check_position_condition_rel

This function checks whether the relative position of a specified axis lies within the given range with respect to a defined target position. It can be called continuously inside control loops (e.g., while or if) to monitor real-time motion conditions.

The axis and target position values are interpreted according to the reference coordinate system defined by set_ref_coord. If eForceReference is set to COORDINATE_SYSTEM_TOOL, the fTargetPos should be expressed in the BASE coordinate system.

Refer to check_position_condition_abs for absolute position comparisons.

Definition
DRFLEx.h within class CDRFLEx, public section (line 957)

bool check_position_condition_rel(FORCE_AXIS eForceAxis,
                                  float fTargetMin,
                                  float fTargetMax,
                                  float fTargetPos[NUM_TASK],
                                  COORDINATE_SYSTEM eForceReference = COORDINATE_SYSTEM_TOOL) {
    return _check_position_condition_rel(_rbtCtrl, eForceAxis, fTargetMin, fTargetMax, fTargetPos, eForceReference);
};

Parameter

Parameter Name	Data Type	Default Value	Description
eForceAxis	FORCE_AXIS		Axis to evaluate (X, Y, Z, or Rx, Ry, Rz).
fTargetMin	float		Minimum allowable deviation from the target position [mm or deg].
fTargetMax	float		Maximum allowable deviation from the target position [mm or deg].
fTargetPos	float[6]		Reference target position of six task coordinates.
eForceReference	COORDINATE_SYSTEM	`COORDINATE_SYSTEM_TOOL`	Reference coordinate system for relative comparison.

Return

Value	Description
1	Condition True — current position within range.
0	Condition False — current position outside range.

Example A — Manual Mode (Position Deviation Check During Teaching)

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

int main() {
    CDRFLEx drfl;
    // Preconditions: Connected, servo ON, Teach mode active

    // 1) Define reference target pose
    float posTarget[6] = {400.f, 500.f, 600.f, 0.f, 180.f, 0.f};

    // 2) Check if current X position is within ±5 mm of target
    bool cond = drfl.check_position_condition_rel(FORCE_AXIS_X, -5.f, 5.f, posTarget, COORDINATE_SYSTEM_TOOL);

    printf("Relative X-position condition: %s\n", cond ? "TRUE" : "FALSE");
    return 0;
}

Example B — Auto Mode (Insertion Approach Verification)

// Preconditions:
// - Auto mode active
// - Robot approaching target under compliance control

// 1) Define target insertion position
float targetPose[NUM_TASK] = {550.f, 200.f, 80.f, 180.f, 0.f, 0.f};

// 2) Move near the insertion point
drfl.movel(targetPose, (float[2]){80.f, 25.f}, (float[2]){300.f, 100.f});
drfl.mwait();

// 3) Check relative position condition along Z-axis
bool bApproached = drfl.check_position_condition_rel(FORCE_AXIS_Z, -3.f, 2.f, targetPose, COORDINATE_SYSTEM_TOOL);

if (bApproached)
    printf("Robot within insertion tolerance range.\n");
else
    printf("Robot not yet in range.\n");

// 4) Once in range, proceed with next task (e.g., force-controlled insertion)
if (bApproached) {
    float fTarget[6] = {0.f, 0.f, 20.f, 0.f, 0.f, 0.f};
    unsigned char dir[6] = {0, 0, 1, 0, 0, 0};
    drfl.set_desired_force(fTarget, dir, COORDINATE_SYSTEM_TOOL, 0.3f);
}

Notes & Best Practices

Use check_position_condition_rel() for fine approach detection, alignment checks, or position safety thresholds.
When using COORDINATE_SYSTEM_TOOL, always define fTargetPos in BASE coordinates.
Combine with check_force_condition for hybrid force-position control logic.
In Auto mode, call within control loops or conditional checks to trigger the next motion or task step dynamically.
For absolute coordinate comparison, use check_position_condition_abs.