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github_url:https://github.com/UniversalRobots/Universal_Robots_Client_Library/blob/master/doc/architecture/script_command_interface.rst

Script Command Interface

The ScriptCommandInterface allows using functionality of the robot that would normally interrupt program execution. For this purpose a subset of the robot's functionality is made available in specific API calls.

At the time of writing the ScriptCommandInterface provides the following functions:

  • zeroFTSensor(): Zeros the force/torque sensor.
  • setPayload(): Set the active payload mass and center of gravity.
  • setToolVoltage(): Set the voltage of the tool output.
  • startForceMode() / endForceMode(): Start and end a force mode. See the force mode example for more information.
  • startToolContact() / endToolContact(): Start and end a tool contact mode. See the tool contact example for more information.
  • setFrictionCompensation(): Set friction compensation for torque command.
  • ftRtdeInputEnable(): Enable/disable FT RTDE input processing.
  • setGravity(): Set the gravity vector for the robot.
  • setTcpOffset(): Set the TCP offset of the robot.
  • setFrictionScales(): Set viscous and Coulomb friction scale factors for direct torque control.
  • setTargetPayload(): Set the active payload mass, center of gravity, inertia matrix and transition time.

Communication protocol

The ScriptCommandInterface communication is part of the protocol implemented in the external_control.urscript.

Data sent to the robot

The robot reads from the "script_command_socket" expecting a 32 bit integer representation of up to 28 datafields.

script_command_socket to_robot message format
index meaning
0
script command functionality. Can be either of
  • 0: zeroFTSensor
  • 1: setPayload
  • 2: setToolVoltage
  • 3: startForceMode
  • 4: endForceMode
  • 5: startToolContact
  • 6: endToolContact
  • 7: setFrictionCompensation
  • 8: ftRtdeInputEnable
  • 9: setGravity
  • 10: setTcpOffset
  • 11: setFrictionScales
  • 12: setTargetPayload
1-27 data fields specific to the command
With zeroFTSensor command
index meaning
1-27 No specific meaning / values ignored
With setPayload command
index meaning
1 Payload mass in kg (floating point)
2-4 Payload center of gravity in m, displacement from the tool mount (floating point)
With setToolVoltage command
index meaning
1 Voltage in V (Has to be 0, 12 or 24)
With startForceMode command
index meaning
1-6 task frame (floating point, see script manual for details)
7-12 selection vector (floating point, see script manual for details)
13-18 wrench (floating point, see script manual for details)
19 force_type(one of 1, 2 and 3, see script manual for details)
20-25 limits (floating point, see script manual for details)
26 damping_factor (floating point, see script manual for details)
27 gain_scaling (not on CB3 robots) (floating point, see script manual for details)
With endForceMode command
index meaning
1 No specific meaning / values ignored
With startToolContact command
index meaning
1 No specific meaning / values ignored
With endToolContact command
index meaning
1 No specific meaning / values ignored
With setFrictionCompensation command (Deprecated, use setFrictionScales instead)
index meaning
1 friction_compensation_enabled enable/disable friction compensation for torque command.
With ftRtdeInputEnable command. See script manual for details.
index meaning
1 ft_rtde_input_enabled enable/disable FT RTDE input processing.
2 sensor_mass in kg (floating point)
3-5 sensor_mesurement_offset in m, displacement from the tool flange (3d floating point)
6-9 sensor_cog in m, displacement from the tool flange (3d floating point)
With setGravity command
index meaning
1-3 The gravity vector (towards the Earth's center), represented in robot's base frame (floating point)
With setTcpOffset command
index meaning
1-6 TCP offset as [x, y, z, rx, ry, rz] given in the flange coordinate system in SI units (meters and radians, floating point)
With setFrictionScales command
index meaning
1-6 Viscous friction scale factors. One number per joint, range [0-1]. 0 means no compensation for that joint. 1 means full compensation. Default is [0.9, 0.9, 0.8, 0.9, 0.9, 0.9]. (floating point)
7-12 Coulomb friction scale factors. One number per joint, range [0-1]. 0 means no compensation for that joint. 1 means full compensation. Default is [0.8, 0.8, 0.7, 0.8, 0.8, 0.8]. (floating point)
With setTargetPayload command
index meaning
1 Payload mass in kg (floating point)
2-4 Payload center of gravity in m, displacement from the tool mount (floating point)
5-10 Payload inertia matrix [Ixx, Iyy, Izz, Ixy, Ixz, Iyz] in kg·m² (floating point)
11 Payload transition time in seconds (floating point)

Note

In URScript the socket_read_binary_integer() function is used to read the data from the script command socket. The first index in that function's return value is the number of integers read, so the actual data starts at index 1. The first data entry is always the command type, hence the indices in the table above are shifted by one when accessing the result array of the URScript function. E.g. reading the boolean value for friction compensation in the setFrictionCompensation command would be done by accessing index 2 of the result array.

All floating point data is encoded into an integer representation and has to be divided by either the MULT_JOINTSTATE or MULT_TIME constant to get the actual floating point value. These constants are defined in the ReverseInterface class.

Data sent from the robot

Data is being sent from the robot to the ScriptCommandInterface only when tool contact is used. It will send either UNTIL_TOOL_CONTACT_RESULT_SUCCESS when tool contact has been established while tool contact was active or UNTIL_TOOL_CONTACT_RESULT_CANCELED if tool contact mode was ended without establishing physical contact.