Making the case for lightening quick reflexes

Electric cars are getting very fast. But any driver travelling at 280mph will want to know that the car is doing exactly what it is told, to and that means having highly accurate and dependable sensors.

There are no passengers on board the Toroidion 1 MW electric super car. Every component has to do its job in the most efficient and reliable fashion, while also contributing to the weight saving demands. The goal is to produce an all-electric supercar capable of competing in the Le Mans 24hr race.

Such a challenge throws up many questions, the most obvious being how will an electric car, travelling (theoretically) at up to 280mph, be able to survive for 24 hours without having excessive batteries that would weigh down the car, requiring more power to move it, and therefore bigger batteries. It’s the classic vicious circle.

Toroidion’s solution to this is a unique battery swap system that is as suitable for the Le Mans pit lane as it is for the home user. “There will be only a few more stops than conventional cars are having,” however, said Pasi Pennanen, chief designer and CEO at Toroidion.

The initial target of entering the race has come just a bit too soon for the team. “For 2017 entry there is no room, and time to develop and test the race cars is simply not feasible,” said Pennanen.Now we’re searching for a main sponsor for the 2018 entry, as we’re under discussion with ACO management [Automobile Club de l’Ouest – organiser of the Le Mans race] about possible participation. As Pro Bono we already have a number of excellent top level partners supporting the race team, so once we have found the right main sponsor it will become a success as it will be the first electric Le Mans car entry in history! Think about the commercial value of that!”

The Toroidion car is obviously not the first all electric car, or even electric sports car, but it is one of the first all electric road supercars that has such lofty targets regarding its performance. The consequence is that the design has little room for compromise – power is maximised, weight minimised, and all the while the occupants of the car must be kept safe from danger.

Power comes virtue of the patent-pending direct drive systems, which includes two 200kW front motors and two 300kW rear motors a total of 1MW (1350hp). Harnessing that power in a useful and safe fashion clearly requires components, materials and technology beyond that used in standard production cars.

“As you would expect, a vehicle that can go at speeds up to 450 km/h does need a different kind of performance level.” That is the view of James McKenna, director of product management for electronic sensing, Honeywell Sensing and Productivity Solutions.

Magneto resistance sensor technology from Honeywell provided the 'supercar' sensing performance

Honeywell worked with the Finnish-based Toroidion team to work out how to go about providing the appropriate sensor technology for a supercar. The majority of cars deploy potentiometers, otherwise known as contacting sensors. The problem with these is that the brush - the copper contact that moves between a resistant and a conductive track within the sensor – will wear out with the movement and vibration. “It’s fine for your day-to-day production vehicles, but for supercars, you do need a different level of performance, and that’s where we come in,” said McKenna.

For this application Honeywell turned to magneto-resistance (MR) sensor technology where the sensors are laid out in an array either linearly or circular, and an algorithm calculates the position of the magnetic field, which relates to whatever it is being sensed. It is accurate, with a resolution down to 0.01° for the rotary sensor and 0.04mm for the linear. More importantly it is guaranteed failsafe. “Those are the exact words that Toroidion used,” said McKenna, “they wanted a failsafe solution.”

Failsafe diagnostic

Behind the failsafe operation was the diagnostics built into the sensors. McKenna explained: “When the vehicle is switched on, our sensors have the added capability that they do their own checks. So, for example, if the target magnet isn’t in the right position or is missing, it’ll give that diagnostic signal to the computer in the car that it’s missing.The same for the accelerator pedal.It was an important feature that Toroidion wanted to have in their vehicles – that additional diagnostics when you start the car.”

One of the big advantages of having a failsafe solution, dismissing the argument that says nothing can ever be completely failsafe, is that you only need one. Typically cars will have some level of built in redundancy for their safety critical systems and this would take the form of a second system. However, with no physical contact and hence no wear, and as the sensors are constructed from many individual sensors in an array therefore providing their own degree of redundancy, no back-up system is required for the Honeywell devices, which cuts the weight allocation in half.

Honeywell's SPS Series of linear sensors

It is technology that Honeywell actually developed and have deployed for industries that either require use in harsh environments or demand high accuracy. Agricultural vehicles and heavy duty transportation are examples of the former, high accuracy process valves and robotics, where very accurate positional feedback is essential, is an example of the latter. Both, of course, apply to an electric supercar.

Unlike other supercars that are hybrids rather than all-electric, the power budget is also all important. “Power is of the essence,” claimed McKenna. “These devices are actually pretty low power and you want to really save on the power consumption. Previous super cars and high-performance vehicles that are petrol or hybrids still have a large amount of power available, whereby for Toroidion one of the requirements was that the sensing system would be low power consumption.”

There is, however, a lot of electric power within the confines of the car. One megawatt of power in fact. It sounds sufficiently hostile from an electromagnetic perspective – to be less than ideal for safety critical magnetic sensors – but there are two methods of magnetic sensing. One of them is to sense field strength (Hall Effect sensors), and the other one is to sense field direction – magnetoresistive (MR) sensors.

McKenna said: “In the case of EMI, the effect on the magnetic fields tends to be changes in the field strength rather than changes in the field direction. And this is the advantage in these types of applications in using magneto resistance, it is a lot more robust than sensing field strength.

“We are interested in this application because first of all, it’s a nice thing to be involved in. It may be a little bit of a niche, but going forward in the automotive industry, in a lot of industries in fact, what’s an issue today can become something that is very high volume going forward. And electrical vehicles are certainly the way forward.”

Design challenges

Toroidion certainly seems to be leading this forward progress, but what were the biggest design challenges: lightweighting, power, safety, efficiency?

“All of it,” concluded Pennanen. “The thing is that we have successfully solved them all. The advancements in power to weight ratio we have achieved together with the safety improvements are paramount in scale compared to anything else out there. Now we’re working on the development of the production versions of the car and its unique powertrain components. The biggest challenge, however, has been raising the capital to make all this development work possible as we have been self-funded so far.”

Estimated spec of the Toroidion 1MW Production version

Speed up to 450kph (280mph) 0 – 400kph in 11.0 sec

Power 1000kW

Weight 860kg

Average range 320 miles