In order to use a wrist-mounted sensor (such as a camera) for a robot task, the position, and orientation of the sensor with respect to the robot wrist frame must be known. We can find the sensor mounting position by moving the robot and observing the resulting motion of the sensor. This yields a homogeneous transform equation of the form AX=XB, where A is the change in the robot wrist position, B is the resulting sensor displacement, and X is the sensor position relative to the robot wrist. The solution to an equation of this form has one degree of rotational freedom and one degree of translational freedom if the angle of rotation of A is neither 0 nor tt radians. To solve for X uniquely, it is necessary to make two arm movements and form a system of two equations of the form: A1X=XB1 and A2X=XB2. A closed-form solution to this system of equations is developed and the necessary conditions for uniqueness is stated.
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