Engine Test Cell / Hardware Design
Sneak circuit analysis for critical weapon system electronics and controls is performed by Southwest Research Institute (SwRI). These analyses typically involve munitions or weapon delivery and are performed to identify unintended circuit paths that could inadvertently alters the intended performance of the system, whether by causing unintended results or by preventing intended results from occurring.
Sneak Circuit Analysis Software
Sneak circuit analysis is performed using MIL-STD-1543B as a guideline and by blending the use of a commercially available software tool called Sneak Circuit Analysis Tool™ (SCAT™) with focused analytical techniques to identify and characterize potential operational hazards of a system or subsystem. CapFast is a CAE (formerly Canadian Aviation Electronics) tool that provides a method of capturing nodal connections within the circuits and the properties of the circuit components. The SCAT software systematically identifies nodal patterns associated with sneak circuits.
Sneak Circuit Analysis Process
- The electronic data is converted into the required format for the CapFast/SCAT analysis software.
- The software is run using multiple initial conditions.
- The CapFast/SCAT outputs are analyzed by the project engineers to determine whether any sneak circuit conditions were present.
SwRI performed stiffness, strength, and durability analysis on the trainable gun mount (TGM). The stiffness finite element analysis (FEA) was used to predict the modal response of the TGM, and modal testing was performed to validate the FEA. The modes determined by this analysis were incorporated in the dynamic models used to analyze controls. The strength and durability FEAs were used to determine whether the TGM was adequately designed to survive maximum loading conditions and repetitive loading conditions over the entire life of the TGM. SwRI participated in the final design of the TGM by identifying stiffness, strength, and durability issues and providing recommendations for overall and specific design improvements. In addition, a damage tolerance analysis (DTA) was performed on the aircraft support structure for the TGM.
SwRI engineers performed analysis of sneak circuit paths and other electrical system effects of the high transient currents to identify design alternatives for a robust, reliable, and safe installation. In addition, they performed system dynamics analysis of the control systems. They generated nonlinear and linear models for the analysis. The linear models were created to aid the controls design process and could be used for bode plots, root locus plots, and other linear control tools. Engineers created the nonlinear model using Simulink®, which encompassed such complexities as:
- Base motion of the aircraft
- Nonlinear hydraulic servo valve effects
- The gun recoil force profile
- Digital control effects
- Effects of dynamic correlation between the two axes
SwRI engineers compared and adjusted the model to match TGM step response data. They participated in the in the final design the TGM controls by simulating controls proposed by Boeing and recommending improvements. The nonlinear model provided the program a method to check the effectiveness of the controls before installing the TGM on the aircraft.
mechanical systems analysis • electrical systems analysis • sneak circuit • critical weapon system • sneak circuit analysis • MIL-STD-1543B • SCAT • CapFast • trainable gun mount