Li Q. Discrete electrohydraulic positioning actuator with software control

The thesis is devoted to the development of a low-cost programmable electrohydraulic position actuator with discrete action, which is capable of performing positioning motion of large mass with the programmable discretization and a high working speed. The application of the developed actuator in hydraulic equipments will increase their productivity. This is due to the increase in the working speed and response speed of the actuator through the rational selection of its structure and positioning algorithm. Based on the analysis of technical solutions of known electrohydraulic positioning actuators, the four main positioning methods and the properties of the actuators that they determine were revealed. The factors affecting the properties of the actuators were determined and a quantitative assessment of their influence was carried out, taking into account the positioning methods. The relationship between the structure of electrohydraulic positioning actuators and their properties was revealed. And the direction of development of the structural solution for an electrohydraulic positioning actuator with a set of desired properties was determined. A mathematical model of the electrohydraulic positioning actuator was established, which is characterized by a modular organization considering the nonlinear friction sub-model LuGre, as well as the asymmetry of the hydraulic cylinder. The correctness of the developed mathematical model was confirmed by comparing the simulation and physical experimental results. The potential performance of the actuator in a discrete control method with a focus on braking processes was researched, which showed that the braking time and the maximum pressure in the hydraulic cylinder chambers are determined by the velocity of the working body and the inertial load. The quantitative dependencies of the braking time and the maximum pressure on the velocity and inertial load of the working body were determined in the case of zero response time of the spool, where the velocity ranges from 0.311 m/s to 1.228 m/s and the inertial mass ranges from 17 to 57 kg. It was also revealed that the spool response time has a significant influence on the braking process of the actuator. It is shown that as the spool response time increases, the braking time and the maximum pressure and the level of pressure fluctuation in the hydraulic cylinder chambers decreases significantly. With a considerable increase in spool response time, this leads to an increase in braking time instead. The influence of the parameters and operating conditions of the actuator on the braking process was studied, and quantitative dependences between the braking time and the maximum pressure in the hydraulic cylinder chambers were obtained. The scheme of the discrete electro-hydraulic positioning actuator was justified and proposed, and a new scheme of a programmable adjustable throttle valve was developed. A two-stage positioning algorithm for the actuator with discrete action was developed. The positioning accuracy (positioning error), positioning process time, and permissible maximum positioning speed were determined by simulation experiments in the Simulink environment. The effectiveness of the developed technical solution and the proposed two-stage positioning algorithm was confirmed by simulation experiments, with the positioning accuracy is improved more than 11 times, the velocity of the working body is increased by more than 1.9 times, as well as the positioning process time is reduced by more than 1.3 times. Recommendations are provided for the selection of the actuator’s components and their control algorithm, which will ensure maximum performance under specific operating conditions.