Servo system modeling and reduction of mechatronic system through finite element analysis for control design

The interaction between structural components flexibility and closed-loop servo system determines primarily the performance of all electro-mechanical systems. Taking hard disk drives as a typical example of high-precision servo systems, this paper focuses on servo system modeling and reduction through quantitative analysis using finite element method. A finite element model of a full head actuator is established. Detailed dynamic characteristics of the head actuator assembly have been investigated. Combined with analytical results, a full model for the servo control of the assembly has been established. The model can be reduced by modifying the full modal matrix, selecting modes based on dc gain and peak gain under constrained operating conditions. Only the most important modes were kept for servo system modeling. This results in a general procedure to analyze the characteristics of servo system that can be adequately modeled by finite element method for servo control design and simulation. Frequency response functions between the VCM input current and velocity response of the slider were measured using LDV to validate the model for further analysis. Both simulation and experiments for servo controller design and evaluation have been conducted in this paper. The results show that the modeling method can be used for the simulation of finial servo control design to achieve effective and integrated system design for mechatronic systems.