Design and control of JAIST active robotic walker

This paper presents the design and control of a novel assistive robotic walker that we call “JAIST active robotic walker (JARoW)”. JARoW is developed to provide potential users with sufficient ambulatory capability in an efficient, cost-effective way. Specifically, our focus is placed on how to allow easier maneuverability by creating a natural interface between the user and JARoW. For the purpose, we develop a rotating infrared sensor to detect the user’s lower limb movement. The implementation details of the JARoW control algorithms based on the sensor measurements are explained, and the effectiveness of the proposed algorithms is verified through experiments. Our results confirmed that JARoW can autonomously adjust its motion direction and velocity according to the user’s walking behavior without requiring any additional user effort.     

HMM-based state classification of a user with a walking support system using visual PCA features

The improvement of safety and dependability in systems that physically interact with humans requires investigation with respect to the possible states of the user’s motion and an attempt to recognize these states. In this study, we propose a method for real-time visual state classification of a user with a walking support system. The visual features are extracted using principal component analysis and classification is performed by hidden Markov models, both for real-time fall detection (one-class classification) and real-time state recognition (multi-class classification). The algorithms are used in experiments with a passive-type walker robot called “RT Walker” equipped with servo brakes and a depth sensor (Microsoft Kinect). The experiments are performed with 10 subjects, including an experienced physiotherapist who can imitate the walking pattern of the elderly and people with disabilities. The results of the state classification can be used to improve fall-prevention control algorithms for walking support systems. The proposed method can also be used for other vision-based classification applications, which require real-time abnormality detection or state recognition.     

Capture and representation of human walking in live video sequences

Extracting human representations from video has vast applications. In this paper, we present a knowledge-based framework to capture metarepresentations for real-life video with human walkers. The system models the human body as an articulated object and the human walking as a cyclic activity with highly correlated temporal patterns. We extract for each of the body parts its motion, shape, and texture. Once available, this structural information can be used to manipulate or synthesize the original video sequence, or animate the walker with a different motion in a new synthesized video     

Output tracking control for an omnidirectional rehabilitative training walker with incomplete measurements and random parameters

In this study, we propose a model and an output feedback tracking control for an omnidirectional rehabilitative training walker (ODW) with unmeasurable speed, incomplete measurements of position output, and random structural parameters. A stochastic model and an incomplete measurement model were proposed to describe the motion of an ODW subject to random structural parameters and to account for any incomplete data transmission phenomenon caused by possible sensor ageing or failures. A speed observer and a state observer were designed to estimate the unmeasurable speed and the incomplete measurements of position output. Moreover, a dynamic output feedback controller was constructed to ensure the exponential stability in mean square of the tracking error system. Furthermore, the results verify that the choice of appropriate design parameters can result in the mean square of the tracking error becoming arbitrarily small. A simulation example was provided to illustrate the effectiveness of the proposed design procedures.     

Motion Control of Passive Intelligent Walker Using Servo Brakes

We propose a new intelligent walker based on passive robotics that assists the elderly, handicapped people, and the blind who have difficulty in walking. We developed a prototype of the robot technology walker (RT walker), a passive intelligent walker that uses servo brakes. The RT walker consists of a support frame, two casters, two wheels equipped with servo brakes, and it has passive dynamics that change with respect to applied force/moment. This system is intrinsically safe for humans, as it cannot move unintentionally, i.e., it has no driving actuators. In addition, the RT walker provides a number of navigational features, including good maneuverability, by appropriately controlling the torque of servo brakes based on RT. We propose a human adaptive motion control algorithm that changes the apparent dynamics to adapt to user difficulties, and an environmentally adaptive motion control algorithm, which incorporates environmental information to provide obstacle/step avoidance and gravity compensation functions. The proposed control algorithms are experimentally applied to the RT walker to test their validity.     

The study of a map realization system (cancellation of ambient light and swaying motion of a robot)

For better terrain adaptability, a walking robot should be equipped with a visual sensor. This paper defines the visual sensor for a walking robot as a map realization system, abbreviated MARS, and investigates the way to realize a practical 3-D range-finder which forms the major part of a MARS. First, the improvement in the range-finder's performance to separate and extract a projected laser slit ray in ambient light is investigated. A video signal processing procedure called the DDD (dual signal extraction with delay and difference) method, which extracts a pulse signal by making use of the dual pattern of positive and negative pulses in a differenced video signal, is proposed. The specific method of DDD, which extracts only the maximum pulse, is shown to be more effective and is called MaxDDD. A range-finder with a signal processing system having an optical interference filter, a MaxDDD video signal processor, and noise reduction software based on continuity of the slit ray image between scanning lines is constructed and its high S/N ratio is shown. Second, structural and algorithmic considerations are made to realize real-time compensation of the swinging motion of a walking robot and to generate a terrain map while walking. As a result, it is shown that the position measurement is executed within 240 us per point to generate a map in real time. The experimental MARS range-finder weighs 1.8 kg and is compact. This paper shows the feasibility of producing a practical visual system for walking robots.     

The Torus Treadmill: realizing locomotion in VEs

Locomotion in virtual environments (VEs) remains one of the major problems in current virtual reality research. The most intuitive way to move about the real world is to travel on foot. People often feel a better sense of distance or direction while walking than while riding in a vehicle. This article discusses the development of a locomotion device that provides a sense of walking. In terms of natural interaction, the physical exertion of walking proves essential to locomotion. The research of my colleagues and I aims to give users a sense of walking while their position remains localized in the physical world. We've developed several prototypes of interface devices for walking. From the results of our research, we concluded that an infinite surface would offer an ideal means for giving people a sense of walking. Our device, called the Torus Treadmill, uses a torus-shaped surface to realize the locomotion interface. The surface employs 12 sets of treadmills connected side-by-side and driven in a perpendicular direction. These treadmills generate an infinite surface. We measured the motion of the users' feet with magnetic sensors. The floor moves in the opposite direction of the walker, canceling the motion of each step. The walker's position remains localized in the real world by this computer-controlled motion of the floor. The walker can freely change direction. An image of the virtual space appears in a head-mounted display corresponding to the walker's virtual position     

The motion control of a statically stable biped robot on an unevenfloor

This work studies the motion control of a statically stable biped robot having seven degrees of freedom. Statically stable walking of the biped robot is realized by maintaining the center-of-gravity inside the convex region of the supporting foot and/or feet during both single-support and double-support phases. The main points of this work are framing the stability in an easy and correct way, the design of a bipedal statically stable walker, and walking on sloping surfaces and stairs.     

Non-contact physical activity estimation method based on electrostatic induction technique

We here present a method for measuring human physical activity, which is based on detecting the electrostatic induction current generated by the walking motion under non-contact and non-attached conditions. A theoretical model for the electrostatic induction current generated because of a change in the electric potential of the human body is also proposed. By comparing the obtained electrostatic induction current with the theoretical model, it becomes obvious that this model effectively explains the behavior of the waveform of the electrostatic induction current. The normal walking motions of daily living are recorded using a portable sensor measurement located in an ordinary house. The obtained results show that detailed information regarding physical activity such as a walking cycle can be estimated using our proposed technique. This suggests that the proposed technique, which is based on the detection of the walking signal, can be successfully applied to the estimation of human physical activity.     

虚拟人行走的动作融合

研究在行走时虚拟人动作与虚拟地形之间的交互性。通过碰撞检测来确定人体在地面之上的正确位置。利用动作融合的方法,即将几个典型动作按合适的权重结合产生新的动作数据,实时地驱动虚拟人并使之对环境变化的反应满足视觉上的逼真性。融合过程中各原始动作的权重取决于沿着和垂直于人体运动方向的2个地面坡度,同时也通过对地形的几何分析来实现虚拟人对其周边地形的感知。     

新型力解耦机器人六维力传感器研究

用应力分析的方法得到了一个可用于测力的应用测量原理 ,根据该原理设计了一种新型六维力传感器 ,分析了其受力与变形元件测量点应力的对应关系。分析结果表明该传感器的输出是力解耦的 ,具有结构简单 ,工艺性好等优点 ,可应用在仿人行走机器人脚部以及其它类型机器人需要使用多维力传感器的场合     

Experimental studies on passive dynamic bipedal walking

Passive dynamic walking is a gait developed, partially or in whole, by the energy provided by gravity. The research on passive dynamic bipedal walking helps create an understanding of walking mechanics. Moreover, the experimental passive dynamic research provides a base to compare and validate computer simulation results. An improved kneed bipedal walking mechanism was designed and built to study the passive gait patterns. The first aim of this study is to determine the equivalency of testing a passive dynamic biped walker on a treadmill to testing on a ramp. Based on the small difference between the gait patterns measured on the two test platforms, testing on a treadmill was found equivalent to testing on a ramp. Gait measurements were then conducted on the treadmill to evaluate the effects of the treadmill inclination angle, mass distribution of the biped, and the length of flat feet on the gait pattern. Results show that most of these parameters had significant effects on the step length, step period and hip velocity of the passive walker. Our experimental results are also compared with previous experimental results.     

Passive dynamic turning in 3D biped locomotion: an extension to passive dynamic walking

Passive dynamic walking usually refers to a kind of walking where a biped walker is able to walk downhill, without any actuation or control, just due to the gravity. Although most of works done in this regard have concentrated on passive walking along a straight line, in this paper we extend this concept to a more general case of locomotion, i.e. turning or walking along curved path. We call the novel extension passive turning, and categorize it to two types of finite and infinite. We showed that the finite type is still applicable on a typical downhill or ramp, while the infinite type is only practical on a specific surface profile that we call it helical ramp. Furthermore, several stability and parameter analysis are also conducted to evaluate more aspects of this notion. We highlighted that surprisingly, the passive straight walking is actually a special case of passive turning, just with infinite radius of turn and less asymptotical stability. It should be noted that the present study is performed using a model of an arc-foot three-dimensional (3D) compass gait walker.     

Wearable artificial skin layer for the reconstruction of touched geometry by morphological computation

ABSTRACT

This paper proposes a wearable haptic sensor for the reconstruction of the surface geometry of an object to be touched. The proposed haptic sensor is a thin rubber artificial skin layer that is formed around the user's finger or other body part and contains a small embedded strain gauge for measuring large deformations. The sensor can be easily fabricated by rubber dipping. First, it was demonstrated that the proposed sensor is not only able to statically detect the curvature of the touched surface but can also measure deformations due to rapid light tapping with robustness against motion noise. As an illustrative demonstration of morphological computation in haptics, it was then demonstrated that it is possible to reconstruct the geometry of tiny undulations in the surface of the touched object from the information obtained by the proposed sensor.     

人性化可折叠助行车设计

助行车是帮助行走不便的老年人与腿部有残疾的人群辅助行走与实现腿部功能恢复训练的设备。讨论了人性化设计理念,研究与分析了行走不便的老年人与腿部残疾人群的生理与心理需求,进行了助行车人性化设计的人机关系分析,给出了助行车关键部位设计尺寸,在考虑了稳定性与舒适性要求的基础上完成了可折叠助行车的总体设计与细节设计。所设计的助行车除了具备助行功能,还具备一定娱乐功能与报警等功能。助行车可在不需行走状态变换成座椅休息,助行车可折叠存放与搬运。给出了助行车的助行状态设计方案、座椅休息状态设计方案、折叠存放状态设计方案以及细节设计方案。     

A Robotic Walker Based on a Two-Wheeled Inverted Pendulum

This paper presents the design and control of a robotic walker based on a two-wheeled inverted pendulum (TWIP) developed to assist mobility-impaired users with balance and stability. Traditional walkers use three or more contact points to create a solid base to augment a user’s balance. A TWIP walker can support a user’s balance through balance control. A robotic walker prototype has been developed to illustrate its ability to assist human gait and exploit the maneuverability of a two-wheeled mobile platform compared to multi-wheeled system. Presented is a linearized mathematical model of the two-wheeled system using Newtonian mechanics. A control strategy consisting of a decoupled linear quadratic regulator (LQR) controller and two state variable controllers is developed to stabilize the platform and regulate its behavior with robust disturbance rejection performance. Results are shown using a physical prototype to demonstrate the ability of the decoupled LQR controller to robustly balance the platform while the state variable controllers regulate the platform’s position with smooth, minimum jerk, control when used by a person during standing and walking.     

Online generation of cyclic leg trajectories synchronized with sensor measurement

The generation of trajectories for a biped robot is a problem which has been largely studied for several years, and many satisfying offline solutions exist for steady-state walking in absence of disturbances. The question is a little more complex when the generation of the desired trajectories of joints or links has to be achieved or adapted online, i.e. in real time, for example when it is wished to strongly synchronize these trajectories with an external motion. This is precisely the problem addressed in this paper. Indeed, we consider the case where the “master” motion is measured by a position sensor embedded on a human leg. We propose a method to synchronize the motion of a robot or of other device with respect to the output signal of the sensor. The main goal is to estimate as accurately as possible the current phase along the gait cycle. We use for that purpose a model based on a nonlinear oscillator, which we associate an observer. Introducing the sensor output in the observer allows us to compute the oscillator phase and to generate a synchronized multilinks trajectory, at a very low computational cost. The paper also presents evaluation results in terms of robustness against parameter estimation errors and velocity changes in the input.     

振弦式传感器测频系统的设计

根据振弦式传感器工作原理而设计的测频系统主要由手持式测频仪和PC计算机组成。测频仪采用直读式测频法测量振弦式传感器的输出频率,并将测量值和传感器特性参数代入固化在其内部的计算公式进行计算,从而实现传感器物理量的现场显示。同时,还可以通过PC计算机的串口将测量数据传给计算机,由计算机对数据进行处理、显示。该系统可大大减轻测量人员和工程技术人员的劳动强度,缩短测量和计算时间,提高测量及计算准确度。     

A reflexive neural network for dynamic biped walking control

Biped walking remains a difficult problem, and robot models can greatly facilitate our understanding of the underlying biomechanical principles as well as their neuronal control. The goal of this study is to specifically demonstrate that stable biped walking can be achieved by combining the physical properties of the walking robot with a small, reflex-based neuronal network governed mainly by local sensor signals. Building on earlier work (Taga, 1995; Cruse, Kindermann, Schumm, Dean, & Schmitz, 1998), this study shows that human-like gaits emerge without specific position or trajectory control and that the walker is able to compensate small disturbances through its own dynamical properties. The reflexive controller used here has the following characteristics, which are different from earlier approaches: (1) Control is mainly local. Hence, it uses only two signals (anterior extreme angle and ground contact), which operate at the interjoint level. All other signals operate only at single joints. (2) Neither position control nor trajectory tracking control is used. Instead, the approximate nature of the local reflexes on each joint allows the robot mechanics itself (e.g., its passive dynamics) to contribute substantially to the overall gait trajectory computation. (3) The motor control scheme used in the local reflexes of our robot is more straightforward and has more biological plausibility than that of other robots, because the outputs of the motor neurons in our reflexive controller are directly driving the motors of the joints rather than working as references for position or velocity control. As a consequence, the neural controller and the robot mechanics are closely coupled as a neuromechanical system, and this study emphasizes that dynamically stable biped walking gaits emerge from the coupling between neural computation and physical computation. This is demonstrated by different walking experiments using a real robot as well as by a Poincaré map analysis applied on a model of the robot in order to assess its stability.     

简单0-1规划问题的动态DNA折纸计算模型

DNA折纸是一种全新的DNA自组装方法。将一个由DNA折纸卡槽、双态DNA机器、DNA行走机器人组装而成的动态折纸应用于求解0-1规划问题。其中DNA折纸卡槽由1条M13脚手架链和202条钉书钉链折叠而成。双态DNA机器分为不修饰和修饰金纳米颗粒两种情况,对应于0-1规划问题约束变量的取值为0或者1。DNA折纸卡槽和DNA双态机器组装成折纸基底。DNA行走机器人是7条单链折叠成的带有粘性末端的DNA折纸。在链的驱动下,DNA行走机器人在折纸基底上顺时针旋转行走,每步旋转120°。DNA行走机器人每走两步,与折纸基底上的DNA双态机器进行链置换,接收修饰的金纳米颗粒。当整个动态行走过程结束,根据透射电镜下DNA行走机器人接收的金纳米颗粒的大小和个数来判断约束变量的取值是否为可行解。该计算模型采用模块化结构,DNA折纸卡槽、双态DNA机器、DNA行走机器人等折纸均单独设计,且采用透射电镜读解,因而提高了模型实现的可行性。