SERCOS Energy Specification Released

The SERCOS vendor organizations have announced the release of the energy profile specification for SERCOS III. The goal of the Energy Profile is to use intelligent control algorithms and Ethernet networking to monitor and manage energy usage on automated machines.

"Products are already under development and will be available in 2011," says Peter Lutz, managing director of SERCOS International.

SERCOS Energy is an application layer profile that defines parameters and commands for reducing energy consumption in a uniform vendor-independent manner. The control reads out parameters for each SERCOS Energy component on a SERCOS III network, receiving status information and detailed consumption values. Depending on the situation (such as scheduled or unscheduled breaks), the control can switch connected components such as drives, I/O and sensors into energy-saving conditions up to a complete shut-down, considerably reducing their energy consumption.         

Bosch-Rexroth is already doing work on an energy profiler for its MTX series of CNCs.  The software looks at the energy consumption of a given cycle, and then comes back with recommendations on how to alter the cycle.  With or without that energy analysis, it can selectively reduce energy usage or shut down completely the energy consumption of devices on a machine.

"All of that functionality requires pieces of the SERCOS Energy Profile standard to get information from peripheral devices on the energy they are consuming, and to selectively control energy consumption," says Scott Hibbard, vice president of technology for Bosch-Rexroth. "With a pump, for example, you may not want to put current sensors on every pump. But you may be able to embed information in the pump on the energy required to get up-to-speed, energy usage to pump or recycle coolant, and energy used to start or stop operation."

Hibbard says that data available to the control system will allow it to intelligently determine if the pump is required and if it is possible to shut down or idle pump operation for a specific timeframe. To control the peripherals on-the-fly, the system needs information on energy consumption under full load, idle mode and the energy required to both get up to speed and stop the device. With that information, the control system can do its calculations, and then also be able to command the device to run at full speed, shut down or go into a low power consumption mode to optimize energy usage.

"In the end, the goal is to manufacture parts with the least amount of cost and energy usage as possible, and still be productive which is a third variable in the equation," says Hibbard. "There is a need to find out the total amount of production and the piece cost in energy for each of the components manufactured."

"Today using function blocks in our controls, we estimate how much energy a coolant, lube or hydraulic pump consumes in terms of energy. We have very accurate data from the drives because we have used existing IDENTS or sets of parameters that we will be able to switch over later to the Energy Profile," he adds.

Applications developed at this point require participation by the end user to analyze and intelligently look at the machine cycle. Often there are decisions on whether, for example, making a part faster will actually consume less energy per part. Often energy consumption is reduced by upping the productivity of the machine, especially on metal cutting machines with significant energy usage during the idle periods. But the quick win is to not allow these machines to idle for too long: either make parts or completely shut down the machine.

Hibbard says the standard is written so that the peripherals don't require a high level of intelligence. The ideal for the main control software is that every device has current or voltage measurement capabilities, and power calculation capabilities available on-the-fly. But he acknowledges that is probably unrealistic on very small pumps, for example.

Through testing, a manufacturer can know what each device consumes in terms of energy. If manufacturers test each component and provide average consumption data while running or idling and embed that into the device itself, the intelligence required in the device is limited. The idea is that devices with memory would be hooked to a SERCOS network which would find devices active on the network and determine if they support the Energy Profile.

While work is being done on perfecting the software at the control level, there is a limited amount of data available from the peripherals. The more devices that come online that can provide data, the more accurate assessment that can be made on the machine's energy consumption and energy used to produce a given part.

"Today we know the energy consumption of SERCOS drives while they are operating or idling," says Hibbard. "With hydraulic pumps which we manufacture, we can measure or make accurate estimates as well. But for other devices, it is uncertain whether we can derive any meaningful information from them or not, and often you can't."

"We can't exploit any type of idle capabilities and don't have an accurate or automated way to assess energy usage," he adds. "But we want to get to a point where a machine builder or packaging company looks for devices that conform to the SERCOS Energy Profile. The controller software would detect these devices on the machine, and use the energy usage data to make more intelligent decisions on machine operation.

At that point, there is less work for the machine builder to optimize the energy consumption of the machine."

In discrete manufacturing, there is a significant opportunity to save by limiting energy usage during idle time. As much as 20-25 percent of the total power consumption on discrete manufacturing machines occurs during idle time. That time is not just limited to sitting and waiting for parts, but also during part transfers and waiting for tooling changes.

On continuous process machines, there is not as much of an opportunity because they are typically running 24/7. But there are opportunities to line-up and level off energy consumption by seeing what the energy consumption is for the various devices and making recommendations to optimize efficiency.

An 8-page whitepaper describing SERCOS Energy can be downloaded from http://www.sercos.com/literature/pdf/SERCOS_Energy_Whitepaper_V10.pdf