Alternative interpretation of rotation rate sensing by ring laser

This paper deals with the laser rotation rate sensor, sometimes also referred to as laser gyroscope, which was most extensively investigated by Macek and co-workers at Sperry Gyroscope. The function of rotation sensing is first discussed for a ring resonator of circular shape. It is seen that in that case the standing wave electromagnetic energy distribution remains stationary while the cavity structure with an attached detector is rotated so that the detector samples standing waves. Thus, rotation sensing is linked with the fact that Maxwell's equations are valid for inertial reference frames or equivalently, with the inertial nature of electromagnetic radiation. The concept of inertia is then used to derive the ring laser equation for arbitrary ring shape. It is hoped that these viewpoints offer a more elementary understanding of rotation sensing through ring lasers than other available derivations.     

Optical rotation sensing by the geometric effect of fiber-loop twisting

An optical technique for sensing a rotation angle is described and experimental results are presented. When a loop of an ideal fiber that exerts no linear birefringence is deformed into a nonplanar curve, the azimuth angle of linearly polarized light propagated in the fiber is rotated. The technique is based on this effect of geometric polarization rotation in an optical fiber. A twisted single-mode fiber is substituted for the ideal fiber. Experimental results include studies of polarization rotation and variations of light propagated in a loop of a twisted single-mode fiber under deformation.     

Modeling and control of the Mitsubishi PA-10 robot arm harmonic drive system

The purpose of this paper is to present our results in developing a dynamic model of the Mitsubishi PA-10 robot arm for the purpose of low-velocity trajectory tracking using low-feedback gains. The PA-10 is ideal for precise manipulation tasks because of the backdrivability, precise positioning capabilities, and zero backlash afforded by its harmonic drive transmission (HDT). However, the compliance and oscillations inherent in harmonic drive systems, and the lack of any technical information on the internal dynamics of the transmission, make the development of an accurate dynamic model of the robot extremely challenging. The novelty of this research is therefore the development of a systematic algorithm to extract the model parameters of a harmonic drive transmission in the robot arm to facilitate model-based control. We have modeled all seven joints of the Mitsubishi PA-10, and we have done several experiments to identify the various parameters of the harmonic drive system. We conclude with a sample trajectory-tracking task that demonstrates our model-based controller for the Mitsubishi PA-10 robot arm.     

Redundancy resolution of the human arm and an upper limb exoskeleton

The human arm has 7 degrees of freedom (DOF) while only 6 DOF are required to position the wrist and orient the palm. Thus, the inverse kinematics of an human arm has a nonunique solution. Resolving this redundancy becomes critical as the human interacts with a wearable robot and the inverse kinematics solution of these two coupled systems must be identical to guarantee an seamless integration. The redundancy of the arm can be formulated by defining the swivel angle, the rotation angle of the plane defined by the upper and lower arm around a virtual axis that connects the shoulder and wrist joints. Analyzing reaching tasks recorded with a motion capture system indicates that the swivel angle is selected such that when the elbow joint is flexed, the palm points to the head. Based on these experimental results, a new criterion is formed to resolve the human arm redundancy. This criterion was implemented into the control algorithm of an upper limb 7-DOF wearable robot. Experimental results indicate that by using the proposed redundancy resolution criterion, the error between the predicted and the actual swivel angle adopted by the motor control system is less then 5°.     

Intelligent optimal control of single-link flexible robot arm

This paper addresses the design and properties of an intelligent optimal control for a nonlinear flexible robot arm that is driven by a permanent-magnet synchronous servo motor. First, the dynamic model of a flexible robot arm system with a tip mass is introduced. When the tip mass of the flexible robot arm is a rigid body, not only bending vibration but also torsional vibration are occurred. In this paper, the vibration states of the nonlinear system are assumed to he unmeasurable, i.e., only the actuator position can be acquired to feed into a suitable control system for stabilizing the vibration states indirectly. Then, an intelligent optimal control system is proposed to control the motor-mechanism coupling system for periodic motion. In the intelligent optimal control system a fuzzy neural network controller is used to learn a nonlinear function in the optimal control law, and a robust controller is designed to compensate the approximation error. Moreover, a simple adaptive algorithm is proposed to adjust the uncertain bound in the robust controller avoiding the chattering phenomena. The control laws of the intelligent optimal control system are derived in the sense of optimal control technique and Lyapunov stability analysis, so that system-tracking stability can be guaranteed in the closed-loop system. In addition, numerical simulation and experimental results are given to verify the effectiveness of the proposed control scheme.     

Hybrid force-velocity sliding mode control of a prosthetic hand

Four different methods of hand prosthesis control are developed and examined experimentally. Open-loop control is shown to offer the least sensitivity when manipulating objects. Force feedback substantially improves upon open-loop control. However, it is shown that the inclusion of velocity and/or position feedback in a hybrid force-velocity control scheme can further improve the functionality of hand prostheses. Experimental results indicate that the sliding mode controller with force, position, and velocity feedback is less prone to unwanted force overshoot when initially grasping objects than the other controllers.     

Fault-tolerant control system of flexible arm for sensor fault by using reaction force observer

In recent years, control system reliability has received much attention with increase of situations where computer-controlled systems such as robot control systems are used. In order to improve reliability, control systems need to have abilities to detect a fault (fault detection) and to maintain the stability and the control performance (fault tolerance). In this paper, we address the vibration suppression control of a one-link flexible arm robot. Vibration suppression is realized by an additional feedback of a strain gauge sensor attached to the arm besides motor position. However, a sensor fault (e.g., disconnection) may degrade the control performance and make the control system unstable at its worst. In this paper, we propose a fault-tolerant control system for strain gauge sensor fault. The proposed control system estimates a strain gauge sensor signal based on the reaction force observer and detects the fault by monitoring the estimation error. After fault detection, the proposed control system exchanges the faulty sensor signal for the estimated one and switches to a fault-mode controller so as to maintain the stability and the control performance. We apply the proposed control system to the vibration suppression control system of a one-link flexible arm robot and confirm the effectiveness of the proposed control system by some experiments.     

Theory of magnetostatic waves in moving ferrite films andapplications to rotation rate sensing

A first-order field theory for electromagnetic waves in moving ferrites and ferrite thin films is presented. The dominant effect of the motion is found to be the Doppler-shifted frequency observed in the moving frame. This gives rise to an anomalously large shift in wavenumber, due to the dispersive nature of the ferrite medium. Because of the large effect, it is suggested that a moving-medium experiment using magnetostatic waves could be used to distinguish between various competing forms for the dispersion term in the Fresnel-Fizeau coefficient. The results of the field theory are discussed with relation to relative and absolute rotation rate sensing. The author describes how magnetostatic waves could be used to measure relative rotation rates if confined to propagate around the perimeter of a rotating disk. Since the phase shift would be established in the time required to propagate around the disk, the response time could be significantly shorter than conventional tachometers. An experiment with counterpropagating magnetostatic waves is suggested to clarify the effect of a magnetic medium on the magnitude of the Sagnac effect     

Characterization of residual information for SeaWinds quality control

Recent work has shown the important properties of the wind inversion residual or maximum-likelihood estimator (MLE) for quality Control (QC) of QuikSCAT Hierarchical Data Format (HDF) observations. Since March 2000, the QuikSCAT near-real-time (NRT) Binary Universal Format Representation (BUFR) product is available. As this product is used for numerical weather prediction (NWP) assimilation purposes, a QC procedure for the BUFR product is needed. We study the behavior of the MLE in order to determine whether the HDF QC procedure is appropriate for BUFR data. A comparison using real HDF and BUFR data reveals that the MLE distributions of HDF and BUFR differ and are actually poorly correlated. One important difference between BUFR and HDF is the amount of signal averaging prior to wind inversion. The averaging reduces the number of observations used in the wind retrieval for the BUFR product as compared to HDF. We show with a simple example that different MLE distributions are indeed expected due to this averaging. We also run a simulation in order to link theory and reality and better understand the behavior of the MLE. Despite the different MLE behavior in BUFR and HDF, the quality of the retrieved winds, as compared with the European Centre for Medium-Range Weather Forecasts winds, is very similar. We develop an MLE-based QC procedure for BUFR, similarly to the one in HDF, and we compare both. The skill of the QC in BUFR is again very similar to the one in HDF, showing that despite the different MLE behavior in both formats, the properties of the MLE as a QC indicator remain very similar.     

Modeling and iterative learning control of spatially distributed parameter systems with sensing and actuation over a selected area of the domain

Multidimensional Systems and Signal Processing - This paper gives new contributions to the development of iterative learning control for distributed parameter systems, based on using finite...     

Quantifying proprioceptive reflexes during position control of the human arm

This study aimed to analyse the dynamic properties of the muscle spindle feedback system of shoulder muscles during a posture task. External continuous force disturbances were applied at the hand while subjects had to minimize their hand displacements. The results were analysed using two frequency response functions (FRFs) from which the model parameters were derived, being 1) the mechanical admittance and 2) the reflexive impedance. These FRFs were analysed by a neuromusculoskeletal model that implicitly separates the reflexive feedback properties (position, velocity and acceleration feedback gains) from intrinsic muscle visco-elasticity. The results show substantial changes in estimated reflex gains under conditions of variable bandwidth of the applied force disturbance or variable degrees of external damping. Position and velocity feedback gains were relatively larger when the force disturbance contained only low frequencies. With increasing damping of the environment, acceleration feedback gain decreased, velocity feedback gain remained almost constant and position feedback gain increased. It is concluded that under the aforementioned circumstances, the reflex system increases its gains to maximize the mechanical resistance to external force disturbances while preserving sufficient stability.     

基于语音信号的嵌入式假肢控制系统研究

文中以凌阳SPCE061A单片机作为核心控制芯片,研究了一种基于语音信号的嵌入式假肢控制系统.该控制系统主要由声音采集和音频输出构成,通过语音命令就能够实现对假肢的多自由度运动控制,弥补了基于EMG和EEG控制系统的不足,并且提高了假肢控制系统的识别率,实现了语音信号对假肢的控制.     

CPLD在智能感应照明控制系统中的应用

针对传统LED照明开关控制模糊等缺陷,设计了CPLD智能照明控制系统。首先介绍采用CPLD进行智能感应照明控制系统的工作原理,分析软硬件设计思路以及遇到的问题。实验表明,智能控制系统改善了传统控制开关的缺陷,能够可靠工作,实现照明的智能控制。     

Modeling and control of a six-axis precision motion control stage

This work presents a newly developed six-axis magnetic suspension stage for precision motion control. The designed travel volume is 4/spl times/4/spl times/2 mm in translation and 1/spl deg//spl times/1/spl deg//spl times/2/spl deg/ in rotation. A dynamic model of the feedback linearized and uncoupled stage is developed for the purpose of motion control. Model parameter variations are demonstrated through closed-loop system identification. In motion control, a parameter variation model is proposed in conjunction with a reduced order observer to compensate the joined effect of disturbance, modeling error, and cross coupling. Experimental results in terms of positioning stability, motion resolution, rotational motion control, model regulation, large travel multiaxis contouring, and disturbance rejection are shown. Uniform positioning stability and invariant dynamic response within the designed travel volume are illustrated.     

基于体感控制的智能车设计

智能车设计中远程端及控制端采用单片机作为主控制器,远程端即小车端接收到控制端发送过来的控制信号,实现自身转向、姿态变换等动作,姿态传感器安装在人的手背上作为控制端,通过无线装置将相关参数传输到小车上的接收装置,接收器接收到相应参数后,处理器执行相应滤波算法,发送指令,从而实现远程遥控。设计中按照低功耗、高精度原则进行器件选型,主控制器部分、电机驱动等硬件电路设计力求经济性和精简性。软件设计充分发挥软件控制灵活方便的特点,实现了小车的平稳性和精确变换姿态等功能,所实现的智能车可应用于医疗、娱乐等各个领域。     

User-modulated impedance control of a prosthetic elbow in unconstrained, perturbed motion

Humans use the agonist-antagonist structure of their muscles to simultaneously determine both the motion and the stiffness of their joints. Designing this feature into an artificial limb may prove advantageous. To evaluate the performance of an artificial limb capable of modulating its impedance, we have created a compact series elastic actuator that has the same size and similar weight as commercially available electric prosthetic elbows. The inherent compliance in series elastic actuators ensure their safety to the user, even at high speeds, while creating a high-fidelity force actuator ideally suited for impedance control. This paper describes three serial studies that build on each other. The first study presents modeling of the actuator to ensure stability in the range of impedance modulation and empirically tests the actuator to validate its ability to modulate impedance. The actuator is found to be stable and accurate over a wide range of impedances. In the second study, four subjects are tested in a preliminary experiment to answer basic questions necessary to implement user-modulated impedance control. Findings include the superiority of velocity control over position control as the underlying motion paradigm and the preference for high stiffness and non-negative inertia. Based on the findings of the second study, the third study evaluates the performance of 15 able-bodied subjects for two tasks, using five different impedance paradigms. Impedance modulation, speed, and error were compared across paradigms. The results indicate that subjects do not actively modulate impedance if it is near a preferred baseline. Fixed impedance and viscosity modulation provide the most accurate control.     

Modeling and control of a humanoid robot

This work deals with modeling of humanoid robots, especially for planning motion using the Denavit-Hartenberg method to determine the inverse kinematics of used trajectory (Matlab/Simulink and SimMechanics). The simulations are applied to an existing robot, in order to determine the optimal trajectory for the robot motion.     

码垛机器人机械臂仿真控制系统设计与实现

随着科技的飞速发展,企业的生产能力大幅提高,传统的人工码垛已经不能满足企业对物流的需求,码垛机器人技术应运而生。高效率的码垛能够大大节省物流时间,提高工作效率。系统利用四轴码垛机械臂仿真控制软件实际控制一台小型的关节型四轴码垛机械臂。机械臂利用舵机作为执行元件,DSP作为控制器控制舵机运动。仿真控制软件根据规划的路径计算出码垛过程中舵机运行的角度,通过串口通信将角度数据传递给DSP,DSP控制舵机的运行并带动码垛机械臂实现码垛功能。