Tyre Asia – May-June 2018

Tyre Asia April/May 2018 79

Adding the sensors after the tyre manufacturing

process appears appropriate from a performance

perspective, but it could be interesting to integrate

them during the tyre fabrication process for

manufacturing or reliability issues. Embedding the

sensors within the rubber itself can be envisioned, but

the materials should be selected to withstand the curing

temperatures. The capacitive sensors only require

conductive electrodes, which open many possibilities

in terms of material used. The piezoelectric sensors are

however more limited. The most common piezoelectric

material (PZT) can lose its properties when heated

above 200ºC. Embedding piezoelectric sensors would

therefore require the use of more exotic materials that

remain poled above 280ºC.

What are the cost factors of your

process to manufacture intelligent

tyres?

Although we have not evaluated the cost of

integrating such sensors, we expect it to be marginal

for the capacitive approach. The capacitive

transducer fabrication itself is well adapted to batch

manufacturing, similar to printing. The Macro Fibre

Composite patches are currently much more expensive,

which was a motivation to develop the capacitive

sensors. A complete sensor for intelligent tyres also

requires the electronics to measure the change in

capacitance and transmit the information, in addition

to the transducer. The cost of high volume microchips

is very low (<1$), but their packaging and integration

to the tyre or wheel can dominate the cost if not well

designed. Finally, an autonomous intelligent tyre also

requires power to drive the electronics. Although it

could be powered by a battery, such as in common

TPMS units, the continuous measurements and

transmission of data in an intelligent tyre would drain

the battery much quicker than in TPMS. Energy

harvesting is therefore an attractive option to power

the electronics from the vibrations, which we have also

been developing. Appropriate harvesting systems are

however not commercially available so their impact on

cost is not clear at this time.

For those developing advanced vehicle

controls, how could you research be

used while designing intelligent tyres?

Measuring the loads directly in the tyre provides the

most comprehensive and rapid information about the

interaction between the road and the vehicle. This

opens a new paradigm in active control strategies,

where the tyre plays a central role, as opposed to

inertial sensors on the vehicle. A complete system

must however combine measurements in the tyre with

active control in the vehicle, so this required the tyre

manufacturers to work closely with automotive OEMs,

which is a hurdle for innovation in this area. A standard

protocol for communication and shared specifications

could overcome this barrier. Further research and

technological demonstrations are however required

to converge towards the appropriate standards. Early

players in the field may also impose their protocols

and therefore establish the industry standards. Our

work provides a basis to use tyre deformations as a

measurement of loads and defines the range for some

of the requirements, such as frequency and load

amplitude. More work is however needed to define

other specifications and communication standards.

B

y fixing the

sensor onto

the rubber, we

can measure

the tyre’s

deformation.

This requires

the sensor

to be highly

flexible, so

the electrodes

were fabricated

using a silver

nanoparticle

ink stamped

onto a flexible

polymer film

Dr Luc G. Frechette