Post Processing Dyno Dampers Data using MATLAB

Introduction

The main function of dampers is to reduce the duration and amplitude of vibrations in the mechanical elements by dissipating the vibrational energy of dynamic loads, as well as to maintain vehicle stability and ensure maximum and balanced contact and grip of the tyres with the track.. In the automotive sector, dampers are important components of the vehicle suspension system, as they help to reduce vibrations from the ground to the chassis. This improves and fine-tunes the dynamic behaviour of the vehicle. A proper suspension system is essential to ensure vehicle handling. Using software tools like MATLAB, the goal is to transform and represent the data in a way that is useful for analysis. This study is focused on two models of dampers recognised in the world of cycling, which are valid for use in vehicles of low weight and small dimensions. It is carried out on a test bench designed to evaluate their performance under different conditions. Throughout the text, the test procedures, the analysis of the data obtained and the implications of the results for the design and tuning of dampers to optimise their performance in various usage situations are described.

Damper

In this study, a RockShox Vivid R2C damper and a Cane Creek Kitsuma coil damper were used. These are well-known brands in the cycling world. These models are used in downhill and freeride disciplines.

The RockShox shock has three adjustment valves to adjust the response. It has a generic valve for compression response, and two valves for rebound, low speed and high speed adjustment.

RockShox Vivid R2C

General specs:

• Eye-to-Eye distance: 200 mm.
• Strocke: 57 mm.
• Spring: coil.

Damping tuning:

• External beginning stroke rebound (0-7) clicks.
• Ending stroke rebound (0-19) clicks.
• Low speed compression (0-19) clicks.

Cane Creek Kitsuma

General specs:

• Eye-to-Eye distance: 210 mm.
• Strocke: 55 mm.
• Spring: coil.

Damping tuning:

• Climb switch (0-3) clicks: Descend, Climb, Firm
• Low speed rebound (0-11) clicks.
• Low speed compression (0-11) clicks.
• High speed rebound (0-13) clicks.
• High speed compression (0-13) clicks.

Test

In this test, 9 damper configurations have been examined. Each one corresponds to a different rebound and compression setting configuration. For each test, the machine worked at a frequency of 1 Hz for 6 repetitions.

All the information is imported into the MATLAB software. MATLAB can be used to represent the information in graphs, as well as to calculate, filter and modify parameters.

Figures below shows the displacement and velocity curves against the sampling frequency of the dyno. The blue curve corresponds to the raw values obtained on the test bench, while the red curve corresponds to the result of applying a local regression with weighted linear least squares and a first degree polynomial model. Looking at the values on the velocity curve, there is a considerable difference. This variation and lack of consistency in the data is due to the lack of precision of the test bench.

The dampers suffer a bit of hysteresis, a phenomenon specific to the damper. To get a better reading of the real behavior of the damper, different tests should be performed at different operating frequencies of the dyno. By collecting the maximum points obtained in each test, a curve more accurate to the real one is plotted.

From the data obtained from dyno, force-velocity curves can be plotted for each damper setting configuration. Using matlab algorithms and equations, the information obtained can be filtered and the curves plotted in a form that can be used for analysis and study. The following pictures show the results after each step of the process.

Finally, the damper responses for each configuration tested are plotted in a single figure in the following two pictures:

By isolating the test results on the Cane Creek damper, it is useful to represent the range of adjustment operation that the damper has. From the compression and rebound setting with valves fully closed, to one with valves fully open. Next figure shows the range described. It is a simple way to compare them graphically.

You can read more about the processes and the analysis in this LinkedIn post made.