Contents

Table Of Figures ................................................................................................................... 3

1. Introduction ....................................................................................................................... 4

1.1. Classification and features of smart materials ............................................................. 4

1.2. Modern applications of smart materials ...................................................................... 5

1.3. Relevance of smart materials in the automobile industry ............................................. 5

1.4. Recent developments in smart automobiles ................................................................. 6

2. Smart engines, power transmission and control ................................................................. 7

2.1. Engines and engine mounting ..................................................................................... 7

2.1.1. Solid state SMA engine........................................................................................ 7

2.1.2. Electro- or magnetorheological engine mounts ..................................................... 7

2.1.3. Piezohydraulic engine valves ............................................................................... 8

2.2. Air intake systems ...................................................................................................... 9

2.2.1. Shape Memory tumble flaps ................................................................................ 9

2.3. Transmission systems ............................................................................................... 10

2.3.1. Temperature compensation in automatic transmissions ...................................... 10

2.3.2. Dilatant fluid viscous differentials...................................................................... 11

3. Safety and comfort in smart cars...................................................................................... 11

3.1. Safety of automobile occupants ................................................................................ 11

3.1.1. Self-monitoring tyres ......................................................................................... 11

3.2. Pedestrian safety ....................................................................................................... 12

3.2.1. Shape memory fold-under-impact bonnet ........................................................... 12

3.3. Occupants‟ comfort .................................................................................................. 13

3.3.1. Semi-active vibration damping systems ............................................................. 13

3.3.2. Thermoelectric multifunctional car seat for long distance driving....................... 14

4. Smart accessories for high-end automobiles .................................................................... 15

4.1. Miniature actuators ................................................................................................... 15

4.1.1. Shape memory alloy based actuators .................................................................. 15

4.1.2. Piezoceramic based ultrasonic motors ................................................................ 16

4.2. Glazing and mirrors .................................................................................................. 18

4.2.1. Electrochromic rear-view mirrors ...................................................................... 18

4.3. Decoration and styling .............................................................................................. 19

4.3.1. Electrochromic panoramic roofs ........................................................................ 19

4.3.2. Electroluminescent chromogenic surfaces .......................................................... 19

5. Conclusion ...................................................................................................................... 20

Bibliography ....................................................................................................................... 22

Table Of Figures

Table 1- Smart materials - Characteristics and examples ....................................................... 4

Figure 1 - Cross section of MPA valve .................................................................................. 8

Figure 2 - Exploded view of piezovalve assembly ................................................................. 8

Figure 3 - Air intake manifold with tumble flap ..................................................................... 9

Figure 4 – SMA resistivity vs Temperature ......................................................................... 10

Figure 5 - Tumble flap actuator showing stretching and retraction springs ........................... 10

Figure 6 - Fuzzy logic control flow for MR damping ........................................................... 13

Figure 7 - (a) Skyhook damping control (b) Conventional damping control ......................... 14

Figure 8 - Applications of thermal SMA actuators ............................................................... 15

Figure 9 - Application of electrical SMA actuators .............................................................. 16

Figure 10 - Double layer piezoceramic vibrator - (a) 3-D view (b) Cross sectional view ...... 17

Figure 11 - Traveling wave displacements in vibrating piezoceramic stator ......................... 17

Figure 12 - Glare dimming with ambient light variation in electrochromic mirrors .............. 18

Figure 13 - Sensor arrangement for smart interior rear-view mirror ..................................... 19

1. Introduction The importance of material technology to humankind is evident from the fact that the

progress of human civilization through the millennia has been characterized historically by

the material which has dominated human technology in that epoch. From the Palaeolithic and

Neolithic Ages where stone was the major material used by man, to the Bronze Age and the

Iron Age, every change in material represents a leap in the scientific and technological

progress of our species. Technology has experienced a huge growth spurt in the last century

and showed us the new Silicon Age. Today, we have gone a step further from using

conventional or „dumb‟ materials and are now looking at materials which can respond to their

environment and adapt their properties. Use of these „smart‟ materials is expected to

characterize technology in the new millennium that we have just now entered.

1.1. Classification and features of smart materials

Conventional materials that have been in use hitherto possess only a single set of physical

properties which cannot be altered by any simple means. The class of materials called smart

materials have multiple sets of properties and can spontaneously change between one

property set and another on the application of an external stimulus. The main types of smart

materials in use today and their characteristic behaviour are shown in Table 1.

Table 1- Smart materials - Characteristics and examples

Classification Characteristics

Examples

Shape Memory Alloys Possess two phases – austenitic and

martensitic – in which shape can differ. On

phase transformation, structure and also

shape is altered to match the original shape

in either phase.

Nitinol

(Ni45%-Ti55%)

Piezoelectrics Produce a charge proportional to the

mechanical stress applied and vice versa in

a reversible effect.

Cane sugar

Rochelle‟s salt

Magnetostrictives Undergo deformation on application of a

magnetic field.

Cobalt

Terfenol - D

Electrorheological /

magnetorheological

Alter their viscosity proportional to the

applied electric voltage or magnetic field

Milk chocolate

fluids respectively.

pH sensitive polymers Swell or collapse depending on the pH of

their surrounding medium.

Polyacrylic acid

Chitosan

Chromogenic systems Change colour based on physical stimuli.

Electrochromic – applied voltage

Tribochromic – friction

Piezochromic – mechanical stress

Halochromic – pH of medium

Thermochromic – temperature

Silver iodide glass

Liquid Crystal

Displays

Non-Newtonian fluids Change viscosity based on applied shear. Custard

1.2. Modern applications of smart materials

Smart materials provide a great advantage in terms of their versatility in adapting to different

environmental and operating conditions. Practical application of smart materials began

around the 1960s with the use of Nitinol wires in spacecraft. With the discovery of newer

classes of materials, smart materials based systems have broadened to include diverse uses

like in automobiles, construction, medical implants, aerospace applications, chemical plants,

architecture and indoor heating. Shape memory alloys are widely used in microactuators and

hold-and-release systems. Piezoelectrics have long permeated households with applications

like the spark-based gas lighter. Chromogenic paints find use as corrosion indicators and

safety indicators in power generation or chemical plants. Electrorheological fluids have a

range of uses from the automated packaging industry for fragile items to automobile

suspensions. Electrochromic windows are becoming common in temperate climates today as

an effective and highly energy efficient means of indoor temperature control. Research is

being conducted on auxetic materials which increase their elasticity on stress application to

explore their possible use as artificial muscles in prosthetics. Thus, most aspects of human

life and comfort offer wide scope for the growth of smart material technology.

1.3. Relevance of smart materials in the automobile industry

The automobile industry, having reached a level of saturation where radical product

innovations are rare and installed production capacity outweighs the consumer demand, is

currently facing a crisis which only the most robust firms are expected to survive. Various

aspects of the automobile have already been optimized and further improvement is minimal,

with diminishing returns on investment in this line. The aerodynamics, structural strength and

fuel efficiency of most automobiles is within a narrow range due to almost all players in the

field having reached the limits of optimization of the design of an automobile. To survive the

crisis by continuing to innovate in this field, it is now more subtle aspects that make one car

more preferred than another by consumers. Smart materials are poised to make this difference

for car manufacturers by replacing conventional components with ones providing better

quality of performance and higher levels of comfort. Hence, most major automobile firms are

currently engaged in bringing out the „smart vehicle‟ which will represent the next stage of

innovation in the product lifecycle of the car.

1.4. Recent developments in smart automobiles

Research on the „smart vehicle‟ concept has been undertaken by industry giants like General

Motors, Volkswagen, Honda, Toyota and Ford Motors. Over 42 patents have been issued to

GM alone concerning the application of smart systems in their product. One version of the

smart car is currently under development at General Motors, which is expected to unveil the

product in early 2010. Work is also underway in university laboratories regarding

development of new smart vehicle systems, either independently or with industry

collaboration and funding.

Patents issued for smart material applications in automobiles include smart structures for

vibration control (1), active airflow control devices (2), ingress and egress system for the

physically challenged (3), intelligent tyres which monitor their own wear (4), self healing

tribological surfaces which remove scratches themselves (5) and automatic rear view mirrors

which can reduce glare from oncoming vehicle lights (6).

Engine performance, passenger comfort and luxury accessories have seen the major impact of

the new technology with most manufacturers adopting the paradigm of making the smart car

a safer, greener and more comfortable means of transportation that is priced to be affordable

to most buyers.

2. Smart engines, power transmission and control

2.1. Engines and engine mounting

2.1.1. Solid state SMA engine

The solid state engine based on Shape Memory Alloys is one of the first applications of smart

materials to be discussed and was proposed by Takemoto et al in 1985 (7). This engine is

intended to supplement a conventional prime mover as a waste heat recovery system and

exploits the phase transformation property of shape memory alloys on the application of

temperature to convert thermal energy directly into mechanical energy. Thermal energy

supplied to a shape memory alloy active component transforms it into an austenitic structure.

When this energy supply is cut off as a result of variations in the supply cycle, the austenite

transforms into martensite, absorbing the supplied thermal energy to do so and changing its

shape to facilitate mechanical actuation. Resupplying of thermal energy reverses the phase

transformation and brings the active component back to the original shape in the austenitic

phase. Such an engine is capable of delivering mechanical power even at low temperatures

and do not require large thermal gradients. However, the energy efficiency is low as

demonstrated by experimental results where output mechanical power of the active

component is significantly less than input thermal energy.

2.1.2. Electro- or magnetorheological engine mounts

The engine block of the automobile is mounted on vibration isolators which perform the dual

function of isolating the engine from vibrations transmitted from the road as well as isolating

the rest of the car from engine vibrations. Rubber pads are conventionally used as isolators

and in some cases fluid viscous dampers are used. The simplest vibration isolation model

shows that transmissibility of force follows different curves having a strong dependence on

damping factor. Transmissibility below and at resonant frequency is higher in case of smaller

damping factors and transmissibility above resonant frequency is higher in case of larger

damping factors. Hence, the ideal isolator is one that has different damping factors above, at

and below the resonant frequency of the system.

Electrorheological and magnetorheological fluids can be used to realise this desired

behaviour by means of a simple current controlled circuit. The fluid is contained in channels

below the engine block. At higher frequencies, lower viscosity is maintained for the fluid thus

reducing the damping factor. At lower frequencies the current applied to the ER fluid or to

the electromagnet in case of an MR fluid increases the viscosity of these fluids thus creating

higher damping. Thus, the bi-viscous behaviour of these fluids is exploited to provide

isolation over a wide range of vibration frequencies.

2.1.3. Piezohydraulic engine valves

Conventional valves employ solenoids for magnetic actuation which consume greater power

and are bulky. Piezoceramics allow the fabrication of microvalves with low power

consumption, smaller size and lower driving voltages. However, these too suffer from the

drawbacks of slow response and low resonant frequency. Multilayer Piezoelectric Actuators

can replace piezoceramics in valve operation with improved response time and greater

reliability. The valve design proposed by G.S.Chung and K.B.Han (8) incorporates a seat die

containing inlet and outlet ports, an actuator die housing the MPA module and separated from

the seat dies by a thin silicon diaphragm and a polydimethylsiloxane sealing pad, all

contained in a stainless steel housing.

The MPA responds to applied voltage and the deformation so produced shifts the silicon

diaphragm up and down thus creating or closing a microchannel for the flow of fluid between

the inlet and outlet ports. Investigation of the characteristics of this valve show maximum

efficiency at a duty cycle of 50% and high non-linearity and reliability. Such a valve can be

used in a car engine to improve the energy efficiency and response time.

Figure 1 - Cross section of MPA valve (8)

Figure 2 - Exploded view of piezovalve assembly (8)

2.2. Air intake systems

2.2.1. Shape Memory tumble flaps

The Euro IV pollution control regulations have made it necessary for automobiles to use

tumble systems to improve engine performance. Tumble flaps are placed in the air intake

manifolds of the engine and are used to control the supply of air leading to tumble flow such

that combustion is improved. Colli et al (9) describe a means whereby such tumble flaps can

be actuated using current controlled shape memory alloy springs.

The linear actuator which controls the position of the tumble flap consists of two sets of

helical shape memory alloy springs of which one is used for stretching the actuator and the

other for its retraction. Phase change is achieved by Joule heating of the spring coils on

passing current and natural convective cooling. Accurate temperature control is necessary to

achieve fast phase variations necessitating a dedicated current controlled power converter.

Thermoelectric modules operating on the Peltier effect accomplish the transfer of thermal

energy from the active set of springs to the inactive set during operation thus reducing the

power consumption of the overall system. For a given applied voltage, the current produced

in the spring coil increases as its temperature rises due to the decrease in specific resistance

resulting from the phase change. At maximum current flow conditions, the phase change to

austenite is complete and spring is in the extreme position. Thus, sampling of the current in

the spring provides feedback on the physical position of the actuator, eliminating the need for

any other sensor. Control of the current flow can maintain the position of the actuator until

the nest trigger without leading to overheating.

Figure 3 - Air intake manifold with tumble flap (9)

Figure 4 – SMA resistivity vs Temperature (9)

Figure 5 - Tumble flap actuator showing stretching and retraction springs (9)

2.3. Transmission systems

2.3.1. Temperature compensation in automatic transmissions

To facilitate the driving experience, cars are today moving away from manual transmissions

and replacing them with automatic transmissions in which there is no requirement of

changing gears by the driver. The Mercedes Benz automatic transmission is detailed by

Stoeckel and Tinschert (10) as using shape memory alloy springs to improve shifting comfort

in diesel engines. The shifting pressure control system and the accumulator each use a spring

whose spring constant changes with temperature. Thus, pressure in the switching elements

can be adapted to the lower torque produced by the diesel engine and shifting pressures and

time can be easily and economically controlled.

2.3.2. Dilatant fluid viscous differentials

Differentials are used in automobile drives to allow for different speeds of the two driving

wheels connected to them in situations like turning. In conditions where the traction at each

wheel is different, a differential that divides the total torque equally between the wheels will

cause the vehicle to lock or skid. A limited slip differential causes torque to be distributed

according to wheel speeds, with the slower wheel receiving greater torque. Mitsubishi

realizes this by the use of the Viscous Coupling Unit which is sensitive to wheel speeds.

Torque is transmitted by means of a viscous fluid that is dilatant or shear-thickening in

nature, i.e. its viscosity increases on application of greater shear stress. The coupling unit

consists of a drum filled with dilatant silicone fluid and containing alternating perforated

discs. When one wheel rotates with a higher speed, the velocity gradient set up in the fluid is

higher and the shear stress increases. In response, the viscosity of the fluid increases causing

the silicone to behave as a near solid and trapping the discs. Power is thus transmitted from

one set of plates to another facilitating movement of the two wheels at unequal tractions.

Such an arrangement is used in the Galant and Eclipse GSX automobiles to facilitate driving

on roads slippery with ice.

3. Safety and comfort in smart cars

3.1. Safety of automobile occupants

3.1.1. Self-monitoring tyres

In August 2000, Bridgestone ordered the recall of more than 6.5 million tyres produced in its

Firestone unit following a US safety investigation (11). The recall prompted enforcement of

laws which required all automobiles manufactured thereafter to be fitted with Tyre Pressure

Monitoring Systems as safety devices to provide a tyre health check for car owners. This led

to the development of „Intelligent Tyres‟ which monitored their own status continuously and

indicated faults or the need for replacement to the driver. Intelligent tyre development faced

numerous challenges like the development of sufficiently robust and miniaturized strain or

pressure sensors and wireless transmission of wheel data.

The sensors to be embedded in the wheels must be miniaturized sufficiently as to be easily

fitted into the tyres without causing any impediments to travel. They must also be robust

enough to withstand the vibrations from the road and also operate under conditions of

accumulated contaminants like dirt. The sensors must be compatible with the tyre rubber and

avoid debonding after some period of use. Also, since the tyres cannot be provided with

batteries which have to be constantly monitored themselves, the sensors must be capable of

scavenging energy from the vibrations encountered on the road.

Piezoceramics are an excellent choice to fulfil most of the requirements of the tyre strain

sensors (12). Surface acoustic wave sensors (SAWS) are used for this purpose which consist

of a metallic transducer or optical fibres arranged on a thick film piezoelectric substrate.

These are capable of monitoring tread deformation and tyre pressure, can harvest energy from

vibrations and are compatible with RF systems for data transfer. Solutions like polyimide

film sensors and Hall effect based sensors are however strong competitors for SAWS and as

such the commercial potential of this concept has not been substantially exploited.

3.2. Pedestrian safety

3.2.1. Shape memory fold-under-impact bonnet

Road safety laws are becoming more stringent world over imposing requirements on cars to

protect not only the occupants but also pedestrians in the event of a collision. The main cause

of injury to pedestrians occurs due to impact with rigid components of the automobile

structure. Efforts are hence being made to increase the „crush zone‟ between the crushable

bonnet and the rigid components below it to mitigate the effects of an impact. One solution is

to employ an active lift which deploys the car bonnet outward on impact thus preventing the

pedestrian from hitting the rigid components within. The high impact forces and small

response times pose major challenges in designing a lift that can be used multiple times on

resetting. Barnes et al. (13) working at the University of Michigan propose one solution

called the SMART – Shape Memory Alloy ReseTable – spring lift which implements

compression springs together with actuators of Shape Memory Alloys to achieve high forces

and quick response. The use of the SMA actuators provides ultra-fast release times for the

expansion of the spring. A controlled path is followed by the bonnet to steer the pedestrian

clear of serious harm in the event of a collision. The bonnet is lowered after release by

gravity and a ratchet helps to recompress the springs and hold them in place until the next

release, making the device ready for another use. The potential of such an idea as a market

feasible safety strategy is currently being evaluated and appears to hold much promise as a

commercially viable solution to more stringent pedestrian safety laws.

3.3. Occupants’ comfort

3.3.1. Semi-active vibration damping systems

At present, purely passive suspension systems are used in automobiles wherein a

conventional spring is used to absorb impacts and a viscous damper to damp out the spring

vibrations. Some high-end automobiles use active suspensions which use onboard electronics

to completely control the vertical movement of the wheels irrespective of road conditions

based on inputs from sensors on the car body. Semi-active suspensions provide better

performance than passive systems and are more reliable and less expensive than active

systems. The first semi-active suspension system was introduced by Mitsubishi in the Galant

model in 1987. These systems typically use a damping element that can be controlled to

provide a known damping force. Various control algorithms have been developed to optimize

the performance of these systems. A characteristic choice for the damping element is smart

material technology, with electrorheological or magnetorheological fluids and shape memory

alloy springs being studied.

Application of electrorheological fluids and magnetorheological fluids to provide controlled

damping force based on the change in their viscosity due to applied electric or magnetic field

has the advantage of eliminating valve control from fluid dampers. Studies (14) have shown

that MR fluids offer better performance than ER fluids in terms of yield strength, required

power input and required fluid volume. High stability, wide operational temperature range

and quick responses make MR fluids an excellent choice for suspensions. A simple magnetic

circuit using an electromagnet with variable current flow to change magnetic field intensity

can control the damping force. Various controller logics like fuzzy controller (15) and

skyhook damping control (16) have been studied for such systems and the technology is

becoming more and more widespread in cars today.

Figure 6 - Fuzzy logic control flow for MR damping (15)

Figure 7 - (a) Skyhook damping control (b) Conventional damping control (16)

MR fluids suffer from the disadvantages of loss of stability due to sedimentation of dispersed

particles, leading to high maintenance costs. An alternative solution proposed is to use

conventional viscous dampers together with controllable shape memory alloy springs as the

controllable active element (17). Such a suspension system shows high degree of non-linear

behaviour but is still characterized by stability. The stiffness of the spring is described as

𝐹 𝑥,𝑇 = 𝐾𝑜 + 𝛼1𝑇 + 𝛼2𝑇2 + 𝛼3𝑇

3 𝑥 + 𝐸𝑥2 + 𝐻𝑥3 + 𝐽𝑥 3

Again, the system can be current controlled as the passage of current heats the springs by

Joule effect thus triggering phase transformation and shape change. Such semi-active

suspensions show considerable improvement over purely passive systems in isolating the

sprung mass of the car from bumps in the road.

3.3.2. Thermoelectric multifunctional car seat for long distance driving

A novel idea has been proposed by Menon and Asada (18) to increase the comfort of

automobile drivers over extremely long drives. The proposal is to include shape memory

alloy actuators coupled with Peltier effect based thermoelectric devices (TEDs) to provide

temperature regulation of the car seat along with massaging action. When current is passed

through the TEDs, a temperature gradient is generated by the Peltier effect. The TEDs are in

close contact with shape memory alloy based actuators. The gradient of temperature set up in

the TEDs causes differential phase change and shape alteration in the shape memory alloys.

Bilayer TEDs can take advantage of the reversible nature of the phase change to set up

variable expansion and contraction in different sections of the actuator thus generating a

wave motion which is used to provide massaging action. The current can be controlled to

produce a given range of temperature in the car seat which will be comfortable to the driver.

4. Smart accessories for high-end automobiles

4.1. Miniature actuators

4.1.1. Shape memory alloy based actuators

The use of shape memory alloy based actuators is advocated in modern automobiles due to

the compact nature of the active components and the extremely fast response times. These

applications were anticipated as early as 1990 as areas for innovation in automobiles. Almost

twenty years later, some of them have entered commercial use while others are still in the

research, development or testing stages. However, the rate of progress has been very high

with almost all projected areas of application having been looked at by researchers and many

new ones conceptualized.

Stoeckel (19) in 1990 surveyed the then prevalent as also projected areas in the automobile

where use of shape memory alloy actuators could find a niche. Stoeckel divides such

actuators into two classes – thermal actuators where the sensory and actuating functions are

integrated and electrical actuators where a unidirectional or reversible motion is generated.

Shape and phase changes in such actuators can be easily controlled as temperature changes

can be effected by Joule heating using a current controlled circuit. The basic design paradigm

utilized is for the actuators to work either against a spring force or a constant external force,

though non-linear applications are also possible.

Figure 6 - Applications of thermal SMA actuators (19)

Figure 7 - Application of electrical SMA actuators (19)

The basic kinds of actuators that can be designed are thermally controlled valves, thermally

compensating Belleville washers, actuating springs and compact locking systems. The major

advantages offered by such smart actuators as compared to conventional solenoidal or

electrical actuators include compactness, noise reduction, lower power consumption, fewer

mechanical parts, large motions with high force and production of non-linear characteristics.

However, in certain applications, concerns include hysteresis and operation in conditions

where the ambient temperature falls within the range of transformation temperatures

triggering the actuator out of hand or failing to reset it.

On comparison with the present scenario, it is seen that almost all applications surveyed by

Stoeckel have become major areas of research for product innovation in the automobile

industry. Hence, smart actuators are one of the largest thrust areas in redefining the

automobile and creating major points of differentiation between competing products thus

helping the automobile industry survive its present crisis and stagnation.

4.1.2. Piezoceramic based ultrasonic motors

Most automobiles using conventional DC motors as actuators suffer from the drawbacks of

low energy efficiency at the low speeds required in actuation and bulky construction. A

method to miniaturize motors and reduce their power consumption involves the use of

piezoceramics to make ultrasonic motors, as proposed by Haertling (20). This has hitherto

been an impractical solution due to the low torques developed by ultrasonic motors. Glenn

and Hagood (21) proposed having a double layer of piezoceramics to increase the torque

supplied by these motors, where such a double sided vibrator was used as the rotor. Oh et al

(22) propose a design using the double sided vibrator as the stator. In both designs, a

travelling wave is set up in the piezoceramic rings. Due to anisotropy of the piezoceramic, the

displacements produced radially and axially to the ring are different resulting in elliptical

motion of any point on the periphery of the stator. Glenn and Hagood use brushes to maintain

electrical contact which is eliminated by Oh et al. In their design, a tangential force is

produced at the periphery where the stator contacts the rotor resulting in friction by which

torque is transmitted from stator to rotor and from rotor to actuator. Comparison with

commercially available products showed the prototype of the two sided stator design as

having almost same speed and efficiency but almost twice the torque and 1.5 times the power

output for a much smaller size.

Figure 8 - Double layer piezoceramic vibrator - (a) 3-D view (b) Cross sectional view (22)

Figure 9 - Traveling wave displacements in vibrating piezoceramic stator (22)

4.2. Glazing and mirrors

4.2.1. Electrochromic rear-view mirrors (23)

A major cause of accidents during night-time driving is glare from rear view mirrors. Light

reflecting off the mirror from the headlamps of vehicles behind one‟s own can momentarily

blind the driver or leave a blind spot on the retina. This phenomenon, called the Troxler

Effect, has been extensively studied by Dr. Alan Lewis of the Michigan College of

Optometry and has been found to increase driver reaction time by up to 1.5 seconds.

The concept of using electrochromic mirrors to reduce the glare and increase driving safety

was developed and pioneered by Gentex Corporation who developed the first self-dimming

mirror in 1987. In its present form, the mirror incorporates an electrochromic gel sandwiched

between a reflector and an ordinary glass pane. A sensor looking ahead of the car detects

ambient light levels and signals the mirror to activate glare detection when ambient light falls

below a certain level. A sensor looking behind the car detects glare from other vehicles and

applies a voltage proportional to the glare intensity. The voltage causes dimming of the

mirror thus reducing the intensity of reflected light perceived by the driver. Both interior and

exterior rear view mirrors can be equipped with electrochromic dimming technology. The

efficacy of such technology in preventing automotive accidents has been recognised

worldwide and more and more car manufacturers have begun to include the self-dimming

mirror as a standard accessory.

Figure 10 - Glare dimming with ambient light variation in electrochromic mirrors (23)

Figure 11 - Sensor arrangement for smart interior rear-view mirror (23)

4.3. Decoration and styling (24)

4.3.1. Electrochromic panoramic roofs

Automobiles in the luxury class like the Maybach 62 produced by Mercedes Benz offer the

option of an integral electrochromic panoramic roof. The roof can be controlled by the user to

go from being completely transparent and offering a complete view of the surroundings or

being completely opaque thus protecting the occupants‟ privacy. The principle of

electrochromic gels incorporated into a glass like matrix as discussed in the preceding section

is again utilised in this application.

4.3.2. Electroluminescent chromogenic surfaces

The Senso concept automobile was developed by Rinspeed in 2005 and unveiled at the

Geneva motor show as a colour changing automobile. Thick film electroluminescence is

employed in the interior finish of the automobile in luminous panels and Liquid Crystal

Displays to give off orange, blue or green patterns of light according to sensory inputs based

on the driver‟s behaviour, which are supposed to have different effects on the driver‟s mood

in conjunction with appropriate background music and scents also produced by the car.

5. Conclusion

Since the discovery of smart materials almost 40 years ago, their incorporation into

engineering and technology has steadily risen - slowly at first but at a great pace in the last 20

years. The automobile sector and smart material technology can be said to share a symbiotic

relationship in that not only is the auto industry one of the most important thrust areas for

smart material applications, so also will smart material technology play a crucial role in

reviving the automotive market.

A wide range of smart materials from solid state shape memory alloys and piezoceramics,

liquid dilatants, solid-liquid phase changing electrorheological and magnetorheological fluids

and interphases like electrochromic gels have found their way into modern automotive

technology. The applications have ranged from power transmission to safety and comfort to

accessories and styling. Smart materials have helped to improve upon existing engineering

solutions and reduce costs of components and maintenance. In addition they have helped the

automotive industry comply with increasingly stringent laws on safety and fuel economy that

would not be possible with conventional solutions.

The strength of smart material technology applied to automobiles lies in their multiple sets of

physical properties which allow engineers wide leverage in designing systems. This also

allows for high levels of integration in systems and reduction in size and number of parts,

thus increasing efficiency and reliability. Very fast response times and high levels of

controllability of such systems have led to their popularity in the transition from purely

mechanical systems to the mechatronic paradigm. However, smart materials still suffer from

the weaknesses of being an incipient field with large gaps in our understanding and modeling

of their behaviour which precludes their optimal use. Lack of stability under extreme

conditions of operation is also a drawback. Where opportunities are concerned, there is

tremendous scope for the automobile to undergo a complete change from its present form into

a system that is far more advanced. Smart materials have the potential to revolutionize the

automobile as we know it today and create a new vehicle that is better equipped to meet the

changing needs of the future. The major threats to smart automobile development are

cutdowns on research in times of recession and competing technologies like active

mechatronic solutions which are more popular and widespread at present.

There are many smart solutions to engineering problems which have already been

incorporated into existing cars. Many more such innovations are under various stages of

research and development awaiting their inception into mainstream commercial automotive

technology. Some of these technologies provide the best engineering solutions at marginal

additional costs of altered design and production. However, some others will slowly be

eclipsed by more effective competing technologies.

In conclusion, having reviewed the recent trends, it is very much evident that the next few

years will witness a revival of the automotive sector with the incorporation of various new

technologies and smart material applications will have a major role to play.

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