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Technical Paper

Identification of Gear Shift Quality as a Key Attribute in Commercial Vehicle Development

Indian automotive market has grown extremely competitive in the recent past. In order to meet the ever growing expectations of the customers, automobile manufacturers are compelled to offer their products under superior quality with supreme comfort. Customers wish of high levels of tactile comfort in the cabin compartment and effortless operation of peripherals will result in negligible fatigue and a pleasant drive, needs to be duly fulfilled. One has to focus more on Gear shift lever and Steering wheel, which are being the most sensitive tactile points in an automobile. The gear shift lever knob is frequently used and significantly influences the perception of the shift comfort for a driver during actual vehicle application.
Technical Paper

Development of an optimized cooling system for a light duty Pickup truck

With the advent of most advanced diesel engines the demand for upgraded engine cooling modules capable of handling more heat rejection in a smaller space is surging. Moreover, the variance in the operating conditions, i.e., the simultaneous cooling demands for peak load as well as partial load in different ambient conditions of the vehicle operation, broadens the scope of development of a cooling system. Also, the cooling system needs to be configured judiciously so as to cater effective cooling at peak loads and efficient cooling at partial loads. This research paper deals with a cooling system developed using modularity approach in order to have a control over tuning of subsystems for varying operating conditions and also to achieve the performance targets with a compact design adhering to packaging constraints. Kuli simulation of different designed configurations were carried out for identification of best concept.
Journal Article

Study of Frequency Characteristics of Vehicle Motions for the Derivation of Inherent Jerk

Jerk in a vehicle is a feel of user which appears due to sudden acceleration changes. The amplitude and frequency components of the jerk defines quality of an engine or an AMT calibration tuning. Traditional jerk evaluation methods use amplitude (peak) of the jerk as a performance index and its frequencies are either used as weighing factor with amplitude or not taken into account. A method is proposed in this paper to quantify and differentiate the non-acceptable level of jerk which is perceivable to human body. Jerk is obtained by differentiating the acceleration data which contains the frequencies in the lower to higher range. Differentiation of such signal causes an amplification of undesired noise in both analog and digital circuits. This results in significant loss or disturbances in the useful data.
Technical Paper

Optimization of Commercial Vehicle Cooling Package for Improvement of Vehicle Fuel Economy

In a heavy commercial vehicle, the engine cooling package is designed by considering peak heat load on the vehicle cooling system from an engine end. In cooling systems, the major unit that consumes most power from the engine is the engine cooling fan. It was seen from the vehicle measured duty cycle data, for most of the time engine operates at part load condition. Regardless of demand from the engine cooling system, engine fan was operating continuously at equivalent speed of the engine. This results in continuous consumption of productive engine power from the fan end ultimately affecting vehicle fuel economy. The present study shows that low idle speed viscous fan has the potential to meet stringent engine cooling performance requirements and consumes less engine power throughout an actual vehicle duty cycle. Experiments were conducted on test vehicle with different fan speeds.
Technical Paper

Improvement in Vehicle Handling through Optimization of Steering System Compliance

Recent infrastructural developments and emerging automotive market in India has given an impetus to the transportation industry and has led to high end research activities in synchronization with growing customer demands and competition especially in last decade. Since average speeds in India has gone up from 50 kmph in the year 2000 to almost 100 kmph in 2011, even the Light Commercial Vehicles (5 to 9.6T) are gradually experiencing a shift from low speed to high speed goods carrier. These new age vehicles are developed with a driver centric outlook towards safety and comfort. They are better optimized and equipped to the changing needs of the consumer and road conditions. Increase in vehicle speed poses many challenges in terms of occupant safety and control. In view of this, refinement of different vehicle handling parameters with respect to steering system compliance becomes far more critical.
Technical Paper

Effect of Steering System Compliance on Steered Axle Tire Wear

Subject paper focuses primarily on non uniform tire wear problem of front steered wheels in a pickup model. Cause and effect analysis complemented with field vehicle investigations helped to identify some of the critical design areas. Investigation revealed that steering geometry of the vehicle is undergoing huge variations in dynamic condition as compared to initial static setting. Factors contributing to this behavior are identified and subsequently worked upon followed by a detailed simulation study in order to reproduce the field failures on test vehicles. Similar evaluation with modified steering design package is conducted and results are compared for assessing the improvements achieved. In usual practice, it is considered enough if Steering Geometry parameters are set in static condition and ensured to lie within design specifications.
Technical Paper

Reduction of Steering Effort and Turning Circle Diameter for Mechanical Steering in Light Commercial Vehicles for Better Driver Comfort

New generation light commercial vehicles are expected to have lower steering effort, high self centering and less turning circle diameter covering large variety of wheelbases from 2.8 m to 4.5 m even with mechanical steering and keeping same number of total turns of steering wheel compared to old generation light commercial vehicles. To address above requirements, below parameters related to steering and rigid front axle were studied. 1 Caster angle of front axle 2 Steering compliance and Steering ball joint articulation angle 3 Front axle kingpin axial play 4 Steering gearbox ratio 5 Pitman arm length The effect of above parameters was studied in isolation and combination. This optimization has resulted in least steering effort and least turning circle diameter in light commercial vehicles with mechanical steering and option of power steering could be eliminated for cost reduction.
Technical Paper

Optimization of Brake Pedal Feel and Performance for Dual Air Over Hydraulic System on Light Commercial Vehicles

In current scenario, Light Commercial Vehicle segment (7 ton - 9.6 ton) is gradually experiencing a shift in the focus from being just a goods carrier to a vehicle which is developed to take care of driver's safety and comfort in terms of better ergonomics and aesthetics. As compared to their conventional counterparts the new generation Light Commercial Vehicles are better equipped and tuned to cater to the changing needs of the consumers. In view of this, refinement at the sub system level is becoming far more critical. On the same lines, the present work discusses a refined brake system for Light Commercial Vehicles where the conventional pneumatic system is replaced with Dual Air Over Hydraulic (DAOH) to achieve cost and weight advantages without compromising on its performance. However, during the development process, a lot of issues were observed with respect to the braking performance and the brake pedal feel.
Technical Paper

Investigation of Frequent Pinion Seal and Hub Seal Leakages on Heavy Commercial Vehicles

The automotive sector is going through a phase of stiff competition among various Original Equipment Manufacturers for increasing their profitability while ensuring highest levels of customer satisfaction. The biggest challenge for such companies lies in minimizing their overall cost involving investments in Research and Development, manufacturing, after sales service and warranty costs. Higher warranty costs not only affect the net profit but in turn it also affects the brand image of the company to a large extent in the long run. An effort is made here to target such warranty costs due to frequent tail pinion and hub seal leakages on single reduction/hub reduction axles of Heavy Commercial Vehicles in the field. A preliminary study involving the severity analysis of such failures is followed by a step by step investigation of these failures.
Technical Paper

Drive Cycle for Commercial Vehicles for Selection of Power Train to Get Optimum Fuel Efficiency

A drive cycle is a representation of standardized driving pattern. Drive cycle is typically represented as a vehicle speed, gradient Vs time developed to represent the driving pattern which is independent of vehicle configuration. A drive cycle has been developed for commercial vehicle based on real life data. Analysis was done on the representative data measured and recorded by real driving behaviors for different driving conditions (City, and highway), along with engine part load data and vehicle parameters like Gross Vehicle Weight (GVW), gear box ratios, rear axle ratio, tire size. The above set of parameters are simulated and validated on software. Estimation of fuel consumption (based on developed drive cycle) using validated software matches real time fuel consumption. This would eventually lead us to choose power train to get better output in terms of fuel efficiency.
Technical Paper

Evaluation of Potential Benefit of 6 × 2 Over 6 × 4 Drive Mode to Improve the Fuel Economy on Heavy Commercial Vehicle

Reduction in the drivetrain losses of a vehicle is one of the important contributing factors to amplify the fuel economy of vehicle, particularly in heavy commercial vehicle. The conversion of 6 × 4 drive vehicle into 6 × 2 drive has a benefit of improving the fuel economy of a vehicle by reducing the drivetrain losses occurring in the second rear axle. It was cultured by calculation that in 6 × 2 drive the tractive force available at the wheels, of heavy commercial vehicle with GVW of 44 tons and above, will be much higher than the frictional force transmission capacity of tires, when the engine is producing peak torque on the driving duty cycle like going on steep gradient road. In such situations the tires will start to slip and may result in deteriorating the fuel economy and excessive tire wear. On the other side the flat road driving duty cycle in 6 × 2 drive will give better fuel economy than 6 × 4 drive.
Technical Paper

Methodology for Measurement of Inherent Driveline Frictional Force for a Vehicle in Coasting Mode

Today, with the introduction of Euro-III engines it is possible to achieve almost zero fuel consumption in coasting mode. This means more the distance covered in coasting mode better will be the overall fuel economy of the vehicle. In turn, distance covered by the vehicle in coasting mode depends on the driveline frictional losses i.e. for a particular moving inertia of a vehicle higher the inherent driveline frictional loss lesser will be the distance negotiated by the vehicle. The proposed methodology has been established to determine this inherent frictional force component acting all across the driveline while the vehicle is run in coasting mode under no-load condition. The application of this methodology is limited to vehicles with manual transmission.
Technical Paper

Design of Commercial Vehicle Cooling Packages

Optimization of vehicle engine cooling package with requisite heat rejection capacity plays a key role in achieving most fuel economy and also in meeting the stringent noise norms. A set of design and operating features from existing vehicle engine cooling systems is reviewed and evaluated for their potential to provide optimized engine cooling. The features reviewed states significant potential in engine performance but these are balanced by satisfying required engine cooling requirement. Sets of trials are carried out on said vehicle with dissimilar features of cooling packages and the results are evaluated. Fuel economy trials in performance mode are carried out on vehicle with well thought-out cooling package for healthier comparison.
Technical Paper

Design of Cabin Suspension Characteristics of Heavy Commercial Vehicle

In the commercial vehicle business, Tractor-trailer combination vehicles are mostly used for carrying heavy loads for longer distances. To improve operating economy of the vehicle by reducing turn around time, it becomes a necessity to have a better driving comfort level for the vehicles. In a Tractor-trailer combination vehicle, due to point load acting on the tractor, pitching effect on the cab is very dominant. To overcome this pitching effect, a fully suspended cabin (suspended at four points) has been designed in order to have better ride comfort as compared to the fixed cabin. This paper discusses some of the measures taken to reduce the overall cabin pitching effect on Tractor -trailer combination vehicles.