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Suspension Tuning & Optimization: Kinematic Modelling and Simulation Introduction

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Kinematic Modelling and Simulation Introduction

06.41

00:00 - So far in this section, we've introduced some basic concepts in suspension geometry and kinematics.
00:06 It's easy to see that even though each of these concepts are simple in their own right, when we start combining them all simultaneously, things will quickly become complicated.
00:16 Everything we've covered in this section so far can be simply drawn out on paper and understood.
00:22 But only in the case where the suspension geometry is extremely simple.
00:27 The majority of real life cases, if we want to understand the true kinematics of our suspension, we'll need to make use of some sort of simulation.
00:36 That's not to say that there's no value in sketching out the constructions of instant centres, roll and pitch centres and anti dive calculations for yourself.
00:45 When you're learning them for the first time, this can be very helpful.
00:48 However with all real suspensions operating in three dimensions, we quickly reach the limitations of two dimensional representations of suspension movement.
00:58 Let's take the simple example of a double wishbone suspension.
01:02 So far, we've represented the front view of the wishbones like this where all pivot points sit on a plane at 90° to the direction we're viewing them in.
01:12 In reality, we're unlikely to have this situation.
01:16 The pick up points will be offset to some degree and that means that the plane of each suspension arm is not perpendicular to our view.
01:24 This is what this same suspension looks like in side view.
01:27 Straight away, we can see that we've got a more complex analysis on our hands than the simplified cases we were looking at previously.
01:34 This suspension which is representative of something you'd find typically in a modern car, is moving in a way that we can no longer easily represent in two dimensions.
01:45 Certainly in the case of a multi link suspension there is no easy way to simulate its motion with basic pencil and paper techniques.
01:53 By making use of simulation tools designed specifically for analysing our suspension kinematics, we can quickly build virtual models of our suspension that we can use to understand both how it works and make improvements.
02:06 Another advantage of making use of simulation software is that we can quickly iterate between different configurations with very little work.
02:14 This means that we don't have to physically build new components to test them.
02:18 We can predict how they're likely to behave ahead of time.
02:21 Broadly speaking, the steps involved with the simulation of kinematics are the measurement of your current suspension, input of the measurements into a chosen simulation tool, deciding on the motions you want to simulate, letting the simulation run and finally post processing the results so you can visualise them.
02:40 There are plenty of options out there for simulating your suspension kinematics.
02:43 And what you choose is going to depend on the complexity you want, your experience level and your budget.
02:49 The most basic option is of course, the pencil and paper with all of the limitations that comes with it.
02:55 The next step up would be an online kinematic simulation tool.
02:58 After that, a computer aided design software package, commonly known as CAD.
03:02 And from there it potentially gets more complicated with a spreadsheet based tool and finally a dedicated piece of kinematic simulation software.
03:12 The pencil and paper approach, as we've already discussed is a great way to play around and learn the basics but you'll quickly hit the limitations of using 2D methods for real projects.
03:23 Let's take a look at online kinematic simulators.
03:25 These can be accessed straight from your internet browser, meaning no downloads or software installation is required.
03:32 There are a number of options available but one good example is VSusp which you'll find a link for in the related resources section below this video.
03:40 Here, you can see that we can easily input the relevant values for the suspension and then play with the movements of the chassis or wheels individually.
03:48 We can move in pure heave or roll as well as move one wheel at a time.
03:52 We also have the option to plot different parameters of our choice.
03:56 Again while they're often free and easy to use, they usually use a lot of simplifications.
04:01 So while they can be helpful to start learning with, you'll usually find them limiting for real projects.
04:08 A CAD package, two of the most common being Fusion 360 and SolidWorks, although there are a huge number of options out there, both paid and free.
04:17 These are used for building generic 3D models that aren't intended for kinematic simulation.
04:23 Their flexibility however can be used in order to build a full 3D representation of your suspension and some packages will allow you to plot your resultant suspension kinematics.
04:33 The downside of using CAD for this is that the post processing and visualisation will be time consuming.
04:40 This should only really be considered as an option if you're already making use of this software for other purposes.
04:46 A self made spreadsheet based tool is again another totally generic tool that's not necessarily intended to be used for simulating kinematics.
04:53 But their ability to hold and build up equations, take user inputs and plot results make them a viable option.
05:01 While this will be a cheap or even free option, the downside to using a spreadsheet is that there is a lot of effort involved in building the tool for yourself and it'll require a reasonable amount of experience to get something usable at the end.
05:13 The final option is to use a piece of dedicated software that you'll need to download and install on your computer and in this case, anything worth using will almost certainly have to be paid for.
05:24 In my opinion, a good software tool is something I've always been happy to pay for if it makes my job easier.
05:30 The main advantages of using a full piece of software is the ability to save and load many different iterations of your designs and quickly work through them.
05:39 Crucially, their value often comes at the post processing stage in helping you to plot and visualise the results more quickly and effectively.
05:47 As for the types of inputs we'd be simulating, typically you'd start with pure heave, roll and pitch in approximate magnitudes you expect in your car before moving onto more complex combinations of these inputs.
06:00 Some pieces of software will even allow you to import your measured damper displacement from your logged data so you can replay the kinematics of your car within the software.
06:09 We won't be going through the actual simulation of kinematics in this course as the approach depends so much on which method you choose to go with.
06:16 We hope however that this has given you a starting point for going ahead and seeing what works for you.
06:22 In summary, for all real world simulations, some type of simulation tool has a lot of value in properly understanding your car's kinematics.
06:31 Depending on your skill level and budget, there are plenty of options available out there, each with their own pros and cons.