Autonomous: the sys tem acts independently of the driver to avoid or mitigate the [612803]

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INTELLIGENT MOBILE OBJECT OBSTACLE
AVOIDANCE SYSTEM

DISSERTATION THESIS

Graduate : Nicoleta -Denisa SISU
Study program: Virtual Engineering in Automotive Design

Scientific c oord inator: S.L. dr. ing. Cristian Cezar POSTE LNICU

2019

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CUPRINS
Summary ………………………….. ………………………….. ………………………….. ………………………….. …………………… 1
1. Description of the theme and objectives ………………………….. ………………………….. ……………………. x
2. State of art ………………………….. ………………………….. ………………………….. ………………………….. …………….. x
3. Autonomou s Emergency Braking ………………………….. ………………………….. ………………………….. ……xx
3.1. Forward collision warning/break assist ………………………….. ………………………….. ………………… xx
3.2. Collision mitigation ………………………….. ………………………….. ………………………….. ……………………… xx
4. Sensors ………………………….. ………………………….. ………………………….. ………………………….. …………………. xx
4.1. Ultrasonic sensors ………………………….. ………………………….. ………………………….. ……………………… xx
4.1.1 Construction and Operation Principles ………………………….. ………………………….. ……………. xx
4.1.2 Applications ………………………….. ………………………….. ………………………….. ………………………….. xx
5. Arduino hardware ………………………….. ………………………….. ………………………….. ………………………….. ..xx
6. Realization of the theoretical model/experimental ………………………….. ………………………….. ….xx
6.1. Sensor test ………………………….. ………………………….. ………………………….. ………………………….. …..xx
6.2. Final assembly ………………………….. ………………………….. ………………………….. …………………………. xx
7. Aspects of performance, reliability, costs, energy consumption, environmental effects,
maintenance, etc. ………………………….. ………………………….. ………………………….. ………………………….. …….. xx
6. Interpretation of results, own contributions and conclusions ………………………….. ……………. xx
References ………………………….. ………………………….. ………………………….. ………………………….. ……………….. xx
Annexes ………………………….. ………………………….. ………………………….. ………………………….. ……………………. xx

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3. Autonomous Emergency Braking
Many car accidents are caused by late braking and/or braki ng with insufficient force. There
are several reasons for a driver to brake far too late:
• he is distracted or inattentive;
• visibility is poor, for instance when driving towards a low sun;
• a situation may be very difficult to predict because the driver ahead is braking
unexpectedly ;
• a pedestrian crosses the street withou t paying attention.
Several manufacturers have developed technologies which can help the driver to avoid
these kinds of accidents or, at least, to reduce their severity. The systems they have
developed can be grouped under the title:
• Autonomous: the sys tem acts independently of the driver to avoid or mitigate the
accident.
• Emergency: the system will intervene only in a critical situation.
• Warning: the system warns the driver.
AEB systems improve safety in two ways:
• they help to avoid accidents by iden tifying critical situations early and warning the
driver ;
• they reduce the severity of crashes which cannot be avoided by lowering the speed
of collision and, in some cases, by preparing the vehicle an d restraint systems for
impact;

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Most AEB systems use radar (stereo) camera and/o r lidar -based technology to identify
potential collision partners ahead of the car. This information is combined with what the car
knows of its own travel speed and trajectory to determine whether or not a critical situation
is developing. If a potential collision is detected, AEB systems fi rst try to avoid the impact
by warning the driver that action is needed. If no action is taken and a collision is still
expected, the system will then apply the brakes. Some syst ems apply full braking force,
others an elevated level. Either way, the intention is to reduce the speed with which the
collision takes place. Some systems deactivate as soon as they detect avoid ance action
being taken by the driver.
AEB systems are aimed at lower -speed crashes, and accidents involving pedestrian
casualties. This is because:
• 75% of crashes are at speeds under 35km/h ;
• 26% of crashes are front -to-rear low speed shunts ;
• Over 400,000 whiplash claims are made annually ;
• More than 6,000 pedestri ans are killed or seriously injured on UK roads every year ;
• Pedestrian casualties account for 23% of all killed and seriously injured.

Euro NCAP (European New Car Assessment Programme) started including AEB assessment
in its rating scheme from 2014. Seve ral different tests are used to cover the different crash
situations in which AEB should be effective:
City (low speed, low injury risk but high volume):
• Car approaching the back of a stationary target car at speeds from 10 to 50km/h.
(Fig. 3.1)
• Tests at different approach speeds with points awarded for avoidance.

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Fig. 3.1 – Car approaching the back of a stationary target car at speeds from 10 to
50km/h.
Inter -urban (higher speeds, higher injury risk, lower volume):
• Car approaching a slower moving target car at approach speeds from 50 to 80km/h
(Fig.3.2).
• Car approaching a lead vehicle that’s decelerating.
• Tests at different approach speeds and differen t headways/ deceleration with
points awarded for avoidance and mitigation.

Fig. 3.2 – Car approaching a slower moving target car at approach speeds from 50
to 80km/h

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Pedestrian (high injury risk but smaller volume):
• Pedestrian walks out from the nearside (Fig. 3.3).
• Pedestrian walks out from behind an obstruction (parked car).
• Pedestrian runs out from the far side.

Fig. 3.3 – Pedestrian walks out from the nearside

3.1. Forward collision warning/break assist
Bosch has developed a suite of Predictive Safety Systems (PSS), the aim of which is to warn
drivers of an impending emergency situation, support them and intervene to reduce the
consequences of an ac cident. The descripti on provided in the manufacturer’ s literature
states that the radar sensor used for Adaptive Cruise Control (ACC) monitors a distance of
up to 200m ahead of the vehicle to detect vehicles in the same lane and calculate their
distance an d speed. When a dangerous situation is recognized in the area in front of the
vehicle safety measures are introduced in three stages as soon as an accident is likely. If an

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accident risk is detected an emergency stop is considered by the system to be prob able and
the manufacturer then describes the following actions that can be taken:
➢ Predictive Brake Assistant (PBA)
Prepares the braking system for an emergency stop by pre -filling the circuit with fluid such
that the linings are just in contact with the discs. The tripping threshold of the Hydraulic
Brake Assist (HBA) system is also lowered. In this way Bosch claim that as soon as the
driver initiates braking, full braking performance is available , around 30ms earlier than
without the system, significantly shortening braking distances. Bosch suggest that this will
offer substantial safety benefits because only one -third of drive rs react to an emergency
braking situation with a full brake application and also state that “most drivers are so
hesi tant that hydraulic brake assist is not activated”.
➢ Predictive Collision Warning (PCW)
Module warning the driver of critical situations by applying a short burst of braking, a brief
tug on the seatbelt and visua l and acoustic signals to warn of imminent da nger. Bosch
claimed that a study by the Association of German Insurers shows tha t almost half of all
drivers involved in accidents did not brake at all, prior to the crash. Early warning allows
drivers to react faster to the danger of a collision by takin g corre ctive action and/or braking
to reduce the impact speed, significantly contributing to avoidi ng many accidents and
reducing the severity of collisions.

The Nissan Brake Assist system with Preview Function (BAP) utilizes information provided
by Adap tive Cruise Control (ACC) sensors to judge when e mergency braking application may
be required based on the distance to the followed vehicle and the relative velocity (Tamura
et al, 2001). Figure 3.4 is extracted from the paper b y Tamura et al (2001) and shows that

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when an impending collision is detected a small b raking force is applied to minimize the
separation between the brake pad and rotor to reduce the brake response time.
The small braking force is activated when the target deceleration for stopping without
colliding with the vehicle ahead exceeds 5.88m/s² (0.6g).

Fig. 3.4 – Nissan Brake Assist with a Preview Function (BAP) (Tamura et al, 2001)

Figure 3.5 shows the results of experiments conducted by Tam ura et al (2001) with the
prototype vehicle. It shows that the delay time from the opera tion of the brake pedal to the
rise of the brake pressure was shortened by 100ms with BAP.

Fig. 3.5 – Brake system reaction (Tamura et al, 2001)

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3.2 Collision miti gation
A collision mitigation emergency braking system was fitted to the Toyota Harrier, launched
in 2003 in Japan. Developed by DENSO with the Toyota Mo tor Corporation, the system
identified inevitable obstacles a split second prior to collis ion, automat ically tightened
passenger seatbelts, and activated a pre -crash brake system to help reduce the impact
speed.
Bosch has developed the Predictive Emergency Brake (PEB) as part of the suite of PSS. The
information on this system claims that should the driver fail to react to the warnings
provided by PCW and an unavoidable accident is recognized due to the p osition and speed
of the other vehicle the Predictive Emergency Brake (PEB) is activated. It inter venes in the
driving process of the vehicle, taking control and automatically ap plying emergency braking
at maximum force to respond to the imminent collision, reducing the impact speed in an
attempt to minimize injuries. It is stated that in order that ob ject re cognition and accident
risk assessment is reliable and robust the radar system must be supported by another
measuring system such as video sensors. The Honda Collision Mitigation Braking System
(CMBS) entered production on the 2006 Legend saloon and the 2007 C RV 4×4. It is offered
on several vehicle models in Japan and the USA it has been offered on the Acura (Legend).
European Accords are expected to be offered with the system after the next model facelift.
The aims of the system are to provide as sistance in avoiding rea r end collisions and to
reduce the degree of occupant injury and vehicle damage in such accid ents. The available
literature suggests that Adaptive Cruise Control (ACC) technology is u sed to monitor the
road ahead, the millimetre -wav e radar detects vehicles within a range of 4 -100m in a
horizontal detection area of 16° and a vertical detection area of 4°. The control ECU judges
the risk of a col lision approximately every 0.02s based on the location of the vehicl e ahead

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and the relativ e speed between vehicles. When the closing rate to the vehicle in fron t
increases to a point where a collision is likely to occur, CMBS operates in the following
manner:
➢ A primary warning, comprising an audible warning and a visual „BRAKE ‟ warning on
the d ash display, is given when the space between the vehicles becomes closer
than the set safety distance for „normal avoidance ‟ or „normal cruising ‟. This
warning is given at approximately three seconds time to collision. Depending on the
situation at the ti me, a collision can be avoided with correct braking. At this stage
brake assist will not be activated with light braking because the accident may be
avoided with a normal brake application. Examples of when the collision may not be
avoided at this stage in clude when the relative speed between vehicles is high, the
grip available is low or if the driver ’s braking is insufficient.
➢ If the distance between the two vehicles continues to diminish, CMBS applies light
braking and the driver's seatbelt pre -tensioner is activated by an electric motor
which retracts the seatbelt gently two or three times, providing the driver with a
tactile warning. The audible and visual warnings are also repeated. The secondary
warning i s given at approximately two seconds time to collision. At this stage the
brake assist activation parameters are altered such that it is easily activated to
provide maximum deceleration. Depending on th e situation , the collision may be
avoided if the drive r brakes appropriately, however in the case of high relative speed
or low grip there are cases where the collision may not be avoided.
➢ If, after issuing the primary and secondary warn ings, the system determines that a
collision is unavoidable, the pre -tensioner retracts the driver's and front passenger's
seatbelts and activates the brakes forcefully to reduce the speed of impact and

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mitigate the effects of the collision. At this stage, depending on the situation, it
would be difficult for the driver to avo id the collision with last minute braking.
The literature claims that the Honda CMBS is effective at detecting, large vehicles, cars,
larger motorcycles in the center of the lane, parked vehicles, and roadside furniture.
However, there are some limitation s as described below:
➢ The sensor system is unable to accurately identify relative speeds less than 15km/h.
➢ Pedestrians cannot be detected
➢ Smaller motorcycles and two wheeled vehicles travelling i n the edge of the road,
diagonally parked vehicles and sm all objects such as fallen rocks may not be
detected.
➢ The system will not functio n when the distance between vehicles is very short or
when the conflict is very sudden such as at junctions .
➢ The system may not function in adverse weather conditions Nissan ’s Intelligent
Brake Assist uses laser radar sensors to detect the distance to a preceding vehicle
and the relative velocity. Figure 3.6 shows when there is a risk of a collision with the
vehicle in front and the driver must take avoidance action immediately the system
sounds a warning to prompt action by the driver to help avoid a rear -end collision.
When a rear -end collision cannot be avoided by the driver's action the system
activates the brakes to decelerate the vehicle at a ma ximum deceleration of 0.5g,
thereby helping to reduce occupant injuries resulting from the collision.

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Fig. 3.6 – Nissan Intelligent Brake Assist

The 2006 Mercedes -Benz S -Class is equipped with Brake Assist PLUS (BAS PLUS) and
PRE -SAFE Brake. The availabl e information suggests that bot h systems utilize a single
77GHz radar sensor capable of monitoring a typical three l ane motorway environmen t in
front of the vehicle with a narrow field of view angle of nine de grees up to a distance of
150m. Two additiona l 24GHz radar sensors with an 80° field of view monitor the
area immediately in front of the vehicle up to a distance of 30m . DISTRONIC PLUS is claimed
to be an additional driver assistance system which also relies upon the radar sensors to
provide adaptive cruise control a t speeds between 0 and 200km/h, maintaining headway
to the vehicle in front by automatically braking the vehicle to a standstill if required and then
accelerating the vehicle as soon as the traffic situation allows. Dependi ng on the speed,
automatic deceleration of up to 4m/s2 is possible. Should heavier braking be requ ired an
audible warning is given telling the driver to watch the traffic situatio n and apply the brakes

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if necessary, and a warning ligh t illuminates on the instrument cluster. Daimler Chrysler
claim that Brake Assist PLUS (BAS PLUS) expands BAS into a n anticipatory system which
registers the distance from the vehicle in front, provides an aud ible and visual warning to
the driver when the gap is too small and calculates the deceleration necessary to avert a
collision.
The appropriate deceleration, which may not necessarily imply full ABS braking, will then
be automatically applied as soon as the driver presses the brake. The fact that the system
only prov ides the deceleration necessary to avoid a collision, rather than full ABS braking
that might have been activated by a standard BAS, is claimed to g ive drivers behind the
vehicle more time to react. According to the manufacturers liter ature, PRE -SAFE Brak e is
a supplement to BAS PLUS. Should the driver fail to reac to the warning proved by BAS
PLUS, PRE -SAFE Brake intervenes by autonomously braking the vehicle with a deceleration
of up to 4m/s2 if there is acute danger of an accident. Fig ure 3.7 shows a timeline
representing a typical rear -end collision situation and the warnings provided.

Fig. 3.7 – Warnings provided by PRE -SAFE Brake in typical rear -end collision situation

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The system is active in the speed range between 10 and 180km/h where traffic is
registered in front of the vehicle, and it also reacts when approaching a stationary
queue of traffic providing the vehicle is not travelling at a speed in excess of 7 0km/h.
Collision Mitigation by Braking (CMbB) is a joint development between Ford M otor
Company’s Research and Advanced Engineering group and the Volvo Safety Centre.
Previewed on the Mercury Meta One concept vehicle, the system uses radar and camera
sensors to detect vehicles on the road ahead to determine whether a collision is imminent
based on the position, speed and direction of other vehicles. Using estimates of collision
threat and driv er intent, the CMbB system provides driver warni ng and enhanced brake
control whe n need ed, amplifying the driver ’s braking and automatically applying full braking
when it determ ines with certainty that a collision with another vehicle is unavoidable. It is
claimed th at depending on speed and road factor s, the braking can automatically reduce
vehicle speed by five mile/h or more before an impact. The 2007 Volvo S80 and Ford S -Max
and Galaxy are f itted with a Collision Warning with Brake Support system that continually
monitors the area in front with a rad ar sensor. If the driver fails to react when approaching
a vehicle in front an audible signal and warning light are triggered. The brake linings are
automatically prepared such that they are j ust in contact with the discs and the system will
boost the bra ke forc e if the driver fails to brake hard enough, as well as flashing the brake
lights to warn drivers behind. If the driver does not react to these alerts or start braking and
the risk of colliding wi th the car in front increases, effective braking is ap plied automatically.

In the 2007 LS saloon, Lexus have introduced additional features to the Pre -Crash Safety
(PCS) system. One s uch feature is an obstacle identif ication system that is claimed to pick
up a wide range o f obstacles on the road ahead, including pedestrians and animals, which

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depending on weathe r conditions will be effective in both dayligh t and darkness. The
system combines information gath ered from a 25GHz millimetre -wave radar and a twin –
lens infra -red stereo camera . The camera monitors near infra -red radiation, emitted from
dedicated units built into the car ’s headlamp high -beam projectors, reflected by objects
directly ahead up to 25m. T he PCS system assesses the likelihood of a collision with an
obst acle ahead based on its position, speed and trajectory. If the collision probability is
judged as high a warning buzzer and „brake ‟ alert on the dashboard display are activated.
Additionally, to help avoid an impact, at 1.5s before impact the parameters of the brake
assist are altered to give maximum brake pressure the moment the driver presses the brake
pedal. If the systems determine that a c ollision cannot be avoided the front seat belts are
pre-tensioned an d the brakes are automatic ally applied to reduc e the vehicle speed at
impact. Literature prescribing the maximu m deceleration achieved during autonomous
braking was not identified for the LS saloon but a maximum deceleration of 0.3g was
identified for a similar system in the GS saloon. Volvo is imple menting the Collision Warning
with Auto Brake system on the 2008 models of the S 80, V70 and XC70. The systems
operates using a fusion of data from a long range rad ar (range 155m ahead of the vehicle)
and a camera (range 55m), which is claimed to provi de m ore reliable and efficient object
recognition. When a potential collision is detected a re d light flashes on the head up display
and an audibl e signal is provided. To shorten the re action time the brakes are prepared by
the brake pads being placed against the discs. The brake pressure is also reinforced
hydraulically, ensuring effective braking even if the d river does not press the brake pedal
particularly hard (similar to Daimler Chrysler ’s Brake Assi st Plus system). If the driver
doesn't brake and the sensor system determines that a collisi on is imminent, the brakes
are activated. Auto Brake is designed to lower the impact speed as much as possible.
Depending on the circumstances, it is also possible that the Auto Brake ca n help avoid the
impact entirely. System availability depends on the number and quality of visible road

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markings. The lane markings must be clearly visible for the camera. Poor li ght, fog, snow
and extreme weather conditions can make the system unavailable. Hino Mo tors report on
a collision mitigation braking system for trucks. The system comprises of a millimetre wave
radar sensor, yaw rate sensor and steering wheel angle sensor, the outputs of which are
processed to judge the li kelihood of a collision occurring. Figure 3.8 sho ws that if the
likelihood of a rear end collision with an obstacle ahead is judged as probabl e, audible and
visual warnings are provided to alert the driver and an automatic braking impulse is
triggered to p rovide further warning. Should the driver fail to react to the warnings when
the collision likelihood is judged as being high the system applies full autonomous braking
in order to reduce the impact speed via the vehicle EBS.

Fig. 3. 8- Hino Motors collis ion mitigation braking system intervention
Mercedes -Benz also has emergency braking systems in production for the Actros truck.
Proximity Control automatically ensures the road speed and headway to the vehicle in front
are adapted to changing traffic conditions. A radar system similar to that on the S-Class
monitors the traffic up to 150m in front of the vehicle, calcula ting the speed and TRL Limited

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10 PPR 227 Unpublished Project Report Version: 1.1 di stance between vehicles and
evaluating any changes. To maintain headway the control sys tem can dece lerate the
vehicle by means of the service and auxiliary brake and accelerate the ve hicle using the
cruise control function. Active Brake Assist builds on the function of the P roximity Control
when there is an acute danger of a rear -end collision with a ve hicle ahead. If the traffic
situation does not change and an accident is likely, the driver first receives a visual and an
audible warnin g. If the risk of a collision increases, partial braking (30% of braking p ower) is
initiated to give the driver a furth er warning. If the driver still fails to react, the s ystem
automatically implements an emergency stop. Although the Active Brake Assist cannot
actively prevent accidents, the application of the full braking power ca n reduce the collision
speed and, therefo re, the severity of the accident and its consequences. Regarding future
developments in truck safety, Volvo acknowledge Brake Assistance stating that “it can help
ensure that the truck is braked to the very maximum so as to minimize the collision speed”,
however there is no mention of a system currently fitted to production vehicles. ACC is
availabl e as an option on the Volvo FH and FM models. The driver selects the time gap to
the vehicle in front. The ACC system maintains this time by automatically contr olling the
throttle and brakes using t he engine brake and auxiliary brakes. In situations when the
auxiliary b rakes are not able to maintain the distance, for example if the vehicle ahead
brakes sharply, t he driver is warned by an acoustic alarm and a ligh t on the speedometer.
The driver mu st then apply the normal wheel brakes. When a collision warning system is
included, the system will also warn the driver of stationary vehicles and is activated if a
large object appears within 30m of the front of the truck. The radar sensor system is
operational over a range of approximately 150m with a horizontal and vertical field of view
of 11°.

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Braking systems reactions times depend on the braking tech nology employed. For hydraulic
systems found on passenger cars the rise time to achieve maximum braking effect is
approximately 0.2 to 0.3s at room temperature. The rise time i s dependent on the brake
fluid temperature for a given system, and it was acknowledged that brake system pre -fill
could improve system reaction times. Vehicle deceleration is modulated using a feedback
control system, with automatically applied deceleration values quoted by different
manufacturers as:
1. from 0.2 to 0.4g;
2. greater than 0.5g;
3. 0.6g;
4. 0.8g;
5. maximum deceleration achievable (i.e. full ABS braking), depending on the surface
conditions .
4. Sensors
The American National Standards Institute (ANSI) defines a se nsor (transducer) as "a device
which provides a usable output in response to a specific me asurand" in year 1975. An
output is defined as an "electrical quantity," and a measurand is ''a phys ical quantity,
property, or condition which is measured." The conclusion was that the outpu t of a sensor
may be any form of energy. Many early sensors converted (by transductio n) a physical
measurand to mechanical energy; for example, pneumatic energy was u sed for fluid
controls and mechanical energy for kinematic control. Sensors are systems witch
possessing a variable number of com ponents. Ther e are three basic components that have
already been identified:
➢ a sensor element;

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➢ sensor packaging and connections;
➢ sensor signal processing hardware.

Fig. 4.1- Technological components in current sensor systems

Technological components in current sensor systems are:
➢ sensor element(s) and transduction material(s);
➢ interconnection between sensor elements (electrical and/or mechanical)
➢ input "gate";
➢ output "gate" and interconnection;
➢ package;
➢ modulator of input interconnects;
➢ calibration device;
➢ output signal modifying device (amplifier);
➢ output signal processing system.

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4.1 Ultrasonic sensors(sonar)
An ultrasonic sensor transmit s ultrason ic waves into the air and detects reflected waves
from an object. There are many applications for ultrasonic sensors, such as in intrusion
alarm systems, automatic door openers and backup sensors for automobiles. Accompanied
by the rapid development of in formation processing technology, new fields of application,
such as factory automation equipment and car electronics, are increasing. Ultrasonic waves
are sounds which cannot be heard by humans and are normally, frequencies of above
20kHz. Velocity of wav e propagation is expresse d by multiplication of frequency and
wavelength.
The velocity of an electromagneti c wave is 3×108m/s, but the velocity of sound wave
propagation in air is as slow as about 344m/s (at 20°C). At these slower velocities,
wavelengths are short, meaning that higher resolution of distance and direction can be
obtained. Because of the higher resolution, it is possible to get higher measurement made
large accuracy.
In order to detec t the presence of an object, ultrasonic waves are refl ected on objects.
Because metal, wood, concrete, glass, rubber and paper, etc. reflect approximately 100% of
ultrasonic waves, these objects can be easily detected. Cloth, cotton, wool, etc. are difficult
to detect because they absorb ultrasonic waves. It may often be difficult, also, to detect
objects having large surface undulation, because of irregular reflection. Velocity of sound
wave propagation “c” is expressed by the following formula :
c=331.5+0.607t (m/s) where t=temperature (°C) That is a s sound velocity varies according
to circumferential temperature, it is necessary to verify the temperature at all times to
measure the distance to the object accurately.

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The strength of ultrasonic waves propagated into the air attenuate proportionally wi th
distance. This is caused by diffusion loss on a spherical surface due to diffraction
phenomenon and absorption loss, that energy is absorbed by medium. As shown in Fig. 4.2,
the higher the frequency of the ultrasonic wave, the bigger the attenuation rat e and the
shorter the distance the wave reaches .

Fig. 4.2- Attenuation Characteristic s of Sound Pressure by Distance

4.1.1 Construction and Operation Principles
When voltage is applied to piezoelectric ceramics, mechanical distortion is generated
according to the voltage and frequency. On the other hand, when vibratio n is applied to

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piezoelectric ceramics, an electric charg e is produced. By applying this principle, when an
electric signal is added to a vibrator, constructed of 2 sheets of piezoelectric ceramics or a
sheet of piezoelectric ceramics and a metal sheet, an electric signal is radiated by flexure
vibration. As a reverse effect, when an ultrasonic vibration is added to the vibrator, an
electric signal is produced. Because of thes e effects, piezoelectric ceramics are utilized as
ultrasonic sensors.
As shown in the diagram of an ultrasonic sensor (Fig. 4.3), a multiple vibrator is fixed
elastically to the base. This multiple vibrator is a combination of a resonator and a vibrator
which is composed of a metal sheet and a piezoelectric ceramics sheet. The resonator is
conical in order to efficiently radiate the ultrasonic waves generated by the vibration and
also in order to effectively concentrate the ultrasonic waves at the central part of the
vibrator. Fig. 4.4 shows a finite element method simulation of the vibration of the multiple
vibrators.

Fig. 4.3- Construction of Open Structure Type Ultrasonic Sensor

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Fig.4.4 Simulation of Vibration
Ultrasonic sensors for outdoors use are sealed to protect them from d ew, rain and dust.
Piezoelectric ceramics are attached to the top inside of the metal case. The entrance of the
case is covered with resin. (See Fig. 4.5.)

Fig.4.5 Construction of Enclosed Type Ultrasonic Sensor
For use in industrial robots, accuracy as precise as 1mm and acute radiation are required.
By flexure vibration of the conventional vibrator, no practical characteristics can be obtained
in frequencies higher than 70kHz and, therefore, vertical thickness vibration mode of

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piezoelectric ceramics is utilized for detection in high frequency. In this case, the matching
of acoustic impedances of the piezoelectric ceramics and air becomes important. Acoustic
impedance of piezoelectric ceramics is 2.6× 10.7 kg/m2s, while that of air is
4.3×10.2kg/m2s.
This difference of 5 powers causes large loss on the vibration radiating surface of the
piezoelectric ceramics. Matching the acoustic impedances with air is performed by bonding
a special material to the piezoe lectric ceramics as an acoustic matching layer. This
construction enables the ultrasonic sensor to work in frequencies of up to several hundred
kHz.

Fig.4.5 Construction of High Frequency Ultrasonic Sensors

4.1.2 Applications
Ultrasonic sensors are utilized for many purposes such as measurement applications etc.
For examples of these applications, please refer to the examples in Table 4.1 and the
explanations as follows. Level detection of continuous wave signals (Example 1) is used f or

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counting machines and approximate switches due to the simple circuit construction of
these devices. Example 2 is used in devices such as automatic doors whe re the
environment is very changeable. The system is arranged so th at the instrument m ay
actuate only when a certain number of reflected pulses is detected. And example 2 is also
used for measuring distance to an object, such as the backup sensors of cars. Example 3 is
an application utilizing the phenomenon by which the Doppler effect produces a modulated
signal as an object moves closer or farther away. This is often used for intruder alarm
systems. Example 4 is an application utilizing the change of sound velocity according to the
density and the flow speed of a gas. Example 5 is a method used to count the number of
Karman vortex generated against flow speed and utilize phenomena that ultrasonic signals
level are reduced as Karman vortex passes into the sensor.

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Table 4.1 Application Examples
Fig.4.7 shows the princip les of measuring distance and is called the "pulse reflection
method" which makes it possible to count the number of reference puls es. This method is
used to measure reflection time up to the object between transmitting pulse and receiving
pulse of the ult rasonic wave. The relationship between the distance up to the object L and
the reflecting time T is expressed by the following formula: L=C · T/2 where C is the velocity

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of sound. That is, the distance to the object can be ascertained by measuring the refl ection
time i nvolved in reaching the object.

Fig.4.7- Principles of Measuring Distance
Fig. 4.8 is an example of the installation of an ultrasonic sensor. The housing of the
ultrasonic sensor should be protected with elastic material, such as rubber, sponge, etc.,
and care should be taken so that ultrasonic vibration is not transmitted directly to the
receiver from the transmitter.

Fig.4.8 Example of Installation of Ultrasonic Sensor
6. Arduino hardware

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The Arduino microcontroller is an easy t o use yet powerful single board computer that
has gained considerable traction in the hobby and professional market. The Arduino is
opensource, which means hardware is reasonably priced and development software is
free.

Fig.6.1- Arduino board
The board features an Atmel ATmega328 microcontroller operating at 5 V with 2 Kb of
RAM, 32 Kb of flash memory for storing programs and 1 Kb of EEPROM for storing
parameters. The clock speed is 16 MHz, which translates to about executing about
300,000 lines of C source code per second. The board has 14 digital I/O pins and 6
analog input pins.
There is a USB connector for talking to the host computer and a DC power jack for
connecting an external 6 -20 V power source, for example a 9 V battery, when running a
program while not connected to the host computer. Headers are provided for interfacing
to the I/O pins using 22 g solid wire or header connectors.
The Arduino programming language is a simplified version of C/C++.

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Arduino also simplifies the process of w orking with microcontrollers, but it offers some
advantage for teachers, students, and interested amateurs over other systems:
➢ Inexpensive – Arduino boards are relatively inexpensive compared to other
microcontroller platforms. The least expensive version of the Arduino module can
be assembled by hand, and even the pre -assembled Arduino modules cost less than
$50 ;
➢ Cross -platform – The Arduino Software (IDE) runs on Windows, Macintosh OSX and
Linux operating systems. Most microcontroller systems are limited to Windows.
➢ Simple, clear programming environment – The Arduino Software (IDE) is easy -to-
use for beginners, yet flexible enough for advanced users to take advantage of as
well. For teachers, it's conveniently based on the Processing programming
environme nt.
➢
Open source and extensible software – The Arduino software is published as open
source tools, available for extension by experienced programmers. The language can
be expanded through C++ libraries, and people wanting to understand the technical
detail s can make the leap from Arduino to the AVR C programming language on
which it's based. Similarly, you can add AVR -C code directly into your Arduino
programs if you want to.
➢ Open source and extensible hardware – The plans of the Arduino boards are
publishe d under a Creative Commons license, so experienced circuit designers can
make their own version of the module, extending it and improving it.
The Arduino Uno can be powered via the USB connection or with an external power supply.
The power source is select ed automatically. External (non -USB) power can come either
from an AC -to-DC adapter (wall -wart) or battery. The adapter can be connected by plugging
a 2.1mm center -positive plug into the board's power jack. Leads from a battery can be

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inserted in the Gnd a nd Vin pin headers of the POWER connector. The board can operate on
an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may
supply less than five volts and the board may be unstable. If using more than 12V, the
voltage regulator may overheat and damage the board. The recommended range is 7 to 12
volts. The power pins are as follows:
➢ VIN. The input voltage to the Arduino board when it's using an external power
source (as opposed to 5 volts from the USB connection or other regulated power
source). The voltage can be supplied through this pin, or, if supplying voltage via
the power jack, access it through this pin.
➢
5VThis pin outputs a regulated 5V from the regulator on the board. The board
can be supplied with pow er either from the DC power jack (7 – 12V), the USB
connector (5V), or the VIN pin of the board (7 -12V). Supplying voltage via the 5V
or 3.3V pins bypasses the regulator, and can damage your board.
➢
3V3. A 3. 3-volt supply generated by the on -board regulat or. Maximum current
draw is 50 mA. GND. Ground pins.
Each of the 14 digital pins on the Uno can be used as an input or output, using
pinMode(),digitalWrite(), and digitalRead() functions. They operate at 5 volts. Each pin can
provide or receive a maximum o f 40 mA and has an internal pull -up resistor (disconnected
by default) of 20-50 kOhms. In addition, some pins have specialized functions:
➢ Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial data.
These pins are connected to the cor responding pins of the ATmega8U2 USB -to-
TTL Serial chip.
➢ External Interrupts: 2 and 3. These pins can be configured to trigger an interrupt
on a low value, a rising or falling edge, or a change in value. See the
attachInterrupt() function for details.

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➢ PWM: 3, 5, 6, 9, 10, and 11. Provide 8 -bit PWM output with the analogWrite()
function.
➢ SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support SPI
communication using the SPI library.
➢ LED: 13. There is a built -in LED connected to digital pin 13. When the pin is HIGH
value, the LED is on, when the pin is LOW, it's off.
The Uno has 6 analog inputs, labeled A0 through A5, each of which provide 10 bits of
resolution (i.e. 1024 different values). By default they measure from ground to 5 volts,
though i s it possible to change the upper end of their range using the AREF pin and the
analogReference() function. Additionally, some pins have specialized functionality:
➢ TWI: A4 or SDA pin and A5 or SCL pin. Support TWI communication using the Wire
library.
Ther e are a couple of other pins on the board:
➢ AREF. Reference voltage for the analog inputs. Used with analogReference().
➢ Reset. Bring this line LOW to reset the microcontroller. Typically used to add a reset
button to shields which block the one on the board.
The Arduino Uno has a number of facilities for communicating with a computer, another
Arduino, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial
communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega16U2 on

the board channels this serial communication over USB and appears as a virtual com port
to software on the computer.

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The Arduino software includes a serial monitor which allows simple textual data to be sent
to and from the Arduino board. The RX and TX LEDs on the board will flash when data is
being transmitted via the USB -to-serial chip and USB connection to the computer.
All of the electrical signals that the Arduino works with are either Analog or Digital.

Digital
An electronic signal transmitted as binary code that can be either the presence or absence
of current, high and low voltages or short pulses at a particular frequency. Humans perceive
the world in analog, but robots, computers and circuits use Digital. A digital signal is a signal
that has only two states. These states can vary depending on the signal, but simply defined
the states are ON or OFF, never in between. In the world of Arduino, Digital signals are used
for everything with the exception of Analog Input. Depending on the voltage of the Arduino
the ON or HIGH of the Digital signal will be equal to the system voltage, while the OFF or
LOW signal will always equal 0V.
To receive or send Digital signals the Arduino uses Digital pins # 0 – # 13.

Analog
A continuous stream of information with values between and including 0% and 100%.
Humans perceive the world in analog. Everything we see and hear is a continuous
transmission of information to our senses. The temperatures we perceive are never 100%
hot or 100% cold, they are constantly chan ging between our ranges of acceptable
temperatures. This continuous stream is what defines analog data. Digital information, the
complementary concept to Analog, estimates analog data using only ones and zeros. In the

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world of Arduino an Analog signal is simply a signal that can be HIGH (on), LOW (off) or
anything in between these two states. This means an Analog signal has a voltage value that
can be anything between 0V and 5V.
Analog allows to send output or receive input about devices that run at percentages as well
as on and off. The Arduino does this by sampling the voltage signal sent to these pins and
comparing it to a voltage reference signal (5V). Depending on the voltage of the Analog
signal when compared to the Analog Reference signal t he Arduino then assigns a numerical
value to the signal somewhere between 0 (0%) and 1023 (100%). The digital system of the
Arduino can then use this number in calculations and sketches .[]
Examples of Analog:
• Values: Temperature, volume level, speed, time, light, tide level, spiciness
• Sensors: Temperature sensor, Photoresistor, Microphone, Turntable, Speedometer,

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7.Vehicle braking (dynamic calculus)

Table 7.1 Vehicle dimensions
For the vehicle stopping distance calculus it was chosen a generi c truck with the above
characteristics (Table4.1). The goal is to design a collision warning system by the results of
the stopping distance calculus.
The calculus will be made for various driving surfaces such as: dry asphalt, wet asphalt, dirt,
snow and i ce. The results will be compared to actual sensors ratings in order to see if such
a system is possible to manufacture.
The calculus was realized id PTC Mathcad prime.

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Calculus 7.1 PTC Mathcad

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Calculus 7.2 PTC Mathcad

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Graph 7.1 Braking space[ ]

Table 7.2 stopping distance at various speed[10]
Graph 7.1 shows the evolution of the stopping distance by velocity on various driving
surfaces. The Table 4.2 is extracted from the graph up to a speed of 73km/h this is because
of the o pening angle of the distance sensing sensor (usually 10 -15 degrees) (Fig7.1).
Although sensors are capable of “seeing” at distances over 130m (stopping distance on ice)
the side angle of the sensor will detect objects outside the road or on the other lane of the
road.

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Fig. 7.1 Flow chart diagram