Giuliano Giacoppo

Zusammenfassung

This paper provides a preliminary experimental assessment of a flexible endoscope driven by antagonistic twisted string actuation (TSA). Traditional endoscope designs have relied on manual manipulation or actuation systems lacking force control loops, limiting their versatility and ease of use. The proposed approach leverages the benefits of additive manufacturing to create customizable, deformable endoscope’s tip structures, while TSA provides an efficient and potentially compact actuation mechanism. The experimental evaluation encompasses two key aspects of endoscope performance: tissue interaction and stiffness variation. Through a series of controlled experiments, the endoscope’s ability to interact with mock biological tissues is assessed, demonstrating successful force application using both agonist-only and antagonistic functioning modalities. Furthermore, the endoscope’s resilience to external disturbances is evaluated, with results showing significant improvements in stiffness and response to perturbations when utilizing antagonistic control. These findings highlight the potential of the proposed device to improve flexible endoscopy design and functionality. By integrating advanced manufacturing techniques with innovative actuation mechanisms, robotic flexible endoscopes can offer enhanced maneuverability, diagnostic precision, and patient safety.

Zusammenfassung

This research project investigated the additive manufacturing of pneumatic actuators based on the principle of droplet dosing using an Arburg Freeformer 300-3X 3D printer. The developed structure consists of a porous inner filling and a dense, airtight chamber. By selectively varying the filling densities of the porous inner filling, different membrane deflections of the actuator were achieved. By linking the actuators, a pneumatic network actuator was developed that could be used in endorobotics. To describe the membrane deflection of an additively manufactured pneumatic actuator, a mathematical model was developed that takes into account the influence of additive manufacturing and porous filling. Using a dedicated test rig, the predicted behavior of the pneumatic actuators was shown to be qualitatively consistent. In addition, a pneumatic network actuator (PneuNet) with a diameter of 17 mm and a height of 76 mm, consisting of nine chambers with different filling densities, could be bent through 82° under a pressure of 8 bar. Our study shows that the variation of filling densities during production leads to different membrane deflections. The mathematical model developed provides satisfactory predictions, although the influence of additive manufacturing needs to be determined experimentally. Post-processing is still a necessary step to realize the full bending potential of these actuators, although challenges regarding air-tightness remain. Future research approaches include studying the deflection behavior of the chambers in multiple directions, investigating alternative materials, and optimizing the printing process to improve mechanical properties and reliability.

Zusammenfassung

When manipulating tissue during medical interventions, high-accuracy movements are important to avoid injuries. However, feedback is limited and it is hard to establish control loops to ensure correct movements. We propose the use of a novel highly compact 6-axis force / torque sensor (Ø 10.5 mm x 11.0 mm) within a hand piece to determine low forces and torques during various small-scale procedures including gentle tool-tissue interaction. For a first validation of the system, different venepuncture cannulas were connected to the sensor top and driven into skinned fruits (toma-toes and grapes) as well as into a silicone block. During insertion of the needle tips, maximum forces of 74 – 158 mN (tomato) and 51 - 161 mN (grape) were recorded, and steadily increasing forces in the range of 0 – 250 mN when insert-ing needles 7.5 mm into silicone. For a 0.99 g screw nut (9.73 mN), the measured gravitational force was 10.6 ± 1.5 mN during ten measurement sets. During the insertion, needle torques of up to 9.5 mNm were observed. Different cutting phases were seen similar to the phases during needle penetration testing. We conclude that the compact measurement setup used is suitable to measure the low forces and torques occurring when cutting soft, aqueous human tissues with or without skin-like layers.

Zusammenfassung

In conventional laparoscopy, the field of view of the surgeon is limited. Angled laparoscopes enable the observation of surrounding structures, however, to change the viewing perspective on a specific object, permanent repositioning and rotation of the shaft is required. In this paper, a demonstrator of a steerable flexible laparoscope is presented, enabling the user to intuitively adjust the perspective onto an object by means of a single control element. The laparoscope provides a viewing angle of ± 50° at 50 mm working distance. In first tests, the presented laparoscope showed advantages regarding intuitiveness of the control, easier handling, and improved depth perception.

Zusammenfassung

Accurate measurement of interaction forces during robot-assisted surgery requires compact force sensing modalities in the surgical tools, thus might add considerable cost to the setup. Measuring the motor current to estimate gripping forces, is an advantageous approach since no expensive force sensor is needed. In this paper, a mechanical interface is presented, which allows actuating conventional articulated instruments for robot-assisted surgery. The interface features the estimation of static gripping forces at the instrument’s tip based on the motor current. The evaluation shows reproducible results, and the current-based approach seems to be a cost-efficient way to estimate gripping forces.

Zusammenfassung

A twisted string actuator (TSA) is a small, strong, lightweight, and low-cost gear, transforming rotation into a linear pulling movement. The TSA consists of two or more strings that are twisted along their common longitudinal axis. The helix formed in this process becomes shorter the further the bundle is twisted. A possible application is a tendon-based endoscopic robot. To control the movement of the endoscope, a precise contraction of the tendon is necessary. Since the strings of the TSA show an elastic behaviour, position feedback is needed to determine the exact movement of the TSA. In this paper, a TSA with a closed-loop position control by a low-cost displacement sensor is presented.

Zusammenfassung

To assist the insertion of a robot-aided endoscope during colonoscopy, a measuring system is required so that the endoscope tip can align automatically and thus find the curved pathway of the large intestine. To achieve this, a self-expanding nitinol wire basket is used to sense the contour of the intestine. As the wire basket touches the wall, it is deflected towards the center of the intestine. The relative position of the wire basket within the camera image is captured, which describes the desired direction to follow the organ. To identify the wire basket in the image, the original RGB image stream is converted into the HSV (hue, saturation, value) color space. Thus, a binary image can be created, in which only the neon-green color portion of the wire basket is visible as a cross. The Hough Transformation is used to search for straight lines in the binary image. Once two lines are found, the intersection point can be calculated and thus its position in the image. The evaluation of the execution time of the algorithm on a live stream was 45 ± 31 ms on average. The algorithm robustly recognizes the wire basket even if it was not visible to the human eye in the original RGB image due to deficient lighting.