Agricultural tractor brake linkage efficiency prediction and correlation using Flexible Multibody Dynamics model

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 with theoretically-based mechanical advantage calculations. This is due to various factors such as linkage transmission angle, elasticity, and friction in joints not considered, which contribute to loss in force transfer. 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 model for brake linkage system for three different tractors developed with flex bodies using ADAMS/View software. Coulomb friction model and LuGre friction modeling methodologies used to describe friction in joints. The force of the brake pull rod of the simulation model is correlated with measured test data shows above 90% correlation. The developed method can be adopted to design an efficient brake linkage system for an agricultural tractor during the front-loading stage of the design.