In agricultural tractors, braking actuation is usually done through control linkages consisting of a series of connected four-bar linkages with multiple pivots from the pedal to the brake pads. The quality of force transmission is critical as it directly affects the braking performance of the tractor.
Forces measured at the end of the control linkage or brake pull rod often show deviation from theoretical values based on mechanical advantage calculations. This is due to various factors such as linkage transmission angle, elasticity, and friction losses in joints. A standardized simulation method needs to be developed and validated to predict the losses in the control linkage system.
In this paper, the author proposes a simulation approach using multi-body dynamics, which includes contribution factors such as transmission angle, linkage elasticity, and friction in joints. MBS models for brake linkage systems for three different tractors were developed with flex bodies using ADAMS/View software. Coulomb friction and LuGre friction models were used to describe friction in joints.
Force on the brake pull rod of the simulation model correlated with measured test data, showing above 85% correlation. The developed method can be adopted to design efficient brake linkage systems for agricultural tractors.