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
  • B25J9/1656—Programme controls characterised by programming, planning systems for manipulators
  • B25J9/1664—Programme controls characterised by programming, planning systems for manipulators characterised by motion, path, trajectory planning
• • 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
  • G05B2219/33—Director till display
  • G05B2219/33116—Configuration of motion 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
  • G05B2219/33—Director till display
  • G05B2219/33119—Servo parameters in memory, configuration of control parameters
• • 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
  • G05B2219/35398—Machining, change parameters as function of machining type

Definitions

• the present invention relates to a control system for controlling an industrial robot comprising a motion control part, wherein the motion control part is configured to operate the robot in accordance with a control program and a set of motion control pa- rameters,
• the invention also relates to a method for controlling an industrial robot, wherein the robot is operate in accordance with a control program and a set of motion control parameters.
• An industrial robot comprises a manipulator and a control system for controlling the motions of the manipulator in accordance with a control program including information on a desired path to be followed by the manipulator during execution of the program.
• the path includes positions and speed of the manipulator along the path and possibly also other requirements, e.g., user acceleration limitations.
• the control program comprises a series of program instructions written in a robot language.
• the control system comprises a program executor adapted to execute the control program and a motion control part.
• the motion control part includes a trajectory interpolator adapted to receive instructions from the control program and on basis thereof generate reference values for the motion, and a servo controller configured to generate control signals to the manipulator based on the reference values and measured values from the manipulator.
• the performance of the motion control part is determined by a plurality of motion control parameters, such as controller gain, model parameters, maximum motor torque, maximum gearbox torque, and maximum stress on the mechanical structure of the manipulator.
• An industrial robot is a general purpose machine for industrial automation.
• the requirements and operational conditions vary for different types of applications.
• the requirement on the motion control system is to follow a desired path in accordance with an accuracy specification for the specific application.
• the motion control part of the robot control system is optimized by the robot supplier with regard to a main applica- tion of the robot, or with regard to a group of applications, with possibly conflicting requirements.
• the optimization of the motion control part includes determining optimal motion control parameters.
• the result is that the per- formance of the robot is optimal for one or a few applications, but not for all types of applications.
• the optimization of the motion control parameters is hard to perform for the robot user as it requires expert knowledge of the motion control part of the robot.
• Patent application with publication number US2007/0244599 discloses an apparatus and a method for optimizing robot per- formance by means of an external computer connected to the robot control system for receiving performance data of the robot as the controller executes a path program.
• the external computer uses the performance data, user specified optimization objectives and constraints and a kinematic/dynamic simulator to generate a new set of control system parameters to replace the default set in the control system.
• the computer repeats the process until the new set of control parameters is optimized.
• the parameters are optimized according to the present robot system and the operating conditions.
• the object of the present invention is to provide a user with a possibility to easily optimize the performance of the motion control part of the robot to the present application of the robot.
• this object is achieved by a control system as defined in claim 1 .
• Such a control system comprises a data storage for storing a plurality of optional sets of motion control parameters adapted for different types of applications, and the control system is configured to receive information on a selected type of application, and the motion control part is configured to operate the robot in accordance with the set of motion control parameters belonging to the selected type of application.
• a plurality of sets of motion control parameters are optimized beforehand for a plurality of different application types.
• Each application type is provided with a set of motion control parameters optimized for the type of application.
• the ap- plication types are discrete process type, continuous high speed process type, and continuous low speed process type.
• the application types can be more specific, such as spot welding, painting, gluing, water cutting, and laser cutting.
• the sets of motion control parameters include constraints for the trajectory interpolation, such as maximum motor torque, maximum velocity, and maximum acceleration derivative.
• the sets of motion control parameters include servo control parameters, i.e., parameters in the feedback and feed forward controller, such as controller gains and model parameters.
• the sets of motion control parameters include constraints for the trajectory interpolation as well as servo control parameters. Hence, it is possible to optimize the trajectory interpolation as well as servo control of the robot.
• the sets of motion control parameters includes a default set of motion control parameters, and the control system is configured to upon request active a change of the set of motion control parameters.
• the change of set of parameters is activated upon executing a specific command in the control program.
• This embodiment makes it possible to change the set of motion control parameters on-line during exe- cution of the control program and during operation of the robot. For example, if an application has conflicting demands it is pos- sible to change the application type one or more times during the robot cycle.
• the control system comprises a configuration database including information on the type of application carried out by the robot, and the control system is configured to activate said change of set of motion control parameters by changing the type of application in the configuration database.
• This embodiment makes it possible for the user to optimize the motion control parameters for a new application by simply changing the type of application in the configuration database.
• a user interface is provided by the control system allowing the user to select the type of application.
• this object is achieved by a method for controlling the robot as defined in claim 9.
• Fig. 1 shows a control system according to an embodiment of the invention.
• Figure 1 shows a manipulator 1 and a control system for controlling the motions of the manipulator according to an embodiment of the invention.
• the control system includes a program execu- tor 2 adapted to execute control programs including information on a desired path and a motion control part 3.
• the motion con- trol part 3 includes a trajectory interpolator 5 adapted to receive instructions p from the program executor 2 and to generate reference values r for the motion, and a servo controller 6 configured to generate control signals y to the manipulator 1 based on the reference values r and measured values u from the manipulator.
• the trajectory interpolator plans how the instructed movement should be performed by carrying out an interpolation of the instructed movement.
• the interpolation includes dividing the instructed movement into a plurality of small increments, and computing joint angles for all axis of the manipulator for each increment.
• the joint angels are then converted into servo controller references r.
• the servo controller references r are transmitted to the servo controller 6.
• the manipulator is equipped with different measuring devices, e.g. angle-measuring devices to provide motor position feedback signals and accelerometers measuring the accelerations of the robot arm.
• the feedback signals u from the measuring devices are transferred to the servo controller 6.
• the servo controller 6 includes a feedback controller and possibly also a feed forward controller.
• the performance of the motion control part is, for example, determined by the algorithms used for the trajectory interpolation and for the servo control, which model structures are used by the trajectory interpolator and the servo control, which model parameters to be used by the kinematic model and the dynamic model of the robot, which constraints on the trajectory interpolation are set, and which servo control parameters are used.
• a plurality of sets of motion control parameters optimized for different types of applications is determined and stored in the robot control system, or at a place easily accessible by the robot control system.
• Each set of motion control parameters is stored together with information on the application type to which it belongs.
• the control system comprises data storage 10 for storing the sets of motion control parameters adapted for different types of applications.
• the motion control parameters determine the behavior of the motion control part and hence the performance of the robot.
• Which parameters the predefined set of motion control parameters shall include may vary between different embodiments of the invention.
• the set of motion control parameters at least shall include parameters defining constraints on the trajectory interpolation and control parameters for the servo controller.
• the sets of motion control parameters may include parameters for selecting which algorithms to be used for the trajectory interpolation and for the servo control, parameters for selecting which model structures to be used by the trajectory interpolator and the servo control, and model parameters of the kinematic model and the dynamic model of the robot.
• the motion control part is optimized for different application types. Each optimization generates a set of motion control parameters optimized for the application type.
• the result is a number of sets of motion control parameters, each set optimizing the performance of the robot for a specific application type.
• the number of application types, and hence the number of predefined sets of motion control parameters may vary for different embodiments of the invention.
• the number of selectable application types is three; a discrete process, a con- tinuous high speed process, and a continuous low speed process.
• a discrete process is, for example, material handling (pick and place applications) and spot welding.
• a discrete process usually have a high demand on cycle time, but less demand on path accuracy, which will affect the optimization of the control parameters for the discrete process.
• Examples of continuous high speed processes are gluing, painting, water jet cutting and grinding.
• the requirement of the continuous high speed processes is, for example, a path error less than 1 mm, which will affect the optimization of the control parameters for the continu- ous high speed processes.
• the main error source for the continuous high speed processes is the elasticity of the gearbox and the manipulator arm, which will also affect the optimization.
• Examples of continuous low speed processes are laser cutting and arc welding.
• the requirement of the continuous low speed processes is, for example, a path error less than 0.1 mm, which will affect the optimization of the control parameters for the continuous low speed processes.
• the main error sources for the continuous low speed processes are friction and motor ripple, which will also affect the optimization.
• the sets of motion control parameters may include a default set of motion control parameters, and the control system is then configured to upon request active a change of the set of motion control parameters.
• the motion control parameters can be changed on-line, for example, from the robot programming lan- guage, or before execution of the robot control program, for example, by changing application type in a configuration database stored in the data storage 10.
• the robot control system is provided with a user interface 12, for example a so called teach pendant unit or an external computer.
• the user interface makes it possible for the user to select on of the sets of parameters by selecting one of the application types. For example, the application types available for selection is displayed on a display screen of the user interface 12, and the user changes the set of motion control parameters by selecting one the displayed appli- cation types.
• the control system is configured to receive information on a selected type of application and store the selected application type, for example, in the configuration database.
• the motion control part is configured to operate the robot in accordance with the set of motion control parameters belonging to the selected type of application.
• the invention provides the robot user with easy-of-use, application optimized motion control parameters.
• the user does not need any detailed knowledge of the motion control part.
• the present invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims.
• the application types and the parameters may vary in different embodiments of the invention.

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• Engineering & Computer Science (AREA)
• Robotics (AREA)
• Mechanical Engineering (AREA)
• Numerical Control (AREA)

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Citations (5)

• 2008
  • 2008-05-21 CN CN2008901003611U patent/CN202011020U/zh not_active Expired - Lifetime
  • 2008-05-21 DE DE112008003870T patent/DE112008003870T5/de not_active Ceased
  • 2008-05-21 WO PCT/EP2008/056225 patent/WO2009141006A1/en active Application Filing

Patent Citations (5)

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