WO2009020600A1 - Robots commandés par force - Google Patents

Robots commandés par force Download PDF

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Publication number
WO2009020600A1
WO2009020600A1 PCT/US2008/009412 US2008009412W WO2009020600A1 WO 2009020600 A1 WO2009020600 A1 WO 2009020600A1 US 2008009412 W US2008009412 W US 2008009412W WO 2009020600 A1 WO2009020600 A1 WO 2009020600A1
Authority
WO
WIPO (PCT)
Prior art keywords
force
robot
force sensor
force control
control
Prior art date
Application number
PCT/US2008/009412
Other languages
English (en)
Inventor
Jianjum Wang
Jianmin He
Mats Isaksson
Tomas Groth
Hui Zhang
Original Assignee
Abb Research 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 Abb Research Ltd. filed Critical Abb Research Ltd.
Publication of WO2009020600A1 publication Critical patent/WO2009020600A1/fr

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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
    • B25J9/16—Programme controls
    • B25J9/1628—Programme controls characterised by the control loop
    • B25J9/1633—Programme controls characterised by the control loop compliant, force, torque control, e.g. combined with position control
    • 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
    • G05B2219/39—Robotics, robotics to robotics hand
    • G05B2219/39319—Force control, force as reference, active compliance
    • 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
    • G05B2219/40—Robotics, robotics mapping to robotics vision
    • G05B2219/40287—Workpiece manipulator and tool manipulator cooperate

Definitions

  • This invention relates to force controlled robots and more particularly to the setup of such robots .
  • a force-controlled robot opens a new horizon of applications as a result of its controlled contact with the working environment.
  • a force-controlled robot has a force sensor and a force controller as compared to a position-controlled robot which does not have these elements.
  • the force sensor provides the measurement of the contact force between a mechanical unit and its interacting environment. The measured force is input into the force controller to change the motion of a mechanical unit in order to achieve a desired contact force.
  • a force control setup involves two mechanical units, namely the force sensor mounting unit where the force sensor is mounted, and the force-controlled unit on which the force control action is exerted.
  • mechanical unit as used herein has a rather broad meaning as it includes a multi-axis robot, single axis mechanism, conveyor, stationary object (world frame), and other mechanisms.
  • a force-controlled unit must be a drivable and controllable mechanism such as a multiple-axis robot and external axis, while the force sensor mounting unit can be anything.
  • Robot 11 has a faceplate 12, a force sensor 13 mounted on the wrist 11a of robot 11 and an end effector lib that, as is shown in Fig. 1, holds either the tool 14 that will perform work on a work object located elsewhere or the work object 14 that will be worked on by a tool located elsewhere.
  • tool as used herein means, without limitation, a conventional tool such as a grinding or deburring tool that is to perform work on the work object located elsewhere or a work object which is to be assembled with or used in the assembly of the work object located elsewhere.
  • the conventional setup further includes a controller 10 which contains the force controller and the software program which is used to control the motion of the robot in response to among other things an input from force sensor 13.
  • controller 10 is connected by cable 15 to the force sensor 13 and to the robot 11 by drive and measurement cable 16. Therefore as is shown in Fig. 1, the robot 11 is subject to force control action, that is, its motion will be altered in response to the measured force.
  • the software program can, as is described above, be resident in controller 10 or may be on a suitable media such as a CD-ROM or flash drive in a form that can be loaded into the controller 10 for execution.
  • the software program may be downloaded into the controller 10 by well known means from the same site where controller 10 is located or from another site that is remote from the site where controller 10 is located.
  • the software program may be installed or loaded into a computing device (not shown in Fig. 1) which is connected to controller 10 to send commands to the controller 10.
  • Fig. 1 While the conventional setup shown in Fig. 1 has its advantages such as compactness and relative closeness it lacks flexibility and suffers performance constraints. For each application at hand, a new setup should be pursued when the conventional one is inadequate in terms of cost and performance.
  • a system has : a robot having one object; a mechanical unit external to the robot having another object; a force sensor associated with either the robot or the mechanical unit; and a controller apparatus for providing force control in response to a signal from the force sensor when the one object comes into contact with the another object, the force control applied to the robot when the force sensor is associated with the mechanical unit and applied to the mechanical unit when the force sensor is associated with the robot.
  • a system includes: a robot carrying a first object; a mechanical unit carrying a second object, the mechanical unit being external to the robot and movable along a single axis; a force sensor positioned between either the robot and the first object or the mechanical unit and the second object; and a controller apparatus for providing force control in response to a signal from the force sensor when the first object contacts the second object, wherein the force control is applied to the robot if the force sensor is positioned between the mechanical unit and the second object and the force control is applied to the mechanical unit if the force sensor positioned between the robot and the first object.
  • a system includes: a first six axis robot carrying a first object; a second six axis robot carrying a second object; a force sensor associated with either the first robot or the second robot; and a controller apparatus for providing force control in response to a signal from the force sensor when the first object contacts the second object, wherein the force control is applied to the first robot if the force sensor is associated with the second robot and the force control is applied to the second robot if the force sensor is associated with the first robot.
  • Fig. 1 shows a prior art setup for a robot with force control .
  • Figs . 2 to 5 show alternative embodiments for the force control setup of the present invention.
  • Figure 6 shows a general control flow of a force controlled robot system describing how the motion of the force controlled unit is altered in order to maintain the desired contact force.
  • Fig. 7A shows the flow control for the prior art setup shown in Fig. 1.
  • Fig. 7B shows the gravity compensation in that setup and
  • Fig. 7C shows the transform from the sensor coordinate system to the work object coordinate system in that setup.
  • Fig. 8A shows the flow control for the embodiment shown in Fig. 2.
  • Fig. 8B shows the gravity compensation in that setup and
  • Fig. 8C shows the transform from the sensor coordinate system to the work object coordinate system in that setup.
  • Fig. 9A shows the flow control for the embodiment shown in Fig. 3.
  • Fig. 9B shows the gravity compensation in that setup and
  • Fig. 9C shows the transform from the sensor coordinate system to the work object coordinate system in that setup.
  • Fig. 1OA shows the flow control for the embodiment shown in Fig. 4.
  • Fig. 1OB shows the gravity compensation in that setup and
  • Fig. 1OC shows the transform from the sensor coordinate system to the work object coordinate system in that setup.
  • Fig. HA shows the flow control for the embodiment shown in Fig. 5.
  • Fig. HB shows the gravity compensation in that setup and
  • Fig. HC shows the transform from the sensor coordinate system to the work object coordinate system in that setup.
  • each of Figs. 2-5 shows an embodiment for the force control setup of the present invention.
  • each of those embodiments includes a controller 10 which, as in the conventional setup in Fig. 1, contains the force controller and the software program which is used to control the motion of the robot in response to among other things an input from force sensor 13.
  • the software program can, as is described above, be resident in controller 10 or may be on a suitable media such as a CD-ROM or flash drive in a form that can be loaded into the controller 10 for execution.
  • the software program may be downloaded into the controller 10 by well known means from the same site where controller 10 is located or from another site that is remote from the site where controller 10 is located.
  • the software program may be installed or loaded into a computing device (not shown in Figs. 2-5) which is connected to controller 10 to send commands to the controller 10.
  • the software program may include the software needed for one or more of the embodiments shown in Figs. 2 to 5 and if it does will allow the user to, in a manner well known to those of ordinary skill in the art, select the software to be executed for the embodiment of the present invention to be implemented by the user.
  • the present invention may take the form of a computer program product on a tangible computer-usable or computer-readable medium having computer-usable program code embodied in the medium.
  • the tangible computer-usable or computer-readable medium may be any tangible medium such as by way of example but without limitation, a portable computer diskette, a flash drive, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , a portable compact disc read-only memory (CD- ROM) , an optical storage device, or a magnetic storage device.
  • Computer program code for carrying out operations of the present invention may be written in an object oriented programming language such as Java, Smalltalk, C++ or the like, or may also be written in conventional procedural programming languages, such as the "C" programming language.
  • the program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server.
  • the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN) , or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider) .
  • LAN local area network
  • WAN wide area network
  • Internet Service Provider for example, AT&T, MCI, Sprint, EarthLink, MSN, GTE, etc.
  • Fig. 2 there is shown one example of a new setup where both the force sensor 13 and object 17 are stationary because they are, for example, sitting on a table 19 and are not, as is shown in Fig. 1, mounted on the robot 11.
  • the controller 10 receives the signal from force sensor 13 through force sensor cable 15 and is connected to the robot 11 by drive and measurement cable 16.
  • the benefit of the setup of Fig. 2 as compared to the setup of Fig. 1 is simple and accurate gravity and inertial compensation, as the gravity components of the sensor payload are constant instead of varying with the robot configuration.
  • the object 17 may either be an object to be worked on by a tool 14 ⁇ held by the robot 11 or a tool that performs work on an object that is held by the robot 11.
  • the external axis 18 may for example be a conveyor or some other device which is capable of motion.
  • Figs. 3 and 4 represent three cases. Cases 1 and 2 are both shown in Fig. 3 where for case 1 the force controlled unit is the robot 11 and the force sensor 13 is mounted on the external axis 18; and for case 2 the force controlled unit is the external axis 18 and the force sensor 13 is also mounted on the external axis 18. In case 3, which is shown in Fig. 4, the force controlled unit is the external axis 18 and the force sensor 13 is mounted on the robot 11.
  • the controller 10 receives the signal from force sensor 13 through force sensor cable 15 and is connected to the robot 11 and external axis 18 by drive and measurement cable 16.
  • an external axis 18 is more responsive to the motion change command from the robot controller 10 due to the smaller inertia. This setup is very beneficial for using the robot in a grinding application where small and rapidly changing contact force is to be controlled.
  • robots such as robot A 11 and robot B 20 as shown in Fig. 5.
  • the force sensor 13 is mounted on robot A 11, but robot B 20 is subject to the force control action.
  • both robots 11 and 20 are connected to controller 10 by an associated drive and measurement cable 16 and the end effector lib of robot 11 either holds the tool or work object 14 while the end effector 20a of robot 20 either holds the work object 17 when the end effector lib of robot 11 holds the tool 14 or the tool 17 when the end effector lib of robot 11 holds the work object 14.
  • Figure 6 shows a general control flow of a force controlled system describing how the motion of the force controlled unit 200 is altered in order to maintain the desired contact force.
  • the force controller module 100 computes the change of motion reference command ⁇ rfrom the difference between the desired ( F dei ) and measured contact force ( F comacl ) .
  • the modified motion reference (f + Ar) is then sent to force controlled unit 200 and affects its motion v .
  • the computing algorithm in force controller module 100 can be varied.
  • the commonly used computing algorithms in module 100 include but are not limited to damping control, admittance control, hybrid position and force control.
  • the force sensor 13 As the motion of the force controlled unit 200 is changed, its interaction force with the contacting environment is changed accordingly.
  • the measurement of the interaction force is performed by the force sensor 13, which as shown in Figs. 2, 3 (case 1), 4 and 5, can be mounted on a mechanical unit 300 different from the force controlled unit 200.
  • This mounting of the force sensor 13 on a mechanical unit 300 which is different from unit 200 is possible because the interaction force is mutual according to Newton's third law.
  • a force signal processing module 400 is used to perform the necessary computations, which include for example, low-pass filtering, gravity and inertial compensation, as well as transformation from one point to the other.
  • Figure 6 can be applied to the various setups such as those shown in Figures 1-5.
  • the difference in choosing force controlled unit 200 and force sensor mounting unit 300 for the location of force sensor 13 affects the implementation of force controller module 100 and force signal processing module 400.
  • the tool 14 is mounted close to the force sensor 13 and the desired contact force is specified in the coordinate system of the work object.
  • the control flow is as is shown in Figure 7A. Because the force sensor 13 is mounted on the robot 11, the payload gravity force will change at different robot configurations. As a result, the gravity compensation in the force signal processing module 400 is complex. As shown in Figure 7B, load identification must be performed first so that the mass and the center of gravity of the payload are known for the gravity force calculation. The gravity force is calculated at the current robot configuration from the known payload mass and center of gravity. The calculated gravity force is deducted from the force center measurement to obtain the gravity compensation. The transformation of the measured force from the force sensor coordinate system 30 to the work object coordinate system 32 is shown in Figure 7C. In this figure, the transformation from the force sensor coordinate system 30 to the work object coordinate system 32 is divided into steps.
  • Each step is represented by a curved arrow 34a to 34d in the figure, and should be either known or be easily calculated or calibrated by one of ordinary skill in the art.
  • the position and orientation of the robot face plate coordinate system 36 relative to the robot base coordinate system 38 is well known as forward kinematics and is calculated as the function of the robot joint angles, while the position and orientation of the force sensor coordinate system 30 is commonly obtained through measurement using simple tools such as measuring tape or gauges.
  • the transformation of the force measurement F meas from the force sensor coordinate system 30 to the work object coordinate system 32 follows the curved arrows 34a to 34d in a counterclockwise direction.
  • F meas is first transformed, as is shown by the arrow 34a, to the robot faceplate coordinate system 36, then, as is shown by the curved arrow 34b, to the robot base coordinate system 38, and as is shown by the curved arrow 34c to the world coordinate system 40 before being transformed, as is shown by the curved arrow 34d, to the work object coordinate system 32.
  • control flow Figure 8A is very similar to the control flow shown in Fig. 7A for the conventional setup.
  • the gravity compensation procedure as is shown in Fig. 8B, is much easier for the setup of Fig. 2 as compared to the gravity compensation procedure shown in Fig. 7B for the setup of Fig. 1 because the force sensor 13 never changes its orientation.
  • the force sensor coordinate system 30 is first transformed into the face plate coordinate system 44a of robot A 11 and then into the base coordinate system 44b of that robot. Then the transformation is to the world coordinate system 40 and from there first to the base coordinate system 46a of robot B 20 and then to the faceplate coordinate system 46b of that robot before the final transformation to the work object coordinate system 32.

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  • Engineering & Computer Science (AREA)
  • Robotics (AREA)
  • Mechanical Engineering (AREA)
  • Manipulator (AREA)

Abstract

Cette invention se rapporte à différents agencements de commande de force et de robots. Dans un agencement, le capteur de force et l'objet sont tous les deux statiques. Dans un autre agencement qui représente deux cas, l'objet et le capteur de force se situent tous les deux sur un axe extérieur, et dans un cas, l'unité commandée par force est le robot, et dans l'autre cas, elle est l'axe extérieur. Dans encore un autre agencement dans lequel l'objet se trouve sur l'axe extérieur, l'unité commandée par force est l'axe extérieur et le capteur de force se situe sur le robot. Dans un autre agencement, il y a deux robots et la force est montée sur l'un des deux tandis que l'autre est soumis à une commande de force. L'objet peut être l'outil ou l'objet à travailler ou l'objet à assembler ou utiliser dans l'assemblage d'un autre objet.
PCT/US2008/009412 2007-08-06 2008-08-05 Robots commandés par force WO2009020600A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US95409507P 2007-08-06 2007-08-06
US60/954,095 2007-08-06

Publications (1)

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WO2009020600A1 true WO2009020600A1 (fr) 2009-02-12

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015067680A3 (fr) * 2013-11-08 2015-10-01 Kuka Systems Gmbh Moyen de détection et procédé de détection
CN106625653A (zh) * 2016-05-23 2017-05-10 北京卫星环境工程研究所 基于力反馈的工业机器人辅助装配柔性对接方法
CN108262766A (zh) * 2018-01-03 2018-07-10 中科新松有限公司 一种协作机器人的检测装置
WO2019168563A1 (fr) * 2018-02-27 2019-09-06 Siemens Aktiengesellschaft Apprentissage de renforcement destiné à des tâches riches en contact dans des systèmes d'automatisation

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08141951A (ja) * 1994-11-17 1996-06-04 Kawasaki Heavy Ind Ltd ロボットの協調制御方法および協調制御装置
JPH09216185A (ja) * 1996-02-13 1997-08-19 Nippon Telegr & Teleph Corp <Ntt> ロボット制御方法及びロボットシステム
JPH106180A (ja) * 1996-06-26 1998-01-13 Toshiba Corp ワーク加工装置
US20060048364A1 (en) * 2004-09-08 2006-03-09 Hui Zhang Robotic machining with a flexible manipulator

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08141951A (ja) * 1994-11-17 1996-06-04 Kawasaki Heavy Ind Ltd ロボットの協調制御方法および協調制御装置
JPH09216185A (ja) * 1996-02-13 1997-08-19 Nippon Telegr & Teleph Corp <Ntt> ロボット制御方法及びロボットシステム
JPH106180A (ja) * 1996-06-26 1998-01-13 Toshiba Corp ワーク加工装置
US20060048364A1 (en) * 2004-09-08 2006-03-09 Hui Zhang Robotic machining with a flexible manipulator

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015067680A3 (fr) * 2013-11-08 2015-10-01 Kuka Systems Gmbh Moyen de détection et procédé de détection
US9962836B2 (en) 2013-11-08 2018-05-08 Kuka Systems Gmbh Detection device and detection method
CN106625653A (zh) * 2016-05-23 2017-05-10 北京卫星环境工程研究所 基于力反馈的工业机器人辅助装配柔性对接方法
CN108262766A (zh) * 2018-01-03 2018-07-10 中科新松有限公司 一种协作机器人的检测装置
WO2019168563A1 (fr) * 2018-02-27 2019-09-06 Siemens Aktiengesellschaft Apprentissage de renforcement destiné à des tâches riches en contact dans des systèmes d'automatisation

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