Drives save energy in test rigs

A Control Techniques product story
Edited by the Engineeringtalk editorial team May 28, 2003

When CP Engineering was looking to establish a technical partnership with a drives company, its shopping list of fundamental requirements excluded many of the main players in the drives market.

In the complex world of automotive testing, the drive system at the heart of each dynamometer rig has to be extremely versatile.

It must encompass a wide range of speeds, extraordinarily fast response times, the ability to 'motor' to simulate over-run and the simulation of engine behaviour in real time.

And that's just for starters.

So, when CP Engineering of Malvern was looking to establish a technical partnership with a drives company, its shopping list of fundamental requirements quickly excluded many of the main players in the drives market.

Although many were able to offer standard drive characteristics, none was able to match the onboard programming versatility of the Control Techniques Unidrive, which gives CP Engineering extra features such as crank starting.

"We now use Control Techniques Unidrive as our drive of choice", says Managing Director, Bob Ceen.

"We had a number of technical issues with other drives and looked at Control Techniques.

We found that the Unidrive gave us all of the features we needed, but, perhaps more importantly, their willingness to give us direct access to their engineering base has proved invaluable in our development of new systems".

CP Engineering manufactures engine and chassis dynamometer test systems, transmission test systems and test rigs for the automotive industry throughout the world.

Many of these feature Unidrive 'universal' AC drives, most often rated between 100 and 450kW and with fully regenerative braking for absorbing the energy output from the engine or vehicle under test.

CP Engineering's 'Cadet' Windows NT-based control and data-logging system's analogue interface is synchronised to the drives closed loop vector control.

"It is crucial that the response of the control loop is consistent, typically 3.25ms cycle time", says Ceen.

"The test systems require real-time control and processing that is precisely synchronised to give the same load/speed profile as a real vehicle.

With Unidrive this is very straightforward", he says.

To simulate gear shifts, the dynamometer's Unidrive has to reverse torque in less than 10ms.

"The engine has to see changes in load in the same time frame as in a real vehicle", explains Ceen.

The drive also has be capable of motoring to simulate overrun conditions and, as energy becomes increasingly costly, the ability to provide regeneration during braking saves the need for external cooling systems and gives an energy payback as power is fed back to the mains supply.

Unidrives offer all of these features as standard.

However, using Unidrives novel plug-in processor modules, the drive can also be used to provide engine starting too.

Cranking software, which is located on the UD70 plug-in module, is designed to protect the drive shaft.

As the engine fires and accelerates, the drive switches to zero torque to simulate engine idling.

This cannot be done with conventional dynamometers using other makes of drive and gives CP Engineering an addition sales feature on its systems.

In a very competitive market, the choice of Unidrive, with its superior dynamic performance, flexibility of programming and communications has been a significant factor in CP Engineering winning key contracts.

At Bath University, against fierce competition, CP Engineering has supplied a sophisticated dynamic test bed for developing methods for automotive engine calibration under transient conditions, for engine mapping applications.

Other systems have recently been supplied to Castrol, Johnson Matthey, Prodrive, Cosworth Technology, Delphi, Shell and Associated Octel.

The Unidrive range of AC drives spans capacities from 0.75kW to 1MW and five operating modes including servo mode.

With plug-in modules, the drive can be tailor made to fit a vast range of different applications, with most of the industry-standard network protocols as well as Control Techniques' own high-speed network, CT-Net being available to simplify communications.

CP Engineering has supplied systems to almost every automotive manufacturer in the world and has well over 300 systems testing vehicle engines, transmissions and other systems for motorcycle and car engines, diesels, gas turbines and Formula One cars.

"The partnership with Control Techniques has proved to be very successful", adds Bob Ceen.

"They have developed an expertise in our market and everyone benefits".

Find out more about this article. Request a brochure, download technical specifications and request samples here.
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