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Get the robot position

Read the joint positions and the TCP position of a UR cobot in C# or Python, with RTDE up to 500 Hz or with the Primary Interface.

Which way to choose
Units
Prerequisites
Example
Troubleshooting
What to read next

This article shows how to read the current position of a Universal Robots cobot from a PC, in C# or Python: the 6 joint positions and the position of the tool center point (TCP). It compares the interfaces that give it and shows a complete program.

Which way to choose

Way	Frequency	Joint positions	TCP position	When
RTDE	Up to 500 Hz	`ActualQ`	`ActualTcpPose`	Fast monitoring, logging, closed loop
Primary Interface	10 Hz	`JointData.Base.Position`...	`CartesianInfo.AsPose()`	Display, no setup, enabled by default
Forward kinematics	No robot	Your values	`KinematicsUtils.ForwardKinematics`	Offline computation, simulation

RTDE also gives the target positions (TargetQ, TargetTcpPose), the speeds and the forces. The Primary Interface also gives the TCP offset of the active tool (CartesianInfo.TCPOffsetX...).

Units

Value	Unit
Joint positions	rad
X, Y, Z of the TCP	m, in the base frame of the robot
RX, RY, RZ of the TCP	rad, a rotation vector, as in URScript and PolyScope

To get roll, pitch and yaw, call FromRotationVectorToRPY(). See Convert position types.

Prerequisites

RTDE: the service RTDE is enabled on the robot. The Primary Interface: the service Primary Client Interface. See Prepare the robot.
No remote control is needed to read data.

Example

The program connects with RTDE at 125 Hz and the Primary Interface, and prints the positions given by both.

using UnderAutomation.UniversalRobots;
using UnderAutomation.UniversalRobots.Common;
using UnderAutomation.UniversalRobots.Rtde;

class HowToGetPosition
{
  static void Main(string[] args)
  {
    
    var robot = new UR();

    var parameters = new ConnectParameters("192.168.0.1");

    // RTDE: joint and tool positions, 125 times per second
    parameters.Rtde.Enable = true;
    parameters.Rtde.Frequency = 125;
    parameters.Rtde.OutputSetup.Add(RtdeOutputData.ActualQ);
    parameters.Rtde.OutputSetup.Add(RtdeOutputData.ActualTcpPose);

    // The Primary Interface is enabled by default: 10 packages per second
    robot.Connect(parameters);

    // Wait for the first packages
    Thread.Sleep(500);

    // 1. RTDE. Joint positions in rad, tool center point in m and rad
    JointsDoubleValues q = robot.Rtde.OutputDataValues.ActualQ;
    Pose tcp = robot.Rtde.OutputDataValues.ActualTcpPose;
    Console.WriteLine($"RTDE joints: {q.Base:F4} {q.Shoulder:F4} {q.Elbow:F4} {q.Wrist1:F4} {q.Wrist2:F4} {q.Wrist3:F4}");
    Console.WriteLine($"RTDE TCP: X={tcp.X:F4} Y={tcp.Y:F4} Z={tcp.Z:F4} RX={tcp.Rx:F4} RY={tcp.Ry:F4} RZ={tcp.Rz:F4}");

    // 2. Primary Interface. Same values, less often
    Pose tcp10Hz = robot.PrimaryInterface.CartesianInfo.AsPose();
    double shoulder = robot.PrimaryInterface.JointData.Shoulder.Position;
    Console.WriteLine($"Primary Interface TCP: X={tcp10Hz.X:F4} Y={tcp10Hz.Y:F4} Z={tcp10Hz.Z:F4}");

    // The orientation as roll, pitch, yaw, in degrees
    Pose rpy = tcp.FromRotationVectorToRPY();
    Console.WriteLine($"Roll={rpy.RxDegrees:F2} Pitch={rpy.RyDegrees:F2} Yaw={rpy.RzDegrees:F2}");

    robot.Disconnect();
    
  }
}

To follow the position continuously, use the event OutputDataReceived of RTDE: see Receive data.

Troubleshooting

The values are 0 or null: no package is received yet. Wait about 100 ms after the connection.
ConnectException on RTDE: the service RTDE is disabled, or port 30004 is blocked.
The pose differs from PolyScope: PolyScope shows the TCP of the active tool, in the base frame or in a feature. The SDK gives the TCP in the base frame.

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