# A Model-Based Investigation of the Performance Robustness of the Deflector Jet Servo Valve
## 7 Conclusions  
In view of the complexity of the deflector jet valve, the assumptions connecting the fundamental jet theory with the actual valve structure are quite essential. They provide a framework for applications of specific theorems and determine the effective scopes of diverse formulas and the interface parameters for formula switching. To a considerable extent, these assumptions are confirmed by numerical simulation and experiments. Therefore, the theoretical model based on them can provide a distinct and logical description of the flow pattern in the deflector jet valve. Furthermore, the static pressure performance of the deflector servo valve can be studied theoretically based on our three-dimensional mathematical model. The uncertainty of the pressure indices of servo valve products, a common problem in actual scenarios, can originate from the installation error of the deflector and the machining error of the shunt wedge. For the balance pressure--the receiver pressure with the deflector centered--the two error sources, within a range of 10 microns, can bring about 1.2% and 7.4% fluctuations, respectively. Additionally, for the pressure gain, the induced fluctuations can reach 1.3% and 3.6%, respectively. That is, the error of the shunt wedge width can result in remarkable performance variation, especially for the balance pressure. It is discovered that the deflector approaching the shunt wedge leads to rapid deterioration of performance robustness against errors, which can magnify the inconsistency of the pressure indices of servo valves. However, as long as the deflector is not too close to the shunt wedge, the performance fluctuation will be dictated by the width error of the shunt wedge. Hence, in the actual production of servo valves, the machining accuracy of the shunt wedge and non-negative errors of the deflector jet distance should both be guaranteed to achieve more stable product performance. Specifically, the width error of the shunt wedge should be limited between \(-0.6\)\(\upmu\)m and \(0.6\)\(\upmu\)m to guarantee that the fluctuation of the balance pressure is less than 1%. Conceptualization, Y.R. and H.Y. ; methodology, H.Y. and Y.R. ; validation, Q.M. and H.H. ; formal analysis, Y.R. and Q.M. ; investigation, Y.R. and H.Y. ; resources, Z.Z. ; writing--original draft preparation, H.Y., Q.M. and Y.R. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Natural Science Foundation of China (grant number 51775032) and the Foundation of the Key Laboratory of Vehicle Advanced Manufacturing, Measuring and Control Technology, Beijing Jiaotong University, Ministry of Education, China. Not applicable. The data will be made available from the corresponding author upon reasonable request. The authors declare no conflict of interest. [PERSON]; [PERSON]; [PERSON]; [PERSON] Model Construction and Performance Degradation Characteristics of a Deflector Jet Pressure Servo Valve under the Condition of Oil Contamination. _Int. J. Aerosp. Eng._**2021**, _2021_, 8840084. [CrossRef]
* [PERSON] and [PERSON] (2014) [PERSON]; [PERSON] Development of a deflector-jet electrohydraulic servovalve using a giant magnetostrictive material. _Smart Mater. Struct._**2014**, _23_, 115001. [CrossRef]
* [PERSON] (2011) [PERSON] Fluid Metering Using Active Materials. Ph.D. Thesis, University of Bath, Bath, UK, 2011. * [PERSON] et al. (2015) [PERSON]; [PERSON]; [PERSON] Optimal design for amplifier of jet deflector servo valve. _Mach. Tool Hydraul._**2015**, _43_, 11-15. * [PERSON] (2015) [PERSON] Jet Pipe Servo Valve Flow Modeling and Characteristic Research. Master's Thesis, Wuhan University of Science and Technology, Wuhan, China, 2015. * [PERSON] (2006) [PERSON] Analysis and Experimental Research of pre-Stage Jet Flow Field in Hydraulic Servo Valve. Master's Thesis, Harbin Institute of Technology, Harbin, China, 2006. * [PERSON] and [PERSON] (2016) [PERSON]; [PERSON] Simulation based on Fluent for pre-stage of deflector jet servo valve. _Chin. Hydraul.