APPLICATION STORY



 Displacement Sensors in Formula 1
The success of a racing car depends on hundreds of components working together at peak performance under the most extreme conditions. Components such as displacement sensors are designed to control and monitor a growing number of vital functions on racing cars and supply information to engineers that help trim precious seconds off the car’s lap times. Whilst most categories of motor racing do not allow the performance of the suspension to be modified during a race, the use of computerised data logging in testing and practice allows race engineers to tune the suspension to match the particular conditions and type of circuit. Using displacement sensors to monitor the movement of the suspension allows electrical signals (indicating the position of the dampers) to feed back to the logging/telemetry system and then display a graphical representation of the car’s performance around a track. Using the data, engineers can easily recognise areas where improvements can be made, and fine-tune the car by adjusting ride heights and stiffness, to suit a particular track and driver. Movement of the suspension can be sensed by a linear displacement sensor such as a potentiometer or LVDT, attached alongside or in close proximity to the suspension damper. The sensor ideally needs to be protected from ingress of fluids and particles. In some applications, rotary movement of the suspension linkage can be used to attach a rotary displacement transducer, such as a rotary potentiometer or RVDT. The use of linear or rotary potentiometers provides a simple solution, operating from a DC voltage and providing a signal proportional to the movement of the sensor shaft. The high cyclic rate of movement requires a high sensor specification with low noise tracks and protective seals to provide operational long life. In the search for ultimate reliability many of the teams in Formula 1 have switched to LVDT displacement sensors for suspension monitoring. The LVDTs are normally custom-built to suit the particular installation and will provide a longer, maintenance-free service life. Although LVDTs require more complex signal conditioning, most suppliers of data logging equipment can provide suitable modules to interface with a number of LVDTs. Throttle control Throttle control is another area where displacement transducers are playing a key role. Most throttle control systems have a rotary motion, so a rotary displacement transducer, either a potentiometer or RVDT, can be attached to the linkage. The position of the throttle mechanism is usually in a very hostile environment such as the top of the engine or underneath air intake ducts, so either device must be extremely rugged and able to withstand high levels of shock, vibration and high temperatures. Special ‘paddles’ on the driver’s steering wheel electronically control the clutch actuating mechanism on today’s high-performance racing cars, overcoming the need for the driver to use his feet to engage or disengage the clutch. This arrangement allows faster up-changing and down-changing of the gearbox during acceleration and braking. For closed-loop control of the paddle mechanism a linear displacement sensor is attached to the clutch actuator to provide position feedback information to the engine management system. As the sensor is exposed to extreme vibration from the engine and transmission assembly, most Formula 1 cars are fitted with a small footprint, high integrity, short stroke LVDT. Unusually, the Penny & Giles LVDT specified by many teams is based on a standard industrial model that uses welded stainless steel construction, a brazed core assembly and coil terminations specially designed to ensure they survive high vibration and shock. When it comes to braking, recent developments in GT and Formula 1 brake caliper design have enabled systems to be fitted to monitor the wear of the brake pads and discs during a race. Advising the driver to back off by one second a lap can make a significant difference to brake wear. The movement of the brake caliper piston is sensed by a very small LVDT embedded in the caliper body, which has been specially designed to withstand extremes of shock and vibration from the track, as well as the high temperatures from the brake discs. The back of the brake pads can reach temperatures as high as 400°C, whilst the caliper body can reach 150-200°C. On Formula 1 cars up to eight LVDT sensors per car are fitted (one per side, per caliper, per wheel, if pad wear sensing is fitted to front and rear wheels). The signals from the LVDT are fed to the car’s data acquisition system and can tell race engineers the condition of the brake pad and disc wear characteristics. Other sensing applications that are helping to improve motorsport include gear position selection (LVDTs), steering rack position (multi-turn potentiometers) and oil reservoir level (LVDTs). _______________________________________________________ For more information, please contact:- Mike Iles at Penny & Giles Controls Ltd. 15 Airfield Road, Christchurch BH23 3TJ. UK Tel: +44(0)1202-409409 Fax: +44(0) 1202-409475 Email: xsales@pgcontrols.com Website: www.pgcontrols.com June 2000
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