Improvement of valve seating performance of engine’s electromagnetic valvetrain

The camless valvetrain is considered to be a promising solution to improve the engine performance. Most of the camless valvetrains suffer the problem of high impacts at valve seating, which restricts its mass production. This paper focuses on the valve seating performance of an electromagnetic valvetrain (EMVT) with moving coil linear actuator. The EMVT has inherent advantages to achieve low valve seating velocity. The seating performance of EMVT is evaluated by two indicators: seating velocity and holding force. To limit the seating velocity, the valve is controlled to track a desired trajectory based on inverse system method at seating process. The holding force is also properly controlled base on PID current control to ensure the cylinder sealed. The valve seating performance is validated on an experimental setup. The results show that excellent valve seating performance has been achieved.     

A sliding mode torque and position controller for an antagonistic SMA actuator

This paper presents position and torque control of an antagonistic setup for a shape memory alloy (SMA) rotary actuator using a sliding mode controller that takes into account the nonlinear behavior of SMA. The control scheme and model are based on the complete physics model of the system. An accurate model of the actuator is presented and validated by means of an experimental prototype. A nonlinear state observer is also developed in order to estimate temperature and phase state variables that are difficult to measure online due to the small dimensions of the actuator. Experimental results are then presented for different set-point functions. Tracking performance, frequency response and disturbance rejection are evaluated and the advantages of the proposed controller are then discussed.     

基于GRU神经网络的晶圆测试工艺控制方法

压电驱动器位移输出的非线性特性,如迟滞的记忆特性及速率相关性,使压电驱动器的建模与控制较难。该文提出了一种基于门控循环单元(GRU)的新型位移输出控制方法。建立相应的位移输出实验平台来验证和分析压电驱动器的滞后现象。使用GRU模拟滞后的内存特性及采用两个全连接层来模拟速率依赖性。该模型是一个端到端系统,其中压电陶瓷和位移放大机构被视为一个整体。针对不同电压输入预测的输出位移量表明,该模型对速率相关的滞后具有很强的泛化能力。使用相同的循环神经网络结构构建逆模型,并进行实验测试。实验结果表明,所提出的位移输出控制法有效地削弱了压电驱动器的非线性特性,有利于将线性系统控制法与前馈补偿法相结合。     

The reduction of stick-slip friction in hydraulic actuators

The stick-slip friction phenomenon is observed near zero relative velocity, during the transition from static to dynamic friction, when static friction is greater than dynamic friction. This nonlinear change in friction force over a small change in velocity results in difficulties in achieving accurate and repeatable position control. In some cases, the actuator position controller reaches a limit cycle (hunting effect). Friction compensation at low speeds has traditionally been approached through various control techniques. This paper proposes an alternative solution, namely, friction avoidance. By rotating the piston and rod, the Stribeck region of the friction-velocity curve is avoided and the axial friction opposing the piston movement is approximately linearized. Simulation and experimental results are presented to validate this approach.     

Closed-loop magnetic bearing and angular velocity control of a reaction sphere actuator

This article presents the first closed-loop magnetic bearing and angular velocity experimental results of a reaction sphere actuator for satellite attitude control. The proposed reaction sphere is a permanent magnet spherical actuator whose rotor is supported by magnetic bearing and can be torqued electronically about any desired axis. The spherical actuator is composed of an 8-pole permanent magnet spherical rotor and of a 20-pole stator with electromagnets. The electromechanical model of the reaction sphere is summarized together with procedures to estimate the rotor magnetic state, the back-EMF voltage, and the rotor angular velocity, which are all fundamental ingredients for controller design. Dynamic controllers are developed to levitate the rotor inside the stator (magnetic bearing) and to control the rotor angular velocity. The magnetic bearing is based on a state-space controller with reduced-order displacement velocity estimator whereas the angular velocity controller is a simple proportional controller with a dedicated angular velocity estimator. The developed control algorithms are experimentally validated using the developed laboratory prototype showing the ability of simultaneously levitating the rotor while rotating it about a given arbitrary axis.     

Active control of nonlinear noise processes in a linear duct

This paper investigates two scenarios in active noise control (ANC) that lead to performance degradation with conventional linear control techniques. The first scenario addresses the noise itself. The low-frequency noise, traveling as plane waves in a duct, is usually assumed to be broadband random or periodic tonal noise. Linear techniques applied to actively control this noise have been shown to be successful. However, in many practical applications, the noise often arises from dynamical systems, which cause the noise to be nonlinear and deterministic or stochastic, colored, and non-Gaussian. Linear techniques cannot fully exploit the coherence in the noise and, therefore, perform suboptimally. The other scenario is that the actuator in an ANC system has been shown to be nonminimum phase. One of the tasks of the controller, in ANC systems, is to model the inverse of the actuator. Obviously, a linear controller is not able to perform that task. To combat the problems, as mentioned above, a nonlinear controller has been implemented in the ANC system. It is shown in this paper that the nonlinear controller consists of two parts: a linear system identification part and a nonlinear prediction part. The standard filtered-x algorithms cannot be used with a nonlinear controller, and therefore, the control scheme was reconfigured. Computer simulations have been carried out and confirm the theoretical derivations for the combined nonlinear and linear controller     

A practical method for friction identification in hydraulic actuators

Friction in hydraulic actuators can be described using nonlinear, velocity dependent models. In this paper, the friction is described by an exponential Stribeck friction model. An iterative algorithm is presented to identify the friction model parameters. The method fits two lines on the experimental data relating steady-state velocities to actuator pressure differentials. The parameters of the fitted lines are obtained using an iterative optimization technique. Based on the obtained parameters, the original nonlinear friction model parameters are completely reconstructed. The proposed method is validated by building a simulation model for a valve-controlled hydraulic system in which the friction is modeled based on the method described here. The proposed method can be used in practical situations, whereby fast and reliable identification of major parameters of the friction in hydraulic actuators is needed with easy to obtained pressure measurements.     

斐索干涉仪中压电陶瓷的非线性校正

相移器是斐索干涉仪的核心部件,其关键为压电陶瓷(PZT)致动器,而其迟滞非线性特性严重影响了相移精度,对光学元件的形貌检测造成不利影响。该文首先设计了PZT的控制系统,利用National Instruments（NI）动态数据采集设备（PCIe 6321）、LabVIEW系统及电压放大器组成电压驱动系统产生驱动信号,利用电阻式应变仪、惠斯通电桥作为位移传感器采集位移;其次,提出了一种多项式模型及基于PZT传递函数的前馈开环校正算法对PZT进行建模及校正;最后,在实验系统上对该算法进行了验证。实验结果表明,校正后,相移器的相移误差可被改善,校正前、后位移差小于10%。该系统可有效校正非线性,从而降低非线性相移对测量结果的影响,满足检测光学元件面形的高精度要求。     

Precision positioning device utilizing impact force of combinedpiezo-pneumatic actuator

This paper reports on a new actuator combining both a piezoelectric actuator and pneumatic cylinder for the automatic assembly application. The results of fundamental experiments are presented and an analytical model is described. The experimental results show that the proposed actuator can move a target object with step sizes in the 10-nm order by utilizing the impact force of a piezoelectric element while maintaining the comparatively long operation range of a pneumatic cylinder. Furthermore, a 3-DOF positioning system had been constructed as a practical application. Due to the limited sensing range of the gap sensors, the positioning range is limited to ±1 mm, ±1 mm, and ±2 mrad along the 3-DOF. A heuristic control model is described. Using this model, a target object made of stainless steel (130×100×10 mm) was successfully positioned with an accuracy of ±0.5 μm, ±0.5 μm, and ±20 μrad along the 3-DOF. It is shown that the combined piezo-pneumatic actuator has attractive practical applications in the field of precision industry     

Theory of distributed mixing and amplification in a superconductingquasi-particle nonlinear transmission line

An analysis is presented for the behavior of the superconducting quasi-particle nonlinear transmission line driven by a high-frequency local oscillator (LO). The theory developed includes a large-signal nonlinear analysis, a small-signal analysis, and a noise analysis. This model is used to simulate the conversion loss and noise temperature of distributed quasi-particle mixers based on the nonlinear transmission line. The numerical results are compared to an experimental mixer at 460 GHz. The theory also predicts that the nonlinear transmission line will provide parametric amplification when the idler frequency is inductively tuned. This new phenomenon may present new opportunities to low-noise receiver systems at submillimeter wavelengths     

Nonlinear Tracking Control for a Hard Disk Drive Dual-Stage Actuator System

This paper presents a nonlinear tracking control method for a hard disk drive dual-stage actuator (DSA) system that consists of a voice coil motor (VCM) actuator and a piezoelectric (PZT) microactuator. Conventional track seeking controllers for DSA systems were generally designed to enable the VCM actuator to approach the target track without overshoot. However, we observe that this strategy is unable to achieve the minimal settling time when the target tracks are beyond the PZT actuator stroke limit. To further reduce the settling time, we design the VCM actuator controller to yield a closed-loop system with a small damping ratio for a fast rise time and certain allowable overshoot. Then, a composite nonlinear control law is designed for the PZT actuator to reduce the overshoot caused by the VCM actuator as the system output approaches the target track. Experimental results show that the proposed dual-stage servo outperforms the conventional dual-stage servo in short-span seeking and, additionally, achieves better track following accuracy than the VCM only single-stage servo.     

Benefits of amplification in an inertial stepping motor

Inertial stepping motors (ISMs) are widely used in high precision applications, such as scanning tunnelling microscopy and/or micro manipulation. The resolution they are able to reach makes them especially suitable when long stroke and high resolution are needed simultaneously. However, the limited speed of this technology is its main drawback. To overcome this drawback, the present paper proposes to use an amplified actuator in an ISM instead of a classical direct actuator. The impact of this choice is studied here, from speed and electrical current points of view.This study determined in an analytical way the influence of the actuator stroke on the step size of an ISM via an optimised control signal. The results are then confronted to a lumped model to identify potential limitations. Finally, a test bench is built using three different piezoelectric actuators to obtain experimental feedback about the benefits of actuator amplification in ISMs.     

Extended state observer-based time-optimal control for fast and precise point-to-point motions driven by a novel electromagnetic linear actuator

An extended state observer-based time-optimal control is proposed in this paper to achieve fast and precise point-to-point motions driven by a novel electromagnetic linear actuator. Working principle and characteristics of the actuator are analyzed. Total disturbance is estimated by an extended state observer, and the nonlinear system is compensated as a linear one. Time-optimal control is used to realize accurate point-to-point motions with minimal time. Comparative simulations and experimental results demonstrate the effectiveness of the proposed method, especially for non-repetitive point-to-point motions, and good positioning performance has been achieved in the presence of both model uncertainties and external disturbances.     

Electromagnetic Actuator Control: A Linear Parameter-Varying (LPV) Approach

This paper deals with system identification and control of a nonlinear electromagnetic actuator, which can be used in many practical applications: electromagnetic valve actuators of combustion engines, artificial heart actuators, magnetic levitation, electromagnetic brakes, etc. The considered practical control problem requires accurate control of the moving armature between two extreme positions. The main objective is to assure small contact velocity, which is known as "soft landing" of the moving armature, and, in this way, low-noise low-component-wear operation. First, due to open-loop instability, system-identification experiments are performed around different equilibrium positions under closed-loop control, and a linear parameter-varying (LPV) model and a bound of plant uncertainty are derived. Next, an LPV controller is designed in a robust control framework (robust gain-scheduled controller). Since the system evolves along quasi-equilibrium positions, quadratic and biquadratic analyses are performed using linear matrix inequalities. Finally, the experimental results show that the controller design problem can be handled successfully, considering an LPV approach. This paper reflects a pragmatic viewpoint: The control structure is simple and easy to implement, and offers good performance and robustness; therefore, it is suitable for industrial applications     

基于H like模型的压电陶瓷作动器内模控制

针对压电陶瓷作动器的率相关特性降低应用端控制精度的问题,该文研究了基于Hammerstein like模型的内模控制策略。其中非线性部分由最小二乘支持向量机模型表示,动态线性部分由自回归历遍模型表示。在此基础上构建了系统逆模型,设计了内模控制器以实现对压电陶瓷作动器的跟踪控制,最后通过实验平台进行了验证。实验结果表明,实时跟踪100 Hz内的期望信号相对误差均小于10%,证明了所设计内模控制方案的有效性。     

Design and experimental implementation of an electromagnetic engine valve drive

In conventional internal combustion engines, engine valve displacements are fixed relative to crankshaft position. If these valves were actuated as a variable function of crankshaft angle, significant improvements in fuel economy could be achieved. To this end, a new type of electromagnetic valve drive system (EMVD) for internal combustion engines was more recently proposed. This EMVD incorporates a disk cam with a very desirable nonlinear profile which that functions as a nonlinear mechanical transformer. Modeling and simulation results showed significant advantages of this EMVD over previously designed electromagnetic engine valve drives. In this articles, we describe an experimental implementation of the proposed EMVD, which was developed to confirm these benefits. The EMVD apparatus was designed, constructed, and integrated into a computer-controlled experimental test stand. The experimental results confirm the benefits of using a nonlinear mechanical transformer in a motordriven engine-valve spring system, as seen in the small average power consumption and low valve seating velocity. In addition, a valve transition time sufficient for 6000-rpm engine operation was achieved. The results also suggest ways to improve the EMVD apparatus in the future.     

用于微振动控制的超磁致伸缩驱动器的研究

文章介绍了允动器在振动主动控制系统中的作用，叙述了超磁致伸缩驱动器的设计计算过程和结构组成，给出了超磁致伸缩驱动器的位移输出特性曲线。     

Active vibration control over the flexible structure of a kitchen hood

This paper presents the full analysis and the complete development of a system for mechanical vibration reduction in a kitchen hood by using piezoelectric actuators. The control system is based on a feedback controller whose action depends on a single acceleration sensor collocated with the actuator. A model of the collocated actuator-sensor pair mounted on the hood and a model of the disturbance are provided. A Minimum Variance (MV) controller is able to provide the theoretically best performance in terms of noise reduction. A single-tones Minimum Variance controller (resonant controller) provides quasi-optimal performance while maintaining the stability of the system. Two different resonant control laws have been designed: the first one operates without the information of the hood motor velocity; the second one is a more sophisticated controller, which also exploits the velocity information. Both controllers are effective in reducing the mechanical vibration with performances that well approximate those achievable with an MV controller. Overall, through the motor velocity’s information, the best performances are guaranteed with an 85% vibration reduction. The resonant control system without the motor velocity information provides the best compromise in terms of performances (75% of reduction) and complexity of the implemented system. Tests held in an anechoic chamber have shown the vibration reduction’s influence upon the acoustic noise.     

Modeling, control and experimental validation of a novel actuator based on shape memory alloys

The paper presents the development of a mechanical actuator using a shape memory alloy with a cooling system based on the thermoelectric effect (Seebeck–Peltier effect). Such a method has the advantage of reduced weight and requires a simpler control strategy as compared to other forced cooling systems. A complete mathematical model of the actuator was derived, and an experimental prototype was implemented. Several experiments are used to validate the model and to identify all parameters. A robust and nonlinear controller, based on sliding-mode theory, was derived and implemented. Experiments were used to evaluate the actuator closed-loop performance, stability, and robustness properties. The results showed that the proposed cooling system and controller are able to improve the dynamic response of the actuator.     

压电陶瓷驱动器在机器人柔性臂应用中的研究

研究了片状压电陶瓷驱动器在柔性手臂中的应用,推导了基本压电陶瓷驱动器的柔性臂静力学方程,建立了描述驱动器迟滞特性的Ｐｒｅｉｓａｃｈ模型,提出了一种基于Ｐｒｅｉｓａｃｈ前钏环的ＰＩＤ掏方法对柔性夺动主动控制和轨迹控制俞中以有效地克服片状压电陶瓷驱动器的迟滞特性,消除柔性臂运动产生的振动,实现柔性臂的精度轨迹控制。