Cadillac PHEV targeting driving dynamics

Cadillac’s upcoming extended-range electric luxury coupe, the 2014 ELR, the Volt’s upscale cousin, is targeting responsive driving dynamics enabled by advanced suspension and steering systems as well as the smart use of energy.

The technologies include front HiPer Strut suspension, rear compound crank with Watt’s link suspension, a premium ZF electric power steering system and ZF-Sachs continuous damping control.

he 2014 Cadillac ELR's advanced suspension and steering technologies provide the responsive dynamics Click to enlarge.

(The Watt’s Z-link is based on the Watt’s linkage, a device invented by James Watt in 1784 to drive a steam engine piston in a straight up-and-down motion. Automotive engineers have since used Watt’s linkage to prevent sideways motion between the axle and body of a vehicle. General Motors’ exclusive Z-link design is a refinement of that technology, and is applied on a number of vehicles, including the Buick Verano and the Chevrolet Cruze.)

“ELR’s methodical use of advanced suspension and steering technologies front and rear has resulted in the quiet cabin, agile handling and superior ride that Cadillac customers have come to expect. ELR will redefine for many people what the electric car driving experience is all about. Not only does it make smart use of energy, it makes energy-efficient driving fun and luxurious.

—Chris Thomason, ELR vehicle chief engineer

ELR’s Extended-Range Electric Vehicle (EREV) propulsion system delivers 295 lb-ft (400 Nm) of instantly available torque. In driver-selectable Sport mode, the reconfigured accelerator pedal provides quicker torque application and more sensitive feedback through altered suspension and steering settings. ELR also offers Tour, Hold and Mountain driving modes.

With so much torque available, engineers relied on a HiPer Strut front suspension to eliminate torque steer and increase front axle grip while cornering due to optimized tire contact with the road. The HiPer Strut also contributes to ELR’s precise, communicative and linear steering feel, and reduces unwanted steering system disturbances over rough roads and bumps for an overall smoother ride.

In its rear suspension, ELR uses a Watt’s link design to center the car’s rear axle during turns to provide a more balanced driving experience. When cornering, the Watt’s link provides greater lateral stiffness that results in more positive vehicle response to steering inputs and helps keep the rear suspension aligned with the front suspension. When the ELR is traveling on a straightaway, the Watt’s link allows the suspension to travel up and down freely to make the ride more comfortable.

ELR’s premium electric power steering system is designed to provide excellent feedback while saving fuel. The rack-mounted, dual-pinion system—one for steering and one for power assist—consumes energy only when the vehicle is actively steered. A combined electric motor and sensing unit monitors steering angle and delivers appropriate assist to the steering gear at all times, correcting for crowned road surfaces and cross-winds. This helps reduce driver fatigue.

In driver-selectable Sport mode, ELR’s steering gear provides increased on-center sharpness and steering sensitivity for dynamic steering. In the more relaxed Tour mode, it allows precise control with less driver steering efforts.

ELR’s continuous damping control monitors sensors throughout the vehicle, vehicle speed and the driver’s input, and adjusts damping accordingly for each 20-inch wheel every two milliseconds to maintain optimal vehicle ride control over varying road surfaces and profiles. This reduces and controls vehicle roll, pitch and vertical motions for a flat “sky-hook” ride performance, and instantly responds to cornering maneuvers by automatically adjusting the dampers to a firmer level for superior handling and stability. When driving on smooth roads, the dampers are automatically adjusted to the softest setting to provide increased isolation and ride comfort.

An isolated four-mount front cradle contributes to the ELR’s overall quietness, noise and vibration performance, and ride-and-handling dynamics. Specifically tuned mounts are tailored to the engine’s inherent torque axis, decreasing the transfer of vibration and noise into the cabin.

Now in its final months of pre-launch engineering testing, the ELR is slated to reach showrooms in the US by early 2014. The EREV propulsion technology provides full driving range exceeding 300 miles (480 km), combining pure electric driving and an efficient, range-extending generator.

Source: Green Car Comgress