Modeling and Simulation of Shimmy Behavior in an Aircraft Steering Sys- tem Using Bondgraph-based Software

Resumo

Most aircraft steering architectures do not actuate the system during landing, allowing the aircraft to

align itself to the runway track. This lack of control results in a condition where the wheels may experience high-
amplitude and high-frequency oscillations, known as the shimmy effect. One of the methods for preventing this

phenomenon from happening is to connect the piston chambers to anti-shimmy valves, acting as a damper for
the steering oscillation. In this paper we present the modeling and simulation of shimmy in an aircraft steering
wheel using a bondgraph-based software. The paper presents a simplified model of a rack-pinion steering wheel
system under landing conditions. Later, anti-shimmy valves are included and their effect in the model dynamics is
evaluated. Tire-pavement interactions are modeled through the Pacejka Formula, informally known as the ”Magic
Formula”, which was adapted for the aeronautical context. Simulations are made using Simcenter Amesim 15.2,
where the model is implemented using components found on the Student Version library. The model fully captures
the shimmy behavior and allows one to visualize the importance of the anti-shimmy valve diameter on steering
dynamics.