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Control and Operating Behavior of Continuously Variable Chain Transmissions

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## Control and Operating Behavior of Continuously Variable Chain Transmissions

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2004 International Continuously Variable and Hybrid Transmission Congress

September 23-25, 2004

Control and Operating Behavior ofContinuously Variable Chain Transmissions

Roland Mölle

- Clamping Systems

- Ratio Control Design during Range Shifts in Autarkic Hybrid

- Expanded Control Layout for Universal Use in Chain Variator Applications

- Summary

Presentation Outline

Typical CVT chain of amodern passenger car:Audi multitronicTorque Capacity up to 300 NmNominal Power 162 kW (V6-3.0)

Pull type Chain in Audi/LuK CVT

- Clamping Systems

- Control Design for Range Shifts in Autarkic Hybrid

- Expanded Control Layout for Universal Use in Chain Variator Applications

- Summary

Presentation Outline

Pressure

- Oil flow on demand

Transducer

Pulley 1

Disadvantages:

- Torque information supplied by engine controller: Poor dynamics and limited accuracy
- Need for high over clamping for security reasons or additional measures
- Oil flow always at maximum pressure level

Pulley 2

Directional

Control Valve

Constant Pressure

Oil Supply

Constant Pressure System

Torque

- Clamping pressures are automatically achieved without superior control
- High dynamically set clamping pressures due to the “pump function”
- Clamping pressure and speed ratio control independent

Sensor

Pulley 1

Four Edges

Spool Valve

Line Pressure

Valve

Pulley 2

Actuator

Speed Ratio Control

Main Disadvantage:

Constant Flow

Oil supply

- Permanent, constant oil flow required

Pressure Differential

HydraulicControl Unit

Valve

Constant Oil Flow System (PIV)

sF (axial movement of sensorplate)

Characteristics:

- Torque sensor pressure – proportional to torque at the shaft

- Additional “pump function” at high torque gradients

Conventional Torque Sensor(System PIV)

40

p

p

Pcyl1

Pcyl2

CYL1

CYL2

p

p

pTorque

Pump

TORQUE

PUMP

bar

Nm

e

r

u

s

s

200

Torque

20

shift speed ds/dt

e

r

P

100

10

0

0

mm

-1,5

-1

-0,5

0

0,5

1,5

Slide valve travel

Characteristic Curve of Actuator in Conventional PIV Clamping Systems- Clamping Systems

- Control Design for Range Shifts in Autarkic Hybrid

- Expanded Control Layout for Universal Use in Chain Variator Applications

- Summary

Presentation Outline

- Opel Astra Caravan
- 60 kW Diesel engine
- 10 kW electric motor (120V)
- i2-CVT gearbox

Range shift in Autarkic Hybrid raised the need for improved speed ratio control:

Extremely high torque gradients during range shift(CVT engaged vs. disengaged)

Error signal <0,002 required

Driveline of the Autarkic Hybrid

Selection of control parameters:

Absolute value of deviation

u

0

Algebraic sign of deviation

u

Variation of param. (gain scheduling):

Value of control variable

u

CVT Controller, Variable in Structure

FAn

z

=

FAb

- Main disturbancevariables:
- Torque
- Speed Ratio

... lead to a change in required z-ratio for steady state operation

pAb

FAb=pAb.Az

Az

FAn=pAn.Az

Az

pAn

Influence of Disturbance Variables

Improved control system is needed for speed ratio control at SYN (i=0,458) during range shift.

Solution:

Disturbance feedforward (torque)

Extension of the Speed Ratio Controller

The taken measures resulted in a significant improvement of the quality of speed ratio control and reliability of range shifts.

Apply same principles to the CVT controller for universal use:

- Regard to further disturbance variables
- Improved control over the whole spreading range (improvements in quality, efficiency etc.)
- Enable different control strategies: ratio based strategies (e.g. ground speed pto) vs. di/dt control (passenger car / transportation work)

Results and further Aims

- Clamping Systems

- Control Design for Range Shifts in Autarkic Hybrid

- Expanded Control Layout for Universal Use in Chain Variator Applications

- Summary

Presentation Outline

Characteristic z-map

- Further disturbance variables:
- Speed (rotating hydraulic cylinder)
- Spring (basic clamping force)

- Main disturbance variables torque and speed ratio lead to:

Pulley Misalignment, shaft deflection, pulley distortion, …

… change in clamping force ratio

Disturbance Variables

Distrubancefeedforward

z-map

Mathematic

Compensation

E=mc2

setpoint

LinearController

CVT

actualvalue

Extension of the Control Structure

Adaptation

DisturbanceVariables

- Steady state(T, n, manipulated var.)
- …

Distrubancefeedforward

z-map

Mathematic

Compensation

background task (duration ?)

E=mc2

constant task time (e.g. 5ms)

Question: Where to get the z-map from ?

Output of Linear Controller supposed to be Zero in steady state!

setpoint

LinearController

CVT

actualvalue

Adaptation of z-map

Adaptation of the sampling points:

Value of the manipulated variable from linear controllerx weighting factor.

- Weighting functions:
- Gauss
- Cone
- ...

Adaptation Law

Visualization and Discussion of the Adaptation Process

Power demand leads to desired engine speed.

- New engine speed is achieved by changing the CVT’s speed ratio i.
- Change in speed ratio di/dt affects the available torque at the wheel T2!

- Controlling the rate of speed ratio change is favorable

DisturbanceVariables

Distrubancefeedforward

z-map

Mathematic

Compensation

E=mc2

setpoint

di/dt

pdyn

LinearController

f(di/dt,n,geometry)

Modification of the

control structure:

- Delete Feedback Loop

- Stop Adaptation Process

- Replace Controller

setpoint

speed ratio

speed ratio

di/dt

CVT

Control of the Rate ofSpeed Ratio Change di/dt- Axial pulley speedds/dt = f ( di/dt, geometry )

- Damping coefficientD = f ( speed… )

* ü = 1/i

Control of the Rate ofSpeed Ratio Change di/dt- Clamping Systems

- Control Design for Range Shifts in Autarkic Hybrid

- Expanded Control Layout for Universal Use in Chain Variator Applications

- Summary

Presentation Outline

Quality of speed ratio control was significantly improved

- The control structure was implemented using a RCP- system running under Matlab/Simulink (xPCTarget) and is currently running on a test rig
- For use in tractor applications it was also implemented on a typical electronic control unit (C167) both manually and using code generation (dSpaceTargetLink 2.0)
- Gathered z-maps can be used for different purposes (scientific work, onboard diagnostic purposes etc.)
- Further optimization possible (improved di/dt, z-max)

Summary

2004 International Continuously Variable and Hybrid Transmission Congress

September 23-25, 2004

Control and Operating Behavior ofContinuously Variable Chain Transmissions

Roland Mölle

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