Obstacle Distance Research Articles

Virtual obstacle crossing: Reliability and differences in stroke survivors who prospectively experienced falls or no falls

IntroductionStroke survivors often fall during walking. To reduce fall risk, gait testing and training with avoidance of virtual obstacles is gaining popularity. However, it is unknown whether and how virtual obstacle crossing is associated with fall risk. AimThe present study assessed whether obstacle crossing characteristics are reliable and assessed differences in stroke survivors who prospectively experienced falls or no falls. MethodWe recruited twenty-nine community dwelling chronic stroke survivors. Participants crossed five virtual obstacles with increasing lengths. After a break, the test was repeated to assess test-retest reliability. For each obstacle length and trial, we determined; success rate, leading limb preference, pre and post obstacle distance, margins of stability, toe clearance, and crossing step length and speed. Subsequently, fall incidence was monitored using a fall calendar and monthly phone calls over a six-month period. ResultsTest-retest reliability was poor, but improved with increasing obstacle-length. Twelve participants reported at least one fall. No association of fall incidence with any of the obstacle crossing characteristics was found. DiscussionGiven the absence of height of the virtual obstacles, obstacle avoidance may have been relatively easy, allowing participants to cross obstacles in multiple ways, increasing variability of crossing characteristics and reducing the association with fall risk. ConclusionThese finding cast some doubt on current protocols for testing and training of obstacle avoidance in stroke rehabilitation.

LOCATION DISTRIBUTION OPTIMIZATION OF PHOTOGRAPHING SITES FOR INDOOR PANORAMA MODELING

Abstract. Generally, panoramas image modeling is costly and time-consuming because of photographing continuously to capture enough photos along the routes, especially in complicated indoor environment. Thus, difficulty follows for a wider applications of panoramic image modeling for business. It is indispensable to make a feasible arrangement of panorama sites locations because the locations influence the clarity, coverage and the amount of panoramic images under the condition of certain device. This paper is aim to propose a standard procedure to generate the specific location and total amount of panorama sites in indoor panoramas modeling. Firstly, establish the functional relationship between one panorama site and its objectives. Then, apply the relationship to panorama sites network. We propose the Distance Clarity function (FC and Fe) manifesting the mathematical relationship between panoramas and objectives distance or obstacle distance. The Distance Buffer function (FB) is modified from traditional buffer method to generate the coverage of panorama site. Secondly, transverse every point in possible area to locate possible panorama site, calculate the clarity and coverage synthetically. Finally select as little points as possible to satiate clarity requirement preferentially and then the coverage requirement. In the experiments, detailed parameters of camera lens are given. Still, more experiments parameters need trying out given that relationship between clarity and distance is device dependent. In short, through the function FC, Fe and FB, locations of panorama sites can be generated automatically and accurately.

Parametric optimization of energy and exergy analyses of a novel solar air heater with grey relational analysis

This study is aimed to identify the optimum parameters affecting the energy and exergy efficiencies for a novel design solar air heater (SAH) using the grey relational analysis (GRA). The effect of the different obstacle distances (L), obstacle relief angles (α) and Reynolds number (Re) on the energy and exergy efficiencies of the SAH is investigated. Experiments designed using L9 orthogonal array and optimized using GRA is carried out to determine the optimal design factor levels as the lowest L and α and the highest Re. The parameter contrubition ratios are performed by using ANOVA analysis. Regression analysis (RA) is developed to predict the energy and exergy efficiencies. The confirmation experimental results showed that the data obtained with RA are compatible with the data obtained from experiments.

Characteristics of gasoline–air mixture explosions with different obstacle configurations

The effects of obstacle distance from ignition point, the blockage ratio of obstacle (BR) and the separation distance of obstacles on the characteristics of gasoline–air mixture explosions have been examined by a series of contrast experiments in a semi-confined organic glass pipe (with a square cross section size of 100 mm*100 mm and 1000 mm long, L/D = 10, V = 0.01 m3). It was shown that before the flame fronts propagated to the obstacle, the flame fronts remained regular shape and spread in a low speed, while passed across the obstacle, the flame fronts could be sharply accelerated and became distorted. And it was obvious that the shorter the distance between obstacle and ignition point, the earlier the flame was accelerated, and eventually led to a higher maximum flame speed. Meanwhile, the maximum overpressures and maximum rates of overpressure rise were obtained at Li = 400 mm, and the shorter the distance between the obstacle and ignition point, the shorter the time taken to reach the maximum overpressure. Three kinds of blockage ratios (BR = 36.4%, 49.8%, 71.7%) were tested, and it was found that the maximum flame speeds, maximum overpressures, average rates of overpressure rise and maximum rates of overpressure rise increased with the growth of blockage ratio. It was also discovered that the maximum effect of the combined obstacles on flame acceleration behavior could be obtained at an obstacle separation distance of 1 time to 4 times the length of pipe diameter. And the time taken to obtain the maximum overpressures became shorter with the growth of the obstacle separation distance, while the maximum overpressures and maximum rates of overpressure rise were obtained at an obstacle separation range from Di/D = 3 to 5 (or 300 mm–500 mm).

Designing of optimised rescue robot using fuzzy inference system

The objective of this work is two-fold. First, this work focuses on detection of alive Homo sapiens. Second, it focuses on obstacle detection and collision avoidance. The main aim of this work is to maintain both needs simultaneously. To define the path more precisely, fuzzy set theory is used which tackle with the intermediate values of direction. A Sugeno fuzzy controller algorithm is used which takes three inputs labelled as obstacle position obtained through ultrasonic sensor, obstacle distance through IR sensor and CO2 sensor for finding presence of carbon-dioxide. The work is evaluated on different parameters. As compare to other rescue robots, the number of passes used by our proposed rescue robot is comparatively lesser. The other parameter is wheel computation which is used for measuring the motion. The proposed rescue robot is more flexible while determining its optimising path.

Designing of optimised rescue robot using fuzzy inference system

The objective of this work is two-fold. First, this work focuses on detection of alive Homo sapiens. Second, it focuses on obstacle detection and collision avoidance. The main aim of this work is to maintain both needs simultaneously. To define the path more precisely, fuzzy set theory is used which tackle with the intermediate values of direction. A Sugeno fuzzy controller algorithm is used which takes three inputs labelled as obstacle position obtained through ultrasonic sensor, obstacle distance through IR sensor and CO2 sensor for finding presence of carbon-dioxide. The work is evaluated on different parameters. As compare to other rescue robots, the number of passes used by our proposed rescue robot is comparatively lesser. The other parameter is wheel computation which is used for measuring the motion. The proposed rescue robot is more flexible while determining its optimising path.

大气电场数据误差的影响分析

为研究大气电场数据误差影响，解决大气电场仪数据一致性问题，本文采用Ansoft Maxwell电磁场仿真软件，以不同尺寸的立方体代替地面上凸出的建筑物、高压线、金属杆、树木等，进行了仿真计算和分析。分析表明：地物环境和电场仪安装高度对地面大气电场测量结果的影响较大，使得地面大气电场仪各观测点数据间缺乏可比性。得出电场仪的安装要考虑环境因素，其离障碍物距离不得低于障碍物高度的3倍、宽度的2倍，同时考虑障碍物高度c和宽深比a/b的影响。设备高度和环境的影响，可利用线性拟合对照标准场所测量数据进行修正。 For the study of atmospheric electric field data error, solving the problem of atmospheric electric field instrument data consistency, this paper simulated different size of the cube instead of the real buildings, high voltage wire, metal rods, trees and so on with Ansoft Maxwell electromagnetic field simulation software. Analysis shows that the terrain environment and instrument installation height on the ground have a great influence on the ground atmospheric electric field measurement results, which makes the atmospheric electric field instrument data lack of comparability between each observation point. It is concluded that the installation of the electric field instrument must consider environmental factors, it away from the obstacle distance shall not be less than 3 times of the barrier height and 2 times of the width, considering the influence of the barrier height c and width depth ratio a/b at the same time. The influence of the height and environmental equipment can use linear fitting to correct with reference to the standard measurement data.

Intelligent navigation and control of a mobile robot in static and dynamic environments using hybrid fuzzy architecture

Navigation and obstacle avoidance are one of the most important tasks for any mobile robot. This article proposes the design and implementation of a hybrid fuzzy (H-fuzzy) architecture for intelligent navigation of a mobile robot in the static and dynamic environments. The proposed H-fuzzy architecture is the combination of Takagi-Sugeno type and Mamdani-type fuzzy logics, which helps the mobile robot to reach the goal with obstacle avoidance. The Takagi-Sugeno type fuzzy logic architecture (TFa) is used to assist the robot to reach the goal. The inputs of the Takagi-Sugeno type fuzzy logic architecture are obstacle distances received from the group of sensors, and the output is the turning angle between the robot and the goal. The Mamdani-type fuzzy logic architecture (MFa) is integrated with the TFa to control the motor velocities of the robot. Computer simulations are conducted through MATLAB software and implemented in real time by using Arduino microcontroller based wheeled mobile robot. Moreover, the successful experimental results on the actual mobile robot demonstrate the superiority of the proposed architecture.

PROBABILITAS IJMA’ DI ERA MODERN (IMPLIKASI PERBEDAAN DEFINISI, SYARAT DAN RUKUN TERHADAP KEMUNGKINAN TERJADINYA IJMA’, KEDUDUKAN DAN HUJJAHNYA)

Ijma 'is one of the arguments of Personality' that has the force of argument under the Koran and Hadith, ijma 'is the first proposition after the al-Quran and Hadith that can be used as guidelines in exploring the laws of Personality'. However there are some Muslim community which does not recognize the existence of ijma 'where they are only based on the Quran and al-Hadith, their diligence in itself likely will not be separated from the two text itself. Variation ijma> 'The dimungkinakan for their differences as well as the definition of halal berkaiatan with ijma>' such terms, pillars and so on. From this study we can conclude that: On the issue of ijma> 'happen perbeadaan opinion among the scholars. The differences are due to differences in the definition of the ulama ijma> '. Selaian, differences in the terms and the pillars of the proposed menajadi importance in understanding ijma> '. The most fundamental thing ijma’ is a difference whether the agreement that all or the majority of scholars only. In this case the author is more inclined to the latter opinion. Both now it is not improbable occurrence of Ijma> '. Although it uses the most stringent requirements. Due to technological advances, create obstacles distance between the scholars are not a barrier anymore. However, the difficulty is that everyone has a different opinion in accordance with the experience and knowledge he possessed.

The effects of obstacle proximity on aperture crossing behaviours.

Affordance theory and behavioural dynamics have been used as theoretical constructs to explain how individuals interact with the environment in order to avoid obstacles. Features of obstacle distance and multiple obstacle avoidance have been discussed in unique studies, yet the interactions of these environmental features have yet to be explored. The purpose of this study was to asses the effects of obstacle distance, relative to the goal, on aperture crossing strategies. Kinematics and gaze behaviours were assessed in a cohort of female young adults (N=24, 21.3±1.4years). Results identified that participants chose to navigate through gaps of 1.3× shoulder width or greater, regardless of obstacle distance. However, safety margin in the anterior-posterior direction was found to increase with increased obstacle distance, suggesting unique environmental affordances for each obstacle distance. Therefore, although decision making on whether to navigate through, or around, the aperture appears to be unaffected by obstacle location, specific environmental features result in unique kinematic behaviours. Such behaviours fit within, and add merit to, the tenets of both affordance theory and behavioural dynamics.

Robust mobile robot localization based on a security laser: an industry case study

Purpose This paper aims to address a mobile robot localization system that avoids using a dedicated laser scanner, making it possible to reduce implementation costs and the robot’s size. The system has enough precision and robustness to meet the requirements of industrial environments. Design/methodology/approach Using an algorithm for artificial beacon detection combined with a Kalman Filter and an outlier rejection method, it was possible to enhance the precision and robustness of the overall localization system. Findings Usually, industrial automatic guide vehicles feature two kinds of lasers: one for navigation placed on top of the robot and another for obstacle detection (security lasers). Recently, security lasers extended their output data with obstacle distance (contours) and reflectivity. These new features made it possible to develop a novel localization system based on a security laser. Research limitations/implications Once the proposed methodology is completely validated, in the future, a scheme for global localization and failure detection should be addressed. Practical implications This paper presents a comparison between the presented approach and a commercial localization system for industry. The proposed algorithms were tested in an industrial application under realistic working conditions. Social implications The presented methodology represents a gain in the effective cost of the mobile robot platform, as it discards the need for a dedicated laser for localization purposes. Originality/value This paper presents a novel approach that benefits from the presence of a security laser on mobile robots (mandatory sensor when considering industrial applications), using it simultaneously with other sensors, not only to guarantee safety conditions during operation but also to locate the robot in the environment. This paper is also valuable because of the comparison made with a commercialized system, as well as the tests conducted in real industrial environments, which prove that the approach presented is suitable for working under these demanding conditions.

Autonomous mobile robot navigation in cluttered environment using hybrid Takagi-Sugeno fuzzy model and simulated annealing algorithm controller

Purpose This paper aims to design a Takagi–Sugeno fuzzy model with a simulated annealing hybrid algorithm (fuzzy-SAA) that was implemented for mobile robot navigation and obstacle avoidance in a cluttered environment. Design/methodology/approach The SAA is used to optimize the output parameters of the fuzzy controller. The ultrasonic range finder sensor and sharp infrared range sensor are used for calculating the different obstacle distances, such as front, right and left obstacle distance, for selecting the suitable steering angle control command in the environment. Findings The simulation and experimental results show the proposed method is feasible and valid for a wheeled mobile robot moving in a cluttered environment. Originality/value The developed fuzzy-SAA hybrid algorithm provides better results (in terms of navigation path length and time) as compared to previous works, which verifies the effectiveness and efficiency of the developed hybrid algorithm.

Anticipatory Postural Control of Stability during Gait Initiation Over Obstacles of Different Height and Distance Made Under Reaction-Time and Self-Initiated Instructions.

Despite the abundant literature on obstacle crossing in humans, the question of how the central nervous system (CNS) controls postural stability during gait initiation with the goal to clear an obstacle remains unclear. Stabilizing features of gait initiation include anticipatory postural adjustments (APAs) and lateral swing foot placement. To answer the above question, 14 participants initiated gait as fast as possible in three conditions of obstacle height, three conditions of obstacle distance and one obstacle-free (control) condition. Each of these conditions was performed with two levels of temporal pressure: reaction-time (high-pressure) and self-initiated (low-pressure) movements. A mechanical model of the body falling laterally under the influence of gravity and submitted to an elastic restoring force is proposed to assess the effect of initial (foot-off) center-of-mass position and velocity (or “initial center-of-mass set”) on the stability at foot-contact. Results showed that the anticipatory peak of mediolateral (ML) center-of-pressure shift, the initial ML center-of-mass velocity and the duration of the swing phase, of gait initiation increased with obstacle height, but not with obstacle distance. These results suggest that ML APAs are scaled with swing duration in order to maintain an equivalent stability across experimental conditions. This statement is strengthened by the results obtained with the mechanical model, which showed how stability would be degraded if there was no adaptation of the initial center-of-mass set to swing duration. The anteroposterior (AP) component of APAs varied also according to obstacle height and distance, but in an opposite way to the ML component. Indeed, results showed that the anticipatory peak of backward center-of-pressure shift and the initial forward center-of-mass set decreased with obstacle height, probably in order to limit the risk to trip over the obstacle, while the forward center-of-mass velocity at foot-off increased with obstacle distance, allowing a further step to be taken. These effects of obstacle height and distance were globally similar under low and high-temporal pressure. Collectively, these findings imply that the CNS is able to predict the potential instability elicited by the obstacle clearance and that it scales the spatiotemporal parameters of APAs accordingly.

Fast Obstacle Distance Estimation using Laser Line Imaging Technique for Smart Wheelchair

This paper presents an approach of obstacle distance estimation for smart wheelchair. A smart wheelchair was equipped with a camera and a laser line. The camera was used to capture an image from the environment in order to sense the pathway condition. The laser line was used in combination with camera to recognize an obstacle in the pathway based on the shape of laser line image in certain angle. A blob method detection was then applied on the laser line image to separate and recognize the pattern of the detected obstacles. The laser line projector and camera which was mounted in fixed-certain position ensured a fixed relation between blobs-gap and obstacle-to-wheelchair distance. A simple linear regression from 16 obtained data was used to respresent this relation as the estimated obstacle distance. As a result, the average error between the estimation and the actual distance was 1.25 cm from 7 data testing experiments. Therefore, the experiment results show that the proposed method was able to estimate the distance between wheelchair and the obstacle.

Fast Obstacle Distance Estimation using Laser Line Imaging Technique for Smart Wheelchair

This paper presents an approach of obstacle distance estimation for smart wheelchair. A smart wheelchair was equipped with a camera and a laser line. The camera was used to capture an image from the environment in order to sense the pathway condition. The laser line was used in combination with camera to recognize an obstacle in the pathway based on the shape of laser line image in certain angle. A blob method detection was then applied on the laser line image to separate and recognize the pattern of the detected obstacles. The laser line projector and camera which was mounted in fixed-certain position ensured a fixed relation between blobs-gap and obstacle-to-wheelchair distance. A simple linear regression from 16 obtained data was used to respresent this relation as the estimated obstacle distance. As a result, the average error between the estimation and the actual distance was 1.25 cm from 7 data testing experiments. Therefore, the experiment results show that the proposed method was able to estimate the distance between wheelchair and the obstacle.

BLINDNESS ELECTRONIC ASSISTANT SYSTEM

Electronic assistant system for blind people is introduced which is capable of detecting obstacles around the blind person allowing him to walk, deal and react with the surrounding environment independently. Ultrasound and IR distance sensors are used in this development to detect the distance of obstacles surrounding the blind person according to the sensors distribution. The system here will convert the sensor signal to vocal signal and vibration to be accessible for blind person hearing nearby obstacles as high frequency beep and further obstacles as low frequency beep, Vibration motors will be set in the two sides of the blind person indication for left or right obstacles. This study shows a design and implementation of assistant system which will be helpful for blind persons who always suffer from being dependent on someone for help or doing their stuff.

Budgerigar flight in a varying environment: flight at distinct speeds?

How do flying birds respond to changing environments? The behaviour of budgerigars, Melopsittacus undulatus, was filmed as they flew through a tapered tunnel. Unlike flying insects-which vary their speed progressively and continuously by holding constant the optic flow induced by the walls-the birds showed a tendency to fly at only two distinct, fixed speeds. They switched between a high speed in the wider section of the tunnel, and a low speed in the narrower section. The transition between the two speeds was abrupt, and anticipatory. The high speed was close to the energy-efficient, outdoor cruising speed for these birds, while the low speed was approximately half this value. This is the first observation of the existence of two distinct, preferred flight speeds in birds. A dual-speed flight strategy may be beneficial for birds that fly in varying environments, with the high speed set at an energy-efficient value for flight through open spaces, and the low speed suited to safe manoeuvring in a cluttered environment. The constancy of flight speed within each regime enables the distances of obstacles and landmarks to be directly calibrated in terms of optic flow, thus facilitating simple and efficient guidance of flight through changing environments.

Mobile robot navigation in unknown static environments using ANFIS controller

Summary Navigation and obstacle avoidance are the most important task for any mobile robots. This article presents the Adaptive Neuro-Fuzzy Inference System (ANFIS) controller for mobile robot navigation and obstacle avoidance in the unknown static environments. The different sensors such as ultrasonic range finder sensor and sharp infrared range sensor are used to detect the forward obstacles in the environments. The inputs of the ANFIS controller are obstacle distances obtained from the sensors, and the controller output is a robot steering angle. The primary objective of the present work is to use ANFIS controller to guide the mobile robot in the given environments. Computer simulations are conducted through MATLAB software and implemented in real time by using C/C++ language running Arduino microcontroller based mobile robot. Moreover, the successful experimental results on the actual mobile robot demonstrate the effectiveness and efficiency of the proposed controller.

A gradient-based path optimization method for motion planning

Most algorithms in probabilistic sampling-based path planning compute collision-free paths made of straight line segments lying in the configuration space. Due to the randomness of sampling, the paths make detours that need to be optimized. The contribution of this paper is to propose a basic gradient-based algorithm that transforms a polygonal collision-free path into a shorter one. While requiring only collision checking, and not any time-consuming obstacle distance computation nor geometry simplification, we constrain only part of the configuration variables that may cause a collision, and not entire configurations. Thus, parasite motions that are not useful for the problem resolution are reduced without any assumption. Experimental results include navigation and manipulation tasks, eg a manipulator arm-filling boxes and a PR2 robot working in a kitchen environment. Comparisons with a random shortcut optimizer and a partial shortcut have also been studied.

Design of capacitive micromachined ultrasonic transducer (CMUT) linear array for underwater imaging

Purpose – The purpose of this paper was to develop a novel capacitive micromachined ultrasonic transducer (CMUT) reception and transmission linear array for underwater imaging at 400 kHz. Compared with traditional CMUTs, the developed transducer array offers higher electromechanical coupling coefficient and higher directivity performance. Design/methodology/approach – The configuration of the newly developed CMUT reception and transmission array was determined by the authors’ previous research into new element structures with patterned top electrodes and into directivity simulation analysis. Using the Si-Silicon on insulator (Si-SOI) bonding technique and the principle of acoustic impedance matching, the CMUT array was fabricated and packaged. In addition, underwater imaging system design and testing based on the packaged CMUT 1 × 16 array were completed. Findings – The simulation results showed that the optimized CMUT array configuration was selected. Furthermore, the designed configuration of the CMUT 1 × 16 linear array was good enough to guarantee high angular resolution. The underwater experiments were conducted to demonstrate that this CMUT array can be of great benefit in imaging applications. Practical implications – Based on our research, the CMUT linear array has good directivity and good impedance matching with water and can be used for obstacle avoidance, distance measurement and imaging underwater. Originality/value – This research provides a basis for CMUT directivity theory and array design. CMUT array presented in this paper has good directivity and has been applied in the underwater imaging, resulting in a huge market potential in underwater detection systems.