feedback signal.
  • the phase value is converted into pulses which are counted in the counter 35.
  • the program unit 25 periodically reads the counter 35 on signal from the clock 36 (e.g. 100 Hz), processes the read value and feeds the necessary control signals to the servo-amplifier 27 and the D/A-converter 26. . Any change of the relative position of the end portions of the outer arm
  • the armature 16 is displaced in relation to the horseshoe magnets 12 (Fig. 2), the magnetic field of the field plates 17 in question being changed.
  • the resulting differential signal is amplified in the OP-ampiifier 20 and led to another amplifier 21 together with the stabilizing signal from the velocity sensor 24.
  • the amplification of the amplifier 21 is controlled in dependence of the degree of extension of the work arm through a compensating signal from the program unit 25 via the D/A-converter 26a.
  • the output signal from the amplifier 21 passes to the servo-valve 22.
  • the latter therr actuates the hydraulic motor or motors in question at the pivotal joints of the slave robot 1, such that the balance is restored in the measuring unit 18.
  • the differential signal obtained from the measuring unit 18, which signal is essentially proportional to the movement of the master robot 2 may be processed by a separate microprocessor unit for maximum mutual stability of the two servo-systems to be obtained. Any movement of the inner robot arm or master robot 2 thus gives a corresponding movement of the outer robot or work robot 1.
  • th devices for the relative position determination of the loaded and the unloade arms may be designed in various ways using various types of sensors.
  • th control systems for the outer and inner robots may be arranged in other ways.
  • the numbers of degrees of freedom of the work arm and the unloade arm as well as the constructive design thereof may be varied.

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  • Engineering & Computer Science (AREA)
  • Robotics (AREA)
  • Mechanical Engineering (AREA)
  • Manipulator (AREA)
  • Control Of Position Or Direction (AREA)

Abstract

Procédé de détermination de la position d'un robot ou d'un bras manipulateur ou autre de manière à ce que la détermination de la position soit totalement indépendante des déformations des matériaux et du jeu pouvant avoir lieu pour de grandes charges s'exerçant sur le bras. Ceci est effectué en détectant la position du bras robotisé ou manipulateur (1) par rapport à un bras indépendant non chargé (2), dont la position peut être déterminée de manière précise et qui est agencé en association au bras de travail (2). L'invention concerne également un bras manipulateur ou de robot conçu pour une telle détermination de position.
PCT/SE1981/000246 1981-09-02 1981-09-02 Procede et moyen de determination de la position d'un bras de travail WO1983000834A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/SE1981/000246 WO1983000834A1 (fr) 1981-09-02 1981-09-02 Procede et moyen de determination de la position d'un bras de travail
EP19810902573 EP0087414A1 (fr) 1981-09-02 1981-09-02 Procede et moyen de determination de la position d'un bras de travail

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SE1981/000246 WO1983000834A1 (fr) 1981-09-02 1981-09-02 Procede et moyen de determination de la position d'un bras de travail

Publications (1)

Publication Number Publication Date
WO1983000834A1 true WO1983000834A1 (fr) 1983-03-17

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ID=20342900

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1981/000246 WO1983000834A1 (fr) 1981-09-02 1981-09-02 Procede et moyen de determination de la position d'un bras de travail

Country Status (2)

Country Link
EP (1) EP0087414A1 (fr)
WO (1) WO1983000834A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1986000557A1 (fr) * 1984-07-13 1986-01-30 American Telephone & Telegraph Company Dispositif de manipulation d'articles
WO1989002101A1 (fr) * 1987-09-01 1989-03-09 Fisw Forschungs- Und Ingenieurgesellschaft Für Ste Procede et dispositif de correction de la position des bras de robots industriels
BE1000768A4 (nl) * 1986-07-17 1989-03-28 Picanol Nv Meet- en stuurinrichting voor bewegende strukturen.

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4119212A (en) * 1977-07-18 1978-10-10 Western Electric Company, Inc. Monitoring the location of a robot hand

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4119212A (en) * 1977-07-18 1978-10-10 Western Electric Company, Inc. Monitoring the location of a robot hand

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1986000557A1 (fr) * 1984-07-13 1986-01-30 American Telephone & Telegraph Company Dispositif de manipulation d'articles
BE1000768A4 (nl) * 1986-07-17 1989-03-28 Picanol Nv Meet- en stuurinrichting voor bewegende strukturen.
WO1989002101A1 (fr) * 1987-09-01 1989-03-09 Fisw Forschungs- Und Ingenieurgesellschaft Für Ste Procede et dispositif de correction de la position des bras de robots industriels

Also Published As

Publication number Publication date
EP0087414A1 (fr) 1983-09-07

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