Modeling and experimental research on zero-bias thermal stability of the torque motor for aviation electro-hydraulic servo valves

A permanent magnet torque motor’s (PMTM) zero is very easily shifted under the dual thermal changes of structure and material in a high-temperature service environment. The aero-engine electro-hydraulic servo valve’s service performance is greatly impacted by the thermal stability of zero bias. However, it is difficult for designers to maintain the stability of the servo valves’ zero position since the fundamental reasons of zero-bias and its effective suppression measures are still unclear. Aiming at this issue, the mechanism of the generation and evolution of the zero-bias of PMTM is analyzed deeply, and a zero-bias predictive model of PMTM is created by combining response surface methods and finite element analysis in this paper. Relative experiments are conducted, and the findings reveal that the practical and theoretical values of the zero-bias distribution characteristic parameters for batch PMTMs are all of the same order of magnitude. The greatest relative errors between theoretical and actual values for the output displacement of the feedback rod ball of PMTM at 30°C and 180°C are 10.6% and 10.7%, respectively. Additionally, the armature assemblies’ thermo-solid coupling deformation has the biggest impact on the thermal drift of zero-bias for PMTM at high temperature. The zero-bias of PMTM at room temperature can be efficiently suppressed by preferentially limiting the range of vertical difference between the four air gaps. In conclusion, this work offers a useful theoretical reference for studying the zero-bias of electro-hydraulic servo valves.