Experimental Research of Force Feedback Dataglove Based on Pneumatic Artificial Muscle

Force feedback dataglove is an important interface of human-machine interaction between manipulator and virtual assembly system, which is in charge of the bidirectional transmission of movement and force information between computer and operator. The exoskeleton force feedback dataglove is designed taking the pneumatic artificial muscle as actuator, meanwhile, its structure and work principle are introduced, and the force control problem is analyzed and researched by experiment. The mathematic model of grasping rigid object for finger is established. Considering the friction of tendon-sheath system and finger deformation, the closed-loop force control for a single joint, a single finger and multi-fingers are studied respectively by the feedforward proportional-integral（PI） control method with variable arguments. On the premise of the force smoothness, the control error of the force exerted on the finger joint is in the range of ±0.25 N, which meets the requirement of force feedback. By experimental analysis, the reason of force fluctuation is that the finger joint has a small amplitude quiver, and the consistent change tendency of the force between proximal interphalangeal（PIP） joint and distal interphalangeal（DIP） joint results from their angle coupling relationship.

MODEL IMPROVEMENT AND EXPERIMENT VALIDATION OF PNEUMATIC ARTIFICIAL MUSCLES

According to the deficiency of the present model of pneumatic artificialmuscles (PAM), a serial model is built up based on the PAM's essential working principle with theelastic theory, it is validated by the quasi-static and dynamic experiment results, which are gainedfrom two experiment systems. The experiment results and the simulation results illustrate that theserial model has made a great success compared with Chou's model, which can describe the forcecharacteristics of PAM more precisely. A compensation item considering the braid's elasticity andthe coulomb damp is attached to the serial model based on the analysis of the experiment results.The dynamic experiment proves that the viscous damp of the PAM could be ignored in order to simplifythe model of PAM. Finally, an improved serial model of PAM is obtained.

Active Force with Fuzzy Logic Control of a Two-Link Arm Driven by Pneumatic Artificial Muscles

In this paper, the practicality and feasibility of Active Force Control （AFC） integrated with Fuzzy Logic（AFCAFL） applied to a two link planar arm actuated by a pair of Pneumatic Artificial Muscle （PAM） is investigated. The study emphasizes on the application and control of PAM actuators which may be considered as the new generation of actuators comprising fluidic muscle that has high-tension force, high power to weight ratio and high strength in spite of its drawbacks in the form of high nonlinearity behaviour, high hysteresis and time varying parameters. Fuzzy Logic （FL） is used as a technique to estimate the best value of the inertia matrix of robot arm essential for the AFC mechanism that is complemented with a conventional Propor- tional-Integral-Derivative （PID） control at the outermost loop. A simulation study was first performed followed by an experi- mental investigation for validation. The experimental study was based on the independent joint tracking control and coordinated motion control of the arm in Cartesian or task space. In the former, the PAM actuated arm is commanded to track the prescribed trajectories due to harmonic excitations at the joints for a given frequency, whereas for the latter, two sets of trajectories with different loadings were considered. A practical rig utilizing a Hardware-In-The-Loop Simulation （HILS） configuration was developed and a number of experiments were carried out. The results of the experiment and the simulation works were in good agreement, which verified the effectiveness and robustness of the proposed AFCAFL scheme actuated by PAM.

FORCE FEEDBACK DATAGLOVE BASED ON PNEUMATIC ARTIFICIAL MUSCLES

An exoskeleton force feedback dataglove is developed, which uses the pneumatic artificial muscles as actuators. On the basis of the simplified hand model, the motion equation is deduced according to the theory of Denavit-Hartenberg. The model of the equivalent contact forces exerted by the object on the finger is proposed. By the principle of virtual work, the static equilibrium of finger is established. The force Jacobian matrix of finger is calculated, and then the joint torques of the finger when grasping objects are obtained. The theory and structure of the force feedback datagolve are introduced. Based on the theory of motion stabilization of four-bar linkage, the flexion angles of joints are measured. The torques on finger joints caused by the output forces of pneumatic artificial muscles are calculated. The output forces of pneumatic artificial muscle, whose values are controlled by its inner pressure, can be calculated by the joint torques of the finger when grasping objects. The arms of force, driving torques and the needed output forces of pneumatic muscle are calculated for each joint of the index finger. The criterion of output force of pneumatic muscle is given.

Design and test of pneumatic artificial muscle driven variable trailing-edge camber wing

A variable camber wing driven by pneumatic artificial muscles is developed in this paper. Firstly, the experimental setup to measure the static output force of pneumatic artificial muscle is designed and the relationship between the static output force and the air pressure is investigated. Experimental results show that the static output force of pneumatic artificial muscle decreases nonlinearly with the increase of contraction ratio. Secondly, the model of variable camber wing driven by pneumatic artificial muscles is manufactured to validate the variable camber concept. Finally, wind tunnel tests are conducted in the low speed wind tunnel. It is found that the wing camber increases with the increase of air pressure. When the air pressure of PAMs is 0.4 MPa and 0.5 MPa, the tip displacement of the trailing-edge is 3 mm and 5 mm, respectively. The lift of aerofoil with flexible trailing-edge increases by 87% at AOA of 5°.

Joint position control of bionic jumping leg driven by pneumatic artificial muscle

The bionic legs are generally driven by motors which have the disadvantages of large size and heavy weight.In contrast,the bionic legs driven by pneumatic artificial muscles(PAMs)have the advantages of light weight,good bionics and flexibility.A kind of bionic leg driven by PAMs is designed.The proportional-integral-derivative(PID)algorithm and radial basis function neural network(RBFNN)algorithm are combined to design RBFNN-PID controller,and a low-pass filter is added to the control system,which can effectively improve the jitter phenomenon of the joint during the experiment.It is verified by simulation that the RBFNN-PID algorithm is better than traditional PID algorithm,the response time of joint is improved from 0.15 s to 0.07 s,and the precision of joint position control is improved from 0.75°to 0.001°.The experimental results show that the amplitude of the change in error is reduced from 0.5°to 0.2°.It is verified by jumping experiment that the mechanism can realize jumping action under control,and can achieve the horizontal displacement of 500 mm and the vertical displacement of 250 mm.

Precise Positioning of Pneumatic Artificial Muscle Systems

Pneumatic artificial muscles (PAMs) currently possess a high power-to-weight ratio, a high power-to-volume ratio, and a high degree of safety. They have therefore been applied to many power assist devices and positioning mechanisms such as bionic robots, welfare devices, and parallel manipulators. However, the significant nonlinear characteristics of PAM mechanisms limit their positioning accuracies. The accuracies are generally lower than 5 μm, which preclude the PAM from precision systems. Nevertheless, enhancing the positioning accuracy is desired to extend the application fields of PAMs. This study aims to clarify a practical controller design method to achieve the precise positioning of PAM systems. As the first step of this research, a linear motion mechanism with a pair of McKibben PAMs was constructed and a conventional dynamic model for this system is introduced. The dynamic model is used to explain the basic characteristics of the PAM mechanism and discuss the necessary characteristics for precise positioning. Then open-loop step and sinusoidal responses of the PAM mechanism were examined by experimental and simulated results. Next, for precise positioning, the practical controller design procedure is discussed and determined based on the measured open-loop responses. The proposed controller design procedure can be easily implemented into PAM mechanisms without an exact dynamic model. The positioning performance of such a system was experimentally evaluated. The experimental results show that although the positioning accuracy depends on the target position, the positioning error is lower than 1 μm even in the worst case and the positioning resolution can be set to 0.5 μm.

Adaptive Self‐Tuning Fuzzy Controller for a Soft Rehabilitation Machine Actuated by Pneumatic Artificial Muscles

Pneumatic artificial muscles (PAMs) have the highest power to weight and power to volume ratios of any actuator. Therefore, they can be used not only in rehabilitation engineering, but also as actuators in robots, including industrial and therapy robots. Because PAMs have highly nonlinear and time‐varying behavior associated with gas compression and the nonlinear elasticity of bladder containers, achieving excellent tracking performance using classical controllers is difficult. An adaptive self‐tuning fuzzy controller (ASTFC) including adaptive fuzzy sliding mode control (AFSMC) and functional approximation (FA) was developed in this study for overcoming the aforementioned problems. The FA technique was used to release the model‐based requirements and the update laws for the coefficients of the Fourier series function parameters were derived using a Lyapunov function to guarantee control system stability. The experimental results verified that the proposed approach can achieve excellent control performance despite external disturbance.

Hopping planning of the bionic leg mechanism driven by PAMs with biarticular muscle

Bionic robots are generally driven by motors.As robots driven by pneumatic artificial muscles(PAMs)have the advantages of light weight,good bionics and flexibility,more and more researchers have adopted PAMs to drive bionic robots.A kind of bionic leg driven by PAMs for hopping is proposed in this work.A 3-DOF bionic leg driven by 4 PAMs is designed by analyzing the biological structure and movement principles of frog legs,and 3 kinds of leg configuration with different PAMs arrangement is proposed.One biarticular muscle is used to increase the joint rotating range.The bracket pulley and PAMs for driving joint can effectively increase its rotating range.The rotating range of hip and knee joint driven by a biarticular muscle is simulated.The simulation results show that the biarticular muscle can transfer the movement of the hip joint to the knee joint and increase the rotating range of the knee joint.The greater the contraction of PAM,the greater the rotating range of joint.The bionic leg can perform planned step distance and step height of hopping.

A Survey on Pneumatic Muscle Actuators Modeling

The aim of this article is to provide a survey on the most popular modeling approaches for PMAs （pneumatic muscle actuators）. PMAs are highly non-linear pneumatic actuators where their elongation is proportional to the interval pressure. During the last decade, there has been an increase in the industrial and scientific utilization of PMAs, due to their advantages such as high strength and small weight, while various types of PMAs with different technical characteristics have appeared in the literature. This article will： （a） analyse the PMA＇s operation from a mathematical modeling perspective; （b） present their merits and drawbacks of the most common PMAs; and （c） establish the fundamental basis for developing industrial applications and conducting research in this field.

悬吊式重力卸荷系统的主动式缓冲控制

针对索驱悬吊式重力卸荷系统被动缓冲器带来的欠驱动问题,提出了基于气动人工肌肉(Pneumatic Artificial Muscle,PAM)主动式缓冲器控制方法。首先,分析用于地面微/低重力模拟的悬吊式重力卸荷系统,为了克服PAM高度非线性特性,提出基于块结构的非线性神经网络建模方法,其次分析吊索与航天器相互作用过程中挠性引起的力扰动,最后采用非线性模型预测跟踪控制。相比传统PID控制方法,该方法具有参数调节简单,实时跟随性能好,以及对卸荷系统目标惯性参数的摄动具有控制性能不变性等优势。实验结果表明,设置不同扰动情况跟随力误差都能保证在3%以内,实验证明了基于PAM主动缓冲器的可行性,所提出的控制方法能够在挠性不确定性的情况下实现力跟随控制。

人工肌肉驱动的腰部助力器设计与仿真研究

目的为了帮助腰椎疾患、腰肌劳损、弯腰作业者,方法提出一种由McKibben型气动人工肌肉实现轻量化、柔性助力、穿戴舒适的腰部助力器,分析穿戴与未穿戴腰部助力器搬举重物时腰部主要肌群的肌肉力变化,验证腰部助力器的有效性。通过三维动作捕捉系统和三维测力系统采集受试者在搬举过程中的运动学和动力学数据,导入腰部助力器三维模型作为驱动数据,建立人体腰部骨骼肌肉生物力学模型,利用Hill型三元素肌肉模拟McKibben型气动人工肌肉,搭建人机交互模型并进行仿真分析。通过测量重物搬举过程中腰部主要肌群的肌电信号变化,对比肌电信号曲线与肌肉力曲线趋势,验证仿真分析结果的有效性。结果实验结果表明,穿戴腰部助力器运动时主要参与作用的为竖脊肌、多裂肌和腰方肌,其中竖脊肌助力效果最为显著,助力效果达到43%。结论通过进行人机交互模型的生物力学仿真,验证了搬举重物时腰部助力器的有效性,该助力器可为护理人员和物料搬运工作者提供助力。

PAM-Motor复合驱动仿生肩关节结构设计及动力学特性研究

针对仿生机器人关节重载情况下难以实现精确控制的问题,以及气动人工肌肉(Pneumatic artificial muscle,PAM)控制非线性、时变性、滞后性等特点,受生物关节在肌肉和骨骼的协作下产生运动的启发,提出一种气动人工肌肉和电机复合驱动的新型驱动仿生肩关节结构设计,用于提高仿生机器人肩关节的控制精度及驱动性能。基于Chou模型及能量守恒定理,推导了复合驱动仿生肩关节结构参数与动力学特性之间的映射模型;通过构建基于拉格朗日动力学的PAM-Motor复合驱动系统俯仰运动和侧摆运动的动力学模型,探究了仿生肩关节复合驱动机理。研究结果表明,PAM-Motor复合驱动仿生肩关节具有良好的精度、灵巧度和承载能力,验证了复合驱动仿生肩关节结构的合理性和有效性。

救护车载PAM担架缓冲系统特性分析

经对救护车担架隔振系统及动力学模型研究分析,提出气动人工肌肉(PAM)救护车担架隔振系统。建立车体-担架-分段人体振动模型,设计基于该系统的半主动神经网络PID控制器,并用Simulink对隔振系统进行性能仿真分析。仿真结果表明,与被动系统相比,采用神经网络PID控制的气动人工肌肉隔振系统对担架及人体有明显隔振效果,气动人工肌肉用于救护车担架隔振系统具有可行性。

基于PAM和MRD的新型六维宽频隔振系统及其特性

提出了一种刚度阻尼解耦,且可调并能大幅降低支撑频率的基于PAM(气动肌肉)和MRD(磁流变阻尼器)的六维宽频隔振系统,推导了由弹性、阻尼作用空间到支撑平台笛卡尔六维空间的雅可比矩阵,获得了系统的惯性、刚度及阻尼矩阵,在此基础上,建立了系统振动方程,分析了系统的解耦特性、支撑频率的可降特性以及宽频隔振原理,讨论了弹性阻尼元件的参数计算方法。该成果可为车载/舰载/机载精密设备的六维宽频隔振提供理论参考。

PAM对抗肌驱动机械臂的运动平稳性研究

针对气动人工肌肉存在的不稳定性问题,本文采用动力学原理,对由PAM组成的对抗肌驱动的单自由度机械臂在运动过程如何保持其平稳性进行研究,并采用MAT-LAB软件中的SIMULINK仿真技术对其进行仿真分析。仿真结果表明,通过对输入条件进行调整,完全可以达到要求,即满足稳定的角度输出70.36°,达到此输出的时间为2s以内,位置角度和速度都处于稳定的状态,达到ΔT最大值所需的时间不影响整个系统的稳定性。该研究为后续对系统进行深入的控制特性分析提供了更合理的系统参数。

Analysis on pivot turning of quadruped robot with bionic flexible body driven by the PAMs

The pivot turning function of quadruped bionic robots can improve their mobility in unstructured environment.A kind of bionic flexible body mechanism for quadruped robot was proposed in this paper,which is composed of one bionic spine and four pneumatic artificial muscles(PAMs).The coordinated movement of the bionic flexible body and the leg mechanism can achieve pivot turning gait.First,the pivot turning gait planning of quadruped robot was analyzed,and the coordinated movement sequence chart of pivot turning was presented.Then the kinematics modeling of leg side swing and body bending for pivot turning was derived,which should meet the condition of the coordinated movement between bionic flexible body and leg mechanism.The PAM experiment was conducted to analyze its contraction characteristic.The study on pivot turning of the quadruped robot will lay a theoretical foundation for the further research on dynamic walking stability of the quadruped robot in unstructured environment.

Modeling and Adaptive Self-Tuning MVC Control of PAM Manipulator Using Online Observer Optimized with Modified Genetic Algorithm

In this paper, the application of modified genetic algorithms (MGA) in the optimization of the ARX Model-based observer of the Pneumatic Artificial Muscle (PAM) manipulator is investigated. The new MGA algorithm is proposed from the genetic algorithm with important additional strategies, and consequently yields a faster convergence and a more accurate search. Firstly, MGA-based identification method is used to identify the parameters of the nonlinear PAM manipulator described by an ARX model in the presence of white noise and this result will be validated by MGA and compared with the simple genetic algorithm (GA) and LMS (Least mean-squares) method. Secondly, the intrinsic features of the hysteresis as well as other nonlinear disturbances existing intuitively in the PAM system are estimated online by a Modified Recursive Least Square (MRLS) method in identification experiment. Finally, a highly efficient self-tuning control algorithm Minimum Variance Control (MVC) is taken for tracking the joint angle position trajectory of this PAM manipulator. Experiment results are included to demonstrate the excellent performance of the MGA algorithm in the NARX model-based MVC control system of the PAM system. These results can be applied to model, identify and control other highly nonlinear systems as well.

MRB-PAM康复柔性关节设计与分析

针对当前康复下肢机器人动力源刚度较强的问题,以及气动人工肌肉控制非线性、滞后性等问题,依照生物关节摆动的启发,提出设计了一种气动人工肌肉和磁流变制动器复合驱动的膝关节。通过构建拉格朗日动力学的MRB-PAM柔性关节的动力学模型,探究了仿生柔性关节驱动机理。研究结果表明,MRB-PAM柔性关节具有良好的精度、稳定性和承载能力,验证了柔性关节的合理性和有效性。

一种扁平气动人工肌肉驱动的直接心脏压缩装置

直接心脏压缩装置是一种用于增强心脏收缩能力的心脏辅助设备,可直接作用于心脏外表面,不与血液直接接触,避免了感染和凝血等问题。将软体机器人领域中一种扁平气动人工肌肉结构用作直接心脏压缩装置的驱动器。六个扁平气动人工肌肉以仿生的方式被等间距嵌入装置的弹性基底中,气压驱动来模拟心脏收缩生理运动。在20、30和40 kPa的压强下,通过仿真和实验得到不同腔室数量扁平气动人工肌肉的长度位移和径向位移,还通过实验得到不同数量驱动器下装置的容积变化。此外,分析了压强在20~80 kPa时以上指标的变化趋势,以表征装置辅助心脏收缩性能。结果表明:以1 Hz频率驱动时,驱动器及装置整体的收缩性能都随着压强的增加而呈非线性增加,且装置收缩性能随驱动器个数的增加而增加。装置性能变化趋势符合预期,为后续直接心脏压缩装置的设计提供了一种新的思路。