In The Name of Allah - Ferdowsi University of...

lecture 10

Dr. Ali Karimpour (Presented by: Ms. Helmi, Mr Talebi and Ms. Faal) Jun 2015

InstrumentationAli Karimpour

Associate Professor

Ferdowsi University of Mashhad

In The Name of Allah

Dr. Ali Karimpour Feb 2015

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Actuators

Topics to be covered include:

Hydraulic actuatorsPresented by: Ms. Fatemeh Helmi

Pneumatic actuatorsPresented by: Mr. Javad Talebi

Piezoelectric sensor/actuatorPresented by: Ms. Zahra faal

Hydraulic actuators

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Hydraulic Actuator

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A hydraulic actuator is a device for converting

hydraulic power into mechanical power.

There are two types of actuators:

Rotary

Linear

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Hydraulic Actuator Principle

Pascal’s Law

Pressure applied to a confined fluid at any point

is transmitted undiminished and equally

throughout the fluid in all directions and acts

upon every part of the confining vessel at right

angles to its interior surfaces.

Amplification of Force

Since pressure P applied on an area A gives rise

to a force F, so : F = P×A

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Basic Fluid Power Formulas

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Actuator Formulas

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Types of Actuators

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Rotary actuators are called hydraulic

motors, while linear actuators are called

hydraulic cylinders.

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Linear Actuators

Hydraulic cylinders are linear actuators,

that is, they produce straight-line motion

and/or force.

There are two types of hydraulic cylinders:

♦ Single acting

♦ Double acting

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The double-acting cylinder is operated by hydraulic fluid in both

directions and is capable of a power stroke either way.

Single and Double Acting Cylinder

In single-acting cylinder the control pressure

is applied to one side of the piston.

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Applications of Hydraulic Cylinders Actuators

Mining industry

Construction machinery

Defense technology

Automotive engineering

Mechanical engineering

Textile industries

Railways

Power plants

Agricultural machinery

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Different Types of Hydraulic Motors

Hydraulic Gear Motors

Hydraulic Vane Motors

Hydraulic Piston Motors♦ Axial Piston Motor

♦ Radial Piston Motor

Limited Rotation Hydraulic Actuators♦ Vane type

♦ Rack and pinion type

♦ Helical type

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Gear motors are high speed motors. If your

operation requires a lower speed, you can reduce

the output speed of the shaft by using gears.

The operating pressure of gear motors is usually

quite low: between 150 and 250 bar. Modern gear

motors, however, are capable of operating at

continuous pressures of up to 250 bar.

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Key features of gear motors:

Low weight and size

Relatively high pressures

Low cost

Wide range of speeds

Wide temperature range

Simple and durable design

Wide viscosity rangeA major drawback of gear

motors is that they

produce a large amount of

noise.

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Typical parameters are:

Displacement volume: 3 to 100 cc

Maximum pressure: up to 250 bar

Range of speeds: 500 to 4,000 rpm

Maximum torque: up to 400 Nm


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The vane motor rotates as hydraulic fluid at high

pressure flows through the motor to the outlet.

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Key features of hydraulic vane motors are:

Low noise level

Low flow pulsation

High torque at low speeds

Simple design

Easy serviceability

Vertical installation easily

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Typical parameters:

Displacement volume: 9 to 214 cc



Maximum torque: up to 650 Nm

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There are two types of piston motors:

Radial piston type arranged radially in a cylinder block.

Axial piston type arranged parallel to each other and to

cylinder block.

Hydraulic Axial Piston Motors

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Hydraulic Axial Piston Motors

Axial piston motors work with a bent axis design or

swash plate principle.

In the bent axis design, pistons move up and down

within the cylinder block bores. This motion is

converted into rotary movement via the piston ball

joint at the drive flange.

In the swash plate design, pistons move up and down

within the cylinder block and turn it, which then turns

the drive shaft via the connected cotter pin.

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Hydraulic Radial Piston Motors

Typical parameters of axial piston motors:

Displacement volume: 10 to 1,000 cc (multi-

stroke up to 1,500 cc)



Maximum torque: up to 10,750 Nm

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Radial Piston motors include a rotating

cylinder containing equally spaced radial

pistons arranged radial around the cylinder

center line.

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Typical parameters of radial piston motors:

Displacement volume: 10 to 8,500 cc


Range of speeds: 0.5 to 2,000 rpm

Maximum torque: up to 32,000 Nm

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Limited Rotation Hydraulic Actuators

A hydraulic motor is a mechanical actuators that

converts hydraulic pressure and flow into torque

and angular displacement (rotation).

The most common types of rotary actuators are:

Vane

rack-and-pinion

helica

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Vane Actuator

A pressure difference between the two parts causes the

vane to rotate .

The maximum rotation of vane rotary actuators is

limited to approximately 280° in a single-vane model

and approximately 100° in the double-vane

configuration.

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Vane Actuator

Hydraulic Rotary vane actuators have many

applications: Automotive assembly and testing

Construction equipment

Industrial automation

Maximum output torque of single-vane

actuator is 40 KNm and maximum output

torque of double-vane actuator is 80 KNm .

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Rack-and-Pinion Actuator

Rack and pinion actuators consist of a housing to

support a pinion which is driven by a rack with

cylinder pistons on the ends.

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Rack-and-Pinion Actuator

Typical rotary actuator applications are for

working pressures of up to 210 bar for

hydraulic actuators, with rotations of 90°,

180° or 360°.

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Helical Actuator

In the Helical Spline compact actuators (HP)

the piston thrust is converted into torque

through a constant pitch helical coupling.

These actuators act like the Rack and Pinion

ones providing a linear torque curve due to the

constant gear ratio

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Helical Actuator

The range of output torque is 0 to 15000 lb-in and

working pressure is 0 to 300 psi with rotations up

to 360°.

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Actuators





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Hydraulic Actuator

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A hydraulic actuator is a device for converting

hydraulic power into mechanical power.


Rotary

Linear

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Pneumatic Actuators

A pneumatic actuator is a device for converting

pneumatic power into mechanical power.


Rotary

Linear

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Advantages of Pneumatic Actuators

Simplicity of realization relatively to small back and forth motions

Sophisticated transfer mechanisms are not required

Low cost

Good long term(reproducibility)

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High speed of moving;

Ease at reversion movements;

High reliability of work;

Explosion and fire safety;

Good precision;

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Disadvantages of Pneumatic Actuators

Compressibility of the air

Impossibility to receive uniform and constant speed of the

working bodies movement

Difficulties in performance at slow speed

Limited conditions - use of compressed air is beneficial up

to the definite values of pressure

Compressed air requires good preparation

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Pneumatic linear actuators

Pneumatic linear actuators or pneumatic cylinders, are

similar to hydraulic actuators except that they use

compressed gas to generate force instead of a liquid.

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Rotary Actuators

Rotary actuators : A rotary actuator is an actuator that

produces a rotary motion or torque from pneumatic signal.

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Pneumatic Artificial Muscles

The Air Muscle is an extraordinary actuator that is

small, light, simple and 'friendly'. It is soft, is easily

controllable and exceptionally powerful.

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Lightweight: Air Muscles weigh as little as 10 grams -particularly

useful for weight-critical applications.

Lower Cost: Air Muscles are cheaper to buy and install than other

actuators and pneumatic cylinders.

Smooth: Air Muscles have an immediate response. This results in smooth

and natural movement.

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Flexible: Air Muscles can be operated when twisted axially, bent round

a corner, and need no precise aligning.

Powerful: Air Muscles produce an incredible force especially

when fully stretched.

Compliant: Being a soft actuator, Air Muscles systems are

inherently compliant.

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Actuators





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Piezoelectric sensor/actuator

A brief history of piezo effect.

Introducing of piezo electric effect and

inverse piezo effect.

Different shapes of Dura act

Working Principle.

Technology

Working Diagram

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Piezoelectric

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Piezoelectric Sensor/Actuator(Dura act patch

transducer)

Parameters for Bender Actuators

Power Requirements

Fields of Application

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History of Piezo Effect

The term piezo is derived from the Greek word for

pressure.

In 1880 Jacques and Pierre Curie discovered that

an electric potential could be generated by

applying pressure to quartz crystals; they named

this phenomenon the piezoelectric effect.

Later they ascertained that when exposed to an

electric potential, piezoelectric materials change

shape.

This they named the inverse piezoelectric effect.

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.

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Pressure(changing shape) electric potential :"Piezo

electric effect" use for sensor

Electric potential to piezoelectric material changing

shape " inverse Piezo electric effect" for actuator

Introducing of piezoelectric effect and inverse

piezo effect

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Introduction of Dura act patch transducer

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Functionality as actuator and sensor component

Nominal operating voltage from 100 up to 1000 V,

depending on the active layer height ..

Power generation for self-sufficient systems possible

up to the milli watt range Can also be applied to curved

surfaces

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Different Shapes of Dura Act

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Dimensions and Geometric

Shapes

DuraAct patch transducers can be

adapted individually to each

application. This includes a free

selection of dimensions and

geometric shape.The height of the

piezo ceramic determines the

bending properties. Depending on

the operating temperature, various

piezoceramic materials can be

used.

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Arrays

To monitor larger areas, several DuraAct transducers

can be incorporated in one single laminate.

Electrical contacting of the piezo ceramics is

established jointly or individually. If a single

DuraAct element is used both as actuator and sensor,

the piezo ceramic can be built in several layers.

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Special Electronics for Sensor Applications

For sensor data processing, controlling the DuraAct

actuator or for harvesting energy and structural health

monitoring, electronic modules can be connected

close to the transducer. Contact is established using

solder pins or miniature plugs.

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Working Principle of Dura Act

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The piezoceramic plates in DuraAct patch transducers resemble

a capacitor. The ceramic acts as a dielectric between its

metallized surfaces. When voltage is applied, an electric field is

created inside the ceramic. The field causes a uniform lateral

contraction of the ceramic perpendicular to the direction of the

electric field. This behavior is called the transverse piezoelectric

effect.

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Electric field strength Magnitude of the lateral

contraction

When the modules are glued to a substrate, they

effectively transfer force over the whole surface.

Dura Act patch transducers transform changes in shape

to electric current, thereby enabling their use as sensors

or energy sources.

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The piezoceramic response to a change of the

electric field or to deformation is extremely fast

Vibrations in the kilohertz range can be produced or

detected.

The correlation between displacement and applied

voltage is not linear.

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A voltage-to-displacement curve with the typical

hysteresis behavior is shown below

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Technology of DuraAct

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DuraAct patch transducers operate as sensors with

varying Bandwidth reacting to mechanical strain

like impact, bending or pressure and as high

precision positioning or bending actuators.

The standard transducer

design features a

piezoceramic foil

with metalized surfaces

for electrical contact

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The thickness of standard foils used is typically 100

to 500μm, with even thinner layers possible.

Without further processing, these piezoceramic

elements are brittle and difficult to handle.

Embedding them in a polymer structure provides

electrical insulation and mechanical stability.

The result is a module that is ductile and extremely

robust. An alternative design features multiple layer

piezo ceramics, enhancing force generation for the

same operating voltage.

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DuraAct patch transducers are solid state actuators

and therefore have no moving parts. Wear and failure

rates are low. Electrical contact is realized by

soldering, clamping or gluing leads to two pads.

Connecting multiple layers separately allows

separation of the sensor and actuator functionality,

meaning that the transducer can be used as sensor

and actuator simultaneously.

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Working Diagram of DuraAct

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The actuator properties of piezoceramic transducers are

essentially described by two parameters: the blocking

force FB and the free displacement, S0. When a voltage

U is applied to the free (unblocked) actuator, it reaches its

maximum displacement S0. The force required to prevent

any length change at all is called the blocking force, FB.

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A graph of applied force versus actuator

displacement is called the actuator characteristic

curve . It basically follows the line passing

through the points with 0 force and 0 displacement

described above.

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In most cases the actuator acts against an elastic

structure, e.g. when a spring or a metal sheet is

deformed (next Fig). If the load is represented by a

spring (characteristic curve of the spring) with

stiffness of cF, the resulting operating point is the

intersection of the load line with the actuator

characteristic curve.

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The most effective operation occurs when the operating

point is in the middle of the characteristic curve.

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DuraAct actuators are usually glued to a substrate

and transfer the contraction over the whole surface.

In such a configuration, theDuraAct / substrate

combination acts as a bender actuator.

Bender actuators provide fast, high-precision and

repeatable deflection and are used in a wide range of

applications.

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DuraAct patch transducers are based on the

transverse piezo effect,and therefore

contract with an electric field applied.

The bender flexes and exerts a normal

force as shown below.

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For the free, unblocked bender, the free deflection is

W0.

The force required to reduce the deflection to zero is

called the bender blocking force FBW. It is

significantly smaller than the actuator blocking

force. The line through these two points, gives the

characteristic curve for the bender.

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These figures show curves relating the maximum

deflection W0 and the maximum force FBW to the

substrate thickness and elasticity.

These diagrams show the actual deflections and

forces measured with 50 mm substrate samples

made of different materials and a P-876.A15

DuraAct patch transducer.

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To determine the required electrical power for

successful actuator operation, the electrical

capacitance must be known.

Typical DuraAct capacitances are in the

nanofarad range and can be found in the

datasheets.

The electrical capacitance, C, depends on the

piezoceramic type, thickness and area.

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Power Requirements of DuraAct

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For an estimation of the average electrical power, Pm,

knowledge of the operating voltage range and the

excitation frequency is necessary.

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The patch transducers ideally have a

symmetrical structure, i.e. when the transducer is

bent, the same quantity of charge with opposite

sign is generated on both electrode surfaces; it

would not be possible to measure a potential

difference. This makes it necessary to bond the

transducer onto a substrate (e.g. aluminum, CRP or

GRP material), thus producing the conventional

bender structure.

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Previous picture shows the power output as a

function of the displacement.

Displacement charge and power .

It is therefore particularly important to analyze

the energy sources available and to develop a

mechanical design adapted to them which allows

optimum conversion of mechanical energy into

electrical.


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There is an almost linear relationship between power

output and excitation frequency. It is also possible to

see a shift of the optimum load range to smaller values

at higher excitation frequency.


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Why Dura Act?

Custom DuraAct Patch Transducers Flexible choice of size

Flexible choice of thickness and thus bending

ability

Flexible choice of piezoceramic material

Variable design of the electrical connections

Combined actuator/sensor applications, even

with

several piezoceramic layers

Multilayer piezo elements

Arrays

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Research

Industry

Used for integration in structures For adaptive Systems

Energy harvesting

Structural health monitoring.

Printers

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Fields of Application

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Problems

بگوییدودادهیحتوضاختصاربهراپیزوالکتریکاثرعکسوپیزوالکتریکاثر-1دارد؟کاربردعملگرهادرکداموسنسوردرکدام

چهوچیستدیگرهایجنساززیرالیهیکبهtransducerچسباندندلیل-2دارد؟دنبالبهاثراتی

واستنیوتنDuraact256))عملگرپیزوالکتریک(FB)کنندهقفلنیروی-3باشدمیمیکرومتر650آناندازهتغییرمقدارحداکثر

عملگرمشخصهرسماستمطلوب(الفبیابیدراسیستممطلوبکارنقطه(بآنسختیریبضکهکنیممدلفنریباراشکلتغییربرابردرعملگرمقاومتاگر(ج

CF=360N/mmبیابیدراعملگراینکارنقطهحالتایندرباشد

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باشدولت300ولتاژسویینگوباشد90nFقطعهاینخازناندازهحالتیکهدر(د(بگیریددرنظر2Hzرافرکانس)بیابیدراتوانمتوسطمقدار

.کنیدمحاسبهراتوانماکزیمممقدار(ه

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http://piceramic.com/products/duraact-piezoelectric-transducer.html

http://www.piezo.ws/piezo_products/Piezo-Patch-

Transducer/index.php

http://www.materialstoday.com/electronic-

properties/products/duraact-power-piezo-composite-patch-transducer/

http://piceramic.com/

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http://www.roymech.co.uk/Related/Hydrostatics/Hydraulic_moto

rs.html

http://hydraulicspneumatics.com/200/FPE/MotorsActuators/Artic

le/False/6426/FPE-

MotorsActuatorshttp://dta.eu/hydraulics/hydraulic-motors

کتاب هیدرولیک صنعتی تالیف محسن دالیلی و احمدرضا مدینه

References

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http://en.wikipedia.org/wiki/Actuator

http://www.ifps.org/Education/WhitePapers/PneumaticCylinders.

htm

http://encyclopedia.che.engin.umich.edu/Pages/TransportStorage/

Actuators/Actuators.html

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References

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