Stability of a discrete closed-loop system which includes a Kalman filter†

This paper describes a method of determining the stability at the sampling instants, of a discrete closed-loop system which includes a Kalman filter. This is done by determining the z-plane poles of a special augmented transition matrix. While this result stems from stochastic optimal control work, the method applies to any, not just optimal, values of the feedback matrix, M, and filter feedforward matrix K. It is still applicable when the filter model and the plant are dissimilar in coefficient values and order.     

一类离散混沌系统的脉冲时滞反馈控制

为了镇定一类离散混沌系统的不稳定周期轨道,提出脉冲时滞反馈控制方法.系统地研究了脉冲时滞反馈控制方法在一类离散小世界网络模型中的应用问题.数值仿真结果表明,小世界网络模型中的倍周期分岔及其导致的混沌可以被延后,镶嵌在混沌吸引子内部的不稳定周期轨道可以被镇定.与已有相关控制方法相比,所提出的脉冲时滞反馈控制方法具有适用范围广泛、实现过程简单方便且灵活等优势.     

Design of a fault tolerated intelligent control system for a nuclear reactor power control: Using extended Kalman filter

In this paper an approach based on system identification is used for fault detection in a nuclear reactor. A continuous-time Extended Kalman Filter (EKF) is presented, which allows the parameters of the nonlinear system to be estimated. Also a fault tolerant control system is designed for the nuclear reactor during power changes operation. The proposed controller is an adaptive critic-based neuro-fuzzy controller. Performance of the controller in terms of transient response and robustness against failures is very good and considerable.     

Lump localisation through a deformation-based tactile feedback system using a biologically inspired finger sensor

The ability to localise harder areas in soft tissues is often desired during robot-assisted surgical operations. A deformation-based tactile feedback system was tested for the detection of objects within soft tissues, after being chosen over common pressure-based designs. This system uses a biologically inspired sensor that offers a new finger-like approach to tactile sensing. A tactile shape display developed from previous successful designs was used to output the sensed tactile information. Using the tactile feedback system on a mechanical teleoperated device, test subjects palpated a number of artificial tissue models to locate objects of varying stiffness. The addition of the tactile feedback system improved the detection of the objects from 64% to 98%, reduced the localisation error from 18 to 11 mm, and also decreased the time the users spent palpating the tissue from 55 to 37 s. This demonstrates that a deformation-based tactile feedback system can be used to successfully locate hard embedded objects within soft tissue, with a significant improvement over force and visual feedback alone. During testing, it was found that the users were able to more accurately locate the softest embedded objects compared to stiffer ones. Reasons for this observation are discussed.     

Development of a sensor system for collecting tactile information

This paper presents the development of a sensor system for collecting tactile information. An active sensing system using the piezoelectric effect and the pyroelectric effect of a PVDF (Polyvinylidene fluoride) film is proposed. The active sensing is designed with human motions for tactile perception in mind. First, as the pretest, the distinction examination of six fabrics with different textures is carried out through human tactile perception. Next, the proposed sensor system is assembled. The sensor is composed of a PVDF film and a soft rubber. The surface of the sensor can be heated through temperature control. The sensor is attached on the tip of a robot finger driven by a piezoelectric bimorph strip and the root of the finger is mounted on a linear slider. Two kinds of active sensing are introduced. First, the heated sensor is contacted with an object and pyroelectric output signals are collected in order to obtain the information on tactile warmth. Next, the heated sensor is slid over the object and piezoelectric output signals are collected in order to obtain the information on feelings of vibration. Through the discussion about each sensing, three indexes representing features of the collected data are extracted and proposed as the sensor outputs for the evaluation of tactile sensation. The measurement using the sensor system is done on the samples used in the distinction examination. Comparison with the results shows that the sensor system extracts features on feelings of vibration and warmth.     

A multi-robot positioning system using a multi-code ultrasonic sensor network and a Kalman filter

In multi-robot systems, each robot needs to have the position and pose information of itself and that of the other cooperative robots. This paper presents a synchronous distributed positioning system that uses a multi-code ultrasonic sensor network and a compensation algorithm using a Kalman filter. The bearings of robots are computed by using their position changes, and then compensated for by using the Kalman filter. The ZigBee sensor network protocol is used for communication among the robots and for the synchronization of the ultrasonic transmission timing. The experimental results show that our system positions multiple robots synchronously without any configured infrastructures. The results have a better accuracy and less accumulative error than those found in positioning systems without compensation.     

A receding horizon Kalman FIR filter for discrete time-invariantsystems

A receding horizon Kalman FIR filter is presented that combines the Kalman filter and the receding horizon strategy when the horizon initial state is assumed to be unknown. The suggested filter is a FIR filter form which has many good inherent properties. It can always be defined irrespective of singularity problems caused by unknown information about the horizon initial state. The suggested filter can be represented in either an iterative form or a standard FIR form. It is also shown that the suggested filter possesses the unbiasedness property and the remarkable deadbeat property irrespective of any horizon initial condition. The validity of the suggested filter is illustrated by numerical examples     

卡尔曼滤波焊缝跟踪控制

在视觉传感的电弧自动焊接过程中,需要根据视觉信息来控制电弧准确地跟踪焊缝.由于强烈的弧光干扰,使得从焊接区图像中直接提取电弧与焊缝的偏差信息十分困难.为此提出一种利用熔池图像质心和卡尔曼滤波来间接获取电弧与焊缝偏差的方法.选择熔池图像质心作为状态向量,建立基于图像质心的状态方程和焊缝位置测量方程.利用卡尔曼滤波消除过程噪声和测量噪声的影响,通过对熔池图像质心的状态估计,准确获取焊缝位置以及电弧与焊缝之间的偏差量,为自动焊接过程的焊缝跟踪控制提供准确信息.焊接试验结果表明,利用卡尔曼滤波方法可有效降低过程噪声和测量噪声的影响,从而提高焊缝跟踪控制精度.     

Design of a feedback control system for real-time control of flow in a single-screw extruder

The topic of this paper is the design and experimental testing of a prototype feedback control system for the regulation of the volumetric flow in a polymer single-screw extruder. Flow regulation is achieved by means of joint regulation of the temperature and the pressure at the die. The overall controller architecture is constituted by three control sub-tasks: the inner-loop control of the local temperatures along the barrel; the outer-loop control of the temperature at the extruder output; the control of the pressure at the extruder output. In this work, the whole design procedure (modeling, controller design, and testing) is presented. Extensive tests have shown that the system reacts rapidly to changes in the operating conditions and effectively rejects disturbances due to unexpected changes in the quality of the material. The achieved regulation provides very small steady state errors both for pressure and temperature. Moreover, it is shown that this control system is a cost-effective alternative to mechanical volumetric pumps.     

An exact solution of the time-invariant discrete Kalman filter

An exact solution is presented of the matrix Riccati difference equation associated with a time-invariant discrete Kalman filter. The time-varying solution is expressed by means of the corresponding steady-state algebraic solution. An exact solution of the closed-loop transition matrix is also presented.     

基于卡尔曼滤波CMAC-PID的视力检查距离控制系统

为提高视力检查的精确性和灵活性,设计了视力检查距离控制系统对检查距离进行有效控制,并建立了数学模型。针对该系统的非线性、时变性和多干扰性,提出基于卡尔曼滤波器的小脑神经网络与比例—积分—微分复合控制(CMAC-PID)方法,利用卡尔曼滤波器抑制测量噪声和控制干扰的影响。仿真结果表明,此控制方法在抗干扰方面优于CMAC-PID控制,可以更好地改善距离控制系统的性能。     

Robust bin-picking system using tactile sensor

ABSTRACT

This paper presents a robust bin-picking system utilizing tactile sensors and a vision sensor. The object position and orientation are estimated using a fast template-matching method through the vision sensor. When a robot picks up an object, the tactile sensors detect the success or failure of the grasping, and a force sensor detects the contact with the environment. A weight sensor is also used to judge whether the lifting of the object has been successful. The robust and efficient bin-picking system presented herein is implemented through the integration of different sensors. In particular, the tactile sensors realize rope-shaped object picking that has yet to be made possible with conventional picking systems. The effectiveness of the proposed method was confirmed through grasping experiments and in a competitive event at the World Robot Challenge 2018.     

凹槽滤波反馈控制混沌系统

通过对具有扰动作用的平面Hamilton混沌动力系统增加一线性的反馈控制器———凹槽滤波器, 基于Melnikov方法这一混沌的微扰判据给出合适的反馈控制器参数, 引导系统从混沌运动转化为期望的低周期运动, 并采用平均理论作了稳定性分析. 数值仿真结果将进一步证实本文的结论.     

Regions of pole location of the discrete stationary Kalman filter

Two regions are found inside the complex unit circle that exclude all the poles of the discrete stationary Kalman filter. The sizes of these regions depend on the ratio between the intensities of the signal and the measurement noise, and in the limit where this ratio tends to infinity, one of the regions shrinks to the origin.     

基于柔性触觉传感器的坐姿压力监测系统设计

提出了一种有效监测人体坐姿压力的系统,设计了柔性触觉传感器阵列,基于多路模拟开关CD4051、微处理器MSP430与无线发送模块实现数据的采集与传输,在上位机软件中通过低通滤波、配色与插值算法,并应用分布式压缩感知理论,形成了模拟人体坐姿压力分布的彩色图像,图像真实清晰,便于观察.实验结果表明:系统稳定性和分辨率较好,且能够实现坐姿压力分布的实时测量和显示.     

基于加速度传感器反馈的丝杠传动系统接触力控制

针对丝杠传动系统从自由空间运动过渡到约束空间力控制过程中,接触不同环境刚度时接触力的动态特性是不同的,并且存在冲击、高频振动甚至不稳定,以及稳态力跟踪阶段的扰动引起的不稳定问题,提出用加速度传感器反馈来增加系统力控制的阻尼,抑制在力控制的接触过渡过程和力维持跟踪过程中因为碰撞和外部扰动等原因产生的高频振动,克服单纯速度反馈控制带宽比较窄的局限性,增加系统的稳定性.建立了基于多传感器的实验平台,进行了接触力控制的实验比较研究,实验结果表明该方法是可行的.     

Robust discrete nonlinear feedback control for robotic manipulators

Nonlinear feedback control algorithms for manipulators utilize a complete (coupled and nonlinear) dynamic robot model to decouple the robot joints. In the companion article¹ we outlined the practical problems introduced by modeling inaccuracies, unmodeled dynamics and parameter errors. We then introduced the α-computed-torque nonlinear feedback control algorithm which is robust in the presence of the aforementioned error sources. In this article, we apply the insight gained from the α-computed-torque algorithm to design a robust discrete-time (accelerometer-free) computed-torque robot-control algorithm founded upon our discrete dynamic robot model.² Numerical experiments with the cylindrical robot confirm both the robust disturbance rejection characteristics and the practical applicability of our discrete-time computer-torque control algorithm.     

基于卡尔曼滤波的两轮平衡姿态检测系统设计

针对传统两轮平衡检测系统易受噪声等环境因素影响,导致测量产生误差的现象,提出基于卡尔曼滤波的两轮平衡系统设计。选择SCA610-CA1H1G型号姿态传感器,以MEMS技术为基础设计姿态传感器结构,具备可选择的多种数据输出模式。选取36V电源将3个12V12AH的铅酸电池利用串联在一起,为系统提供充足电源。设计主控芯片Pentium II/III/4系列CPU,将它的状态信息描述和对外输出。设计基于卡尔曼滤波的去噪流程,构建误差修正模型,通过四元数转旋转矩阵转移到当前设备坐标系上处理,由此获取姿态矩阵从本体坐标系旋转到另一个坐标系的过程,对测量数值进行归一化处理,可得到无量纲标量。使用定时采样三阶逼近法,更新四元数,完成姿态检测。由实验结果可知,无论是在0-15dB噪声环境,还是15-30dB噪声环境下,系统监测精准度最高为92%,为汽车、航天领域提供设备支持。