This article proposes a novel piezo rotary positioning device in which the rotation of the endeffector is generated by the friction driving mechanism principle. Two piezoelectric elements are utilized as motion sources. In this article, a complete study for design, finite element analysis, manufacturing, dynamic model, simulations and experiments is presented. The finite element analysis is applied to evaluate the designed device. Based on results of analysis on the finite element model, a prototype of device is manufactured. The driving resolutions of the endeffector of prototype can be achieved approximately 0.45×10 -3 rad when the driving voltage of 80 V with frequency of 1 Hz is applied. By taking in account of the nonlinear hysteresis of piezo actuators as well as the complexity of friction mechanism between the end-effector and the movable platform, the predicted dynamic model of the end-effector angular displacement is achieved. Simulations and experiments results show that the prediction model is in good agreement with the actual model. This provides a useful solution for designing and controlling of such rotary devices. So, this rotary device can be controlled automatically by a computer and it has a great potential application in practice.
The EHA (electro hydraulic actuator) has a notable advantage over conventional hydraulic actuators as it uses a closed-loop circuit, reducing the size and volume of oil, and eliminates pressure losses caused by valve orifices. However, accurate control performance of EHA is difficult to achieve using a traditional PID (proportional integral derivative) controller due to the strongly nonlinear, time-varying, and unknown dynamics of the system. Hence this paper seeks to address this problem by proposing a design of an intelligent controller for the EHA. The proposed adaptive fuzzy sliding mode controller (AFSMC) is developed as a hybrid of the adaptive, fuzzy logic, and sliding mode algorithms. To reduce costs and time, a virtual prototype approach is also proposed instead of experimentations to evaluate the performance of the proposed controller. The virtual model of the EHA is built in Amesime software, and then embedded into Matlab/Simulink where the AFSMC is developed and tested to obtain the position responses of the EHA. The results show that the AFSMC is highly successful and more efficient than the traditional PID at controlling the position of the piston accurately.
As well known, nonlinear vibration isolation models may offer potential effectiveness for isolating low frequency vibrations. Therefore, this paper will introduce a nonlinear vibration isolation model, featuring asymmetrical and quasi-zero stiffness characteristics. Firstly, the physical model of the nonlinear vibration oscillation is shown, including a semicircular cam-roller and wedge-roller mechanism, in which cylinder adding auxiliary tank is worked as an elastic element. Secondly, its dynamic stiffness is built and numerically simulated. Based on these, the parameters which effect on dynamic stiffness of the system are identified. The analysis results confirmed that the proposed model can attain the quasi-zero stiffness by adjusting the pressure inside the cylinder of the stiffness corrected stiffness. Moreover, increasing the auxiliary tank volume will decrease the asymmetry of the stiffness curve. This study will furnish a useful insight to analyze and design a quasi-zero stiffness vibration isolator.
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