fkin (forward kinematics)

This function computes the TCP pose (Task Space Position and Orientation) from the given joint angles in the robot’s kinematic chain. It is the inverse operation of ikin, converting joint values to Cartesian coordinates.

Definition
DRFLEx.h within class CDRFLEx, public section

LPROBOT_POSE fkin(
    float fSourcePos[NUM_JOINT],
    COORDINATE_SYSTEM eTargetRef = COORDINATE_SYSTEM_BASE
) {
    return _fkin(_rbtCtrl, fSourcePos, eTargetRef);
};

Parameter

Parameter Name	Data Type	Default Value	Description
fSourcePos	float[6]		Joint positions for each axis [deg]. Represents the current robot configuration in joint space.
eTargetRef	COORDINATE_SYSTEM	COORDINATE_SYSTEM_BASE	Reference coordinate system for TCP output.

Return

Value	Description
LPROBOT_POSE	Structure containing the resulting TCP position and orientation (x, y, z, Rx, Ry, Rz).

Note

This call waits for the controller to answer.

The returned pointer refers to storage in the CDRFLEx object that other DRFL calls and every reconnect reuse; copy the structure before making another DRFL call. The 3-argument ikin returns its result in storage shared by all CDRFLEx objects in the process instead; see ikin. Except for get_user_home, the pointer is never NULL; do not use a NULL check to detect failure.

Example

float q1[6] = { 0.f, 90.f, 0.f, 90.f, 90.f, 0.f };
drfl.movej(q1, 60, 30);  // Move robot to initial joint pose

float q2[6] = { 30.f, 0.f, 0.f, 0.f, 90.f, 0.f };
LPROBOT_POSE res = drfl.fkin(q2, COORDINATE_SYSTEM_WORLD);

float vel[2] = { 100, 100 };
float acc[2] = { 200, 200 };

float tcp[6] = { 0 };
for (int i = 0; i < 6; ++i)
    tcp[i] = res->_fPosition[i];

drfl.movel(tcp, vel, acc);

This example calculates the forward kinematics for joint angles q2 in the WORLD coordinate system, producing a TCP pose tcp. The resulting pose is then used as a motion target for movel(), demonstrating how FK results can be directly reused for Cartesian control.