Muscle circumference sensor and model reference-based adaptive impedance control for upper limb assist exoskeleton robot

In this paper, we have addressed two issues for upper limb assist exoskeleton: (1) estimation of human desired motion intention (DMI) using non-biological-based sensors; and (2) compliant control using model reference-based adaptive approach. For non-biological-based DMI estimation, we have employed Muscle Circumference Sensor (MCS) and load cells. MCS measures human elbow joint torque using human arm kinematics, biceps/triceps muscle model, and physiological cross-sectional area of these muscles. So, using MCS, we have measured Biceps/Triceps internal muscle activity and we have tried to reduce it by providing robotic assistance. To extract DMI, we have employed radial basis function neural network (RBFNN). RBFNN uses position, velocity, and human force to estimate DMI which is further tracked by the impedance control law. This algorithm is based on model reference-based adaptive impedance control law which drives the overall assist exoskeleton to the desired reference impedance model, giving required compliance. To highlight the effectiveness, we have compared proposed control algorithm with simple impedance and adaptive impedance control algorithms. Experimental results demonstrate the reduced muscle activity and active compliance for subject wearing the robot.     

Analysis of motor synergies utilization for optimal movement generation for a human-like robotic arm

Controlling human-like robots with musculoskeletal structure has been a challenging problem in engineering. In biological studies, motor synergy hypothesis has been proposed as a solution in order to control high degree-of-freedom and complex human body. In this paper, we focus on exploring the applicability of motor synergies in generating goal-directed movements by optimal control in a human-like robotic arm. We focus on three problems： 1） Can motor synergies facilitate the solving of optimal control problem？ 2） What properties should motor synergies have in order to achieve tasks？ 3） How should motor synergies be utilized better？ For the first problem we show that goal-directed movements can be achieved by utilizing motor synergies which have properties of achieving the goals. For the second problem, we testify motor synergies which have different properties and discover that energy efficiency is an important aspect in motor synergies which can also be utilized to achieve goal-directed movements. This discovery also implies that we can obtain motor synergies by other ways rather than from goal-directed optimal control signals. For the third problem, we show that the control complexity can be further reduced by utilizing a subset of motor synergies which are effective to achieve goals.     

Equilibrium point-based control of muscle-driven anthropomorphic legs reveals modularity of human motor control during pedalling

ABSTRACT

This study aims at shedding new light on the human motor control during forward and backward pedalling motions from a viewpoint of the mechanical impedance, determined by the coordinated activations of multiple pairs of agonist-antagonist muscles, called equilibrium point (EP)-based synergy. First, human movements and electromyograms as muscle activations during forward and backward pedalling motions were measured, and using our working model proposed earlier, they were analysed to obtain EP-based synergies, i.e. a set of synergy vectors and the corresponding time-courses of synergy activation coefficients associated with a virtual trajectory, for each pedalling direction. We showed the similarity in the EP-based synergies between forward and backward motions. We performed a robot experiment, where we used the EP-based synergies for the forward pedalling with their time-reversed synergy activation coefficients and a phase-shift in a coefficient for a specific synergy vector to actuate a robot of muscle-driven anthropomorphic legs for achieving a backward pedalling. Comparisons between the backward motion in the robot and that in human confirmed that they were mostly the same. Our results support our working model that the human motor control shares the common EP-based synergy and the associated mechanical impedance for controlling the forward and backward pedalling motions.     

Iterative learning control for robotic-assisted upper limb stroke rehabilitation in the presence of muscle fatigue

The use of iterative learning control to regulate assistive functional electrical stimulation applied to the muscles of patients undergoing robotic-assisted upper limb stroke rehabilitation has been followed through small scale clinical trials. These trials confirmed that an increase in patient ability to complete the specified task also led to a reduction in the level of electrical stimulation required. This previous work assumed that the effects of muscle fatigue could be neglected but if a patient suffers fatigue during a rehabilitation session then their the session goals are not achieved or, more likely, the session must be abandoned due to the time limits imposed by the ethical approval required to conduct such sessions. In this paper the results of the first investigation into enhancing the control scheme to remove or lessen the effects of fatigue and hence make better use of the time available for a session are given. The scheme considered adds a feedback loop around the muscle model used, where the performance results given are based on a model for the dynamics constructed using patient data collected in previous clinical trials.     

双臂空间机器人协调操作运动控制仿真系统的设计与实现

阐述了双臂自由飞行空间机器人闭链式协调操作运动控制实验平台的建立方法。将VC 6.0、OpenGL、Matlab和Matcom四种软件融合起来,搭建FFSR(自由飞行空间机器人)系统实验平台;通过运动控制算法描述了机器人双臂协调操作目标物的动态特性,给出了机器人本体中心的位置姿态和转角的变化曲线,验证了该运动控制算法的正确性,以及编程效率的优越性。     

Nonlinear sliding mode control of an unmanned agricultural tractor in the presence of sliding and control saturation

The paper considers the problem of automatic path tracking by autonomous farming vehicles subject to wheel slips, which are characteristic for agricultural applications. Two guidance laws are proposed to solve this problem, and both explicitly take into account the constraints on the steering angle and ensure tracking an arbitrarily curved path. The first law is implemented by the pure sliding-mode controller, whereas the second one combines the sliding mode approach with a smooth nonlinear control law and requests control chattering at the reduced amplitude as compared with the first law. Mathematically rigorous proofs of global convergence and robust stability of the proposed guidance laws are presented. In doing so, the slipping effects are treated as bounded uncertainties. Simulation results and real world experiments confirm the applicability and performance of the proposed guidance approach.     

Improved control and simulation models of a tricycle collaborative robot

The objective of collaborative manufacturing is to create the synergism from the collaboration of manufacturing resources. Most of the studied collaborations are made among intelligent machines; however, the collaboration can be realized even between machines and human being, and a collaborative robot (Cobot) belongs to the latter. A cobot is a robot designed to assist human beings as a guide or assistor in a constrained motion. Various prototypes have been developed and the potentials of these robots have been demonstrated. The research presented in this paper focuses on the control and simulation models of a tricycle cobot with three steered wheels, with the following two contributions: (i) A concise model for the closed-loop control is developed. Existing closed-loop control has been implemented in an intuitive way, and some control parameters have to be determined by a trial-and-error method. (ii) A simulation model is proposed to validate the control algorithms. No simulation model is available and the control models of other existing systems have to be validated experimentally. The developed control and simulation models have been implemented. Graphic simulation is also developed. Case studies are provided and the simulation results are analyzed.     

A review on modelling, implementation, and control of snake robots

This paper provides an overview of previous literature on snake robot locomotion. In particular, the paper considers previous research efforts related to modelling of snake robots, physical development of these mechanisms, and finally control design efforts for snake locomotion. The review shows that the majority of literature on snake robots so far has focused on locomotion over flat surfaces, but that there is a growing trend towards locomotion in environments that are more challenging, i.e. environments that are more in line with realistic applications of these mechanisms.     

Decoupling force and motion control in industrial robots

A theoretical approach to force control design for industrial robots involved in surface-following tasks is described in this paper, assuming an infinitely stiff environment. Independent Joint Control techniques, based on standard (PID) algorithms, are adopted for position control. Force control acts as an outer loop, by adding a bias to the position set points in the joint space. A simple model and compensation of the joint flexibility effects, that play an important role in determining the dynamic behavior of the system, are also presented, leading to a force control decoupled from motion control. Some experimental results are discussed, with reference to the industrial robot SMART.     

Effect of visual display height on modelled upper and lower cervical gravitational moment,muscle capacity and relative strain

Head and neck posture is an important factor in neck pain related to computer use; however, the evidence for an optimal posture is unconvincing. This study measured the 3-D postures of 36 young adults during use of three different display heights. Cervical extensor muscle strain was estimated using modelled gravitational load moments and muscle capacities. The influence of more or less upper vs. lower cervical movement was also explored across a broad range of potential postures. Overall cervical extensor muscle capacity diminished away from a neutral posture whilst gravity moment increased with flexion. Overall cervical extensor muscle strain increased with head flexion but remained stable into head extension. Individual differences in the amount of upper and lower cervical movement had an important effect on strain, particularly for some muscles. Computer display height guidelines are an important component of ergonomics practice, yet the relative strain on neck extensor muscles as a function of display height has not been examined. The current findings provide more detailed biomechanical evidence that ergonomists can incorporate with usability and other evidence to determine appropriate display height recommendations.     

基于功能性电刺激的上肢康复系统条件反馈控制

功能性电刺激是脑卒中患者有效的康复方法,然而上肢肌肉的动态模型存在着强非线性、多源扰动、模型不精确和参数变化大等控制难点.为提高基于功能性电刺激的上肢康复系统的跟踪速度和扰动抑制能力,本文提出了一种基于条件反馈的比例–积分控制策略,条件反馈的设计用于提高系统的跟踪性能,通过比例–积分控制器抑制外部扰动与模型不确定性.通过单一变量法分析了控制器参数对控制效果的影响,提出了一种简单、实用的参数整定规则.基于Hammerstein肌骨系统模型,通过仿真验证了所提方法在保证闭环系统鲁棒性的前提下,与常规的比例–积分控制器相比在跟踪和扰动抑制性能方面的优势.最后,基于搭建的上肢康复系统控制平台,对不同实验者在不同目标输出力下进行对比实验,实验结果表明本文所提基于条件反馈的比例–积分控制策略的平均峰值量占比为9.22%,而对比控制策略的平均峰值量占比为17.80%,所提控制策略的平均单位误差绝对值积分指标是对比控制策略平均单位误差绝对值积分指标的70.43%,验证了本文所设计的控制策略在保证闭环系统鲁棒性的前提下具有更好的跟踪效果.     

实时上肢参数辨识的康复机器人力控制研究

针对病人进行康复训练时,上肢动力学参数估计不准确和训练过程发生上肢动力学参数变化,所导致康复机器人系统辅助力计算不准确,影响精确和稳定的控制练训。为减小辅助力计算误差,实现精确和稳定的训练控制,基于阻抗控制算法,使用多元线性回归方法对上肢动力学参数进行辨识,提出了一种实时上肢动力学参数辨识的阻抗控制算法,建立了康复机器人动力学模型,同时对控制算法进行仿真研究。仿真结果表明该算法能够准确地对上肢动力学参数进行辨识,有效地消除了辅助力计算误差,实现训练过程中训练轨迹精确控制。     

康复机器人上肢传递系统的周期稳态与自主控制

研究康复机器人上肢传递系统的周期稳态和自主控制.运用计时事件图和极大–加代数方法,建立康复机器人上肢传递系统的数学模型,给出传递系统的周期计算公式、周期稳态的扰动估计范围和自主控制策略,并分析周期稳态相对于参数扰动的鲁棒性.周期稳态的扰动估计可用于提高上肢康复机器人工作的精确性和柔顺性,而自主控制策略有益于保证上肢康复机器人工作的实时性和安全性.扰动估计和自主控制方法易于计算,并有助于上肢康复机器人传递运动智能辅助系统的设计、控制和优化.     

Variation in upper limb posture and movement during word processing with and without mouse use

Work postures and movements of the upper limb were analysed for 12 ‘mouse’ operators and 12 ‘non-mouse’ computer operators employed in word-processing work. Measurements were carried out during correction of a given text. ‘Mouse’ operators spent 64% of the working time with the operative wrist deviating more than 15° towards the ulnar side, while ‘non-mouse’ operators spent 96% of the time with the corresponding wrist in neutral position towards radial deviation. The rotation in the shoulder was at all times in neutral position towards inward rotation for ‘non-mouse’ operators, while ‘mouse’ operators worked 81% of the time with the shoulder rotated outward more than 30°. ‘Mouse’ operators corrected a longer text during the given time. Our observations showed long periods of strenuous working postures for ‘mouse’ operators compared to ‘non-mouse’ operators. We believe that further investigations need to be carried out on the effects of word-processing techniques and to develop ergonomic work station designs for the ‘mouse’ and other non-keyboard input devices.     

Design and control of a climbing robot based on hot melt adhesion

Robust climbing in unstructured environments has been one of the long-standing challenges in robotics research. Among others, the control of large adhesion forces is still an important problem that significantly restricts the locomotion performance of climbing robots. The main contribution of this paper is to propose a novel approach to autonomous robot climbing which makes use of hot melt adhesion (HMA). The HMA material is known as an economical solution to achieve large adhesion forces, which can be varied by controlling the material temperature. For locomotion on both inclined and vertical walls, this paper investigates the basic characteristics of HMA material, and proposes a design and control of a climbing robot that uses the HMA material for attaching and detaching its body to the environment. The robot is equipped with servomotors and thermal control units to actively vary the temperature of the material, and the coordination of these components enables the robot to walk against the gravitational forces even with a relatively large body weight. A real-world platform is used to demonstrate locomotion on a vertical wall, and the experimental result shows the feasibility and overall performances of this approach.     

Modelling the movement of a two-link manipulator

An algorithm for optimizing the control signal for simple movements of a two-link manipulator with four degrees of freedom is described. Based on the typical movement and functions of upper human extremities, the manipulator (so-called anthropomorphic manipulator) is composed of two links. The motion of the links is developed by four driving motors. The mathematic model is based of the Lagrange equations of the IInd king. The minimization of the time of movement with initial limitation of accuracy is obtained and the error of the final position is minimized without changing the time-optimal criterion. The relations connected with minimalization of both quality factors are considered. At the same time, the algorithm optimizes the torque distribution between the actuators which drive each link of manipulator. As well the manipulator as its activity are modelled on the digital computer. The results of the computer simulation of the algorithm, and the modelling of the time and accuracy optimal control, are presented.     

The effectiveness of ergonomics interventions in reducing upper limb work-related musculoskeletal pain and dysfunction in sonographers,surgeons and dentists: a systematic review

Abstract

The aim of this systematic review was to summarise the effects of ergonomics interventions on work-related upper limb musculoskeletal pain and dysfunction, and on productivity in sonographers, surgeons and dentists. A total of 31 studies were included. All studies reported effects on upper limb pain. Nine studies reported effects on dysfunction and only two studies reported effects on productivity. Moderately strong evidence in reducing upper limb pain was found for instigation of microbreaks into long duration surgical procedures, and the use of wider, lighter handles in dental instruments. Moderate evidence was also found for use of prismatic glasses and favourable positioning in reducing upper limb pain. Weak, inconsistent or no evidence was found for all other ergonomics interventions in reducing upper limb pain and dysfunction and increasing productivity. The lack of high quality research, particularly in sonographers and in the outcome of productivity, should be addressed.

Practitioner summary: This systematic review investigates the effectiveness of ergonomics interventions on upper limb pain, dysfunction and productivity in sonographers, dentists and surgeons. Instigation of microbreaks during long duration procedures and the use of wider, lighter instrument handles were most effective in reducing upper limb work-related pain.

Abbreviations: ANOVA: analysis of variance; CLS: conventional laparoscopic surgery; DMAIC: define, measure, analyze, improve and control; GRADE: grading of recommendations, assessment, development and evaluations; HD: high definition; PRISMA: preferred reporting items for systematic reviews and meta-analyses; PROSPERO: The International Prospective Register of Systematic Reviews; RCT: randomised control trial; SILS: single incision laparoscopic surgery; VITOM: video telescopic operative microscope; WNSWLHD: Western New South Wales Local Health District; WMSD: work related musculoskeletal disorder     

Development of an adaptive fuzzy behavioural control system with experimental and industrial applications

This paper discusses a newly developed Adaptive Fuzzy Behavioural Control System which has been designed for use with an autonomous mobile robot. The merit of the system is the capability to adapt the fuzzy function to suit the environmental conditions encountered without changes to the rule base. This is compared to conventional behavioural control and demonstrated by simulation. The paper also discuses the results of both experimental and industrial applications in which this new control system was applied.     

A simple approach to the control of locomotion in self-reconfigurable robots

In this paper we present role-based control which is a general bottom-up approach to the control of locomotion in self-reconfigurable robots. We use role-based control to implement a caterpillar, a sidewinder, and a rolling track gait in the CONRO self-reconfigurable robot consisting of eight modules. Based on our experiments and discussion we conclude that control systems based on role-based control are minimal, robust to communication errors, and robust to reconfiguration.     

The accuracy of conventional 2D video for quantifying upper limb kinematics in repetitive motion occupational tasks

Marker-less 2D video tracking was studied as a practical means to measure upper limb kinematics for ergonomics evaluations. Hand activity level (HAL) can be estimated from speed and duty cycle. Accuracy was measured using a cross-correlation template-matching algorithm for tracking a region of interest on the upper extremities. Ten participants performed a paced load transfer task while varying HAL (2, 4, and 5) and load (2.2 N, 8.9 N and 17.8 N). Speed and acceleration measured from 2D video were compared against ground truth measurements using 3D infrared motion capture. The median absolute difference between 2D video and 3D motion capture was 86.5 mm/s for speed, and 591 mm/s² for acceleration, and less than 93 mm/s for speed and 656 mm/s² for acceleration when camera pan and tilt were within ± 30 degrees. Single-camera 2D video had sufficient accuracy ( < 100 mm/s) for evaluating HAL.

Practitioner Summary: This study demonstrated that 2D video tracking had sufficient accuracy to measure HAL for ascertaining the American Conference of Government Industrial Hygienists Threshold Limit Value^® for repetitive motion when the camera is located within ± 30 degrees off the plane of motion when compared against 3D motion capture for a simulated repetitive motion task.