Leveraging the Fulcrum Point in Robotic Minimally Invasive Surgery

Abstract

In robotic Minimally Invasive Surgery (MIS) the incision point acts as a fulcrum around which the surgical instrument pivots. The fulcrum point has been the topic of much research. Mechanisms have been invented to enforce instrument motion about such a fulcrum. Other systems establish a fulcrum through coordinated control of their joints. For laparoscopists, the fulcrum point is an obstacle to overcome through a lot of training. For robots, it is a hurdle requiring careful consideration. In this paper, new estimation methods are proposed to exploit the properties of a fulcrum and turn its presence into an advantage. The paper starts by presenting a novel fulcrum estimation method that is robust against measurement noise and quantization effects. A general fulcrum refinement method is proposed next. This method can be used as add-on to ameliorate alternative estimation approaches. It is shown how the fulcrum can also be leveraged to get accurate, high-bandwidth estimates of the instrument tip. The quality with which the instrument tip is estimated has a large impact on the performance of advanced guidance schemes, such as haptic virtual walls. User tests are included, demonstrating substantially improved guidance thanks to the algorithms presented in this work.

Surgical Robotic Arm with Pneumatic Semi-active Joints for Load Reduction on Tool-insertion Port

“…However, q 4 and q 5 are used for calculation of feedforward control. Thus, it is necessary to obtain q 1 -q 8 . Considering this method, we can separately deal with the inverse kinematics of its arm and that of forceps.…”

“…Estimation methods for the insertion port have been researched. (7,8) In this study, we easily estimated the insertion port using the velocity, angular velocity, and geometric information of the wrist of the arm.…”

“…In addition, algorithms for insertion port estimation have been studied to deal with misalignment. (7,8) However, the arm cannot compensate for the weight of its forceps and external forces owing to its passive joints. As a result, forces are exerted on the insertion port and friction increases.…”

A Hybrid Active/Passive Wrist Approach for Increasing Virtual Fixture Stiffness in Comanipulated Robotic Minimally Invasive Surgery

“…From (14), it can be seen that the fulcrum causes a distortion of the stiffness from distal to proximal side, in both magnitude (s f ) and direction (R f ). This is illustrated in Fig.…”

“…A time-consuming alignment procedure is avoided. Instead, the location of the incision point can be estimated by automated routines as soon as the instrument is inserted [13], [14]. These routines can run continuously to accommodate for patient motion and incision point compliance.…”