基于模糊控制的轮椅自主跟随与避障系统

为了减轻看护人员的负担,设计并实现了一种基于模糊控制的嵌入式轮椅自主跟随与避障系统。首先利用激光扫描雷达实时探测轮椅周围人员和障碍物的位置,并结合信号强度定位方法,将目标人员准确识别出来。然后将目标人员和障碍物的相对于轮椅的位置偏差作为输入,利用模糊控制方法,建立模糊控制规则,将跟随与避障进行综合决策,控制轮椅的线速度和角速度以实现自主跟随与避障。实验表明轮椅能准确识别出目标人员和干扰人员,对目标人员的跟随效果较好,并能在跟随过程中准确避开障碍物。     

One-hand drive-type power-assisted wheelchair with a direction control device using pneumatic pressure

In this paper, we propose and develop a one-hand drive-type power-assisted wheelchair with a direction control device using pneumatic pressure sensors, for disabled persons who can use only their right or left arm. Compared with a joystick-type wheelchair, the advantages of the proposed wheelchair are that a disabled person can keep the functions of their arm, and can feel a sense that they are driving the wheelchair by the power of their arm. In the case of the wheelchair for disabled persons who can use only their right arm, the right wheel is rotated by the right hand and arm of the person. The left wheel is driven by an electric motor. For traveling in a straight line, the computer controls the motor as the angles of the right and left wheel are the same. When changing the direction of travel, the user uses a direction control device that consists of two vinyl tubes attached to both sides of a hand rim and pneumatic pressure sensors. Traveling experiments on a flat course with obstacles showed the validity of the proposed wheelchair system.     

Wheelchair for physically disabled people with voice,ultrasonic and infrared sensor control

This paper describes a wheelchair for physically disabled people developed within the UMIDAM Project. A dependent-user recognition voice system and ultrasonic and infrared sensor systems has been integrated in this wheelchair. In this way we have obtained a wheelchair which can be driven with using voice commands and with the possibility of avoiding obstacles and downstairs or hole detection. The wheelchair has also been developed to allow autonomous driving (for example, following walls). The project, in which two prototypes have been produced, has been carried out totally in the Electronics Department of the University of Alcalá (Spain). It has been financed by the ONCE. Electronic system configuration, a sensor system, a mechanical model, control (low level control, control by voice commands), voice recognition and autonomous control are considered. The results of the experiments carried out on the two prototypes are also given.     

Design and testing of a low-cost robotic wheelchair prototype

Many people who are mobility impaired are, for a variety of reasons, incapable of using an ordinary wheelchair. In some instances, a power wheelchair also cannot be used, usually because of the difficulty the person has in controlling it (often due to additional disabilities). This paper describes two low-cost robotic wheelchair prototypes that assist the operator of the chair in avoiding obstacles, going to pre-designated places, and maneuvering through doorways and other narrow or crowded areas. These systems can be interfaced to a variety of input devices, and can give the operator as much or as little moment by moment control of the chair as they wish. This paper describes both systems, the evolution from one system to another, and the lessons learned.     

Semi-autonomous Navigation of a Robotic Wheelchair

The present work considers the development of a wheelchair for people with special needs, which is capable of navigating semi-autonomously within its workspace. This system is expected to prove useful to people with impaired mobility and limited fine motor control of the upper extremities. Among the implemented behaviors of this robotic system are the avoidance of obstacles, the motion in the middle of the free space and the following of a moving target specified by the user (e.g., a person walking in front of the wheelchair). The wheelchair is equipped with sonars, which are used for distance measurement in preselected critical directions, and with a panoramic camera with a 360 degree field of view, which is used for following a moving target. After suitably processing the color sequence of the panoramic images using the color histogram of the desired target, the orientation of the target with respect to the wheelchair is determined, while its distance is determined by the sonars. The motion control laws developed for the system use the sensory data and take into account the non-holonomic kinematic constraints of the wheelchair, in order to guarantee certain desired features of the closed-loop system, such as stability. Moreover, they are as simplified as possible to minimize implementation requirements. An experimental prototype has been developed at ICS–FORTH, based on a commercially-available wheelchair. The sensors, the computing power and the electronics needed for the implementation of the navigation behaviors and of the user interfaces (touch screen, voice commands) were developed as add-on modules and integrated with the wheelchair.     

Advanced and Intelligent Control Techniques Applied to the Drive Control and Path Tracking Systems on a Robotic Wheelchair

This paper presents the theoretical support and experimental results of the application of advanced and intelligent control techniques to the drive control and trajectory tracking systems on a robotic wheelchair. The adaptive optimal control of the differential drive helps to improve the automatic guidance system's safety and comfort taking into consideration operating conditions such as load and distribution changes or motion actuator limitations. Furthermore, the incorporation of an optimal controller to minimize location errors and a fuzzy controller to adapt the linear velocity to the characteristics of the trajectory, provide the vehicle with a high degree of intelligence and autonomy, even when faced with obstacles. The global control solution implemented increases the features of the wheelchair for handicapped people, especially for those with a high degree of disability.     

基于激光和单目相机信息融合的智能轮椅避障策略研究

针对智能轮椅使用环境复杂多变,障碍物形状各异,单一传感器无法获得完整的环境信息的问题,提出一种基于激光传感器和单目视觉传感器信息融合的障碍物检测方法。通过单目相机和激光雷达传感器感知智能轮椅周围环境,得到障碍物的形状、距离分布状况等信息;在此基础上提出两种传感器信息的融合策略,建立局部障碍物地图,进一步采用模糊神经网络完成整体避障算法,实现智能轮椅安全、快速避障等功能。实验结果验证了文中所提避障算法的可行性及有效性。     

Speech and sensor in guiding an electric wheelchair

Many people with disabilities do not have the dexterity necessary to control a joystick on an electric wheelchair. Moreover, they have difficulty to avoid obstacles. The aim of this work is to implement a multi-modal system to control the movement of an Electric wheelchair using small vocabulary word recognition system and a set of sensors to detect and avoid obstacles. The methodology adopted is based on grouping a microcontroller with a speech recognition development kit for isolated word from a dependent speaker and a set of sensors. In order to gain in time design, tests have shown that it would be better to choose a speech recognition kit and to adapt it to the application. The text was submitted by the authors in English.     

Design and Implementation of a Multi Sensor Based Brain Computer Interface for a Robotic Wheelchair

In this study, design and implementation of a multi sensor based brain computer interface for disabled and/or elderly people is proposed. Developed system consists of a wheelchair, a high-power motor controller card, a Kinect camera, electromyogram (EMG) and electroencephalogram (EEG) sensors and a computer. The Kinect sensor is installed on the system to provide safe navigation for the system. Depth frames, captured by the Kinect’s infra-red (IR) camera, are processed with a custom image processing algorithm in order to detect obstacles around the wheelchair. A Consumer grade EMG device (Thalmic Labs) was used to obtain eight channels of EMG data. Four different hand movements: Fist, release, waving hand left and right are used for EMG based control of the robotic wheelchair. EMG data is first classified using artificial neural network (ANN), support vector machines and random forest schemes. The class is then decided by a rule-based scheme constructed on the individual outputs of the three classifiers. EEG based control is adopted as an alternative controller for the developed robotic wheelchair. A wireless 14-channels EEG sensor (Emotiv Epoch) is used to acquire real time EEG data. Three different cognitive tasks: Relaxing, math problem solving, text reading are defined for the EEG based control of the system. Subjects were asked to accomplish the relative cognitive task in order to control the wheelchair. During experiments, all subjects were able to control the robotic wheelchair by hand movements and track a pre-determined route with a reasonable accuracy. The results for the EEG based control of the robotic wheelchair are promising though vary depending on user experience.     

轮椅脑控算法研究与实验验证

文章介绍了一种基于BCI实现轮椅运动控制的新型控制方法,研究了一种便携化的脑机接口范式,搭建了适用于普通轮椅的便携化脑机轮椅控制系统;系统根据脑电信号的自身特点,选用Emotiv公司的EPOC无线便携式脑电仪采集脑电电波信号,由单片机控制,实现脑电电波数据的处理,由集成两个无刷电机的制动器执行命令,选用ZD6716V3作为无刷电机的控制器,且每个电机中,都有一个霍尔传感器,提供来自电机的速度反馈信号,以精确获取每个电机的速度参数,并将电机集成在轮椅后轮上,实现轮椅速度和方向的控制;此外,进行了基于脑电识别率的控制方式实验、基于小车的脑控实验以及基于轮椅的脑控实验;实验结果表明脑电信号的准确率可以达到83%,满足实际使用需求。     

A Modular Fuzzy Control Approach for Two-Wheeled Wheelchair

Wheelchairs on two wheels are becoming essential part of life for disabled persons. But designing control strategies for such wheelchairs is a challenging task due to the fact that they are highly nonlinear and unstable systems. The subtle design of the system mimics a double inverted pendulum with three actuators, one for each wheel, and one for chair position. The system starts to work with lifting the front wheels (casters) to the upright position and further with stabilizing in the upright position. The challenge resides in the design and implementation of suitable control strategies for the two-wheeled wheelchair so as to perform comparably similar to a normal four-wheeled wheelchair. A two-level modular fuzzy logic controller is proposed in this paper. A model of the standard wheelchair is also developed as a test and verification platform using Visual Nastran software integrated with Matlab.     

融合眼电及头部姿态的智能轮椅控制

目前已有的轮椅融合控制系统,为肢体残疾人提供了多种操纵策略。多数研究只从提升控制成功率的角度开展,少有从轮椅使用的安全性和舒适性角度开展的研究。为满足特殊群体对轮椅安全性和舒适性的需求,提出了一种新式轮椅控制策略,结合眼电信号和头部姿态变化进行融合控制。头部姿态角度变化适合用于轮椅的实际导向,符合人们的使用习惯;眼电分眨眼和眼动两种,眨眼行为快速且动作细微,适合作为需频繁使用的控制确认信号,而眼动行为不易发生误操作,因此适合用于发送求救信号。设计了一个集成眼电采集和头部姿态检测的护目镜,位于轮椅处的树莓派通过小波变换特征提取和随机森林算法分类,实现不易疲劳、操纵性好且安全的轮椅控制系统。实验表明,该种控制策略能在识别成功率达到92%的基础上,最大程度满足对安全性和舒适性的要求。     

Adaptable navigational assistance for intelligent wheelchairs by means of an implicit personalized user model

Elderly and disabled people can experience considerable difficulties when driving a powered wheelchair, especially if they do not possess the fine steering capacities that are required to perform certain manoeuvres, like avoiding obstacles or docking at tables. In order to help these people, several “intelligent” wheelchairs have been developed in the past, meaning that a powered wheelchair was endowed with the abilities to provide navigational assistance to its user. In such a scenario, control over the wheelchair is shared between the user and the intelligent assistance. The problem of the existing intelligent wheelchairs is, however, that the rules for assistance are hard-coded and by consequence not adaptable to the personal handicap and needs of a specific user. Therefore, this paper proposes a new, more user-centered approach to shared wheelchair control. The presented framework executes two tasks: it continuously estimates the user’s intention and it determines whether the user needs assistance to achieve that intention. An implicit user model is introduced and incorporated in the framework, in order to make the execution of both tasks adaptable to a specific user. This paper presents the proposed framework, along with experimental results in simulation and on a real wheelchair.     

Active tension optimal control for WT wheelchair robot by using a novel control law for holonomic or nonholonomic systems

The characteristics of interaction between WT wheelchair robot and stair environments is analyzed and possible patterns of WT wheelchair robot during the stair-climbing process are summarized, with criteria to determine the pattern of the wheelchair robot proposed. Aiming at the complicated mechanism of WT wheelchair robot with holonomic constraints and combining it with the dynamic programming, namely the Hamilton-Jacobi equation, a new control law called active tension optimal control is presented for holonomic or nonholonomic robotic systems, based on which one can make the wheelchair robot with a holonomic or nonholonomic mechanism track the expected reference input of constraint forces of holonomic or nonholinomic constraints as well as track the expected reference input of the generalized coordinate of each joint. The module STATEFLOW in MATLAB is used to simulate the entire stair-climbing process of WT wheelchair robot, and comparison is made between the output curves of each joint and the tension of the track and the expected reference input curves, which verifies the effectiveness of the proposed control law.     

Traversing step obstacles with manual wheelchairs

In the public transport system, there are sometimes step obstacles, such as curbs, steps, entrance steps of vehicles, edges of lifting platforms, internal steps in vehicles, etc. This paper describes research work carried out in Sweden to specify the heights of step obstacles possible to traverse with a manual wheelchair manoeuvred by an attendant. The work included trials with the subjects manoeuvring two different kinds of wheelchairs, with dummies as occupants, over a step obstacle with adjustable height. It also included trials with a person in the wheelchair. The subjects were 20 healthy persons in the age range of 23-60 years, with no or only little experience of manoeuvring wheelchairs, chosen to represent bus drivers or other helpers. They rated their perceived feeling of effort on a 10-level rating scale with ratio properties. The occupant rated the feeling of comfort and safety in three grades. All trials were recorded using a video-camera. From the video-film, the situations and series of actions of the subjects were analysed and the length of time for each task was measured. The forces needed when traversing step obstacles with a wheelchair were calculated according to the principles of mechanics and processed by a computer for the different principal traversing situations. The results show that for the planning of systems for public transportation, where the passenger can get assistance, a step height of 50 mm is acceptable, and a step height of 100 mm can be acceptable if there is enough room to manoeuvre the wheelchair, so that it is possible to choose the most convenient way to traverse the step. Higher heights should be avoided.     

Optimized obstacle avoidance trajectory generation for a reconfigurable staircase climbing wheelchair

This paper describes the mechanical devices, the control scheme and the trajectory generation of which a new wheelchair prototype capable of climbing staircases is formed. The key feature of the mechanical design is the use of two decoupled mechanisms in each axle, one to negotiate steps, and the other to position the axle with regard to the chair in order to accommodate the overall slope. This design simplifies the control task substantially. Kinematic models are necessary to describe the behavior of the system and to control the actuated degrees of freedom of the wheelchair in order to ensure the passenger’s comfort. The choice of a good control scheme based on a local and a global trajectory planner simplifies control, decreases power consumption, reduces the time invested in traversing the obstacles and maintains passenger comfort throughout all movements. The paper presented here is the natural continuation of a previous work presented in [R. Morales, A. Gonzalez, V. Feliu, P. Pintado, Environment adaptation of a new Staircase climbing wheelchair, Autonomous Robots 23 (2007) 275–292]. After studying the time outs in the staircase climbing/descent process due to configuration changes, we started to increase the capabilities of the trajectory planner in order to reduce the time invested in traversing obstacles. The optimization algorithm is only used in the period of time in which configuration changes are being produced. More specifically, we have used the special properties of the mechanical configuration, the kinematic model and the trajectory planner to develop an improvement in the trajectory planning based on complex notation. The new optimized algorithm solves a nonlinear problem in order to discover an auxiliar center of mass route which is free of obstacles, through the work environment of the wheelchair prototype. Additional properties of the new optimization algorithm are: (a) the resulting analytical expressions are closed (iterative calculation is not necessary); (b) it is easy to implement in the real prototype and (c) it can be executed in real time. Experimental results are reported which show the behavior of the prototype as it climbs a staircase both when using the original trajectory planner and when using the new obstacle avoidance optimization algorithm explained in this paper. The results obtained illustrate a high percentage of time reduction and the maintenance of comfort levels. However, the control prototype becomes more complicated, the power consumption is increased and the comfort level is slightly lower.     

Development of an Intelligent Wheelchair Using Computer Graphics Animation and Simulation

A new robot simulator JC-1 is used as a control software development tool in a project in progress where an intelligent wheelchair for a blind user is being developed. The intelligent wheelchair is planned to be able to fulfill simple symbolic commands like "follow wall" or "follow object" and using the JC-1 simulator an evaluation team which includes e.g. the user, a rehabilitation engineer and a software engineer, can check control algorithms and user interface routines before constructing a real wheelchair prototype. The JC-1 simulator models the environment using simplified boundary- representation where objects, robot sensors and actuators are presented as symbolic objects in the graphics data-base of the simulator. In the JC-1 simulator a robot controller under development controls the motion of the graphical model of the robot while simulator commands or other robot controllers can be used to control the movement of disturbing obstacles. Computer graphics animation and simulation help to find fundamental design errors at an early design stage and as this paper suggests, enable the user of the final product to take part in to the designing process of the robot controller. Benefits and difficulties of using computer graphics simulation in the wheelchair development process are discussed.     

Fault-tolerant control of three-pole active magnetic bearing

Active magnetic bearings have many advantages over conventional bearings due to contactless operation and adjustable force dynamics. However, one of the obstacles associated with these bearings is failure modes, which may result in destructive rotor dynamic behaviour. One of the important failure modes is electric power outage which may be due to failure of power amplifier, coil or electric wiring. In the present work, a fault tolerant controller has been designed for three-pole magnetic bearings to provide unaltered performance in the event of fault occurrence. The controller has been designed by incorporating the nonlinear fuzzy logic control. The present design of fuzzy logic controller is done by reducing the number of rules of its rule base. Simulations have been carried out to test the performance of the controller for different failure conditions. The designed controller is able to stabilize the rotor for large deviations from the origin even in the presence of failure. The controller is found to be robust as it provides satisfactory operation in the presence of uncertainties.     

基于超声波传感器的脑控轮椅避障系统的研究

针对脑控轮椅行驶时因用户脑电信号的不稳定性可能引起碰撞事故发生的现象,提出了一种避障方法,并设计了多路超声波传感器避障系统及避障提示反馈界面;反馈界面上实时显示的提示信息将辅助用户做出有效的避障决策;当用户采用脑电自主控制轮椅运行时,若无法成功避障,则该避障系统立即启动紧急停车功能以避免与障碍物发生碰撞,保证了脑控轮椅用户的人身安全;实验结果表明:当把安全区域临界值、前后及左右紧急停车距离临界值分别设置为500mm、400mm和200mm时,该超声波传感器避障系统稳定性好、实时性强,能够满足脑控轮椅的用户安全导航的需要.