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For information on the latest version, please have a look at 1.33.5.

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
DRFLEx.h within class CDRFLEx, public section

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 speedl_rt for smoother motion.

• fTargetTime is not the send interval. See the second Caution section below for how to choose it.

Parameter

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] If set to -10000, velocity is automatically calculated from fTargetPos
fTargetAcc	float[6]		Target TCP acceleration [mm/s², deg/s²] 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
  (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 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 set_rt_control_input, or the input watchdog ends the session while servol_rt keeps returning 1.

• For continuous position control, consider speedl_rt.

• Not compatible with force/compliance control or DR_VAR_VEL near singularities;
  the system automatically reverts to DR_AVOID mode in such cases.

Return

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 set_on_log_alarm. set_on_rt_log_alarm reports only RT session messages, so register both callbacks.

Example

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 servoj_rt.