Assigning Inverse Kinematics

You can simulate inverse kinematics for a device by defining numeric, generic, device-specific and inverse attributes.

See also:

  1. Select Inverse Kinematics .
  2. Select a device to define inverse kinematic attributes. The Inverse Kinematic Attributes dialog box for the selected device is shown: The Basic tab page (shown above) allows you to select and modify the essential attributes of a device to which inverse kinematics are applied. The Basic attributes are defined as follows:
    Mount Part Mounting plate for the device - indicated by LMB (Left Mouse Button) selection of mouse.
    Mount Offset TCP position indicated by selecting a Frame of Interest on the Mount Part. This is optional and origin of Mount Part is assumed if FOI is not specified.
    Reference Part The Part in the Kinematic chain from which the solver computes the DOF values. Indicate with LMB for selection.
    Base Part Base Part of the device - indicate with LMB for selection.
    Singularity Tolerance Angular tolerance value (float).
    Approach Axis X, Y or Z approach axes
    Approach Direction In / Out - the Approach Direction
    Solver Type A list box allowing you to switch between solvers for the device. The contents of the Solver Attributes tab depend on this selection. Available solvers are:
    • Numeric Inverse
    • Generic Inverse
    • Device Specific Inverse
    • User Inverse
    Kinematic Routine Name This is a non-editable string based on the selected solver type.
    Kinematic Class Contains the kinematic classes per the currently selected solver. This attribute is not applicable for the Numeric Solver.
    Note: In some cases, the Inverse Kinematics function cannot solve for the device automatically and an error message is displayed. When this occurs, click OK to close the Error dialog box, then click Advanced to manually configure the Inverse Kinematics.
    Note: Inverse Kinematics for robots imported from the Robot Library (whether from V5 or 3DEXPERIENCE) can not be edited. Please contact Support for modifications to these robots.
  3. Click Advanced to access the other tab pages, and select the Configurations tab. This page allows you to alter the name and set the validity of the postures available to the device. The Configurations attributes are defined as follows:
    Configuration Name The name of the configuration.
    Validity Determines whether the configuration is proper. Possible values are Valid and Invalid.
  4. Select the Actuator Space Map tab. This page describes the joint behavior of the device:

    The Actuator Space Map attributes are defined as follows:

    Joint Map The DOF expression governing the joint.
    Joints Type The type of joint motion: Translational or Rotational.
    Kinematics Axis Type The axis and direction of motion of the joint: TransX, TransY, Transz, RotX, RotY and RotZ along both positive and negative directions.
    Kinematics DOF Number The numerical DOF value attached to the joint in the kinematic chain.
    Kinematics Part The link (or part) which builds up the joint in the kinematics chain.
    Compute

    When clicked, an automatic computation of the Actuator Space Map parameters is launched, if possible. This computation will attempt to identify the elements of the 2nd to 5th columns. However, note that it will not modify the 1st column. This is because, in case of robots with dependency relations in the primary chain, the DOF expression governing the joint for inverse kinematics can only by typed in by a user, they cannot be synthesized from the model.

  5. Select the Solver Attributes tab. This page consists of fields that are dependent on the Solver Type selected on the Basic tab page.

    Numeric Inverse

    If Numeric Inverse is selected, the tab page consists of attributes related to a numeric solver, such as convergence tolerances, solvable joints in the mechanism, and constraints for the TCP Convergence:

    Attributes for Numeric Inverse Kinematics are defined as follows:

    Convergence Tolerances - Linear and Angular The allowed TCP Convergence tolerance during inverse kinematics simulation.
    Solve Joints This frame consists of available joints. Each joint can be selected to be solved (or otherwise) for inverse kinematics.
    TCP Convergence Controls TCP convergence in the directions X, Y, Z, R, P, and Y.

    Generic Inverse

    If Generic Inverse is selected, the Generic Inverse attributes are displayed. This information is related to joints, mount and base offsets, link lengths and wrist rotation. Attributes for Generic Inverse Kinematics are defined as follows:

    Zero Offsets Joint offset from joint zero position.
    Presents Indicates whether the kinematics solution for this joint is to be used for the device or not. Present (use), Absent-Fixed (not to be used) and Absent-Free (ignore).
    Signs The joint direction signs for motion.
    Order The joint order.
    Link Lengths Defines joint length and offset.
    Base Offset Offset for base part.
    Mount Offset Offset for mount part.
    Wrist Rotation (Yaw, Pitch, Roll) Wrist rotation values to be set to rotate the default Device wrist to align with current Device.

    Device Specific Inverse

    If Device Specific Inverse is selected, the Device Specific Inverse attributes are displayed.

    Multiple instances of a given robot can share the same inverse kinematics scheme of one particular robot whose inverse kinematics parameters are already defined (instead of calculating the inverse kinematics parameters individually for each robot). When this solver type is selected, the Device Routine Name indicates the device whose inverse kinematics parameters are to be shared.

    Attributes for Device Specific Inverse Kinematics are defined as follows:

    Link Parameters Defines length and offset for each link.
    Auxiliary Data Additional Inverse Kinematics algorithm specific parameters.
    Device Routine Name Specifies the device whose inverse kinematics parameters are to be shared.

    Device Specific Inverse

    If this button is pressed, it launches a kinematic structure analysis engine that tries to automatically compute of the attributes for the Generic solver. The analysis includes the identification of the Kinematic Class based on the 8 supported type definitions within Generic (see "About Generic Inverse Kinematics" for details). If the kinematic structure of the robot does not fall into the Generic class definitions, this button will issue the following Warning message:

    "Unsupported Arm Type. Computation of the Generic Inverse Kinematic parameters for the given Robot failed"

    Caveat: Of the 8 Generic classes, the BLOCK and PENDULUM classes are special in that they are not supported for automatic computation, and will result in the Warning message above. This is because these 2 classes are non-industrial and are included in the solver mainly for completeness in case of research type of applications, and the analysis engine is not able to identify them from the kinematic structure. If the user models a BLOCK or PENDULUM type robot, the Generic algorithm will only be able to solve for it if the user enters the above attributes by hand.

    User Inverse

    Currently not supported.

    Note: Inverse kinematics is a specification of the assembly: the assembly can be reused in many different contexts, with the same inverse kinematics specification. Thus, the Inverse Kinematics dialog box can only be edited when the assembly data is open in its own window. The Inverse Kinematics dialog box may open in other contexts, but cannot be changed without the assembly also being open.