KUKA

Cartesian trajectories for the KUKA robots (KRC/KRL).

Vendor specifics

Teach pendant	“KCP” (KUKA Control Panel) or smartPAD
Programming / simulation software	OrangeEdit editor / KUKA simulator Sim Pro
Software	KUKA System Software (KSS)
User interface	KUKA smartHMI (smart Human-Machine Interface)
Programming language	KRL (KUKA Robot Language)
Relevant hardware	KR C2 / KR C3 / KR C4 and probably others

Further reading

• manual_collection
• manual_slides
• manual_advanced

Trajectory composition

Cartesian trajectories can be composed in three ways (see manual_slides p. 23-32).:

• Linear Cartesian motions

  LIN

  [LIN]
  $VEL.CP = 0.5
  PTP Start point
  LIN End point
  

• Circular motions

  CIRC

  [CIRC]
  $VEL.CP = 0.5
  PTP Start point
  CIRC Auxiliary point , Endpoint, CA Angle
  

• Joint space interpolation

  PTP

  • joint space movement to a given goal, which can be specified in joint space or in Cartesian space.

  • controller calculates the necessary angle differences for each axis

  • Preferred motion if a high TCP speed is wanted and the interpolation between both waypoints doesn’t have to follow a predefined path.

    [PTP]
    $VEL.CP = 0.5
    PTP Start point
    PTP Auxiliary point C_PTP
    PTP End point
    

• Additional

  SLIN

  • The Spline Linear motion uses splines between linear motions

  SCIRC

  • The Spline Circular motion uses splines between circular motions

  SPTP

  • The Spline Point to Point motion is similar to PTP but it allows continuous spline motions.

Waypoint representation

(see kuka_system_software and manual_slides)

• Linear

  [LIN]
  X 1000.00
  Y 0.00
  Z 1000.00
  A 90.00
  B 0.00
  C 90.00
  

• Circular

  [CIRC]
  P1[]
    X 1000.00
    Y 1.00
    Z 1000.00
    A 90.00
    B 0.00
    C 90.00
  P2[]
    X 1000.00
    Y -1.00
    Z 1000.00
    A 90.00
    B 0.00
    C 90.00
  CA 180
  

• Point 2 Point

  [PTP]
  POS []
    X 1000.00
    Y 0.00
    Z 1000.00
    A 90.00
    B 0.00
    C 90.00
    S 6
    T 50
  

  [PTP]
  AXIS []
    A1 0
    A2 -90
    A3 90
    A4 90
    A5 0
    A6 -180
  

• Spline

  [SPLINE]
  SPL
    X 102
    Y 1
  SPL
    X 104
    Y 0
  SPL
    X 204
    Y 0
  

• Angles of rotation of the robot coordinate systems
• S and T specify a robot’s position unambiguously if more than one axis position is possible for the same point in space (because of kinematic singularities). This is often written in integer form, thus the values above.
  • S (status): 3-bit binary value describing the robot’s configuration with predefined criteria
  • T (turn): direction of a turn. 6-bit binary value, containing flip bits for each axis (0 when axis >= 0 deg, 1 when axis < 0 deg)

Angle	rotation axis
A	Z
B	Y
C	X

Trajectory parameterization and execution

(see manual_advanced)

Specification of velocity

• Speed of TCP can be set within a move instructions in % by the ‘vel’ argument.

• For Continuous path motions ([LIN], [CIRC]) the velocity is constant from start to end.

• Realtive Joint Velocity can be set by: setJointVelocityRel(0.3)

• KUKA operation mode influence velocity

  Mode	description	velocity
  T1	Manual Reduced Velocity	max of 250mm/s
  T2	Manual High Velocity	as programmed
  AUT	Automatic	as programmed
  EXT	Automatic external	as programmed
  CPR	Safe Operation	max of 250mm/s

specification of acceleration

Relative Joint Acceleration can be set by: setJointAccelerationRel(0.5)

Blending

(source Angerer and Vistein)

• Blending is enabled by the advance run mechanism enabling planning the next motion while executing a motion.

• To activate blending a motion needs to be marked as blendable by adding a keyword to the motion instruction. C PTP`for PTP motions and `C_DIS, C_VEL or C_ORI for motions in operation space.

• Blending between all motion types is supported. It is even possible to blend a PTP (joint space) into a LIN (Cartesian space) and vice versa.

• Blending can be done by defining a blend radius

  • as a relative value: IMotion.setBlendingRel(0.2)
  • in millimeters: IMotion.setBlendingCart(20)

Parallel IO operations

No information found so far

Online (real-time) trajectory modifications

Robot Sensor Interface (RSI) (see RobotSensorInterface)

• supported since KRC-4 controller
• influence the position of the robot by external sensors.
• robot position can be influenced by external sensors through overlaying a programmed motion with external control, like position correction from a sensor-based system
• default 4 ms cycle time for accepting set point, hence external controller requires hard real-time
• usually correction data is provided in relative values and applied directly to the running program. However, as absolute values are possible, the robot can be controlled externally while a KRL program only providing a fixed start position runs in the background.
• communication between KUKA and external controller via UDP/IP on a dedicated network segment
• RSI context is a library with RSI objects for configuration of the signal flow
• RSI monitor offers online a visualization of the RSI signals.