Toyota's recall of its Prius model this week wasn't down to a mechanical fault but a software glitch. Increasingly, computers are in control of our cars, says Paul Horrell, and that is changing our relationship with the open road. In this week's recall of the Toyota Prius, there is no faulty mechanical component. All that's necessary is a quick software update to recalibrate the electrically generated pedal "feel" in its braking system. Which just goes to show how deeply computer control is embedded in today's cars. The Prius is such a famously economical car partly because of its regenerative braking system. When the driver touches the brake pedal, there is no mechanical link to the normal brake discs. In gentle braking, all that happens is the electric generator in the powertrain takes up the load, slowing the car by collecting its kinetic energy and re-charging its battery. COMPUTERS IN A MODERN CAR Climate control unit - allows driver to control temperature with thermostat. Also detects pollutants and shuts off air intake accordingly Alarm and immobiliser - controls security. Engine starts when two codes sent wirelessly via aerial in steering wheel Engine management - controls fuel injection, engine temperature, ignition Wiper control - turns on wipers when it rains; adjusts headlights to counteract heavy loads Automatic transmission - monitors weather, load, incline and position of accelerator to select best gear ABS - controls brakes in emergency and can brake any of four wheels to correct a potential skid Airbag - triggers front and side airbags in event of crash or impact Parking aid - operates warning signal to let driver know how close they are to object behind them

Q&A: Toyota recalls Connected cars 'promise safer roads' Only when the driver brakes moderately hard, or when the battery is charged, do the electronics hand over the braking effort to the wheel discs. For this to occur smoothly, instantly and predictably is an extraordinarily complex piece of control technology. But then, while they don't have this type of "brake by wire", all modern cars do have some electronics in the brakes. The anti-lock braking system (ABS) detects if a wheel has locked up, which causes a skid. ABS corrects this by over-riding the mechanical command from the pedal, easing the braking pressure on the affected wheel. Back in the 1980s, ABS, along with electronically regulated fuel injection, was one of the first pieces of electronics in cars. They used to be a selling point - now they're standard by law. You can't have modern exhaust emission control without fuel injection, and electronic control is nowadays cheaper and more effective than mechanical. As cars have become more economical over the years, the degree of electronic optimisation of the engine and transmission has grown. And on hybrid cars such as the Prius and Honda Insight, it's orders of magnitude more complex again. All the driver does is press the throttle, but the powertrain electronics module independently controls both the petrol engine and the electric motor, and the transmission that blends them, to give the most economical drive at any given moment. Many of today's computerised systems take the load off the driver, for the sake of safety or convenience. High-end cars have radar-based cruise control to vary their speed, keeping them a safe distance from the car in front. "Crash mitigation" uses the radar to sense that the car in front has stopped or there's an obstacle, and can apply the brakes if the driver fails to. Trickle down effect Camera-based "lane-keeping assist" reads the road markings and nudges the steering to keep the car in its motorway lane. And infra-red-based night-vision systems can recognise pedestrians and warn the driver if they're stepping into the car's path. David 'Knight Rider' Hasselhoff, prophet of the computer-car synthesis These systems are beginning (as with the new Audi A8) to link up with the satellite navigation, the better to predict the road ahead and work more smoothly. And history has shown that these gadgets trickle down. In five years or so they'll be available, at least as options, on mid-market hatchbacks. With this level of electronic driver support, won't cars soon be able to drive themselves? In fact car makers have built prototypes that can do just that. But for years into the future they will stop short of selling them. It's too onerous to take legal responsibility away from the driver. Even so, cars will continue to harvest more and more information about the world around them. Rival manufacturers are co-operating to lay down an automotive wifi standard. The aim is that in a few years from now vehicles will be able to set up ad-hoc car-to-car networks. Cars would send and receive their position, direction and speed to neighbouring vehicles. Your car would warn you if a vehicle was around a corner, coming towards you but hidden. If you don't apply the brakes, it could. Soulless automation This type of networking opens more possibilities. Imagine a localised traffic jam in a city - a truck breaks down, say. Cars that get stuck will report their position to neighbouring cars, which will pass it on to a wider pool of vehicles. The navigation systems in vehicles a few streets away will be able to use this info to re-route and avoid the jam. The golden days - some drivers dislike the feel of modern cars So there's no doubt computerisation is making every car more effective as a transport appliance. But that's a pretty dreary fate for the most expensive piece of technology we ever buy. People don't always want that level of soulless automation. They want an individual relationship with their cars. Electronics come to our aid here too. And it goes beyond just having personal preferences for the entertainment and navigation interfaces. Any system that's governed or modulated by electronics can be re-programmed. For most cars today that means the engine response, steering weight, suspension firmness, climate control, even engine sound. It's becoming common for cars to have a 'sport' button on the dashboard. This lets them feel more relaxed in town, but when the driver presses the button, their responses get more urgent on a faster country road. The engineers for different car brands can go further with this, taking the same basic components (because commonality reduces cost) but baking in a particular character of driving feel by calibrating the firmware to suit their brand. In an age where brands are a means of self-expression, that's become a critical part of car marketing. Below is a selection of your comments. Electronic controls can produce wonderful efficiencies and extend capabilities for most automobile drivers. The cautionary notes are these:

- failure mode of these computers or the functions which they control must be such that there are no critical repercussions;

- ultimately control must be available to the driver when extenuating circumstances exist that are not handled by the system as programmed.

Rick Contestabile, Brookings, Oregon, US The real problem is the interconnectivity of the systems in cars. The functions that make up a car used to be separate components, so a fault in the braking system could not possibly affect the engine management. Now it is common for the systems in the car to be made up of a network of components that communicate over data buses in a similar way to office computer systems. As a result a single failure could result in multiple failures if a great deal of care is not taken with the design.

Andy Cole, Ulverston All credit to the folk who manage to design, write and test this complex software which needs to be faultless to ensure the safety of the vehicle which is controlled. Theme for detective drama: programmer modifies braking software on victims car to cause fatal crash at critical point in journey, causing murder with no murder weapon?

Peter Fisk, Doddinghurst, Essex, England By all means refine things like the engine and braking, but when we start having rain-sensing wipers, dark-sensing lights, the car nudging us back into our lane, braking for us... that's too far. There are enough bad drivers without these additional aids to encourage complacency. Look at the number of motorcycle riders who are sceptical at ABS now that more and more bikes are offering it as a feature!

Stephen W, Caerphilly Any more loss of control and you might as well take the train! However, my basic concern is lack of feel; power steering in particular, which is totally unnecessary on all but the largest cars. Most people nowadays drive "digitally" - constantly on and off the accelerator, and steering as if playing a computer game rather than controlling a 3D object with momentum. Such a loss of driving skill and mechanical appreciation, detracts from all the engineering improvements in safety and efficiency. The basic ignorance of how to deal with a sticking pedal is a case in point!

Nick, Rugby



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