Accurate haptic feedback is a critical challenge for surgical robots, especially for flexible endoscopic surgical robots whose transmission systems are Tendon-Sheath Mechanisms (TSMs) with highly nonlinear friction profiles and force hysteresis. For distal end haptic sensing of TSMs, this paper, for the first time, proposes to measure the compression force on the sheath at the distal end so that the tension force on the tendon, which equals the compression force on the sheath, can be obtained. A new force sensor, i.e., a nitinol tube attached with an optical Fiber Bragg Grating (FBG) fiber, is proposed to measure the compression force on the sheath. This sensor, with similar diameter and configuration (hollow) as the sheath, can be compactly integrated with TSMs and surgical end-effectors. In this paper, mechanics analysis and verification tests are presented to reveal the relationship between the tension force on the tendon and the compression force on the sheath. The proposed force sensor was calibrated in tests with a sensitivity of 24.28 pm/N and integrated with a tendon-sheath driven grasper to demonstrate the effectiveness of the proposed approach and sensor. The proposed approach and sensor can also be applied for a variety of TSMs-driven systems, such as robotic fingers/hands, wearable devices, and rehabilitation devices.

If a perforation occurs as a result of a flexible endoscopic procedure, suturing through urgent laparoscopy or open surgery may be required to repair the perforation because suturing is normally stronger than closure using existing endoscopic devices. Suturing with stitches and knots, widely adopted in open or laparoscopic surgery, is still not possible in flexible endoscopy. This is because of the confined space of the natural orifice and target area, high levels of motion dexterity and force needed for stitching and knot-tying, and critical size and strength requirements of wound closure. We present a novel flexible endoscopic robotic suturing system that is able to suture gastrointestinal defects without opening up the patient's body like in open or laparoscopic surgery. This system features a robotic needle driver and a robotic grasper, both of which are flexible, through-the-scope (small in sizes), and dexterous with five degrees of freedom. The needle driver, facilitated by the grasper, enables the surgeon to control a needle through teleoperation to make stitches and knots in flexible endoscopy. Successful in vivo trials were conducted in the rectum of a live pig to confirm the feasibility of endoscopic suturing and knot-tying using the system in a realistic surgical scenario (not possible with existing devices which are all manually driven). This new technology will change the way how surgeons close gastrointestinal defects.

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Haptic feedback for flexible endoscopic surgical robots is challenging due to space constraints for sensors and shape-dependent force hysteresis of tendon-sheath mechanisms (TSMs). This paper proposes (1) a single-axis fiber Bragg grating (FBG)-based force sensor for a TSM of a robotic arm and (2) an integrated sensor-model approach to estimate forces on other TSMs of that arm. With a robust and simple structure, a temperature-compensated sensor can be mounted on the distal sheath to measure forces applied by the TSM. This proposed sensor was integrated with a Ø4.2 mm articulated robotic arm driven by six TSMs, with a measurement error of 0.37N in this work. The measurement from the single sensor was used to identify parameters in the force-transmission models of all other TSMs in the robot, realizing a one-sensor-for-all-distal-forces measurement method. The sensor-model approach could accurately estimate the distal force with an RMSE of 0.65N. An animal study was carried out to demonstrate the sensor's feasibility in real-life surgery. The sensor-model approach presented a robust, space-saving, and cost-effective solution for haptic feedback of endoscopic robots without any assumption on the shapes of the robot.

A three-limb teleoperated robotic system with foot control for flexible endoscopic surgery