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In compliance with Euro regulations, transport managers for long-haul commercial vehicles need to know the remaining life of their brake pads before sending a vehicle out across the Continent. Changing pads too soon is costly and wasteful but not changing them soon enough could be disastrous. With the ability to accurately measure brake pad wear a major manufacturer of commercial brake calipers would be able to gain a substantial competitive advantage over others, providing state of the art brake technology.
To take full advantage of this market opportunity the product would have to be designed, evaluated and tested against specific international standards within 18 months.
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Any measurement device would have to be accurate, robust and provide readily available pad wear data without the need to remove wheels etc. In the event of damage to the device, a false reading of pad wear must not be produced. The sensor should automatically account for the varying gap between the pad and disk to provide a reliable reading. The sensor should be intelligent, providing the ECU with data to allow even very minor changes in braking ratios to even up brake and tyre wear across the axles.
Accuracy
The sensor would have to be accurate to within 1mm of its full scale reading.
Environmental Conditions
Fitted to the axle of a truck the sensor would be subjected to:
Constant high and low frequency vibration
The potential for sudden high energy impacts
Extremes of temperature including very sudden changes
Corrosive metals from brake pad wear
Road dirt and spray
Salt
Hydro-carbons in the form of grease, oil, diesel and petrol
We were confident that our non-contact position sensing technology would be perfect for this application
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| Development Timeline |
JULY 2004 - PROOF OF CONCEPT
Gill Sensors designed and delivered five proof of concept non-contact position sensor samples for a relatively small initial investment. We manufactured these from a combination of machined and rapid prototyped mechanical parts with bespoke electronics. The customer could then perform initial field trials and produce a specification for a fully production-ready sensor. Gill Sensors reassured the customer that we could meet their deadline by producing full project and development plans.
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Proof of concept CAD image
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OCTOBER - DECEMBER 2004 - FIELD TRIALS #1
Fifty-five machined sensors, designated FT1, were produced for the first set of on-bench and on-vehicle trials. We also began designing the production jigs and fixtures ready for mass manufacture, performing a full quality audit on the proposed manufacturer.
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FEBRUARY - MARCH 2005 - PROJECT REVIEW
Gill Sensors' Executive Management produced development plans and organised supply contracts to ensure that the sensor would be available for high volume production in the first quarter of 2006. Feedback from the trials would be incorporated into the next iteration of design.
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APRIL - JUNE 2005 - FIELD TRIALS #2
Another prototype batch of sensors was produced for field trials - mechanically the same as the originals but with modified firmware. Fail-safe operation included ensuring that in the event of damage the sensor would not produce misleading data.
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JUNE - SEPTEMBER 2005 - SPECIFICATION UPDATES - FIELD TRIALS #3
We enabled the customer to add features resulting in a highly evolved and detailed product specification on which all future development could be based whilst still maintaining the planned date for volume manufacture. The FT3 variant was designed along with associated production tooling and subjected to EMC and environmental testing to the highest levels, including thermal shock resiliance testing. The results along with manufacturing reports would be the basis for the final FT4 product.
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SEPTEMBER DECEMBER 2005 - FINAL PHASE
During this final phase before mass-production, minor changes were made to optimise production and minimise costs. Production tooling including injection moulding was commissioned with Gill Sensors providing substantial input to the design of the production cell. Various design variants were produced to match customer-specific applications. Testing, diagnosis and calibration of the pad wear sensor on the production line or in the field was facilitated by the development of a Sensor Service Tool.
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JANUARY 2006 - FULL-SCALE VOLUME MANUFACTURE COMMENCEMENT
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Throughout the project Gill Sensors kept in close contact with the customer, using their expertise to advise them on specifications, compliance testing, optimisation of the production process etc. This ensured that the customer's needs and goals were met. Gill Sensors produced a turnkey solution to the customer's problem within the required timescale. |
| Application Animation |
We have put together a short 3D animation to illustrate the basic principle of operation of this sensor. Please click below to view (Flash 8 required - click here to download)
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