This paper discusses modeling and validation of unsteady flow blocks for hydraulic arms. The proposed model is similar to the look-up table but does not need any flow sensors. The proposed model is identified by experiment with a hydraulic arm and the nominal nonlinear model and compared with conventional model using the Bernoulli principle. The validity of the proposed model is confirmed via on-line validation experiment with the initial pressure measurement only.

In recent years, the computational numerical analysis makes it possible to find out various kind of unknown phenomenon in the fluid power systems due to rapid improvements of computer. The three dimensional transient CFD (Computational Fluid Dynamics) analysis can be a powerful tool for understanding the transient flow phenomenon inside pumps, valves and other hydraulic components. It can be also used for analyzing the pulsation phenomenon such as pressure and flow ripple in the hydraulic circuits. The aim of this report is to study on the analyzing method of the pulsation transfer characteristics of hydraulic circuit components by the CFD approach. A rigid pipe for the hydraulic line and a quarter wavelength side branch silencer are chosen as the analyzed hydraulic components. The transient CFD analysis is conducted to obtain the time history pressure and flow ripple at inlet and outlet of component. These time domain data are converted into the frequency domain by FFT, and the pulsation transfer characteristics which is represented by the four pole transfer matrix can be obtained as the frequency dependent characteristics. The results are compared with the theoretical and experimental results to verify the accuracy. The investigations about the CFD settings are also carried out to acquire the knowledge of calculation settings for pulsation phenomenon in the fluid power system.

Pneumatic rubber artificial muscle is attracting attention as an actuator having high cooperativeness with human because of its feature of being flexible and lightweight. The authors have developed Straight fiber type pneumatic artificial muscle (SF-ARM), which is a high power, highly displaced pneumatic rubber artificial muscle. Although SF-ARM has excellent contraction characteristics, it has a problem of short fatigue life. Therefore, in this study, focusing on strain-induced crystallization of natural rubber, the fatigue life of SF-ARM has been extended. First, strain-induced crystallization of natural rubber were confirmed by wide angle X-ray diffraction. Next, analysis of strain concentration in the vicinity of the crack was performed by the finite element method. Finally, a fatigue life test of SF-ARM was carried out to confirm the effect of prolonging the fatigue life by using strain-induced crystallization.