Studies On Interaction Force Acquisition And Control Technology In Thoracoscopic Virtual Sugery

In view of the laparoscopic surgeon training, the key technology of the virtual surgeryhaptic interaction system is researched to improve surgeons‘operation feeling. The hapticinteraction system can provide the realistic haptic perception with the simulation operationusing haptic interaction device and the force model of soft tissue.The haptic interaction device is composed of many parts and can move in multiple DOF.The gravity center of the operation lever will not be located on the support point in themovement space all the time. When surgeons operate the haptic interaction device, the gravityforce will worsen the surgeons feel with the gravity center movement. So the gravitycompensation is required. The screw theory is used to make the spatial analysis and the staticanalysis, and based on the analysis the component force is calculated for the motors‘compensation torque. The ADAMS is used to verify the correction of the calculatedcompensation force through the displacement error comparison before and after gravitycompensation.Haptic interaction system delay makes the controller cannot response timely to thevariable changes and the system is difficult to adapt to the changes of the virtual environmentmodel parameters. The haptic interaction system model including haptic interaction devicedynamics model, the motor electrical model and virtual environment model is analyzed. Theinternal model control is used to improve the robustness of the system and eliminate thesystem delay and the adaptive internal model control is used to real-time correct the systemmodel parameters. Finally, the results of the simulation and experiment indicate that thecontrol strategy can not only reduce the overshoot value to4.55%but also less the controltime to0.02s, and the system performance is improved.To measure the tool-tissue interaction force, the sliding structure six-axis force/toque sensor is developed and the sensor features small size, low range and high resolution. Theoverall size is52mm328mm, the measurement range is20N, the resolution of the sensor is20mN and the measurement accuracy is1%F.S.. Both the theoretical analysis and finiteelement analysis are used to indicate that the sensor can decouple more thoroughly thefloating beams structure sensor. The maximum coupling error can be decreased to0.34%,which is less than1.14%of floating beams structure sensor. Considering the machining error,the influence of the sliding clearance and the asymmetric grooves on decoupling is analyzedand the required machining tolerance level GB/T1800.3-1998is given. Finally, the sensorcalibration device is designed to make the sensor calibration and the static calibration matrix,the coupling error and the sensitivity is obtained.The five degrees of freedom haptic information acquisition device is designed to get theinteraction information acquisition between the isolated soft tissue and the surgical toolsduring the puncture, cutting, clamping and suturing operation. The conversion state of thedeformation, cracking and fracture is analyzed and the deformation force, friction force andrupture force during the force interaction is analyzed. The exponential and polynomial forcemodel of the soft tissue during the puncture, cutting, clamping and suturing operation isestablished based on the haptic information acquisition experiments. The force model canillustrate the viscoelastic properties of soft tissue and the polynomial force model can beeasily realized by the computer.