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This paper presents a settling control of a dual-actuator system for hard disk drives. The dual-actuator system consists of a voice coil motor (VCM) as a first stage actuator and a push-pull-type piezo-electric transducer (PZT) as a second-stage actuator. The settling controller is designed in three steps. In the first step, the VCM controller is d...
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... DUAL-ACTUATOR SYSTEM OF HARD DISK DRIVES Fig. 1 shows a basic schematic diagram of a hard disk drive (HDD) with a dual-actuator system. Several disks are stacked on the spindle motor shaft, and each disk is accompanied by a pair of recording heads. Each head is attached to the tip of a sus- pension. The PZT actuator is placed between the suspension and the base plate [5]. The VCM ...
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Citations
... In light of the above facts, numerous scholars have already presented outstanding researches relating to coordinated control problem and obtained extensive and in-depth research results. Numasato et al. presented the strategy to retard the response of motor system, resulting in consistent response of the motor and hydraulic system, thereby decreasing the switching impacts [6]; yet the strategy suffers from limitations and prone to bring about the response hysteresis. To alleviate the problem, Ko et al. applied filtering algorithm to eliminate the difference in response between motor and hydraulic system [7], which is not applicable to some transient conditions; Todeschini et al. designed a dead time compensator to improve the response time of the hydraulic system [8], which is poor in eliminating the hysteresis of pressurization. ...
Due to the difference of time‐domain response between hydraulic braking and regenerative braking, as well as changes of equivalent parameters and operating parameters during braking mode switching, it is liable to cause torque fluctuation, which affects braking safety and vehicle ride comfort. First, the uncertainties of vehicle load and frictional coefficient model are investigated. Second, the hybrid system theory is applied to provide state transfer condition for mode switching strategy. Finally, the control strategy that utilizes regenerative braking torque to compensate for difference of the required braking torque is designed, and a new μ‐H ∞ control algorithm through D‐K iteration is presented to improve the robust performance. The proposed μ‐H ∞ control strategy is examined under various braking situations, and the results indicate that (1) the μ‐H ∞ controller have the advantage of robustness performance, the amplitude of regenerative braking is decreased by 6.14%, and the steady‐state error of hydraulic braking is decreased by 5.26% over the H ∞ , and (2) under the braking mode switching, the designed compensation control strategy has the performance of fast and accurate tracking of the desired torque, and the steady‐state error does not exceed 3.5%.
... According to the dynamic response difference between the friction brake and the hub motor, experts and scholars have done a significant amount of research work on the above-mentioned coordinated control problem, and obtained extensive and indepth research results. Numasato et al put forward a method to eliminate the difference in response time between the motor and hydraulic system to make the response time tends to be consistent by correcting the response speed, thus reducing the switching impact [5]. However, the method has its limitations, which is prone to cause the response hysteresis of system. ...
In the process of braking mode switching of electro-hydraulic brake (EHB) system, there exist time delay and time-varying model parameters in the actual control process, result in the delay of state transfer and controller effectiveness degradation. In response to the above concerns, a torque coordinated control strategy is provided. Firstly, the motor compensation control algorithm is provided to reduce the fluctuation of the actual braking torque as well as considering the braking feeling and energy recover. On top of which, an optimization model incorporating braking feeling and braking energy recover is developed; Secondly, the improved non-dominated sorting genetic algorithm (NSGA-II) is applied to optimize the distribution coefficient to achieve the higher recover energy and stable braking feeling; Furthermore, given the communication delay exists in the compensation control process, which is liable to cause decreasing the quality of braking mode switching, a coordinated delay compensation control strategy consisting of improved compensation module of RBF-Smith, braking mode coefficient solver module, braking force distribution module, and motor compensation control module is introduced. The proposed control algorithm is examined under various time delays and the results indicate that the algorithm effectively tackles communication delay and time-varying model parameters in mode switching stabilization.
... In these, miniature linear actuators play an important role in controlling optical systems, such as zoom and autofocus features, to allow camera modules to obtain clearer images. The most commonly used linear actuators are voice coil motors, which are electromagnetic linear motors that are also used for hard disk drives [1]. These are designed to surround a lens with coils and are placed in front of an image sensor. ...
We present a miniature linear piezoelectric ultrasonic motor with a thin and hollow design, which can serve as an essential component of autofocusing features in next-generation camera modules. It consists of a thin square stator with a hole and an elastic cylindrical slider with a slit. The motor design, in which the slider inserted into the stator hole expands outward, enables a hollow structure for centering a lens and an optimal preload for enhancing the motor thrust force. In this study, we model the relationship between the dimensions and the preload statically to quantify the preload value and clarify the design methodology of the motor. After optimizing the preload empirically, we evaluate the fundamental characteristics experimentally. The stator with a side length of 4.5 mm and a thickness of less than 1 mm provides a thrust force of 12.9 mN that leads to a quick response, which is a requirement of autofocusing. Finally, the motor drive system with visual feedback control is used to demonstrate the positioning of an actual lens group in front of an image sensor to obtain clearer images.
... One of the most well-used linear electromagnetic motors is the voice coil motor (VCM). A well-known application of VCMs is hard disk drives [72], [73]. In relation to the positioning control of VCMs, their fundamental characteristics in terms of design, modeling, and actuation have been summarized in an earlier review article [74]. ...
Micromotors are of great interest not only for the miniaturization of current products but also for the realization of future micromachines that can explore challenging environments. The speed of downsizing actuators is slower than that of semiconductor components, but developments over the last two decades have overcome several difficulties and enabled engineers to start designing applications. In this article, we review the existing micromotors ranging from famous articles to state-of-the-art, in particular recent developments and their applications. We deal with three representative principles for rotary and linear micromotors: electromagnetics, electrostatics, and piezoelectricity. Another purpose of this article is to suggest design criteria and physical limitations on these principles for engineers who design millimeter-scale automation devices. Incorporating micromotors can permit space saving and improve design flexibility in application designs, such as smartphones and medical devices.
... To control a servomechanism in dual-stage HDDs, various methods have already been designed and optimized and are described in the existing literature [7][8][9][10][11]. The decoupled master-slave architecture is explained in [12][13][14][15], the parallel structure is presented in [16][17][18], and the PQ method is described in [19]. ...
... To control a servomechanism in dual-stage HDDs, various methods have already been designed and optimized and are described in the existing literature [7][8][9][10][11]. The decoupled master-slave architecture is explained in [12][13][14][15], the parallel structure is presented in [16][17][18], and the PQ method is described in [19]. In a triple-stage system, the R/W head is controlled by three stages with the help of three actuators installed in different positions of the suspension-a VCM actuator used as the primary stage, a PZT micro-actuator used as the secondary stage, and a thermal positioning controller (TPC) actuator used as the tertiary stage [20][21][22][23][24][25][26]. ...
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.
... Consequently, the two main challenges in designing a controller for the stage are: 1) to track input signals with frequencies larger than the most dominant resonant frequency of the stage; and 2) to reduce the resonance peak magnitude, i.e., to increase the damping so as to minimize the effects of exogenous disturbances on the stage. Many active damping controllers have been reported in the literature for a range of applications including nanopositioning stages [19], [20], disk drives [21], [22] and high-speed atomic force microscopy [23] among others. Some of the active damping control techniques such as positive position feedback, positive velocity and position feedback, linear quadratic Gaussian, and linear quadratic regulator (LQR) are computationally complex and difficult to implement while others such as integral force feedback (IFF) and integral resonant control (IRC) are much easier to design and implement. ...
The precise, high-speed control of nanopositioning stages is critical for many microscale additive manufacturing systems, such as microscale selective laser sintering (μ-SLS), where high throughput is needed. In μ-SLS, the positioning stage requires achieving 10 Hz steps with sub-100 nm accuracy and a travel range of 50 mm. The open loop resolution and settling time of the flexure stage presented in the study are found to be 63 nm and 1.27s respectively. This settling time is too large for its application in high throughput μ-SLS. To improve the tracking performance of the stage for fast varying signals upto 10 Hz and achieve better resolution, this paper presents the design of a finite horizon linear quadratic regulator controller for the XY stage. Owing to the good damping properties of the controller, the resolution is improved to 8 nm and input signals with 10 Hz frequency are effectively tracked. With the addition of a resonant shifting control, the tracking bandwidth is improved to 23 Hz. The paper presents a unique combination of low cost, large travel, sub 10 nm resolution and high bandwidth XY positioning system, which is not to be found in either off-the-shelf nanopositioning stages or in research labs.
... Consequently, the two main challenges in designing a controller for the stage are: 1) to track steps at speeds faster than the most dominant resonant frequency of the stage and 2) to reduce the resonance peak magnitude, i.e., to increase the damping so as to minimize the effects of exogenous disturbances on the stage. Many active damping controllers have been reported in literature for a range of applications including nanopositioning stages [19], [20], disk drives [21], [22] and high-speed AFM [23] among others. Some of the active damping control techniques such as Positive Position Feedback (PPF), Positive Velocity and Position Feedback (PVPF), Linear Quadratic Gaussian (LQG), Linear Quadratic Regulator (LQR) are computationally complex and difficult to implement while others such as Integral Force Feedback (IFF) and Integral Resonant Control (IRC) are much easier to design and implement. ...
The precise, high-speed control of nanopositioning stages is critical for many microscale additive manufacturing systems, such as microscale selective laser sintering (μ-SLS), where high throughput is needed. In μ-SLS, the positioning stage requires achieving 10 Hz steps with sub-100 nm accuracy and has a stroke of 50 mm. The open loop resolution and settling time of the flexure stage presented in the study are found to be 63 nm and 1.27s respectively. This settling time is too large for its application in high throughput μ-SLS. To improve the tracking performance of the stage for fast varying signals upto 10 Hz and achieve better resolution, this paper presents the design of a finite horizon linear quadratic regulator controller for the XY stage. Owing to the good damping properties of the controller, the resolution is improved to 8 nm and signals with 10 Hz frequency are effectively tracked. With addition of a resonant shifting control, the tracking bandwidth is improved to 23 Hz. The paper presents a unique combination of low cost, large travel, sub 10 nm resolution and high bandwidth XY positioning system, which is not to be found in either off-the-shelf nanopositioning stages or in research labs.
... Such a dual-stage configuration simultaneously delivers long-range, precise, and rapid motion, which would have been challenging to achieve with a single actuator. Figure 1.1 (c) illustrates a voice coil actuator connected in series with a piezo actuator for controlling the motion of the read/write head in hard disk drives [9,[28][29][30]. The increased motion range and precision enabled by this dual-stage configuration enables faster read/write speeds (higher throughput) and higher data density (capacity). ...
... 1: (a) The Use of Redundant Effectors to Compensate for a Failed Effector in an Airbus Plane[7], (b) Over-Actuation in the Vehicles using In-Wheel Motors and Steer-by-Wire System to Replace Conventional Powertrain and Steering[8], and (c) Over-Actuated Dual-Stage in Hard Disk Drive[9] ...
Over-actuated (or input-redundant) systems are characterized by the use of more actuators than the degrees of freedom to be controlled. They are widely used in modern mechanical systems to satisfy various control requirements, such as precision, motion range, fault tolerance, and energy efficiency. This thesis is particularly motivated by an over-actuated hybrid feed drive (HFD) which combines two complementary actuators with the aim to reduce energy consumption without sacrificing positioning accuracy in precision manufacturing. This work addresses the control challenges in achieving energy optimality without sacrificing control performance in so-called weakly input-redundant systems, which characterize the HFD and most other over-actuated systems used in practice. Using calculus of variations, an optimal control ratio/subspace is derived to specify the optimal relationship among the redundant actuators irrespective of external disturbances, leading to a new technique termed optimal control subspace-based (OCS) control allocation. It is shown that the optimal control ratio/subspace is non-causal; accordingly, a causal approximation is proposed and employed in energy-efficient structured controller design for the HFD. Moreover, the concept of control proxy is proposed as an accurate causal measurement of the deviation from the optimal control ratio/subspace. The proxy enables control allocation for weakly redundant systems to be converted into regulation problems, which can be tackled using standard controller design methodologies. Compared to an existing allocation technique, proxy-based control allocation is shown to dynamically allocate control efforts optimally without sacrificing control performance. The relationship between the proposed OCS control allocation and the traditional linear quadratic control approach is discussed for weakly input redundant systems. The two approaches are shown to be equivalent given perfect knowledge of disturbances; however, the OCS control allocation approach is shown to be more desirable for practical applications like the HFD, where disturbances are typically unknown. The OCS control allocation approach is validated in simulations and machining experiments on the HFD; significant reductions in control energy without sacrificing positioning accuracy are achieved.
... In this type of actuation, a VCM is used to realize high-speed large-stroke macromotion, and a PZT is used to achieve high-precision micromotion for high-speed ultraprecision positioning. Combining of the characteristics of VCM and PZT [9]- [13] in macro-micro composite actuation can help solve the contradiction problem of high-speed, large-stroke motion with high positioning accuracy. ...
A macro-micro composite precision positioning stage is mainly used in microelectronics manufacturing to achieve high-velocity and high-precision positioning. The residual vibration caused by high-speed macromotion will prolong the settling time and influence the working efficiency. This paper proposes a rapid dynamic positioning (RDP) method to quickly reduce the settling time of a macro-micro positioning stage by employing a designed spring-piezoelectric microstage. The main points of the RDP method are that it can start up the microstage at appropriate moment with proper extension to work against the macromotion vibration. Once the stage vibration amplitude is reduced to the piezoelectric element stroke limit, the micromotion is actuated to approach its final position. In this study, the start-up conditions and extension amount of the piezoelectric element were determined for implementing the RDP method. The feasibility of the method was clarified through theoretical analysis, including dynamic modeling, natural frequency analysis, and a vibration reduction and error compensation analysis. The experimental work was carried out, and the results validated the effectiveness of the RDP method in settling time reduction at different movements. With the assistance of the RDP method, the macro-micro high-speed, large-stroke stage can achieve an effective settling time reduction without sacrificing its accuracy.
... For feedback controller, a proportional and integral (PID) controller is used as it is simply designed and has good robustness. What's more, to damp resonant behavior, a notch filter is designed [10,11]. For feedforward controller, feedforward sequence is designed. ...
