hard disk driver
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Author(s):  
Beibei Ren ◽  
Qing-Chang Zhong

In this paper, the UDE (uncertainty and disturbance estimator) based robust control is investigated for a class of non-affine nonlinear systems in a normal form. Control system design for non-affine nonlinear systems is one of the most difficult problems due to the lack of mathematical tools. This is also true even for the exact known non-affine systems because of the difficulty in explicitly constructing the control law. It is shown that the proposed UDE-based robust control strategy leads to a stable system. The most important features of the approach are that (i) by adding and subtracting the control term u, the original non-affine form is transformed into a semi-affine form, which not only simplifies the control design procedure, but also avoids the singularity problem of the controller; (ii) the employment of UDE makes the estimation of the lumped uncertain term which is a function of control input, states and disturbances possible, rather than states alone; and (iii) it does not require any knowledge (e.g., bounds) about the uncertainties and disturbances, except the information about the bandwidth, during the design process. The stability of the closed-loop system is established. Effectiveness of the proposed approach is demonstrated through application to the hard disk driver control problem.



2009 ◽  
Vol 18 (6) ◽  
pp. 065010 ◽  
Author(s):  
Hao Sun ◽  
Zhichun Yang ◽  
KaiXiang Li ◽  
Bin Li ◽  
Jiang Xie ◽  
...  


2005 ◽  
Vol 54 (8) ◽  
pp. 3787
Author(s):  
Li Xin ◽  
Hu Yuan-Zhong ◽  
Wang Hui


Author(s):  
Xin Li ◽  
Yuanzhong Hu ◽  
Hui Wang

The static and dynamic properties of lubricant PFPE are important for the service durability and reliability of the computer head-disk device. Thus molecular dynamic simulations based on a coarse-grained, bead-spring model are adopted to study those properties. On the one hand, we investigate the static properties and infer the structure of both nonpolar and polar PFPE films. For a nonpolar PFPE film, there is a layering structure in the surface layer. And for a polar PFPE film, besides layering structure, there is a bi-polymer structure in the bulk layer. On the other hand, we investigate the dynamic properties and find that for nonpolar PFPE film, a precursor film around one atomic diameter thickness develops according to layering structure; while for polar PFPE film, besides a precursor film, a much steeper and slower spreading shape appears according to bi-polymer structure.



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