**6. Conclusion**

In this chapter, the methodology of optimal design of MRF-based devices was introduced. The chapter was started by a review of fundamentals and the theory behind MRF in section 2. In section 3, the operating modes used in MRF based devices were considered and several different devices featuring MRF are discussed. In the fourth section, optimal design methodology of MRF-based mechanisms was considered. In this section, firstly the necessity of optimal design and the state of the art were discussed. The magnetic circuit analysis and the modeling of MRF devices were then considered. In addition, the optimization problem of MRF devices was figured out and the methods to solve the problem were investigated. Section 5 dealt with a case study of MR valve optimal design. In this case study, several valve configurations such as single-coil MR valve, multiple-coil MR valve and annularradial MR valve were considered. The optimization problem is to minimize the valve ratio by which maximized the control range and pressure drop of the MR valves. The results have shown the significance and the effectiveness of the proposed optimization methodology. Base on this study case, the optimal design of other MRF-based devices such as MR dampers, MR brakes can be performed.

## **Author details**

376 Smart Actuation and Sensing Systems – Recent Advances and Future Challenges

Design Parameter

*t = 17.23 wc = 1.78 th = 7.43* 

*a=19.7 t = 10.6 wc = 6.38 th = 5.33* 

*b = 6.36 a =10.94 t = 5.84 wc=7.48 th = 3.35* 

*t = 8.6 wc= 3.1 th = 6.36*  Valve Ratio, Pressure Drop & Power

λ*opt*=0.033

Δ

λ

Δ

λ*opt*=0.024

Δ

λ

Δ

*Popt*=37.3*bar Nopt*=7.92*W*

*opt*=0.02296

*Popt*=48.62*bar Nopt*=16.5*W*

*Popt*=42.95*bar Nopt*=37.4*W*

*opt*=0.0293

*Popt*=64.4*bar Nopt*=29.1*W*

Consumption

*<sup>0</sup>*=0.08274

*P0*=28.2*bar N0*=83.2*W*

Initial Optimal Initial Optimal

λ

Δ*P0*=15*bar N0*=38.83*W*

λ*<sup>0</sup>*=0.0381

Δ

λ*<sup>0</sup>*=0.0355 *∆P0*=32.72*bar N0*=55*W*

λ*<sup>0</sup>*=0.041 *∆P0*=47*bar N0*=44.3*W*

In this chapter, the methodology of optimal design of MRF-based devices was introduced. The chapter was started by a review of fundamentals and the theory behind MRF in section 2. In section 3, the operating modes used in MRF based devices were considered and several different devices featuring MRF are discussed. In the fourth section, optimal design methodology of MRF-based mechanisms was considered. In this section, firstly the necessity of optimal design and the state of the art were discussed. The magnetic circuit analysis and the modeling of MRF devices were then considered. In addition, the optimization problem of MRF devices was figured out and the methods to solve the problem were investigated. Section 5 dealt with a case study of MR valve optimal design. In this case study, several valve configurations such as single-coil MR valve, multiple-coil MR valve and annularradial MR valve were considered. The optimization problem is to minimize the valve ratio by which maximized the control range and pressure drop of the MR valves. The results have shown the significance and the effectiveness of the proposed optimization methodology. Base on this study case, the optimal design of other MRF-based devices such as MR

[mm]

*t = 17 wc= 10 th = 6.5* 

*a=10 t = 5 wc= 10 th = 4* 

*b = 6 a =7 t = 7 wc= 10 th = 6* 

*t = 10 wc= 6 th = 8* 

**Table 3.** Optimization results for MR valve design

dampers, MR brakes can be performed.

Valve Type

valve

valve

valve

valve

Single-coil annular

Two-coil annular

Three-coil annular

Annular-radial

**6. Conclusion** 

Quoc-Hung Nguyen and Seung-Bok Choi *Mechanical Engineering, Inha University, Korea* 

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