Hey All,
I've been thinking recently of all the various decisions that are made on FS cars at a conceptual stage, and the reasoning behind them. Often Rules-of-thumb, trend analysis from competitions, or copying from other teams generate numbers for wheelbase, track, CoG height, tyre choice, steering ratio, etc. etc. and having done all of the above myself (ssh!) I know that I dreaded being asked why I'd chosen them, as I'd have to respond with my most dreaded answer to any question ever (apart from 'ewww, no I will not, get out!'):
'It worked last year'.
I know that two of the answers to generating these nos. are testing and testing, along with iteration from previous years, but given the incredibly short development time of an FSAE car, and the hideously small amount of actual track time that most teams get, along with the high turnover of members, I wonder how much effort goes into simulation tools to try and predict at least an 'ideal' concept/setup for your cars?
I know there are teams out there that have been at this game a lot longer than ours, and who have far greater knowledge of the competition and what it takes to be successful, and so I thought I'd start a post to discuss what people have done and what methods you might use to exploit simulation tools to your advantage when it comes to both developing a good car, and answering those dreaded questions in Design Judging.
Of course, all simulations should be taken with a healthy dose of perspective in terms of what you're simulating, how, and what your results actually mean when compared to a real life car, but I see simulation as a vital tool in a world that is looking to cut cost and development times way beyond a cash-strapped FSAE team.
Since I've graduated I've been lucky enough to work where there is a lot data acquisition and testing going on, particularly through rigs and dynos, but it has always been used to feed simulation accuracy as well as diagnose performance.
I'm particularly interested in laptime simulations, as this is probably where I've had most experience and what I think offers greatest scope for establishing general relationships and sensitivities to what I'd call 'conceptual variables' like the numbers I mentioned above (compared to say FEA, or CFD).
Do people use laptime simulators, like lapSim, RaceSim, piSim or other products (or even written their own) to establish an 'ideal' performance of their car? Have people done much work in terms of varying key parameters of their car to see the effects? Could this be a useful tool for establishing which areas of a car need most attention, in terms of lowering weight or lowering CoG or moving roll centres or whatever you might be interested in?
Obviously as with all simulation garbage in = garbage out, and I imagine most simulations will be specific to a particular car (depending on the amount of work you want to put into your model); so where in the design loop do people use their simulations (i.e. do you review last years car and iterate on that, or at the start of the new car work with a simple model, or simply update the model as you go along)? And how much testing goes into providing accurate inputs to the model (beyond design values, one can use these models to establish sensitivies to installation stiffness, or chassis stiffness and give an informed answer when asked 'how stiff does your chassis need to be?' - this can then be backed up with bench testing, which is cheaper and can provide more detail than track testing)?
Woah, so a bit of a brain dump, but hopefully someone will decipher it and respond with their thoughts! ;-)
B
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