Title
A Computer-Assisted Total Knee Replacement Surgical System Using a Calibrated Robot

Abstract
In the surgical replacement of the knee joint, accurate alignment of prosthetic components with respect to the mechanical axis of the leg is essential to the mobility and possibly the longevity of the joint. The correct alignment is not obvious during surgery because the long bones are largely obscured by tissue. An integrated system has been developed that allows the surgeon to accurately place prosthetic components during total knee surgery. A graphics computer displaying a 3- dimensional model of the patient's knee is used to perform accurate and informed preoperative planning. In the operating room, a robot and specially designed fixturing aid the surgeon in performing the bone resections as determined in the preoperative plan. Crucial to the accuracy of this system is the rigid immobilization of the involved bones (fixturing), the robot's ability to determine their exact locations in space (registration), and the accuracy of the robot itself (parameter identification). An overview of the system is presented here, as well as discussion of the technical issues mentioned above.

Source: IEEE Engineering in Medicine and Biology, May 1995

Title
Complete Parameter Identification of a Robot from Partial Pose Information

Abstract
The absolute accuracy of a robot depends to a large extent on the accuracy with which its kinematic parameters are known. Many methods have been explored for inferring the kinematic parameters of a robot from measurements taken as it moves. Some require an external global positioning system, usually optical or sonic. We have used instead a simple radial-distance linear transducer (LVDT) which measures the distance from several fixed points in the workspace to the robot's endpoint. This incomplete pose information (one dimensional rather than six dimensional) is accumulated as the robot endpoint is moved within one or more hemispherical "shells" centered about the fixed points. Optimal values for all of the independent kinematic parameters of the robot can then be found.

Here we discuss the motivation, theory, implementation, and performance of this particularly easy calibration and parameter identificat on method. We also address a recent disagreement in the literature about the type of measuring system (in particular, the dimensionality of the pose measurements) needed to fully identify a robot's kinematic parameters.

Source: IEEE Control Systems 13 (5), October 1993