Reinventing Electric Bus Design Through Lightweight Engineering
With the global shift toward greener transport, the automotive industry is under growing pressure to reduce energy consumption while improving performance. Nowhere is this challenge more pressing than in the design of new-energy vehicles, where every kilogram saved translates to measurable gains in efficiency and range.
Electric buses represent a particularly demanding case due to their large, heavy structures, which account for a significant share of total vehicle mass, directly influencing battery load and energy use. To tackle this, engineers are turning to advanced lightweight design strategies that balance performance, safety, and structural integrity.
A research team from the National Engineering Research Center for Electric Vehicles at Beijing Institute of Technology, working in collaboration with the Northwest Institute of Mechanical and Electrical Engineering, has developed a sophisticated new framework to address this problem. Their study, Lightweight Design of an Electric Bus Body Structure with Analytical Target Cascading, proposes an innovative approach to optimising the body structure of electric buses through analytical target cascading (ATC).
The Analytical Target Cascading (ATC) Approach
At the heart of this study lies the ATC method, a hierarchical optimisation technique designed to improve system-level performance by coordinating goals across multiple subsystem levels. Unlike traditional optimisation approaches that treat a vehicle structure as a single unit, ATC allows engineers to decompose complex problems into manageable layers, ensuring that local design improvements contribute to global objectives.
In this research, the lightweight design problem was divided into two major levels: a system-level model and three subsystem-level models, covering the side structure, roof structure, and chassis. The system-level optimisation sought to minimise total mass while maintaining essential modal frequencies for structural stiffness and vibration resistance. Meanwhile, each subsystem-level model focused on improving local performance metrics while keeping mass reductions within specified limits.
To align the two levels, the team reformulated subsystem objectives into penalty-based functions. These functions ensured that subsystem goals did not conflict with system-level targets but rather reinforced them through iterative coordination.
Structural Validation Through Advanced Simulation
Optimisation alone does not guarantee safety or real-world viability, so the research incorporated rigorous validation techniques. The team constructed a detailed finite element model (FEM) of the bus body and verified its accuracy using experimental modal tests. The simulations captured dynamic responses under a variety of operational conditions, allowing the researchers to fine-tune the model before implementing the ATC strategy.
To solve the optimisation problem, they employed a sequential quadratic programming (SQP) algorithm, a reliable method for achieving convergence in nonlinear problems with multiple constraints. This choice ensured efficient coordination between the system and subsystems without compromising accuracy.
Significant Weight Reduction and Enhanced Structural Performance
The outcome of the research was impressive. The optimised electric bus body achieved a total mass reduction of 49 kg compared with the original design, while simultaneously improving torsional stiffness by 17.5%. This gain in stiffness enhances the vehicle’s ability to resist twisting forces during cornering and uneven road conditions, contributing to improved ride quality and safety.
Further validation came through strength analysis under both bending and torsional load cases. The findings confirmed that all critical stress levels remained below the yield stresses of their respective materials, ensuring that the redesigned structure met all strength and durability requirements.
Multi-Material Design and its Advantages
One of the standout aspects of this study was its use of a multi-material approach. By carefully integrating materials with different mechanical properties and densities, the engineers could strategically position strength where needed and reduce weight where possible. This method aligns with modern trends in vehicle design, where hybrid material architectures, such as combining high-strength steel with aluminium and composites, deliver optimal performance-to-weight ratios.
Such material efficiency doesn’t just reduce energy consumption; it also lowers the total cost of ownership by extending component life and improving overall efficiency. In electric buses, even modest reductions in body weight can lead to substantial gains in range and battery lifespan.
Implications for Future Electric Vehicle Manufacturing
The implications of this research extend beyond the bus sector. The ATC method can be applied to other categories of electric vehicles, including trucks, vans, and passenger cars. As EV manufacturers race to improve efficiency without compromising safety or comfort, structured optimisation frameworks like ATC will play an increasingly vital role in product development.
Moreover, by integrating ATC into early design phases, manufacturers can reduce prototype testing costs and shorten development cycles. The combination of computational simulation, hierarchical modelling, and data-driven validation provides a pathway to more predictive and efficient engineering.
Bridging the Gap Between Theory and Practice
While analytical optimisation methods have existed for years, their practical application in large-scale vehicle design has often been limited by computational demands and complexity. This study demonstrates how modern algorithms and high-performance computing can bridge that gap, allowing design teams to coordinate dozens of interdependent variables effectively.
By decomposing the problem hierarchically, engineers can maintain clear control over individual components while ensuring that subsystem refinements contribute meaningfully to the overall vehicle objectives. This harmonised design philosophy could soon become standard practice in next-generation electric mobility solutions.
Industry Perspective and Global Context
Across the global transport sector, the pursuit of lightweight solutions is accelerating. European bus manufacturers like Solaris and Volvo have already adopted lightweight aluminium architectures, while Chinese leaders such as BYD and Yutong are investing heavily in carbon fibre-reinforced panels and modular chassis systems. The study by Beijing Institute of Technology and the Northwest Institute of Mechanical and Electrical Engineering positions China firmly within this global trend, pushing for innovation that combines material science, computational optimisation, and vehicle dynamics.
International research collaborations are likely to expand this approach further. Integrating ATC methods with digital twin technology, for example, could allow continuous real-time optimisation during production and operation, further improving efficiency and safety.
A Step Forward in Sustainable Transport
The success of this project underscores how methodical, data-driven engineering can yield measurable benefits for sustainable mobility. As cities strive to decarbonise public transport networks, electric buses designed through intelligent optimisation frameworks will play a central role in achieving these goals.
In a field where every gram and kilowatt counts, this research represents not just an academic achievement, but a practical milestone in the evolution of electric mobility.
