Instrumentation Monthly Test | Measurement | Control
Current trends indicate that smaller, more compact, more intelligent displacement measurement sensors are now required, particularly in high performance motorsport applications. Hydraulic cylinders and actuators, for example, are becoming ever smaller and therefore require more compact, ultra slimline position sensors for measuring displacement and piston position. More robust, pressure-resistant position sensors are now required.
With pressure on motorsport teams to minimise the weight of onboard systems, the requirement for extremely compact sensors is also critical, especially if installation space is restricted. This is also true for integration – both in terms of electronics and building more intelligence into the sensor itself, without the need for any bulky, separate controllers.
Precision sensor manufacturer Micro-Epsilon UK recently co-developed a new version of drive electronics for its EDS series of displacement sensors with McLaren Applied Technologies, the official supplier of Electronic Control Units (ECU) to the FIA Formula One World Championship. The custom developed EDS sensor electronics becomes an integral part of the sub-miniature sensor, electronics and hydraulic actuator control system on the engine.
Compared to traditional methods of measuring displacement and piston position in hydraulic actuators such as LVDT’s, the EDS sensor is much more compact in both its length and diameter. It uses a non-ferrous aluminium outer sleeve as its target, which can be easily integrated into the piston rod if required. As Chris Jones, managing director at Micro-Epsilon explained: “This enables the sensor body to be a solid rod rather than a traditional LVDT style with a hollow sensor body and plunger, making it easier for OEMs to assemble and much more robust and reliable, particularly in harsh, on-vehicle environments.”
The EDS sensor is a robust, pressure-resistant position sensor for hydraulics and pneumatics applications. The latest version is ultra-compact with a diameter of just 3mm, which is ideal for miniature hydraulic cylinders and actuators. The sensors are manufactured from a pressure-resistant stainless steel (up to 450bar), can operate to 175°C and withstand extreme vibration and shock levels (up to 300g axial and 100g radial). The sensor electronics and signal conditioning are also extremely compact and mounted onto the engine. They are therefore also subject to harsh shock, vibration, temperature and EMS levels. Compared to an LVDT with similar measurement range, EDS sensors are typically 50% shorter and much narrower in body diameter.
For such compact sensor geometries, it is necessary to use external electronics. However, the electronics are also very compact, typically 20 x 30 x 45mm (long) and it is not necessary to match sensor to electronics like many other sensor solutions i.e. the sensor and electronics are interchangeable.
Another benefit of such a compact design is that the length of the hydraulic cylinder does not have to be increased in order to accommodate a larger sensor (which would increase weight and the overall space envelope). These sensors operate without any contact between the moving parts and are wear-free.
Chris Jones continued: “For the project with McLaren Applied Technologies, we were originally approached by the actuator manufacturer, who wanted to integrate our EDS sensor into its own sub-miniature hydraulic actuator for use in Formula One throttle and turbocharger control applications. The company required a smaller footprint sensor and the 3mm diameter EDS sensor more than met this need. We worked closely with McLaren Applied Technologies, who developed the necessary interface electronics and software to enable our EDS sensor and hydraulic actuator to communicate with their engine control unit. The result is a more elegant, more compact and robust solution for Formula One engines, with a very clean output signal.”
Micro-Epsilon’s standard range of EDS sensors are available for measuring lengths from 100mm up to 630mm. OEM versions can be designed to almost any measurement range, from 10mm to 1m typically. Pressure resistance is up to 450 bar (sensor rod, flange) and standard temperature range is from -40°C to +85°C. The sensors have very short dead-bands at either end of the measurement range. For example, the 250mm sensor has a body length of just 298mm. The sensors are being used in a wide variety of hydraulics and pneumatics applications to measure displacement, position, distance, gaps, deflection, movement, stroke, fill level, immersion depth and spring travel.
