Enhancing Hybrid Force/Velocity Control with Visual Servoing in Robot-Assisted Total Knee Arthroplasty

In robot-assisted orthopedic surgery the use of semi-active systems is the most promising technique for future applications and research. The robot device acts as an advanced tool, combining the experience of the surgeon with the advantages of a robot system. These include among others high accuracy, repeatability, and no fatigue. Contrary to active systems the surgeon interacts continuously with the device and therefore also within the operation area. The semi-active system is directly humanly powered during the intervention. No invasive process is executed autonomously by the robot. The surgeon has full control and supervision during the operation. A hybrid force/velocity approach is developed to implement a semi-active strategy on an industrial robot device. The robot end-effector is moved by the power of the surgeon. The actuated forces are transformed into robot joint velocities. To overcome the drawbacks of invasive clamping and the necessity of renewing the initial registration during intervention a vision sensor is included into the system. With the help of dynamic registration the vision system feeds back unexpected motions in the workspace to the robot controller, allowing the device to compensate autonomously for these changes. Two set-ups are considered and initial experimental results are obtained under laboratory conditions. The proximal tibia cut of total knee arthroplasty is used as a proof of concept