.. _servol_rt:

servol_rt
------------------------------------------
This function performs **real-time task-space (TCP) position control** from an external controller.  
It commands the robot’s tool center point (TCP) position and orientation at each real-time control cycle,  
based on the target pose, velocity, acceleration, and interpolation time.

**Definition** |br|
``DRFLEx.h`` within class `CDRFLEx`, public section

.. code-block:: cpp

   bool servol_rt(float fTargetPos[NUM_TASK],
                  float fTargetVel[NUM_TASK],
                  float fTargetAcc[NUM_TASK],
                  float fTargetTime) {
       return _servol_rt(_rbtCtrlUDP, fTargetPos, fTargetVel, fTargetAcc, fTargetTime);
   };

**Caution**

- Communication latency or network jitter produces jerky ``servol_rt`` motion.  
- It is recommended to **tune the target time (fTargetTime)** and use a **slow response speed**,
  or alternatively use :ref:`speedl_rt <speedl_rt>` for smoother motion.  
- ``fTargetTime`` is not the send interval. See the second **Caution** section below for how to choose it.

**Parameter**

.. list-table::
   :widths: 25 20 20 35
   :header-rows: 1

   * - **Parameter Name**
     - **Data Type**
     - **Default Value**
     - **Description**
   * - fTargetPos
     - float[6]
     - -
     - Target pose [X, Y, Z, A, B, C] in mm and deg; the orientation uses the Euler ZYZ convention.
   * - fTargetVel
     - float[6]
     - -
     - Target TCP velocity [mm/s, deg/s] |br|
       If set to **-10000**, velocity is automatically calculated from ``fTargetPos``
   * - fTargetAcc
     - float[6]
     - -
     - Target TCP acceleration [mm/s², deg/s²] |br|
       If set to **-10000**, acceleration is automatically computed
   * - fTargetTime
     - float
     - -
     - Target interpolation duration [s]

**Note**

- **Asynchronous command.**  
- The internal motion profile interpolates between current and target states |br| 
  *(fTargetPos, fTargetVel, fTargetAcc)* over ``fTargetTime``.  
- On releases with the 0.001 s minimum, if ``fTargetTime`` ≤ controller’s cycle (~1 ms), interpolation is skipped.  
- If the next command is not received before completion, the robot decelerates to a stop with the task acceleration set by :ref:`set_accx_rt <set_accx_rt>`.

**Caution**

- The current implementation is **not linked** with Operation Speed [%].  
- ``fTargetTime`` is the time the controller is given to reach the target, and it is **not** the interval at which commands are sent. Set it comfortably larger than the send interval so consecutive commands overlap.
- The controller enforces a **minimum** ``fTargetTime`` and raises smaller values to it. Minimum fTargetTime: 0.001 s on DRCF v2.12.x and v3.3.x. On DRCF v3.4.0 or later, values below 0.025 s are raised to 0.025 s, and each command then takes fTargetTime + 0.005 s. A value below the minimum is silently replaced, so a value tuned on one controller release must be re-checked on another.
- The send interval must match the period declared to :ref:`set_rt_control_input <set_rt_control_input>`, or the input watchdog ends the session while ``servol_rt`` keeps returning 1.
- For continuous position control, consider :ref:`speedl_rt <speedl_rt>`.  
- Not compatible with **force/compliance control** or **DR_VAR_VEL** near singularities;  |br|
  the system automatically reverts to **DR_AVOID** mode in such cases.

**Return**

.. list-table::
   :widths: 20 80
   :header-rows: 1

   * - **Value**
     - **Description**
   * - 1
     - The command was sent. This does not confirm that the controller received or applied it.
   * - 0
     - The command datagram could not be sent.

.. note::

   This function is asynchronous. It returns without waiting for the controller to accept or reject the command, so a return value of 1 does not confirm that the robot acted on it. Rejected commands and motion warnings and errors are reported through :ref:`set_on_log_alarm <set_on_log_alarm>`. :ref:`set_on_rt_log_alarm <set_on_rt_log_alarm>` reports only RT session messages, so register both callbacks.

**Example**

.. code-block:: cpp

   drfl.connect_rt_control("192.168.137.100", 12347);

   std::string version = "v1.0";
   float period = 0.001f; // 1 ms
   int lossCount = 4;

   // Configure real-time streaming
   drfl.set_rt_control_input(version, period, lossCount);
   drfl.set_rt_control_output(version, period, lossCount);
   drfl.start_rt_control();

   // Define target TCP pose
   float fTargetPos[6] = {150.f, 0.f, 100.f, 0.f, 0.f, 0.f};
   float fTargetVel[6] = {200.f, 100.f, 100.f, 20.f, 20.f, 20.f};
   float fTargetAcc[6] = {1000.f, 800.f, 800.f, 100.f, 100.f, 100.f};
   float fTargetTime = 0.06f; // 60 ms (recommended >= 30 ms)

   // Send real-time task-space motion command
   if (drfl.servol_rt(fTargetPos, fTargetVel, fTargetAcc, fTargetTime))
       printf("Task-space motion command successful.\n");
   else
       printf("Task-space motion failed.\n");

   drfl.stop_rt_control();
   drfl.disconnect_rt_control();

This example shows how to control TCP motion in real time  
by sending continuous task-space commands at 1 ms intervals.

**Tips**

- Use ``servol_rt`` for **precise Cartesian interpolation control** in external systems.  
- Always ensure consistent timing between cycles for smooth motion.  
- For joint-level streaming, refer to :ref:`servoj_rt <servoj_rt>`.