Sensors are in pole position to meet motor racing demands

Each Formula One car features over 100 sensors. However, not only do these need to fit into very limited spaces, but they need to offer the highest performance and reliability throughout the harsh conditions of each race, where they will face extremes of temperature, humidity, vibration and shock. Here Mike lies, marketing manager of Penny+Giles, looks into how sensors have evolved to meet demands, and the applications in which they are being used.

0ver the last 50 years, Penny + Giles has provided creative solutions for position measurement and control across a range of markets, with one example being the aerospace division, where it is essential that products offer reliability under even the most extreme and hostile conditions. Taking experience gained in this sector, however, the company's sensors have now become a benchmark for motorsport applications and are used in numerous series including the American Le Mans Series (ALMS), Formula One (Fl) and Formula Student.

From the moment a leading F1 team adopted a bespoke Penny + Giles sensor as part of its revolutionary active suspension system, to today's Hall effect position sensors, the company can proudly boast that it was the first position sensor manufacturer to enter motorsport and has supplied every F1 championship winning team since 1986.

Motor racing demands
Success in motor racing, and especially in F1, depends on tens of thousands of components working together at peak performance under the most extreme operating conditions. Engines that can rev up to 19,000rpm means a single piston completes 300 cycles per second; brake discs have to withstand operating temperatures in excess of 1,000°C; and gears can be selected up to 4,000 times per race.
Of the 80,000 or so components in a typical F1 car, there are over 100 sensors linked to more than a kilometre of cable. Of these, position sensors are essential in controlling and monitoring systems that supply information to the team's race engineers to help trim all too precious tenths of a second off lap times.

For the 2014 season, Penny + Giles LVDTs, rotary potentiometers and Hall effect rotary and linear sensors are being used by eleven F1 teams representing 22 of the 24 cars.

The challenges of an F1 car
Every F1 car presents a unique challenge because, in effect, each car is a prototype. With designers and engineers focused on performance, weight and size, the sensors have to fit into spaces that are left over!

Other demands faced are that the sensors need to succeed in a two-hour operational race window, in environments where running temperatures can exceed 130°C, with soaks of over 150°C when cars are stationary in the pits or on the starting grid.

During the 2012 season, control and feedback applications for Penny + Giles sensors included gearbox sensing for forward/reverse gear position select and interlock and barrel position; brake sensing including pad wear and master cylinder; engine and pedal sensing including throttle and pedal positioning; power steering spool and rack position, steering angle and front/rear suspension sensing; and hydraulic reservoir position sensing.

Here, sensors for each application have evolved over the years. Some to reduce size and weight, others to eliminate the `noise' associated with potentiometer-based technologies.
In one example, the company was tasked to design and develop a replacement for a gearbox sensor that was particularly oversized for its application. Because it was running off a 12Udc supply, the original sensor also had temperature issues, which made it brittle over time. For the solution, Penny + Giles engineers analysed various materials and subsequently re-designed the sensor using an organic polymer thermoplastic with strong mechanical properties at elevated temperatures. This not only enabled them to reduce the size and weight of the sensor, but also meant it was extremely strong and had a good temperature coefficient.

At the end of that season the team approached Penny + Giles and asked for the sensor to be made smaller, lighter and faster. The result was a sensor that could work from a 5Vdc supply. This enabled them to remove the voltage regulators from within it, further reducing the size and weight of sensor.
Sensors are also used in brake positioning/pad wear sensing, where temperatures can exceed 1000°C. Here, many teams use Linear Variable Differential Transformers (LVDTs).

Over the years, these linear sensors have become smaller, with many teams now using a 6mm diameter LVDT, which is 25% smaller than those being used a couple of years ago and nearly half the diameter of those in use ten years ago. A smaller LVDT means less material is used to mount them, which provides teams with a weight advantage, as well as improvements in dynamic shock and vibration performance resulting from the reduced mass.

In another example, teams have historically mounted a linear potentiometer on brackets alongside the master cylinder to provide measurement feedback. In recent years Penny + Giles has worked closely with manufacturers to integrate a magnet into the push/pull rod and have embedded a Hall effect sensor within the body of the master cylinders. This has eliminated the need for brackets, therefore reducing weight and, in turn, providing a cleaner solution.

Changes and developments
Over the years, linear potentiometers were used for pedal sensing applications, but these needed mounting brackets that added weight. A few years ago Penny + Giles engineers looked at the car's pedal mechanism and developed a two-piece sensor - using the same principle as its NRH style dual-output 'non-contact' rotary position sensor - which is now mounted on the pedal's natural rotary pivot point. This development has helped to reduce the space envelope and eliminate signal noise associated with track wear on potentiometer-based sensors.

Another change is when it comes to the front and rear suspension where there has been a shift from potentiometerbased linear sensors - requiring brackets to mount the sensors along the dampers - to Hall effect rotary sensors. Like in the pedal-sensing applications, these use natural pivot points on the bell cranks.

In another example, Penny + Giles was tasked with developing a steering angle sensor for one team that had limited space because the sensors would be mounted at the end of the steering column within the nose cone.

For the solution, a miniature Hall effect rotary sensor was developed, which exceeded the team's expectations regarding space and has proved to be technologically superior to anything used before. This particular move from potentiometer-based technology to non-contact has proved so popular that other teams are now testing rotary sensors for similar applications.

It's not always about Hall effect technology though. For a recent clutch position application one team had been experiencing problems with cross-talk, wear, temperature instability and electrical noise from the Hall effect sensor supplied by another company. A Penny + Giles LVDT was tested and eliminated all these problems.

Race-proven parts
High-performance ratiometric LVDT's can be supplied in a range of shaft and body configurations to suit clutch, gearbox, engine and brake applications. These benefit from the experience the company has gained in fly-by wire wire control systems for flight-critical aerospace applications; using high-integrity coil, screen and connection assemblies, combined with welded and vacuum brazed
stainless steel construction.

The company's rotary potentiometers are race-proven and ideally suited to providing data acquisition systems with clean, robust signals for throttle angle, steering angle and gear select position indication. The use of highly durable rotary potentiometer track technology provides virtually infinite resolution, low electrical noise and high stability, especially under the extremes of temperature, humidity, vibration and shock experienced over a long operating life.

The Penny + Giles range of contactless rotary and linear position sensors, featuring the latest Hall effect 'System-onChip' technology, have been designed to offer the best combination of materials, mounting styles, sealing systems and cable connections to ensure survival in the most rugged of motorsport applications. Furthermore, they have been tested to withstand severe shock and vibration, and operating temperatures to +170'C.

Sensors under development
Despite its claims for individual sensors, and having its own NAMAS-approved test laboratory on site in Christchurch where engineers can `shake, bake and shock' its sensors, Penny + Giles still can't reproduce a F1 race car environment.

The design of each new sensor therefore relies on the company's design, engineering and experience, rather than the proven, tested parameters provided by last season's product.

February 2014

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