可穿戴式下肢外骨骼康复机器人研究进展

对于脊髓损伤、脑损伤等因素导致下肢运动障碍的患者,利用下肢外骨骼康复机器人可在患者损伤早期进行精准康复,并在康复过程中优化康复策略。本文详细对比了下肢外骨骼康复机器人相比于传统康复方法的优势,并结合国内外研究现状阐述了不同外骨骼机器人的设备特点及应用场景,详细分析了机器人的驱动方式、控制系统以及训练模式等关键技术。最后,着重探讨了下肢外骨骼康复机器人未来发展所面对的挑战,并针对机械结构优化、驱动算法优化、康复流程智能化、基于虚拟现实技术的应用场景优化及康复效果评估等5方面提出了可行的探讨,对下肢外骨骼康复机器人未来的技术发展趋势作出可行分析。     

Generalized Control Framework for Exoskeleton Robots by Interaction Force Feedback Control

This paper newly proposes a generalized control framework for exoskeletons. Motivated by the fact that the exoskeleton robot and its wearer physically interact by the force at each contact point and that this interaction depends on the controller used in the literature, the proposed method shows that the exoskeleton controllers can be generalized into a standard force feedback control system. To this end, the control system consists of the interaction force feedback control loop and the reference generation loop. The proposed method is advantageous in systematically implementing the conventional approaches and, moreover, extending it to other objectives. The proposed method is applied to a lower-limb exoskeleton, and verified by the experiments.

     

下肢外骨骼研究进展及关节运动学解算综述

随着传感融合、移动计算、智能驱动等技术的发展以及研究者对人体运动中下肢重要生物力学功能认知的逐步深化,下肢外骨骼机器人作为一种与下肢并联,能为穿戴者行走助力的可穿戴智能设备愈发受到世界各研究机构的重视。本文根据下肢外骨骼的用途和结构详细综述了近年下肢外骨骼的研究进展,并借此对下肢外骨骼的未来发展进行展望。并针对下肢外骨骼在实时运动学检测与控制上对小型传感器的迫切需求,提出一种能够用于控制下肢外骨骼的基于惯性测量单元的人体下肢关节运动学测量与解算技术,在基于惯性测量的单自由度关节角度结算上得到较好结果。     

Neural network-based asymptotic tracking control of unknown nonlinear systems with continuous control command

ABSTRACT

This paper proposes a robust tracking controller for a class of nonlinear second-order systems with time-varying uncertainties. The controller is mainly based on the robust integral of the sign of the error (RISE) control approach to achieve an asymptotic stability result with a continuous control command in the presence of additive uncertainties. An adaptive feedforward neural network control term is blended with a new RISE controller to improve the system's transient performance. The proposed RISE controller is a modified version of the existing saturated RISE controller such that only sign of the derivative of the output is needed. The stability of the closed-loop system is well studied, where a local asymptotic stability is proven. The controller performance is validated through simulations on a two-degree-of-freedom lower limb robotic exoskeleton.     

Real-time myoelectric control for a lower-limb assistive exoskeleton

This paper describes the approach to a novel algorithm for real-time myoelectric onset detection based on the classic moving average method with added features to provide onset detection while myoelectric signals are recorded from two muscles at a time. The aim of this algorithm is focused on the generation of real-time binary signals to drive a dc motor attached to the hip joint of a rehabilitation exoskeleton for the assistance on lower-limb rehabilitation of hemiplegic patients in supine/prone, seated and standing positions. With this low computational cost real-time control algorithm based on myoelectric signals, patients involved on a physical rehabilitation program wearing the developed exoskeleton will have full control over the assistance for the lower-limb exercises. The parameter tuning for the myoelectric onset detection algorithm and the results of its accuracy along several tests over two test subjects on the rectus femoris and semitendinosus muscles are presented.     

An admittance shaping controller for exoskeleton assistance of the lower extremities

We present a method for lower-limb exoskeleton control that defines assistance as a desired dynamic response for the human leg. Wearing the exoskeleton can be seen as replacing the leg’s natural admittance with the equivalent admittance of the coupled system. The control goal is to make the leg obey an admittance model defined by target values of natural frequency, peak magnitude and zero-frequency response. No estimation of muscle torques or motion intent is necessary. Instead, the controller scales up the coupled system’s sensitivity transfer function by means of a compensator employing positive feedback. This approach increases the leg’s mobility and makes the exoskeleton an active device capable of performing net positive work on the limb. Although positive feedback is usually considered destabilizing, here performance and robust stability are successfully achieved through a constrained optimization that maximizes the system’s gain margins while ensuring the desired location of its dominant poles.     

Flat trajectory design and tracking with saturation guarantees: a nano-drone application

Abstract

This paper deals with the problem of trajectory planning and tracking of a quadcopter system based on the property of differential flatness. First, B-spline characterisations of the flat output allow for optimal trajectory generation subject to waypoint constraints, thrust and angle constraints while minimising the trajectory length. Second, the proposed tracking control strategy combines feedback linearisation and nested saturation control via flatness. The control strategy provides bounded inputs (thrust, roll and pitch angles) while ensuring the overall stability of the tracking error dynamics. The control parameters are chosen based on the information of the a priori given reference trajectory. Moreover, conditions for the existence of these parameters are presented. The effectiveness of the trajectory planning and the tracking control design is analysed and validated through simulation and experimental results over a real nano-quadcopter platform, the Crazyflie 2.0.     

A myosignal-based powered exoskeleton system

This paper studies the integration of a human arm with a powered exoskeleton (orthotic device) and its experimental implementation in an elbow joint, naturally controlled by the human. The human-machine interface was set at the neuromuscular level, by using the neuromuscular signal (EMG) as the primary command signal for the exoskeleton system. The EMG signal along with the joint kinematics were fed into a myoprocessor which in turn predicted the muscle moments on the elbow joint. The moment-based control system integrated myoprocessor moment prediction with feedback moments measured at the human arm/exoskeleton and external load/exoskeleton interfaces. The exoskeleton structure under study was a two-link, two-joint mechanism, corresponding to the arm limbs and joints, which was mechanically linked by the human operator. Four indices of performance were used to define the quality of the human/machine integration and to evaluate the operational envelope of the system. Experimental results indicate the feasibility of an EMG-based power exoskeleton system as an integrated human-machine system using high-level neurological signals     

Simulated motion negatively affects motor task but not neuromuscular performance

The effects of long duration simulated motion on motor task and neuromuscular performance along with time frames required to recover from these effects are relatively unknown. This study aimed to determine (1) how simulated motion affects motor task and neuromuscular performance over one hour of motion and (2) the time course of recovery from any decrements. The dependent variables that were measured included: reaction time; visuomotor accuracy tracking; maximal voluntary contractions; voluntary activation; evoked contractile properties and biceps brachii electromyography of the elbow flexors. Reaction times and error rates of the visuomotor accuracy tracking task were compromised in motion, but maximal force, voluntary activation, evoked contractile properties and rmsEMG responses of the biceps brachii were unaffected by motion. It is concluded that motion causes an increase in attention demands, which have a greater effect on motor task rather than neuromuscular performance.

Practitioner Summary: Minor delays or mistakes can separate life and death at sea. The safety and productivity of most vessels rely on error-free performance of motor tasks. This study demonstrates that human ability to perform motor tasks is compromised by ship motions and may aid in developing training and safety guidelines for seafarers.     

On Security of Compressed Gray Scale Image Using Joint Encryption and Data Hiding

ABSTRACT

This paper proposes a novel scheme that integrates quality access control and tracking of illicit distribution of digital image(s) in a single platform. The goal is achieved by (1) modulating some of the valuable Discrete Cosine Transform (DCT) coefficients of the compressed data followed by (2) embedding a binary watermark (fingerprint) as tracking information using Quantization Index Modulation (QIM). The data modulation process serves the purpose of access control so that an unauthorized user is unable to enjoy proper visual quality. On the other hand, embedded watermark tracks illicit distribution. The coefficients to be modulated are selected pseudo randomly using a secret key (K). Before embedding, the watermark is encoded by applying convolution coding that reliably identifies colluder(s) involved in time varying (intelligent) collusion operation. Simulation results have shown the validity of the above claims without affecting compatibility with standard JPEG coding scheme.     

Optimization-based analysis of push recovery during walking motions to support the design of rigid and compliant lower limb exoskeletons

Abstract

Lower limb exoskeletons provide a promising approach to allow disabled people to walk again in the future. Designing such exoskeletons and tuning the required actuators is challenging, since the full dynamics of the combined human-exoskeleton system have to be taken into account. In particular, it is important to not only consider nominal walking motions but also extreme situations such as the recovery from large perturbations. In this paper, we present an approach based on push recovery experiments while walking, multibody system models, and least-squares optimal control to analyze the required torques to be generated by the exoskeleton, assuming that the human provides no torque. We consider seven different trials with varying push locations and push magnitudes applied on the back of the subject. In a first study, we investigate the dependency of these total joint torques on the exoskeleton mass – and compare the torques required for a human without exoskeleton to the ones for the human with two different exoskeleton configurations. In a second study, we investigate how optimally chosen passive spring-damper elements can support the required torques in the exoskeleton joints. It can be shown that the active torques can be reduced significantly in the different joints and cases.     

下肢康复机器人的研究进展与临床应用

社会老龄化进程中,由于疾病或事故导致下肢受损的患者越来越多,患者的运动能力康复变得尤为重要.相对于传统的物理康复治疗方法,利用下肢康复机器人进行运功功能康复训练可以准确评估、大幅改善康复效果,提高康复效率,节约医疗康复资源.作为一种涉及康复医学、机械学、控制学、机器人学、计算机学及人工智能等诸多学科的智能仿生机电设备,下肢康复机器人按照患者的康复作业姿态主要分为坐卧式下肢康复机器人和站立式下肢康复机器人.其中坐卧式下肢康复机器人可以分为脚踏板式和外骨骼式机器人,站立式下肢康复机器人分为悬挂减重式和独立可穿戴式机器人.本文调研了国际上应用较为广泛的几类下肢康复机器人的代表性产品,详细分析了下肢康复机器人的主被动自由度、驱动方式、传动关节、感知技术、运动控制策略和训练模式等关键技术,并对各类机器人典型临床测试案例进行了比较和探讨,对下肢康复机器人未来的技术发展做出展望.     

Control of an exoskeleton robot arm with sliding mode exponential reaching law

Robots are now working not only in human environments but also interacting with humans, e.g., service robots or assistive robots. A 7DoFs robotic exoskeleton MARSE-7 (motion assistive robotic-exoskeleton for superior extremity) was developed as an assistive robot to provide movement assistance and/or ease daily upper-limb motion. In this paper, we highlight the nonlinear control of MARSE-7 using the modified sliding mode exponential reaching law (mSMERL). Conventional sliding control produces chattering which is undesired for this kind of robotic application as it causes damage to the mechanical structure. Compared to conventional sliding control, our approach significantly reduces chattering and delivers a high dynamic tracking performance. The control architecture was implemented on a field-programmable gate array (FPGA) in conjunction with a RT-PC. In experiments, trajectory tracking that corresponds to typical passive arm movement exercises for single and multi joint movements were performed to evaluate the performance of the developed robot and the controller. Experimental results demonstrate that the MARSE-7 can effectively track the desired trajectories.     

The effect of a passive trunk exoskeleton on metabolic costs during lifting and walking

The objective of this study was to assess how wearing a passive trunk exoskeleton affects metabolic costs, movement strategy and muscle activation during repetitive lifting and walking. We measured energy expenditure, kinematics and muscle activity in 11 healthy men during 5?min of repetitive lifting and 5?min of walking with and without exoskeleton. Wearing the exoskeleton during lifting, metabolic costs decreased as much as 17%. In conjunction, participants tended to move through a smaller range of motion, reducing mechanical work generation. Walking with the exoskeleton, metabolic costs increased up to 17%. Participants walked somewhat slower with shortened steps while abdominal muscle activity slightly increased when wearing the exoskeleton. Wearing an exoskeleton during lifting decreased metabolic costs and hence may reduce the development of fatigue and low back pain risk. During walking metabolic costs increased, stressing the need for a device that allows disengagement of support depending on activities performed.

Practitioner summary: Physiological strain is an important risk factor for low back pain. We observed that an exoskeleton reduced metabolic costs during lifting, but had an opposite effect while walking. Therefore, exoskeletons may be of benefit for lifting by decreasing physiological strain but should allow disengagement of support when switching between tasks.

Abbreviations: COM: centre of mass; EMG: electromyography; LBP: low back pain; MVC: maximum voluntary isometric contraction; NIOSH: National Institute for Occupational Safety and Health; PLAD: personal lift augmentation device; PWS: preferred walking speed without exoskeleton; PWSX: preferred walking speed with exoskeleton; ROM: range of motion; RER: respiratory exchange ratio; V ?O2max: maximum rate of oxygen consumption     

Adaptive PID-like fault-tolerant control for robot manipulators with given performance specifications

ABSTRACT

This paper investigates the trajectory tracking problem of rigid robot manipulators with unknown dynamics and actuator failures. The goal is to achieve desirable tracking performance with a simple and low-cost control strategy. By introducing a new form of parameter estimation error, together with an error transformation, a robust adaptive and fault-tolerant control scheme is developed without the need for fault information nor precise robotic mathematical model. It is shown that, with the proposed control, the tracking error is ensured to converge to an adjustable residual set within prescribed finite time at a user pre-assignable decay rate. The appealing feature of the developed control also lies in its simplicity in structure (i.e. PID form) and effectiveness in dealing with modelling uncertainties as well as actuation faults.     

On-line Walking Speed Control in Human-Powered Exoskeleton Systems Based on Dual Reaction Force Sensors

On-line walking speed control in human-powered exoskeleton systems is a big challenge, the translations of human intention to increase or decrease walking speed in maneuverable human exoskeleton systems is still complex field. In this paper, we propose a novel sensing technique to control the walking speed of the system according to the pilot intentions and to minimize the interaction force. We introduce a new sensing technology “Dual Reaction Force (DRF)” sensors, and explain the methodology of using it in the investigation of walking speed changing intentions. The force signals mismatch successfully applied to control the walking speed of the exoskeleton system according to the pilot intentions. Typical issues on the implementation of the sensory system are experimentally validated on flat terrain walking trails. We developed an adaptive trajectory frequency control algorithm to control the walking speed of HUman-powered Augmentation Lower Exoskeleton (HUALEX) within the human wearer intended speed. Based on the mismatch of DRF sensors, we proposed a new control methodology for walking speed control. Human intention recognition and identification through an sensorized footboard and smart shoe is achieved successfully in this work, the new term heel contact time H _{C T} is main feedback signal for the control algorithm. From the experimental walking trails we found that, the H _{C T} during flat walking ranges from 0.69±0.05 sec and 0.41±0.07 sec while walking speed varies between 1m/s and 2.5m/s. The proposed algorithm used an Adaptive Central Pattern Generators (ACPGs) applied to control joint trajectory frequency, the different walking speeds associated with different functioning of human body CPGs frequency. We validated the proposed control algorithm by simulations on single Degree of Freedom (1-DoF) exoskeleton platform, the simulation results show the efficiency and validated that the proposed control algorithm will provides a good walking speed control for the HUALEX exoskeleton system.     

Active torque-based gait adjustment multi-level control strategy for lower limb patient–exoskeleton coupling system in rehabilitation training

This paper proposes an active torque-based gait adjustment multi-level control strategy for lower limb patient–exoskeleton coupling system (LLPECS) in rehabilitation training. The proposed controller has three levels of high, middle, and low sub-controllers: gait adjustment layer (high-level), interaction torque design layer (middle-level), and trajectory tracking layer (low-level). The high-level sub-controller uses an adaptive central pattern generator (ACPG) to adjust the desired gait for rehabilitation training according to the patient’s active torque. In the middle-level sub-controller, the desired interaction torque is designed with neural networks and the estimated muscle torque by utilizing nonlinear disturbance observer (NDO). In the low-level sub-controller, a time delay estimation-based prescribed performance model free control is designed for the accurate tracking performance of the exoskeleton, so as to make the actual interaction torque track the desired value. An exoskeleton virtual prototype, which is developed in SolidWorks, has been imported to MATLAB/Simulink to conduct co-simulations in the SimMechanics environment. The results of co-simulations demonstrate the effectiveness of the proposed control strategy when the patient’s muscle torque is at different recovery degrees.     

采用核相关滤波的快速TLD视觉目标跟踪

目的 如何对目标进行快速鲁棒的跟踪一直是计算机视觉的重要研究方向之一,TLD（tracking-learning-detection）算法为这一问题提供了一种有效的解决方法,为了进一步提高TLD算法的跟踪性能,从两个方面对其进行了改进。方法 首先在跟踪模块采用尺度自适应的核相关滤波器（KCF）作为跟踪器,考虑到跟踪模块与检测模块相互独立,本文算法使用检测模块对跟踪模块结果的准确性进行判断,并根据判断结果对KCF滤波器模板进行有选择地更新;然后在检测模块,运用光流法对目标位置进行初步预测,依据预测结果动态调整目标检测区域后,再使用分类器对目标进行精确定位。结果 为了验证本文算法的优越性,对其进行了两组实验,实验1在OTB2013和Temple Color128这两个平台上对本文算法进行了跟踪性能的测试,其结果表明本文算法在OTB2013上的跟踪精度和成功率分别为0.761和0.559,在Temple Color128上的跟踪精度和成功率分别为0.678和0.481,且在所有测试视频上的平均跟踪速度达到了27.92帧/s;实验2将本文算法与其他3种改进算法在随机选取的8组视频上进行了跟踪测试与对比分析,实验结果表明,本文算法具有最小的中心位置误差14.01、最大的重叠率72.2%以及最快的跟踪速度26.23帧/s,展现出良好的跟踪性能。结论 本文算法使用KCF跟踪器,提高了算法对遮挡、光照变化和运动模糊等场景的适应能力,使用光流法缩小检测区域,提高了算法的跟踪速度。实验结果表明,本文算法在多数情况下均取得优于参考算法的跟踪性能,在对目标进行长时间跟踪时表现出良好的跟踪鲁棒性。     

Robust nonlinear control schemes for finite-time tracking objective of a 5-DOF robotic exoskeleton

This paper investigates the finite-time robust tracking problem for a 5-DOF (degrees of freedom) upper-limb exoskeleton robot subjected to parametric uncertainties, unmodelled dynamics, and unknown human efforts. By developing the non-singular terminal sliding mode control approach, three innovative schemes of robust torques are proposed to steer configuration variables (angular displacements of joints) of the 5-DOF robotic exoskeleton to the reference trajectories within adjustable finite times. Based on mathematical analysis, it is proven that all suggested schemes of control inputs (input torques) accomplish and provide the mentioned tracking objective accurately. In addition, several new formulas (in the form of inequalities) are derived to determine and tune the needed finite times for achieving the tracking objective. Finally, three numerical examples are given to show the appropriate performance and the acceptable effectiveness of the proposed finite-time robust control schemes.     

Stability analysis of nonlinear multi-agent relay tracking systems over a finite time interval

ABSTRACT

This paper explores the stability of a class of multi-agent systems with proposed relay tracking strategy over a finite time interval. In this paper, agents are deployed in an area to monitor and track the intruded targets. According to proposed relay tracking strategy, the tracking agents and their communication topologies switch during the whole tracking process. This results in impulsive effects on the overall tracking errors. The relationship of finite time interval against desired overall tracking errors and control parameter is derived quantitatively for the multi-agent relay tracking system. Moreover, stability conditions for the system with disturbances and impulsive effects are obtained. Performance of proposed relay tracking strategy and correctness of derived results on stability over finite time intervals are demonstrated by a set of simulations.