A 3‐DOF Inchworm Using Levitation Caused by Vertical Vibration

We propose a 3‐DOF inchworm‐type microactuator that uses levitation generated by vertical vibration. The vertical vibration is created by a piezoelectric actuator. The inchworm typically consists of thrust elements and clamp elements. The proposed inchworm, however, does not use any clamp elements. Four levitation elements are connected with four thrust elements, which are stacked‐type piezoelectric actuators. The levitation element consists of a mass, a piezoelectric actuator, and a plate. The vertical vibration of the piezoelectric actuator lifts the levitation elements, which eliminates any friction. By controlling the order of the deformation of the horizontal piezoelectric actuators and the vibration of the vertical piezoelectric actuators, the inchworm engages in linear and rotational motion. The levitation height and the linear and rotational displacement of the inchworm were measured. Experimental results demonstrated the feasibility of the proposed 3‐DOF inchworm. The mechanism described in this paper is effective for a precision positioning system in a clean room.     

行走式尺蠖压电直线驱动器研究现状及关键技术综述

尺蠖压电驱动器具有大行程、高精度、大输出力、快速响应、无磁场影响等优点,在超精密定位领域具有广泛的应用前景。而行走式尺蠖压电驱动器又以箝位机构结构简单、刚度和动态性能好,中间驱动机构偏摆小,整体体积小,运动稳定性好等特性引起世界各国的关注。在阐述行走式尺蠖压电驱动器的本质、组成结构及运动原理的基础上,对其国内外研究现状及其关键技术进行了分析,并对其发展趋势进行了展望。     

Improvement of sensing characteristics of self‐sensing active magnetic bearings

A winding‐current interference model of self‐sensing magnetic bearings (AMBs) and an improvement technique of position‐sensing characteristics are proposed. In the self‐sensing AMB systems, the electromagnets work not only as actuators suspending the rotor but also as position sensors. The self‐sensing position signal, however, includes errors because of nonlinearity of the magnetic circuits. In the proposed model, the current is directly transmitted to the self‐sensing position signal. This transmission means degradation of the self‐sensing characteristics. This winding‐current interference to the self‐sensing signal is reduced by the proposed compensation method. The characteristics of the proposed self‐sensing method agree well with a reference sensor signal up to over 1 kHz. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(2): 70– 77, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20732 Copyright © 2004 Wiley Periodicals, Inc.     

Self‐sensing active magnetic bearings with zero‐bias‐current control

A zero‐bias‐current self‐sensing active magnetic bearing is proposed. One degree‐of‐freedom (DOF) of the rotor is controlled by a pair of electromagnets which are alternatively energized by the proposed circuit. The rotor position of the one DOF is measured by using both electromagnets: the nonenergized electromagnet also contributes to the position sensing. The proposed method gives good linearity in the position estimation. The controller of the magnetic levitation consists of a digital signal processor, DSP, which compensates the nonlinearity of the magnetic force and achieves good damping. In the experiment, the rotor can run at 45,000 min^‐1. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(2): 69–76, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20616     

Dynamic Characteristics Analysis of Two‐DOF Oscillatory Actuator and Experimental Verification of Prototype

Recently, linear oscillatory actuators have been used in a wide range of applications. In particular, small linear oscillatory actuators are expected to be used in haptic devices by being extended to provide multi‐degree‐of‐freedom motion with arbitrary acceleration. In this paper, we propose a compact two‐DOF oscillatory actuator that can move in various directions on a plane. The static and dynamic characteristics of the actuator are determined by the 3D finite element method. The effectiveness of this method is shown through a comparison of the measured results with the experimental results from a prototype. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(1): 58–65, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22312     

Quadratic modeling of wheeled moving platforms on planes

Planar motion of wheeled moving platforms, on which a camera is installed to capture videos, is common in real‐world scenarios. For a general planar motion, Scaramuzza et al. proposed a linear one‐point model to recover motions from a video under a potential assumption that the camera needs to be placed somewhere between the rear wheels of a moving platform. However, the assumption is too restricted for researchers and manufacturers, because the camera is generally fixed either on the front top of vehicles for a broad view or near the left/right mirrors because of the requirement of mechanical design. In this paper, we focus on motion modeling of wheeled moving platforms without the restriction of cameras' location on a vehicle, and propose a quadratic motion model to circumvent the limitation. Newton's iterative method and bounded quadratic least squares are used to solve the quadratic optimization problem. We test our model on both the synthetic data and the real data, and conclude that the tradeoff between model error and computational error and that between performance and computational cost are the main concerns in the practice of visual odometry. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

磁控形状记忆合金蠕动型直线电机研究

磁控形状记忆合金(MSM)是一种新型具有形状记忆功能的合金材料，不仅变形率大，易于控制，动态响应速度高，而且功率密度大和机电能量转换效率高，特别适合于制造高精度的运动与位置控制执行器。该文首先介绍MSM材料在磁场作用下的变形机理与磁控特性，然后分析利用仿生学蠕动原理将MSM小步距的位移累加形成直线电机所需要的大行程的工作原理，而后论述蠕动型MSM直线电机的设计与控制方法，最后给出样机的试验结果。     

一种新型磁悬浮直线运动平台的热分析

为实现定位平台的大运动行程和高运动精度,建立了一种新型磁悬浮直线运动平台,该平台由磁悬浮运动装置和电磁直线驱动装置组成,具有无摩擦、高刚度等优点.针对磁悬浮直线运动平台长时间运行过程中电磁铁的发热问题,运用有限元软件对电磁铁的发热机理、发热量以及热量的时空分布进行了分析,并和实验数据进行了对比.结果表明,在常温常压下,电磁铁温度上升到一定程度后即达到平衡,不需要加装冷却装置.而在真空环境下,电磁铁温度会不断增加,必须加装冷却装置来降低温度.最后,通过仿真对真空环境下的冷却装置设计进行了简单地讨论.     

Studies on thrust characteristics of high‐thrust spiral motor

Linear actuators are used in various industrial applications. Conventional linear actuators are a combination of a rotational motor and a ball screw, a hydraulic actuator, or a linear motor. However, these actuators have some demerits. This paper proposes a spiral motor (SPRM) that comprises a helical stator and a helical mover. Owing to its helical structure, the SPRM can be expected to show better performance compared to the conventional linear actuator. A stator and a mover are shown in Figs. 1 and 2, respectively. Helical motion is obtained by this motor and only linear motion is extracted by canceling rotational motion at the end effector. There are two types of SPRMs. One has no ball screw on the output axis, while the other has a ball screw. The former can be used in a direct drive system. However, the gap between the stator and the mover should be controlled because the motor is a magnetic levitation system without a ball screw. Further, the motor requires two three‐phase inverters. The other motor is easy to control because it does not require gap control. However, the motor is inferior to the first motor with regard to position control since the friction in this motor is larger. In this study, a prototype of the SPRM is developed. The prototype constructed is a motor with a ball screw. In this motor, the stator and mover are made of block cells. The stator block is shown in Fig. 3 and the mover block is shown in Fig. 4. The prototype of the SPRM shown in Fig. 5, is developed by using these two blocks. An experiment is conducted to examine the driving of the SPRM. The experimental result is shown in Fig. 6. From this result, it is evident that comprising a helical stator and a helical mover can generate linear motion. Another experiment is conducted for measuring the thrust characteristic of the motor. The result obtained is shown in Fig. 7. From the figure, the thrust constant of the spiral motor, K_f, is obtained as 538.0 N/A. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(2): 58–64, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21168     

用于大范围纳米级压电微动台的驱动控制系统

介绍了一种基于尺蠖运动原理大范围纳米级步距压电微动工作台。根据其运动原理特点,设计完成了该压电微动台的控制系统。在电压控制下,利用压电陶瓷的逆压电效应,通过机械装置将压电陶瓷的微小位移输出,达到精密定位的目的。最后对该控制系统进行了性能测试。实验表明,该控制系统所产生的三角波、方波信号纹波电压小,信号稳定,其中放大电路部分放大倍数为57,能够驱动所选用的压电陶瓷,满足微动台驱动要求。     

提高蠕动式压电直线驱动器输出力的研究进展

蠕动式压电直线驱动器具有大位移行程和高位移分辨率的特点,但是箝位机构利用静摩擦力输出负载的方式大大限制了系统的进给刚度和输出推力.从箝位机构的结构类型、运动方式以及和新材料新技术的交叉应用等方面,介绍了几种典型尺蠖驱动器的研究进展,为提高系统的输出力,指出了今后的研究方向.     

一种新型三自由度微定位新方法

设计了一种基于压电陶瓷的三维微定位系统,通过12个空间分布的压电陶瓷微驱动器及4个工作平台的配合,实现X、Y、Z向的精密位姿控制.阐述了微定位原理、建立了载物台位姿与压电陶瓷微驱动器伸缩量之间的关系,介绍了系统误差来源以及微定位装置的构造.该研究可望为一些高科技领域的微进给提供实用新技术.     

离合器箝位型尺蠖驱动器研究及发展

按箝位方式对尺蠖驱动器进行分类.介绍了尺蠖驱动器箝位机构从主动箝位到楔箝位再到楔辊子箝位以及螺旋楔箝位的发展过程;指出传统主动箝位的不足及楔箝位和楔辊子箝位各自的优缺点;介绍了螺旋楔箝位的特点及需要完善发展的方向,指出离合器箝位型尺蠖驱动器是高性能精密直线驱动器的一个重要发展方向.     

Parameter design of event‐driven logic controller for two‐wheeled vehicle

Programmable Logic Controllers (PLCs) are widely used in industry. In PLC‐based control systems, low‐resolution (especially ON‐/OFF) sensors are inexpensive, and actuators are commonly used because they are compatible with programming languages used in PLCs. PLC switches the actuators ON/OFF as the state of the sensor changes between ON/OFF. In designing PLC‐based systems, the design of the parameters of these sensors and actuators (e.g., position of limit switches and torque of motors) is an important problem because they affect the overall performance of the system. This problem, however, has not yet been fully discussed. In the present paper, a systematic design method for this problem is developed. The main concept is to express the model of the system as a Mixed Logical Dynamical System (MLDS) and to formulate the problem as a mathematical programming problem. The developed idea is applied to the line‐following control of a two‐wheeled vehicle. The usefulness of the proposed method is demonstrated through simulation and experiments. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(2): 51–60, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20584     

Image‐based visual target following for a nonholonomic wheeled mobile robot with a single fixed camera

This paper addresses the problem of visual target following for a nonholonomic wheeled mobile robot with a single fixed camera. For the problem, we propose a control scheme composed of vision‐based trajectory planning and tracking control. We present online trajectory planning based on image‐based visual servoing. The key idea is to compensate the target object motion. In particular, we focus on visual feature motion resulting from the target object motion. Tracking control to the generated trajectory can therefore achieve visual target following precisely even if the target object is moving. Our proposed scheme can be applied to, e.g. robotic systems for autonomous guard and observation. The effectiveness of the control system is evaluated experimentally. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Real‐time compensation for positioning performance using on‐line parameter identification and initial value compensation

Variations and/or uncertainties in environments of mechatronic systems, such as electrical/mechanical parameter changes and nonlinear components, generally deteriorate the motion control performance. In our research, the fast and precise position settling performance for parameter variations in positioning devices can be improved by techniques of an on‐line parameter identification and an initial value compensation. The proposed technique allows the positioning systems to be adaptive and robust for unknown parameter variations. The effectiveness of the approach has been verified by numerical simulations and experiments using a prototype. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(2): 40–49, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20926     

Experiment and simulation of micro‐part dynamics with roughness effect

In this study, we perform an experiment and develop a dynamic model that describes the planar motion modes of a micro‐part, including two linear motions and one rotational motion, on a saw‐tooth surface. In the experiment, the planar motion of the micro‐part is obtained by a particle‐tracking method. The rotation angle is measured from the principal axis of the micro‐part image. In a simulation, the contact between the micro‐part and the saw‐tooth surface is assumed to be the contact between a number of hemispheres on the micro‐part and the surface, which results in either a point contact or a slope contact. The effect of the saw‐tooth surface's roughness on the contact force at each contact point is modeled as a field of normal vectors. In addition, the roughness of the saw‐tooth surface is approximated by superposing white noise on an ideal saw‐tooth profile and is used to evaluate the adhesion force. The results show that the model can describe the motion modes of a micro‐part. Furthermore, the simulated results of the two linear motions are in good agreement with our experimental results from a previous study. The proposed model can be used to improve the design of surfaces for micro‐part transport. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

三自由度永磁同步平面电机的控制策略

在介绍三自由度平面电机的结构和工作原理之后,提出执行器的电磁力方程和平面电机的运动控制方程,推导合外力和执行器水平电磁力的转换方程,提出平面电机的三自由度解耦控制策略.设计三个自由度的位置伺服控制算法,进行单自由度定位和三自由度同时定位实验.平移运动的上升时间为0.1 s,稳态误差为10 μm,旋转运动的上升时间为0....     

Control Method for Harmonic Voltage Injection to Achieve Noise Reduction in Position‐Sensorless Control of Permanent‐Magnet Synchronous Motors at Low Speeds

In this study, we examine the relationship between harmonic voltage injection, acoustic noise, and position estimation performance in a PMSM when a position‐sensorless control method involving harmonic voltage injection is used at low speeds. Further, we propose a novel control method for voltage injection; this method can be used to reduce acoustic noise in the motor. The proposed control method is verified by performing numerical simulations and carrying out experiments using a four‐pole, 2‐kW, 2100‐rpm IPMSM (interior permanent‐magnet synchronous motor). © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(3): 49–56, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21246     

Cylinder pressure sensor‐based real‐time combustion phase control approach for SI engines

As one of most effective factors affecting the economy and emissions of internal combustion engines, the combustion phase can maximize performance by tracking its optimum reference. In this study, the combustion phase indicator CA50 is employed for the combustion control of spark‐ignited (SI) engines with the application of a cylinder pressure sensor. In order to suppress the influence of cylinder pressure variation on CA50 measurement, a moving average method is used to stabilize CA50 calculation, and based on measured CA50, a linear autoregressive model is obtained by identification, which depicts the relationship between spark advance and combustion phase. Then, a closed‐loop controller is synthesized for CA50 regulation, including both feedforward and feedback channels. Finally, the proposed strategy is validated by experiments on an SI engine. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.