ADAPTIVE CRUISE CONTROL

Adaptive cruise control is not only useful, but also an important part of the autonomous driving puzzle. However, not all systems operate in the same way. We put three to the test.

We put four systems through gruelling tests to see which works better.

It’s early morning outside Bloemfontein on the N1 and the fog is impenetrable. If I drive too slowly, I risk getting hit from behind; up the speed and I might plough into the car in front. These are the kinds of conditions where adaptive cruise control (ACC) can be a life-saving safety feature and, fortunately, my Ford Kuga long-termer is equipped with this useful tech. I set my speed to 80 km/ h and the following distance to the maximum setting. Not long after, the Kuga slows and, sure enough, two faint rear lights appear in the grey wall ahead.

While ACC was not invented primarily as a safety net, it is clear that the technology is an important building block on the way to fully autonomous driving. We decided to put the systems fitted to three of our long-term vehicles to the test.

THE TECHNOLOGY

Continental not only produces tyres, but is also one of the big ACC systems suppliers – it has sold more than 30 million radar sensors to automotive OEMS.

We recently chatted to Norbert Hammerschmidt, Continental’s head of programme management for radar, about the tech. According to him, because it’s unaffected by adverse weather conditions (including even the thickest fog), the radar sensor is the most common component used in vehicles fitted with ACC from Continental. Radar: Continental radar-sensor tech is now in its fifth generation and it is supplied as a package including a processor and its software. This sensor operates at 77 GHZ and makes use of the Doppler effect to identify objects with a relative speed difference in a 65° ‘V’ facing forward from the sensor, up to a distance of 300 m. Early sensors could not operate at short distances, which meant that ACC systems did not work in stop/start traffic ( usually slower than 30 km/ h). This type of sensor is a more cost-effective alternative and is still used in some applications ( our Ford Kuga long-termer is equipped with it).

Lidar: This is another type of sensor that functions similarly to radar or sonar, bouncing a signal off objects and capturing the resulting reflection, but uses laser light pulses where radar uses a radio signal.

Cameras: Subaru’s innovative Eyesight dual-camera system is the third type of technology used. Our Subaru XV long-termer is equipped with this and it also formed part of our evaluation testing.

Interestingly, in some ACC systems, the radar sensors do not pick up solely the vehicle immediately ahead, but may also ‘see’ the next vehicle in line as the waves move underneath the first car. This information then feeds into the vehicle’s ACC algorithms in case it needs to perform an emergency brake manoeuvre that may cause a chain reaction for the vehicles behind it.

These algorithms are developed to identify target vehicles as well as avoiding ‘ false detections’, such as stationary vehicles next to the road, as well as all the approaching traffic in the opposite lane. Steering angle is also one of the inputs used to determine the vehicle’s trajectory when, for example, you may be following another car round a bend in the road. As the sensor is connected to a vehicle’s CAN bus (the network linking together all the electronic control units, including the engine control unit), it can make use of accelerating and braking to keep fine control on the car’s speed.

Local minimum following distances are specified by relevant authorities in the markets where the vehicle is being sold, as are all the requirements specified by the manufacturer. Supplier companies like Continental therefore use their resident engineers to help calibrate the system for any specific supplier according to all the legal and client requirements.

EVALUATION

Vehicle manufacturers often boast about the peak power output of their engines, or the size of the infotainment screen, but little information is available regarding the specification of a vehicle’s ACC system. That’s why we put three systems to the test and evaluate the differences between them.

THE VEHICLES

Three of our long-termers stood out as the perfect test vehicles, seeing a German ( Audi Q2), an American ( Ford Kuga) and a Japanese ( Subaru XV) manufacturer taking their places in the line-up. The Audi and Ford both employ radar-based systems; the Subaru, on the other hand, utilises the dual-camera setup.