A method including, based upon a desired path of a reference point from a start position to an end position, where the reference point is on an end effector on a robot arm, determine an included angle that corresponds to the start position and the end position, calculating a trajectory in radial coordinates of the reference point on the end effector at least partially based upon the included angles; calculating corresponding angular coordinates of the reference point on the end effector, based on the calculated radial coordinates, so that the reference point follows the desired path; using a modified formulation of inverse kinematics, converting the radial and angular coordinates supplemented with the included angles of the trajectory and corresponding angular velocity and acceleration of the end effector to form motion setpoints for the robot arm; and controlling the motors of the robot drive.