Dynamic drive

Car drivers could get a far sportier feeling out of their vehicles without additional power, weight or fuel consumption, thanks to a dynamics system developed by Prodrive.

The company has developed Active Toe Control, which can adjust the toe angle (the angle of the rear tyres, which affects stability) to different driving styles. It is designed so that a compromise does not have to be made between toe-out, which gives stability at high speeds, and toe-in, which gives a more responsive feel at lower speeds.

Developed over two years, the system can be fitted to economical twist beam axles to provide some of the feel of an expensive multi-link rear suspension.

Matthew Taylor, Prodrive's head of vehicle dynamics, said: 'You've got these two camps — expensive multi-link versus cheap and cheerful twist-beam. We think the technology has phenomenal potential for affecting the way a car behaves. It is strides ahead of electronic stability programme (ESP) and torque vectoring systems because it gives the car authority.'

Hydraulic activators — technology which traditionally could be used to control the toe angle — can prove expensive, and fast actuation uses a lot of power, factors which Taylor said has stalled them from being used.

Prodrive decided to drive an active/static toe using low-cost actuation that, rather than rapidly changing the toe angle to catch a skid or respond to side winds, will respond to ongoing driving style.

'When you use cheap suspensions, you toe the wheels in towards each other for stability when driving at speed on a motorway, but it's dull and boring at low speed,' said Taylor. 'So you point the wheels away from each other and you get agility and response at low speed. But if you go fast, the car feels wayward, even if it's perfectly stable.

'We wanted to maximise the potential of a given suspension system for agility at low speed and maximise its stability sensation at high speed. We're not talking miracles; we're looking at one of the key deficiencies of a twist-beam suspension system and overcoming it with low-cost hardware. We're one step further away from needing to deal with a multilink suspension in order to be competitive.'

Prodrive's solution gives the car toe-in or toe-out as required by running a cheap, low-power, low-torque motor through a significant gearing system. Despite being small, the motor can generate the torque it needs as it can work slowly.

Prodrive is keeping the exact system it uses close to its chest, but it uses intelligent feedback from the car's speed and drivers characteristics.

'You have to make a guess at whether the speed is temporary,' said Taylor. 'If the car's doing 40mph and the driver makes a shift to second gear, briefly goes to 60mph then slows down, we can say that was an overtaking manoeuvre and it would be better to stick with the 40mph strategy rather than trying to keep up with what the car's trying to do. If the car's cruising gently up to speed, then it's likely to be moving into a motorway characteristic and we move into motorway strategy.'

Taylor claimed that all European cars are more capable than the majority of those who drive them, so cars tend to be sold on brand feel and driver enjoyment rather than their actual dynamic capability. Although the way the system will eventually be used remains in the hands of the eventual manufacturer, Taylor said the system could be tailored to the driver or the model of car.

'You could give the driver a switch, or code it into his or her key, so different drivers of the same vehicle could set it to a sportier or more stable feel. Manufacturers could also reduce costs by using the same suspension hardware across different models but changing the way each handles and drives by programming the Active Toe Control to have the agility part of the code hold on longer and leave the stability sensation until later, or vice-versa.'

Active Toe Control has already interested several major suspension manufacturers willing to partner Prodrive to develop the system into production. As it can deliver a sporty feel without additional weight, it can also produce overall fuel savings — a key driver for new vehicle technology.

Although it is early days for the technology, Prodrive admits that its potential has skewed the company's planned research towards similar techniques that economically reduce cost and weight in cars, but still deliver the attributes drivers are looking for.