23 research outputs found
Towards tactile sensing active capsule endoscopy
Examination of the gastrointestinal(GI) tract has traditionally been performed using tethered endoscopy tools with limited reach and more recently with passive untethered capsule endoscopy with limited capability. Inspection of small intestines is only possible using the latter capsule endoscopy with on board camera system. Limited to visual means it cannot detect features beneath the lumen wall if they have not affected the lumen structure or colour. This work presents an improved capsule endoscopy system with locomotion for active exploration of the small intestines and tactile sensing to detect deformation of the capsule outer surface when it follows the intestinal wall. In laboratory conditions this system is capable of identifying sub-lumen features such as submucosal tumours.Through an extensive literary review the current state of GI tract inspection in particular using remote operated miniature robotics, was investigated, concluding no solution currently exists that utilises tactile sensing with a capsule endoscopy. In order to achieve such a platform, further investigation was made in to tactile sensing technologies, methods of locomotion through the gut, and methods to support an increased power requirement for additional electronics and actuation. A set of detailed criteria were compiled for a soft formed sensor and flexible bodied locomotion system. The sensing system is built on the biomimetic tactile sensing device, Tactip, \cite{Chorley2008, Chorley2010, Winstone2012, Winstone2013} which has been redesigned to fit the form of a capsule endoscopy. These modifications have required a cylindrical sensing surface with panoramic optical system. Multi-material 3D printing has been used to build an almost complete sensor assembly with a combination of hard and soft materials, presenting a soft compliant tactile sensing system that mimics the tactile sensing methods of the human finger. The cylindrical Tactip has been validated using artificial submucosal tumours in laboratory conditions. The first experiment has explored the new form factor and measured the device's ability to detect surface deformation when travelling through a pipe like structure with varying lump obstructions. Sensor data was analysed and used to reconstruct the test environment as a 3D rendered structure. A second tactile sensing experiment has explored the use of classifier algorithms to successfully discriminate between three tumour characteristics; shape, size and material hardness. Locomotion of the capsule endoscopy has explored further bio-inspiration from earthworm's peristaltic locomotion, which share operating environment similarities. A soft bodied peristaltic worm robot has been developed that uses a tuned planetary gearbox mechanism to displace tendons that contract each worm segment. Methods have been identified to optimise the gearbox parameter to a pipe like structure of a given diameter. The locomotion system has been tested within a laboratory constructed pipe environment, showing that using only one actuator, three independent worm segments can be controlled. This configuration achieves comparable locomotion capabilities to that of an identical robot with an actuator dedicated to each individual worm segment. This system can be miniaturised more easily due to reduced parts and number of actuators, and so is more suitable for capsule endoscopy. Finally, these two developments have been integrated to demonstrate successful simultaneous locomotion and sensing to detect an artificial submucosal tumour embedded within the test environment. The addition of both tactile sensing and locomotion have created a need for additional power beyond what is available from current battery technology. Early stage work has reviewed wireless power transfer (WPT) as a potential solution to this problem. Methods for optimisation and miniaturisation to implement WPT on a capsule endoscopy have been identified with a laboratory built system that validates the methods found. Future work would see this combined with a miniaturised development of the robot presented. This thesis has developed a novel method for sub-lumen examination. With further efforts to miniaturise the robot it could provide a comfortable and non-invasive procedure to GI tract inspection reducing the need for surgical procedures and accessibility for earlier stage of examination. Furthermore, these developments have applicability in other domains such as veterinary medicine, industrial pipe inspection and exploration of hazardous environments
Toward Bio-Inspired Tactile Sensing Capsule Endoscopy for Detection of Submucosal Tumors
© 2016 IEEE. Here, we present a method for lump characterization using a bio-inspired remote tactile sensing capsule endoscopy system. While current capsule endoscopy utilizes cameras to diagnose lesions on the surface of the gastrointestinal tract lumen, this proposal uses remote palpation to stimulate a bio-inspired tactile sensing surface that deforms under the impression of both hard and soft raised objects. Current capsule endoscopy utilizes cameras to visually diagnose lesions on the surface of the gastrointestinal tract. Our approach introduces remote palpation by deploying a bio-inspired tactile sensor that deforms when pressed against soft or hard lumps. This can enhance visual inspection of lesions and provide more information about the structure of the lesions. Using classifier systems, we have shown that lumps of different sizes, shapes, and hardnesses can be distinguished in a synthetic test environment. This is a promising early start toward achieving a remote palpation system used inside the GI tract that will utilize the clinician's sense of touch
Rapid manufacturing of color-based hemispherical soft tactile fingertips
Tactile sensing can provide access to information about the contact (i.e.
slippage, surface feature, friction), which is out of reach of vision but
crucial for manipulation. To access this information, a dense measurement of
the deformation of soft fingertips is necessary. Recently, tactile sensors that
rely on a camera looking at a deformable membrane have demonstrated that a
dense measurement of the contact is possible. However, their manufacturing can
be time-consuming and labor-intensive. Here, we show a new design method that
uses multi-color additive manufacturing and silicone casting to efficiently
manufacture soft marker-based tactile sensors that are able to capture with
high-resolution the three-dimensional deformation field at the interface. Each
marker is composed of two superimposed color filters. The subtractive color
mixing encodes the normal deformation of the membrane, and the lateral
deformation is found by centroid detection. With this manufacturing method, we
can reach a density of 400 markers on a 21 mm radius hemisphere, allowing for
regular and dense measurement of the deformation. We calibrated and validated
the approach by finding the curvature of objects with a threefold increase in
accuracy as compared to previous implementations. The results demonstrate a
simple yet effective approach to manufacturing artificial fingertips for
capturing a rich image of the tactile interaction at the location of contact
An Optical Sensor Design: Concurrent Multi-axis Force Measurement and Tactile Perception.
PhD ThesesForce and tactile sensing have experienced a surge of interest over recent decades, as they
convey useful information about the direct physical interaction between the sensor and the external
environment. A robot end effector is a device designed to interact with the environment.
End effectors such as robotic hands and grippers can be used to pick up, place or generally
manipulate objects. There is a clear need to equip such end effectors with appropriate sensing
means to be able to measure tactile and force information. Work to date has explored these two
modalities separately. Tactile sensors have been developed for integration with gripper fingertips
or as skins embedded with the outer side of manipulators, mainly to measure normal force and
its distribution across a surface patch. On the other hand, force sensors have commonly been
integrated with the joints of robotic arms or fingers to measure external multi-axis forces and
torques via the connected links.
We observe that a force sensor cannot measure tactile information, and current tactile sensors
cannot accurately measure force information. This can become a particular issue when
integrating force sensors remotely to measure forces indirectly, especially if the connecting link
is flexible or, generally, difficult to model potentially impacting negatively on the force estimates.
We aim to provide a solution for an integrated sensor capable of measuring tactile and
force information at the point of contact, i.e., on the fingertip of a robot hand or arm.
In this thesis, we explore the idea of integrating the two sensing modalities, tactile and force
sensing, in one sensor housing with the signal acquisition being performed by a single monocular
camera acting as the transducer. The hypothesis is that an integrated force/tactile sensor will
perform in a better way than having these sensor modalities separated. This thesis shows that
an integrated sensor achieves a tactile sensing performance comparable to existing vision-based
tactile sensors and at the same time proves to provide more accurate force sensor information
whilst extending the field of similar vision-based sensors from 3 DoF to 6 DoF. In addition,
the tactile sensing element of our sensor is not affected by the patterns superimposed on to the
flexible element of comparable vision-based sensors used to infer force information. In this
thesis, we have implemented several sensor prototypes; designs and experimental analyses for
each prototype are being provided. The manufactured sensor prototypes prove the validity of the
proposed vision-based dual-modality sensing approach, and the proposed sensing principle and
structure shows high versatility and accuracy, as well as the potential for further miniaturization,
making the proposed concept suitable for integration with standard robot end effectors