基于分子马达的骨骼肌生物力学原理及其在外骨骼机器人人机力交互中应用

发布时间：2018-09-19 13:17

【摘要】：外骨骼机器人是一种穿戴式具有防护、助力和助行等功能的机器人，在军事、康复医疗等领域有着巨大的应用价值和广阔的市场前景，也是国内外竞相研究的热点。随着我国经济的快速发展，人们对生活质量和生命健康更加关注和重视。与此同时，人口老龄化及肢残人的增加也带来了重大社会问题，对智能型外骨骼康复机器人有着广泛需求。但是，由于存在可穿戴性、高可靠性、人机交互、智能控制等技术难点，，真正走向临床应用的外骨骼机器人仍不多见，高性能的人机交互接口及交互技术成为制约其应用的瓶颈问题之一，而其中与外骨骼人机力交互技术密切相关的人机力交互机理，特别是骨骼肌收缩生物力学原理非常值得深入探索。本文以实现对人体下肢主动康复训练为目标，开发出下肢外骨骼机器人，通过分析骨骼肌中分子马达的纳米力学特性及运行机制，探索骨骼肌生物力学原理，从微观到宏观构建基于分子马达集体运行机制的骨骼肌力学模型，并设计基于EMG信号、接触力信号的人机交互接口，研究人与外骨骼之间力交互机理，制订外骨骼机器人控制策略，开展了人机力交互及机器人控制实验研究。本文的主要工作及取得的成果可以归纳为以下几点：一、以肌球蛋白分子马达为对象，分析分子马达的纳米力学特性及运行机制。针对分子马达的循环工作过程，探索了分子马达在van der Waals力、Casimir力、静电力及布朗力等耦合作用下向肌动蛋白丝接近并结合的运动规律，建立了分子马达循环过程的动力学模型，通过Monte Carlo方法对分子马达的运动过程模拟发现，接近过程中当分子马达与细肌丝表面距离大于3nm时，起主要作用的力为Casimir力和静电力；当距离小于3nm时，van der Waals力和静电力使分子马达向细肌丝轨道快速接近，比较这几个力的影响可知，接近过程中静电引力占主导，并由此阐明了分子马达开始运行并使肌肉收缩的力学机理，解析了钙离子在肌肉收缩中的关键作用，同时分析了分子马达所处空间势场对肌纤维结构稳定性的影响。二、通过分析分子马达集体运行特性，利用非平衡态统计力学方法从微观到宏观构建了新的骨骼肌力学模型。首先研究分子马达的集体运行机制，为了反映分子马达一个循环周期的N个状态，构建位移变量概率密度的Fokker-Planck方程，并考虑肌小节空间结构特征、分子马达弹性系数、肌小节横截面积等因素，推导出肌小节主动收缩力学模型，通过计算位移变量的概率密度分布，分析了ATP浓度、负载力对主动收缩力及收缩速度的影响。进一步地，针对骨骼肌激活与收缩过程，建立动作电位频率与肌小节收缩力之间稳态关系，考虑肌小节的串并联作用，最终从微观到宏观建立基于分子马达集体运行机制的骨骼肌力学模型。计算表明，随着动作电位频率的增加，肌浆中钙离子浓度先线性上升并逐渐趋于饱和，主动收缩力出现融合并跟随钙离子浓度变化趋势，当动作电位处于最大频率时肌肉强直收缩，在ATP浓度饱和情况下，肌肉最大等长收缩力主要取决于分子马达数目、弹性系数、肌肉横截面积等物理参数，由于动作电位的叠加形成EMG信号，由此为开展EMG信号特征与肌肉力之间联系研究奠定了理论基础。三、针对人体下肢关节运动范围大、自由度多、关节力矩大等运动特征，从仿生学角度设计实现了多功能下肢外骨骼机器人，开发出并联关节式外骨骼踝关节。外骨骼机器人系统结构紧凑，膝关节转动范围0~110度、髋关节-25~55度，能满足人体步行要求，并联踝关节能实现人体踝关节背屈/跖屈、内翻/外翻两个自由度运动，外骨骼机器人适合身高在155cm~190cm的人使用，并可主动调整人体重心轨迹使之符合上下波动的特征，系统有较高的稳定性和可靠性。同时开发了基于EMG信号、力触觉信号的人机交互接口，包括传感单元（EMG信号采集仪、交互力传感器）、数据采集及处理单元，重点开展了人与外骨骼之间力交互机理研究，建立了外骨骼机器人的动力学模型，并以人体膝关节为对象，利用大腿骨胳肌肉系统进行了人体膝关节正向/逆向动力学建模，构建EMG信号特征频率与肌肉收缩力、关节力矩之间函数关系。四、开展了人机力交互实验及人机接口在外骨骼机器人主动控制中应用。首先，完善了外骨骼机器人控制系统并制定了满足不同康复训练要求的外骨骼控制策略；其次，进行了人机力交互实验，通过采集大腿肌肉EMG信号、人与外骨骼交互力，利用EMG信号表征肌肉激活程度，根据肌肉力学模型计算肌肉收缩力和关节力矩，比较肌肉主动力矩与外骨骼对人的反作用力矩，实验结果表明两者之间吻合较好，证明了所构建肌肉力学模型的合理性；最后，根据外骨骼机器人控制策略，对人体进行了被动与主动训练，其中被动模式是按照设定的步态及角度信息完成了对人体下肢训练，主动模式是结合人机交互接口，采集肌肉的EMG信号，利用肌肉力学模型预测关节运动所需力矩，识别人体运动意图，根据预测信息完成了对外骨骼机器人的智能控制，实现了按照人体意图的主动助力训练。
[Abstract]:Exoskeleton robot is a kind of wearable robot with the functions of protecting, assisting and walking. It has great application value and broad market prospects in military, rehabilitation and other fields. It is also a hot research topic at home and abroad. With the rapid development of China's economy, people pay more attention to the quality of life and health. At the same time, the aging of population and the increase of the disabled also bring about major social problems, and there is a wide demand for intelligent exoskeleton rehabilitation robots. Interactive interface and interaction technology have become one of the bottlenecks restricting its application. The mechanism of human-computer interaction, especially the biomechanical principle of skeletal muscle contraction, which is closely related to exoskeleton-human interaction technology, deserves further exploration.
In this paper, a lower extremity exoskeleton robot is developed to achieve active rehabilitation training of human lower extremities. By analyzing the nanomechanical properties and operating mechanism of molecular motors in skeletal muscle, the biomechanical principle of skeletal muscle is explored. A skeletal muscle mechanical model based on the collective operation mechanism of molecular motors is constructed from micro to macro, and designed based on it. EMG signal, human-computer interaction interface of contact force signal, force interaction mechanism between human and exoskeleton is studied, control strategy of exoskeleton robot is formulated, and Experimental Research on human-computer interaction and robot control is carried out.
Firstly, taking myosin molecular motor as the object, the nanomechanical properties and operation mechanism of the molecular motor are analyzed. According to the cyclic working process of the molecular motor, the movement law of the molecular motor approaching and combining to actin filament under the coupling action of van der Waals force, Casimir force, electrostatic force and Brownian force is explored, and the molecular motor is established. The kinetic model of the cycling process was established by Monte Carlo method. It was found that when the distance between the molecular motor and the filament surface was more than 3 nm, the main forces were Casimir force and electrostatic force, and when the distance was less than 3 nm, van der Waals force and electrostatic force made the molecular motor move to the filament orbit faster. Comparing the effects of these forces, we can see that the electrostatic force is dominant in the process of approaching, and thus clarify the mechanical mechanism of the molecular motor starting to run and muscle contraction, and analyze the key role of calcium ions in muscle contraction. At the same time, we analyze the influence of the spatial potential field of the molecular motor on the stability of muscle fiber structure.
Secondly, a new skeletal muscle mechanics model is constructed by analyzing the collective operation characteristics of molecular motors and using the non-equilibrium statistical mechanics method from microscopic to macroscopic. Firstly, the collective operation mechanism of molecular motors is studied. In order to reflect the N states of a cycle of molecular motors, the Fokker-Planck equation of the probability density of displacement variables is constructed and examined. The mechanical model of active contraction of sarcomere was deduced by considering the spatial structure of sarcomere, the elastic coefficient of molecular motor and the cross-sectional area of sarcomere. The effects of ATP concentration and load on the active contraction force and contraction velocity were analyzed by calculating the probability density distribution of displacement variables. The steady-state relationship between the action potential frequency and the contraction force of sarcomeres was established. Considering the series-parallel interaction of sarcomeres, a skeletal muscle mechanical model based on the collective operation mechanism of molecular motors was established from microscopic to macroscopic. Active contraction force fuses and follows the trend of calcium ion concentration. When the action potential is at its maximum frequency, the muscles contract rigidly. When the ATP concentration is saturated, the maximum isometric contraction force mainly depends on the number of molecular motors, elastic coefficient, muscle cross-sectional area and other physical parameters. This lays a theoretical foundation for the study of the relationship between EMG signal characteristics and muscle strength.
Thirdly, according to the motion characteristics of human lower limb joints, such as wide range of motion, many degrees of freedom and large joint torque, a multi-functional lower limb exoskeleton robot is designed and implemented from the perspective of bionics, and a parallel articulated exoskeleton ankle joint is developed. For walking, the parallel ankle joint can realize the back flexion/plantar flexion of the ankle joint and the inversion/valgus motion with two degrees of freedom. The exoskeleton robot is suitable for the people whose height is between 155 cm and 190 cm, and can adjust the trajectory of the center of gravity of the human body actively to conform to the characteristics of fluctuation. The system has high stability and reliability. The human-computer interaction interface of force-tactile signal, including sensor unit (EMG signal acquisition instrument, interactive force sensor), data acquisition and processing unit, focuses on the study of force interaction mechanism between human and exoskeleton, establishes the dynamic model of exoskeleton robot, and takes human knee joint as the object, carries out the research using the thigh skeletal muscle system. The forward/reverse kinetics model of human knee joint was established to construct the functional relationship between EMG signal characteristic frequency and muscle contraction force and joint torque.
Fourthly, the human-machine interaction experiment and the application of human-machine interface in the active control of exoskeleton robot are carried out. Firstly, the control system of exoskeleton robot is improved and the exoskeleton control strategy is formulated to meet the different rehabilitative training requirements. Secondly, the human-machine interaction experiment is carried out, and the human-exoskeleton interaction is achieved by collecting the EMG signal of thigh muscle. Mutual force is represented by EMG signal, muscle contraction force and joint torque are calculated according to muscle mechanics model, and the reaction torque between muscle active torque and exoskeleton is compared. The experimental results show that the two coincide well, which proves the rationality of the muscle mechanics model. Finally, according to exoskeleton robot control. The passive mode is to complete the training of human lower limbs according to the set gait and angle information. The active mode is to collect the EMG signals of muscles by combining the human-computer interaction interface, predict the required torque of joint motion by using the muscle mechanics model, identify the human motion intention, and according to the prediction letter. It completes the intelligent control of the external skeleton robot, and realizes the active assistance training according to the human body's intention.
【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2012
【分类号】：TH789

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