Linear motor motion control using a learning feedforward controller

The design and realization of an online learning motion controller for a linear motor is presented, and its usefulness is evaluated. The controller consists of two components: (1) a model-based feedback component, and (2) a learning feedforward component. The feedback component is designed on the basis of a simple second-order linear model, which is known to have structural errors. In the design, an emphasis is placed on robustness. The learning feedforward component is a neural-network-based controller, comprised of a one-hidden-layer structure with second-order B-spline basis functions. Simulations and experimental evaluations show that, with little effort, a high-performance motion system can be obtained with this approach     

On the approximation by truncated sampling series expansions

In this note we point out in which way the approximation of not necessarily bandlimited functions by sampling series is injured by additional truncation. We will also show how the rate of convergence is influenced by the features of the underlying kernel function.     

An optimal and adaptive design of the feedforward motion controller

The zero phase error tracking controller (ZPETC) in motion control, as proposed by Tomizuka (1987) , renders the desirable zero phase error, but with a limited gain response. Moreover, a ZPETC, which is basically in a feedforward control structure, is very sensitive to modeling error. To improve the tracking accuracy of the ZPETC, this paper presents an optimal ZPETC design with a concise polynomial digital prefilter (DPF). The parameters of this well-designed DPF are obtained through the derived L₂-norm optimization. By cascading the developed DPF to the ZPETC, the resultant optimal ZPETC greatly improves the bandwidth of the tracking control systems while maintaining the zero phase error. Compared with other optimal approaches, the present design leads to much simpler procedures and fewer computations. Furthermore, the proposed optimal ZPETC can be adequately implemented as an adaptive ZPETC by including real-time estimation technique to cope with the external load perturbation and parameter variation. Compared with the other adaptive approaches, the optimal concept is used in the present adaptive ZPETC, and it also renders more accurate results because of its improved magnitude response. Experimental results on a DC servo table with different controllers indicate that when there is no loading, the present optimal ZPETC achieves the best tracking performance. Moreover, the adaptive ZPETC achieves the most satisfactory results when an external load is applied     

High-speed and high-precision motion control with an optimal hybrid feedforward controller

An optimal feedforward controller which makes a hybrid usage of the shift (q) and delta (/spl delta/) operators is proposed for high-speed and high-precision digital motion control systems. Uncancellable discrete-time zeros arising from sampling the continuous-time plant at high rates, which make the mathematical inverse unstable, are handled in a natural way. The controller is optimized to have good performance in both low and high frequency ranges, and it is able to handle uncancellable discrete-time zeros in the right half plane. The optimization problem is generalized to an H/sup /spl infin// problem. Convex minimization is used to find the solution to the optimization problem. Simulation results and experiments carried out on an MC-510V Matsuura vertical machining center show superior performance of the proposed optimal hybrid feedforward controller.     

Soft eigenvalue assignment with limited disturbance feedforward and state controller norm

The method of softly assigning eigenvalues is attractive for design problems where constraining the control effort and disturbance feedforward is more important than following the exact pole location.     

利用改进微分进化算法实现线性系统逼近

提出一种基于改进的微分进化算法的逼近算法。新算法通过参考粒子群算法惯性权重思想,引入惯性加权系数,在计算初期能够维持个体的多样性,后期能够加快算法的收敛速度,提高了DE算法的性能。最后对典型的稳定线性系统逼近问题进行了数值计算,计算结果证明该算法优于未改进微分进化算法,能够以更少的进化代数和更小的计算量找到高质量的逼近模型。     

Particle swarm optimization based feedforward controller for a XY PZT positioning stage

Compensations for cross-axis coupling effect and hysteretic nonlinearity of a novel XY piezo-actuated positioning stage are presented in this study. The piezo-actuated stage utilizes a monolithic flexure-based mechanism (FBM) to achieve translations in X- and Y-axes instead of using stacked mechanisms. A hysteresis model with crossover term is proposed to alleviate the cross coupling effect between X- and Y-stages during precision positioning tasks. System identifications using real-coded genetic algorithm (RGA) and clonal selection algorithm (CSA) are compared with particle swarm optimization (PSO). The results show that PSO provides better performance than the others. Therefore, a feedforward controller with cross-axis coupling compensation is studied and the used for the piezo-actuated FBM to enhance the precision of the coarse positioning stage. The experimental results confirm that the proposed controller can achieve precision tracking tasks with submicron precision.     

System reduction by Routh approximation and modified Cauer continued fraction

An algorithm is proposed for obtaining stable reduced-order models using Routh stability criterion and matching moments and Markov parameters, via the modified Cauer continued fraction.     

A modified offered load approximation for nonstationary circuit switched networks

In this paper, we develop approximation methods to analyze blocking in circuit switched networks with nonstationary call arrival traffic. We formulate generalizations of the pointwise stationary and modified offered load approximations used for the nonstationary Erlang loss model or M(t)/M/c/c queue. These approximations reduce the analysis of nonstationary circuit switched networks to solving a small set of simple differential equations and using the methods for computing the steady state distributions for the stationary versions of such loss networks. We also discuss how the use of time varying arrival rates literally adds a new dimension to the class of telecommunication networks we can model. For example, we can model the behavior of alternate routing due to link‐failure, which is a feature that the classical stationary version of the model cannot capture. Our nonstationary model can also describe aspects of the dynamic calling traffic behavior arising in cellular mobile traffic. For the special case of a two‐link, three node network, we present numerical results to compare the various approximation methods to calculations of the exact blocking probabilities. We also adapt these calculations to approximate the behavior of rerouting calling traffic due to link‐failure. The results are achieved by formulating some new recursions for evaluating the steady state blocking probabilities of such networks. We also generalize these techniques to develop analogous formulas for a linear N‐node circuit switched network. This revised version was published online in June 2006 with corrections to the Cover Date.     

Embedding a feedforward controller into the IGBT gate driver for turn-on transient improvement

This paper proposes an active gate drive method based on a feedforward control for turn-on condition in IGBTs. The transient improvement with minimum undesirable effect on the efficiency is the main objective of this research. The new gate driver (GD) improves the trade-off between switching loss and device stress at the turn-on condition, without getting feedback from the output. The operation principle and implementation of the controller in the GD are presented. The effect of the proposed GD on the transient behaviour, efficiency, junction temperature and electromagnetic interference (EMI) during turn-on switching is evaluated by both simulation and experimental tests. The new GD is evaluated under hard switching condition and various frequencies. Advantages and disadvantages of the method have been discussed.     

A wide-band feedforward amplifier

The design of a wide-band feedforward amplifier in the frequency range 30-300 MHz is described. Expressions are derived for feedforward amplifier sensitivity, and the effect of imperfect loop cancellation is described. The effect of circuit imbalance on gain and terminal impedances is investigated. The circuit is realized in thin-film hybrid form, and measurements show 20 dB of distortion improvement at 300 MHz. Practical aspects of circuit adjustment and operation are considered.     

Uniform approximation with doubly finite Volterra series

The assumption that a system possesses a certain discrete-time Volterra series representation frequently forms the basis for studies in the areas of signal processing and communication theory. A further assumption often made, always without discussion, is that the representation can be suitably approximated by a corresponding `double finite' series. It is shown that, for a very large class of nonlinear discrete-time systems, such doubly finite approximations exist in the sense of uniform approximation on a ball of bounded inputs. Several additional results are also given. These concern, for example, asymptotic properties of the expansions. The results provide a more firm foundation for applications involving Volterra series     

MIMO multirate feedforward controller design with selection of input multiplicities and intersample behavior analysis

Inversion-based feedforward control is a basic method of tracking controls. The aim of this paper is to design MIMO multirate feedforward controller that improves continuous-time tracking performance in MIMO LTI systems considering not only on-sample but also intersample behavior. Several types of MIMO multirate feedforward controllers are designed and evaluated in terms of the 2-norm of the control inputs. The approach is compared with a conventional MIMO single-rate feedforward controller in simulations. The approach improves the intersample behavior through the optimal selection of input multiplicities with MIMO multirate system inversion.     

A three-axis vibration isolation system using modified zero-power controller with parallel mechanism technique

This paper proposes a module-type three-degree-of-freedom vibration isolation system using modified zero-power control. Three vibration isolation modules are connected together using parallel mechanism to control 3-DOF motions. Each module consists of a common base, an individual middle mass and a common isolation table. The base to the middle mass is suspended by positive springs generated by active and passive system, and the middle mass and the isolation table is connected by negative spring realized by active-type modified zero-power control. The developed system could realize zero-compliance to direct disturbances as well as good ground vibration isolation. Furthermore, the isolation table is supported by a weight support mechanism for supporting heavy payloads. In the previous research, a concentrated middle mass with redundant actuators, in the vertical and horizontal directions, were used. Therefore, a vibration isolation system is proposed in this work using modular concept to overcome those drawbacks. Each module is controlled separately by decentralized control technique, and three modules can be used for three-degree-of-freedom of motion control. Therefore, no redundancy of actuator is occurred. Moreover, an improved zero-power controller is presented that can adjust negative stiffness instead of conventional zero-power controller. The results obtained from analytical and experimental studies show that the modular technique is reliable and efficient approach to vibration control, and represents a suitable alternative to the conventional active vibration isolation systems.     

Computer-based controller design for quantum boost series resonant rectifier

To obtain a stable output voltage from a recently-developed rectification circuit called a quantum boost series resonant rectifier (QBSRR), two control schemes, digital PI (proportional-integral) control and deadbeat control, are derived for a computer-based system. Since the output voltage regulation loop has a sampling time corresponding to the zero crossing point of the AC line voltage, the output voltage can be controlled regardless of the 120 Hz ripple component. By deriving a simple and exact model for the current program loop (open loop) of a QBSRR and using the pole-assignmenl technique, the controller gains can be systematically designed in the digital PI control scheme. The deadbeat control scheme is also developed to maintain fast dynamic performance in the presence of any load variations. In this control scheme, the controller gain is adjusted in accordance with the load information using a load estimation method. Simulation and experimental results are presented to verify the usefulness of these two control schemes.     

A feedforward S-band MIC amplifier system

A 2.2 GHz high-power feedforward amplifier system has been designed and fabricated, which has an RF gain of 30 dB and delivers an output power of 1.25 W with all IM distortion products at least down 50 dB from the carrier level. The power amplifiers and passive circuit components used in this system are all realised in thin-film hybrid form. The theoretical development of the system is described. The result of the temperature stability tests is given. The computer optimisation technique with multiband weighting functions used throughout the amplifier design process is presented. Finally, practical applications and a comparison of the advantages and drawbacks of this (feedforward) amplifier system with those produced by using the conventional (back-off) approach are discussed.     

Implementation of a neural controller for the series resonantconverter

A neural controller implementing an energy feedback control law is proposed as an alternative to classic control of resonant converters. The properties of the energy feedback control, and particularly the optimal trajectory control law, are analyzed. As a result, the state space is considered to be divided into two subspaces, that correspond to different states of the switches in the converter. An analog neural network learns to classify these two classes by means of a learning algorithm. A simple electronic implementation of this controller is proposed and applied to a series resonant converter (SRC). Results based on prototype measurements show a good improvement in the SRC response versus classical control methods based on the linearization of the state variable equations around a working point and confirm the validity of the neural approach     

Current-mode pseudo-exponential-control variable-gain amplifier using fourth-order Taylor's series approximation

A new current-mode pseudo exponential-control variable-gain amplifier (VGA) using CMOS technology is proposed. The technique is based on the fourth-order Taylor's series approximation. The VGA exhibits a linear-dB controllable output range of 30 dB with maximum error less than 0.5 dB.     

Robust controller design for a series resonant converter viaduty-cycle control

Robust controller design for a series resonant power converter is presented when load variation and unregulated input line voltage perturbation are taken into consideration. The perturbation of unregulated line voltage is treated as an exogenous disturbance and the load variation as a structured uncertainty of the converter. An averaged model, including disturbance and model uncertainty, is then derived. Two kinds of μ synthesis-D-K and μ-K iteration schemes-are applied to design robust controllers to diminish the susceptibility of the regulated voltage to perturbations of load variation and unregulated line voltage. In addition, a classical controller is also designed for performance comparison. Finally, simulations and experimental results are presented to verify the feasibility of the robust control theory