The NavChair Assistive Wheelchair Navigation System.

The NavChair Assistive Wheelchair Navigation System [19] is being developed to reduce the cognitive and physical requirements of operating a power wheelchair for people with wide ranging impairments that limit their access to powered mobility. The NavChair is based on a commercial wheelchair system with the addition of a DOS-based computer system, ultrasonic sensors, and an interface module interposed between the joystick and power module of the wheelchair. The obstacle avoidance routines used by the NavChair in conjunction with the ultrasonic sensors are modifications of methods originally used in mobile robotics research. The NavChair currently employs three operating modes: general obstacle avoidance, door passage, and automatic wall following. Results from performance testing of these three operating modes demonstrate their functionality. In additional to advancing the technology of smart wheelchairs, the NavChair has application to the development and testing of "shared control" systems where a human and machine share control of a system and the machine can automatically adapt to human behaviors.     

Assisted Control of Step Passage Motion and Its Comfort Evaluation in Two‐Wheel Wheelchair Systems

Two‐wheel wheelchair systems have been attracting attention because their mobility is better than that of conventional four‐wheel wheelchair systems. However, two‐wheel wheelchair systems must achieve stabilization control in the presence of disturbances caused by modeling error or the road situation, since these systems are underactuated systems similar to the inverted pendulum. In this investigation, step passage motion in two‐wheel wheelchair systems is considered. A reaction torque observer was employed to estimate the pitch angular interaction torque and the pure external wheel disturbance. Repulsive compliance control was employed to determine the optimal pitch angle command to compensate for the center of gravity of the user and to assist the whole step passage motion. Experimental results are evaluated in terms of user comfort by utilizing the ISO 2631‐1 generalized index.     

A low-cost, portable system for the assessment of the postural response of wheelchair users to perturbations.

Maintaining seated postural stability presents a serious challenge to wheelchair users in vehicles, even during normal driving conditions. The purpose of this research was to develop a system for the study of seated postural control in response to perturbations similar to those that might be experienced during vehicle turning and braking. A servo-controlled tilt platform was constructed to provide a low-cost, small, and easily transportable device for generating precise and repeatable perturbations. Tilt platform operation was examined for accuracy and reproducibility of a desired perturbation. Repeatability was high with a mean signal-to-noise ratio (SNR) of 45.4 for a given perturbation measured across 11 subjects. An initial comparison of stability results obtained on the tilt platform and in a vehicle showed a correspondence, although differences were apparent. The tilt platform has been used successfully to assess balance in spinal cord-injured subjects and to test wheelchair securement systems.     

Analysis and improvement of cross‐regulation effect in the primary side‐regulated multi‐output flyback converter

In the multi‐output primary side‐regulated (PSR) flyback converters, cross‐regulation effect denotes the phenomenon that change of load current in either one of the outputs would lead to the output voltage variations in other output terminals. Because the PSR flyback converters are frequently used to provide power supplies in a power system, the steady operation of the power system may be affected. Based on an improved Cantilever model, this paper proposes a thorough analysis on the cross‐regulation effect in the PSR flyback converter. It has been found that the coupling between the output windings and the topology of the output terminal would have significant influence on the cross‐regulation effect. Moreover, a mathematical expression has been derived to calculate the relationship, in the time domain, between the voltages of the output windings in the PSR flyback converter. In the mathematical expression, the leakage inductances in the improved cantilever model are lumped into a matrix R ′. Hence, the winding method and the geometry of the transformer can be optimized to improve the precision of the multi‐output voltages in the PSR flyback converter. A 10‐W PSR flyback prototype with three output terminals is built. Experimental results are given to validate the theoretical analysis. Copyright © 2017 John Wiley & Sons, Ltd.     

Opening doors with assistive technology

Results of the 2001 RESNA student scientific paper and student design competitions are presented. The topics dealt with included: scapula orientation in a virtual wheelchair push; repeatability of determining effective Young's modulus of buttocks soft tissue across multiple subjects; power and control system testing of five different types of power wheelchairs; modification of hybrid III test dummy for use in wheelchair studies; effect of adult-onset diabetes and/or peripheral neuropathy on acceleration threshold detection during horizontal translations; battery tester for people with physical and mental disabilities; design of a modular sensory feedback system to enhance physical education of persons with disabilities; an assistive technology key turning device for independent entryway access; ear-chin strap system for sleep apnea.     

Effects of back cooling with Peltier devices on thermoregulatory responses in a hot environment

To prevent individuals with thermoregulatory dysfunction from becoming hyperthermic in a hot environment, we propose a back‐cooling (BC) system with Peltier devices mounted on a wheelchair backrest. Here, we characterize the changes in thermoregulatory responses induced by BC in order to confirm the feasibility of the proposed system. A cooling experiment in a climate chamber at 33°C with six able‐bodied subjects demonstrated that the amount of sweating and systolic blood pressure were significantly lower in the BC trials than in the no‐cooling trials, providing preliminary evidence that BC can partially replace thermoregulatory responses and reduce the heat burden. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Novel straight and circular road driving control of electric power assisted wheelchair based on fuzzy algorithm

This paper describes a novel straight and circular road driving control scheme for electric power‐assisted wheelchairs. “Electric power‐assisted wheelchair” which assists the driving force by electric motors is expected to be widely used as a mobility support system for elderly people and disabled people, however, the performance of straight and circular road driving must be further improved because the two wheels drive independently. This paper proposes a novel driving control scheme based on fuzzy algorithm to realize stable and reliable driving on straight and circular roads. The suitable assisted torque of the right and left wheels is determined by fuzzy algorithm based on the posture angular velocity of the wheelchair and the human input torque proportion of the right and left wheels. Some experiments on the practical roads show the effectiveness of the proposed control system. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 36–44, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20846     

The theory of instantaneous power in three‐phase four‐wire systems and its applications

This paper discusses “the p–q theory” and “the cross‐vector theory” in three‐phase four‐wire systems, with the focus on similarities and differences between the two theories. They are perfectly identical if no zero‐sequence voltage is included in a three‐phase three‐wire system. However, they are different in definition of the instantaneous active power and instantaneous reactive power in each phase if a zero‐sequence voltage or current is included in a three‐phase four‐wire system. Based on both theory and computer simulation, this paper leads to the following conclusions: An instantaneous reactive‐power compensator without energy storage components can fully compensate for the neutral current even in a three‐phase four‐wire system including a zero‐sequence voltage or current, when a proposed control strategy based on the p–q theory is applied: However, the compensator cannot compensate for the neutral current fully, when a conventional control strategy based on the cross‐vector theory is applied. © 2001 Scripta Technica, Electr Eng Jpn, 135(3): 74–86, 2001     

机器人轮椅用户行为与自主导航动态共享控制方法

机器人轮椅人机交互研究表明长时间采用单一模式交互容易导致用户操作意图误判且稳定性会变差,完全自主模式亦会因用户缺乏控制体验而产生沮丧情绪。针对当前基于人机协作的机器人轮椅交互存在模式间硬切换与缺乏对环境变化的动态调整能力的问题,本文以手势交互控制轮椅为基础,提出一种基于用户行为与自主导航相结合的机器人轮椅动态共享控制方法。首先基于Leap Motion传感器追踪用户掌心坐标,生成用户手势速度指令;其次,基于RPLIDAR A1激光雷达传感器并结合自主导航算法,生成自主导航控制指令;最后基于距离、疲劳及误差等多种约束条件实时更新人-机控制指令权重,实现对机器人轮椅的动态共享控制。实验结果表明,本文所提动态共享控制方法能根据轮椅运行环境与用户操作性能动态调整不同模式间的角色分配,避免了不同模式间的直接硬切换,具有较好的用户体验。     

Proposal of Vibration Control Reducing 2nd Radial Electromagnetic Force

A permanent‐magnet synchronous motor (PMSM) with a concentrated winding generates vibration and noise resulting from the 2nd radial electromagnetic force. In preceding research, it has been shown that the D‐axis negative current reduces the 2nd radial electromagnetic force. In contrast, a relationship between this force and the current has not been clarified. In this paper, it is demonstrated that this force is separated into three forces caused by the D‐axis current, the Q‐axis current, and the flux of the magnet. An equation correlating this force and the current is developed by using a finite element analysis. On the basis of this equation, vibration control is proposed to reduce this force. In addition, this proposed method is verified by experiment.     

Early malfunction diagnosis of industrial process units utilizing online linear trend profiles and real‐time classification

The early detection of potential malfunctions at process systems can significantly reduce downtime and improve their overall operability. In that context, this paper demonstrates the behavior and response, through a comparative analysis, of novel data‐driven diagnosis methods for interdependent time series. The proposed real‐time slope statistic profile method utilizes a self‐adaptive sliding window based on a real‐time classification technique of linear trend profiles of both interdependent time series and internal condition so as to avoid misdetections. The calculation of the linear trend profile is based on a standard parametric linear trend test, and the selection of possible incidents is based on its two‐level cross‐checking. All possible combinations for the calculation of the trend test and cross‐checking are created to explore their efficiency. The proposed methods are tested against real data sets from a chemical process system of the Centre for Research and Technology Hellas/Chemical Process Energy and Resources Institute derived from specific scenarios during nominal operating conditions.     

Controlling mouse pointer position using an infrared head-operated joystick.

This paper describes the motivation for and the design considerations of a low-cost head-operated joystick. The paper briefly summarizes the requirements of head-operated mouse pointer control for people with disabilities before discussing a set of technological approaches that can be used to satisfy these requirements. The paper focuses on the design of a head-operated joystick that uses infrared light emitting diodes (LED's) and photodetectors to determine head position, which is subsequently converted into signals that emulate a Microsoft mouse. There are two significant findings. The first is that, while nonideal device characteristics might appear to make the joystick difficult to use, users naturally compensate for nonlinearities, in a transparent manner, because of visual feedback of mouse pointer position. The second finding, from relatively informal, independent trials, indicates that disabled users prefer a head-operated device that has the characteristics of a joystick (a relative pointing device) to those of a mouse (an absolute pointing device).     

Road loads acting on manual wheelchairs.

A barrier to performing more in-depth analyzes during the wheelchair design process is a lack of dynamic reaction force and moment data, and the instrumentation to collect this data. Instrumentation was developed to collect the dynamic force and moment data. New data collections methodologies and analysis techniques were implemented to facilitate computer-aided-engineering for wheelchair designs. Data were collected during standardized wheelchair fatigue tests, while driving over a simulated road course within a laboratory, and while driving in the community. Seventeen subjects participated in this study. Based upon the three test conditions, a pseudo-statistical distribution of the force and moment data at both a caster and rear wheel was developed. The key parameters describing the distribution and the extremums of the data (minima and maxima) were compared using analysis of variance. The results showed that the force and moment distributions and extreme values were similar for the both sets of human trials (i.e., simulated road course and field trials). However, the standardized testing (i.e., wheelchair fatigue testing) differed from both human trials. The force/moment data gathered during this study are suitable for inputs in finite element analysis and dynamic modeling. Our results suggest that the fatigue tests should be modified to change the magnitude and increase the frequency of the forces and moments imparted on the wheelchair. The data reported from this study can be used to improve wheelchair standards and to facilitate computer-aided-engineer in wheelchair design.     

Resistance formulae of a multipurpose n‐step network and its application in LC network

We consider a multipurpose n‐step network with cross resistors that is a profound problem that has not been resolved before. This network contains a number of different types of resistor network model. This problem is resolved by three steps: First of all, we simplify a complex graphics into a simple equivalent model; next, we use Kirchhoff's laws to analyse the network and establish a nonlinear difference equation; and finally, we construct the method of equivalent transformation to obtain the general solution of the nonlinear difference equation. In this paper, we created a new concept of negative resistance for the needs of the equivalent conversion and obtain two general resistance formulae of a multipurpose ladder network of cross resistors. As applications, several interesting specific results are produced. In particular, an n‐step impedance LC network is discussed. Our method and the results are suitable for the research of complex impedance network as well. Copyright © 2017 John Wiley & Sons, Ltd.     

Lyapunov‐based trajectory tracking controller for a fixed‐wing unmanned aerial vehicle in the presence of wind

This paper addresses the directional control problem of autonomous air vehicles in order to obtain trajectory tracking capabilities when flying in other than calm conditions. The control strategy is designed in the framework of the Lyapunov theory, and adaptive techniques are employed for online wind identification. An application of light fixed‐wing unmanned aerial vehicles that consists in tracking straight‐line paths between geo‐referenced waypoints is first formulated, and the dynamic of the cross track error with respect to such trajectory is further obtained from the lateral airplane equations of motion. The dynamic order of the closed‐loop adaptive system is guaranteed to be minimal by choosing the proper variables so that the tuning functions method could be applied. Several simulations taking into account unknown wind have been performed to analyze the behavior and the robustness of the control scheme. Copyright © 2014 John Wiley & Sons, Ltd.     

Threshold voltage modeling for dual‐metal quadruple‐gate (DMQG) MOSFETs

In this paper, a three‐dimensional (3D) model of threshold voltage is presented for dual‐metal quadruple‐gate metal‐oxide‐semiconductor field effect transistors. The 3D channel potential is obtained by solving 3D Laplace's equation using an isomorphic polynomial function. Threshold voltage is defined as the gate voltage, at which the integrated charge (Q_inv) at the ‘virtual‐cathode’ reaches to a critical charge Q_th. The potential distribution and the threshold voltage are studied with varying the device parameters like gate metal work functions, channel cross‐section, oxide thickness, and gate length ratio. Further, the drain‐induced barrier lowering has also been analyzed for different gate length ratios. The model results are compared with the numerical simulation results obtained from 3D ATLAS device simulation results. Copyright © 2015 John Wiley & Sons, Ltd.     

Enhancement of steady‐state visual evoked potential‐based brain–computer interface systems via a steady‐state motion visual stimulus modality

Steady‐state visual evoked potential (SSVEP)‐based brain–computer interface (BCI) systems are among the most accurate assistive devices for patients with severe disabilities. However, existing visual stimulation patterns lead to eye fatigue, which affects the system performance. Therefore, in this study, we propose two improvements to SSVEP‐based BCI systems. First, we propose a novel visual stimulator that incorporates a visual motion stimulus for the steady‐state visual stimulus to reduce eye fatigue while maintaining the advantages associated with SSVEPs. We also propose two corresponding feature extraction algorithms, i.e. SSVEP detection and visual attention detection, to capture the phenomena of steady‐state motion visual stimulus responses. The accuracy of the test was ∼83.6%. Second, we propose a novel hybrid BCI‐SSVEP system and a motion visual stimulus hybrid BCI system to enhance the SSVEP‐based BCI system during a state of eye fatigue. Participants used the SSVEP system until reaching a fatigued state and then began using a hybrid motion visual stimulus. The accuracy of the proposed system was ∼85.6%. The proposed improvements can be incorporated into practical BCI systems for wheelchair control. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Properties of Space Charge Distributions and Conduction Current in XLPE and LDPE under DC High Electric Field

Space charge behavior and conduction current in polyethylene under dc stress were investigated. One of the reasons for the different breakdown property in cross‐linked polyethylene (XLPE) from that in low‐density polyethylene (LDPE) may be based on the existence of cross‐linking by‐products in XLPE. Furthermore, a thermal history in cross‐linking process for XLPE may also cause of the difference. It is generally accepted that the existence of the cross‐linking by‐products increase the conduction current in XLPE under dc stress. It is also said that an anneal treatment in air atmosphere may affect to the electrical properties under dc stress. Therefore, we investigated the effect of the cross‐linking by‐products and the anneal treatment on space charge behavior and conduction current in polyethylene under dc stress. In our research, it is thought that the increasing dissipation power in XLPE is the cause of the breakdown in it under dc stress. Therefore, to calculate the dissipation power in the bulk of test sample, we measured the space charge distribution and the external circuit current simultaneously. Based on the results, we discussed the reason of the difference of the space charge properties in XLPE and LDPE focusing on the cross‐linking by‐products and the oxidation of the test samples.     

Comparison of three different models to represent the wrist duringwheelchair propulsion

Due to the high incidence of secondary wrist injury among manual wheelchair users, recent emphasis has been placed on the investigation of wheelchair propulsion biomechanics. Accurate representation of wrist activity during wheelchair propulsion may help to elucidate the mechanisms contributing to the development of wrist injuries. Unfortunately, no consensual wrist biomechanical model has been established. In order to determine if different methodologies obtain similar results, this investigation created and compared three different wrist models: 1) a fixed joint center placed between the styloids (midstyloid joint center); 2) a joint center with 2° of freedom computed from de Leva's joint center data; and 3) a floating joint center. Results indicate that wrist flexion and extension angles are highly consistent between models, however, radial and ulnar deviation angles vary considerably. Mean maximum right flexion angles were found to be 3.5°, 2.2°, and 5.0° for the midstyloid, de Leva, and floating joint center models, respectively. Extension angles were 22.3°, 23.6°, and 23.6°, respectively. Mean maximum right radial deviation angles for the midstyloid, de Leva, and floating joint center models were 26.0°, 26.9°, and 45.1°, respectively, and ulnar deviation angles were found to be 30.5°, 38.8°, and 10.2°, respectively. This information is useful when comparing kinematic studies and further supports the need for consensual methodology     

Accurate one‐terminal fault location algorithm based on the principle of short‐circuit calculation

An alternative method to find the line fault distance in a transmission network employing only one‐terminal measured data is presented. The proposed method applies Z_bus for short‐circuit calculation to find the fault location on a transmission line without the necessity to know the fault type a priori. The well‐known drawback of the standard simple‐reactance one‐terminal algorithm, which neglects the effect of fault impedance, will be minimized by estimating the voltage drop at the fault location by employing the Z_bus technique. Accuracy the proposed method is demonstrated using the short‐circuit simulation of the modified IEEE‐14 bus test system on MATLAB/Simulink and the Simpower Toolbox. Compared to the accuracy obtained from the standard one‐terminal algorithm, test results confirm substantially improved accuracy of the proposed method in all cases of the four types of fault categories: single line‐to‐ground fault; double line‐to‐ground fault; line‐to‐line fault; and balance three‐phase fault. While the accuracy has been significantly improved, especially for the case with a relatively high fault impedance, also the simplicity in the involved computation is well preserved when compared to other iterative‐based techniques. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.