Designing sense into off-highway systems

  • 30-Jul-2011 04:21 EDT

Sensors from companies such as Sauer-Danfoss help electronics and humans use hydraulics effectively.

Regulators are forcing equipment suppliers to reduce emissions, improve fuel economy, and improve safety, while customers are pressing for more features and functions. When design engineers turn to electronic controls to handle these challenges, sensors will be a critical portion of system designs.

Digital controls will provide the interface with human operators and make the decisions for many parameters, so these controls get much of the spotlight. But sensors provide the input that these controllers use to make their decisions. That’s driving solid growth in the number of sensors on most vehicles.

“When you have more intelligence and more sensors, you can control the vehicle much better,” said Joe Maher, Product Marketing Manager at Sauer-Danfoss Inc. “We definitely see more applications for sensors.”

The new emissions regulations in the U.S. and Europe will drive further demand for sensors as OEMs strive to eke the most out of each drop of fuel. These sensors will have to monitor many functions that typically haven’t had any connection with electronic controls.

“When you look at hydraulic filters, you’ll see smart sensors,” said Kirk Lola, North American Marketing Manager at Parker Hannifin Corp.’s Electronic Controls Division. “They need to monitor backpressure and how dirty or clean the fluid is, so they need intelligence. With Tier 4, you’ve got to monitor a lot of parameters, sometimes even things like whether a door’s open.”

While the number of sensors rises, expectations are also increasing. In emissions and other areas, extremely precise control is a central aspect of system designs. For digital controls to make minute adjustments and improve efficiency, they have to get extremely accurate information on the operating conditions.

“The precision of the sensor is one of the key focal areas,” said Terry Hershberger, Director Sales for Mobile Applications Machine Sector Management at Bosch Rexroth. “The system response and accuracy are based on how well the sensor provides the information.”

This demand for more precision is one of the factors that’s prompting a change in the way sensor modules are designed. These modules, which typically sit inside valves, pumps, filters, and other gear, often have some intelligence to process the analog signals collected by the sensing element. Sometimes, these modules can make decisions so remote controllers are free to handle other tasks.

“Depending on the type of module, there can be software embedded at a sensor such as in an application specific integrated circuit (ASIC),” Hershberger said. “Sometimes there’s a driver and some operational know-how at the valve, so much more intelligence is needed.”

While sensor makers provide more precision, system developers must also make these sensors easier for OEMs to integrate. Many embedded sensor modules now have enough software to handle many setup functions, making it easy for engineers to get modules running quickly.

“Many pumps, valves, and motors have compliance blocks, so the signal range and calibration of sensors is already done,” Maher said. “What used to take OEMs days to tune can now be set up by dragging and dropping icons.”

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