Intelligent gaze control for vision-guided humanoid walking: methodological aspects

This article presents methodological aspects of a scheme for visually guided humanoid robot navigation. The proposed approach is based on the maximization of the predicted visual information. For the information management a coupled hybrid Extended Kalman Filter is employed. Specific view direction evaluation strategies for conflicting objectives of different nature such as obstacle avoidance and self-localization, have to be weighted and pursued in parallel. A combination of both objectives shows the task dependence of the gazing strategy. A major goal of this work is to formalize and implement a decision making strategy in order to achieve an intelligent task-oriented active vision system for a biped walking robot. Simulation results based on experimental experience with real biped robots demonstrate the relevance of the approach.     

Application of active noise control to an elevator cabin

The elevators constructed today are getting faster and offer a high level of comfort. However, this increase in speed means more noise inside the cabin, and this noise is normally attenuated by passive methods, that is, by improving the cabin's insulation. Low-frequency noise persists, however, and it has to be dealt with by active techniques. This article describes the practical application of active noise control (ANC) to an elevator cabin, in order to reduce greatly the level of noise in the whole area. The results obtained are an advance towards the integration of ANC in elevators, and its commercialization.     

Multi-modal approach to evaluate adaptive visual stimuli of remote operation system using gaze behavior

A multi-modal approach is proposed to evaluate the usability of Adaptive Visual Stimuli for User Interface (AVS4UI) of remote operation systems. This study focuses on the evaluation of AVS4UI for forklift work because the operation complexity includes driving and cargo handling, which typically requires multiple salient attention. Presenting this amount of information simultaneously on a User Interface (UI) tends to cause confusions to operators and reduces operation efficiency. AVS4UI can therefore be one of the promising solutions where the optimal visual stimuli are autonomously presented for different work conditions. However, evaluation of AVS4UI is challenging because operators may be disoriented by adaptive information and worked without safety considerations. Therefore, novel gaze metrics are proposed to evaluate responses of forklift operators to AVS4UI so that undesired behavior can be evaluated. The proposed metrics implicitly represent gaze pattern in terms of transition and distribution between UI elements, operation safety, and familiarity with the adaptive system. The ideal AVS4UI is expected to minimize the proposed gaze metrics and outperform the non-adaptive UI. More importantly, the results of these metrics are consistent with those of perceived workload defined by NASA-Task Load Index. We also propose a correlation model using stepwise linear regression that provides reasonable estimation of perceived workload. Such novel metrics and correlation model enable objective and online evaluation to minimize biases of subjective response. Therefore, online work support system can be developed to support workers.     

Adaptive narrow band disturbance rejection applied to an active suspension—an internal model principle approach

This paper presents a methodology for feedback adaptive control of active vibration systems in the presence of time varying unknown narrow band disturbances. A direct adaptive control scheme based on the internal model principle and the use of the Youla-Kucera parametrization is proposed. This approach is comparatively evaluated with respect to an indirect adaptive control scheme based on the estimation of the disturbance model. The comparative evaluation is done in real time on an active suspension system.     

一种自适应振动主动控制策略及其在C型三维表面检测系统中的应用

基干广义最小方差和一步超前预报理论,围绕三维型面扫描系统中所存在的周期性徽振动问题,提出了一种新的自适应振动主动控制算法.以C型臂式三维激光扫描系统为应用背景,基于来自于该系统的数据样本建立了系统的振动动态自回归滑动平均模型(ARMA模型).采用所提出的自适应控制算法对该模型进行了振动主动控制仿真研究.仿真结果验证了所提出的方案可以有效地抑制C型臂运动过程中产生的振动,提高系统的整体三维检测精度.     

气动加载系统的积分型线性自抗扰控制

气动加载系统是复杂的非线性时变系统,可变参数和不确定性比较多,本文采用积分型线性自抗扰控制器(I--LADRC)对气动加载系统进行控制.自抗扰控制器(active disturbance rejection controller,ADRC)结构简单,不依赖于被控对象精确的数学模型,可以很好补偿被控系统内外各种不确定性.加入积分环节用来弥补ADRC在时变系统控制中存在的不足.在采用VC++6.0的工控试验平台上,将I--LADRC应用于气动加载系统中,分别在加载压力为恒值、方波和正弦波时进行空载和加载实验,并将得到的实验结果与PID控制算法进行比较,实验结果表明该控制算法不仅响应速度快,精度高,并且还具有较强的鲁棒性,具有良好的工程应用前景.     

Adaptive feedforward compensation algorithms for active vibration control with mechanical coupling

Adaptive feedforward broadband vibration (or noise) compensation is currently used when a correlated measurement with the disturbance (an image of the disturbance) is available. However in most of the systems there is a ”positive” mechanical feedback coupling between the compensator system and the measurement of the image of the disturbance. This may lead to the instability of the system. The paper proposes new algorithms taking into account this coupling effect and provides the corresponding analysis. The algorithms have been applied to an active vibration control (AVC) system and real time results are presented. A theoretical and experimental comparison with some existing algorithms is also provided.     

Guaranteed-cost active disturbance rejection control for uncertain systems with an integral controller

Guaranteed-cost active disturbance rejection control (ADRC) for uncertain systems is investigated in this study. Firstly, an integral action is introduced in the framework of ADRC to measure and reduce the tracking error. Then, a robust stability condition is presented, and a quadratic cost function where the tracking error is appearing explicitly is used for ADRC performance assessment. The cost bound is formulated by linear matrix inequality and optimised to obtain controller parameters. Full-dimension extended state observer is used, and thus, the proposed strategy is applicable to an uncertain system that allows relative-degree varying or right-half-plane zero. Finally, the validity of the proposed method and its advantages is demonstrated through the simulations of comparative examples and experiments on a motor speed control system.     

一种基于DSP＋MCU＋FPGA的APF控制系统设计

针对单片DSP实现有源电力滤波器的控制系统会延长控制周期,影响系统性能,本文设计了一种旗于DSP＋MCU＋FPGA的有源电力滤波器数字控制系统。MCU和FPGA分担了DSP的部分工作,使DSP最大限度的用于系统控制算法实现,提高了运算速度,满足有源电力滤波器控制系统的设计要求。仿真验征了基于DSP＋MCU＋FPGA的有源电力滤波器数字控制系统设计的可和性。     

Binormalized data-reusing adaptive filtering algorithm for active control of impulsive sources

The main objective of active noise control (ANC) is to provide attenuation for the environmental acoustic noise. The adaptive algorithms for ANC systems work well to attenuate the Gaussian noise; however, their performance may degrade for non-Gaussian impulsive noise sources. Recently, we have proposed variants of the most famous ANC algorithm, the filtered-x least mean square (FxLMS) algorithm, where an improved performance has been realized by thresholding the input data or by efficiently normalizing the step-size. In this paper, we propose a modified binormalized data-reusing (BNDR)-based adaptive algorithm for impulsive ANC. The proposed algorithm is derived by minimizing a modified cost function, and is based on reusing the past and present samples of data. The main contribution of the paper is to develop a practical DR-type adaptive algorithm, which incorporates an efficiently normalized step-size, and is well suited for ANC of impulsive noise sources. The computer simulations are carried out to demonstrate the effectiveness of the proposed algorithm. It is shown that an improved performance has been realized with a reasonable increase in the computational complexity.     

Adaptive complementary sliding-mode control for thrust active magnetic bearing system

An adaptive complementary sliding-mode control (ACSMC) system with a multi-input-multi-output (MIMO) recurrent Hermite neural network (RHNN) estimator is proposed to control the position of the rotor in the axial direction of a thrust active magnetic bearing (TAMB) system for the tracking of various reference trajectories in this study. First, the operating principles and dynamic model of the TAMB system using a linearized electromagnetic force model is derived. Then, a conventional sliding-mode control (SMC) system is designed for the tracking of various reference trajectories. Moreover, a complementary sliding-mode control (CSMC) system is adopted to reduce the guaranteed ultimate bound of the tracking error by half while using the saturation function as compared with the SMC. Furthermore, since the system parameters and the external disturbance are highly nonlinear and time-varying, the ACSMC is proposed to further improve the control performance and increase the robustness of the TAMB system. In the ACSMC, the MIMO RHNN estimator with estimation laws is proposed to estimate two complicated dynamic functions of the system on-line. In addition, a robust compensator is proposed to confront the minimum approximated errors and achieve the robustness. Finally, some experimental results for the tracking of various reference trajectories show that the control performance of the ACSMC is significantly improved comparing with the SMC and CSMC.     

Multi-channel active noise control for periodic sources—indirect approach

This paper presents a multi-channel active noise control algorithm that is designed to reject periodic signals of unknown frequency. It is based on a so-called indirect approach, where the frequency of the disturbance is estimated in real time, and the estimate is used in a disturbance rejection scheme designed for a known frequency. Improvements over an earlier algorithm include an extension to multi-channel systems, a better frequency estimation algorithm, and a thorough experimental evaluation. For disturbance rejection, a so-called inverse G algorithm is proposed and its properties are compared through analysis and experiments to those of a gradient algorithm. A new frequency estimator is also considered that is simple and flexible in design, and is able to use multiple harmonics or multiple signals in order to estimate the fundamental frequency of the noise source. In this manner, the algorithm maintains tracking of the fundamental frequency despite significant changes in signal characteristics. The ability of the indirect approach to reject periodic noise with fixed or time-varying frequency and amplitudes is demonstrated in active noise control experiments. The algorithm may also be useful in other control applications where periodic disturbances of unknown frequency must be rejected.     

Adaptive fuzzy backstepping control of three-phase active power filter

A backstepping controller (BC) and an adaptive fuzzy backstepping controller (AFBC) are proposed for three-phase active power filter (APF) in this paper. Firstly, the dynamic model for APF is build in which both the system parameter variations and external disturbance are considered. Then, the backstepping method is applied in the design of current control system to deal with the nonlinearity of APF. Moreover, the AFBC is developed by combining the backstepping approach with adaptive fuzzy strategy to attenuate the effect of parameter uncertainties and external disturbances. Fuzzy logic system is designed to estimate the unknown nonlinear function in the AFBC where the parameters are adjusted online by the adaptive law derived from the Lyapunov stability analysis to guarantee the tracking performance and stability of the closed-loop system. Simulation studies using the MATLAB/SimPower Systems Toolbox demonstrate that the proposed control strategies exhibit excellent performance in both steady state and transient operation.     

Real-time compliance control of an assistive joint using QNX operating system

An assistive robot is a novel service robot, playing an important role in the society. For instance, it can amplify human power not only for the elderly and disabled to recover/rehabilitate their lost/impaired musculoskeletal functions but also for healthy people to perform tasks requiring large forces. Consequently, it is required to consider both accurate position control and human safety, which is the compliance. This paper deals with the robot control compliance problem based on the QNX real-time operating system. Firstly, the mechanical structure of a compliant joint on the assistive robot is designed using Solidworks. Then the parameters of the assistive robot system are identified. The software of robot control includes data acquisition and processing, and control to meet the compliance requirement of the joint control. Finally, a Hogan impedance control experiment is carried out. The experimental results prove the effectiveness of the method proposed.     

Verification of an active control system using temporal process algebra

In this paper we describe complementary approaches that can be used to ensure the reliability of real-time systems, such as those used in active structural control systems. These approaches include both model-checking and simulation, and are based on a temporal process algebra. We combine these formal methods with a high-level, graphical modeling technique, Modechart, to specify an active structural control system consisting of several processors. Timing requirements on the system are specified and verified with a combination of process algebraic models and modal logic, and various simulation concepts are described for debugging models and for gaining insight into system behavior.     

机器人远程控制系统的实时仿真与实现

机器人远程控制随着互联网技术的发展逐渐成为目前的研究热点,它具有广泛的应用前景。由于互联网复杂性所带来的时延问题以及由此产生的安全问题是机器人远程控制的关键问题。设计和实现了一个基于互联网的机器人实时仿真和视觉反馈系统。首先,提出了基于状态反馈的实时仿真方法解决时延问题,以保证远程仿真机器人和本地服务器机器人的状态同步和机器人操作的安全性。其次,提出通过离线示教仿真之后再进行在线控制策略以及通过远程控制与本地自主控制的模式切换方法进一步地缩短在线操作时间和提高操作的安全性。最后,实验证明了基于互联网的实时仿真和视觉反馈系统的正确性和有效性。     

Ｓｔｅｗａｒｔ主动隔振平台的神经网络自适应控制

针对Stewart主动隔振平台,提出一种基于径向基函数(RBF)神经网络的多输入多输出自适应隔振控制方法.考虑外界振动对Stewart主动隔振平台动态特性的影响,建立了隔振平台在工作空间中的动力学模型.推导出RBF神经网络的权值矩阵、高斯基函数中心和宽度的在线自适应调节律,以使神经网络快速逼近系统的非线性动态函数.应用Lyapunov稳定性理论,证明了在扰动力和神经网络逼近误差有界的条件下,闭环控制系统滤波误差和RBF神经网络各调节参数估计误差的一致最终有界.仿真结果表明,该控制方法能有效地抑制不同方向的低频有界振动.     

Adaptive suboptimal control of a linear system with bounded disturbance

An adaptive suboptimal control of a linear discrete system with unknown parameters is proposed. An additive disturbance v_t acting on the system is supposed to be uniformly bounded. The criterion is sup_vtI(y^∞₁, u^∞₁), where y_t is the output, u_t is the control. The adaptive control law gives almost the same guaranteed value of the criterion as the optimal linear feedback does for a system with known parameters.     

Experimental validation of an active heave compensation system: Estimation,prediction and control

This work presents a comprehensive active heave compensation (AHC) approach proposing estimation, prediction and control methods. The estimation concept covers the estimation of the attitude using sensor fusion as well as the estimation of heave which is obtained by applying adaptive filtering methods. Moreover, a prediction approach based on a Levinson recursive least squares (RLS) algorithm is proposed. The actuation concept consists of a model predictive trajectory planner and a model-based Two-Degree-of-Freedom (2-DOF) controller. It is based on a model of the hydraulically driven compensation winch. The overall compensation performance as well as the estimation and prediction accuracy are evaluated using a full-scale AHC test bench.     

Real-time Design Constraints in Implementing Active Vibration Control Algorithms

Although computer architectures incorporate fast processing hardware resources, high performance real-time implementation of a complex control algorithm requires an efficient design and software coding of the algorithm so as to exploit special features of the hardware and avoid associated architecture shortcomings. This paper presents an investigation into the analysis and design mechanisms that will lead to reduction in the execution time in implementing real-time control algorithms. The proposed mechanisms are exemplified by means of one algorithm, which demonstrates their applicability to real-time applications. An active vibration control (AVC) algorithm for a flexible beam system simulated using the finite difference (FD) method is considered to demonstrate the effectiveness of the proposed methods. A comparative performance evaluation of the proposed design mechanisms is presented and discussed through a set of experiments.