Active Safety – A Little Help From Your Electronic Friends

It started out simple enough. Historians may argue the chronology, but "Active Safety" likely began with the "horn," an effective way to alert the guy ahead of you that you might run into him if he doesn't move. Then someone came up with the idea of something called a "turn signal" to let other drivers know which way you were thinking of going. That led to another great idea, "brake lights" that let the guy behind you know you were slowing down.

Active safety has mushroomed ever since. Much of the safety technology developed over the past 50 years has focused on protecting people in a crash -- reacting to an impact with passive safety technology like seat belts and airbags. The future of active safety seeks to help prevent accidents in ways the inventor of the horn never imagined.

One of the most common active safety systems widely used today is anti-lock braking. Anti-lock braking senses impending wheel lock-up and pulses the brakes many times a second -- faster than most humans could -- allowing drivers to maintain steering control under severe braking conditions. The brake controllers for ABS also enable traction control and dynamic stability systems; the three lie at the heart of most near-term active safety systems. Among these systems are sensors that monitor the angle of the steering wheel, the front wheels and the vehicle itself; the speed at which each wheel is turning; the engine speed; and, in some cases, how hard the driver is hitting the brakes. The electronic components process this information in milliseconds and take corrective action to assist the driver.

This is where we are today, but the technology that will soon be available to consumers will take active safety to another level. The elements of adaptive cruise control and steer-by-wire will be added, and radar might sense impending collisions and either warn the driver or enable the vehicle to take evasive action itself.

With steer-by-wire and active suspension, the vehicle can correct oversteer or understeer with brakes, the engine, steering and perhaps shocks. This is also referred to as integrated chassis control, which uses not just the brakes but also the steering, engine and other systems within the chassis. In essence, the active suspension system analyzes what the driver is asking the vehicle to do and decides how best to achieve that result. In other words, it would be much harder for a driver to lose control of a vehicle if an active safety system could steer to counteract unwanted turning in a braking maneuver. While the system would take input from the driver's controls -- the steering wheel, brake pedal and accelerator pedal -- it could just as easily take commands from outside the vehicle, perhaps from an intelligent highway system.

Suppliers and engineers believe that integrated chassis control could become commonplace in 10 years. The leading edge of this technology is an enhanced handling system called active roll control. The system uses hydraulic input from the steering system to actuate hydraulic cylinders in the front and rear sway bars so they resist leaning when the vehicle turns or follows a curve. Currently, rollover sensors are available to help indicate if a rollover is imminent. The sensor assesses the vehicle's inclination and in conjunction with other inputs, such as vehicle speed and lateral acceleration, warns of extreme inclination or the potential for vehicle rollover.

Also well along the development cycle is adaptive cruise control, also known as intelligent cruise control or smart cruise control, a system that is already in production. One such system features a single radar unit both mid- and long-range capability. The system's processor is contained in the same box as the radar, and the entire unit is hidden behind the front grill. The radar looks forward, while the processor interprets the distance to the vehicle ahead. If the car ahead gets too close (a pre-determined limit entered by the driver), the processor sends a command to the engine controller to slow the engine; and if that's not enough, it sends a command to apply the brakes.

Collision avoidance systems may evolve from adaptive cruise control by adding short-range radar to the front and side. This would work in tandem with a panic brake-assist system currently available. This system measures master-cylinder pressure; if it detects a very rapid application of the brake pedal, it uses the motor pumps from the traction control or dynamic stability control system to build brake pressure at the wheels faster than the driver could manage alone.

Automotive suppliers are looking not only at radar, laser and infrared for collision warning and collision avoidance systems, but also at optical systems - cameras which collect data that is interpreted by a computer rather than driver-displayed. Both optical sensors and angular-rate sensors determine whether there's an obstacle in a vehicle's path. That's the easy part. The challenge becomes understanding the vehicle's intended path, particularly when that path involves a curve in the road. Once the system recognizes that the vehicle is going around a curve, it would be able to determine whether an object is actually in the vehicle's path. An intelligent system that can tell the road is curving will know that a car that looks like it's directly in front is really in another lane.

Increasingly sophisticated advances in active safety will continue to blossom over the next decade, including stop-and-go cruise control, pre-crash sensing, forward collision warning, side and rear blind spot detection and lane change warnings. The more pieces of active safety that are fitted together, the closer the industry comes to being able to turn over control of a car to an on-board or off-board computer in emergency situations, on "smart" high-speed lanes of crowded highways or perhaps even full time during regular driving conditions. Of course, that much automated control could eventually become a "hot potato." The concern is likely to be whether drivers and buyers are ready for it. The fact is, automakers aren't going to spring entire active safety systems on the public all at once. As is already the case, the ingredients will be added gradually, piece by piece.