The electro-hydraulic brake begins requalification testing in Frankfurt.

In early 2003, the endurance testing room at the Frankfurt plant of Continental Teves will begin the requalification testing of our electro-hydraulic brake (EHB). "Requalification testing" is carried out prior to approval being granted for series production and means that all the ABS components of the pilot lot (for the "300 batch) will have been tested to ensure that the customer actually gets all the warranted performance features. As a result, the EHB has to undergo, and pass, a range of tests such as the saline spray test, vibration testing, mechanical shock, bursting pressure and endurance testing. All the component parts of the system are subjected to a functional inspection before and after each test (except the bursting pressure test). Endurance testing simulates the stresses and strains to which a component is subjected throughout the whole life of a vehicle. As Matthias Schildwächter of Customer Sampling Requalification explained to us: This is a whole new ball game for the EHB because in tests like this the electronics have to function as they would normally in a vehicle. So, of course, all the sensors and connections that are present in the vehicle have to be simulated. This will be effected partly by means of the sensors incorporated in the machine itself (steering angle and cluster) and partly by means of electronically simulated signals (this in conjunction with Temic). Since in future tests the electronics will have to perform the same control functions as in a vehicle on the road, the "intelligence of the ECU will be called upon during testing. Matthias Schildwächter again: "The whole test has become more electronic and that means more complex. In the past, for the MK20, 25, 60 and 70 ABS systems, the same control system was used as in actual production, i.e. with fixed control times, and the ECU was simply used as an electronic switch.

The number of brake applications during endurance testing, in the case of "normal" braking, braking with ABS, ASR and ESP for example, would typically be around 300,000 stress cycles in the case of the MK60. Together with the other tests, this gave rise to a total duration of requalification testing of approximately 12 weeks. The stress cycles also included deliberate overloading through higher braking pressures than normal in order to shorten the duration of endurance testing. With the EHB, this deliberate overloading is no longer possible because the new proportional control valves have to be operated at realistic pressures. So a total of more than one million actuations will have to be performed, meaning that endurance testing will now take at least twice the time as it did before. In addition, with the EHB there are now six components to be endurance-tested instead of four, which inevitably means that the new endurance test stands for the EHB will be around one and a half times the size of the present ones.