Digital Torque Sensor

The torque-current characteristics of a combined motor-generator developed for a Lotus-based hybrid car have been comprehensively mapped by a TorqSense digital torque sensor. Specialist electromagnetic design company Elektro Magnetix (EMX) of Brighton developed and tested the motor-generator for Lotus Engineering's EVE(Efficient, Viable, Environmental) Hybrid. This is a technology demonstrator that is showcasing many of the medium term solutions that will be used to reduce vehicle emissions.

Jonathan Bremner of EMX explains that the mapping was essential, but could not be done in-house. ''We are a design house, so tend to sub-contact testing to other organisations. With this project we needed to plot out the full range of performance, but had only a tight time window to do all the work.''

So EMX worked with a testhouse to design a simple yet effective test rig. It was not long before the specialist engineers had settled on using a TorqSense torque sensor from Sensor Technology as they could design a rig around it very easily, and then it was very quick and simple to use.
''Normally when taking torque measurements you can spend more time fitting the transducer as they have to be mechanically coupled and use either slip rings, inducing drag, or induction coils that can have high inertia'' says Bremner. ''leading to inaccuracies that it can be very frustrating. But TorqSense is different; as it is a non-contact measurement sensor it monitors the sensor by use of a radio frequency (RF) link. It can be set up in moments, leaving us to concentrate on the analytical work in hand.''
And because TorqSense is digital, its outputs can be fed directly into a computer, where calculations are performed automatically. The result is highly refined information, produced in real time, which designs out the data processing and assessment phases of the test programme.

TorqSense, made by Sensor Technology in Bicester, can be described as a plug-and-play digital torque sensor, which interrogates and analyses a radio signal from a miniature piezo electric detector on the rotating shaft being monitored. The sensor is fully self-contained, can be set up in minutes and generates outputs that can be read locally by a technician or transmitted to computers and control systems for data analysis.

Unlike other torque sensors TorqSense is mechanically simple with its sensors fixed to the shaft and a rotating RFantenna used to allow non-contact coupling with its digital electronics offering immunity from magnetic fields, so there is no need for complicated and delicate slip rings or large transformer assemblies to obtain signals, making it a very cost effective, drag free, low inertia sensor.

Clean motoring
Lotus Engineering believes that hybrid technology is a key route for CO2 reduction. In the medium term it may remain more viable to integrate hybrid technologies into existing model ranges than to develop completely new vehicles.

The EVE Hybrid programme is focussed on establishing the processes for integrating hybrid technology with minimal development time and cost. Engineers from Lotus and its parent company Proton have produced the EVE Hybrid demonstrator, based on a Proton Gen.2 compact midsize car with a 1.6litre gasoline engine. This currently showcases a 'micro-hybrid' start-stop system, a full parallel hybrid drive and Continuously Variable Transmission.