Dual-stage Actuator Research Articles

Cooling/heating dual-stage actuators decoupling structure design and energy management strategy for thermostatic airflow control

The temperature control system is required to have both cooling and heating actuators to achieve a high-precision thermostatic indoor air environment of industrial buildings. The coupling of the two actuators and the generation of redundant energy consumption leave a sufficient gap to be optimized. Combining the Linear Quadratic Regulator (LQR) approach with the sensitivity decoupling structure, we construct a dual-stage PI controller for this type of dual-input single-output system. Meanwhile, a proposed energy management technique for lowering energy consumption can alter the controlled quantities adaptively and synergistically. Accordingly, the multi-objective teaching–learning-based optimization algorithm is implemented to determine the optimal parameters and establish a balance between temperature stability and energy consumption. Simulation and experimental platforms are built to verify the design effect. Compared with four typical single-stage PI controller tuning algorithms, the proposed method has better output temperature stability with an improvement of the index by at least 14%. And the results reveal that the control input is decreased by 45.6% when the energy management technique is implemented, while the stability index of the final output temperature is maintained at about the same level.

Frequency Response Data-based Resonant Filter Design considering Phase Stabilization and Stroke Limitation applied to Dual-Stage Actuator Hard Disk Drives

Disturbance rejection of a Hard Disk Drive (HDD) enables a large amount of data storage in a recent information society. The aim is to design a feedback controller which rejects disturbances at multiple frequencies in HDDs. The disturbance rejection is achieved using resonant filters which have a large peak at disturbance frequencies. The developed approach enables the convex optimization of resonant filters with phase stabilization and stroke limitation using frequency response data of a controlled system. The disturbance rejection performance of the optimized resonant filters is validated in a dual-stage actuator HDD benchmark problem.

Dual-stage fast tool servo cascading a primary normal-stressed electromagnetic stage with a secondary piezo-actuated stage

The dual-stage actuation effectively extends the dynamic response and tracking accuracy of conventional fast tool servos (FTS). In this study, a normal-stressed electromagnetic stage is deliberately designed as the primary stage to cascade with a secondary piezo-actuated stage, constructing a new medium-range dual-stage FTS. Analytical models for both the normal-stressed actuator and the flexure mechanisms are established. The mechanical and electromagnetic parameters are selected and verified by finite element simulation, targeting the desired motion stroke and the maximized natural frequency. The prototype using the designed parameters is tested to have an actual stroke of 80μm and a first resonant frequency around 814 Hz. The dual-stage FTS employs a decoupled control strategy to track the desired trajectory precisely. As for the main controller, an additional disturbance observer is designed to work with the typical PID controller to compensate for both the internal nonlinear dynamics and external disturbances for each stage. The practical result demonstrates that the closed-loop bandwidth can be improved from 220 Hz to 500 Hz by cascading the secondary stage. As for the tracking of a complex trajectory with multiple frequencies, a motion error of around ±0.8μm was achieved, which is less than 30% of that obtained by the primary stage alone.

A novel dual-stage shape memory alloy actuated gripper

PurposeThe paper aims to propose a novel dual-stage shape memory alloy (SMA) actuated gripper (DAG), of which the grasp performance is improved through primary and secondary actuation.Design/methodology/approachThis paper presents a method of integrating the design of dual-stage actuation modules based on the SMA bias actuation principle to enhance the grasping shape adaptability and force modulation of a DAG. The actuation angle range and grasping performance of the DAG are investigated by thermomechanical analysis and the finite element method based numerical simulation.FindingsThe results of present experiments and simulations indicate that the actuation angle scope of the DAG is about 20° under no load, which enables the grasping space occupied by an object in the DAG from 60 mm to 120 mm. The grasping force adjusted by changing the input power of the primary main actuation module and secondary fine-tuning actuation module can reach a maximum of 2 N, which is capable of grasping objects of various sizes, weights, shapes, etc.Originality/valueThe contribution of this paper is to design a DAG based on SMA, and establish the solution methods for the primary main actuation module and secondary fine-tuning actuation module, respectively. It lays a foundation for the research of lightweight and intelligent robotic grippers.

Precision tracking control of a dual-stage measuring machine

Abstract Modern production requires shorter measuring cycles of measuring machines, which can be achieved with highly dynamic references causing dynamic deviations of the actual tool-center-point (TCP) position. To minimize the TCP tracking error, the considered measuring machine is extended with a redundant axis and a modular control concept is proposed. For this dual-stage actuation setting, a higher-level reference allocation module exploits the resulting redundancy and yields suitable position references for the lower-level controlled subsystems. On the higher-level, two dual-stage control concepts are presented, yielding both significantly reduced tracking errors in experiments compared to using only the main axis. Furthermore, to deal with strongly spatially varying friction of the main axis of the considered measuring machine, its lower-level control system is improved.

High-bandwidth controller design for dual-stage actuator system in hard disk drives

Large-capacity hard disk drives are important for the development of an information society. The capacities of hard disk drives depend on the positioning accuracy of magnetic heads, which read and write digital data, in disk-positioning control systems. Therefore, it is necessary to improve positioning accuracy to develop hard disk drives with large capacities. Hard disk drives employ dual-stage actuator systems to accurately control the magnetic heads. A dual-stage actuator system consists of a voice coil motor and micro-actuator. In micro-actuators, there is a trade-off between head-positioning accuracy and stroke limitation. In particular, in a conventional controller design, the micro-actuator is required to actuate such that it compensates for low-frequency vibration. To overcome this trade-off, this study proposes a high-bandwidth controller design for the micro-actuator in a dual-stage actuator system. The proposed method can reduce the required stroke of the micro-actuator by increasing the gain of the feedback controller of the voice coil motor at low frequencies. Although the voice coil motor control loop becomes unstable, the micro-actuator stabilizes the entire feedback loop at high frequencies. As a result, the control system improves the positioning accuracy compared to that achieved by conventional control methods, and the required micro-actuator stroke is reduced.

A Series-Hierarchical Iterative Learning Controller for Multi-Stage Systems

Multi-stage actuators are becoming more common in practice as the desire for larger work areas is combined with demands for higher precision. Systems such as these exist throughout the manufacturing and digital process environments which perform repetitive tasks. Iterative learning control (ILC) is a control strategy suited for such repetitive tasks. However, complex systems like these often exhibit coupling between individual stages. This letter presents a series-hierarchical ILC strategy (SH-ILC) that employs similar coupling between unique ILC algorithms to improve tracking performance in each stage of actuation. A numerical example of a dual-stage actuator (DSA) is provided, and simulation results demonstrate that the proposed SH-ILC achieves improved reference tracking performance over a comparable multivariable ILC approach.

Cooling/Heating Dual-Stage Actuators Decoupling Structure Design and Energy Management Strategy for Thermostatic Airflow Control

Cooling/Heating Dual-Stage Actuators Decoupling Structure Design and Energy Management Strategy for Thermostatic Airflow Control

Speed- and Range-Based Filter Design for Dual-Stage Actuator Control

Abstract Dual-stage actuators, which combine two actuators with different characteristics, have gained interest due to their large-range, high-resolution positioning capabilities. Control of such systems is challenging because it requires balancing the relative contributions of the individual actuators in terms of speed, range, and precision. The most common approach is to allocate effort to the actuators based on frequency but this can lead to misallocation in the case of low-frequency short-range trajectories. In this paper, the problem of trajectory allocation in dual-stage actuator systems is addressed using a recently developed range-based filter. The theoretical basis of the range-based filter is rigorously derived for the first time and insights regarding its use, specifically its reinterpretation as a speed-based filter, and its range-frequency response characteristics are presented. The new analysis not only explains the behavior of the filter clearly, but it provides a more robust strategy for incorporating range constraints in filter design for different desired trajectories.

An adjustable anti-resonance frequency controller for a dual-stage actuation semi-active vibration isolation system

An adjustable anti-resonance frequency controller for a dual-stage actuation semi-active vibration isolation system

Head-Positioning Control in Triple-Stage-Actuator Enterprise Hard Disk Drives Using Mixed H2/H∞ Synthesis Methodologies

Abstract The recent rapid growth in the cloud storage industry has strongly increased the demand for high-capacity enterprise hard disk drives (HDDs). Increasing the areal density brings new challenges to the high-accuracy head-positioning control in the next generation HDD development. Triple-stage-actuator (TSA) system is one of the emerging technologies (Atsumi, 2016, “Emerging Technology for Head-Positioning System in HDDS,” IEEJ J. Ind. Appl. 5(2), pp. 117–122.) that can achieve higher bandwidth than that of a dual-stage-actuator (DSA) system and improve the track-following performance. In this paper, we focus on the TSA system with one voice coil motor (VCM) and two piezoelectric (PZT) actuators. Two types of mixed H2/H∞ synthesis methodologies based on model-based optimization and data-driven optimization are proposed to design the track-following controller for the TSA system. The simulation results show the feasibility and effectiveness of the TSA systems with a tertiary PZT actuator. We also analyze the effects of stroke limitations and resonance frequencies of the second-/third-stage PZT actuators on the head-positioning accuracy. The results might provide a guideline for the TSA mechanical design.

Closed-Loop Range-Based Control of Dual-Stage Nanopositioning Systems

In this article, a closed-loop control framework for dual-stage nanopositioning systems is presented that allows the user to allocate control efforts to the individual actuators based on their range capabilities. Recent work by the authors has focused on range-based control of dual-stage actuators implemented as a prefilter, which assumes that each individual actuator has sensor feedback enabling them to be controlled separately. This article seeks to address the problem of range-based control of dual-stage systems when sensor measurements are only available from the total output of the system, a commonly encountered design. This is a significant departure from previous work since the range-based filter is included in the dual-stage system feedback loop and stability becomes a concern. In this article, the controller is presented, stability conditions are determined, and imaging experiments are performed on an atomic force microscope. Tracking results show that the root-mean-square tracking error for various triangular reference trajectories is improved with the presented range-based control structure by up to 50% compared to frequency-based methods.

Coupling Controller Design for MISO System of Head Positioning Control Systems in HDDs

Head positioning control systems are required to improve the positioning accuracy and thus increase the recording capacity of hard disk drives (HDDs). Existing head positioning control systems employ a dual-stage actuator system comprising a voice coil motor (VCM) and a piezoactuator. The control system is a multi-input single-output system, and positioning controllers must be designed for both actuators. In this article, we propose a coupling controller design method for head positioning control systems of HDDs. The proposed method designs the controllers by considering the interaction between the VCM and the piezoactuator. It is more complex than the decoupling controller design method, which is widely used to design the controllers for the dual-stage actuator system. Nevertheless, it provides greater freedom in the controller design. The main advantage is, when the entire feedback loop is stabilized, the feedback loop for each actuator does not need to be stabilized. The design results show that the proposed design method can improve the positioning accuracy with comparison to the decoupling controller design. Moreover, the amount of the required stroke of the piezoactuator is decreased by using the coupling controller design.

Experimental Study for μ-class Control of Relative Position and Attitude for Synthetic Aperture Telescope Using Formation Flying Micro-satellites

Earth remote sensing from geostationary orbit (GEO) realizes high time resolution that is essential for disaster monitoring; however, the spatial resolution is commonly worse than observation from low Earth orbit (LEO). In order to achieve high-resolution and high-frequency GEO remote sensing, we have proposed a “Formation Flying Synthetic Aperture Telescope (FFSAT)” with multiple micro-satellites. The FFSAT can improve the spatial resolution by using the technique of a synthetic aperture, and therefore the relative positions and attitudes between the optical units of each satellite must be controlled with an accuracy better than 1/10 of the observation wavelength. In order to verify feasibility of such highly accurate control, μ-class control experiments were conducted by using COTS components, and numerical models of the components were constructed. Results of the experiments were integrated into a software simulator, and the μ-class formation flying control of the entire FFSAT system was numerically evaluated. In this simulation, highly accurate control was achieved with dual-stage actuators, which consist of piezo actuators and thrusters. The simulation results show that the formation can be controlled in μ-class accuracy under some assumptions.

Controller Design Method for Stroke Reduction of Micro-actuator in HDD

For realizing high information society, recording capacity of the hard disk drives (HDDs) is required to increase. The capacity of the HDDs depends on positioning accuracy of magnetic head which read/write the digital data on disks. To improve the positioning accuracy, the head positioning control system employs a dual-stage actuator system. The dual-stage actuator system is consisting of the voice coil motor (VCM) and the micro-actuator. The micro-actuator has possibility to move accurately the magnetic head in higher frequency. On the other hand, the stroke limitation can be problem for increasing the control bandwidth: improvement of the positioning accuracy. especially, the stroke limitation is a major constraint to compensate for low frequency vibration. There is the tradeoff between the stroke limitation and the positioning accuracy. To overcome the problem, this study proposes the controller design method for stroke reduction of the micro-actuator. The proposed design method can adjust the main working frequency for each actuator. In this system, the VCM can mainly compensate for the low frequency vibration. The micro-actuator mainly focuses on stabilization of the control system in higher frequency, the working doesn’t require the large stroke. The effectiveness is verified in the compensation of the representative internal and external vibration. The proposed method can reduce the stroke of the micro-actuator by about 60% with comparison to the conventional design method with keeping the positioning accuracy.

Quadruple-Stage Actuator System for Magnetic-Head Positioning System in Hard Disk Drives

In this article, we present a magnetic-head positioning system in hard disk drives (HDDs) with a quadruple-stage actuator system. The quadruple-stage actuator system consists of a voice coil motor, a milliactuator with two piezoelectric (PZT) elements, a microactuator with two PZT elements, and a thermal actuator. The milliactuator is the first generation of a secondary actuator for a dual-stage actuator in the HDDs and moves a sway mode of a suspension in a head-stack assembly. The microactuator is the second generation of the secondary actuator for the dual-stage actuator in the HDDs and moves a yaw mode of the suspension. The thermal actuator is an actuator in a development phase for future HDDs. It consists of heaters embedded in the magnetic head and moves read/write elements a few nanometers in a horizontal direction with thermal expansion. The achievable disturbance-rejection performance of the proposed quadruple-stage-actuator system is higher than that of the conventional triple-stage actuator system because the proposed system can decrease a negative impact caused by the stroke limitation of the thermal actuator. As a result, the magnetic-head positioning system with the quadruple-stage-actuator system enables us to improve the positioning accuracy under the external vibrations by about 48 ${\%}$ from that with the triple-stage-actuator system.

Comparative Analysis among Single-Stage, Dual-Stage, and Triple-Stage Actuator Systems Applied to a Hard Disk Drive Servo System

In modern times, the design and optimization of different actuator systems for controlling a high-precision position control system represent a popular interdisciplinary research area. Initially, only single-stage actuator systems were used to control most of the motion control applications. Currently, dual-stage actuation systems are widely applied to high-precision position control systems such as hard disk drive (HDD) servo systems. In the dual-stage system, a voice coil motor (VCM) actuator is used as the primary stage and a piezoelectric micro-actuator is applied as the secondary stage. However, a dual-stage control architecture does not show significant performance improvements to achieve the next-generation high-capacity HDD servo system. Research continues on how to fabricate a tertiary actuator for a triple-stage HDD servo system. A thermal positioning controller (TPC) actuator is considered promising as the tertiary stage. The triple-stage system aims to achieve greater bandwidth, track density, and disk speed, with minimum sensitivity and greater error minimization. In this work, these three actuation systems with different combinations of proportional plus integral (PI), proportional plus derivative (PD), and proportional plus integral plus derivative (PID) controller, lag-lead controller, lag filter, and inverse lead plus a PI controller were designed and analyzed through simulation to achieve high-precision positioning. The comparative analyses were done on the MATLAB/Simulink simulation platform.

Identification and Compensation of Dynamic Interaction in a Non-Contact Dual-Stage Actuator System.

Dynamic interaction seriously limits the overall performance of a Dual-Stage Actuator (DSA) system. This paper aims to identify and compensate for the dynamic interaction in a non-contact DSA system. The effects of the interaction in the non-contact DSA system are initially classified as non-contact position-dependent disturbance forces (PDDFs) and velocity-dependent disturbance forces (VDDFs). The PDDFs in the three degrees of freedom (DoFs) motion space between the two stages of the DSA system are directly identified in the time domain, and VDDFs are indirectly identified in the form of damping values in frequency domains. The feedforward networks of the force are subsequently applied to compensate the PDDFs and VDDFs, which are indexed with relative displacement and velocity, respectively. Experiments are finally conducted to investigate the effectiveness of compensation, which infers that the final positioning error in the time domain can be reduced from 260 nm to 130 nm with PDDFs and VDDFs compensation. The gain of the interaction transfer is decreased in the frequency range of up to 45 Hz with PDDFs and VDDFs compensation. With this method, some weak dynamic interaction can be completely compensated for by the force feedforward compensation, and the positioning accuracy of non-contact DSA systems can be greatly improved.

Design and Control of a Dual-Stage Actuation Active Vibration Isolation System

Active vibration isolation system is used in various fields to reduce the vibrations transmitted. In this paper, a novel dual-stage actuator is proposed, which combines a voice coil motor and a piezoelectric actuator. The proposed dual-stage actuator maintains the advantages, in terms of the long stroke, the high precision, and the wide band. The dual-stage actuation active vibration isolation system (DSA-AVIS) with the proposed dual-stage actuator is initially modeled. The characteristic of the DSA-AVIS is subsequently analyzed. H ∞ controller is finally designed to consider the vibration isolation performance and the output range of the actuators. The experimental results indicate that the closed-loop transmissibility of the DSA-AVIS is less than -18 dB from 0 to 100 Hertz.

Stroke Oriented Controller Design for Dual-stage Actuator of Head Positioning Control System in Hard Disk Drives

In this research, we have proposed a stroke-oriented controller design for head positioning control system of hard disk drives (HDDs). A dual-stage actuator composed of a voice coil motor and a piezo actuator is widely used in the head positioning system. The decoupling filter design which decouples the interaction of each the actuator is a representative controller design for the dual-stage actuator. However, it is necessary for the feedback loop related to the piezo actuator to increase the gain in the low frequency range due to design constraints. It can lead to increase a required stroke of the piezo actuator. The proposed controller design can decrease the required stroke of the piezo actuator by utilizing the interaction of each the actuator. To confirm the effectiveness the proposed controller design method, a simulation was performed to compensate for external vibrations. As the results, it was confirmed that the required stroke of the piezo actuator can be reduced by about 65%, while the stability and positioning accuracy of the head positioning control system is almost same as the that of decoupling filter design.