Flexible soft and stiffness-controllable surgical manipulators enhance the manoeuvrability of surgical tools during Minimally Invasive Surgery (MIS), as opposed to conventional rigid laparoscopic instruments. These flexible and soft robotic systems allow bending around organs, navigating through complex anatomical pathways inside the human body and interacting inherently safe with its soft environment. Shape sensing in such systems is a challenge and one essential requirement for precise position feedback control of soft robots. This paper builds on our previous work integrating multiple optical fibres into a soft manipulator to estimate the robot's pose using light intensity modulation. Here, we present an enhanced version of our embedded bending/shape sensor based on electro-conductive yarn. The new system is miniaturised and able to measure bending behaviour as well as elongation. The integrated yarn material is helically wrapped around an elastic strap and protected inside a 1.5mm outer-diameter stretchable pipe. Three of these resulting stretch sensors are integrated in the periphery of a pneumatically actuated soft manipulator for direct measurement of the actuation chamber lengths. The capability of the sensing system in measuring the bending curvature and elongation of the arm is evaluated.
In order to determine the cause of and to treat an abnormal heart rhythm, electrophysiological studies and ablation procedures of the heart sensorized catheters are required. During catheterization, force sensors at the tip of the catheter are essential to provide quantitative information on the interacting force between the catheter tip and the heart tissue. In this study, we are proposing a small sized, robust, and lowcost three-axis force sensor for the catheter tip. The miniaturized force sensor uses fiber-optic technology (small sized multi-cores optical fiber and a CCD camera based on image processing to read out the forces by measuring light intensity which are modulated as a function of the applied force. In addition, image processing techniques and a Kalman filter are used to reduce the noise of the light intensity signals. In this paper, we explain the design and fabrication of our three-axis force sensor and our approach for reducing noise levels by applying a Kalman filter model, and finally discuss the calibration procedure. Moreover, we provide an assessment of the performance of the proposed sensor.
This paper presents a multi-axis force/torque sensor based on simply-supported beam and optoelectronic technology. The sensor’s main advantages are: (1) Low power consumption; (2) low-level noise in comparison with conventional methods of force sensing (e.g., using strain gauges); (3) the ability to be embedded into different mechanical structures; (4) miniaturisation; (5) simple manufacture and customisation to fit a wide-range of robot systems; and (6) low-cost fabrication and assembly of sensor structure. For these reasons, the proposed multi-axis force/torque sensor can be used in a wide range of application areas including medical robotics, manufacturing, and areas involving human–robot interaction. This paper shows the application of our concept of a force/torque sensor to flexible continuum manipulators: A cylindrical MIS (Minimally Invasive Surgery) robot, and includes its design, fabrication, and evaluation tests.
This paper describes the modeling of a soft threeaxis force sensor. The sensor has a cylindrical cantilever beam made of silicone rubber that compresses and bends when normal and tangential forces are applied. The displacement of the beam's end is calculated by measuring the change of the magnetic field emitted by a permanent magnet embedded in the soft beam, at fixed points in space. Spring theory and bending theory are used to calculate the normal and tangential force components. The normal forces calculated by the proposed model and the measured values have an error less than 5% validating the analogy of the sensor to a soft cantilever beam under compression and bending. The proposed mathematical model is simple and faster than a finite-element model, and accurately represents the non-linear behavior of the sensor's physical effects to applied loads.Index Terms-Force sensor, magnetic field measurement, modeling, soft embodiment.
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