The significant features of screw transmission are effort-saving and self-locking. Based on this, a screw-rod-type actuator is proposed, which is driven by a nut swung spirally together with piezoelectric transducers. The actuator consists of three parts: a nut fastened to a hollow cylinder, a precise screw rod, and two orthogonal piezoelectric vibrators worked on d₃₃ mode. The screw rod is forced to rotate and translate by traveling wave within the helical surface of nut, which is generated by two vibrators. First, the actuator’s running mechanism is preliminarily illustrated. Second, modal analysis and optimal design of the stator are performed through finite element method. Finally, the prototype actuator is manufactured and tested. The experimental results have proven that this driving manner is feasible, and the main characteristics are as follows: the stable working frequency is about at 9.5 kHz, and the maximum no-load speed and output force are approximately 61 r/min and 2.1 N, respectively, under 300 V_pp.

A directional valve is a core component of the electro-hydraulic shakers in fatigue testing machines, controlling the cylinder or motor that drives the piston for reciprocating linear or rotary motion. In this article, a high-speed rotating directional valve with a symmetrical flow channel layout is designed to optimize the force on the valve core of the directional valve. A comparative analysis is conducted on the flow capacity of valve ports with different shapes. A steady-state hydrodynamic mathematical model is established for the valve core, the theoretical analysis results of which are verified through a Computational Fluid Dynamics (CFD) simulation of the fluid domain inside the directional valve. A prototype of the rotatory directional valve is designed and manufactured, and an experimental platform is built to measure the hydraulic force acting on the valve core to verify the performance of the valve. The displacement curves at different commutation frequencies are also obtained. The experimental results show that the symmetrical flow channel layout can significantly optimize the hydraulic force during the movement of the valve core. Under a pressure of 1 MPa, the hydraulic cylinder driven by the prototype can achieve a sinusoidal curve output with a maximum frequency of 60 Hz and an amplitude of 2.5 mm. The innovation of this design lies in the creation of a directional valve with a symmetric flow channel layout. The feasibility of the design is verified through modeling, simulation, and experimentation, and it significantly optimizes the hydraulic forces acting on the spool. It provides us with the possibility to further improve the switching frequency of hydraulic valves and has important value in engineering applications.