The International Centre for Automotive Technology (ICAT) recently organised the fifth edition of its International Seminar on Noise, Vibration and Harshness (iNVH) at its Manesar facility. Realising the challenges before automotive OEMs, ICAT undertook an initiative in 2011 to create a platform for NVH experts, academia and industry engineers, to come together and share global trends, challenges, solutions, knowledge and experiences for the future benefit of improving NVH on vehicles.
The 5th iNVH workshop-cum-seminar strived to reinforce this platform for deliberation among the industry and domain experts, in their bid to develop superior solutions for quieter vehicles. After the overwhelming response of the last four workshops, the 2019 iNVH workshop-cum-seminar provided a highly interactive experience to the participants through keynote presentations and a panel discussion by leading industry experts on the various domains of NVH. Presentations by keynote speakers at iNVH 2019 focussed on the current trends and future projections of the NVH technology for the Indian and global markets. Further, the speakers also deliberated on systems & component development, testing & infrastructure requirements as well as simulation technologies for NVH optimisation. The iNVH 2019 workshop offered delegates an excellent platform to interact & discuss the advancements of the NVH technology, problem-solving strategies and real life case history on NVH, while offering a global perspective. Delegates at the iNVH 2019 workshop-cum-seminar witnessed ten technical lectures by highly competent thought leaders, live lab demonstrations at ICAT Centre 2 and a panel discussion comprising eminent industry leaders.
INCREASING NVH CHALLENGES FOR ELECTRIC VEHICLES
With vehicle buyers becoming more discerning and mature, the ever-increasing expectations of quieter vehicles are growing. A single quiet vehicle becomes a benchmark for others to follow in the future. Thus, customer expectations are continuously on the rise, posing huge challenges for NVH engineers. Experts in the NVH domain have highlighted the issues and challenges faced in the backdrop of e-mobility that is an emerging trend in the mobility space.
Contrary to the common belief and expectations that the challenge of NVH with EVs may decrease, Dinesh Tyagi, Director ICAT and Chairman of the Organising committee, iNVH 2019, stated this challenge will only increase going forward. He reasoned that the absence of a conventional ICE that emanates ambient white noise and added that wind, road and suspension noises will be highlighted, causing customer discomfort. Tyagi proposed a solution of artificial sound to provide a soothing ambience within the vehicle, as it would camouflage exterior noises.
Further, considering EVs are relatively silent, there is also a need for artificial sound to alert road users of an approaching vehicle. Pravin Agrawal, Joint Secretary, Department of Heavy Industries, Government of India, opined that road users do not want to buy electric vehicles, as they do not have any noise, as this leads to confusion over the vehicle’s ignition status. He was of the opinion that it may further lead to a mishap. Agrawal highlighted deliberations at the United Nations Economic Commission for Europe’s (UNECE) WP.29 forum regarding the introduction of artificial sound in EVs, to alert other road users of a moving vehicle. Sharing perspectives on the subject, Sudeshna Sen, Director Finance, NATRiP, highlighted the plight of a visually challenged citizens, who rely on sound to find their bearings and added that there is a need to introduce artificial sound in vehicles.
Dr Manivasagam Shanmugam, Global COE Head – Vehicle Engineering, Tata Technologies, spoke of the strong disruption taking place across the automotive industry, with the electric vehicle technology gradually emerging as the future vehicle technology. It has been predicted that roughly half of the global passenger car population will be from the electric vehicle segment by 2035. Despite NVH control of the passenger vehicle industry reaching significant maturity, the emerging technology shift towards electric vehicles will pose new challenges for NVH engineers, as the prime source of noise, the IC engine, is not making noise generated by auxiliary systems like fans and pumps. Although the noise generated by the motor is normally less in decibels, the pure tone signal content will be quite annoying for the passengers.
EVOLUTION OF NVH ENGINEERING & CURRENT OPTIMISATION TRENDS
Two decades ago, OEMs were focussing on aspects such as energy, drive performance, etc. NVH was earlier defined in the form of basic body vibrations. From the late nineties to early 2000 the prediction maturity has increased. Vehicle manufacturers have started using NVH to differentiate their products in an increasingly competitive marketplace. Today, the typical targets in 2019 for bending frequency should be above 35 Hz. It is not easy to achieve these targets, especially coming from a stage where these were not being looked into at all. Dr Shanmugam also stated that NVH and durability predictions have come a long way. Further, he established that flow-induced noise prediction has reached a certain level of maturity, as it was never considered a part of development parameters - it is now gradually being introduced as a development parameter.
New trends like electrification, engine downsizing, autonomous mobility, etc are also expected to affect classical NVH engineering. Noise and vibration of the classical combustion engine will not play a dominant role any further; rather other mechanisms such as magnetic induction, road excitation, gear whine, HVAC or aerodynamics will now be the focus of NVH engineers. Taking the subject further, Wim Hendrix, Business Development & Technical Supervisor, Simcenter Engineering Consulting Services stated that modelling holds the key to streamlining NVH integration in the vehicle development process. Testing also remains an important aspect and while the trend is more towards simulation, testing remains crucial for evaluation and benchmarking, he stated.
Among the many sources for noise in a vehicle, tyre–road interaction noise is one the most critical noise sources of a vehicle, when at high speeds. For electric vehicles, with the engine removed, the tyre-road interaction noise is more dominant. Current legislation and customer awareness dictate stringent exterior noise performance targets for tyres. Here, the accommodation of low noise demands without affecting other performance requirements of tyres is a real challenge for a tyre NVH engineer. Typically, tyre–road interaction noise generation mechanisms are divided into two main categories – vibrational mechanisms (below 1,000 Hz) and aerodynamic mechanisms (above 1,000 Hz). Reiterating the challenges before tyre NVH engineers, Dr Jaiganesh Subbian, Senior Scientist – Advance Engineering, Apollo Tyres Ltd, said in today’s scenario low rolling resistance is required to control CO2 emissions and improve mileage. The tradeoff is on wet grip to achieve low rolling resistance. Further, for lower rolling resistance, weight reduction exercises need to be done. With weight reduction, vibrations will increase. With low rolling resistance, vehicle handling is also compromised. An aggressive tread design can offset the compromise, but would generate more noise. He concluded that performances are conflicting and at present engineers need to balance these.
Buzz, squeak and rattle (BSR) are other noises associated with NVH engineering of vehicles. Human perception of quality is closely attributed to BSR and the perceived quality has a high impact on brand perception of vehicles. Speaking about the BSR challenges and solutions, Riyazuddin Mohammed, Lead Engineer – BSR & Door Slam Development (NVH), Product Development – Automotive Division, Mahindra Research Valley, stated that with significant improvements in NVH, the masking of BSR is slowly diminishing and customers are easily able to identify these, leading to a perception of poor quality. He spoke about the zero gap design challenge, using simulation, wherein Mahindra engineers were able to identify relative displacements of gaps and used a preloading strategy, with topology optimisation to control both rattle and squeak. He also highlighted the use of planned quality BSR with end-of-line testing to thoroughly iron out BSR issues.
The two-day event was attended by around 220 delegates from different sections of the automotive industry. The various sessions that were conducted during the two-day event focussed on multiple research & development activities, industry practices, testing methodologies and standards. The panel discussion on “NVH challenges faced by the automotive Industry” also deliberated on various plausible solutions to challenges faced by NVH engineers. The participants discussed the basics of the NVH technology, problem-solving strategies on NVH to obtain a global perspective on the relevant trends in the NVH domain.
The event witnessed speakers from leading research & development Institutes such as Mahindra Research Valley, Tata Technologies Ltd, Mahindra Truck and Buses, Siemens PLM Software, 3M India, Comstar Auto, Adams Technologies, Apollo Tyres, Mahindra Tractors, etc. Delegates shared their knowledge on various issues critical to automotive NVH like current challenges & future trends, buzz, squeak and rattle - development challenges for Indian OEMs, tractor NVH, tyre & road interaction noise, motor noise and the importance of NVH software in the Indian automotive industry.
TEXT: Joshua David Luther