A DAY IN THE LIFE OF A HIGH PERFORMANCE ELECTRIC VEHICLE TEST DRIVER – ALAN CLARK AND DARREN COCKLE, WILLIAMS ADVANCED ENGINEERING TEST DRIVERS

03 Dec 2020

What does it take to be a test driver?

Firstly, you need to be comfortable driving a vehicle to the limit. It’s not all about drifting, but prototype vehicles regardless of performance will start off with no electronic safety systems – no ABS, no traction control, etc. Limit driving helps to understand the performance envelope of a vehicle and how the vehicle is going to react at that point.

Secondly, the ability to almost need to detach yourself from driving, to not think about how to drive.  Instead having the ability to focus only on what you are evaluating, feeling the difference from a change to suspension set-up or a calibration change for example. This a skill that is built up over time.

There are two aspects to the role in our case; leading the development of the vehicle’s characteristics and completing objective tests accurately while ensuring repeatability. For example, lap times should be consistent to ensure a vehicle is experiencing consistent loading throughout a specific stint, or while trying to evaluate or measure the effect of a component change.  

How do you approach developing a high performance electric car?

With EV development, the foundations of chassis tuning don’t change much, but management of the instant torque available and how that is transferred to the wheels is the challenge. It calls for good throttle pedal mapping and ultimately quick reacting traction control systems when needed. What you are always aiming for is to feel you can jump in and drive it away normally, giving driver confidence, even if it is a high performance car.

Then there is the issue of the mass of battery, which could be stacked up high affecting the car’s centre of gravity, or its placement in the vehicle affecting weight distribution and inertias. We get involved at concept level to ensure that the vehicle architecture/layout and systems chosen will help meet defined targets for the vehicle’s characteristics.

With such high voltage systems onboard do you have to have a different approach to safety?

Definitely. When you begin development there is always more nervousness with an EV than with an ICE. The battery system can be 800V. There is a serious danger to life for driver and for those around them if safety precautions aren’t followed.

At WAE, safety strategy starts from the initial design and continues as number one priority throughout development, with all necessary team members having to pass high voltage training courses.

If the car gets an isolation fault there is a procedure in place to follow, including egress procedures to jump clear of the car too. There are more things to go wrong with an EV than an ICE car and during development it is very much laptop driven due to the complexity of the early phase electronics and software.

Can you give an example of the challenges you might face on an EV project?

Let’s imagine we are tasked with electrifying an existing ICE car. Our challenge might be to maintain as much of the car’s original character as possible, keeping the main e-powertrain masses in the same areas as the engine and gearbox so the dynamics don’t suffer.

With these sorts of projects we also need to minimise changes to content from a cost point of view as we are working to the confines of an already established production vehicle.

Once the integration of the EV powertrain is complete, the development of the chassis can be quite straightforward. The challenges come in maximising range and making the car a driver’s car. For instance, managing the regenerative brakes to give good pedal feel.

With an EV that has been designed from the ground up – and where we have had input in this process – it is easier to define the attributes and have fewer compromises on weight distribution and packaging. The major challenges come in the dynamic development of the vehicle, making sure that the responsiveness of the controls – steering, brakes, throttle – all complement each other and give the driver confidence. We’ll come on to this in more detail when we talk about the order of development for an EV.

What is WAE’s role in the new ETCR electric racing series? And where does a test driver fit into this?  

We are responsible for battery system development and integration for the entire ETCR programme, along with the writing and development of battery management software, powertrain control software and strategy. We are also involved in some shakedown activities and development driving.

How will WAE support ETCR over the coming months?    

WAE will be supporting in the integration of the battery and commissioning of the electrical systems. This will involve a short confirmation test to ensure dynamically the complete package is performing. Once initially set-up the teams will join a series of test events at Vallelunga to develop their cars and run through a series of race simulations. WAE will support with electrical and mechanical engineering teams.

WAE is also supplying the battery system for Extreme E. Will you be carrying out a similar testing support role for that electric racing series too?

WAE is responsible for the battery on Extreme E and works closely with Spark Racing Technologies who are developing the off-road chassis for the series. Although we’re supporting technically at test events, the physical test driving for this series is being carried out by off-road professional race drivers.

What is the order of development with an EV prototype?

The first stage is simulation. Before the first chassis is built, simulation will determine the positioning of suspension hard points vehicle handling analysis, powertrain performance, battery sizing and management, traction control, torque vectoring analysis, aerodynamics and thermodynamics. These are all key simulation tools which we have at WAE.

When we get the first dynamic prototype, the typical development order is:

  1. Shakedown – this is to make sure everything is safe, that the car charges correctly and that we have reliability.
  2. Powertrain calibration – make sure torque demands and control are accurate, before throttle pedal mapping to provide driveability at a complete range of speeds.
  3. Chassis system development – vehicle dynamics and brake system development, giving a predictable and stable car to allow development of other vehicle systems such as cooling.
  4. Aerodynamics – refinement of active or passive aero systems.
  5. Range development – reviewing and testing areas to improve efficiency.
  6. Control systems – once we have all of the above, we can then overlay traction control, torque vectoring, mode mapping, etc. We use these control systems to extend the performance envelope of a vehicle.
  7. Vehicle refinement – iterative development process combining suspension tuning, aerodynamics tuning, control systems and powertrain, to deliver a holistic product to a customer’s DNA target.

The key for us is to get the chassis inherently stable so that we have a good foundation to build on. This then gives the driver a more natural driving experience and allows us to use the control systems to extend the performance envelope.

What are the other challenges with an electric car?

NVH (Noise, Vibration and Harshness) is a huge challenge because there isn’t a noisy engine soundtrack to mask certain sounds such as road noise, stone chipping and motor whine. That missing engine noise or exhaust note is part of the ICE experience, giving character and drama with high performance vehicles. The acceleration in a high performance electric car is incredibly exciting – but there is a need to create further driver engagement with visuals or other methods.

EV range is another challenge. At WAE, we draw upon our motorsport experience to develop and introduce lightweight components. Aside from the chosen cell chemistry for the battery, as dynamics engineers we look at reducing rolling resistance by reviewing drag, suspension geometry and tyres. Low rolling resistance tyres usually mean reduced grip on track either from reduced tyre footprint or tyre compound, but of course will benefit range. It will always be a compromise depending on what the vehicle is.

Why would a client come to WAE?

For many reasons:

We also have our own EV powertrain control system software which we have developed over the years, encompassing battery management, powertrain control and performance enhancing systems such as traction control and torque vectoring.

Torque vectoring helps us to quickly control torque to independent wheels, increasing vehicle responsiveness, stability and agility. To demonstrate the control system opportunities, we created a ‘Drift Mode’ for the Nissan Bladeglider where the vehicle could hold a specific slip/drift angle while the driver applied full throttle.

Is there tech transfer from motorsport?

Yes, battery and control system management from Formula E has certainly benefitted the efficiency of roadgoing EVs. Jaguar has seen an up to eight per cent improvement in efficiency of its 90kWh battery for I-PACE as a direct result of learnings on the race track.

What’s the best thing about the job?

Each time behind the wheel is different. When it all clicks and the car feels right, that is an incredible feeling, and knowing that a customer will get to experience what you’ve spent a lot of long hours developing. Then there is what we get to do with a car, driving at the limit with the chance to drive cars at various race tracks, doing lap after lap – who else gets to do that? Plus, we are the first in the world to drive a new prototype – that’s a thrill.