servoj_rt

This function performs real-time joint position control from an external controller. It commands the robot joints to move toward the target position at each RT cycle based on the target position, velocity, acceleration, and interpolation time.

Definition
DRFLEx.h within class CDRFLEx, public section (line 600)

bool servoj_rt(float fTargetPos[NUM_JOINT],
               float fTargetVel[NUM_JOINT],
               float fTargetAcc[NUM_JOINT],
               float fTargetTime) {
    return _servoj_rt(_rbtCtrlUDP, fTargetPos, fTargetVel, fTargetAcc, fTargetTime);
};

Caution

• The current servoj_rt command is still in early implementation.
  Jerky motion may occur depending on communication latency or jitter.

• It is recommended to tune fTargetTime carefully and use a slow response speed
  or use speedj_rt instead for smoother motion control.

• When used in high-frequency loops (1 kHz), ensure that fTargetTime
  is set slightly greater than the communication cycle time.

Parameter

Parameter Name	Data Type	Default Value	Description
fTargetPos	float[6]		Target joint position [deg].
fTargetVel	float[6]		Target joint velocity [deg/s]. If set to None (-10000), velocity is automatically computed from fTargetPos.
fTargetAcc	float[6]		Target joint acceleration [deg/s²]. If set to None (-10000), acceleration is automatically computed.
fTargetTime	float		Target motion duration [s].

Note

• This command is asynchronous.

• The inner motion profile interpolates the path from current state to fTargetPos at fTargetTime using fTargetVel and fTargetAcc.

• If fTargetTime ≤ controller cycle period (~1 ms),
  the robot moves directly to the target without interpolation.

• If the next command is not received before reaching fTargetPos, the system decelerates according to the global acceleration value.

Caution

• The current version is not synchronized with the system’s operation speed [%].

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

• Recommended to set fTargetTime ≥ 20×communication_period
  or use speedj_rt for continuous position control.

Return

Value	Description
1	Success
0	Error (invalid parameter or RT communication issue)

Example

#include "DRFLEx.h"
#include <iostream>
#include <cstring>
using namespace DRAFramework;

int main() {
    CDRFLEx drfl;
    drfl.connect_rt_control("192.168.137.100", 12347);

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

    // Configure RT streaming
    drfl.set_rt_control_input(version, period, lossCount);
    drfl.set_rt_control_output(version, period, lossCount);
    drfl.start_rt_control();

    float fTargetPos[6] = {0.f, 0.f, 0.f, 0.f, 0.f, 0.f};
    float fTargetVel[6] = {0.f, 0.f, 0.f, 0.f, 0.f, 0.f};
    float fTargetAcc[6] = {0.f, 0.f, 0.f, 0.f, 0.f, 0.f};
    float fTargetTime = 0.008f;

    for (int i = 0; i < 5000; ++i) {
        // Example: oscillate Joint 1
        fTargetPos[0] = 10.f * sin(i * 0.01f);
        drfl.servoj_rt(fTargetPos, fTargetVel, fTargetAcc, fTargetTime);
        std::this_thread::sleep_for(std::chrono::milliseconds(1));
    }

    drfl.stop_rt_control();
    drfl.disconnect_rt_control();
    return 0;
}

This example demonstrates how to perform continuous joint streaming control by repeatedly sending servoj_rt commands at 1 ms intervals.

Tips

• Always run servoj_rt in a deterministic loop (1 kHz or lower).

• Use smoothed joint trajectories or low-pass filtered signals to prevent jerk.

• For Cartesian streaming, use servol_rt instead.