Estimation and reduction of lateral deviation (brake pulling) of a vehicle due to difference in Left and Right wheel brake force

Paper #:
  • 2017-01-2505

  • 2017-09-17
It is well established that one of the causes of brake pulling during straight ahead braking of the vehicle is torque difference between Left and Right wheel brakes. This paper explains a method to estimate and reduce brake pulling of a Light commercial vehicle (LCV) caused by such a brake torque difference during panic braking. It is challenging to eliminate this unwanted brake pulling in shorter wheelbase LCV having all drum brakes and high center of gravity. A mathematical model is developed to estimate extent of brake pulling from known parameters like brake torque at each wheel, tire properties, steering geometry, vehicle center of gravity location etc. With the help of this model the sensitivity of each parameter change on vehicle pulling derived & it supported for optimizing the DOE. Vehicle tests have been done to measure extent of brake pulling along with measurement of brake torque and speed etc. Close correlation could be seen between the test results and derived mathematical model. Vehicle testing revealed that brake torque difference between LH and RH wheel can change considerably from start to end during a single braking event itself. In addition, brake torque difference changes significantly with brake temperature and pressure. When pulling due to brake force difference is in the same direction as wheel turning due to bump & brake steer, the extent of vehicle pulling increases considerably. This article also describes how to reduce brake pulling by changing steering geometry and by optimizing certain parameters of drum brakes. The same vehicle has been tested again after changing these parameters, and brake pulling is found to have reduced considerably as predicted by the mathematical model.
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