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
  • B25J9/1694—Programme controls characterised by use of sensors other than normal servo-feedback from position, speed or acceleration sensors, perception control, multi-sensor controlled systems, sensor fusion
  • B25J9/1697—Vision controlled systems
• • 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
  • B25J9/1674—Programme controls characterised by safety, monitoring, diagnostic
  • B25J9/1676—Avoiding collision or forbidden zones
• • 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
  • G05B2219/40053—Pick 3-D object from pile of objects
• • 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
  • G05B2219/40478—Graphic display of work area of robot, forbidden, permitted zone

Definitions

• the present invention relates to a method and an arrangement for a robot and gripper for picking up components with a guided robot
• robots are nowadays guided automatically by various forms of sensor system, such as camera or laser sensors.
• the technology is primarily used in materials handling to replace manual assembly line production. Its function is to guide the robot in order to grip components having an unknown orientation.
• the pick-up arena there are multiple components present in the area within which the robot must pick up the component, hereinafter referred to as the pick-up arena.
• Problems often arise with the robot gripper and/or the robot itself colliding with adjacent components.
• Current solutions are aimed at preventing the components getting close to one another in the arrangement that supplies the pick-up arena with components.
• One way of doing this is to mechanically arrange the components on a conveyor belt, for example, in order to prevent them lying against or too close to one another. This is not particularly reliable, however.
• the object of the present invention is to demonstrate a means in the form of a method and arrangement for picking up components with a guided robot.
• the present invention also affords the advantage that when picking up components the robot with associated gripper does not collide with adjacent components.
• the present invention furthermore affords the advantage that the pick-up arena can be supplied with components with a simpler prior separation or without the use of any prior sorting or separation.
• the present invention provides for improved pick-up of components by means of a guided robot and having the characterising features specified in claim 1.
• the arrangement according to the present invention comprises a sensor system, such as a camera system (vision system), for example, an optical 3D measuring system or laser equipment, which creates an image or a multi-dimensional range of the pick-up arena.
• a sensor system such as a camera system (vision system), for example, an optical 3D measuring system or laser equipment, which creates an image or a multi-dimensional range of the pick-up arena.
• the components and their orientation are identified in the sensor system.
• the information obtained on the orientation is used to guide the robot to grip the component.
• the sensor system defines the gripper and or robot and the area for the pick-up arena.
• the result from this or another sensor system is then used to prevent the robot or the gripper colliding with adjacent components or with the surroundings.
• Prohibited areas for the aforementioned gripper and the robot are monitored in order to prevent any collision occurring in operation before the components has been collected or gripped by the robot.
• This is done by programming into the sensor system the components that are to be searched for and where on the component it is to be gripped.
• the so-called programming is done by defining the component in one or a number of different ways, for example by selecting an area on an image of the component where sensing is to be performed using some form of pattern recognition, or by defining blob parameters for the component.
• blob parameters refers, for example, to the area, circumference, maximum length, minimum length, and compactness (area per circumference) of a defined area.
• the system searches for the programmed component, which is most commonly done with some form of image processing.
• Fig. 1 shows the programming of a component with the gripping position drawn in.
• the centre of the gripping position is in the thin circle 1 with a rotational orientation according to the thin vertical section 2.
• the system searches for components resembling the component 4.
• the rectangles 3 describe the gripper fingers.
• Fig. 2 shows parts from an example of a graphic interface for programming in the appearance and location of the gripper in relation to the gripper reference position, TCP.
• the designation A describes the distance between TCP and the gripper fingers 3.
• the designations B and C describe the size of the gripper fingers 3.
• Fig. 3 shows an image from programming in components, where thresholding is used to define the component within the pick-up area. In this example this method works well for the three smaller components 6 but on the large component 5 significant parts 7 are missing, see Fig. 4.
• Fig. 4a shows a component 5, which is to be programmed in.
• Fig. 4b shows two components 5, 6, where parts of the larger component 5 (cf. Fig. 4a) have been rendered invisible by thresholding, for example due to background or light setting.
• Fig. 4c shows two components 5, 6 where during programming parts of the component 5 are rendered visible by manually defining the lighter grey area 7 in relation to the position of the component 5, thereby creating the required definition of the entire component 5.
• Fig. 4d shows two components which are correctly defined within the pick-up arena.
• Fig. 5 shows three components 9, 10, 11 which cannot be picked up due to collision and a component 8 which can be picked up.
• the first component 9 has been picked up, it becomes possible to pick up a least one further component 10 (to the right of the figure).
• the arrangement according to the present invention comprises a sensor system, such as a camera system (vision system), for example, an optical 3D measuring system or laser equipment, which creates an image or multi-dimensional range of the pick-up arena.
• a sensor system such as a camera system (vision system), for example, an optical 3D measuring system or laser equipment, which creates an image or multi-dimensional range of the pick-up arena.
• the components and their orientation are defined in the sensor system.
• the information obtained on the orientation is used to guide the robot to grip the component.
• the sensor system defines the gripper, the robot and the area of the pick-up arena prior to operation.
• gripper or gripping fingers relate to all forms of tool for carrying the component with it, such as a pair of fingers that grip around the component, three fingers that grip around a cylinder or in an aperture such as a lathe chuck, suction cup or suction cups, magnet or magnets and so forth. All these parts are not necessarily defined prior to operation, very often only the gripping fingers being defined.
• Grippers may be defined, for example, simply by determining whether the TCP of the components are situated closer together than a certain number of millimetres, in which case the components must not be picked up.
• the term robot relates, for example, to simpler moving systems comprising a few linear units which can be brought to a specific position, four-axis pick-up robots, six-axis industrial robots etc.
• the robots may be floor, wall or ceiling-mounted.
• the result from the sensor system is then used in order to prevent the robot or the gripper colliding with adjacent components or with the surroundings.
• the gripper, the robot and prohibited areas are normally defined in 2 or 3 dimensions, that is to say in two dimensions represented as the plane or in three dimensions represented as the space.
• the surroundings, the gripper and the robot are defined either together or individually in relation to the centre of the gripper (see the example of a gripping finger definition in Fig.2).
• the definition may be done manually, for example, through a graphical interface or from a virtual model which is imported into the system or by inputting with the sensor system.
• Prohibited areas for the aforementioned gripper or the robot are monitored in order to prevent any collision occurring in operation before the component has been collected or gripped by the robot.
• a collision occurs if the gripper or the robot encroaches on areas in which there are components or on prohibited adjacent areas. If the result of monitoring shows that collision will occur, the component is not picked up.
• the components are only monitored to ensure that their centres do not lie too close to one another, there being no need in this case to define gripping fingers and grippers. If one component is situated too close to another, it will not be picked up. Components are not picked up if the distance between them is less then a certain predetermined measurement.
• the components that are not picked up for the aforementioned reason may sometimes be picked up later once the adjacent components that could be picked up have been picked up or the components have been reoriented by the arrangement which supplies the pick-up arena with components. This can be achieved by transporting the components via an W 20
• Fig. I- The so-called programming is done by defining the component in one or a number of different ways, for example by selecting an area on an image of the component where sensing is to be performed using some form of pattern recognition, or by defining blob parameters for the component.
• thresholding is used to mean the creation of a digital image.
• the technique for thresholding the image is used to create an image in which the components are white and the surroundings black, or vice versa.
• the arrangement does not depend on any particular method of thresholding, it being possible to use a single fixed threshold value or more sophisticated solutions with automatic adjustment of the threshold value in proportion to variations between images over time, with a threshold value varying over the image and adapted to local variations in light setting or different variants for colour-coding of component and background etc.
• the defining of prohibited areas is done by programming in relation to the programmed gripping positions.
• the system searches for multiple components in the sensor result and prohibited areas are marked in relation to the search results obtained, see Fig.4.
• This method is used, for example, when parts of the component cannot be reliably distinguished from the surroundings by thresholding.
• There are many different methods of searching for the component which can in principle all be used for this arrangement for collision protection.
• the method and arrangement according to the present invention afford the facility for undertaking said control of robot and gripper in operation and for supplementing the virtual world with components having an unknown position.
• the unknown position can be handled by the sensor system, which among other things programs in the components and reads off the pickup arena so that the robot is allowed to pick up components without the risk of collision with the immediate surroundings.
• the steps involved in the method using the arrangement for the robot and gripper when picking up components with a guided robot with associated sensor system can be performed in any feasible order.

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

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Publications (1)

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• 2002
  • 2002-12-10 SE SE0203655A patent/SE524796C2/sv not_active IP Right Cessation
• 2003
  • 2003-12-10 AU AU2003302921A patent/AU2003302921A1/en not_active Abandoned
  • 2003-12-10 WO PCT/SE2003/001933 patent/WO2004052596A1/en not_active Application Discontinuation
  • 2003-12-10 EP EP03812746A patent/EP1569776A1/de not_active Ceased

Non-Patent Citations (1)

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