Yohan Noh

Robust real time material classification algorithm using soft three axis tactile sensor: Evaluation of the algorithm

Materials and textures identification is a desired ability for robots. Developing such systems require tactile sensors that have enough sensitivity and spatial resolution, and the computational intelligence to meaningfully interpret sensor data. This paper introduces a texture classification algorithm utilizing support vector machine (SVM) classifier. Data taken from a novel three axis tactile sensor that utilize magnetic flux measurements for transduction was used to obtain the three dimensional tactile data. Frobenius norm calculated from the covariance matrix of the above data and the mean values of the three dimensional sensor data were used as features. Palpation velocity and small vertical load variances had minimum influence on the proposed algorithm. We have compared this algorithm with two other classification methods. They are: classify using the feature spatial period that is calculated from principal frequencies of the textures/material, and classify using neural network classifier with special properties of each materials tactile signals as features. For eight classes of material, the proposed algorithm performed faster and more accurately than the comparators when the scanning velocity and the vertical load varied.

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.

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.

Bio-inspired tactile sensor sleeve for surgical soft manipulators

Robotic manipulators for Robot-assisted Minimally Invasive Surgery (RMIS) pass through small incisions into the patients body and interact with soft internal organs. The performance of traditional robotic manipulators such as the da Vinci Robotic System is limited due to insufficient flexibility of the manipulator and lack of haptic feedback. Modern surgical manipulators have taken inspiration from biology e.g. snakes or the octopus. In order for such soft and flexible arms to reconfigure itself and to control its pose with respect to organs as well as to provide haptic feedback to the surgeon, tactile sensors can be integrated with the robots flexible structure. The work presented here takes inspiration from another area of biology: cucumber tendrils have shown to be ideal tactile sensors for the plant that they are associated with providing useful environmental information during the plants growth. Incorporating the sensing principles of cucumber tendrils, we have created miniature sensing elements that can be distributed across the surface of soft manipulators to form a sensor network capable of acquire tactile information. Each sensing element is a retractable hemispherical tactile measuring applied pressure. The actual sensing principle chosen for each tactile makes use of optic fibres that transfer light signals modulated by the applied pressure from the sensing element to the proximal end of the robot arm. In this paper, we describe the design and structure of the sensor system, the results of an analysis using Finite Element Modeling in ABAQUS as well as sensor calibration and experimental results. Due to the simple structure of the proposed tactile sensor element, it is miniaturisable and suitable for MIS. An important contribution of this work is that the developed sensor system can be ”loosely” integrated with a soft arm effectively operating independently of the arm and without affecting the arms motion during bending or elongation.

Novel uniaxial force sensor based on visual information for minimally invasive surgery

This paper presents an innovative approach of utilising visual feedback to determine physical interaction forces with soft tissue during Minimally Invasive Surgery (MIS). This novel force sensing device is composed of a linear retractable mechanism and a spherical visual feature. The sensor mechanism can be adapted to endoscopic cameras used in MIS. As the distance between the camera and feature varies due to the sliding joint, interaction forces with anatomical surfaces can be computed based on the visual appearance of the feature in the image. Hence, this device allows the measurement of forces without introducing new stand-alone sensors. A mathematical model was derived based on validation data tests and preliminary experiments were conducted to verify the models accuracy. Experimental results confirm the effectiveness of our vision based approach.

A continuum body force sensor designed for flexible surgical robotics devices

This paper presents a novel three-axis force sensor based on optical photo interrupters and integrated with the robot arm STIFF-FLOP (STIFFness controllable Flexible and Learnable Manipulator for Surgical Operations) to measure external interacting forces and torques. The ring-shape bio-compatible sensor presented here embeds the distributed actuation and sensing system of the STIFF-FLOP manipulator and is applicable to the geometry of its structure as well to the structure of any other similar soft robotic manipulator. Design and calibration procedures of the device are introduced: experimental results allow defining a stiffness sensor matrix for real-time estimation of force and torque components and confirm the usefulness of the proposed optical sensing approach.

Tendon-Based Stiffening for a Pneumatically Actuated Soft Manipulator

There is an emerging trend toward soft robotics due to its extended manipulation capabilities compared to traditionally rigid robot links, showing promise for an extended applicability to new areas. However, as a result of the inherent property of soft robotics being less rigid, the ability to control/obtain higher overall stiffness when required is yet to be further explored. In this letter, an innovative design is introduced which allows varying the stiffness of a continuum silicon-based manipulator and proves to have potential for applications in Minimally Invasive Surgery. Inspired by muscular structures occurring in animals such as the octopus, we propose a hybrid and inherently antagonistic actuation scheme. In particular, the octopus makes use of this principle activating two sets of muscles-longitudinal and transverse muscles-thus, being capable of controlling the stiffness of parts of its arm in an antagonistic fashion. Our designed manipulator is pneumatically actuated employing chambers embedded within the robots silicone structure. Tendons incorporated in the structure complement the pneumatic actuation placed inside the manipulators wall to allow variation of overall stiffness. Experiments are carried out by applying an external force in different configurations while changing the stiffness by means of the two actuation mechanisms. Our test results show that dual, antagonistic actuation increases the load bearing capabilities for soft continuum manipulators and thus their range of applications.

Development of the evaluation system for the Airway Management Training System WKA-1R

The emerging field of medical robotics is aiming in introducing intelligent tools. More recently, thanks to the innovations on robot technology (RT), advanced medical training systems have been introduced to improve the skills of trainees. The principal challenges of developing efficient medical training systems are simulating real-world conditions and assuring their effectiveness. Up to now, different kinds of medical training devices have been developed which are designed to reproduce with high fidelity the human anatomy. Due to their design concept, the evaluation of progress of the trainees is based on subjective assessments limiting the understanding of their effectiveness. In this paper, we are presenting our research towards developing a patient robot designed to simulate the real-world task conditions and providing objective assessments of the training achievements. Due to its complexity; in this paper, we are presenting as a first approach the development of the Waseda-Kyotokagaku Airway No. 1R (WKA-1R) which includes a human patient model with embedded sensors in order to provide objective assessments of the training progress. In particular, we have proposed an evaluation function to quantitatively evaluate the task performance by determining the weighting of coefficients. In order to determine the weighting of coefficients, we applied discriminant analysis. In order to determine the effectiveness of the proposed evaluation function to detect differences among different levels of expertise, an experimental setup was carried out. From the experimental results, we could find a significant difference between both groups (P < 0.05).

Development of a robot which can simulate swallowing of food boluses with various properties for the study of rehabilitation of swallowing disorders

Many patients suffer from swallowing disorders (dysphagia). There are many treatments for these disorders, such as swallowing therapy, surgery, and dietary modification. In our study, we focuse on dietary modification, a common approach. Normally, the swallowing is affected by food bolus properties such as hardness, stickiness and rheological characteristics, and dietary modifications can prevent swallowing disorder patients from suffering dysphagia (aspiration), as well as promote good nutrition. Based on these facts, our goal is to find foods which do not cause dysphagia, and develop food for swallowing disorder patients accordingly. Therefore, we are proposing an in-vitro Dynamic VFSS (Video Fluorographic Swallowing Study) simulation system which uses advanced robotics technology to mimic the dynamic process of swallowing and monitors the status and movement of the food bolus inside the system, for objective evaluation of the swallowing process. The dynamic VFSS simulation system consists of a head, mandible, neck, tongue, pharynx, and larynx which reproduce human anatomy. It is driven by 16 actuators with wire driving mechanisms. In this paper, we will present the dynamic VFSS simulation unit in detail. In addition, we will detail a set of the experiments carried out to determine whether food bolus properties can affect dysphagia or not. To observe the movement of the food bolus, we use a Video Fluoroscopy (VF) unit. The results of the experiments show that thickened boluses have a tendency to leave residue in the epiglottic vallecula. In contrast, liquids cause less residue, and increase the risk of dysphagia (aspiration). Moreover, this study shows that the frontal image, as well as the lateral image, is important for evaluating residual food in the oral- pharyngeal space.

Embedded electro-conductive yarn for shape sensing of soft robotic manipulators.

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 robots 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.