基于二阶矩阵微分方程的机械振动系统线性二次型调节器设计

本文讨论机械振动系统线性二次型状态调节器（LQR）问题，直接针对系统二阶运动微分方程，性能指标为一个依赖于二阶导数的泛函。由欧拉-拉格朗日方程得出一个系统矩阵增广的二阶线性微分方程，指出该方程稳定的特征对就是最优控制振动系统闭环特征对，并给出求解最优控制状态反馈矩阵的方法，另外，由本文方法还可得出基于速度和加速度反馈的最优控制反馈矩阵。这里不涉及求解代数矩阵Riccati方程。     

Stability of General Linear Dynamic Multi-Agent Systems under Switching Topologies with Positive Real Eigenvalues

The time-varying network topology can significantly affect the stability of multi-agent systems. This paper examines the stability of leader–follower multi-agent systems with general linear dynamics and switching network topologies, which have applications in the platooning of connected vehicles. The switching interaction topology is modeled as a class of directed graphs in order to describe the information exchange between multi-agent systems, where the eigenvalues of every associated matrix are required to be positive real. The Hurwitz criterion and the Riccati inequality are used to design a distributed control law and estimate the convergence speed of the closed-loop system. A sufficient condition is provided for the stability of multi-agent systems under switching topologies. A common Lyapunov function is formulated to prove closed-loop stability for the directed network with switching topologies. The result is applied to a typical cyber–physical system—that is, a connected vehicle platoon—which illustrates the effectiveness of the proposed method.     

A model for signal processing and predictive control of semi-active structural control system

The theory for structural control has been well developed and applied to perform excellent energy dissipation using dampers. Both active and semi-active control systems may be used to decide on the optimal switch point of the damper based on the current and past structural responses to the excitation of external forces. However, numerous noises may occur when the control signals are accessed and transported thus causing a delay of the damper. Therefore, a predictive control technique that integrates an improved method of detecting the control signal based on the direction of the structural motion, and a calculator for detecting the velocity using the least-square polynomial regression is proposed in this research. Comparisons of the analytical data and experimental results show that this predictor is effective in switching the moving direction of the semi-active damper. This conclusion is further verified using the component and shaking table test with constant amplitude but various frequencies, and the El Centro earthquake test. All tests confirm that this predictive control technique is effective to alleviate the time delay problem of semi-active dampers. This predictive control technique promotes about 30% to 40% reduction of the structural displacement response and about 35% to 45% reduction of the structural acceleration response.     

An accelerated iterative method for the dynamics of constrained multibody systems

An accelerated iterative method is suggested for the dynamic analysis of multibody systems consisting of interconnected rigid bodies. The Lagrange multipliers associated with the kinematic constraints are iteratively computed by the monotone reduction of the constraint error vector, and the resulting equations of motion are easily time-integrated by a well established ODE technique. The velocity and acceleration constraints as well as the position constraints are made to be satisfied at the joints at each time step. Exact solution is obtained without the time demanding procedures such as selection of the independent coordinates, decomposition of the constraint Jacobian matrix, and Newton Raphson iterations. An acceleration technique is employed for the faster convergence of the iterative scheme and the convergence analysis of the proposed iterative method is presented. Numerical solutions for the verification problems are presented to demonstrate the efficiency and accuracy of the suggested technique.     

Modified input estimation technique for tracking manoeuvring targets

A new input estimation (IE) model for problems in tracking manoeuvring targets is proposed. The proposed model is constructed by combining the two models of uncertainties, Bayesian and Fisher. The conventional model, which describes targets with manoeuvre, is based on the state vector of target position and velocity. The acceleration is treated as an additive input term in the corresponding state equation. The proposed method is a Kalman filter-based tracking scheme with the IE approach. The proposed model is a special augmentation in the state-space model which considers both the state vector and the unknown input vector as a new augmented state vector. In the proposed scheme, the original state and acceleration vectors are estimated simultaneously with a standard Kalman filter. The proposed tracking algorithm operates in both the non-manoeuvring and the manoeuvring modes and the manoeuvre detection procedure is eliminated. The theoretical development is verified by simulation results, which also contain some examples of tracking typical target manoeuvres. The results are compared with a traditional IE method. A comparison based on the Monte-Carlo simulation is also made to evaluate the performances of the proposed method in three scenarios: low, medium and high manoeuvring target.     

基于增量耦合预测控制的风电叶片打磨机械臂末端颤振抑制研究

针对风电叶片打磨过程中,末端执行器与叶片表面发生刚性接触而引起末端执行器切向颤振问题,提出一种基于力反馈与加速度前馈复合结构的末端执行器增量耦合预测控制方法。在末端执行器柔性驱动单元数学建模的基础上,基于增量耦合动态矩阵预测控制算法对复合PID控制策略进行改进,将不可控但可预知输入加速度作为磨削轴向力预测序列的一部分。同时,在有限时域内采用二次型性能指标最小化的方式对控制目标进行滚动优化,以确保末端执行器与风电叶片表面柔顺接触。仿真及实验结果表明,此方法可以快速地实现末端执行器的切向颤振抑制,并能最大限度地减小因控制时滞、环境时变、模型失配等带来的误差。     

On the possibility of a collective acceleration of ions in a magnetically insulated vircator in the regime of a traveling distributed virtual cathode boundary

A new scheme for the acceleration of ions by a traveling distributed virtual cathode boundary is proposed. Operation of the scheme is based on the phenomenon according to which an electron beam with a density exceeding a certain threshold exhibits a transition into the so-called compressed state. This state is characterized by a small velocity, a large electron density, and the developed turbulence of the opposite flows. The results of numerical calculations are presented.     

Development of a hybrid negotiation scheme for multi-agent manufacturing systems

A hybrid inter-agent negotiation mechanism based on currency and a pre-emption control scheme is proposed to improve the performance of multi-agent manufacturing systems. The multi-agent system considered consists mainly of four types of agents: machine, clone, part and mediator. The machine agent controls the scheduling and the execution of a task. The clone agent aims to maximize the utilization rate by attracting relevant work to the machine. The part agent communicates with the machine agent or clone agent to acquire necessary production resources in order to get the required processing done, and the mediator agent contains the status of the part that will be processed by the subcontracting machine agent. The primary objective is to design decentralized control protocols for discrete part manufacturing systems to enhance the efficiency of the system and to allocate dynamically the resources to critical jobs based on the dynamic search tree. This research incorporates both the currency and the pre-emption schemes within a common framework. Currency functions are used to help the agents meet their individual objectives, whereas the pre-emption scheme is used to expedite the processing of parts based on their due dates. A dynamic search algorithm for the best route selection of different operations based on the job completion time is also proposed and it is implemented on a small manufacturing unit.     

Economic oriented stochastic optimization in process control using Taguchi’s method

The optimal operating region of complex production systems is situated close to process constraints related to quality or safety requirements. Higher profit can be realized only by assuring a relatively low frequency of violation of these constraints. We defined a Taguchi-type loss function to aggregate these constraints, target values, and desired ranges of product quality. We evaluate this loss function by Monte-Carlo simulation to handle the stochastic nature of the process and apply the gradient-free Mesh Adaptive Direct Search algorithm to optimize the resulted robust cost function. This optimization scheme is applied to determine the optimal set-point values of control loops with respect to pre-determined risk levels, uncertainties and costs of violation of process constraints. The concept is illustrated by a well-known benchmark problem related to the control of a linear dynamical system and the model predictive control of a more complex nonlinear polymerization process. The application examples illustrate that the loss function of Taguchi is an ideal tool to represent performance requirements of control loops and the proposed Monte-Carlo simulation based optimization scheme is effective to find the optimal operating regions of controlled processes.     

Instantaneous optimal control with acceleration and velocity feedback

In the experimental demonstration of aseismic control systems, difficulties were encountered in the measurement of the displacement response of the structure. During earthquake ground motions, both the building and the ground are moving so that there is no absolute reference for the determination of the displacement response. An optimal control algorithm is proposed herein, which utilizes the measurements of acceleration and velocity responses rather than the displacement and velocity measurements. Such an optimal algorithm is developed based on the instantaneous optimal control theories, and it is evaluated and compared with other available optimal control laws. Numerical results indicate that the performance of the proposed optimal algorithm is as good as that of other optimal control laws currently available. However, the contribution of such an optimal control law to the practical implementation of active control systems for seismic hazard mitigations may be quite significant.     

Optimal input design for online parameter estimation for aircraft with multiple control surfaces

An optimal input design method is proposed for online parameter estimation for aircraft with multiple control surfaces. The optimal input is designed considering the input and output constraints. These constraints are constructed based on a military standard, MIL-STD-8785C, viz., the flying qualities of a piloted aircraft. The accuracy of parameter estimation using the optimal input is compared with that of parameter estimation using conventional doublet/3211 inputs. Two online parameter estimation schemes are also considered to evaluate the performance of the designed optimal input: a Bayesian method based on the time domain and an equation-error method based on the frequency domain. The recursive form of the Bayesian method is also derived. Numerical simulations are performed, and the performance, convergence, and accuracy of two online parameter estimation schemes are compared.     

振动主动控制中电磁作动器动态特性的研究

分析了电磁作动器的动态特性及其对振动主动控制系统振动传递率的影响。振动传递率不仅受作动器动态特性的影响,而且还与反馈变量的选取有关。因此,在实际控制系统中应选择绝对位移、速度、加速度及加加速、绝对位移的积分和相对位移、速度、加速度及加加速度、相对位移的积分的不同组合作为反馈变量,以期取得良好的隔振效果。     

跟踪系统中多闭环控制模式的分析和实现

实现高精度跟踪,尤其在外界干扰力矩下,必须增加系统刚度来提高系统的扰动抑制能力.提出将加速度反馈引入常规的跟踪系统控制方式中,实现了由电流环、加速度环、速度环、位置环构成的四闭环控制模式.高增益的加速度反馈为系统提供一个响应更快、带宽更宽的内环,克服了单纯速度反馈带宽窄的特性.首先从理论上分析和证明了该方法的意义,多闭环控制模式可以提高系统的刚度,从而增强系统的抗扰动能力;同时,在加速度反馈的基础上研制前馈控制器,能够进一步提高大速度目标的跟踪性能.在某一实际的系统中对多闭环控制模式进行了实验验证,结果表明:同以往的控制方法相比扰动抑制带宽由15 Hz 提高到30 Hz ;并且在10 Hz 以下频率获得了-30 dB 抑制能力.     

负载加速度反馈的伺服系统谐振抑制

谐振常常造成伺服系统不稳定,影响其控制性能.首先建立光电控制系统的动力学方程,分析了谐振和反谐振产生的原因.伺服系统同样也受到反谐振的影响,并且反谐振出现在谐振之前.由于间隙和摩擦的影响,谐振往往会随之变化,很难用固定的陷波器去补偿.提出一种负载加速度反馈控制算法减小谐振的影响,由此形成三闭环控制模式.根据提出的加速度反馈算法3条准则设计加速度控制器,采用此控制方法速度闭环带宽提高了5Hz左右,谐振峰减小了15dB.并且200Hz以后的谐振迅速衰减,提高了系统的稳定性.     

Agent-based manufacturing control based on distributed bid selection and publish-subscribe messaging: a simulation case study

Bidding-based negotiation schemes play a major role in multi-agent manufacturing systems research. Despite some concerns with message congestion, researchers have been proposing and studying negotiation schemes based on the contract net protocol (CNP). On the other hand, research in robotics has considered a variant of CNP based on publish-subscribe messaging designed for multi-robot coordination. A distinct feature of this variant involves distributing the bid evaluation and selection functions among robot agents. This paper discusses our adaptation of this design variant for multi-agent manufacturing systems and examines its performance implications. Using discrete-event simulation, we study how the adapted CNP design can help address the message congestion problem by cutting down on negotiation slack time. Our case study results show that it can enhance the resilience of the agent negotiation process to message congestion, thereby contributing to the overall performance of a multi-agent manufacturing system.     

Digital Instrumentation for Angular Velocity and Acceleration

An instrument is described for the measurement of angular velocity and angular acceleration of a rotating shaft, based upon an optical angular transducer and an associated operational digital (pulse rate) system. The angular transducer produces a pulse rate directly proportional to the instantaneous angular velocity and this quantity and its rate of change are processed by the pulse rate system and presented as parallel binary-coded decimal representations driving in-line digital displays. The operational digital system comprises essentially an electronic register controlling a variable rate pulse generator that tracks the input pulse rate in a frequency lock loop. Changes of loop frequency are brought about by changing the register contents by positive or negative correction pulses, and the rate at which these are supplied provides an accurate measure of acceleration or deceleration, respectively, provided that the loop is locked on and hence follows the changes of input pulse rate accompanying changes of angular velocity. The error correction pulse rate may be measured in a second frequency lock loop and the registers in the two loops used to control digital in-line decimal displays of angular velocity and acceleration, of ranges up to 10 000 r/min (±1 r/min) and 1000 r/min/s (±1 percent), respectively.     

Formal verification of negotiation protocols for multi-agent manufacturing systems

Formal verification is an important means of tackling behavioural problems such as deadlocks in multi-agent systems. This paper is concerned with the role played by formal verification in the simulation-based performance analysis of multi-agent manufacturing systems. A discrete-event simulation case study is presented to show how varying certain timing parameters of the agent negotiation protocol affects the performance of a multi-agent manufacturing system as well as the chance of getting deadlocks among the software agents. When one tries to determine the optimal values of these timing parameters based on the simulation results, formal verification can help refine the results by confirming whether deadlocks among software agents are indeed possible for particular parameter values. This involves modelling the system's real-time behaviour according to the simulation model and applying the techniques and tools of model checking.     

A stabilized numerical solution for the dynamic contact of the bodies having very stiff constraint on the contact point

For the numerical analysis of dynamic contact problem where the contact constraint is imposed by a very stiff massless spring between the bodies, it is shown that a stabilized time integration solution can be obtained without spurious oscillations by imposing the velocity and acceleration constraints as well as the displacement constraint on the contact point. For the velocity and acceleration contact constraints which are crucial for the numerical stability, the time derivatives of the spring deformation are computed by using the Newmark time integration rule of structural dynamics. With the numerical experiments the necessity of the velocity and acceleration contact constraints and the necessity of unconditionally stable time integration rule for the very stiff spring are demonstrated.     

A New Anti-Quantum Proxy Blind Signature for Blockchain-Enabled Internet of Things

Blockchain technology has become a research hotspot in recent years with the prominent characteristics as public, distributed and decentration. And blockchain-enabled internet of things (BIoT) has a tendency to make a revolutionary change for the internet of things (IoT) which requires distributed trustless consensus. However, the scalability and security issues become particularly important with the dramatically increasing number of IoT devices. Especially, with the development of quantum computing, many extant cryptographic algorithms applied in blockchain or BIoT systems are vulnerable to the quantum attacks. In this paper, an anti-quantum proxy blind signature scheme based on the lattice cryptography has been proposed, which can provide user anonymity and untraceability in the distributed applications of BIoT. Then, the security proof of the proposed scheme can derive that it is secure in random oracle model, and the efficiency analysis can indicate it is efficient than other similar literatures.     

Electronic ballast for multiple fluorescent lamp systems

An electronic ballast for multiple tubular fluorescent lamp systems is presented. The proposed structure has a high value for the power factor, a dimming capability, and soft switching of the semiconductor devices operated at high frequencies. A zero-current switching pulse width modulated SEPIC converter is used as the rectifying stage and it is controlled using the instantaneous average input current technique. The inverting stage consists of classical resonant half-bridge converter with series-resonant parallel-loaded filters. The dimming control technique is based on varying the switching frequency and monitoring the phase shift of the current drained by the filters and lamps in order to establish a closed loop control. Experimental results are presented that validate the theoretical analysis.