Hydraulic Micro Device with Force Sensing for Measurement of Mechanical Characteristics
Tohru Sasaki*,, Yudai Fujiwara**, Kaoru Tachikawa**, Kenji Terabayashi*, and Kuniaki Dohda***
*Department of Mechanical and Intellectual Systems Engineering, University of Toyama
3190 Gofuku, Toyama-shi, Toyama 930-8555, Japan
**Graduate School of Science and Engineering for Education, University of Toyama, Toyama, Japan
***Department of Mechanical Engineering, Northwestern University, Illinois, USA
The medical and bio-engineering fields have been increasingly using information and communication technology. To introduce robots into surgical procedures, data on surgical operations are required. Several studies have tried the creation of data on living tissues for mechanical actions, which makes determining the mechanical characteristics of living tissues vital, but few have been commonly used. Therefore, we previously developed a sensing system that uses a hydraulic-driven micro mechanism to measure the force applied to an object when it is touched. Micro force sensors are necessary for various manipulations requiring careful operation. Unfortunately, the measurement accuracy of sensors tends to reduce with the reduction in sensor size. The proportional output in conventional force sensors, such as piezoelectric sensors, also decreases when the size of the sensor is reduced. However, a micro force sensor using a hydraulic-driven micro mechanism can obtain a large output even when it is small. Our system uses Pascal’s principle to measure small forces acting on the end effector. We propose methods for identifying the mechanical characteristics of certain viscoelastic materials similar to those used in a living organ. A hydraulic-driven micro device pushes an object and measures the reaction force and its displacement. We have used two types of micro devices, micro cylinder and micro bellows. Its stiffness and viscosity coefficient are obtained through calculations using Kelvin-Voigt and Zenner models. Discrete displacement and load data are applied to the estimated model, and the mechanical characteristics of the materials are identified as a minimized value between the estimated value and experimental one. We conducted experiments using the proposed identification methods on viscoelastic materials, and the results indicate that the value provided from the Kelvin-Voigt model was near the truth value.
-  M. T. Gettman et al., “Robotic-assisted laparoscopic partial nephrectomy: Technique and initial clinical experience with DaVinci robotic system,” Urology, Vol.64, No.5, pp. 914-918, 2004.
-  K. Hongo et al., “Microsurgery-assisting robotics (NeuRobot): Current status and future perspective,” Japanese J. of Neurosurgery, Vol.20, No.4, pp. 270-274, 2011.
-  A. Garg et al., “Tumor localization using automated palpation with gaussian process adaptive sampling,” Proc. of IEEE Int. Conf. on Automation Science and Engineering, pp. 194-200, 2016.
-  S. McKinley et al., “Disposable haptic palpation probe for locating subcutaneous blood vessels in robotassisted minimally invasive surgery,” Proc. of IEEE Int. Conf. on Automation Science and Engineering, pp. 1151-1158, 2015.
-  K. Franze et al., “Spatial mapping of the mechanical properties of the living retina using scanning force microscopy,” Soft Matter, Vol.7, pp. 3147-3154, 2011.
-  T. Sasaki et al., “Hydraulically driven joint for a force feedback manipulator,” Precision Engineering, Vol.47, pp. 445-451, 2017.
-  M. Sato et al., “Nonlinear viscoelastic behaviour of canine arterial walls,” Medical and Biological Engineering and Computing, Vol.23, pp. 565-571, 1985.
-  A. Serra-Aguila et al., “Viscoelastic models revisited: characteristics and interconversion formulas for generalized Kelvin-Voigt and Maxwell models,” Acta Mechanica Sinica, Vol.35, pp. 1191-1209, 2019.
-  Y. Kitada et al., “Mechanical modelling of high damping rubber dampers using nonlinear system identification,” J. of Structural and Construction Engineering, Vol.531, pp. 63-70, 2000.
-  T. Sasaki et al., “Improving accuracy of hydraulic-driven forceps,” Proc. of the 16th Int. Conf. of the European Society for Precision Engineering and Nanotechnology, 2.07, 2016.
-  T. Sasaki et al., “Force measurement of blood vessel gripping by hydraulic-driven forceps,” Procedia CIRP, Vol.65, pp. 84-87, 2017.