Communications Biophysics

Contains reports on nine research projects split into four sections.National Institutes of Health (Grant 5 P01 NS13126)National Institutes of Health (Grant 5 K04 NS00113)National Institutes of Health (Training Grant 5 T32 NS07047)National Institutes of Health (Grant 5 ROl NS11153-03)National Institutes of Health (Fellowship 1 T32 NS07099-01)National Science Foundation (Grant BNS77-16861)National Institutes of Health (Grant 5 ROl NS10916)National Institutes of Health (Grant 5 ROl NS12846)National Science Foundation (Grant BNS77-21751)National Institutes of Health (Grant 1 RO1 NS14092)Health Sciences FundNational Institutes of Health (Grant 2 R01 NS11680)National Institutes of Health (Grant 2 RO1 NS11080)National Institutes of Health (Training Grant 5 T32 GM07301

A data-driven method to reduce excessive contact pressure of hand orthosis using a soft sensor skin

Discomfort under customised hand orthosis has been commonly reported in clinics due to excessive contact pressures, leading to low patient adherence and decreased effectiveness of orthosis. However, the current orthosis adjustment by clinicians to reduce pressures based upon subjective feedback from patients is inefficient and prone to variability. Therefore, a quantitative method to guide orthosis adjustment was proposed here by developing a data-driven method. Firstly, Verbal Protocol Analysis was employed to convert the implicit process of orthosis customisation into working models of clinicians. Relevant data to inform a new solution development to reduce excessive contact pressure were extracted from the working models in terms of time consumption and iterations of tasks. Secondly, a new soft sensor skin with strategically placed sensing units to measure static contact pressures under hand orthoses was developed. Finite element simulations were conducted to reveal the required contact pressure range (0.02 – 0.078 MPa) and the distribution of relatively high pressures in 12 key areas. A new fabrication method was proposed to produce the sensor skin, which was then characterised and tested on the subject. The results show that the sensor unit has a pressure range from 0.01 MPa to 0.1 MPa with the maximum repeatability error of 6.4% at 0.014 MPa, and the maximum measurement error of 8.26% at 0.023 MPa. Thirdly, a new method was proposed to predict contact pressures associated with the moderate level of discomfort at critical spots under hand orthoses. 40 patients were recruited to collect contact pressures under two types of orthoses using the sensor skin, and their discomfort perceptions were measured with a categorical scale. Based on these data, artificial neural networks for five identified critical spots on the hand were built to predict pressure thresholds that clinicians can use to adjust orthoses, thus reducing excessive contact pressures. The neural networks show satisfactory prediction accuracy with R2 values over 0.89 of regression between network outputs and measurements. Collectively, this thesis proposed a novel method for clinicians to adjust orthoses quantitatively and reduce the need for subjective assessment for patients. It provided a platform to further investigate the pressure for patients with other conditions.Open Acces

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