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

• The current servol_rt command is preliminary, and jerky motion may occur depending on communication latency or network jitter.

• 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 TCP position and orientation [x, y, z, Rx, Ry, Rz] (position in mm, rotation in deg, using Euler ZYX 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.

• If fTargetTime ≤ controller’s cycle (~1 ms), interpolation is skipped.

• If the next command is not received before completion, the motion decelerates
  using the system’s global acceleration setting.

Caution

• The current implementation is not linked with Operation Speed [%].

• Jerky motion may occur if the command interval exceeds 1 ms.

• 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: 0.001 s on DRCF v2, and 0.025 s on DRCF v3, to which v3 adds a further 0.005 s. A value below the minimum is silently replaced, so a value tuned on one controller generation must be re-checked on the other.

• 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 datagram was sent.
0	The command datagram could not be sent.

Note

This function is asynchronous. It returns as soon as the datagram is sent and does not wait 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 faults are reported through set_on_rt_log_alarm.

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 ≥ 20 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.