Systems That Talk Together, Are Efficient Together

Design teams take a holistic view, linking engines, transmissions, hydraulics, and aftertreatment systems to boost efficiency and performance.

February 1, 2014

Terry Costlow

When engines and transmissions are tightly linked with good communications, there’s more potential for downsizing engines to trim costs. (Perkins)

The need to trim fuel consumption and emissions is forcing design teams to take a broader look at equipment operations, linking various systems so they work together closely. Engines, transmission, hydraulics, and even aftertreatment systems share data so that demands and power output are coordinated for optimal performance.

Advanced electronics are being used to analyze ambient temperature and many other parameters making it possible to make the most of every drop of fuel. The benefits extend beyond fuel consumption, even extending component lifetimes by reducing friction.

“When the engine and transmission know more about the operating conditions of the other systems, the operation of the entire powertrain can be set to the most efficient point using data-based criteria rather than a generic set of rules,” said Chris Mays, Senior Technical Specialist at BorgWarner’s Advance Engineering Group. “For example, the system can warm up faster for friction reduction as well as for aftertreatment conversion efficiency.”

Cummins and Eaton paired an engine and a transmission to cut energy consumption.

More powerful controllers also let OEMs customize installations. Typically, machine developers target specific characteristics related to transient response, smooth and stable equipment operation, or efficient use of equipment. ECUs ensure that engines stay near their sweet spot for longer periods so engines don’t have to be oversized to meet peak requirements.

“The benefits are significant, as it is possible to automatically control the engine and transmission to operate in the most efficient points without compromising machine performance,” said Mike Cullen, Perkins’ Product Marketing Specialist. “It is also possible to monitor and anticipate machine load, which allows us to work with our customers when considering engine downsizing.”

Smart shifting

This right-sizing extends to transmissions. With integrated controls, the transmission can reduce the worst-case condition to its mechanical limits. That lets the transmission maximize the engine’s output.

Adjusting operations in response to changing conditions such as temperature helps MTU improve performance and extend engine life.

“Active torque limiting allows lower cost transmissions without sacrificing reliability or durability,” an engineering spokesman from Cummins said. “A transmission can sometimes be limited by having to avoid torque capacity in lower gears or by component stress during gear shifts. By using advanced electronics, the transmission has the ability to limit engine torque or power output when needed, but allow full or higher torque when possible.”

The benefits extend to operations in the field. Engines can adapt to the varied conditions seen by equipment, providing optimal performance in a range of environments.

“Advanced electronics allow engine power curves to be optimized along with transmission capability to achieve the best efficiencies from each, particularly with changing environmental conditions, such as altitude, machine load, and ambient temperature,” said James Krueger, Senior Sales Engineer at MTU. “Transmission life and engine life can both be extended in certain situations, for instance, where electronics allow engine torque-limiting or the transmission can ‘teach’ an operator to operate the engine/machine more efficiently.”

The results can be significant for equipment makers striving to meet demanding expectations for fuel conservation. For example, matching a Cummins ISX15 engine with an Eaton Fuller Advantage Series 10-speed automated transmission improves efficiency and trims fuel consumption for on-highway vehicles.

“Sharing data allows the engine to determine the torque curve and power level to match real-time demand, providing additional torque when necessary and better fuel economy as a total unit,” the Cummins spokesman said. “As a tangible example of benefits, the SmartAdvantage Powertrain offers customers a 3-6% improvement in fuel economy.”

Sharing data, sharing power

Deere links transmissions and engines to deliver power to tracks efficiently.

Maximizing efficiency extends beyond the basic powertrain. Engines must also interact well with hydraulic systems. In many existing equipment designs, hydraulic systems sometimes apply loads faster than the engine can accept them. When electrohydraulic controllers and engine controllers communicate, performance and fuel consumption can be improved by managing how loads are applied to the engine.

“Typically, the load is applied and the engine reacts to changes in speed by lugging,” the Cummins spokesman said. “The auxiliary device must be designed so it cannot lug the engine too low in speed or the engine speed must be increased to provide sufficient lugging capability to react. In a more integrated system, the engine can operate at low speed to save fuel when no load is applied, but then receive advanced communication prior to application of a load.”

Engineers try to keep the engine running at its optimal rate when the engine isn’t idling. When loads are added, it’s not always optimal to have the engine or the hydraulic system work at a level that’s very efficient for either system alone. The end goal for many design teams is to get the most overall efficiency.

“Instead of asking for an engine speed set-point to make the hydraulics most efficient, at the possible expense of engine efficiency, the machine could choose a point that means neither engine nor hydraulics are at optimal efficiency, but the net efficiency or productivity is maximized,” Mays said.

Clean communications

For many design teams, tighter emissions regulations have expanded the definition of a powertrain. Aftertreatment systems are now a critical factor that impacts engine operations. Design teams must include treatment technologies as they optimize powertrain parameters.

Intelligent controls from BorgWarner use real-time information instead of generic rules to adjust performance and improve efficiency.

“The aftertreatment system, engine, and transmission need to be optimized as a complete system instead of individual elements,” Mays said. “For example, getting the SCR aftertreatment to its operating temperature quickly means that the engine can move to more efficient operation sooner. The engine needs to interact with fuel injection, throttles, and variable valve train components as well as the transmission to enable a rapid warm-up. This is a system decision to sacrifice lower engine efficiency for a short time to achieve a net overall system benefit for the full operation cycle.”

When all these systems share information continuously, there is a lot of data traveling over networks. Getting the right data to each node at the right time is a challenging task. If the combined systems and networking links aren’t considered as elements of a larger system, problems can arise.

“Another challenge associated with communication between the engine and transmission is obtaining accurate load information at very light loads,” said Michael Pipho, technical lead at John Deere Power Systems. “Aftertreatment technologies also increase the amount of data on the network structure due to additional control requirements and the need to communicate aftertreatment information to operator interfaces. The increased sharing of data among systems can result in high network loading and cause some data latency issues.”

Most developers are using a number of networks linked together using gateways. That provides the necessary bandwidth without adding a lot of complexity.

“As the engine subsystems develop, particularly those related to aftertreatment, it is necessary to use multiple networks separating machine and application data from subsystem monitoring,” Cullen said. “One example is NOx sensors, which run on a different network to that of the machine. As the number of variables increase, the limitations of a network become apparent. To maintain a responsive system and avoid latency issues it is sometimes necessary to rethink the network architecture of a machine.”