Global Hybrid Cooperation, formerly Advanced Hybrid System 2 (AHS2), is a set of hybrid vehicle technologies jointly developed by General Motors, Daimler, and Chrysler LLC, with BMW joining in 2005. It uses 2 or 3 planetary gearsets in an automatic transmission: one on the internal combustion engine (ICE) side (input split) paired with a second (output split), forming the compound split, and possibly one third additional planetary gearset to multiply the number of fixed gear ratios (up to 4). General Motors has stopped using the "AHS2" name as of 2006, preferring to call it simply a two-mode hybrid system.
This technology was named as "Technology of the Year" for 2007 by Automobile magazine.
While Toyota's Hybrid Synergy Drive may appear similar in that it also combines the power from an ICE and a pair of electric motor–generators; however in its current form, Toyota uses only one planetary gearset providing only single mode functionality (i.e. input split only) using a series/parallel architecture. While, Honda's Integrated Motor Assist uses a traditional ICE and transmission where the flywheel is replaced with an electric motor: it is a simple parallel architecture, requiring the addition of a mechanical continuously variable transmission (CVT), i.e. not electrically variable.
Cooperation
The GM/DaimlerChrysler partnership was announced on December 13, 2004, with Dieter Zetsche of DaimlerChrysler joining Rick Wagoner of GM on stage with a prototype. The agreement was not signed until the following August, however.
GM was reportedly responsible for development of rear- and four-wheel drive truck and front wheel drive car systems while DaimlerChrysler was focused on a rear wheel drive luxury car application.
It was announced on September 7, 2005, that BMW would also join the alliance, likely using then-archrival DaimlerChrysler's rear wheel drive system.
The three companies formed an organization called Global Hybrid Cooperation with engineering and management centered at the GM, DaimlerChrysler and BMW Hybrid Development Center in Troy, Michigan. Recent reports indicate that the three automakers will spend one billion US dollars between them on the development of the front- and rear-wheel drive hybrid transmissions.
On March 1, 2007, BMW and DaimlerChrysler announced that they were expanding their partnership and moving quickly to develop a mild hybrid module for rear wheel drive premium cars. They planned to roll out the new system within the next three years on BMW and Mercedes-Benz vehicles produced. In 2009 Mercedes released the S400 hybrid using a lithium ion battery.
GM is not part of this expanded partnership, and has not announced plans to develop a hybrid RWD system for cars.
It was reported in July 2009, however, that after the upcoming introductions of two-mode versions of the BMW X6 globally and the Mercedes-Benz M class only in the United States, the joint venture would be dissolved. Daimler indicated that it wants to avoid investing in aftersales and service for a vehicle which will only be produced in small quantities, and will instead concentrate on modular hybrid building blocks with scalable lithium-ion batteries, based on the hybrid drive developed for the S-class and 7 Series sedans in another joint venture with BMW and auto supplier Continental AG.
Technology
The technology is referred to as "two-mode" hybrid transmission due to the ability to extend the abilities of both electrical and mechanical paths of power. The two modes of operation are: