Linamar introduces Agilit-e rear axle hybrid power unit for OEMs; FWD Cadillac SRX converted to AWD plug-in hybrid as demo
|The Linamar Agilit-e unit contains the two motors, gears, power electronics, and cooling. The ECU, which is discrete in this first demo application, will be subsequently integrated into the main unit. Click to enlarge.|
Global automotive supplier Linamar Corporation has developed a fully-integrated, compact, modular and scalable twin-motor bolt-on rear axle unit to enable hybrid all-wheel drive applications: the Agilit-e Hybrid Power Unit. The company presented the unit, applied in a conventional front-wheel drive Cadillac SRX now converted to an AWD plug-in hybrid, at the 2013 SAE World Congress in Detroit.
The demonstration unit features twin independent 75 kW motors (150 kW total output), each coupled with a single-speed reduction gear (8.4 ratio), which is bolted to its respective half shaft. Coupled with a 330V, 9 kWh Li-ion battery pack in the SRX, the system enables an all-electric range of up to 30 km (18.6 miles) with a maximum all-electric speed of 130 km/h (81 mph).
The twin motors can be programmed for fully independent active torque vectoring (as opposed to brake-based torque vectoring) with a less than 50 msec response time. The active torque vectoring increases safety and handling by improving front-to-back and side-to-side drivability and optimizes vehicle stability during turns, evasive maneuvers and slippery conditions. (Each OEM customer would tailor the programming to suit their own vehicle “DNA”.)
The Agilit-e unit allows for bolt-on installation between the vehicle’s suspension components. The unit includes the motors, power electronics, gearing and cooling system (liquid). The Agilit-e system is capable of powering the rear wheels in conjunction with the traditional front-wheel drive powertrain, allowing the vehicle to operate in four different drive modes:
Front-wheel drive (FWD) mode powered only by the internal combustion engine (ICE);
Electric only (EV) mode (charge-depleting), which is rear-wheel drive powered only by the battery and the electric motors; and
Hybrid and AWD modes, which allow the ICE and the rear electric motors to work together to provide the desired combination of fuel economy and performance. Full AWD mode is a charge-depleting mode; i.e., the battery powers the rear axle motors and draws down its state of charge to about 60%. At that point, the control unit kicks out of AWD and enters hybrid mode (charge sustaining).(On a subjective note, based on a short drive through downtown Detroit including short stints on the expressways, the SRX in AWD mode delivers a very noticeable improvement in performance and sporty handling. Switching from the hybrid AWD mode to engine-only mode is a definite let-down.)
In a vehicle equipped with the Agilit-e Hybrid Power Unit, the electric mode would typically be used for city driving. Hybrid-electric is best suited for a combination of city and highway driving, with the vehicle powered by the battery and internal combustion engine. The AWD capability is used when handling and performance are needed, for example, during evasive maneuvers or on icy, snow-covered roads. The vehicle’s conventional engine will take control at highway cruising speeds where these engines operate at their peak efficiency.
The scalable Agilit-e can be used on a wide range of front-wheel drive applications from micro hybrid to PHEV/EV.
Linamar’s development target, said Scott Maxwell, Linamar’s Director, Business Development and Marketing and General Manager, McLaren Performance, is to offer OEMs a low-cost, flexible unit to expand their prevalent front-wheel drive lineups with electric drive options. Maxwell said Linamar currently has several programs running with OEMs as they evaluate the unit and see what they might do with it.
There is a massive amount of technology change [in the industry]. Moving from six- to seven- to eight- to nine-speed transmissions, turbocharging, direct injection...so much churn. Our goal is to shorten our customers’ development time and lower their costs.—Scott Maxwell
A great deal of Linamar’s own development effort went into developing the compact packaging, Maxwell noted. The unit will continue to evolve, based on customer feedback. For example, the control unit, which is currently discrete from the main unit, will be integrated back into the main unit, said Maxwell.
Too, the company could replace the single-speed gear (its “Double Planetary”) with a two-speed solution, Maxwell noted.