A smart wheelchair system using a combination of stereoscopic and spherical vision cameras

University of Technology, Sydney. Faculty of Engineering and Information Technology.Reports have shown growing numbers of people who fall into the categories of the elderly or those living with some form of disability. Physical and functional impairments are broad-ranging across these groups and the causes are numerous, including strokes, spinal cord injury, spina bifida, multiple sclerosis, muscular dystrophy, and various degenerative disorders. Rehabilitation technologies are a solution to many of these impairments and aim to improve the quality of life for the people who require them. Smart wheelchair developments, in particular, have the purpose of assisting those with mobility disabilities. Providing independence in mobility can have many significant benefits to the users in their daily lives, including improved physical, cognitive, confidence, communication, and social skills. Unfortunately for many, particularly those with tetraplegia (partial or total loss of functionality through illness or injury to all four limbs and torso), there is a serious lack of options available for adequately and safely controlling mobility devices such as wheelchairs. There are few options for hands-free controlling wheelchairs, and furthermore, there are no accessible options for intelligent assistance from the wheelchair to make hands-free control easy and safe. This is a serious issue since the limited hands-free control options available can be difficult to use, resulting in many accidents. There are also new control technology devices emerging in research, such as brain-computer interfaces (BCIs), which could potentially provide an adequate means of control for many people who cannot use currently commercial options, but require intelligent assistance from the wheelchair to make use of such a system safe. In this thesis, the design and development of a new smart wheelchair, named TIM, is introduced to address these issues. The TIM smart wheelchair was created with the intention of providing intelligent assistance during navigation for any hands-free control technology, both currently commercial and new devices produced in research. This aims to vastly improve the options available to the people who are in need of such smart wheelchair developments. A method of utilising stereoscopic cameras for adaptive, real-time vision mapping is presented in this thesis, as cameras are increasingly becoming a more accessible and inexpensive form of artificial sensor. The mapping process in this method involves acquisition from the left and right stereo pair of cameras, which then undergo a range of image pre-processing techniques before being stereo-processed, which includes matching and correlation algorithms, to produce a disparity image. This disparity image contains depth information about the scene, which is then converted into a 3-dimensional (3D) point map, placing all mapped pixels of the environment, and features within, into a 3D plane. Unnecessary information, such as the floor and everything above the maximum height of the TIM smart wheelchair, is removed and the remaining data extracted into a 2-dimensional (2D) bird’s eye view environment map. This mapping representation assists the wheelchair in the later steps of making intelligent navigational decisions based on the relative placement of objects in the environment. Wheel encoders on the drive wheels are also acquired during operation, and odometry change calculations are performed to facilitate the ability of the system to ‘remember’ mapped object points that have passed outside the vision range. This is performed frequently to construct a real-time environment map, and to remember the placement of objects that have moved out of the range of vision, in order to further avoid collisions. This is particularly useful for static environments and creating maps of the static object placements within. A wheel parameter correction process was also employed to increase the accuracy of this mapping process and successfully reduce the errors associated with drive wheel specifications, which in turn can affect the mapping process based on the wheel encoder information. Correction of these parameters helped optimise the ‘memory mapping’ process and reduce skewing and accumulative errors in the maps. A process for intelligent stereo processing parameter selection was designed, as the quality of disparity images, and hence the quality of environmental-mapping, is heavily dependent on the stereo processing parameters, which may work well when set for one environment but produce problems in another. The differences that affected performance between environments were found to mostly be the lighting conditions which resulted from the varying types of environments. As such, this proposed method involves classifying environmental categories in real-time, based on image data available, and adapting the parameters accordingly. The environment types were separated into four categories to account for most encountered environmental situations, being 1) ‘General Illumination Contrast’, 2) ‘Extreme Illumination Contrast’, 3) ‘Consistent Dark’, and 4) ‘Consistent Bright’. The proposed method successfully allowed classification in real-time of the environment categories and adaptation of the stereo processing parameters in accordance, producing a system that can change its settings ‘on the fly’ to suit the environment the wheelchair is navigating through. Limited vision and trouble with dynamic objects were found to be downfalls with the stereoscopic vision, so to address these, methods of utilising a spherical vision camera system were introduced for obstacle detection over a wide vision range. Spherical vision is an extension of monoscopic cameras, producing 360º of panoramic vision. A strategy to utilise these panoramic images is presented, in which the images are separated into segments and ‘Traffic Light’ zones. The segments display different areas of the image representing the allocated areas around the wheelchair. The ‘Traffic Light’ zones within the segments are separated into three categories: 1) Red, meaning an obstruction is present around the wheelchair, 2) Yellow, indicating to take caution as an object is nearby, and 3) Green, meaning there are no objects close to the wheelchair in this segment. Image processing techniques have been assembled as a pre-processing strategy, and neural networks are used for intelligent classification of the segmented images into the zone categories. This method provides a wider range of vision than the stereoscopic cameras alone, and also takes into account the issue of detecting dynamic obstacles, such as people moving around. A unique combination of the stereoscopic cameras and the spherical vision cameras is then introduced. This combination and system configuration is biologically inspired by the equine vision system. Horses inherently have a large vision range, which includes a wide monocular vision range around and a binocular vision overlap ahead of the horse. In accordance with this effective vision system, the camera configuration on the TIM smart wheelchair was modelled similarly and advanced software integration strategies then followed. A method for advanced real-time obstacle avoidance is presented, which utilises algorithms in research, such as Vector Field Histogram (VFH) and Vector Polar Histogram (VPH) methods, and adapts them for use with the specified camera configuration. Further improvement upon the algorithms for this application provides safer obstacle avoidance during navigation in unknown environments, with an added emphasis on making automated navigational decisions towards areas with more available free space. Speed and manner of obstacle avoidance is dependent upon the placement spread of objects in an environment and how close they are to the wheelchair during navigation. Finally, the combination and integration of the automated guidance and obstacle avoidance capabilities of the wheelchair with hands-free control technologies are introduced. The aim of the TIM smart wheelchair system was to effectively provide safe navigation with automated obstacle avoidance in a manner that ultimately executes the user’s intentions for travel. As such, a head-movement control (HMC) device and a brain-computer interface (BCI) device are both separately integrated with the TIM smart wheelchair, providing a display of two new options for hands-free control. Experimental studies were conducted using these two control devices separately, to assess the performance of the TIM smart wheelchair, as well as its ability to carry out user’s navigational intentions safely and effectively. Eight able-bodied participants trialled the system, including four male and four female, with ages ranging from 21 to 56 years old. All of these able-bodied participants have not previously had any experience operating a wheelchair. In addition, two male tetraplegic (C-6 to C-7) participants also completed the experimental study, aged 20 and 33. Both tetraplegic participants are wheelchair users, so these experiments were of great importance. The same tasks applied to all, and included navigating obstacle courses with the use of the head-movement control system and the brain-computer interface for control. Experiment runs were conducted for each control system with automated navigational guidance assistance from TIM, and repeated for some capable participants without the assistance from TIM. This process was also conducted in two types of obstacle courses, being 1) a ‘Static Course’ and 2) a ‘Dynamic Course’, requiring different types of challenges in obstacle avoidance. This provided results to assess the performance and safety of the TIM smart wheelchair in a range of environments and situations. Evaluation of the results displayed the feasibility and effectiveness of the developed TIM smart wheelchair system. This system, once equipped with a unique camera configuration and reliable obstacle avoidance strategies, was able to successfully allow users to control the wheelchair with research-produced hands-free interface devices and effectively navigate safely through challenging environments. The TIM smart wheelchair system is able to adapt to people with various types and levels of physical impairment, and ultimately provide ease-of-use as well as safety during navigation

Bayesian recursive algorithm for width estimation of freespace for a power wheelchair using stereoscopic cameras.

This paper is concerned with the estimation of freespace based on a Bayesian recursive (BR) algorithm for an autonomous wheelchair using stereoscopic cameras by severely disabled people. A stereo disparity map processed from both the left and right camera images is constructed to generate a 3D point map through a geometric projection algorithm. This is then converted to a 2D distance map for the purpose of freespace estimation. The width of freespace is estimated using a BR algorithm based on uncertainty information and control data. Given the probabilities of this width computed, a possible movement decision is then made for the mobile wheelchair. Experimental results obtained in an indoor environment show the effectiveness of this estimation algorithm

Experimental study on a smart wheelchair system using a combination of stereoscopic and spherical vision

This paper is concerned with the experimental study performance of a smart wheelchair system named TIM (Thought-controlled Intelligent Machine), which uses a unique camera configuration for vision. Included in this configuration are stereoscopic cameras for 3-Dimensional (3D) depth perception and mapping ahead of the wheelchair, and a spherical camera system for 360-degrees of monocular vision. The camera combination provides obstacle detection and mapping in unknown environments during real-time autonomous navigation of the wheelchair. With the integration of hands-free wheelchair control technology, designed as control methods for people with severe physical disability, the smart wheelchair system can assist the user with automated guidance during navigation. An experimental study on this system was conducted with a total of 10 participants, consisting of 8 able-bodied subjects and 2 tetraplegic (C-6 to C-7) subjects. The hands-free control technologies utilized for this testing were a head-movement controller (HMC) and a brain-computer interface (BCI). The results showed the assistance of TIM's automated guidance system had a statistically significant reduction effect (p-value = 0.000533) on the completion times of the obstacle course presented in the experimental study, as compared to the test runs conducted without the assistance of TIM. © 2013 IEEE

Semi-autonomous wheelchair developed using a unique camera system configuration biologically inspired by equine vision

This paper is concerned with the design and development of a semi-autonomous wheelchair system using cameras in a system configuration modeled on the vision system of a horse. This new camera configuration utilizes stereoscopic vision for 3-Dimensional (3D) depth perception and mapping ahead of the wheelchair, combined with a spherical camera system for 360-degrees of monocular vision. This unique combination allows for static components of an unknown environment to be mapped and any surrounding dynamic obstacles to be detected, during real-time autonomous navigation, minimizing blind-spots and preventing accidental collisions with people or obstacles. This novel vision system combined with shared control strategies provides intelligent assistive guidance during wheelchair navigation and can accompany any hands-free wheelchair control technology. Leading up to experimental trials with patients at the Royal Rehabilitation Centre (RRC) in Ryde, results have displayed the effectiveness of this system to assist the user in navigating safely within the RRC whilst avoiding potential collisions. © 2011 IEEE

Physicians, Primary Caregivers and Topical Repellent: All Under-Utilised Resources in Stopping Dengue Virus Transmission in Affected Households

BACKGROUND: Primary health care facilities frequently manage dengue cases on an ambulatory basis for the duration of the patient’s illness. There is a great opportunity for specific messaging, aimed to reduce dengue virus (DENV) transmission in and around the home, to be directly targeted toward this high-risk ambulatory patient group, as part of an integrated approach to dengue management. The extent however, to which physicians understand, and can themselves effectively communicate strategies to stop focal DENV transmission around an ambulatory dengue case is unknown; the matter of patient comprehension and recollection then ensues. In addition, the effectiveness of N,N-diethyl-3-methylbenzamide (DEET)-based insect repellent in protecting dengue patients from Aedes aegypti mosquitoes’ bites has not been investigated. METHODOLOGY: A knowledge, attitude and practice (KAP) survey, focusing on the mechanisms of DENV transmission and prevention, was performed using semi-structured questionnaires. This survey was targeted towards the patients and family members providing supportive care, and physicians routinely involved in dengue patient management in Southern Vietnam. An additional clinical observational study was conducted to measure the efficacy of a widely-used 13% DEET-based insect repellent to repel Ae. aegypti mosquitoes from the forearms of dengue cases and matched healthy controls. PRINCIPAL FINDINGS: Among both the physician (n = 50) and patient (n = 49) groups there were several respondents lacking a coherent understanding of DENV transmission, leading to some inappropriate attitudes and inadequate acute preventive practices in the household. The application of insect repellent to protect patients and their relatives from mosquito bites was frequently recommended by majority of physicians (78%) participating in the survey. Nevertheless, our tested topical application of 13% DEET conferred only ~1hr median protection time from Ae. aegypti landing. This is notably shorter than that advertised on the manufacturer’s label. No differences in landing time between febrile dengue cases or matched healthy controls (n = 19 experiments) were observed. CONCLUSIONS/SIGNIFICANCE: Our study identifies missed opportunities for primary care physicians to improve public health through communication of strategies that could prevent focal dengue transmission in and around a case household. We advocate better access to more efficient communication methods for physicians and auxilliary health workers, supporting to educate those at high risk of DENV transmission. Our empirical testing of a widely-available 13% DEET-based repellent was limited in its protective efficacy against Ae. aegypti mosquito bites, and therefore DENV transmission, suggesting more frequent application is necessary to be beneficial

Signals 1, 2 and B cell fate or: Where, when and for how long?

Diverse B cell responses are important for generating antibody‐mediated protection against highly variable pathogens. While some antigens can trigger T‐independent B cell proliferation and short‐term antibody production, development of long‐term humoral immunity requires T‐dependent B cell responses. The “two‐signal” model of B cell activation has long been invoked to explain alternate B cell recruitment into immune response to foreign antigens vs. induction of tolerance to self‐antigens. However, a number of other factors appear to influence the fate of mature B cells responding to antigen in vivo. In this review, we will discuss how various spatiotemporal scenarios of antigen access into secondary lymphoid organs, antigen valency and cellular environment of antigen acquisition by B cells, duration of B cell access to antigen and the timing of T cell help may affect follicular B cell fate, including death, survival, anergy, and recruitment into T‐dependent responses. We will also highlight unresolved questions related to B cell activation and tolerance in vivo that may have important implications for vaccine development and autoimmunity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156186/2/imr12865.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156186/1/imr12865_am.pd

Public health responses to influenza in care homes: a questionnaire-based study of local Health Protection Units.

BACKGROUND: Influenza virus infection poses a major threat to the elderly people in residential care. We sought to describe the extent to which local public health services in England were positioned to detect and respond effectively to influenza-like illness (ILI) in nursing homes. METHODS: A questionnaire-based survey was conducted in all 34 Health Protection Units (HPUs) regarding the 2004-05 influenza season. RESULTS: Of the 20 responses, half reported 24 outbreaks of ILI in care homes. The mean resident population attack rate was 41% (range 15-79) with 31 deaths. Staff ILI occurred in 23 of 24 outbreaks. Seven of 20 HPUs stated that a local policy for the management of ILI in nursing homes was in place, with only four specifying the use of neuraminidase inhibitors (NI) for treatment of cases and prophylaxis of residents. In the outbreaks reported, NIs were used for treatment and prophylaxis, respectively, in only 46 and 54% of instances. CONCLUSIONS: Given the availability of effective interventions for treatment and prophylaxis, there is potential to prevent substantial morbidity and mortality from influenza in at-risk populations. This study suggests that challenges remain in the effective response to influenza outbreaks in care homes and that there are wide variations in practice at local level

A new approach for concurrently improving performance of South Korean food waste valorization and renewable energy recovery via dry anaerobic digestion under mesophilic and thermophilic conditions

© 2017 Elsevier Ltd Dry semicontinuous anaerobic digestion (AD) of South Korean food waste (FW) under four solid loading rates (SLRs) (2.30–9.21 kg total solids (TS)/m3 day) and at a fixed TS content was compared between two digesters, one each under mesophilic and thermophilic conditions. Biogas production and organic matter reduction in both digesters followed similar trends, increasing with rising SLR. Inhibitor (intermediate products of the anaerobic fermentation process) effects on the digesters’ performance were not observed under the studied conditions. In all cases tested, the digesters’ best performance was achieved at the SLR of 9.21 kg TS/m3 day, with 74.02% and 80.98% reduction of volatile solids (VS), 0.87 and 0.90 m3 biogas/kg VSremoved, and 0.65 (65% CH4) and 0.73 (60.02% CH4) m3 biogas/kg VSfed, under mesophilic and thermophilic conditions, respectively. Thermophilic dry AD is recommended for FW treatment in South Korea because it is more efficient and has higher energy recovery potential when compared to mesophilic dry AD

An explicit hybridizable discontinuous Galerkin method for the 3D time-domain Maxwell equations

International audienceWe present an explicit hybridizable discontinuous Galerkin (HDG) method for numerically solving the system of three-dimensional (3D) time-domain Maxwell equations. The method is fully explicit similarly to classical so-called DGTD (Dis-continuous Galerkin Time-Domain) methods, is also high-order accurate in both space and time and can be seen as a generalization of the classical DGTD scheme based on upwind fluxes. We provide numerical results aiming at assessing its numerical convergence properties by considering a model problem and we present preliminary results of the superconvergence property on the H curl norm

Effects of seasonal and pandemic influenza on health-related quality of life, work and school absence in England: results from the Flu Watch cohort study

BACKGROUND: Estimates of health-related quality of life (HRQoL) and work/school absences for influenza are typically based on medically-attended cases or those meeting influenza-like-illness (ILI) case definitions, and thus biased towards severe disease. Although community influenza cases are more common, estimates of their effects on HRQoL and absences are limited. OBJECTIVES: To measure Quality-Adjusted Life Days and Years (QALDs and QALYs) lost and work/school absences among community cases of acute respiratory infections (ARI), ILI and influenza A and B and to estimate community burden of QALY loss and absences from influenza. PATIENTS/ METHODS: Flu Watch was a community cohort in England from 2006-2011. Participants were followed-up weekly. During respiratory illness they prospectively recorded daily symptoms, work/school absences and EQ-5D-3L data and submitted nasal swabs for RT-PCR influenza testing. RESULTS: Average QALD lost was 0.26, 0.93, 1.61 and 1.84 for ARI, ILI, H1N1pdm09 and influenza B cases respectively. 40% of influenza A cases and 24% of influenza B cases took time off work/school with an average duration of 3.6 days and 2.4 days respectively. In England, community influenza cases lost 24,300 QALYs in 2010/11 and had an estimated 2.9 million absences per season based on data from 2006/07 - 2009/10. CONCLUSIONS: Our QALDs and QALYs lost and work and school absence estimates are lower than previous estimates because we focus on community cases, most of which are mild, may not meet ILI definitions and do not result in healthcare consultations. Nevertheless, they contribute a substantial loss of HRQoL on a population level. This article is protected by copyright. All rights reserved