For such a specialised event, this year’s Automotive Testing Expo and its four sister events (see www.ukipme.com for details), which took place over three days in May, attracted a very respectable 11,230 visitors to a brand new exhibition site adjacent to Stuttgart Airport. Automotive testing is very big business and the international audience that this event attracts, regards it as the global industry showcase.
I was joined by my host at the show, HBM, possibly the world’s foremost manufacturer of strain gauges, and invited to meet some of that company’s key sector customers. In addition, HBM was taking advantage of ATE2008 to launch an important new product, the T40 non contact torque transducer, which leading test equipment manufactures such as AVL, FEV, Siemens and D2T have embraced with enthusiasm; but more about that later.
If one fact became clear at this year’s show, it was the automotive industry’s current campaign to reduce development costs and development timescales - and that desire has had an impact on product developments among the industry’s test equipment suppliers. Moreover, like dominoes collapsing one upon another, so too have component suppliers - HBM being prominent among them - felt the pressure to come up with more economical but nonetheless high-performing products to serve these aims. Which is where the new T40 comes in.
This new torque flange is described by HBM as a “budget all-rounder”, which is equally applicable to stand-alone type operations as it is to more complex, expanded measuring chains, on bespoke test benches or as a continuous process monitoring device. One of HBM’s customers, the US dynamometer manufacturer, Anderson Electric Controls beta-tested a 1kNm T40 on a brake test bed system and subsequently described it as an “excellent, competitively priced” transducer for dynamometer applications.
Essentially, the T40 is a non-contact device - there are no bearings or slip-rings to affect the measured system’s dynamics - which ensures that the measured value is a true a representation of the actual torque value in real time. A special sigma-delta converter is used to ensure reliable digital transmission of measurement values from rotor to stator. The robust design features a transmitter coil integrated into the flange and environmentally sealed. The strain gauges are arranged around the inner core of the rotor and sealed along with the electronics within the body of the flange.
Data are transferred digitally via the inductive loop at a transmission speed of 1.0Mbaud with error identification, ensuring insensitivity to interference and no loss of data or accuracy even in applications where EMC is a critical issue. High accuracy (Class 0.05) and stability are obtained using a ratiometric method of measurement - the reference voltage of the analogue-to-digital converter is always equal to the bridge excitation voltage and any drifts thus compensate each other.
The T40 is very compact, compared with its predecessor, the length of the torque flange having been reduced to save space and costs - particularly for test bench applications. The flange is designed to be easily mounted, meeting yet another of HBM’s customers’ demands for test bed systems that can be changed out quickly to facilitate the testing of multiple prototypes.
Due for launch later this year is the TIM40 (TIM standing for torque interface module), a complementary T40 product that will provide both digital and analogue communications interfaces for the transducer. These include scaled and filtered analogue outputs for controllers, fieldbus connectivity (currently Profibus DP and CANopen) and Ethernet (for remote monitoring via an Internet browser).
A key customer
Austrian company, AVL is the world's largest privately owned and independent developer of powertrain systems for internal combustion engines and their associated test systems. The company has installed more than 8,000 automotive dynamometer test rigs throughout the world and has been a key customer for HBM’s torque measuring devices over many years.
At ATE2008, I spoke with AVL Deutschland’s Matthias Renz who described HBM’s torque transducers as being the “best in the world” - a compliment supported by the fact that the T40 is set to feature prominently in future dynamometer designs - some 20% of the company’s business. Renz attributes this impressive take-up to the T40’s optimised pricing, improved accuracy and robustness, and its overall versatility. He reiterated the automotive industry’s current obsession with finding cheaper routes to component testing without compromising quality and safety. “We have to provide cheaper testing systems, but more specifically ‘universal’ test beds that avoid the high costs of test bed customisation,” he says. “In particular, the new hybrid drive chains require a much wider test range and capability. We are very active in this area and the T40 is ideal for this application.”
Data acquisition
Moog FCS was also present at the show. A customer of HBM for some ten years now, the company has an impressive track record in aerospace testing where its hydraulic rigs are widely used for durability testing of airframes and aircraft structures. In recent years, Moog has transferred a lot of its expertise to the automotive sector - an interesting example is illustrated on this page - a multi-axis shaker table (MAST) for the vibration testing of Thule’s automotive roof rack products.
Moog’s partnership with HBM has more to do with static load measurements, strain surveys and data acquisition rather than torque measurement, often involving bespoke test rigs that are in continuous operation for very long periods - a number of years in some cases. Moog’s test systems manager, Stuart Bibb says that the precision and stability of the data acquisition systems deployed on such test beds are vital. With continuous test runs lasting as long as ten years, you need a partner that is going to support you over the entire period and be readily available for problem solving. Moog uses off-the shelf HBM data acquisition hardware and adapts the software to suit the application.