SUSPENSION TUNING MODULE (STM)
DYNATUNE SUSPENSION TUNING MODULE is an ulterior development of the Standard Ride Feature Tool in DYNATUNE R&H and comes as a powerful standalone tool. In STM do exist interactions between Front & Rear Body and Non-Linear damping is more accurately represented by instantaneous Force-Velocity Gradients of the measured damper curve for the complete damper velocity range. Furthermore, by switching from a linear Laplace Transformation to a fully non-linear numerical integration/differentiation of the ride equations, the tool allows a lot more in-depth analysis of the spring/damper/suspension system and provides - with respect to the Standard Ride Tool in DYNATUNE R&H - more detailed results both in the Time, as in the Frequency Domain.
The tool comes with a "Control Section Panel" with convenient Scaling Factors for Spring Rates and Damper Jounce & Rebound Force Velocity Curves, allowing very quick optimization cycles. driven by the DYNATUNE philosophy to achieve maximal results with the absolute minimal amount of input data.
The tool is based on a standard MS EXCEL ® workbook and does use next to the standard workbook functions, also some additional custom written VBA code for the "live" Fast Fourier Transformation in the Frequency Transfer Function Algorithm.
NOTE: DYNATUNE SUSPENSION TUNING MODULE (STM) IS NOT INCLUDED IN ANY OTHER DYNATUNE TOOL. IT COMES AS A STANDALONE TOOL ONLY.
The tool is based on a standard MS EXCEL ® workbook and does use next to the standard workbook functions, also some additional custom written VBA code for the "live" Fast Fourier Transformation in the Frequency Transfer Function Algorithm.
NOTE: DYNATUNE SUSPENSION TUNING MODULE (STM) IS NOT INCLUDED IN ANY OTHER DYNATUNE TOOL. IT COMES AS A STANDALONE TOOL ONLY.
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Straight Out of the Box Damper Setting
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Setup comparison between competitors
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A picture tells more than a Thousand Words
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Analytical MODEL
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The DYNATUNE STM Fully Dynamic Ride Model - which is being used for numerical calculating of the response of the vehicle to a road input signal - exists out of 4 DOF / 3 PART (bicycle) model with a Sprung Body, Unsprung Masses and (linear) Springs & (Non-Linear) Dampers. The Sprung Mass is connected to Front & Rear Spring & Damper systems. Wheels are connected to ground each via a Tire Spring and Tire Damping (which is calculated out of the number for % critical tire damping input parameter).
The differential equations of motion are being solved in the time domain by numerical integration/differentiation with a step size of 0.001 sec. |
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RELEASE 8.1 - SPRiNG INPUT DATA - NON-LiNEAR WHEEL DEFLECTION CURVE
From RELEASE 8.1 onward it's is now possible to specify next to a linear spring rate also a Non-Linear Wheel Force Deflection Curve and - if wanted - also a Non-Linear Motion Ratio Curve as such allowing basically to combine all possible suspension wheel rate combinations.
Beyond the Vertical Wheel Force Deflection Curve the User can also decide to implement a Damper Topmount which is typically found in many OEM applications - for better Ride Comfort and Filtering - to which a Damper Units is attached and as such basically coupling a Damper and a Spring in Series effectively creating an additional Mechanical equivalent of a High Pass Filter.
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DAMPER INPUT DATA
Any operating points outside of the provided data will be linearly extrapolated based on the last two damper data points.
At this point it is worthwhile to mention that the Second Damper Velocity Point (not counting 0) has been defined as the Damper Knee Point defining the typical Transition Point from Low Speed Damping to High Speed Damping Rate. |
Measured Damper Data are to be provided in the standard Force over Damper Velocity format - preferably in the standard speed range of 0 to 1572 mm/s used by almost every damper manufacturers. Different damper velocities however, can be handled without any problems, but the total number of data points is fixed and has to be filled up in the data table as shown below.
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Next to the Damper Data some other Suspension Data have to be provided. Those parameters are the (linear) Spring Rate and the Motion Ratio of the Spring/Damper Unit to the Wheel. Tire Damping Characteristics have to be entered as % Critical Damping according to the usual definitions in Tire Modelling Literature.
VEHICLE INPUT Data
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The most important vehicle data are of course Vehicle Mass, Weight Distribution, Wheelbase and Pitch Inertia, since these parameters define - next to the spring and damper data - for the major part the ride behavior of the vehicle.
The Pitch Inertia of the Sprung Mass is automatically calculated out of a generic x-distance deduction of the Steiner Part of the Unsprung Masses relative to the Center of Gravity of the overall Vehicle Pitch Inertia. |
In order to represent correctly Aerodynamic Vehicles a Constant Static Down-Force can be defined allowing correct Contact Patch Loads.
ROAD INPUT SIGNAL
In RELEASE 8.0 DYNATUNE STM does provide in total 4 different types of road input signals, which are all frequently used in the automotive world to understand and optimize the ride oscillation of a vehicle.
The first 2 Signals have been especially developed for Analysis in the Frequency Domain and the other 2 Signals are commonly used for Analysis in the Time Domain. All signals can be adjusted in Amplitude & Time/Frequency Behavior and if desired the signals can be applied to one or two axles of the Vehicle.
The first 2 Signals have been especially developed for Analysis in the Frequency Domain and the other 2 Signals are commonly used for Analysis in the Time Domain. All signals can be adjusted in Amplitude & Time/Frequency Behavior and if desired the signals can be applied to one or two axles of the Vehicle.
FREQUENCY DOMAIN SIGNALS
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TIME DOMAIN SIGNALS
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2 Input Signals are available:
These signals are typically used on a 4 Poster Hydraulic Rig and can be executed in Bounce Mode or Pitch Mode. Due to the sinusoidal wave content, the results can be post-processed with Fast Fourier Transformations.
The Linear Decaying Sweep Sine Function is representing a road signal with Linear changing Frequency Content (typically from 0Hz to 100Hz) and if desired, changing amplitude. The signal is typically used on a 4 Poster Hydraulic Rig and can be executed in Bounce Mode or Pitch Mode. Due to the sinusoidal wave content, the results can be post-processed with Fast Fourier Transformations.
The Exponential Decaying Sweep Sine Function is representing a more artificial Road Input Signal with Exponentially changing Amplitude Content. The key feature of such a signal is the capability of creating an Input Signal with CONSTANT VELOCITY, allowing to fine-tune especially the Dampers in specific operating ranges.
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2 Input Signals are available:
The Ramp/Step Function represents in effect a smooth 1/4 sinusoidal oscillation/step to a user defined Ramp Height. By setting the Ramp Length and Height & Vehicle Velocity, the Frequency Content of the Ramp is defined and displayed.
The HavSin Function represents a smooth 1/2 sinusoidal oscillation/step to a user defined Height, allowing to investigate the response of the vehicle oscillation to this input. By setting Length and Height of the Object & Vehicle Velocity, the Frequency Content of the ramp is defined and displayed. This particular information will help the user to relate the results from the HavSin Test better to the results from the Sweep Sine Test.
The HavSin Function is particularly useful for KERB Strike Events.
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At this point it is worthwhile to mention that the Exponential Decay Signal does allow the Post Processing of Data for NON-LINEAR Damper settings (Knee-Points - Strongly Different Bump and Rebound Damper Curves. In the previous version of STM, the Fast Fourier Transformation (creating the Transfer Function) was forced to be executed with the averaged Jounce & Rebound Damping, mainly due to the fact that the Linear Decay Signal does contain at Higher Road Signal Input Frequencies more "Energy" than the Exponential Decaying Signal. This new signal has been a major step forward in analyzing non-linear damping and should be used for all Standard Analysis.
CONTROL PANEL WITH SCALING FACTORS
After having entered all Vehicle & Suspension Data and after having selected the various Road Inputs, the user can basically optimize his suspension setting in the "Control Panel" by modifying the Scaling Factors for Front & Rear Spring Rates and Jounce & Rebound Damper Characteristics. The "Live Feedback" of the most important results - all located directly around the control panel - makes it easy to investigate alternatives and work towards the best compromise.
Automatic damper curve GENERATION & optimization feature
Instead of running many manual iterations towards an optimized damper setting, STM does now allow to run a Fully Automatic Loop creating in a First Step a Suitable Damper Curve - for the selected test events - and in a Second Step the Optimized Overall, Bump & Rebound Damping Rates. The User can - if desired - define Start Damping Values for this Process.
In order to Create & Optimize a Damper Curve a proprietary Cost Function - Called STM Performance Index - has been defined which does exist out of a mix of KPI's describing the overall "Performance" of the Vehicle. Expert Users can define a CUSTOM Performance Index with their own Cost Function, allowing maximum Tuning Flexibility.
The Optimization can be executed for Frequency Domain only (4-Poster Test) or include also the Time Domain (Ride Obstacle Event Simulation).
Furthermore, depending on the actual operating conditions of the Vehicle one can "Scale" the Importance of 3 Attributes in the Optimization Dire from 1 to 10 . These 3 Attributes are:
Based on the Scaling Settings the Performance Index will be adapted and allow a Specific Optimization into the desired direction.
Next to the FULL Automatic Loop each of the steps can be executed manually. This does allow to partially optimize Damper Data and execute repeat loops for ultimate In-Depth Fine-Tuning.
In order to Create & Optimize a Damper Curve a proprietary Cost Function - Called STM Performance Index - has been defined which does exist out of a mix of KPI's describing the overall "Performance" of the Vehicle. Expert Users can define a CUSTOM Performance Index with their own Cost Function, allowing maximum Tuning Flexibility.
The Optimization can be executed for Frequency Domain only (4-Poster Test) or include also the Time Domain (Ride Obstacle Event Simulation).
Furthermore, depending on the actual operating conditions of the Vehicle one can "Scale" the Importance of 3 Attributes in the Optimization Dire from 1 to 10 . These 3 Attributes are:
- Platform Control for vehicles that are dominated by Aerodynamics
- Wheel Control for vehicles that are depending on Mechanical Tire Grip
- Driver Comfort & Vertical Accelerations
Based on the Scaling Settings the Performance Index will be adapted and allow a Specific Optimization into the desired direction.
Next to the FULL Automatic Loop each of the steps can be executed manually. This does allow to partially optimize Damper Data and execute repeat loops for ultimate In-Depth Fine-Tuning.
RESULTS
STM does provide 4 Main Area's of Analysis & Results:
- Frequency Domain Analysis & Results
- Time Domain Analysis & Results
- Automatic Damper Generation & Optimization Results
- Classic Analytical & Ride Metrics
FREQUENCY DOMAIN RESULTS
THE SWEEP SINE RESULTS consist out of 3 Main Graphs and several Performance Metrics, all in the Frequency Domain
GRAPHS:
The Frequency Transfer Function describes the relationship between the Road Input Signal and the response of the Wheels & Body to this input. It basically shows, that if the road input at a Frequency of 3 Hz is for example 10mm, the Front Body would react with approximately 10mm x 2 = 20mm vertical displacement and at a Frequency of 10 Hz the Front Body would react with approximately 10mm = 0.3 = 3mm displacement.
The presentation of such a chart - representing the Frequency Domain- is typically in a logarithmic scale, both for x-axis as for y-axis.
This Graph is in fact a Presentation of the Percentage Critical Damping over the Frequency Spectrum. It does show the Percentages of Critical Damping for Wheels and Body for a given Amplitude Input & Excitation Frequency. This allows a good overview of the amount of Damping in the System over the whole operating range.
A graph which displays the "Normalized Dynamic Wheel Load" for a given Excitation Frequency. This is the ratio of dynamic wheel load to static wheel load and when this value does go below -1, the wheel would in real life loose contact with the road. The graph does allow therefore a quick check if the road signal is suited for the vehicle or vice versa, the graph does show at which Excitation Frequency the wheels would start loosing contact with Ground for the given Road Input Signal.
METRICS:
The Key Performance Indicators/Metrics are:
FREQUENCY DOMAIN PERFORMANCE INDEX:
The Performance Index does combine a range of Frequency Domain KPI's into a Cost Function which does allow to be minimized by the Automatic Optimization Procedure.
GRAPHS:
- The Frequency Transfer Function Graph for Body & Wheel Movements.
The Frequency Transfer Function describes the relationship between the Road Input Signal and the response of the Wheels & Body to this input. It basically shows, that if the road input at a Frequency of 3 Hz is for example 10mm, the Front Body would react with approximately 10mm x 2 = 20mm vertical displacement and at a Frequency of 10 Hz the Front Body would react with approximately 10mm = 0.3 = 3mm displacement.
The presentation of such a chart - representing the Frequency Domain- is typically in a logarithmic scale, both for x-axis as for y-axis.
- 0.1 Hz Moving Average Percentage Critical Damping
This Graph is in fact a Presentation of the Percentage Critical Damping over the Frequency Spectrum. It does show the Percentages of Critical Damping for Wheels and Body for a given Amplitude Input & Excitation Frequency. This allows a good overview of the amount of Damping in the System over the whole operating range.
- Dynamic Wheel Load Graph
A graph which displays the "Normalized Dynamic Wheel Load" for a given Excitation Frequency. This is the ratio of dynamic wheel load to static wheel load and when this value does go below -1, the wheel would in real life loose contact with the road. The graph does allow therefore a quick check if the road signal is suited for the vehicle or vice versa, the graph does show at which Excitation Frequency the wheels would start loosing contact with Ground for the given Road Input Signal.
METRICS:
The Key Performance Indicators/Metrics are:
- Dynamic Overshoot & Percentage Critical Damping Factors for Front & Rear Body at Resonance Frequency.
- Dynamic Wheel Load Indicator which does describe how close the Wheel Transfer Function remains to the Value "1".
- Maximum Dynamic / Static Contact Patch Load Ratio.
- Dissipated Energy in Dampers & Tires During The Test.
- Integrated Dynamic Tire Load over Frequency Range.
FREQUENCY DOMAIN PERFORMANCE INDEX:
The Performance Index does combine a range of Frequency Domain KPI's into a Cost Function which does allow to be minimized by the Automatic Optimization Procedure.
Time DOMAIN RESULTS
THE RAMP SINE / HAVSIN INPUT RESULTS consist out of 4 Graphs and several Performance Metrics, all in the Time Domain.
GRAPHS:
METRICS:
BODY:
WHEEL:
TIME DOMAIN PERFORMANCE INDEX:
The Performance Index does combine a range of Time Domain KPI's into a Cost Function which does allow to be minimized by the Automatic Optimization Procedure.
NOTE: In RELEASE 8.0 in the Time Domain Analysis, the Ride Model does permit the wheel to lift off. The car can actually "jump". Performance Metrics are divided into Body and Wheel KPI's. All Body related KPI's describe objective measures for judging/describing the time behavior of the oscillation. The maximum vertical acceleration can be used for trade-offs or to confront comfort aspects of variants.
Last but not least there the tool does contain graphical representation of Accelerations, Velocities and Displacements for the Center of Gravity.
GRAPHS:
- Time Trace of Displacements for Road, Wheel & Body
- Time Trace of Dynamic Contact Patch Load, Spring & Damper Forces
- Damper Operation Points
- Time Trace of Dynamic Spring Deflection & Damper Velocity
METRICS:
BODY:
- 95% Decay Time
- Dynamic Overshoot
- Time to Reach Peak Overshoot
- Maximum Vertical Acceleration
WHEEL:
- Max / Min Contact Patch Load
- Contact Patch Load Integral
- Wheel Lift Time
TIME DOMAIN PERFORMANCE INDEX:
The Performance Index does combine a range of Time Domain KPI's into a Cost Function which does allow to be minimized by the Automatic Optimization Procedure.
NOTE: In RELEASE 8.0 in the Time Domain Analysis, the Ride Model does permit the wheel to lift off. The car can actually "jump". Performance Metrics are divided into Body and Wheel KPI's. All Body related KPI's describe objective measures for judging/describing the time behavior of the oscillation. The maximum vertical acceleration can be used for trade-offs or to confront comfort aspects of variants.
Last but not least there the tool does contain graphical representation of Accelerations, Velocities and Displacements for the Center of Gravity.
DAMPER CURVE GENERATION & OPTIMIZATION RESULTS
As mentioned above the Results of the Damper Generation & Optimization Feature can be devised into 2 Sections:
In Section 1 All Results are displayed for the Newly Created Damper Curve. Step 1 does present the Linear Damper Data and in Step 2 one can evaluate the added Knee-Point Characteristics. In each Step the Performance Index Graph does show "Live" the Progress of the Optimization Process and data will be "Frozen" at the End of the Execution of each Step.
In Section 2 All Results are displayed for the Newly Created & Fully Optimized Damper Curve. Step 3 does present the Results for the Optimized Overall % Critical Damping (Damping Ratio) and in Step 4 one can evaluate the Best Combination of Bump & Rebound Damping. As the Fast Fourier Transformation in the Frequency Domain does primarily consider the Total Amount of Damping in the System the Optimization towards Bump & Rebound Damping is entirely executed in the Time Domain.
Section 2 Data will be generated by Scaling Damper Data Created by Section 1 or Existing Damper Data in the Vehicle 1 Sheet. At the End of the Optimization Process the User can decide whether to set the new Damper Curves as new Base Curves.
CLASSIC ANALYTICAL RESULTS
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RIDE FREQUENCY & DAMPING RESULTS. DYNATUNE STM does provide all the classically known numbers for Front and Rear Ride Frequencies and Percentage Critical Damping Charts for both "Jounce" as "Rebound" damper velocities corrected by motion ratio's and if applicable corrected by scaling factors. Plots are available both for Body as for Wheel damping. On top of that the location of the "Bounce" and "Pitch" Centers are being calculated and in order to optimize the vehicle setup Carpet Plots are provided showing the effects of a wide range of Front & Rear Wheel Rate Combinations on the location of those Centers with respect to the Front Axle of the Vehicle.
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COMPARISON OF RESULTS
The Workbook does contain also a COMPARISON Sheet in which all key Parameters and Graphs for 2 Vehicles are listed allowing an easy back to back comparison of variants. Metrics which are more favorable are high-lighted in Green.
