ESP Made Simple & SOME IMPLICATIONS OF ELECTRONICS

Automotive Manufacturing & Production, Jan, 2000 by Gary S. Vasilash

As automotive supply companies provide sophisticated systems that aid drivers' they are discovering that electronics technology is driving what they do. Here's a look at one technology and one supplier's approach.

One of the products becoming more prevalent on vehicles is ESP, or Electronic Stability Program. One of the leading providers of ESP is Continental Teves (Frankfurt, Germany; Auburn Hills, MI).

As its engineers explain, ESP is about correlating two things, then automatically making the appropriate adjustments. The two things are:

1. Where the driver wants to go (in the immediate sense, not in the context of, say, a navigation system)

2. Where the car happens to be going (as in skidding toward the left when the driver wants to be going to the right)

The two things can be in conflict when, say, ice is encountered on the road surface. The determination of (1) is based on information from a steering wheel angle sensor. The determination of (2) requires inputs from a variety of sensors including, but not limited to, the yaw rate sensor and the lateral acceleration sensor. Realize that these are in addition to the sensors required for other systems that work in concert with ESP, such as antilock brakes (ABS), traction control (TCS), electronic brake power distribution (EBD), and engine drag torque control (EDC).

While ABS and TCS help deal with longitudinal vehicle dynamic issues, ESP adds lateral force considerations to the mix. If either understeering or oversteering conditions are measured (there is a model of the vehicle inside the control computer and if the behavior of the actual vehicle is in conflict with the model, ESP kicks in and begins monitoring at a rate as high as 150 times per second and initiates corrective actions), the ESP system does things that even the best driver can't do (e.g., for understeer it will increase the brake pressure on the inside brakes and decrease the pressure on the outside brakes, if required; it can even adjust the powertrain if it will help bring the car back under control--ESP can actually override the driver's inputs to the brakes or accelerator).

Implications

While Continental Teves (and other companies providing systems of this type) must still have manufacturing skills such as machining, molding, and assembling electronics manufacturing is becoming increasingly critical.

For example, in the case of yaw sensors--which are aerospace technology come to automotive--Continental Teves uses what are essentially two tuning forks made out of a quartz material that are attached at their bottom ends. Fabricating these devices requires a nontraditional skill set, to say nothing of the equipment used to do the job.

The control unit used for the Continental Teves ESP system (encompassing two processors) has 240 kilobytes of memory--which is six times higher than the capability of the processor that Continental Teves was using in 1994. And 1994 represented a 12-fold increase over the control that was used in 1984 for the Mark II, which is said to be the first standard ABS for, passenger cars. Clearly, the same sort of increase in processing power that's evident on desktops everywhere is occurring under the hood.

Helmut Fennel, head of Concept Engineering Controls for Continental Teves, observes, "One thing is obvious, however, from the multitude of electronic components in the chassis area: It makes no sense to continue to develop the different automotive components separately, combining one component after another, often with independent electronic controls." He adds, "A vehicle's electronic components must all be optimized more strongly with a view to their overall system behavior. This all amounts to defining the interaction between the electronic control systems of the drivetrain, display and control elements, comfort components, and chassis functions." This is both a modular and holistic approach to dealing with the various systems that are becoming parts of the standard automobile.

Continental Teves is the world's largest supplier of foundation brakes and is number two in ABS. Each year, it produces some eight million tire and wheel assemblies and 22 million calipers.

What's interesting to note is that in November, 1999, Dr. Stephan Kessel, chairman of the executive board of Continental AG, Continental Teves' parent company, stated, "We are on our way to total chassis management." Which means that it is pursuing the integration of tires and wheels, brakes, wheel suspension, cushioning, damping, vibration control, chassis and stability management electronics, and steering. So look for the company not only to pursue things like its CWS run-flat tire (there is a supporting structure within the tire), but to work on the development of intelligent sensor modules on a single chip that would combine the sensor, processor, and digital I/O ("This would keep down the cost for material, production and installation," Fennel explains).

Bottom line: Even tire and brake companies are being driven by electronic technologies in the 21st century-- and that means now.