Brake Torque Variation Research Articles

Investigation of Brake-judder through Caliper Vibrations due to the Effects of Friction Pad Properties, Disc Thickness Variation and Brake Torque Variation using a Dynamometer

There is a budding demand in the automotive industry for discovering the causes of brake judder and numerous mathematical models for analysis and simulation have been established. Since most of the data and knowledge are hidden within automobile manufacturers, it is still a mystery to unravel and get a clear picture. Judder was reported on the field during vehicle testing with a subjective assessment of Pad A (highlighted in table 1). The aim was to investigate the problem at the brake component by altering pad grades since it was within the scope of the study. Therefore, to save the time of running the vehicles and keeping the least variables from the 4M (Material, Method, Machine, Man), 8 combinations of friction pads were taken on an inertia brake dynamometer and deals with judder arising from the disk brake assembly only. This paper provides a novel approach by running various permutations and combinations of friction pads and interlinking caliper vibrations with the factors such as Brake torque variation (BTV), disc thickness variation (DTV), and friction pad properties by DOE (Design of experiment) analysis. It also provides some insight on the causes, types of brake judder and further gives quantifiable results which determine the bandwidth of the factors based on the experimental results. The paper is structured as follows: the introduction and causes to judder are covered in section 1. Materials and methodology in section 2, Results in section 3, and conclusion in section 4.

Frictional coefficient depending on active friction radius with BPV and BTV in automobile disc braking system

The present paper theoretically investigates the behaviour of frictional coefficient considering variants as active friction radius, brake force variation (BPV) and brake torque variation (BTV) in automobile disc brake system. The variations in the frictional coefficient on the piston side of the rotor disc and on the non piston side has been tracked with the use of equations obtained for the disc brake system under equilibrium condition .The effect of parameters like active friction radius, BPV and BTV has been studied as per the computations of the estimation algorithm. The formulated equations were solved by using the input parameters acquired using the braking system and predetermined values. The comparison of estimated frictional coefficient from numerical output is in agreement with vis-à-vis corresponding similar computed from the virtual braking system model in the Simulink. The results indicated that highest frictional coefficient of 0.7 was obtained on the piston side of the rotor disc and active friction radius is predominantly the impact factor for frictional coefficient.Keywords: Automobile, Mechanical, Frictional Coefficient, disc brake, active friction radius, BPV and BTV

Active Brake Judder Compensation Using an Electro-Hydraulic Brake System

Geometric imperfections on brake rotor surface are well-known for causing periodic variations in brake torque during braking. This leads to brake judder, where vibrations are felt in the brake pedal, vehicle floor and/or steering wheel. Existing solutions to address judder often involve multiple phases of component design, extensive testing and improvement of manufacturing procedures, leading to the increase in development cost. To address this issue, active brake torque variation (BTV) compensation has been proposed for an electromechanical brake (EMB). The proposed compensator takes advantage of the EMB's powerful actuator, reasonably rigid transmission unit and high bandwidth tracking performance in achieving judder reduction. In a similar vein, recent advancements in hydraulic system design and control have improved the performance of hydraulic brakes on a par with the EMB, therefore invoking the possibility of incorporating the BTV compensation feature of the EMB within hydraulic brake hardware. In this paper, the typical characteristics of electromechanical and electro-hydraulic brake systems are presented. Based on the experimental results, the feasibility of active BTV compensation on the electro-hydraulic brake (EHB) systems is discussed. Furthermore, a BTV compensation algorithm designed for the EMB is presented and is shown to be applicable to the EHB. Using an experimentally validated model of BTV, the compensation was performed on a hardware in-the-loop EHB test rig. The preliminary results demonstrate the potential of using an EHB to compensate for brake judder.

Vibration path analysis and optimal design of the suspension for brake judder reduction

Brake judder is abnormal vibration, which is mainly generated by uneven contact between the brake disc and pad. The abnormal vibration from BTV (Brake Torque Variation) is transferred to the suspension and the steering system during braking. In this paper, judder simulation is carried out using a multi-body dynamic analysis program to analyze the relationship between judder and the transfer mechanism, which consists of the suspension and the steering system. In order to verify the analytical model, test results are compared with the simulation results. A sensitivity analysis is also carried out. In addition, an optimization method is presented for judder reduction, using the design of experiments.

Adaptive Brake Torque Variation Compensation for an Electromechanical Brake

A novel method for attenuation of brake judder directly at the source is proposed, utilizing an electromechanical brake to actively compensate for the variation in brake torque that causes judder. Taking advantage of the high-bandwidth closed-loop clamp force tracking performance offered by an electromechanical brake, an adaptive compensator is designed to estimate the brake torque variation (BTV), and to produce a compensating clamp force command to cancel it. The compensator is tested over fixed and varying BTV frequencies by employing a production-ready prototype EMB. It is demonstrated that significant BTV attenuation is obtained using the proposed approach.

Brake Torque Variation on Wave Type Brake Disc for Motorcycles

Brake Torque Variation on Wave Type Brake Disc for Motorcycles

Brake dynamometer model predicting brake torque variation due to disc thickness variation

In this study, the mathematical model for a brake system in a dynamometer is proposed to identify brake torque variation (BTV), and correlations between the dynamo test and simulation are determined. The interaction between the pads and the disc on the contact patch is simply modelled as a point-contact element and the transient response analysis in the time domain is introduced. The model indicates that the amount of BTV is linearly proportional to the pad stiffness, the friction coefficient, the disc thickness variation, and the effective radius of the brake pads. To verify the analytical model, a brake dynamometer is used and additional material tests are carried out. The dynamo test shows that the suggested model has reasonable accuracy in predicting the BTV of a brake system.

Disc brake judder considering instantaneous disc thickness and spatial friction variation

Brake judder is a braking-induced vibration. The character of judder is typical of forced vibrations passing through a critical speed. No specific friction characteristic is needed for judder to occur. In two previous models, i.e. a rotor-stator model and a whole vehicle model, the vibration during a brake application was simulated. The vibrations were assumed to be driven by a brake torque variation (BTV) during a wheel revolution. The BTV was assumed to be proportional to the brake pressure variation (BPV) which was measured. Moreover, the proportionality constant was assumed to be independent of the braking conditions. Verifying measurements were made on a street going vehicle with strong disc thickness variation (DTV) on one of its front wheels. The measured vibration variation during braking was predicted almost exactly by the models. However, the maximum measured vibration level could only be approximated. In the present paper a more accurate analysis of the measurements was found to improve strongly the agreement between predicted and measured vibrations. Hence, the deviation in slope between measured and experimentally generated curves was markedly reduced by replacing the overall mean values of brake pressure level, etc. by slowly varying time functions. The new extended model of the present paper takes into account that the BTV may be generated by variations in normal force (i.e. BPV) and other synchronous variations (called BXV), e.g. spatial friction variation and variation of the equivalent brake radius. The result indicates that BXV may be induced by high BPV levels. Even at judder vibrations primarily caused by heavy DTV (20 μm or more in the cold state), there may be considerable contributions to the vibration level from other synchronous disturbances, i.e. BXV. Further, it was found that the pad stiffness increases with the brake pressure. For such a pad stiffness characteristic, an increase of the DTV level (for whatever reason) by 50 per cent might result in more than a 100 per cent increase in the corresponding BPV and BTV levels. Hence, a progressive pad is more sensitive to increases of the DTV level than a linear pad would be.

실차 상태에서의 제동시 이상떨림 현상에 관한 실험적 연구

The study presents a new testing and analysis method for brake judder on vehicle. For the identification of the excitation mechanism of a brake judder, it is necessary to measure the dynamic brake disc geometry during braking on vehicle. The non-contact sensor system was used to monitor the brake disc geometry. Brake torque variation (BTV) caused by disc thickness variation (DTV) is the primary excitation for brake judder. The mechanical effects generating BTV are linked not only to initial manufacturing tolerances but also to uneven wear. Therefore, the brake disc geometry should be strictly managed to initial condition. The aim of this study has been to measure the dynamic DTV and runout on vehicle and analyze the influence of test parameters on brake judder and compare the disc component with vehicle matching about the DTV Profile. As a result of this study, The amplitude of brake judder is proportional to vehicle speed and fluid pressure fluctuation on braking. The major sources of brake judder are directly related to disc thickness variation and side runout variation of corner assembly (disc, hub. bearing).