Audi to integrate powertrain and chassis control

The next step in closer integration of on-board technical systems is almost upon us, according to Audi, with the manufacturer’s Electronic Chassis Platform (ECP) laying the cornerstone of that integration.

Introduced with the Audi Q7 SUV, the ECP can coordinate up to 15 different dynamic subsystems – everything from steering, brakes, g-force sensors and driver inputs to Audi Drive Select, rear-wheel steering, torque vectoring and the car’s quattro sport differential (when fitted).

It’s now about to face a bigger challenge, taking on powertrain operation as well.

The company’s e-tron SUV has already made a move in that direction by linking the ECP to the car’s regenerative braking system, through a system Audi names the ‘integrated brake control system’. This is described by Audi spokesman Ekkehard Kleindienst as “a key component for the efficiency of the Audi e-tron…”

During a pre-production test of the e-tron two years ago at America’s most famous hillclimb, Pikes Peak, the electric SUV completed the downhill ascent with no more than 10 degrees of temperature build-up in the car’s braking system. Audi says that this was due to the integrated brake control system, an energy recovery facility that can provide all the braking effort up to 0.3g – as much as 90 per cent of all braking manoeuvres. In the event that the driver demands braking effort greater than 0.3g, the car’s conventional braking system takes over.

Audi claims that the integrated brake control system can recover about 30 per cent of kinetic energy and convert that energy back to electricity for storage in the car’s lithium-ion battery pack.

The e-tron uses a brake-by-wire system, without any direct mechanical or hydraulic link between the brake pedal and the brake calipers. As the lynchpin for the system, the integrated brake control system assesses the amount of braking effort applied to the pedal and chooses how much braking effort is left to the electric generators and how much – if any – is allocated to the conventional brakes.

Sebastian Kirch, Audi tech expert for brake energy recuperation, says that the driver will not feel any difference in pedal feedback in either mode.

“On the brake pedal, [the driver] always has a constant, reliable brake pedal feel. He doesn’t really notice which of the actuators is being used by the system,” Kirch told Australian journalists, speaking through an interpreter during a live-stream presentation yesterday. There’s no detriment to braking effectiveness, Kirch says. In an emergency, the e-tron’s AEB system will actuate the conventional brakes for a full emergency stop within 150 milliseconds.

In future Audi projects that the ECP will be the ‘coach’ for practically every electronically networked subsystem in the car.

“We will combine the world of the powertrain and the chassis, including the recuperation in one central control unit, which means the ECP will become the central drive unit – or should we say a new drive dynamic control unit – which will combine all the functions regarding the suspension...” said suspension electronics expert Klaus Diepold, also speaking through an interpreter. Diepold revealed that computing power in future interations of the ECP can be expected to increase by “a factor of about 10”, to harness networking of all the car’s on-board systems for applications such as car-to-x autonomous motoring technology, as one example.

The Audi execs wouldn’t specify when this technology would reach market, but development has gone beyond the ‘pilot program’ stage.

Asked whether the advanced powertrain-compatible ECP, which can run with internal-combustion engines as well as electric motors, would be compatible with hub motors in future, Kleindienst answered: “In principle, yes, of course.

“With our electric motors we’re taking a different approach at the moment.”

But Kleindienst indicated that Audi saw no future in that type of powertrain. Another Audi executive, Carsten Jablonowski followed up with his own take.

“The ECP interface is an open one,” he explained through an interpreter. “It doesn’t really matter what actuators I’m using.

“Every system can be adjusted; that’s where the ECP is quite open.”