speedj_rt

This function controls the joint velocity from an external controller in real-time. It allows smooth joint motion control by continuously streaming target velocity and acceleration values through the UDP-based real-time interface.

Definition
DRFLEx.h within class CDRFLEx, public section

bool speedj_rt(float fTargetVel[NUM_JOINT],
               float fTargetAcc[NUM_JOINT],
               float fTargetTime) {
    return _speedj_rt(_rbtCtrlUDP, fTargetVel, fTargetAcc, fTargetTime);
};

Parameter

Parameter Name	Data Type	Default Value	Description
fTargetVel	float[6]		Target joint velocity [deg/s] to be commanded.
fTargetAcc	float[6]		Target joint acceleration [deg/s²]. If set to -10000, acceleration is automatically calculated based on fTargetVel.
fTargetTime	float		Duration of target command [s].

Note

• Asynchronous command.

• The motion profile is interpolated to reach (fTargetVel, fTargetAcc) over fTargetTime.

• If fTargetTime ≤ controller cycle (~1 ms), motion is executed without interpolation.

• If the next command is not received before reaching fTargetVel, the previous velocity is maintained.

• If the next command is not received for more than 0.1 s, the system triggers a timeout stop.

• If the global acceleration limit is exceeded, motion stops and an Info message is generated.

Caution

• In the current version, this function is not linked with Operation Speed [%].

• Frequent use with too short intervals may cause communication delay or jerky response.

• Ensure that fTargetTime > communication cycle for stable performance.

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;

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

float fTargetVel[6] = {0.f, 0.f, 0.f, 0.f, 0.f, 0.f};
float fTargetAcc[6] = {1000.f, 1000.f, 1000.f, 1000.f, 1000.f, 1000.f};
float fTargetTime = 0.05f; // 50 ms

float time = 0.f;
int count = 0;

while (count++ < 3000) {
    // Example: oscillate J1 between ±50 deg/s
    fTargetVel[0] = 50.f * sin(count * 0.01f);
    drfl.speedj_rt(fTargetVel, fTargetAcc, fTargetTime);
    std::this_thread::sleep_for(std::chrono::milliseconds(1));
}

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

In this example, the joint velocity is continuously commanded in a sinusoidal profile using speedj_rt at 1 ms intervals.

Tips

• Use speedj_rt for smooth and continuous velocity control of joints.

• Maintain a fixed update loop (typically 1 kHz) for deterministic motion.

• For position-based streaming, use servoj_rt instead.