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Force Estimation of the Surgical Instrument tip by a 6-DOF Proximal Force Sensor Located at the End of the Sina Surgical Robot Instrument

Shayestehpour, Hamed | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50200 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farahmand, Farzam
  7. Abstract:
  8. Measurement of laparoscopic instrument tip forces plays an important role in the research area of controlling robotic surgeries. The first attempts in this topic were estimating the tip forces using distal force sensors, but these methods were too expensive and required sterilization. On the other hand, proximal sensors do not suffer from the distal sensors problems, however, they were not used to estimate the instrument tip force in previous works. In this regard, the effectiveness of proximal sensors in this project was investigated. To do so, firstly, an appropriate plan for estimating the forces of the laparoscopic instrument’s tip was found using a proximal force sensor, located at the end of the laparoscopic instrument in “Sina” robot in static state. Then, an analytical model for estimating these forces was proposed. After selecting spherical joint type for trocar holder design and ensuring the proper signals in the sensor, an initial analytical model was obtained using the governing equations. According to the proximal position of the sensor, three submodels were supposed to identify the weight effect, the friction between the trocar and the instrument and the forces and momentums of the abdominal wall. The static weight compensator submodel was obtained using the direct kinematics of the robot. The Friction submodel was consisted of two static and dynamic parts, which were used by the instrument’s curvature equation and the friction between instrument and trocar to obtain them. The abdominal wall submodel can model the abdominal wall rotational stiffness just by knowing the information of the rotational stiffness of the instrument around the spherical joint, and therefore the abdominal momentum in different situations. To calculate tip force’s instrument in the direction of it (y-axis) and perpendicular to the instrument (transverse plane, x-z), the friction and abdominal wall submodels were used, respectively. Finally, the maximum error of the x, y, z tip forces and the total force in the final model and different situations were obtained as 0.8, 1.2, 1 and 0.9 N respectively when tip force was around 8 N. Final model was an appropriate model to calculate the tip force of the laparoscopic instrument without having instrument tip momentums
  9. Keywords:
  10. Robotic Laparascopic Instrument ; Force Estimation ; Friction Between Trocar and Instrument ; Abdominal Rotational Stiffness ; Spherical Joint Type of Trocar Holder ; Proximal Force Sensor

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