dynamic performance analysis of a full toroidal ivt - a theoretical approach - 2004 international...
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Dynamic Performance Analysis of a Full Toroidal IVT
- a theoretical approach -
2004 International CVT and Hybrid Transmission Congress
CVT2004
R. Fuchs, Y. Hasuda
Koyo Seiko Co. Ltd.
I. James
Torotrak Development Ltd.
1/21
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
Content
• Motivations
• Approach
• Dynamics of the full toroidal variator
• Interaction variator-hydraulic
• Variator system damping
• Conclusion
2/21
Motivations
• IVT dynamic in the frequency domain
• Prediction of system behavior
• System design
• Transmission and driveline control
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
3/21
Approach
InteractionVariator-hydraulic
InteractionVariator-driveline
(engine side)
InteractionVariator-driveline
(vehicle side)
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
4/21
The Full Toroidal Variator
Dynamic model(4 inputs, 4 outputs)
Variator(roller)
i
o
Pe
Pp
Ti
To
xp
dxp/dt
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
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Variator Dynamic: 2 Main Mechanisms
2 mains mechanisms dictates variator stability
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
② Castor angle roller self-alignment. castor angle and disc
rotational direction linked.
① Traction drive power transmission. basic control law for piston
and endload forces.
6/21
Variator Dynamic: Static Response
Soft nonlinearities only due to toroidal geometry Linearization possible
Torque controlPiston position
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
7/21
Variator Stability: Frequency ResponseThe full toroidal variator is a nonlinear MIMO system.
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
8/21
Variator Dynamic: Parametric Study
Dominant parameters
Roller speed, dxp /dt /Fp
100Hz
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
Castor angle, dxp/dt/Fp
• Castor angle Damping
• Endload force Gain• Roller speed Stiffness
9/21
Hydraulic Interaction: Closed-Loop
Mechanism of interactionVariator ratio change produces pressure perturbation.
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
10/21
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
Block diagram
Variator
Hydrauliccircuit Pressure
demand
T
xp, dxp/dtFe, Fp
Hydraulic Interaction: Closed-Loop
11/21
Hydraulic Interaction: 2 Circuit Concepts
Pressure control circuits based on flow control valve and pressure reducing valve
xp
u
Flow control valve (FCV)
Valve spool not sensitive to pressure perturbation.
FCVxp
u
Pressure-reducing valve (PRV)
Valve spool sensitive to pressure perturbation.
PRV
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
12/21
Hydraulic Interaction: Frequency Response
Comparison of frequency response of hydraulic circuit: Fp/dxp/dt
bandwidth
damping
Pressure reducing valve
• Low pass.• Resonance peak.• Load compliance dependent
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
13/21
• Low pass.• Load pressure dependent.
gain
bandwidth
Flow control valve
Hydraulic Interaction: Variator-FCV Circuit
Stable interactionHydraulic damping when variator resonance frequency is higher than hydraulic cut-off frequency
Stability
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
14/21
Closed-loop: Hydraulic damping
Hydraulic Interaction: Variator-PRV Circuit
Valve stability can be guaranteed usingconventional hydraulic design techniques
Stable example
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
Closed-loop: Hydraulic damping
15/21
Hydraulic Interaction: Summary
2 basic circuits
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
Flow control valve circuit• Interaction stable.• Hydraulic damping.• Technically not optimum for control.
Pressure reducing valve• Interaction stable for high load compliance.• Hydraulic damping.• Technically good for control.
16/21
Importance of sub-system designfor system stability.
System Damping: 2 Methods
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
u1
FCV1
Pp1
u2
FCV2
xp
Pp2
Fp1Fp22Ft
Flow control valve (FCV)
PRV1u1u2
PRV2
Pp1Pp2
Fp1Fp22Ft
xp
Pressure-reducing valve (PRV)
• Differential hydraulic (major effect for FCV circuits)• Damping orifices (major effect for PRV circuits)
Damping orifice Damping orifice Damping orifice Damping orifice
17/21
System Damping: FCV Differential Circuit
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
Frequency responses Fp/dxp/dt for null differential pressures
FCV hydraulic
As pressures increases:• Hydraulic gain increases & bandwidth decreases• System damping
18/21
Variator + FCV hydraulic
System Damping: PRV Circuit with Restriction
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
Frequency responses Fp/dxp/dt for different restriction areas
PRV hydraulic Variator + PRV hydraulic
As the area decreases:• Hydraulic gain & damping increase• System damping
19/21
Conclusion
The variator-hydraulic system is stable• For a given variator design, the system performance is determined by the hydraulic circuit.• Additional response tuning possible with control.
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
System design• This analysis is a key step in a theoretical approach of system design.• It should be applied at the design stage to provide a system optimised for fast but well damped response.
20/21
Outlook
Extension to the complete IVT driveline• Complete theoretical investigation including dynamic response of the driveline.
Experimental validation and implication on driveability• Using test rigs and prototype vehicles.
>> Future publications
Performance Analysis of a Full Toroidal IVT- a theoretical approach -
21/21
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