| This thesis deals with the nonlinear hysteresis modeling,pressure-length hysteresis characteristics and force-length hysteresis characteristics analyses of a Mckibben pneumatic artificial muscle(PAM).The following contributions have been made.In hysteresis modeling of the PAM,the generalized Prandtl-Ishlinskii(GPI)model with hyperbolic and exponential envelop functions were introduced,which are widely used in the fields of piezoelectric ceramics and intelligent materials.By investigating the characteristic of the hysteresis curve of the PAM,a modified GPI model formulated using modified generalized play operators constructed by arc tangent envelope functions was proposed.By comparing the genetic algorithm and LM algorithm,the LM algorithm was selected for the identification of the parameters in the model.In the study of pressure-length hysteresis characteristics of the PAM,the pressure-length hysteresis curve of PAM was obtained with the aid of an experimental setup.The validity of the modified GPI model was demonstrated by comparing the responses of three models with the measured hysteresis loops of the PAM.Besides,the effectiveness of the inversion of the proposed model in compensating the asymmetric hysteresis nonlinearities of the PAM was illustrated via simulations.In the study of force-length hysteresis characteristics of the PAM,the isobaric experiment and constrained experiment were carried out with the aid of an experimental setup of force-length hysteresis characteristics.Then,the force-length hysteresis curve of the PAM was obtained.In order to avoid the process of solving the inverse model,the hysteresis models were directly employed to capture the inverse curve of the force-length hysteresis.The responses of three models were compared with the measured hysteresis loops.The experimental results showed that the GPI model with exponential function has a better capability of characterizing the force-pressure hysteresis behavior of the PAM. |
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