A Method for Quantifying Automobile Brake Creep Groan Intensity Based on Friction-Induced Vibration and Noise

To quantify the intensity of automobile brake creep groan, both experimental and analytical studies are innovatively conducted on the friction-induced vibration and noise of the disc brake in this paper. Experimentally, three factors, brake disc initial temperature, terrain, and gear position, are comprehensively contemplated to design six different test conditions, based on which a creep groan vehicle road test is conducted. Depending on the subjective evaluation and statistical analysis of the annoyance degree caused by vibration and noise in the starting and braking process under different test conditions, the influence of each factor on creep groan intensity is obtained. By processing the brake caliper and lower suspension arm acceleration and the interior sound pressure signals acquired in the test, the occurrence conditions and transient dynamic characteristics of creep groan are explored. One of the creep groan vibration modes is triggered by the rapid removal of the force exerted on the brake pedal when the vehicle starts at an extremely low speed, which presents intermittent impact and chaotic characteristics. The other vibration mode shows periodic harmonic characteristics, whose energy is concentrated on specific frequencies in the form of frequency doubling. This vibration mode occurs when continuously maintaining a low brake oil pressure or slowly releasing the force exerted on the brake pedal during the vehicle low-speed starting process, the velocity-displacement phase-plane portrait of which shows a stable limit cycle of stick-slip motion. Analytically, four vibration indexes and four noise indexes are established to evaluate the intensity of creep groan, the validity of which is verified by linear regression analysis. Finally, by combining all effective indexes, multiple linear regression analysis is performed, based on which the mapping relationship between the subjective evaluation of creep groan and effective indexes is obtained. The results demonstrate that the combination of the logarithmic vibration dose value of maximum brake caliper acceleration pulse and the loudness of interior noise can accurately describe the annoying degree caused by creep groan. The regression model can quantify and predict creep groan intensity of the test vehicle under different test conditions, which has guiding significance for engineering applications.

Studies on Operational Frequencies of Controls on Self-propelled Combine Harvesters in India

A study was conducted to measure the operational frequencies of various controls on self-propelled combine harvesters and to categorize them into frequently and infrequently operated controls. The operational frequency of controls on 10 combine harvesters of different makes and models were measured during harvesting of wheat crop. The frequency of use of frequently operated controls viz. header assembly control lever, ground speed control lever, gear shift lever, brake pedal, and clutch pedal ranged 232-484, 43-170, 41- 135, 42-140, and 66-162 action.h-1, respectively. The percent time distributions of operation of controls were 44.84, 13.40, 12.21, 13.10, and 16.42%, respectively. The controls on the combine harvesters used repetitively that require high level of human effort. Therefore, to accommodate 90% of user population, the most frequently operated controls should preferably be placed in the optimum reach zone, and infrequently used controls can be conveniently placed within maximum reach zone of operators’ reach envelope.

An ultrasonic sensor based automatic braking system to mitigate driving exhaustion during traffic congestion

Traffic congestion has been the most tiresome encounter since the initiation of vehicle advancement. Many braking systems have been designed by researchers in previous studies, but this study is primarily focused on a braking system that is affordable to all because it is based on a simple Arduino-controlled system. Moreover, it is assistive on everyday traffic commutes rather than highway driving, which is relatively rare for normal drivers. As more and more vehicles crowd the roads, the more problematic it is becoming for the drivers, which is ultimately leading toward increment in the frontal car accidents. In this study, an electro-mechanical braking system has been deployed that assists the driver during the jam-packs by measuring the exact distance between the driven and forthcoming vehicle or any obstacle by applying the brakes without the driver pressing the brake pedal to ultimately bring the vehicle to a halt without any fear of vehicle collision. An ultrasonic sensor is used at the front bumper grille that measures the distance between the two closing vehicles. The total time to halt the vehicle has been calculated as 0.6 s, while the critical distance for the sensor has been set as 1-m. Furthermore, the stepper motor drivers are set at the maximum current output of 2.5 amps with a 12-volt battery connected in parallel to the motors. It is found that theoretical stopping time is in good agreement with the experimental stopping time to completely press the brake pedal and halt the car.

Experimental Research on the Effectiveness of Speed Reduction Markings based on Drivers’ Operating Performance: A Driving Simulation Study

Speed reduction markings (SRMs), which are widely used on highways and urban roads in China, are designed to inform drivers of the upcoming road conditions and thus encourage them to reduce travel speed. The objective of this paper is to test the effectiveness of SRMs on drivers’ operating performance and decision to decelerate in downhill segments on urban roads. Data of gas and brake pedal use was collected in a driving simulator experiment, and a subjective questionnaire survey was conducted. Two indicators—the operating frequency and operating power—were proposed to evaluate drivers’ operating performance due to SRMs. Results of the subjective questionnaire study showed that the majority of subjects were affected by SRMs while driving through downhill segments with distinct roadway grades (3%, 2%, 1.5% and 1% in experimental scenarios). In terms of the operating frequency, the results of the analysis of variance with repeated measures (rANOVA) and the contrast analysis (S-N-K method) showed that transverse speed reduction markings (TSRMs) were significantly effective in influencing drivers’ frequency of letting off the gas pedal when roadway grades of downhill segments were 3%, 2%, and 1.5% (p<0.05), while longitudinal speed reduction markings (LSRMs) had little effects; both types of SRMs are effective in increasing the frequency of pressing the brake pedal in all four downhill segments. For the operating power, the gas pedal power was significantly affected by TSRMs in all four roadway scenarios; TSRMs also tended to increase the brake pedal power when the roadway grades were 2% and 1.5%, while both types of SRMs had similar effects in road sections with roadway grades of 3%.