Active Shimmy Control System

A T-37 nose gear is modeled as a multiple lumped mass system with four torsional-degrees-of-freedom and one lateral-degree-of-freedom. Fuselage flexibility is incorporated and a Von Schlippe tire model is used. The equations of motion for various input conditions are solved using measured gear properties. An Active Shimmy Control System is incorporated in the analytical model. A feedback signal proportional to angular velocity is used to control the hydraulic actuator pressure. The equations of motion for the gear with active control are solved for the same inputs as for the passive gear and their responses are compared. System parameter values were varied about the nominal measured values to determine their effects for both active and passive systems. A breadboard Active Shimmy Control System was built based on the model results. A test program was performed establishing regions of shimmy for the passive gear. The same conditions were repeated with the active system. Substantial improvement was seen. A comparison with the theoretical predictions showed good correlation.