CV Petri Kuosmanen

12.11.2020

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-Hydrauliikan professori 2020

-Koneensuunnittelun professori

vuodesta 1999

-Koneensuunnittelun ryhmän

johtaja

-Fuksi (TKK) vuonna 1982

-erikoisalana telojen mittaus ja

koneistus

-patentteja

-entreprenööri

Motto: ”Elämä on kuin tanssia”

Mechatronics Basics: HydraulicsHydraulics

12.11.2020

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Hydraulics

KON-C2004 Mechatronics BasicsPetri Kuosmanen 12.11.2020

Slides by Tapio Lantela, Jyrki Kajaste & Petri Kuosmanen

FLUID

FLUID

” Fluid, any liquid or gas or generally any material that cannot sustain a

tangential, or shearing, force when at rest and that undergoes a continuous

change in shape when subjected to such a stress”Reference: Encyclopædia Britannica

”FLUID POWER” covers both hydraulics (liquids, oil/water hydraulics) and

pneumatics (gas, air).

Hydraulics – power transmission

Mechanical power (T, ω) → hydraulic power (qV, p) with pump- The medium transmitting the power is “incompressible” fluid (oil, water, etc.)

Pressure 𝒑 =𝑭

𝑨[SI unit Pa]

Power 𝑷 = 𝒒𝒗𝚫𝐩 [SI units m3/s and Pa]

A B

Source NeedPower transmission

Pump Actuator

Power transmissionTechnology of converting power to a more useable form and distributing it to where it is needed. (by NFPA)https://www.nfpa.com/home/AboutNFPA/What-is-Fluid-Power.htm Mechanical Hydraulic Mechanical

Hydrostatic transmission

Hydraulic system types

Hydrostatic system Hydrodynamic system

m m

Force and power

mostly linked to

pressure p

Force and power

mostly linked to

flow qV

Change in momentummass flow rate and velocity

(pressure dependent) Force

p= gh

h

F= pAF F

Hydraulic force conversion

If

- Same pressure

- Different area

Then

- Different force

- Different speed

And

• Same power

- (if no friction or leakage)

• power transmission

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https://www.britannica.com/technology/hydraulic-press/images-videos/Illustration-of-Pascals-principle-at-work-in-a-hydraulic-press/170703

Applications of hydraulics

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Applications: Atlas leg actuation

Hydraulic cylinders

Controlled with servo

valves

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https://www.bostondynamics.com/atlas

Boston DynamicsAtlas humanoid robot

Applications: cranes

Telescoping hydraulic boom

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Applications: mining machinery

Hydrostatic driveline

Boom & bucket

12.11.2020

12https://www.hitachicm.com/global/ourbusiness/products/large-excavators-loading-shovels/

Applications: harvester

Hydrostatic driveline

Hydraulic boom

Hydraulic harvester

head

12.11.202013

Pump and motor

Saw motor

Applications: other mobile machinery

Wheel loader with

Hydrostatic driveline

Boom & bucket

12.11.202014

Dump truck

Tractor with

Hydraulic lift

3 point hitch

Applications: paper machine

Hundreds of hydraulic actuators- Roll positioning

- Roll geometry compensation

12.11.2020

15https://www.valmet.com/globalassets/media/downloads/white-papers/roll-services/wpr_rollmoddeflcomp.pdf

deflection-compensated rolls

Applications: airplanes

Elevator, rudder

Landing gear

Brakes

Cargo doors, stairs

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Applications: Hydraulic car brakes

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http://www.weblumen.com/index.php/tools-supplies/tools/83-tools-supplies/tools/72-disc-brake-spreaders

Applications: Hydraulic press

Deep drawing press- Forming sheets by pressing them

into a mold with a huge force

https://www.youtube.com/channel/

UCcMDMoNu66_1Hwi5-MeiQgw

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Applications: every day stuff

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Hydraulic log splitter Hydraulic bottle jack Hydraulic power steering

Pros and cons of hydraulics

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Actuator types

Example system

- Valve controlled

- Power source electric motor

Depending on application

- Pressure level 10−400 bar

- Flow rates 0.1−1000+ l/min

Hydrostatic systems – basic structure

Control of power

mNeed for power

Generationof power

Need for power

Linear movement

cylinder

Rotary movement

motor

Components

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Pumps

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http://www.designworldonline.com/a-quick-and-easy-guide-to-hydraulic-pump-technology-and-selection/#_

Pumps

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Produced flow rate 𝒒𝒗 = 𝒏𝑽𝒓𝜼𝒗

Required torque 𝑻 =𝚫𝐩𝐕𝒓

𝟐𝝅𝜼𝒉𝒎

Required power 𝑷 =𝒒𝒗𝚫𝐩

𝜼𝒕𝒐𝒕

Pump equations

Bosch Rexroth

n = Rotational speed [r/s]

Vr = Displacement [m3/r]

p = Pressure difference between inlet

and outlet [Pa]

qV = Flow rate [m3/s]

v = Volumetric efficiency []

hm = Hydromechanical efficiency []

t = Overall efficiency []

= v hm

More torque and rotational speed input power

needed because of

• Friction (hydromechanical efficiency)

• Leakages (volumetric efficiency)

than in ideal pumps

Ideal and real values for flow, torque and power

Efficiencies < 1

Pump efficiency

hmvt =

n : rotational speed

v : volumetric efficiency (leaks)

hm : hydromechanical efficiency (flow and mechanical frictions)

t : overall efficiency

p0

0

40

20

60

80

100

n = constant

[%]hmv

t

n0

0

40

20

60

80

100

p = constant

[%]

v

t

hm

p : pressure difference

Motors

Often exactly the same structure as in a pump

Types- Axial piston

• Bent axis

- Radial piston

- Gear

- Vane

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http://www.hyspecs.com.au/how-stuff-works/hydraulic-motor/

Parker F11/F12 - motor/pumpsF11 (and F12) are bent axis, fixed displacement heavy-duty motor/pumps.

Often used as a saw motor

Motor

V= 4.9 ccm

m= 5 kg

Ppeak.theor= 41 kW

V= 30 ccm

m= 12 kg

Ppeak.theor= 170 kW

F11 and F12

performance

Flow rate in 𝒒𝒗 =𝒏𝑽𝒓

𝜼𝒗

Produced torque 𝐓 =𝚫𝐩𝐕𝒓𝜼𝒉𝒎

𝟐𝝅

Power in 𝑷 = 𝒒𝒗𝚫𝐩 =𝐓𝝎

𝜼𝒕

Motor equations

Bosch Rexroth

n = rotational speed [r/s]

= angular velocity [rad/s]

Vr = swept volume [m3/r]

T = load torque [Nm]

p = pressure difference between

in- and outlet [Pa]

qV = flow rate [m3/s]

v = volumetric efficiency []

hm = hydromechanical efficiency []

t = overall efficiency []

= v hm

Generalized performance characteristics of hydraulic motors:

Motor parameters

Bosch Rexroth

Low speed Tmax 1−125 kNm

motors nmax 1−1000 r/min

t 0,8−0,95

Middle speed Tmax 50−1000 Nm

motors nmax 200−1500 r/min

t 0,7−0,9

High speed Tmax 10−3000 Nm

motors nmax 200−6000 r/min

t 0,8−0,9

Parker F11 efficiency

F11-19 motors can be

equipped with Power

Boost

which in high speed

applications can

decrease the

mechanical losses by

up to 15%.

F11-5 motor

https://www.parker.com/literature/Literature%20Files/hydraulicpump/cat/english/F11-F12_HY17-8249-US.pdf

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Low Speed High Torque Hydraulic motor

Bosch – Rexroth - Hägglunds CBm radial piston motor

Maximum torque 1.97 MNm

Diameter 1.46 m

Height 1.3 m

Weight 7500 kgTotal efficiency exceeds 97%

Semi-rotary motors (torque motors)

GenerallyRotation angle max 90−720°Torque Tmax 10−300 kNm

Efficiency t 0,6−0,85

http://nptel.ac.in/courses/112103174/module6/lec4/4.html

Cylinders

Double or single acting- Single acting returned by external force.

Symmetric or asymmetric

Generally

- Maximum pressure pmax 16 − 25 − 40 MPa

- Total efficiency ηt 0,8 − 0,9

- Piston diameter Dp 0,01 − 0,5 m

- Stroke length l 0,1 − 10,0 m

http://www.bluebird-

electric.net/oceanography/Ocean_Plastic_International_Rescue/SeaVax_

Hydraulics_Actuators_Autonomous_Robotics_For_Ships_Boats.htm

http://www.globalspec.com/learnmore/fluid_power_components/hydraulic_equipment_components/hydraulic_cylinders

• 100 mm (diameter)

• 350 bar

275 kN

Flow rate 𝒒𝒗𝟏 =𝑨𝟏𝒗

𝜼𝒗

Force balance 𝒑𝟏𝑨𝟏 =𝑭

𝜼𝒉𝒎+ 𝒑𝟐𝑨𝟑

Required power 𝑷 = 𝒒𝒗𝟏(𝐩𝟏 −𝐀𝟑

𝐀𝟏𝐩𝟐) =

𝐅𝐧𝐞𝐭𝐯

𝜼𝒕

Cylinder equations

A1 A

3

F

v

A2

1p

2p

V1q

V2q

A1 = piston area on the working chamber [m2]

A3 = piston area on the opposing chamber [m2]

v = piston speed [m/s]

F = external load force [N]

pout = pressure on the opposing chamber [Pa]

v = volumetric efficiency []

hm = hydromechanical efficiency []

t = overall efficiency []

Telescopic cylinders

Long stroke

Often single acting

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http://hydraulicspneumatics.com/200/TechZone/Cylinders/Article/False/21653/TechZone-Cylinders

Typically for

• dump trailers

• dump trucks

Cylinder size

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http://www.offshore-technology.com/contractors/hydraulics/ruhfus-systemhydraulik/ruhfus-systemhydraulik5.html

D= 500 mm

@ 400 bar

7.7 MN

AIRBUS A380 - Superjumbo

• 3 jacks

• Cylinders made in Finland

• Empty mass 277 000 kg

Manual valves

Controlling booms etc.

Usually spool type

Proportional or logic (ON/OFF)

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Electric valvesElectric actuators as electric interfaces

• Solenoids ON/OFF

• Proportional solenoids proportional valves

• Torque motors servo valves

• Voice coils ”proportional valves”

Servo valve with torque motor Proportional control valve with proportional solenoid

S S

N N

S N

Torque motor (Proportional) solenoid

Valves for control systems (1)

Proportional Directional Control Valve

Rexroth 4WRPH6Step response at 100 % step < 10 ms

Spool valve

Separate control electronics

Proportional Solenoid operated proportional control valves

Proportional solenoidLVDT position sensor

Electronics

can be

also

integrated

into the

valve!

Frequency response of

spool displacement

[Hz]

[Amplitude, dB]

[Phase, ]

Response is

displacement

amplitude

dependent

- Stroke

amplitude

- Phase lag

+/- 5%

+/- 100%

Valves for control systems (2)

http://www.parker.com/literature/Hydraulic%20Controls%20Europe/Manuals%20UK/D_FP_20%205715-658%20UK.pdf

Voice Coil operated Proportional Directional

Control Valve - Parker DFplus

Nominal flow up to 40 l/min @ 35 bars

Step response at 100 % step < 3.5 msMeasured with load (100 bar pressure drop/two control edges)

Spool valve

Voice coilControl electronicsVoice Coil operated proportional control valves

http://www.parker.com/literature/Hydraulic%20Controls%20Europe/HY11-3500UK/PDF_2013/D1FP%20UK.pdf

Size:

NG06 / CETOP 03 / NFPA D03Moving Coil Assembly

v vPermanent

Magnetic Field Assembly

Moving Coil Actuator

Other valves

Pressure relief valves- To protect from over pressure

- Usually connects the protected line to tank

- Necessary component in practice

Check valves- Block reverse flow direction

Shuttle valves- Choose the larger pressure level

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Energy storage and regeneration

Pressure accumulator- Nitrogen gas compressed by the fluid

acts as energy storage

- Pressure depends on loading condition

- Types: bladder, piston, diaphragm

http://www.womackmachine.com/engineering-toolbox/design-data-sheets/tips-on-sizing-accumulators.aspx

http://www.machinerylubrication.com/Read/2305/hydraulic-accumulators

Hydraulic fluid

Oil- Good lubricant

- Environmental hazard

- Health risk

• Food industry

- Expensive

- Fire hazard

- Viscosity index

Filtering- Metal chips, water, air

Water- Needs additives to lubricate

- ”Clean”

- More expensive components

- Fire safe

- Can freeze

- Corrosion

• Stainless steel must be used (or even plastics for low pressures)

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Future of Hydraulics

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Direct Drive Hydraulics

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• Direct Drive Hydraulics (DDH)• Motion of actuators is controlled by

electric motor’s rotation

• Basically valves are not needed

• Pressure losses minimized• Servo motor

• Inverter controlled motor

Direct Drive Hydraulics in the laboratory

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frastructure in the laboratory

Test benches in the Fluid Power Laboratory are unique. The best

place in the world to study the systems.

• DDH systems by leading manufacturers (Bosch-Rexroth, Parker)

• Own architectures and prototypes

• Hydraulic hybrid test system

”Dolores” (Parker)

”Rex” (Bosch-Rexroth)

”DDH-LITE”

Student project developed during

MEC-E5004 - Fluid Power Systems

MEC-E5002 - Mechatronics Project

Digital Hydraulic valvesTapio Lantela’s (Aalto) research

Digital valve system based on

pilot operated miniature valves (pilot main)

4 x 8 on/off valves

Response time < 2 ms

Flow capacity 78 l/min @ 35 bar

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Magnetic sub-

system simulation

Pilot and main valve

Laminated

valve body

Digital hydraulic valves

Selective Laser Melted manifold Enables optimization of flow paths

Enhanced 3D printed version

also made and tested

http://www.tandfonline.com/doi/full/10.1080/14399776.2017.1358025

Improved flow channels

pressure loss reduced up to 49%

Mechatronics in Fluid Power

• Proportional control valves, integrated

• Hydraulic spool valve

• Spool position sensor (LVDT)

• Control electronics (spool position control)

• Option: CAN Bus operated

• Digital hydraulic valves

• Valve units (digital flow control units, DFCU)

• Consisting of multiple ON/OFF valves

• Fast and leak free

• Optimized magnetic circuit, integrated electronics

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Examples

Integrated actuators

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MoogEaton

Servo cylinder with integrated valveCylinder with integrated position sensor

Efficiency

Hydraulic components have often good efficiency

Traditionally designed hydraulic systems have often bad

efficiency- Valve control – throttling

- Constantly rotating pump

- Not recovering kinetic and potential energy

Well designed hydraulic systems can be very efficient

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Pros and cons

Advantages- High power/weight –ratio

- Linear and rotary movement

- Ease and accuracy of control

- Protection against overloading

- Flexible power routing

- Power regeneration readiness

• lifting/lowering

• acceleration/deceleration

Deficiencies- Mediocre efficiency

- Characteristics of fluid

• Possible leakages

- Maintenance

If requirements for

- high force or torque and small component weight and size

- flexible power transmission routing

→ Consider using hydraulics!

Summary

Hydraulics is a power transmission method- High forces nad power from compact actuators

- Good efficiency actuators, often bad efficiency systems (bad design)

- Input power from outside (electric motor/combustion engine)

Hydraulic system consists of- Power source + pump

- Actuators: motor, cylinder, semi-rotary devices

- Valves: on/off, proportional, check, pressure relief

- Sensors: pressure, flow, position, force, temperature

- Fluid: oil, water

- Pressure accumulator, heat exchanger, filters, tank?

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