Calibration and the Ford Fusion Hybrid

Control and calibration engineers are the unsung heroes of vehicle development. Their role is to create, tune, and set the complex digital algorithms that control the engine, transmission, and other key vehicle systems, and to make those systems continually “talk” to each other in milliseconds.

When the control and calibration engineers excel in their tasks, as Ford’s team clearly did in developing the 2010 Fusion Hybrid, the resulting vehicles are seamless in operation. As perceived by the driver, they function as an integrated piece rather than a collection of separate parts.

This critical work requires a special focus and commitment. It consumes thousands of hours. As the production deadline looms, much of the engineers’ time is spent “in the saddle”-glued to laptop screens, poring over data, tapping in new code and making adjustments on the fly during long drives in the vehicle.

The payoff is a new car or truck that meets or exceeds the customer’s performance and drivability expectations, while also complying with increasingly tough fuel economy and emissions targets.

For conventional vehicles, the controls and calibration task is considerable. For hybrid-electric vehicles, it’s enormous.

“Calibration on any vehicle program is all about managing tradeoffs,” explains Rob Iorio, calibration engineering manager on the Fusion Hybrid program. “You have the ‘musts’ of meeting various regulatory mandates — tailpipe and evaporative emissions, and onboard diagnostics. And you have your ‘wants’ of efficiency, performance, and reducing NVH (noise, vibration, and harshness). The ‘musts’ and the ‘wants’ often are very challenging to reconcile.”

A hybrid-electric powertrain adds significant new dimensions to the trade-offs engineers must deal with, Iorio notes.

“Hybrids are all about battery management, which includes getting the most out of regenerative braking performance,” he says. “You’re striving for second-by-second efficiencies. Every tweak and adjustment made for the purpose of improving one area — stop-start smoothness, for example—is magnified, often to the detriment of another area.”

The best hybrid vehicles are far greater than the sum of their major subsystems such as batteries, electric motors, and power control units, observed Dave Hermance in 2003. Toyota’s Prius set the pace in this area during the ‘first’ hybrid decade, 1999-2009.

Hermance believed that increasingly precise calibration would be what separates the best hybrids from the rest. He believed it also would help define and distinguish vehicle brands.

By that measurement, the 2010 Fusion Hybrid earns the inaugural Hermance Award, setting a new industry benchmark in overall hybrid-powertrain functionality and refinement.

The Hermance Award panel believes Ford’s engineers did a remarkable job in smoothing the transitions from combustion engine to electric drive, including stop/start, acceleration, and cruising. From the cockpit, the feeling is of a single propulsion source under the hood. Mode changes are imperceptible—and best among the year’s new crop of hybrids, the award committee believes.

Iorio cites three keys to the Fusion Hybrid’s calibration success. “First, we have outstanding hardware,” he notes. “Second, the calibration team which I lead has very close cooperation with our software team—all the controls are developed in house. Thirdly and perhaps most importantly, the teams that are solving the ‘musts’ and the ‘wants’ are very closely integrated. They both have the same goals.”

The realization that those goals were met came during the final engineering signoff drive last year.

“We were out West, going through Death Valley with the air conditioning set on ‘max,’ Iorio recalled. “We were getting around 40 mpg on the highway [the Fusion Hybrid is EPA-certified at 41 city/36 highway].

“And through the drive the car’s overall seamlessness as a hybrid just hit us, even given the amount of time we’d all spent in the vehicle,” he said. “That’s when I realized we had something really special.”