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  • Interview: Kurt Nickerson, Ford Technical Leader, Transmission Attributes and Calibration

Interview: Kurt Nickerson, Ford Technical Leader, Transmission Attributes and Calibration

Getting 10 Ratios Out of Four Gear Sets

Gary Witzenburg
Apr 4, 2017
Photographers: Courtesy of Ford
Kurt Nickerson grew up in Andover, Massachusetts, and earned a mechanical engineering bachelor’s degree from the University of Rochester in 1991 and a mechanical engineering master’s degree from Purdue University in 1993. He then took a job in Ford's transmission group, where he has been ever since. Working mostly on calibration and control electronics for four-speed, then five-, six-, and now 10-speed automatics may sound boring to some, but not to him.
"I grew up a car nut with pictures and posters all over my walls," he says. "I wanted to be an engineer and dreamed of working in the auto industry, and I've have had my dream job all along. I'm in vehicles on a daily basis, working on control systems and software, driving on test tracks, figuring out how to get the best performance, fuel economy and shift smoothness out of every transmission design and application.” And along the way, he has transitioned from car nut to motorcycle nut, and he road-races bikes as a hobby.
This new 10-speed automatic has been his professional passion since its joint-venture effort with General Motors kicked off in November 2012. "It's been a real treat to see it from conception to birth to marketplace," he adds with a grin.
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Truck Trend: What were the program's major objectives?
Kurt Nickerson: To develop the next generation of transmissions to meet fuel-economy regulatory requirements, with constraints on weight, cost, and package size. All OEMs are looking for the most efficient ways to improve vehicle fuel economy, and transmission architecture is a big part of that. It starts with a search on the kinematics, figuring out how to hook up the output from the engine to the driveshaft through a series of clutches and gears with advanced software and the optimum selection of ratios to get an efficient power flow to maximize powertrain efficiency. In this case, we landed on four planetary gearsets and six clutches, with clever ways to hook things up to achieve 10 speeds.
TT: How do you get 10 ratios out of just four gearsets?
KN: It's very different from a manual transmission. Planetary gearsets have a sun gear, a ring gear, and a planet in the middle, and each one has three potential ratios at which it can operate depending on which element you hold (the sun or the planetary ring), which one you drive, and which one you make the output. So clutches to hook up four of them in various ways, we can get 12 or more ratios. Our six-speed has three gearsets, so we've added just one gearset and one clutch and made some packaging adjustments to get to 10 ratios.
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TT: Why 10 speeds instead of eight, nine, 11, or more?
KN: We used optimization software to look at what number of ratios among eight, nine, 10, or 11 would optimize powertrain efficiency, and our analysis showed that there was an advantage in going to 10 speeds over eight and a small advantage over nine. But going further than 10 did not bring an appreciable benefit.
TT: What was this program's biggest challenge?
KN: To manage 10 ratios and six clutches, the software control system is probably more complex than the hardware. Compared to the six-speed, we were adding nearly four times the complexity in terms of the number of transitions we had to manage with the clutches during all the shifts. In some applications, you may be cruising in 10th gear at low rpm but have the capability to shift to any gear between second and 10th, and to have all those gears available, we had to create a clean-sheet control system to maximize efficiency in the clutch controls, how we perform shifts, shift scheduling, the power we would manage and the significant increase in the number of ratios. Just for the transmission, our control system uses more than a million lines of code, and it's very much integrated with all of the other control systems in the vehicle, especially the engine but also the brake control module, the body control module, and all the other modules that communicate with each other real-time. The tremendous effort that went into creating the software control system probably employed at least as many people as on the hardware side.
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TT: Any industry firsts?
KN: This is the industry's first 10-speed automatic, with a large number of technical innovations and patents in both the kinematic layout and the control system. For example, to get the fastest shifting capability, we have casting-integrated direct-acting solenoids—the solenoids are integrated into the castings in the main controls—so the control electronics are acting directly on the hydraulic control valves, rather than indirectly. That is an industry first.
TT: The joint venture with GM is for both rear-drive and front-drive transmissions, and the front-drive is a nine speed. Why not also a 10-speed?
KN: Because the powertrain is packaged transversely, there is not sufficient room between the wheels to fit this 10-speed transmission architecture. So while the front-wheel-drive uses the same fundamental components of planetary gear sets and clutches, the hookups and the layout need to be optimized to package within the east-west environment under the hood.
TT: Anything else you would like to add?
KN: We get the question that, with 10 speeds, isn't it going to be shifting all the time? But a big part of the software design was to come up with a control system that's looking at all of the driver inputs all of the time, looking at over a dozen parameters including where the driver is placing and how fast he is moving the accelerator pedal, how quickly he is steering, how much lateral acceleration, braking rates, engine torque, all of these factors are going into a very sophisticated algorithm to quickly pick the right gear at the right time. And we don't need to operate sequentially through all of these gears. It will often skip over gears. Depending on how the driver is driving, we may pick an upshift sequence that skips second and fourth. There are only two operating modes where we single-step sequentially through all the gears. One is light-pedal acceleration in city driving because that helps maximize fuel economy. The other is wide-open throttle for maximum performance. Everywhere else, under all other driving conditions, we have the capability to skip between any two gears with no interruption.
Photo 5/5   |   Interview Kurt Nickerson F150 Trans
TT: The first applications are in the Ford F-150 Raptor and Chevrolet Camaro ZL1. Are the ratios different?
KN: No, they are the same. Our analysis looked at what would be the optimum ratio span for a potentially large number of applications with different powertrains, and we arrived at 7.4 as the best solution for efficiency. With a planetary automatic transmission, because we're getting 10 ratios out of four gearsets, there is not lot of flexibility the way there is in a manual gearbox. The ratios are locked in because if you change one, you're changing more than one. For example, if I change First gear, I've also changed Sixth and Eighth. They are interconnected.
TT: And it has to be very robust to take all of that torque.
KN: We had to know up front exactly what the duty cycles would be—how much power and torque and how hard they would be driven. Knowing up front that we had these high-power applications, we designed the components to that level of performance. One early prototype unit went into a Raptor that went straight to the Baja 1000 and finished without an issue.



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