Engineer's Drivetrain Research Advances Automotive Comfort Technology

A Nigerian engineer's innovative research into vehicle drivetrain dynamics has demonstrated how advanced computer modeling can revolutionize the way automotive manufacturers approach driver comfort and vehicle performance.

Engineer Chukwudi Unegbu, who completed his Master of Science in Mechanical Engineering at the University of Bradford, successfully employed cutting-edge simulation tools to predict and analyze problematic vibrations that have long challenged the automotive industry.

Engr. Unegbu's thesis, completed in August 2010, focused on using Modelica and Dymola—sophisticated multi-domain modeling environments—to build comprehensive virtual models of rear-wheel drivetrain systems.

His research specifically targeted "driveability" issues, the subjective quality of how a vehicle responds to driver inputs, how the desired response of the driveline can be achieved by varying the specific parameters and how comfortable that response feels during everyday driving conditions.

The study addressed two persistent problems in automotive engineering known as "shuffle" and "shunt." These low-frequency oscillations occur when drivers suddenly press or release the accelerator pedal during what engineers’ call "tip-in" and "tip-out" maneuvers.

The resulting vibrations manifest as uncomfortable jerking motions that drivers and passengers experience as longitudinal surges through the vehicle, significantly degrading the driving experience and potentially affecting vehicle sales.

Using Dymola's powerful simulation capabilities, Engr. Unegbu constructed detailed virtual models of individual drivetrain components, including the clutch, ideal gearbox, propeller shaft, differential, drive shafts, and wheels.

He then systematically connected these components to create a complete functional drivetrain model that accurately represented the complex mechanical interactions occurring in real vehicles. The model incorporated realistic effects such as aerodynamic drag and rolling resistance to ensure the simulations produced meaningful, applicable results.

The research methodology which represented a departure from conventional approaches to driveability investigation employed a torque step input ranging from 5 to 15 Newton-meters to simulate the sudden torque changes that occur during rapid acceleration or deceleration.

This approach allowed Engr. Unegbu to observe and analyze drivetrain behavior under conditions that typically trigger shuffle and shunt phenomena and key parameter to be adjusted to obtain the desire response. All without the substantial expense and time investment required to build and test physical prototypes.

Historically, automotive manufacturers relied heavily on subjective assessments by experienced test drivers who rated vehicles based on their personal perceptions of comfort and responsiveness. While valuable, the approach lacked the quantitative precision and cost-effectiveness that simulation-based analysis provides.

Engr. Unegbu's work demonstrated that virtual testing could complement subjective assessments, allowing engineers to identify and resolve potential problems during the design phase. The mathematical rigor underlying the study was substantial. Engr. Unegbu derived equations of motion for the rear-wheel drivetrain system, treating it as a series of interconnected masses, springs, and dampers.

The model incorporated realistic physical phenomena including rolling resistance, which he calculated using coefficient values that vary with vehicle speed, and aerodynamic drag, which increases with the square of velocity. These details ensured that simulation results would accurately reflect real-world behavior.

Results from the virtual testing proved highly revealing. The simulations successfully captured the oscillatory behavior characteristic of shuffle and shunt, with graphical outputs clearly showing the periodic vibrations in angular acceleration, velocity, and torque at various points throughout the drivetrain. The longitudinal acceleration response graphs displayed oscillations between 8 and 15 seconds after torque input, followed by gradual decay—precisely the pattern observed in real-world driving scenarios.

Critically, Engr. Unegbu's work confirmed that sudden changes in engine torque serve as the primary excitation source for shuffle characteristics in drivetrains. The simulations demonstrated how torque variations propagate through the drivetrain's compliant elements—the flexible shafts and elastic connections—exciting the system's natural frequencies and producing the unwanted vibrations. The rotational inertia of the engine and flywheel emerged as key influencing factors, validating theoretical predictions with quantitative simulation data.

The thesis also explored the broader implications of drivetrain vibrations beyond driver comfort. Excessive oscillations can accelerate component wear, reducing the service life of expensive parts like transmissions and driveshafts. They can also negatively impact fuel efficiency by introducing parasitic energy losses into the power transmission pathway. Most significantly, severe shuffle or shunt can compromise vehicle control during critical maneuvers, presenting potential safety concerns that extend beyond mere discomfort. The ability to virtually evaluate design alternatives and predict performance before committing to expensive tooling and prototype production offers substantial competitive advantages.

Engr. Unegbu's educational background proved ideal for this multidisciplinary research challenge. His Bachelor of Technology in Industrial Physics from the Federal University of Technology Owerri provided strong foundations in mechanics, thermodynamics, and mathematical modeling. This preparation enabled him to effectively bridge the theoretical aspects of drivetrain dynamics with the practical computational implementation required for successful simulation.

The work's relevance has only increased in the years since completion. As automotive manufacturers face mounting pressure to deliver refined, high-quality vehicles while simultaneously shortening development cycles and controlling costs, simulation-based approaches like Engr. Unegbu's have become increasingly essential especially with the increasing developments in the EV industry. Though the EV and hybrid drivetrains behave very differently from conventional internal combustion systems, simulation allows engineers to model these effects mathematically and refine control strategies until the vehicle responds naturally to driver inputs.

Modern vehicle development has evolved to incorporate even more complex systems, including hybrid powertrains, electric drivetrains, and advanced driver assistance technologies. The modeling frameworks and analytical approaches Unegbu demonstrated in his thesis provide foundational knowledge applicable to these emerging vehicle architectures, where managing vibrations and optimizing driveability remain critical challenges despite the different propulsion technologies. His proposed further work summarily called for collaboration between software developers, mechanical engineers, and test specialists to make drivetrain simulation a shared language rather than a niche skill.

Since completing this research, Engr. Unegbu has built an impressive career in the oil and gas industry, where he currently serves as Principal Subsea and Hardware Delivery Engineer on major deepwater projects. As a Subsea engineer in Shell, he was critical in the award-Winning Engineering and flowless execution of the Bonga Northwest (BNW) field project which was widely recognized as a world-class, pioneering deepwater development by Shell Nigeria. A project named the 2015 Engineering project of the year by the international publication Platts, recognizing its technical excellence, safe and timely delivery.

Since the end of BNW project, he has led many recognized projects within Shell while also providing Subsea solutions across the industry. His work involves leading the designing deepwater Subsea field development projects, Front end engineering designs of Subsea Systems and hardware (FEED), carrying out detailed design of Subsea hardware, managing the fabrication of the Subsea hardware, assembly, testing and installation of complex subsea equipment systems worth hundreds of millions of dollars. The analytical skills, systematic problem-solving approaches, and attention to technical detail developed during his automotive research have translated effectively to these demanding offshore applications.

Engr. Unegbu is also a Chartered Engineer registered with the Institute of Marine Engineers, Science and Technology in the United Kingdom, where he serves as a Council Member. He is currently pursuing doctoral studies in Mechanical Engineering focusing on waste-to-energy conversion technologies. He is specifically investigating kinetic modeling and thermodynamic analysis of catalytic co-pyrolysis reactions.

This ongoing academic engagement demonstrates his sustained commitment to advancing engineering knowledge across multiple domains, from automotive systems to sustainable energy technologies.