DYNATUNE SUSPENSION DESIGN MODULE - KINEMATIC Modeling
DYNATUNE SUSPENSION DESIGN MODULE is a tool that is as completely based on vector algebraic equations which are being used for determining the generic 6 DOF motion equations (3 translations, 3 rotations) of a "free floating body in space". Based on these equations a "free floating body in space" can be fixed to "ground" with 6 separate links, each with spherical joints at both ends. This "knowledge" can be transferred 1 to 1 onto a Suspension Upright/Knuckle which is being held by several suspension Links: By using only 5 of the 6 above mentioned links and by transforming the 6th link into a "spring", the "free floating" body movement of the Upright/Knuckle can be reduced to just 1 Translational Degree of Freedom: (Vertical) Wheel travel. All other movements are restricted by the links.
DYNATUNE SUSPENSION DESIGN MODULE - UNLIMITED DESIGN POSSIBILITIES
The vector algebraic approach permits a new fully flexible approach to suspension modelling. Since the equations are generically based on a 6x6 Matrix that covers the full 3 Dimensional Movement almost any suspension can be modeled by combining and/or (re-) arranging links. The same principle is being applied for the Rocker Linkage in the "Race" Version.
By combining the end of two links one can create A-Arms:
By combining the end of two links one can create A-Arms:
By combining 3 or more Links one can create H-Arms and so on:
DYNATUNE SUSPENSION DESIGN MODULE comes with 3 "Pre-Set" Base Suspensions Configurations that allow to create over 99% of all existing independent suspension types:
- Generic 5 Link: This configuration permits to create most of the existing independent suspensions, that are NOT characterized by a McPherson type Strut. By combining two, three or more links one can create trailing arm suspensions (3 - 5 combined links), double wishbone suspension (max 4 combined links) and various types of multi-link suspensions (max 2 combined links).
- McPherson Strut: This configuration is a "particular" configuration of the Generic 5 Link Suspension where two of the "upper" links combine into an "infinitely" long upper wishbone creating in that manner the equivalent of a slider joint which is typical for any (McPherson) Strut Suspension.
- Integral Link: The 2 above configurations assume that all links are attached on either chassis side or upright side. An Integral Link Suspension however, is characterized by the fact that ONE link is NOT attached to the chassis but to another link, causing a very particular configuration of the GENERIC 5 LINK concept (BMW 5-Series).
DYNATUNE SUSPENSION DESIGN MODULE - EXAMPLE SUSPENSION ARCHITECTURE LIBRARY
The GENERIC approach of the calculation algorithm permits creating a large database of Suspension Configurations from simple Trailing Arm configurations to full blown 5 Link Multi-Link Suspensions. Below a selection of possibly to be created Suspension Types:
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Running Clockwise starting at 12 o'clock:
Center: Generic 5 Link Multi-Link Suspension |
DYNATUNE SUSPENSION DESIGN MODULE - COMPLIANCE & LOADCASE Modeling
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DYNATUNE offers in "EXPERT" Version the Feature of adding COMPLIANCE (Stiffness) to the Suspension Linkage System. Since the tool is based on vector algebraic matrix operations one can extract for each link the correlation between its axial (i.e. in direction of the link orientation) displacement and effect on the Wheel position.
For instance: One can calculate the Contact Patch Lateral Displacement when moving the Track-Rod Link along its center line (similar as in a "steering" movement). Once "knowing" this relationship (which is a "ratio") between those two displacements, the 2 (action/reaction) Forces that are acting in the direction of those two movements are proportional to that same ratio. This implies, that for an Fy (= working in Lateral Contact Patch Displacement direction) the total Link Load on the Track-Rod Centerline can be calculated directly. Extending this concept to all 5 links allows to calculate for any Suspension Linkage Configuration ALL the loads that do act in the center line of the Links when loads are applied at the wheel. |
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Once "knowing" the loads on each link, one can then in a next step by adding a "Link Stiffness" determine the amount of elastic deformation of each link, making the links either "longer" or "shorter" depending on being a Compression or Tension Load acting on that link. Changing the Link Lengths will of course lead to some geometric (=Kinematic) changes and by iterating this process over all the 5 links the "Compliant" Suspension Geometry Position can be determined for that particular load condition.
The Link Stiffness is in real life a Lumped Stiffness Parameter existing out of 3 key local area stiffness values which have to added as "Springs in Series" into one single number. These key local stiffness areas are:
CHASSIS/SUBFRAME ATTACHMENT:
Chassis / Subframe attachment point stiffness (steel, titanium, aluminum or carbon fiber)
LINK ITSELF:
Bushing or Rose Joint stiffness on either side & Link Stiffness in between the "connection" points (steel, titanium, aluminum or carbon fiber)
UPRIGHT/KNUCKLE ATTACHMENT:
Knuckle / Upright attachment point stiffness (steel, titanium, aluminum or carbon fiber)
The Link Stiffness is in real life a Lumped Stiffness Parameter existing out of 3 key local area stiffness values which have to added as "Springs in Series" into one single number. These key local stiffness areas are:
CHASSIS/SUBFRAME ATTACHMENT:
Chassis / Subframe attachment point stiffness (steel, titanium, aluminum or carbon fiber)
LINK ITSELF:
Bushing or Rose Joint stiffness on either side & Link Stiffness in between the "connection" points (steel, titanium, aluminum or carbon fiber)
UPRIGHT/KNUCKLE ATTACHMENT:
Knuckle / Upright attachment point stiffness (steel, titanium, aluminum or carbon fiber)
The above shown tool has been developed and incorporated in the software to calculate / estimate the overall "lumped" Link Stiffness.
NOTE-1: THE INTRODUCED LINK STIFFNESS DOES NOT AFFECT THE PURE KINEMATIC ANALYSIS OF THE SUSPENSION GEOMETRY. ALL COMPLIANCE CHARACTERISTICS ARE CALCULATED "ON TOP" OF THE KINEMATIC RESULTS._
NOTE-2: SINCE THE SUSPENSION TOOL IS BASED ON (TENSION & COMPRESSION) LINKS ANY PARTICULAR BENDING MOMENTS ON THE LINKS ARE NOT BEING CONSIDERED.
NOTE-3: COMPLEX BUSHINGS WITH SIGNIFICANT DIFFERENCES IN AXIAL & RADIAL RATE(S) OR NON-LINEAR STIFFNESS PROGRESSION CURVES CANNOT BE ACCURATELY MODELED WITH THE LINEAR LINK-STIFFNESS CONCEPT AND WILL RESULT IN LESS ACCURATE RESULTS.
NOTE-2: SINCE THE SUSPENSION TOOL IS BASED ON (TENSION & COMPRESSION) LINKS ANY PARTICULAR BENDING MOMENTS ON THE LINKS ARE NOT BEING CONSIDERED.
NOTE-3: COMPLEX BUSHINGS WITH SIGNIFICANT DIFFERENCES IN AXIAL & RADIAL RATE(S) OR NON-LINEAR STIFFNESS PROGRESSION CURVES CANNOT BE ACCURATELY MODELED WITH THE LINEAR LINK-STIFFNESS CONCEPT AND WILL RESULT IN LESS ACCURATE RESULTS.
DYNATUNE SUSPENSION DESIGN MODULE - STRUT BENDING Modeling
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In order to investigate compliant suspension behavior on a Strut Suspension, it is fundamental to implement Strut Bending. The Damper Piston Rod deforms under Vertical, Lateral and Longitudinal wheel loads and causes thus (significant) changes in the kinematic suspension parameters.
In DYNATUNE SUSPENSION DESIGN MODULE "EXPERT" Version the Strut Bending Model consists of an Elementary Beam Element representing the Piston Rod of the Damper with the indicated (automatically calculated) geometric dimensions. The Strut Model comes with a Specific Tool in the software permitting the user to enter additional needed data like Damper Rod Diameter. |