Synthesis Tools for Vehicle Design

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Synthesis Tools for Vehicle Design
Madhusudan Raghavan GM Technical
Fellow Powertrain Systems Research Lab GM RD
Center Warren, Michigan 48090-9055
McGill University Nov. 3, 2004
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• Synthesis Tools for Vehicle Design
• mechanism types
• wheel motion reqts. ? ISA
• control arm synthesis
• tie-rod/toe-link synthesis
• roll-center height synthesis
• Ackermann steering synthesis
• IMPACT

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Motivation
Need for good kinematics Great ride
handling Why synthesis? Eliminates design
iterations Shortens lead time
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Mechanism Types
5-link rear
short-long arm
short-long arm (goose-neck)
4-link rear
5-bar front
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Mechanism Types
Raghavan, M., An atlas of Linkages for
Independent Suspensions, SAE 911925
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• Synthesis Tools for Vehicle Design
• mechanism types
• wheel motion reqts. ? ISA
• control arm synthesis
• tie-rod/toe-link synthesis
• roll-center height synthesis
• Ackermann steering synthesis
• IMPACT

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Wheel Motion Requirements ? ISA

• Front-view swing arm center
• Side-view swing arm center
• Ride caster
• Ride camber
• Ride steer
• Ride tread
• Ride fore-aft
• Roll caster
• Roll camber
• Roll steer
• Roll tread
• Roll fore-aft

• Requirements generally expressed in terms of
  planar quantities

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Wheel Motion Requirements ? ISA
Front View
Side View
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Wheel Motion Requirements ? ISA
Caster, Camber, Toe, Kingpin InclinationRates
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• Synthesis Tools for Vehicle Design
• mechanism types
• wheel motion reqts. ? ISA
• control arm synthesis
• tie-rod/toe-link synthesis
• roll-center height synthesis
• Ackermann steering synthesis
• IMPACT

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Equations for Various Chains (R-S)
Theoretical Kinematics by O. Bottema, B. Roth
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Equations for Various Chains (S-S)
Theoretical Kinematics by O. Bottema, B. Roth
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Equations for Various Chains (S-P)
Theoretical Kinematics by O. Bottema, B. Roth
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• Synthesis Tools for Vehicle Design
• mechanism types
• wheel motion reqts. ? ISA
• control arm synthesis
• tie-rod/toe-link synthesis
• roll-center height synthesis
• Ackermann steering synthesis
• IMPACT

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Tie-Rod Synthesis for Linear Toe Curve
Constraint Equations

Theoretical Kinematics by O. Bottema, B. Roth
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Tie-Rod Synthesis for Linear Toe Curve
Theoretical Kinematics by O. Bottema, B. Roth
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Tie-Rod Synthesis for Linear Toe Curve
SLA front
5-Link rear
MacPherson Strut front
Theoretical Kinematics by O. Bottema, B. Roth
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• Synthesis Tools for Vehicle Design
• mechanism types
• wheel motion reqts. ? ISA
• control arm synthesis
• tie-rod/toe-link synthesis
• roll-center height synthesis
• Ackermann steering synthesis
• IMPACT

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Control Arm Synthesis for Roll Center Height
Control
Ride-Handling, Comfort
M. Olley
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Roll Center Kinematic Constraints (contd)
M. Olley
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Roll Center Kinematic Constraints (contd)
Differentiating w.r.t. y
Differentiating again w.r.t. y
M. Olley
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Olleys Main Result
Roll Center Fixed to Ground
Roll Center Fixed to Sprung Mass
John Carriere, Milford Proving Grounds
11 Roll Center Motion
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Generalizing Olleys Result

• n1 roll center motion (kinematic)
• Elastokinematic effects

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• Synthesis Tools for Vehicle Design
• mechanism types
• wheel motion reqts. ? ISA
• control arm synthesis
• tie-rod/toe-link synthesis
• roll-center height synthesis
• Ackermann steering synthesis
• IMPACT

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Synthesis for Non-Zero Ackermann Steer
Freudensteins Equation
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Synthesis for Non-Zero Ackermann Steer
Freudensteins Equation
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• Synthesis Tools for Vehicle Design
• mechanism types
• wheel motion reqts. ? ISA
• control arm synthesis
• tie-rod/toe-link synthesis
• roll-center height synthesis
• Ackermann steering synthesis
• IMPACT

28

• Synthesis Tools for Vehicle Design
• mechanism types
• wheel motion reqts. ? ISA
• control arm synthesis
• tie-rod/toe-link synthesis
• roll-center height synthesis
• Ackermann steering synthesis
• IMPACT