Macrobend optical sensing for pose measurement in soft robot arms

This paper introduces a pose-sensing system for soft robot arms integrating a set of macrobend stretch sensors. The macrobend sensory design in this study consists of optical fibres and is based on the notion that bending an optical fibre modulates the intensity of the light transmitted through the fibre. This sensing method is capable of measuring bending, elongation and compression in soft continuum robots and is also applicable to wearable sensing technologies, e.g. pose sensing in the wrist joint of a human hand. In our arrangement, applied to a cylindrical soft robot arm, the optical fibres for macrobend sensing originate from the base, extend to the tip of the arm, and then loop back to the base. The connectors that link the fibres to the necessary opto-electronics are all placed at the base of the arm, resulting in a simplified overall design. The ability of this custom macrobend stretch sensor to flexibly adapt its configuration allows preserving the inherent softness and compliance of the robot which it is installed on. The macrobend sensing system is immune to electrical noise and magnetic fields, is safe (because no electricity is needed at the sensing site), and is suitable for modular implementation in multi-link soft continuum robotic arms. The measurable light outputs of the proposed stretch sensor vary due to bend-induced light attenuation (macrobend loss), which is a function of the fibre bend radius as well as the number of repeated turns. The experimental study conducted as part of this research revealed that the chosen bend radius has a far greater impact on the measured light intensity values than the number of turns (if greater than five). Taking into account that the bend radius is the only significantly influencing design parameter, the macrobend stretch sensors were developed to create a practical solution to the pose sensing in soft continuum robot arms. Henceforward, the proposed sensing design was benchmarked against an electromagnetic tracking system (NDI Aurora) for validation

Modular soft mechatronic manipulator for minimally invasive surgery (MIS): overall architecture and development of a fully integrated soft module

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A Three-Axial Body Force Sensor for Flexible Manipulators

This paper introduces an optical based three axis force sensor which can be integrated with the robot arm of the EU project STIFF-FLOP (STIFFness controllable Flexible and Learnable Manipulator for Surgical Operations) in order to measure applied external forces. The structure of the STIFF-FLOP arm is free of metal components and electric circuits and, hence, is inherently safe near patients during surgical operations. In addition, this feature makes the performance of this sensing system immune against strong magnetic fields inside magnetic resonance (MR) imaging scanners. The hollow structure of the sensor allows the implementation of distributed actuation and sensing along the body of the manipulator. In this paper, we describe the design and calibration procedure of the proposed three axis optics-based force sensor. The experimental results confirm the effectiveness of our optical sensing approach and its applicability to determine the force and momentum components during the physical interaction of the robot arm with its environment

Multi-fingered haptic palpation utilizing granular jamming stiffness feedback actuators

This paper describes a multi-fingered haptic palpation method using stiffness feedback actuators for simulating tissue palpation procedures in traditional and in robot-assisted minimally invasive surgery. Soft tissue stiffness is simulated by changing the stiffness property of the actuator during palpation. For the first time, granular jamming and pneumatic air actuation are combined to realize stiffness modulation. The stiffness feedback actuator is validated by stiffness measurements in indentation tests and through stiffness discrimination based on a user study. According to the indentation test results, the introduction of a pneumatic chamber to granular jamming can amplify the stiffness variation range and reduce hysteresis of the actuator. The advantage of multi-fingered palpation using the proposed actuators is proven by the comparison of the results of the stiffness discrimination performance using two-fingered (sensitivity: 82.2%, specificity: 88.9%, positive predicative value: 80.0%, accuracy: 85.4%, time: 4.84 s) and single-fingered (sensitivity: 76.4%, specificity: 85.7%, positive predicative value: 75.3%, accuracy: 81.8%, time: 7.48 s) stiffness feedback

Design and characterization of a robotic module for symbiotic multi-robot organism

The aim of this master thesis is the design and characterization of a robotic module for swarm robotics capable of exploring the environment Il lavoro di tesi è stato svolto nel contesto del progetto europeo Replicator, che ha come finalità quella di realizzare un numero elevato di robot autonomi in grado di auto-assemblarsi per dar vita ad organismi robotici complessi. L’obiettivo della tesi è quello di studiare e caratterizzare una delle tre piattaforme robotiche nel progetto, il robot “Scout”. In particolare, dato che il robot “Scout” ha il ruolo di esplorare l’ambiente, particolare attenzione è stata posta allo studio del meccanismo di locomozione e di un sensore di triangolazione costituito da un gruppo Laser-telecamera posizionato sulle pareti frontale e posteriore del robot. Durante la tesi è stata condotta una significativa attività di prototipazione, resa possibile da tecnologia di stampa 3D e di componentistica commerciale il cui risultato è un robot completo dotato di un sistema di locomozione tramite cingoli flessibili adatta a terreni sconnessi. E’ stato caratterizzato il sensore di triangolazione definendo la posizione relativa della telecamera e del diodo laser. Mediante un software scritto in LabVIEW è possibile localizzare ed analizzare la linea laser. Il robot, sulla base dell’informazione ottenuta dal sensore, è in grado di allinearsi autonomamente prendendo come riferimento una parete esterna dopo essersi portato ad un’opportuna distanza da tale parete

Development of a Cable Actuated Joint for a Surgical Robotic Flexible Arm

Advances in robotics surgery are focused on facilitating complex surgical procedures and overcoming existing natural limitations associated with Minimal Invasive Surgery (MIS). Distal dexterity in the robotic manipulator is of primary importance for tool manipulation and the performance of complex surgical tasks as suturing. The present work deals with the development of a cable actuated 2 degrees of freedom (DoF) joint mechanism to be int