RCBode plot-based controller design for dual-stage actuators in HDDs

Combined H∞/H2 controller design and optimal selection of sensors and actuators

Dynamics and control of aggregate thin film surface morphology for improved light trapping: Implementation on a large-lattice kinetic Monte Carlo model

As the technology advance of UAV (Unmanned Aerial Vehicle), the large UAV is a prevalent trend, which is widely used for scout and strike in modern military battlefield. The flight safety is rather important because of the cost increase of UAV with various airborne devices equipped. EMA (Electromechanical Actuator) is one of the key components in UAV system. Whether its performance is reliable or not determines the flight safety. In this paper, in order to design high-power EMA for scout and strike UAV with fast response and high stability to ensure UAV safety, dual-redundancy technology is adopted. There are two communication interfaces between the actuator and the flight mission computer. The control circuit and the drive circuit are in the form of dual redundancy, while there are two sets of windings in the motor. The controller and actuator design are introduced in details one by one. Also, the paper presents the dual-redundancy design scheme. Several ground tests simulating the real flight conditions are conducted, proving that the EMA design is feasible and its performance is satisfactory. The UAV flight tests are needed later in the future to verify EMA performance in practice.

A recently developed large-span track-seeking and track-following method for dual-stage actuator systems is improved in terms of settling duration, recovery from saturation in the secondary actuator loop and design flexibility by incorporating an anti-windup (AW)-compensation scheme. The developed large-span track-seeking and track-following controller is based on a well-known method which allows the decoupling of the secondary micro-actuator loop from the primary VCM-loop in terms of stability and design. For the originally suggested method, micro-actuator saturation was addressed using the circle criterion to guide the controller design for this loop. However such an approach does not allow the fine-tuning of seeking and settling speeds and also limits the class of linear controllers for the secondary loop. This paper suggests the use of an anti-windup compensator, based on an /spl Lscr//sub 2/-optimization approach and computed using linear matrix inequalities (LMI's), to cope with the saturation issues in the secondary loop, allowing full freedom in the initial linear controller design. The suggested approach is demonstrated using a PZT-actuated suspension and a commercial VCM-actuator.

Motivation: The LQR and LQG techniques are widely used for designing disturbance rejection controllers for linear systems. In this chapter, quasilinear versions of these techniques are developed and extended to simultaneous design of controllers and instrumentation, that is, actuators and sensors. Overview: We begin with developing the SLQR/SLQG technique, where the “S” stands for “saturated” (Section 6.1). Then, we extend LQR/LQG to the so-called ILQR/ILQG (where the “I” stands for “instrumented”), which is intended for simultaneous design of controllers, sensors, and actuators (Section 6.2). For each of these methods, we show that the solution is given by the usual Lyapunov and Ricatti equations coupled with additional trancendental equations, which account for the Lagrange multipliers of the associated optimization problems and the quasilinear gains. Bisection algorithms for solving these coupled equations are provided. Saturated LQR/LQG Scenario The LQR/LQG design methodology is one of the main state space techniques for designing linear controllers for linear plants, assuming that the actuators and sensors are also linear. Clearly, this methodology is not applicable to nonlinear systems. Is an extension to LPNI systems possible? A positive answer to this question is provided in this section for systems with saturating actuators. The resulting technique is referred to as SLQR/SLQG, where the “S” stands for “saturated.” Extensions to other nonlinearities and to nonlinearities in actuators and sensors simultaneously are also possible using the approach presented here.

Adjustable compliance or variable stiffness actuators comprise an additional element to elastically decouple the actuator from the load and are increasingly applied to human-centered robotic systems. The advantages of such actuators are of paramount importance in rehabilitation robotics, where requirements demand safe interaction between the therapy system and the patient. Compliant actuator systems enable the minimization of large contact forces arising, for example, from muscular spasticity and have the ability to periodically store and release energy in cyclic movements. In order to overcome the loss of bandwidth introduced by the elastic element and to guarantee a higher range in force/torque generation, new actuator designs consider variable or nonlinear stiffness elements, respectively. These components cannot only be adapted to the walking speed or the patient condition, but also entail additional challenges for feedback control. This paper introduces a novel design method for an impedance-based controller that fulfills the control objectives and compares the performance and robustness to a classical cascaded control approach. The new procedure is developed using a non-standard positive-real Η2 controller design and is applied to a loop-shaping approach. Robust norm optimal controllers are designed with regard to the passivity of the actuator load-impedance transfer function and the servo control problem. Classical cascaded and positive-real Η2 controller designs are validated and compared in simulations and in a test bench using a passive elastic element of varying stiffness.

<div class="htmlview paragraph">Recent interest in applications of adaptive engine mounts to improve ride quality and passenger comfort has introduced new research areas in the field of vehicle dynamics and control. Introduction of vehicles with smaller engines and lighter and more flexible frames, for the purpose of improving fuel economy, has led to increased frame vibration levels. Frame vibration at engine idle speeds is caused by engine firing and imbalance forces which are transmitted primarily through the engine mounts. Consequently, effort has been focused on improving engine mount technology to achieve better vibration isolation.</div> <div class="htmlview paragraph">Introduction of adaptive engine mounts into the dynamics of a flexible engine-frame system requires an integrated study from both vibration and control points of view. This paper presents the results of an on-going research on applications of adaptive hydraulic mounts, manufactured by Cooper Industrial Products, on a Ford Ranger Light Truck. Several issues have been studied which form the fundamentals for optimal implementation of adaptive engine mounts. These include: system modeling, controller design, required sensors, and design of new actuators. The focus of this paper is on the controller design for hydraulic engine mounts. In particular, the issue of open-loop control versus closed-loop control will be discussed and performance of these control schemes once implemented on the actual vehicle will be compared.</div>

<p>A pneumatic actuator is a device that converts compressed air into mechanical energy to perform varieties of work. It exhibits high nonlinearities due to high friction forces, compressibility of air and dead band of the spool movement which is difficult to manage and requires an appropriate controller for better performance. The purpose of this study is to review the controller design of pneumatic actuator recommended by previous researchers from the past years. Initially, the basic views of the pneumatic will be presented in terms of introduction to the pneumatic actuator and its applications in industries. At the end of this review, discussions on the design of the controllers will be concluded and further research will be proposed along with the improvement of control strategies in the pneumatic actuator systems</p>

Haptic devices need to render accurate force to a human operator in order to create a virtual environment from a remote real environment. Existing end-effector type haptic devices employ parallel mechanisms to achieve force interaction in multiple degrees-of-freedom (DoF). Those parallel mechanisms have non-constant Jacobian matrices that create difficulties in the actuator and controller design for accurate haptic force interaction. This paper presents a 3-DoF translational parallel manipulator (TPM) with a constant Jacobian matrix to facilitate the force and impedance controller design. Instead of using external force sensors, series elastic actuators (SEAs) are used for the proposed device to realize the force rendering. SEAs can render more accurate output force and stiffness while the inertia and friction problems of using a gearhead can be ignored. In this paper, the modeling, design, and control of the haptic device are established to show the merits of the proposed TPM. Initial force control experiments demonstrate the accuracy and speed of SEA-based force control. We expect that this novel haptic device can serve as an alternative for robotic teleoperations requiring accurate force sensing and control.

This paper presents a controller design approach to provide the precise force control considering compensation for interference and disturbance in load devices. In the control system, a pneumatic actuator and a voice coil motor are combined as a dual-stage actuator to expand the servo bandwidth of the load control. The interference between the actuators, however, deteriorates the servo performance, especially at around the cross-over frequency. In addition, the disturbance generated by an abrasive motor deteriorates the tracking performance for the target value. In this research, therefore, a PQ method is adopted to achieve the high precision load control by expanding the servo bandwidth. Here, the compensators are designed to compensate for the interference, while a resonant filter is designed to suppress the disturbance with the specific frequency, paying attention to a vector locus of the open-loop characteristic. The proposed approach has been verified by experiments using an actual load device.

This paper presents a new controller design method for dual-stage actuators. The controller consists of two stabilizing controllers for VCM and MEMS actuators and two main controllers (slave and master). The slave and master controllers are used to shape the sensitivity of the closed loop system at low and high frequency, respectively. With the proposed method satisfactory sensitivity and complementary sensitivity are achieved.

Crucial to the increase in aerial densities of future hard disk drives (HDD) is the increase of the number of tracks per inch. In order to achieve very high track densities new high bandwidth and very accurate servo systems will be necessary. One possible solution is the use of dual-stage actuators, in which a high bandwidth and a highly accurate micro-actuator (MA) is used in combination with a traditional voice coil motor (VCM). In this case the nature of the servo controller becomes multivariable since both the VCM and the MA have to be controlled simultaneously. The design of servo controllers for track following with dual-stage actuators has been an active area of research in the last few years. Modern control methods were specifically developed for multivariable systems and offer significant advantages over classical control methods. On the down side, they usually lead to controllers which are of order equal to or greater than the plant they were designed for. The aim of the paper is to present a systematic approach for the design of a fixed order servo controller and to illustrate this design on a piezoelectric MA designed by Hutchinson Technologies Inc. The complexity of the servo controller is limited to address costs and implementation issues in a commercial HDD. The systematic approach for such a low order servo controller design is developed in the paper by utilizing H/sub /spl infin//-optimization with a choice of specific closed loop weighting functions and additional constraints on the order of the controller.