Research On Dual Stage Actuated HDD Head Positioning System Based On Integral Resonance Control Technique

In this information era,hard disk drives(HDDs)have been an essential storage device in people's daily life for long time.At the same time,they are promoting the development of modern science and technology rapidly.However,with the rapid growth of electronic data,larger disk surface densities are indispensable.But because of the low bandwidth and low positioning precision of the single-stage actuated(SSA)HDD,the storage capacity of the disk is hard to increase,thus limiting the increase in disk density.On the other hand,to improve the positioning accuracy and disk density,dual-stage actuated(DSA)HDD head positioning technology has been proposed.Ultra-high areal density also makes the requirements of the transient performance very harsh.Therefore,a well-designed servo control system and excellent controller to improve the head positioning accuracy and transient performance of the head positioning system is particularly important.For SSA HDDs,only the voice coil motor(VCM)is used as an actuator for head positioning.However,the inherent mechanical resonance of the VCM hinders the increase of the servo bandwidth,thus limiting the improvement of the disk density.In order to break this limitation,DSA HDD head positioning system came into being.In this structure,the primary coarse actuator VCM for facilitating large motion is regulated in low frequency region,and the secondary micro-actuator(MA)for high-precision positioning is regulated in high frequency region,while suppressing high-frequency vibration.For a DSA HDD servo control system,a large servo bandwidth is desirable to attain ultra-high accuracy in read/write head positioning,but the resonant modes hamper the achievement of such an essential high bandwidth.Aiming at the problem,we propose in this paper a novel control scheme to achieve a transient performance enhancement for DSA HDD servo system.The control scheme is designed based on a feedback control method called integral resonant control(IRC),which is suitable for damping highly resonant modes and has a compact structure.First of all,the structure of IRC technique is introduced.The principle of this compensator is demonstrated through a practical example,and then the scope of this technique,the design steps and the derivation process are introduced.Aiming at the problem that the system has extremely high frequency resonance and can not be eliminated sufficiently,a modified IRC technique is proposed,which can eliminate the ultra-high frequency resonance effectively,without sacrificing the computational complexity and structure complexity at the same time.The transient performance of the system is improved without sacrificing computational complexity and structure complexity.Then,the IRC control technology is used in DSA HDD head positioning system.Aiming at the DSA head positioning model,a reasonable control scheme is proposed.Specifically,for a VCM actuator,a notch filter is used to eliminate the resonance mode,the first stage actuator mainly acts on the low frequency region.The secondary piezoelectric MA for high-precision positioning is controlled through an IRC compensator together with a notch filter,which attenuates resonances of MA sufficiently to achieve a necessary high bandwidth,the second stage actuator mainly acts on the high frequency region.The performance of the proposed novel DSA scheme is verified with comparison with those of the conventional SSA composite nonlinear feedback(CNF)control method and the dual-stage linear feedback control(LFC)method through simulation.The simulation results show that the proposed control scheme can get to the desired track in shorter time,and has almost no overshoot.Further,for the first time,the IRC technique and CNF control technique are combined and used in the DSA head positioning system.To be specific,the primary coarse actuator VCM for facilitating large motion is regulated by reduced order CNF control approach,which ensures rapid response and puny overshoot,and the secondary piezoelectric MA for high-precision positioning is controlled through an modified IRC compensator,which attenuates resonances of MA sufficiently to achieve a necessary high bandwidth.Finally,we demonstrate the effectiveness of the proposed control scheme and compared with those of the conventional single-stage actuated SSA CNF method and the dual-stage LFC method.The simulation responses tell that the proposed control scheme can enhance transient performance of the DSA head positioning system.Finally,step disturbance and periodic impulsive disturbance are added to the control system,respectively,which verifies that the proposed control system has desirable robustness.