气动人工肌肉驱动球面并联机器人关节的力控制研究

分析了具有柔索冗余驱动特点的静力关系，研究了力控制的智能控制算法及策略，在建立的实验样机上达到了良好的力伺服性能．将气动人工肌肉的被动柔顺性与位置控制到力控制过渡的主动柔顺控制策略结合，有效避免了机器人在与环境接触时的碰撞与冲击．     

Miniature Pneumatic Curling Rubber Actuator Generating Bidirectional Motion with One Air-Supply Tube

Soft actuators driven by pneumatic pressure are promising actuators for mechanical systems in medical, biological, agriculture, welfare fields and so on, because they can ensure high safety for fragile objects from their low mechanical impedance. In this study, a new rubber pneumatic actuator made from silicone rubber was developed. Composed of one chamber and one air-supply tube, it can generate curling motion in two directions by using positive and negative pneumatic pressure. The rubber actuator, for generating bidirectional motion, was designed to achieve an efficient shape by nonlinear finite element method analysis, and was fabricated by a molding and rubber bonding process using excimer light. The fabricated actuator was able to generate curling motion in two directions successfully. The displacement and force characteristics of the actuator were measured by using a motion capture system and a load cell. As an example application of the actuator, a robotic soft hand with three actuators was constructed and its effectiveness was confirmed by experiments.     

Novel H-beam electrothermal actuators with capability of generating bi-directional static displacement

A new H-beam electrothermal microactuator is proposed for providing bi-directional static displacement. The design concept and preliminary experimental results of H-beam actuators are presented in this paper. Due to its symmetric structural design, this H-beam actuator can avoid the influence from rotational torques during its bi-directional dynamic and static movement. The restoring force generated by cold beam of H-beam actuator potentially renders this new actuator capability of faster returning speed than conventional electrothermal actuator designs. H-beam actuator is able to generate 50 μm static stroke under 0.9 W electrical dc load. This H-beam electrothermal actuator is well functioned and exhibits good characteristics with high-level performance for industrial applications.     

Sensing mechanism for estimation of the physical properties of an object avoiding failure of the sensors

Active sensing, in which a robot pushes an object and senses the reaction force or joint angle by means of the force sensor at the point of the contact or on the joint, is one of the effective approaches to estimate the physical properties of an object, such as its compliance. A compliant joint driven by elastic actuators has an advantage over a rigid joint driven by a motor with a high gear ratio in that it absorbs the reaction force, and thus avoids any joint damage during active sensing. However, this approach is not suitable for either rigid joint or a compliant joint because the sensors attached to the contact point and the joint tend to break, owing to iterative contact or an excessive force. Here, this paper adopts a one-degree-of-freedom joint mechanism driven by elastic pneumatic actuators, and focuses on the passivity of the elastic pneumatic actuator, in which the pressure is changed when force is applied, after which it is deformed. By utilizing the passivity of the actuators under a number of conditions, this paper derives multiple regression models of the force and the angle, using the pressures before and after force is applied to the joint mechanism. Experimental results present that the contact information can be estimated from the pressure values and that the joint mechanism can detect the elasticity of an object using the regression models. We also observe the range of the elasticity of the object by tuning the joint compliance. This approach provides a robot hand that can estimate the contact information, including the force and joint displacement, avoiding the failure of the sensors.     

Micro parts assembly system with micro gripper and RCC unit

This paper presents a new micro assembly system, which is composed of a micro gripper, a micro remote center compliance (RCC) unit, a voice coil motor-driving mechanism and precision motion stages. The micro gripper is actuated by two shape memory alloy (SMA) wires, and its grip is 1 mm. The micro RCC unit has low translational and rotational stiffness sufficient for micro parts assembly. The voice coil motor-driving mechanism can generate linear motion with an adjustable stiffness, and it can also measure external force in the moving direction. An algorithm for the automatic assembly of micro parts is also proposed, and assembly experiments are performed.     

Design and analysis of a pneumatic high-impact force drive mechanism for in-pipe inspection robots

A pneumatic actuator is suitable and safe for in-pipe inspection robots in inflammable circumstances because of its ability to withstand explosions. However, ordinary pneumatic actuators limit driving speed because of their slow response. In this paper, we propose a novel pneumatic drive mechanism that can produce a high-impact force to move the in-pipe robot forward with sufficient speed by a catastrophic phenomenon using rapid release between a magnet and springs. We also introduce an anisotropic friction mechanism that uses a self-locking phenomenon to transmit the impact force to the pipe walls efficiently. A pin retraction mechanism that releases the self-locking condition is applied to retrieve the robot from the pipes. Optimizations of the proposed design were conducted based on a motion simulation model and verified in experiments. The experimental results obtained for maximum driving speeds in a straight pipe with different material types were approximately 90 and 50 mm/s for horizontal and vertical pipes, respectively. Stable strokes were also observed at different driving frequencies from 0.5 to 2.0 Hz.     

Auxilio: A portable cable-driven exosuit for upper extremity assistance

This paper introduces a fully portable, lightweight exosuit-type device for shoulder and elbow assistance. The main motivation of this research was to design a portable upper limb exosuit capable to assist dynamic rehabilitation tasks where patient can involve trunk motions and overground movements (e.g., during pick-and-place tasks). The proposed system provides assistance for shoulder flexion and abduction, as well as for elbow flexion. The mechanism is driven by DC motors which are worn on the wearer’s back, and the power is transferred from the actuators to the arm by means of cable-driven transmission. The unique features of the proposed exosuit are the absence of rigid links or joints around the arm, high compliance and portability. This paper describes operating principle and kinematic model of the proposed exosuit and provides force analysis and experimental evaluation of the manufactured device. As the result of this work, we performed a simulation of rehabilitation scenario with the developed wearable prototype.     

Six-DOF micro-manipulator based on compliant parallel mechanism with integrated force sensor

This paper describes the design of a micro-scale manipulator based on a six-DOF compliant parallel mechanism (CPM), which is featured by piezo-driven actuators and integrated force sensor capable of delivering six-DOF motions with high precision and providing real-time force information for feedback control. Particularly, the position and screw-based Jacobian analyses of the CPM are presented. Then, the compliance model and the workspace evaluation of the CPM are proposed in order to account for the compliance and obtain design guidelines. Finally, the integrated sensor is introduced. The static features of such a mechanism include high positioning accuracy, structural compactness and smooth and continuous displacements.     

Design of 22-DOF pneumatically actuated upper body for child android ‘Affetto’

Child robots have been used in a lot of studies on human–robot social/physical interaction because they are suitable for safe and casual experiments. However, providing many compliant joints and lifelike exteriors to enhance their interaction potential is difficult because of the limited space available inside their bodies. In this paper, we propose an upper body structure that consists of slider crank and parallel mechanisms for linear actuators and serial mechanisms for rotary actuators. Such combinations of several joint mechanisms efficiently utilize the body space; in total, 22 degrees of freedoms were realized in an upper body space equivalent to that of an 80cm tall child. A pneumatic drive system was adopted in order to fully verify the behavioral performance of the body mechanism. The proposed redundant and compact upper body mechanism can be a platform for testing the effectiveness of future exteriors for the little child android ‘Affetto’, which was developed in order to integrate several key characteristics for achieving advanced human–robot interaction.     

Design and control methodology of a 3-DOF flexure-based mechanism for micro/nano-positioning

A 3-DOF (X–Y–θ_Z) planar flexure-based mechanism is designed and monolithically manufactured using Wire Electro-Discharge Machining (WEDM) technology. The compact flexure-based mechanism is directly driven by three piezoelectric actuators (PZTs) through decoupling mechanisms. The orthogonal configuration in the x and y directions can guarantee the decoupling translational motion in these axes. The rotational motion and translational displacement in the x direction can be decoupled by controlling the piezoelectric actuators in the x axis with the same displacement values in same and opposite motion directions, respectively. The static and dynamic models of the developed flexure-based mechanism have been developed based on the pseudo-rigid-body model methodology. The mechanical design optimization is conducted to improve the static and dynamic characteristics of the flexure-based mechanism. Finite Element Analyses (FEA) are also carried out to verify the established models and optimization results. A novel hybrid feedforward/feedback controller has been provided to eliminate/reduce the nonlinear hysteresis and external disturbance of the flexure-based mechanism. Experimental testing has been performed to examine the dynamic performance of the developed flexure-based mechanism.     

串联弹性驱动器设计、建模及在机器人上的应用

相比于传统的刚性驱动器, 串联弹性驱动器(Series elastic actuator, SEA)具有被动柔顺性、阻抗低、抗冲击、力感知等诸多优点, 因而已被广泛应用于各种机器人系统中. 首先根据弹性和阻尼特性将串联弹性驱动器分为弹性型、阻尼型和弹性−阻尼型串联弹性驱动器, 介绍不同类型串联弹性驱动器的优缺点, 并详细概述弹性和阻尼特性的机械实现方式; 然后对各类串联弹性驱动器作为力传感器的建模方法进行介绍; 接着叙述串联弹性驱动器在机器人系统中的主要应用, 如力传感器、安全保护、降低能耗; 最后展望串联弹性驱动器未来的发展方向.     

New Multi-d.o.f. Haptic Device Using a Parallel Mechanism with a Wide Rotational Working Area

A parallel mechanism is a multi-legged kinematic structure with actuators fixed on the base. In recent years, parallel mechanisms have been implemented in haptic devices due to their benefits, such as high rigidity, high output force, high accuracy and high backdrivability. Multi-d.o.f. haptic devices with rotational motion have become increasingly important as haptic applications have become diversified (e.g., in surgical training). However, typical multi-d.o.f. parallel mechanisms (e.g., Stewart platform and HEXA) have limitations on the working area for rotational motions. A multi-d.o.f. haptic device can be designed by stacking the translational and rotational mechanisms by decoupling these motions. However, this dedoupling can have an adverse effect on inertia because of the weight of the stacking mechanism. Eventually, the operability of the device deteriorates. Therefore, a parallel mechanism with both a translational and rotational multi-d.o.f. structure can effectively apply the full advantages of a parallel mechanism to a multi-d.o.f. haptic device. In this paper, a 6-d.o.f. (five active: three translations, two rotations and one passive rotation) parallel mechanism, called the D-8, is presented. In the D-8, a new redundant parallel mechanism is introduced to overcome the problem of operability.     

Cosine tuning minimizes motor errors

Cosine tuning is ubiquitous in the motor system, yet a satisfying explanation of its origin is lacking. Here we argue that cosine tuning minimizes expected errors in force production, which makes it a natural choice for activating muscles and neurons in the final stages of motor processing. Our results are based on the empirically observed scaling of neuromotor noise, whose standard deviation is a linear function of the mean. Such scaling predicts a reduction of net force errors when redundant actuators pull in the same direction. We confirm this prediction by comparing forces produced with one versus two hands and generalize it across directions. Under the resulting neuromotor noise model, we prove that the optimal activation profile is a (possibly truncated) cosine--for arbitrary dimensionality of the workspace, distribution of force directions, correlated or uncorrelated noise, with or without a separate cocontraction command. The model predicts a negative force bias, truncated cosine tuning at low muscle cocontraction levels, and misalignment of preferred directions and lines of action for nonuniform muscle distributions. All predictions are supported by experimental data.     

Nonlinear control strategy development for asymmetric actuators

We develop a nonlinear control method for asymmetric actuators. Asymmetric actuators do not generate symmetric power during an application. Thrusters and shape memory alloy wires are examples of this class of actuators that produce only unidirectional forces. Hydraulic and pneumatic cylinders are generally asymmetric because, under constant pressure, the generated force in the forward direction is different than that in the reverse direction. Existing control methods assume a symmetric actuation, and therefore, application of asymmetric actuators calls for new control schemes. Current control techniques implement a bias in utilizing asymmetric actuators. However, the amount of the bias depends on the control effort and is not constant. Also, the use of a bias changes the system equilibrium point and introduces a steady-state error. We propose a control scheme capable of producing any biased input. The controller is a second-order system coupled to the system through quadratic terms. The application of quadratic terms for the control input enables us to generate any biased control input, which can be utilized by asymmetric actuators     

改进的自然图像铅笔画效果生成

目的现有的自然图像素描画效果生成算法存在容易造成画面细节丢失,笔画线条单一等问题。针对这些问题,提出一种改进的自然图像素描画效果生成算法。方法通过模拟艺术家创作素描画过程,采用多层次多尺度方法提取图像中不同层次的细节信息,并使用不同长度不同粗细的笔画来模拟艺术家在创作过程中不同力度的绘画效果,分层绘制画面中不同细节层次,然后融合各层次笔画效果形成最终的素描画笔画效果,最后合并素描画笔画效果和素描画图像底纹。结果通过本文算法,可以得到与原输入自然图像内容一致,色调与艺术家绘制的素描画效果相同,笔画和底纹形式与实际素描画相似,真实感较强的素描画效果输出图像。结论大量实验结果表明,本文算法可以生成高质量的自然图像素描画效果,与现有成熟的铅笔画生成技术相笔,该算法具有较强的可比性。     

Development of large-scale stacked-type electrostatic actuators for use as artificial muscles

Electrostatic actuators have the advantages of light weight, flexibility, and high energy efficiency, which make them suitable for use as artificial muscles. However, a traditional electrostatic actuator cannot generate long strokes and a high force density at the same time because such actuator would excessively widen the gap between the electrodes because of its structure. This paper presents a newly developed large-scale stacked-type electrostatic actuator (LSEA) intended for use as an artificial muscle for robots. LSEA is a multi-stacked electrostatic actuator that can be linearly contracted by the application of a voltage. It has a unique structure that prevents overextension of the gap between the electrodes. It can therefore generate a large force. The spring characteristics and the relationship between the contractive force and the stroke were experimentally determined. The findings showed that LSEA prevents the overextension of the gap between the electrodes and has a high contraction ratio that is equivalent to that of a mammalian skeletal muscle.     

Verification of throwing operation by a manipulator with variable viscoelastic joints with straight-fiber-type artificial muscles and magnetorheological brakes

The performance of a robot can be enhanced by increasing its output. However, increasing the output of rigid actuators such as motors and hydraulic actuators will likely increase the weight of the robot. Conversely, organisms such as human beings achieve high output within a short time by accumulating and releasing the elastic energy stored in their muscles; thus, providing an instantaneous force. Moreover, the viscoelastic properties of muscle enable organisms to control their instantaneous force outputs and overall movements. Therefore, in this study, we developed a manipulator with two-degree-of-freedom (DOF) variable viscoelastic joints. The manipulator comprised straight-fiber-type artificial muscles and a magnetorheological (MR) brakes. The ability of a manipulator to generate controlled movement from an instantaneous force was tested in a throwing operation. This simple two-DOF variable viscoelastic manipulator with apparent viscosity control by the MR brakes achieved successful throwing motions. However, it was not possible to calculate the experimental parameters from the target operation in previous study. Therefore, we focused on particle swarm optimization (PSO) as a parameter search method. In this paper, we try to optimize parameters of the throwing movement by combining the spring model of a two-DOF variable viscoelastic manipulator with the PSO method.     

基于阻抗模型的下肢康复机器人交互控制系统设计

为帮助下肢功能障碍患者进行康复训练,设计了下肢康复机器人。对于该机器人的控制,采用传统系统无法柔顺控制,导致机器人运动轨迹偏离预设轨迹。针对该现象,提出了基于阻抗模型的下肢康复机器人交互控制系统设计。通过分析总体控制方案,设计系统硬件结构框图。采用L型二维力传感器,确定两个方向的人机交互力。使用绝对值编码器安装在各个关节处,其输出值作为髋关节、膝关节、踝关节电机的转动位置,增量编码器安装在电机轴上,测量值用来作为后期控制方法的输入参数。构建阻抗控制模型,能够调节机器人位置和速度,具有消除力误差功能。依据此力矩对参考运动轨迹进行设计,实时获取患者康复训练的跟踪、主动柔顺和接近状态信息。在柔顺训练实验测出人机交互力,通过实验结果知,在检测到人体主动力矩异常时,系统能够重新优化轨迹,具有良好柔顺控制效果。     

Task-space synchronisation of nonlinear teleoperation with time-varying delays and actuator saturation

ABSTRACT

In a nonlinear teleoperation system controlled for task-space position tracking, while the time-varying delay in the communication channel has been addressed, the actuator saturation has not been taken into account yet. Considering that in practice, the actuator saturation is a serious constraint, disregarding it in the controller design stage can cause problems. In this paper, we have proposed a control framework to ensure end-effectors position tracking while satisfying sub-task control in the presence of the nonlinear dynamics for the telemanipulators, bounded time-varying delays in the communication channels and saturation in the actuators. We have shown that in free motion and when the operator applies a bounded force to the local robot, the proposed controller not only guarantees the position convergence of the end-effectors but also guarantees the accomplishment of the sub-task control. The efficiency of the proposed control algorithm is validated showing a number of numerical simulations.     

Development of a Flying Robot With a Pantograph-Based Variable Wing Mechanism

We develop a flying robot with a new pantograph-based variable wing mechanism for horizontal-axis rotorcrafts (cyclogyro rotorcrafts). A key feature of the new mechanism is to have a unique trajectory of variable wings that not only change angles of attack but also expand and contract according to wing positions. As a first step, this paper focuses on demonstrating the possibility of the flying robot with this mechanism. After addressing the pantograph-based variable wing mechanism and its features, a simulation model of this mechanism is constructed. Next, we present some comparison results (between the simulation model and experimental data) for a prototype body with the proposed pantograph-based variable wing mechanism. Both simulation and experimental results show that the flying robot with this new mechanism can generate enough lift forces to keep itself in the air. Furthermore, we construct a more precise simulation model by considering rotational motion of each wing. As a result of optimizing design parameters using the precise simulation model, flight performance experimental results demonstrate that the robot with the optimal design parameters can generate not only enough lift forces but a 155 gf payload as well.