Transcript for: Understanding Race Car Dynamics and Handling
Tyres, vehicle dynamics and handling make
up a massive part of the performance of any race car. We're here today at Highlands Motorsport Park
and I've got Blake from University of Canterbury Motorsport to talk a little bit about the approach
to vehicle dynamics they take when designing their cars. Hey Blake so we've got your cars behind you
here, what's the general approach you're taking when you're going to design one of
these cars, what sort of parameters are you starting with and what sort of outputs are
you looking for when you're starting from first principles? - So what we look for at the start is our
extremities, so we're looking for track, wheel base, what kind of, where we want
our tyres, where we want our positioning. Centre of gravity is a consideration. Once you have those parameters, you look
at the track that you're running. So for a Formula Student competition, it's
a lot of tight corners, some open straights but the key is really high lateral acceleration
cornering. So from that point we move into the car,
look at roll centres and you start looking at your stiffnesses so your roll stiffness,
spring stiffness and from there you can kind of start developing some geometries,
working with your camber, caster, king pin inclination and it's kind of like a combined
effort between the chassis team, the powertrain team and packaging all that within the one
group. - The thing I guess with this competition
is the rules are so open, you've got an enormous array of parameters to choose from
and there's lots of different directions you can go. So how much of that is based on building on
previous experience, 'cause you guys build a new car each year right, so how much is
built on previous experience versus say starting with a blank sheet of paper each time? - I think a huge part is the transfer of
knowledge. There's no way that you can design a car
in 3 months without that prior experience. You're definitely building upon previous years,
there's no point redeveloping the wheel, the guys before have done it, done a
fantastic job, it's all about learning off those mistakes. Some years we see issues, some years
we see ways we can improve the car and it's just about taking note of those and
making use of those learnings. - Yeah great so what's the general suspension
layout on one of these cars, what are some of the considerations you make? I can see both of these examples are double
A arms so what are the decisions you're going through when you're layout out the suspension
and deciding where to put the suspension arms, where to put the dampers and how to select
your components? - Yeah so I mean the double A arm is a pretty
standard geometry for the Formula Student competition. It allows a lot of freedom, it's a very reliable
setup. Once you have your rim size selected and you
can know your constraints, it does allow for a bit of freedom with where we're putting
components. Certainly with the 4WD electric vehicle that we
have here, we have a lot more limitations so with that motor mount in there we have to be really
clear of interferences and our clearances between A arms and the moving components
through the range of motion. So from that it limits you to a range of
values that you can use so there's only so much that we can play with and it's just
about optimising those and finding the sweet spot really. - And what is the damper system you're using
on these cars? I can see here this car looks like, I can't see any
coil springs on there whereas this one has different style of damper and it's got some
coil springs on it so what's going on there with the dampers you've got fitted to the car? - Yep sweet so we have the Ohlins spring shocks
over here and we have our air shocks on this car and the air shocks was a bit of a change for us. It was something that's been thought about
for a while, we kind of wanted a shock that was a lot lighter, weight's a serious consideration
for us and so with the air shocks we were able to drop quite a lot of that weight and it still
allowed us that baseline performance that we needed. The spring shocks are really reliable, quite a
linear force whereas the air shocks are a lot more progressive. And it also provides us with a bit more
adjustability so we've got a lot more high and low speed compression and rebound
adjustability. While these do have that adjustability, we've
just got a little bit more freedom there and the weight consideration was definitely part
of that. - And what, as a damper like this, what's it
originally designed for, is it designed exclusively for something like a Formula
Student car or is it based on something else individually? - Yeah so these are actually mountain bike
shocks, downhill bike shocks and we've kind of, we've selected ones that we think are
going to be capable. We do run them at a high PSI, certainly
at the higher end, not something you'd probably, well not what you'd run on a
mountain bike but we've found that they actually perform quite well and they're
quite well suited due to the light weight of the vehicle and the fact that we have 4 of them. But in saying that, they are at their
higher end. - And looking at the cars I can see a little
bit of instrumentation on them, I can see some damper pots, I had a look at the pedal box
before, looks like you've got brake travel. What sort of instrumentation and logging
system have you got in the cars? - So we run quite a few, there's a lot of
linear potentiometers in the car just recording travel and with the shocks we want to know
what sort of loads are going through our tyres and using those shocks we're able to determine
that. With our brake we have, and our accelerators
as well, it's all electrically controlled so we need to know where that pedal's at. In terms of other electronics in there, we also
have the GPS, a 6 axis gimble and all that stuff is useful for interpreting stuff after track
days. - And as far as logging, how do you guys
managed that? Have you guys got something that manages the
data like a data engineer or a race engineer or how do you deal with that when you're
running the car on track? - Yeah so we always have software engineers
on hand, they're always out there with the computers plugging in, just interpreting data
as we go. That live track feedback and it's a really
important component of testing. It's certainly an iterative process, there's always
software updates, there's always software changes and it's definitely having all that recording
equipment in there allows us just to be able to validate what we're doing. - The other thing about, I guess it's really
interesting about developing these sorts of cars, it's happening in a university
environment, you guys have got access to a lot of really high level of equipment and
presumably processing and computer power. How do you use your simulation, how does
that feed into your design, can you talk us through that proccess? - Yeah well we're very fortunate to be in the
university environment and have the resources we have available. Obviously validation's a huge component,
it's something that's often quite overlooked. When you're considering the static events of
the Formula Student competition, validation in the design process is vital. It's incredibly important and we're using a
lot of Ansys, a lot of MATLAB, a lot of Solidworks, a lot of stuff depending on where
we're going, there's a lot of electrical software that's being utilised. A new development for us has been utilising
the Adams Car software. So what we've been doing is creating a full
dynamic model of the vehicle in Adams and that allows us to validate what we're doing
in the suspension side of things so being able to validate suspensions geometries is
really important. It's something that goes back to first
principles and it's really hard to come to a suspension geometry that provides all
the responses that we want but then also provide an improved lap time and it's
really hard to justify that. So having a computer model that we can
put those inputs into and then validate that through MATLAB and also on track data
as well is a really important process. - And when you're building these virtual
models of the cars, is this something that you're able to set the car up virtually and
be pretty confident that that setup you've got in the computer, once you're happy with it
you can take it to the track and it's generally going to work pretty well straight off the
bat in the real car? - Yeah I mean in an ideal world it's always
what we want. In reality there's always going to be issues
and it's just about ironing those out and making sure that you have good procedures
in place to pick up those things. Having those validations as well is really
important. Being sure of what we're doing is actually
realistic in the real world, it's easy to have a computer model that gives you the perfect
answer but if that answer's not actually reliable or not relevant to what we're doing here then
it's useless to us so it's really important to validate things after we've put them on the car
as well. With suspension that's a little bit hard
bit with some of the other things it's a lot easier. With some aero we're testing in wind
tunnels and stuff a lot so validating those Ansys flow simulations in the wind
tunnel is really important for us to justify what we're doing is the right path. - Got you, and one of the things that's
quite striking when you see one of these cars is how tiny the wheels and tyres
are. So from what I understand, there is a pretty
wide range of options, I think tyre companies are making these tyres for Formula Student events. How wide are the options that you can choose
from and what sort of things are feeding into the decision when you're going to design a
car as far as size and width and compound and brand and stuff like that? - Yeah well there's a huge amount that comes
into them, obviously the tyres are a very crucial part of the car. There's not point having a fabulously
powered car if it can't put the power down to the ground. In terms of tyre range, it is extensive,
there's a lot, there's a lot of considerations that come into it, even just the simple path
of designing your own rims or purchasing rims. There's a few things that come into it, without
going too far into depth, like the frontal area is one, how it fits, packaging with our aero. Also packaging internally with, in terms of
these we've got planetary gear boxes within those rims and you've got to fit an
upright and your suspension pickups around that so having clearance is definitely
a consideration, airflow, everything needs to be cool through there so there's a lot that you
have to consider. I think it's just coming down to finding that
optimum for you car and where your design goals are. - And with the tyres, I understand you guys have
got access to some tyre model or some tyre information that you can build your own tyre
models from, can you just talk us a little bit through how that process works with how they
gather that data and how a tyre model is actually useful for you in a simulation? - Yeah so we get our tyre data from the tyre
data consortium and that's something that we can put into Adams, so into our vehicle
dynamics software and having that in there is crucial, what we're looking at with these
vehicle dynamic models is suspension, we're looking at performance on the track but
it's irrelevant if you can't put that power down like I was saying before and with those tyres,
your slip angle is a huge consideration, under certain lateral accelerations. It's something that's really hard to model,
you've got a highly non linear scenario and to model that by hand is damn near
impossible so having those models in place and being able to put, effectively the data
from the tyres we have on the car into those computer models is incredibly important. - And from what I understand, the way they
test the tyres is essentially a large ram on a big treadmill essentially going down and
loading it from side to side and all the different pressures and vertical loads and
stuff. How do you guys turn that raw data into
something useful that you can put into a simulation, are you doing the modelling
yourself as far as the curve fitting and stuff or is that something that's taken care of
for you? - Yeah a lot of that has been done in house
through some UCM boys. There's been a lot of time and thought go
into those. It's definitely a pretty intensive process doing
all those curve fittings. It's a huge process, there's a lot of variables,
a lot of unknowns and I mean that process is something that it's on the leading edge. So the boys have been pretty well hooked into
that and put some serious hours into figuring it all out and validating what we're doing and
comparing data to other resources as well. But that interpretation, a lot of that
interpretation's done through MATLAB. - And one of the really striking differences
I see when I look at these two cars is you've got the combustion car which is obviously
just rear wheel drive. This car has got an electric motor on all 4
wheels so one of the things that's become pretty popular in recent years is torque
vectoring as a strategy. Is that something you guys make use of
in this and what is torque vectoring, how can it help you? - Torque vectoring is huge, especially for a
4WD vehicle. It's something that really sets them apart
so in a high level way, torque vectoring is effectively making the most use of that
vertical force on your tyre. So when you're coming around a corner,
the outside tyres are going to be more highly loaded than the inside tyres so that
means that we can deliver a higher torque to those tyres, utilising that additional
grip and dropping that off on the inside tyres so that we don't have tyre slip and tyre wear. So it's about measuring our vertical loads
on those tyres throughout the track and delivering torque to those tyres based on
that. And also based on slip angle, steering wheel
angle and it's something that we've been working on for a while and it's something that
we haven't quite got right yet, it's an incredibly complex process. We have been developing some basic models
so we've got an open loop system with steering wheel angle. So based on the steering wheel angle
we're loading up our outside tyres more than our inside tyres. And that's just based on a bias. And there's been a bit of work done
as well, just improving that process for future years. Definitely iterative. It's had its kinks and it's something we've
been working out for a while but when we get it right it will certainly be pretty huge. - And what sort of driver feedback, I don't
know if you've been in the position of being able to turn it off and turn it on and back to back
it, what is the driver's feedback, what does it feel like in the car, how much does it improve
the performance for them? - Yeah it's a weird feeling, it's like riding an
e bike. It's powering you out in funny places. But it's something that can be hugely
beneficial and I think once the drivers really start to get used to it, get some hours
in the vehicle, then it can be quite powerful. It's just about changing your driving style
slightly, knowing when that power's going to kick in, how it's going to pull you. Knowing if it's going to oversteer you a little
bit more than in other situations so it's definitely something that you want to have
your drivers in early with and keeping them on board through the process and
definitely driver feedback like you were saying is important. Sometimes you're going to overdo it and
they're going to tell you that and that's important because you need to know that
for the track. You need to know when something's
actually been having a detrimental effect. It is iterative. - Great well that was a really great rundown
of the vehicle dynamics of the cars, thanks very much Blake, that was really
interesting. - Awesome cheers. - Cheers mate. If you liked that video
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