Dear Mrs. Luchie, dear Sirs,
At our last meeting we were discussing how to deal with the verification of the
establishment of the ESP data bus (pin 6 & 7 ISO 7638). Several members of the group
wanted to achieve a safety improvement between standard systems and an ACV system,
trying to combine this improvement with the stability of EBS data bus.
I tried to put together some thoughts to find a possible solution. I hope that I understood
everything correct in the last meeting; please correct me if I'm wrong.
What safety improvements does ACV already include?
* While coupling and uncoupling electric and pneumatic connectors the driver is no more
in the dangerous area.
* Coiled cables and their risk of braking while turning are eliminated under ACV.
* Automated connections in general are more reliable and fatigue endurable than manual
systems.
* Human factor is considerably reduced.
--> So in my eyes there is no urgent need to reach additional safety improvement
regarding stability of EBS data bus, compared with today's (manual) situation.
How would a verification of the ACV EBS connection be possible?
- Indirect detection of EBS via connection condition
It could be specified that the pneumatics get connected only after the electric pins are
engaged (as it is already included in the dimensions of ISO 13044-2, shown in Annex
A3.2). If the pneumatics are not engaged the trailer brakes don't open. It's then impossible
that the vehicle combination starts to move.
Other methods of indirect detection were analyzed and found less reasonable (e.g. one
electric pin shorter than the rest).
- Direct detection of EBS via data bus condition
The most reliable direct data bus detection for the whole line between the ECUs would be
achieved by the already existing ECU node in the tractor itself, displaying the result on
the truck's dashboard.
Other methods of indirect detection were analyzed and found as less reasonable (e.g.
installing a ECU in ACV, reading EBS data bus, giving somehow a signal to the truck).
But: A demand for a direct detection of EBS causes at least a software modification
inside the truck-EBS-ECU and the dashboard. This means in fact an interdiction of
retrofit, leading to a market entry only via OEM-installation. This would delay ACV and
its safety improvements for a lot of years.
Also a failure indication for EBS-malfunction is rather a general question, independent
from ACV. It should be mandatory the same time as EBS becomes mandatory.
--> So in my eyes the best way to detect connector state is to detect the air pressure in the
trailer via trailer brake condition.
Result
As a consequence of the thoughts above I would propose the following text block to
replace the requested demand on pin verification:
"It shall be made sure that the electric contacts 1-7 acc. to ISO7638:1999 are engaged
before the pneumatic terminals get airtight connected."
To be discussed.
Best regards
i.A. Michael Eiermann
Michael Eiermann
Jost-Werke GmbH
Siemensstraße 2
63263 Neu-Isenburg
Tel.: 06102-295-408
Fax: 06102-295-207