alter_motion

This function applies an incremental adjustment to the active motion trajectory after enable_alter_motion has been successfully activated. It allows fine control of the robot’s end-effector position and orientation in real time by sending small delta pose values at each control cycle.

Each call to alter_motion() modifies the current trajectory based on the provided fTargetPos offsets. The input values correspond to X, Y, Z, Rx, Ry, Rz displacements and rotations, which are interpreted according to the reference frame configured in enable_alter_motion().

This function is available in M2.4 version or higher.

Definition
DRFLEx.h within class CDRFLEx, public section (line 982)

bool alter_motion(float fTargetPos[NUM_TASK]) {
    return _alter_motion(_rbtCtrl, fTargetPos);
};

Parameter

Parameter Name	Data Type	Default Value	Description
fTargetPos	float[6]		Array representing incremental motion values for the current cycle. Order: [X, Y, Z, Rx, Ry, Rz] Units: mm for translation, deg for rotation.

Return

Value	Description
0	Failed to apply alter motion.
1	Successfully applied the incremental motion.

Example

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

// Thread continuously sending small incremental poses
void ThreadFunc() {
    CDRFLEx drfl;
    float delta[6] = {10.0f, 0.0f, 0.0f, 10.0f, 0.0f, 0.0f};  // ΔX=10mm, ΔRx=10°
    while (true) {
        drfl.alter_motion(delta);
        std::this_thread::sleep_for(std::chrono::milliseconds(20));  // must match enable_alter_motion cycle
    }
}

int main() {
    CDRFLEx drfl;

    // 1) Start background thread for continuous alter motion
    std::thread th(ThreadFunc);

    // 2) Enable alter motion mode (20 ms cycle)
    float limitDpos[2] = {50.0f, 90.0f};
    float limitDposPer[2] = {5.0f, 50.0f};
    drfl.enable_alter_motion(20, PATH_MODE_DPOS, COORDINATE_SYSTEM_BASE,
                             limitDpos, limitDposPer);

    // 3) Let it run for a while to apply incremental corrections
    std::this_thread::sleep_for(std::chrono::seconds(3));

    // 4) Stop alter motion mode safely
    drfl.disable_alter_motion();
    th.detach();

    return 0;
}

Caution

alter_motion() can be executed only inside a user thread.
The update rate must match the cycle time set in enable_alter_motion.
Input values follow fixed XYZ notation, and must not exceed configured limits (fLimitDpos, fLimitDposPer).