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Driving dynamics performance is one of the key customer attributes to be developed during product development. In the vehicle development process, freezing the hardware of the chassis aggregates is one of the major priorities to kick off the other vehicle development activities. The current work involves the development of a multilink suspension for an SUV class vehicle. Typically, each OEM performs several product development loops for maturing the vehicle design. The driving dynamics performance evaluation and tuning happens on a physical vehicle with the driver in Loop. Tuning of suspension parameter on the physical vehicle entails actual replacement of parts/components. This encompasses multiple tuning cycles in product development associated with increased cost and test time. To reduce the product development time and cost while delivering first time right chassis configuration, we took an approach of getting driver-in-loop through driving simulator in the concept phase.

Potholes are a major cause of discomfort for riders and vehicle damage. The passive suspension systems which are used in the passenger vehicles are primarily reaction based. These can’t adapt to the changing road conditions which means the best ride quality and handling characteristics cannot be ensured for different driving situations. Passive suspension system also needs more maintenance due to its inability to reduce the impact of the road irregularities. In recent years, semi-active suspension systems have been developed to improve ride comfort and vehicle safety. This paper covers the integration of a semi-active suspension system with a road preview mechanism with a TATA car model to investigate its impact on ride comfort, handling characteristics and component loads in digital domain. A quarter car vehicle model is used to compare different active damping control strategies.

In current competitive automobile sector, gear shift quality has become significant factor for vehicle evaluation. OEMs are sensibly focusing on improving gear shift quality to meet customer’s expectations. Though there are different gear shifting habits in different drivers, diagonal shifting is the fastest way of shifting gears in manual transmission vehicle. So the components linked with shift system should be designed to facilitate smooth diagonal gear shift pattern. This paper enlightens the process of defining chamfers on internal gear shifting components for smooth diagonal shifting movement of gear shift lever. It is hard to define chamfers by analytical or practical approach. Creo-mechanism is very useful simulation tool which can be used to understand diagonal shift patterns and to define the chamfers.

Twist-beam suspensions are an example of design solution presenting acceptable performance when applied to passenger cars & light vehicles and it can provide an optimal between cost & performance in the automotive market. For these reasons, twist beam is quite popular in use in rear suspension of light vehicles. In contrary to other types of suspension, the twist-beam has a flexible torsion beam connecting the swing arms. The study of the deformation of this flexible element becomes important to understand its performance and durability behavior. As the name signifies, twist beam major performance attribute is control of twist or opposite wheel travel arising from vehicle roll or road input. Current approach for the study this deformation is through FEA & Multi-body dynamics software tools.

Lift axles of heavy commercial vehicles are deployed to handle increased payload. These axles of Commercial vehicles are made of low alloy carbon steel materials. Lift axles are designed in hollow condition for weight reduction opportunity. Two types of tube materials are used for the manufacturing of lift axles. These are either Cold Drawn Seamless (CDS) tubes or Hot Finished Seamless (HFS) tube material. The vanadium micro-alloyed steel grade, 20MnV6 is an excellent choice for the manufacturing of lift axles. The 20MnV6 has favorable mechanical properties for lift axles and also offers good weldability. However, lift axles made of 20MnV6 when manufactured in hot-finished condition, shows significant scatter in terms of durability performance. This requires further heat treatment of 20MnV6 to be deployed for reducing the scatter in the material properties to reduce scatter in durability performance and thus increasing the reliability of the lift axles.

This paper takes a review of fretting phenomenon on splines of the engaging gears and corresponding splines on shaft of automotive transmission and how it leads to failure of other components in the gearbox. Fretting is a special wear process which occurs at the contact area of two mating metal surfaces when subject to minute relative oscillating motion under vibration. In automotive gearbox, which is subjected to torsional vibrations of the powertrain, the splines of engaging gears and corresponding shaft may experience fretting, especially when the subject gear pair is not engaged. The wear debris formed under fretting process when oxidizes becomes very hard and more abrasive than base metal. These oxidized wear particles when comes in mesh contact with nearby components like bearings, gears etc. may damage these parts during operation and eventually lead to failure.

This paper discusses the test setup and methodology required to validate complete lift axle assembly for simulating the real time test track data. The correlation of rig vs track is discussed. The approach for reduction of validation time by eliminating few of the non-damaging tracks/events, its correlation with real life condition is discussed, and details are presented. With increased competition, vehicle development time has reduced drastically in recent past. Bench test procedure using accelerated test cycle discussed in this paper will help to reduce development time and cost. Process briefed in this paper can also be used for similar test specification for other structural parts or complete suspension system of heavy commercial vehicles.

With the advent of BS VI regulations, automotive manufacturers are required to innovate the powertrains, fuel systems, exhaust and its after treatment systems to meet the regulatory requirements. The exhaust regulations can be met either by reducing the exhaust gases being generated by the engine (attacking the source) or by treating the exhaust gases in after treatment devices. The choice of the opted system varies with the manufacturer. The after-treatment devices such as catalytic converters are generally mounted in the engine compartment to take advantage of high temperature of exhaust gases to yield the reactions. Such an arrangement imposes a lot of thermal load on the peripheral components such as gearshift cables, bearings, oil seals, driveshafts etc. Thermal shields or thermal sleeve are used to address thermal issue and to protect transmission components.

For a modified electric vehicle on the same internal combustion engine (ICE) platform, the primary consideration is to have no change in long member and pendulum type conventional engine mounting system to save development cost and timeline. Electric vehicle (EV) powertrain is comparatively lighter w.r.t the ICE. As a result, the engine mount’s static preload setting point or powertrain centre of gravity under static powertrain load gets changed resulting in a change in stiffness for the same engine mount. As the static stiffness changes, the dynamic stiffness and modal frequency also change. The 6 degrees of freedom (DOF) modal frequency has almost no impact on powertrain modes as EV powertrain modes, mainly, the motor frequency, is much higher than engine mount Eigen modes. In this scenario, the gap management gets disturbed due to less static preload, and non-linearity gets affected.

In modern automotive vehicles, there is a major concern for noise and vibrations generating from drivetrain. These noise and vibrations affect the passenger comfort and drivetrain parts life. Engine generates fluctuating torque and causes angular acceleration that results into torsional vibrations. These vibrations are transmitted to powertrain. Clutch disc consists damper springs and hysteresis which aids reducing these torsional vibrations. Based on the damper spring stiffness, one can control the resonance speed range and shift the resonance rpm out of driving speed range of engine. The resonance should not happen within driving speed range of vehicle to avoid large amplitude torsional vibration. But here limitation is put on the torque transmission capability of clutch for meeting vehicle requirements. As, low stiffness of damper spring requires large wind-up angle so, it is critical to decide its stiffness.

Exhaust Noise attenuation is one of the important functions of exhaust muffler. Transmission Loss (TL) is a measure of noise attenuation used in designing exhaust mufflers for NVH. TL is a logarithmic difference between inlet and outlet pressures for unit velocity input at inlet of the muffler and anechoic termination at outlet of the muffler as boundary conditions. TL amplitude and its frequency tuning depends on a combination of various muffler design parameters like volume, length, muffler cross section, pipe cross sections, pipe perforations, number of chambers, baffle perforations, etc. Achieving the desired TL performance with no valleys over a wide frequency range is very challenging. Manual design iterations with large numbers of permutations and combinations of design variables are difficult and time-consuming. It also needs a highly experienced professional to balance TL performance, design variables and design constraints.

Passenger utility vehicles like car, SUVs, MPVs are used in wide application all over the world. Luxuries are becoming essential features of product mix along with comfort and ergonomics. Customer desires best shift quality with emerging technologies like AT, DCT, CVT, etc. and every OEM is working hard to achieve it. It is very difficult to satisfy the customer desire because of diversities in demographics and geographic. Gear shift quality (GSQ) is very crucial touch point in overall drive feel of vehicle. It consist of various parameters like mode selection feel, precision, comfort, select Noise, etc. It demands tradeoff practices among various parameters as stated. In this paper, external mode selection system of automatic transmission is explained. Various contributing parameters are explained with practical design approach for detent profile, mode selection mechanism, cable & dampers, etc.

Gear rattle is due to impact noise of unloaded gears in transmission having freedom to move in backlash region. Engine order vibrations in the presence of backlash in meshing pairs induce the problem. It is a system behavior wherein flywheel torsional vibrations, the pre-damper characteristics and transmission drag torque plays a vital role in an engine idle condition (hot & cold). Idle rattle is a severe issue, which is highly noticeable in cold condition or after 1st engine crank. Gear rattling observed in idle condition is idle gear rattle or neutral gear rattle, specifically in cold condition is a “Cold idle rattle” and this is one of the critical noise parameters considered for entire vehicle NVH. Damper mechanism in the clutch, is used to serve better isolation (by reducing the input excitation to transmission parts) of vibrations between engine and transmission their by reducing gear rattle intensity.

Gearbox and driveline durability is always been a sensitive subject from both end user and manufacturer’s point of view. Since powertrain is heart of vehicle, naturally it is expected to long last and perform satisfactorily for the entire vehicle life. Sometimes the driveline aggregates especially gearbox might face some issues because of various factors, but this is distinctively noted by the driver since it is one of the important touch point of the vehicle. The gear slippage is a very typical phenomenon observed in automotive gearbox. The issue of gear slippage is very sensitive because it leads to compromising safety of the driver, also it deteriorates gear shift quality and thereby performance of the vehicle. Generally, gear slippage is not observed during end of line testing or during early kilometers of vehicle. It is observed after some thousand kilometers, that to initially gear slippage is not observed consistently and that’s why it is difficult to identify at early stage.

Normal engine mounting system is designed to carry loads of powertrain in all driving conditions and also isolate the vibrations of powertrain. Softer mounts are good for vibration isolation but it is not recommended to have softer mounts because durability will be affected adversely. Optimum stiffness needs to be finalized which will have balance between durability and performance. In addition to durability many performance parameters needs to be checked during the time of development. This study includes the development of engine mounting system for elimination of drive away judder in first gear. Maximum peak torque value for the drive-away event is in the range of 80Nm - 120Nm. In the worst case, this peak torque can reach to maximum 170Nm depending on maneuver, engine rpm is around 1100-1200. Steering wheel, instrument panel and whole vehicle cabin will vibrate for few seconds and then vehicle will run smoothly.

The recent vehicle development demands for electric powertrain as against conventional fuels engines. The electric powertrain offers advantages in terms of cleaner and quieter operations. In electric vehicle, the conventional engine is replaced by electric motor operated on batteries. Here, the conventional engine refers to those powered by diesel, petrol, CNG and some hybrid vehicles using fuel as primary source for power generation. Thus, the system design approach for mount also changes. At present, various approaches are being followed to mount electric powertrain like conventional pendulum type, with or without cradle, Common or different motor and electric box mountings etc. The electric powertrain differs from conventional powertrain in terms of weights, mass moment of inertia, torque, NVH requirements like Key in Key off, idling, low frequency vibrations etc. Thus conventional mount will not necessarily meet NVH requirements for Electric powertrains.

The clutch is the connecting link between engine and the power train. It connects and disconnects the engine to the gearbox as per the wish of the driver. Clutch has a friction disc which acts like a fuse wire which wears in the process of the connection. This paper tries to calculate the clutch life analytically (In terms of Kms. run by vehicle), of automotive vehicles having manual transmission. As the clutch engages and disengages the engine to the gearbox, during this time due to slippage, energy is dissipated which results in the wear of the clutch disc. It calculates life based on the volumetric wear of the clutch disc and wear allowance available. The work done by other people in this domain include the empirical estimation of clutch life based on the past data, effect of the surface topography on the friction characteristics of the wet clutches, modeling of clutch housing and facing temperature for the estimation of the clutch life of a manual transmission etc.

As we are moving towards complete electrification from combustion engine to electric motor, the system design approach also changes due to application. For a range of 100-150 kg EV powertrain weight, number of mounts as well as mount locations, orientations and stiffnesses plays a significant role during system design. The electric powertrains are usually lighter and their mounts are usually stiffer than the mounts for typical combustion engines, the static displacements at dead load are usually lower. However, currently it seems like there is no common direction of all OEM’s regarding the question of how stiff an e-motor mounting system should actually be. Due to the high torque of the EV’s one could even think about switching to a four point mounting instead of a pendulum mounting.

Regular vehicle has the advantage of Engine resistance even when it is not fired, hence chances of vehicle roll back on gradients will be minimized. This is not the case for Electric vehicles, which uses an electric motor that does not have any resistance offered to wheels that prevent vehicle roll back on gradient. This leads to increased load on the conventional hydraulic brakes due to absence of engine inertia. Hence, there is a need for a low cost and reliable automatic braking system which can help in holding the vehicle and assists the driver during launch in case he need to stop at a gradient. An Electromagnetic brake (EM brake) system can be used as a solution for the above-mentioned requirement. EM brake can provide hill hold and hill assist effect in addition to automatic parking brake application when the vehicle is turned-off. This system will assist anyone who need to halt the vehicle at a gradient and then relaunch it without much struggle.

In the recent years steering feel characteristics have emerged as one of the important brand image attributes of automotive OEMs. Since past few decades, the hydraulic assisted steering system (HPAS) on which lot of research was done to tune the steering feel has been taken over by electric power assisted steering (EPAS) system. The EPAS primarily uses an electric motor controlled by an electronic control unit to assist the driver in maneuvering the vehicle. The next big leap in the steering system advancement is steer-by-wire (SbW) technology where the mechanical linkage between the steering wheel and the road wheels is eliminated. The advantages of this system are ease to use, elimination of noise-vibration-harshness of steering system caused by road forces, modularly of steering system for packaging, improved visibility to front-end displays and road ahead and a fun to drive concept.