Study on the effect of generalized coupled stiffness in the electro-hydraulic load simulator

The Electro-hydraulic load simulator (EHLS) is used to replicate aerodynamic hinge moment in real-time hardware-in-the-loop missile Simulations. As a passive kind of torque control system, the movements of loaded system resulted in so called surplus torque to loading system. The surplus torque problem is almost related to the performances of EHLS. Generally, the contributions of surplus torque are negative. But, there is no quantitative method to design a suitable coupled stiffness for "eliminating" surplus torque in electro-hydraulic load simulator (EHILS) at present. In our research works, the ultimate purpose is possible to improve the disturbed closed-loop bandwidth. This paper draws attention to a quantitative method in generalized coupled stiffness design which not treated surplus torque as disturbance, but as "compensation". Augment of the generalized coupled stiffness has a "two-direction" action characteristic. There must be an optimal generalized coupled stiffness which makes the "two-direction" action reach at the optimal state independently. We gave an equation to calculate this stiffness by shaping the curve of disturbed system in frequency domain and made "compensating" action of surplus torque reached at an optimal state under the precondition of linear load gradient. The simulation results show that the EHLS system "eliminates" surplus torque validly and ensures the system performances use this optimal generalized coupled stiffness.