GM PARALLEL HYBRID
TRUCK PROGRAMME CASE STUDY
A FORE-RUNNER TO FUTURE VEHICLE PLATFORMS
Zytek were approached by GM to assist with the creation of a new concept of vehicle, hybridised but with new operating modes and power outlets to be able to offer both a fuel efficiency saving in day-to-day use, but also to act as a portable generator with 3 phase outputs in both the cabin and the truck bed for use in construction sites etc.
The truck was scheduled to be a pioneer, one of the first hybrid vehicles to be launched to the market, and the first with such a complex mix of fuel saving potential and electrical capabilities.
Following an initial study to investigate a variety of electrical topologies, a concept was agreed and work commenced using teams located in both the USA and the UK.
The 48V system required a number of new innovations to be brought to market, including
- Electric steering system
- Electric braking system
- New integrated electric machine encasing
- Downsized torque converter
- Hybrid control module
Plus integrated electronics with 3 phase outputs for both the electric machine and the 120V outlets, sited in the cabin and in the rear of the truck.
Zytek’s role included project management and the coordination of multiple suppliers to end up with a vehicle that could demonstrate fuel savings compared with the base truck.
In addition, a new clean sheet of paper hybrid control module was created designed to arbitrate the hybrid system to deliver functionality within a tightly-constrained safety system.
Significant test efforts were necessary due to the unique test requirements associated with a hybrid vehicle, including ensuring:
- A representative CO2 emissions performance when tested in chamber
- That emission-related diagnostics could be completed (as the engine was deliberately operated to avoid high manifold vacuum, low efficiency areas)
- Driveability metrics could be maintained, including speed of engine restart, towing performance, cabin comfort when the engine was not used at low speed and at rest etc
After a development period of 4 years, the Zytek team delivered a vehicle that met all of the customer requirements, and assisted with the product launch into market where it served as a fore-runner to future vehicle platforms where ever-increasing levels of electrification were introduced.