News of August 22, 2001
Jarred, rattled and shaken: Innovations in assembly of the new Audi A4
Ingolstadt - The motto "Vorsprung durch Technik" applies not just to the cars manufactured by Audi, but also to their production. One example is the assembly of the new Audi A4 in Ingolstadt. Audi has invested around DM 130 million in a new assembly shop with the most modern production processes. Among the numerous innovations in A4 assembly are the fully automatic refueling system, the truck lift for logistics handling and the combined shaker and ESP test rig - a world first in car production.
A first because up to now only separate test rig systems have been employed in the automotive sector. The equipment used for the new A4 combines both technologies together in one test rig for the first time. Once its assembly is completed, every Audi A4 must pass through this stationary "torture chamber". It is jarred, rattled and shaken, without moving even a metre from its starting point. AUDI AG has filed for patents on the combined test system. The concept was put into practice by Siemens.
The Electronic Stability Program (ESP) is standard on all Audi models. Contrary to the practice of other car manufacturers, Audi subjects every completed vehicle to an ESP test on a test rig at the end of the production line. Karl Unger, Head of Production Planning - Superstructure/Structure Planning - Assembly at Audi, explains the advantages of active ESP testing: "During the test, transverse-acceleration, longitudinal-acceleration, and yaw-rate sensors are checked by moving a vehicle about its transverse, longitudinal, and yaw axes. The complete test is fully automatic. For one minute the rig runs fixed profiles, and for one minute it runs free. The parameters of the test programme run through a universal proving system (UPS) with communication to the control unit. We achieve reproducible test results with it, and so replace a "double-S" run on the test track that would otherwise be necessary."
This saves a great deal of time. And, as Karl Unger adds: "For logistical reasons, it would hardly be possible at the moment to take every new A4 from production to the test track on the company's site and have the double-S run carried out there." After all, around 1,300 new A4 models come off the Ingolstadt assembly lines every day.
The computer-monitored vibration test incorporates three tracks with three different surfaces. An A4 fresh from the production line is subjected to a rough-track test over cobblestones, bumps and through potholes. During this time, customer-relevant creaks and rattles are assessed which may occur, for example, in the region of the glove box, centre console or instrument panel. Since the vibration test takes place before suspension tuning, the shaking encourages the early settling of body and suspension. The result: a better long-term suspension setup in the subsequent operation.
This is just one example of the numerous innovations that have been incorporated into A4 assembly. Another innovation at Ingolstadt are the two fully automatic refueling systems. The operator only has to open the filling cap by hand; all other operations are taken over by his colleague, the "robot filling-station attendant". First an operator had to carry out a complete filling operation by hand. A mobile data carrier, which can be found on every vehicle, sends the relevant information such as filling quantity, filling speed and fuel grade to the 7-axis robot. The latter detects the filler neck with the aid of a 3D camera system. And how does that work? Two cameras take pictures of the filler neck from different angles, and this information is used to determine its position. The process is based on the stereo-image principle of the human eye.
The computer calculates the displacement of the filler neck from a pre-programmed standard point, moves the filling nozzle into position and starts refueling. The advantage of the 3D camera technique is that different types of vehicle, in this case the A4 saloon and A4 Avant, can be recognised and filled using a single refueling system.
The filling process takes on average one minute. The new car is filled with between five and twenty litres of diesel, petrol or different reference fuels depending how far it has to be driven. After the refueling process the robot uncouples and returns to its start position. Finally the filling parameters are recorded on the data carrier in the vehicle. The movements of the robot are synchronised with the production line conveyor throughout the refueling process.
(August 21, 2001)