Rear Multi-link

The multi-link suspension derives its name from the fact that it is made up of three or more links. The rear Multi-link suspension contains five links, and is generally used on higher end luxury cars. The multi-link suspension is derived from the SLA suspension, in that each wishbone (or A-Arm) is replaced with two links. This suspension offers flexibility to the designer, since each link’s location can be determined independently. In this suspension we use the term “link” and “control arm” interchangeably. Traditionally a link is a rigid body with two connections, and a control arm has three connections.



Figure 1. Rear Multi-link Suspension
In conventional designs, the coil spring, shock absorber, and jounce bumper act between the one lower link and chassis. The chosen lower control arm carries most of the load. Additionally, the rear multi-link suspension consists of a toe link, which provides toe control.

Model Use

The rear multi-link suspension system can be used in either a half car or a full vehicle analysis. The default geometry and mass is that of a passenger car or light truck, however the model and data can be revised to reflect any size vehicle, from a large truck to a scale model car.
Note:
  • The wheel body represents the mass and inertia of the tire and the rim.
  • The wheel hub body represents the mass and inertia of other rotating bodies such as a brake rotor, but not the half-shafts if the suspension is driven. The wheel hub and brake rotor have no associated graphics.
  • The wheel and wheel hub parts use the Wheel CG location as the center of gravity.
  • Each body’s Center of Gravity (CG) is estimated from the body’s geometry. The formulas are coded into the point panel and can be seen via the graphical user interface. If more accurate CG locations are available they should be used.
Tip:
  • A wide variety of combinations of suspensions and subsystems can be built using the Assembly Wizard. You are encouraged to build systems and understand the resulting model using the graphical user interface.

    When building a new suspension model, build the model with all of the optional systems (stabilizer bar, etc) included in the model. Immediately turn off the systems using the Project Browser and run an analysis on the base suspension to ensure it solves properly. As data becomes available for the optional systems; activate those systems and populate them with data.

The image below shows the Model Browser view of the systems in a fully populated rear suspension model. The rear multi-link suspension system has five “child” systems.


Figure 2. Browser View of a Rear-Half-Vehicle Model Systems and Subsystems Employing a Multi-link Suspension

Attachments

Attachments determine how the suspension system connects to the rest of the vehicle. The rear multi-link includes attachments for the front lower control arm (LCA), rear lower control arm (LCA), front upper control arm (UCA), rear upper control arm (UCA), and the toe link.
Entity Attaches To
Front and Rear Lower Control Arm Default: Sub-frame

No subframe: Vehicle body

No vehicle body: Ground

Front and Rear Upper Control Arm Default: Vehicle body

No vehicle body: Ground

Toe Link Default: Rear sub-frame

No rear sub-frame: Vehicle body

No vehicle body: Ground

You can also set any attachments using the Attachment Wizard, or by selecting the subsystem in the Model Browser and revising the attachments on the System/Assembly panel.

Points

Points locate the joints and bushings that connect the suspension bodies to one another. The image below shows the principal points for the rear multi-link suspension:


Figure 3. Right Side Principal Points – Rear Multi-link Suspension
Note: The image above omits the left side of the suspension, points locating body centers of mass, and points that locate the optional subsystems (springs, dampers, bump stops and stabilizer bar) for clarity.

Bodies

The rear multi-link suspension is comprised of the bodies shown in the image below:


Figure 4. Right Side Bodies – Rear Multi-link Suspension
Note:

Bushings and Joints

The table below describes the bodies, bushings, and joints for the rear multi-link suspension:
Note: The table omits the joints internal to the strut.
Label Type Body 1 Body 2 Point Notes
Front Lower Ball Joint Spherical Knuckle Front Lower Control Arm Front Lower Ball Joint When the Compliant option is set to No, the compliance for this joint is turned "Off" and behaves as a pure spherical joint.
Rear Lower Ball Joint Spherical Knuckle Rear Lower Control Arm Rear Lower Ball Joint When the Compliant option is set to No, the compliance for this joint is turned "Off" and behaves as a pure spherical joint.
Front Upper Ball Joint Spherical Knuckle Front Upper Control Arm Front Upper Ball Joint When the Compliant option is set to No, the compliance for this joint is turned "Off" and behaves as a pure spherical joint.
Rear Upper Ball Joint Spherical Knuckle Rear Upper Control Arm Rear Upper Ball Joint When the Compliant option is set to No, the compliance for this joint is turned "Off" and behaves as a pure spherical joint.
Wheel Spindle Revolute Wheel Hub Knuckle Wheel Center  
Wheel Hub

Fix Jt

Fixed Joint Wheel Wheel Hub Wheel Center When the Spindle compliance option is set to Yes, the joint type changes to universal.
LCA Front Bush Universal Front Lower Control Arm Subframe, Vehicle Body or Ground Front Lower Control Arm Bush When the Compliant option is set to No, this joint compliance is turned "Off" and behaves as a pure universal joint.
LCA Rear Bush Universal Rear Lower Control Arm Subframe, Vehicle Body or Ground Rear Lower Control Arm Bush When the Compliant option is set to No, this joint compliance is turned "Off" and behaves as a pure universal joint.
UCA Front Bush Universal Front Upper Control Arm Subframe, Vehicle Body or Ground Front Upper Control Arm Bush When the Compliant option is set to No, this joint compliance is turned "Off" and behaves as a pure universal joint.
UCA Rear Bush Universal Rear Upper Control Arm Subframe, Vehicle Body or Ground Rear Upper Control Arm Bush When the Compliant option is set to No, this joint compliance is turned "Off" and behaves as a pure universal joint.
Outer Toe Link Bush Spherical Toe Link Knuckle Outer Toe Link Bush When the Compliant option is set to No, the compliance for this joint is turned "Off" and behaves as a pure spherical joint.
Inner Toe Link Bush Spherical Toe Link Subframe, Vehicle Body or Ground Inner Toe Link Bush When the Compliant option is set to No, this joint compliance is turned "Off" and behaves as a pure universal joint.
The following image shows the location of the joints and bushings in the suspension:


Figure 5. Right Side Joints and Bushings - Rear MacPherson Strut Suspension

Similar Suspensions

Front SLA (1pc LCA)

Front SLA (2pc LCA)

Rear SLA (1pc LCA)

Rear SLA (2pc LCA)

Front Multi-Link