This case study from Altair ProductDesign explains how the company utilized a simulation driven design approach in the development of a new bus platform, actively looking for every possible opportunity to save weight from the vehicle. A lighter bus takes less energy to move which improves fuel consumption and lowers the operating cost of vehicles that do a huge number of miles over their lifetime.

The Federal Transit Administration (FTA) requires modern transit bus systems to provide more efficient services across America. Currently, U.S. public transit authorities are subsidized to meet operating budgets, with state and local subsidies exceeding $19 billion per year and federal subsidies exceeding $7 billion annually. It became clear that the business challenges faced by owners and operators required an entirely new bus-development process and design.

Comprising senior management, designers, simulation experts and vehicle development engineers, BUSolutions was launched by Altair as an internally sponsored program. The team members sought to apply their deep domain knowledge and a simulation-driven design methodology to fully develop a fuel-efficient, next-generation bus design.

In 2005 Altair partnered with Automation Alley, Michigan’s largest technology business association, to explore government grant opportunities to support the physical build and testing of a technology demonstrator to validate the design. The program attracted the attention of officials from the U.S. Department of Transportation (DOT) and its Federal Transit Administration (FTA). Since 2005, the FTA has provided funding support to Altair, with additional program support from the Michigan Economic Development Corporation (MEDC) and Automation Alley to produce a prototype bus demonstrator.

Simulation-Driven Design
Throughout the development process, vehicle weight was a focus due to its impact on fuel efficiency. When developing the bus, Altair ProductDesign implemented its simulation-driven design process, in which advanced computer-aided engineering (CAE) and simulation technologies are employed at the very start of the design process. Optimization techniques were used to rapidly explore multiple design variations and suggest the ideal layout of structural material. This process gave invaluable insight to the engineers, who used the initial analysis results to form a weight and performance optimized structure very early in the design process.

The core design synthesis tool for the project was OptiStruct, the Altair HyperWorks finite-element-based technology that helps engineers rapidly develop lightweight, structurally efficient designs. Combining Altair ProductDesign’s engineering knowledge with the OptiStruct tool allowed engineers to generate an innovative, lightweight aluminum frame for the bus.

Series Hydraulic Hybrid Technology
To maximize the fuel economy of the bus, an efficient powertrain system was required. After reviewing the potential systems, from pure electric drive to more traditional diesel engines, Altair chose a hydraulic hybrid system, the first of its kind in a bus platform. Unlike electric hybrid technology, the LCO-140H bus (Low Cost of Ownership—1st 40-foot Hybrid) uses hydraulic pressure instead of electricity to propel the vehicle. Through combination hydraulic pump/motor units, it captures braking energy to pressurize fluid, which is then re-used to accelerate the bus. The engine runs only on demand and has periods when it is off and the bus relies solely on the stored hydraulic pressure for propulsion.

Maximizing Miles Per Gallon
Compared to the database of buses tested at Altoona, Penn., where the FTA certification program is run, the LCO-140H was determined to be more than twice as fuel-efficient as the average conventional bus — delivering 110 percent more miles per gallon. Compared to today’s best diesel-electric hybrid bus, the LCO-140H offers 30 percent better mileage and 30 percent lower cost of ownership. This lower cost also comes with higher-level features to meet today’s demands for clean technology and simplified maintenance. These include:

• A design that is 15 percent lighter than other hybrid buses and 10 percent lighter than a conventional diesel bus
• Better cost and performance than diesel and electric hybrid buses
• Industry-leading 41 passenger seats, which are 70 percent lighter than conventional systems

Twice the Fuel Efficiency at a Lower Cost
What started as an internally funded “stretch” project, today has resulted in an industry-first, series hydraulic hybrid bus design that is ready for manufacture. Having successfully completed the testing phase to validate its design and performance metrics, the BUSolutions LCO-140H is the lowest-cost, most fuel-efficient hybrid bus designed to date.

Based on a “clean-sheet” design approach, the extremely lightweight bus design yields more than twice the fuel efficiency of conventional buses and is projected to save $25,000 per year per vehicle for transit authorities using the platform. Requiring no infrastructure upgrades to operate, the LCO-140H is an attractive option for transit authorities to cost-effectively upgrade aging fleets with hybrid vehicle technology.

Find out more about BUSolutions at: altairbusolutions.com