Study On Braking Delay Characteristic Of Associated Braking System Of Heavy Equipment Transporter

The associated braking system in this thesis consists of the brake system and the hydraulic retarder and has certain braking delay characteristic.This characteristic would incur semitrailer colliding tractor during downhill braking of the heavy equipment transporter(tractor-semitrailer).Then the braking direction stability of the transporter would be negatively affected,resulting in significant casualties and property loss.Therefore,it is of great realistic meaning to research on the braking delay characteristic of the associated braking system for the heavy equipment transporter.To begin with,the simulation model of the associated braking system was built in AMEsim and SIMULINK and the braking delay characteristic of it was analyzed.The dynamic response characteristics of the brake torque of each drum brake were gained by using the experimentverified simulation model of the braking system.The dynamic response characteristic of the brake torque of hydraulic retarder was gained by using the simulation model of it.The results showed that the semitrailer brake working delay time increased from 0.16 s to 0.20 s and the growing rate of the brake torque of the rear wheels of tractor rose after adding the work of the hydraulic retarder by comparing the dynamic response characteristics of those two sorts of brake torque.Secondly,the influences of the braking delay characteristic of the associated braking system on the braking direction stability of the heavy equipment transporter downhill braking were analyzed.Based on the ten-degree-of-freedom mathematical model of the transporter,it was concluded that when there was no lateral disturbing force the braking delay characteristic could increase the colliding force between tractor and semitrailer.Besides,when there was lateral disturbing force the braking delay characteristic could increase yaw rates of tractor and semitrailer.The downhill braking process of three sorts of lateral disturbing torque was simulated by using the experiment-verified simulation model of the transporter in Trucksim and simulation model of the associated braking system.Simulation results showed that the braking delay characteristic could increase the lateral motion of the transporter in each condition by comparing lateral displacements,yaw rates and splice angles of the tractor and semitrailer with and without braking delay.Besides,the bigger lateral force,the worse effect.Last but not least,a modification scheme of reducing braking delay time was proposed and verified.The simulation models of the modified associated braking system and its control strategy were built in AMEsim and SIMULINK respectively based on the scheme layout and principle.The simulation results showed that the modification scheme could reduce the braking delay time by 0.19 s and effectively suppress the lateral motion of the transporter by simulating and analyzing.Furthermore,by simulating downhill process with different braking speeds,it was concluded that the bigger braking speed,the weaker validity of the scheme.