U-ABS wins third-party approval for trailer retrofits10 March 2021
The Haldex U-ABS antilock braking system has been approved by French third-party testing body UTAC Ceram for retrofitting on trailers equipped with older generations of braking systems. This approval means that a U-ABS retrofit won’t violate the terms of the trailer’s type approval; modified trailers remain road-legal.
Having been confirmed to be safe and compliant in retrofit, U-ABS is now Haldex’s standard retrofit option for MGX, Modal 24V and Modular systems for existing trailers and semi-trailers. As Haldex’s newest ABS, U-ABS had previously passed EU type approval in its own right and complies with the anti-lock provisions of UNECE Regulation 13. ‘U’ stands for universal; the 24V system is intended for many markets in Asia and South America. In Europe, it is often used for agricultural trailers. It can be used there on road-going trailers too, but only those with a steel suspension.
The tests, which were carried out at a customer site near Strasbourg, France in October 2020, confirmed that U-ABS offers at least equivalent brake performance to the older systems that it replaces. Technicians measured braking performance on a three-axle skeletal semi-trailer originally equipped with a Haldex Modular antilock braking system. For the tests, that system was replaced with the new UABS system in different configurations, including 2S/1M axle-by-axle configuration, 2S/2M side-by-side configuration and 4S/3M configuration compared with the Modal ABS system. Tests for response time (which had to be less than 0.44sec) were done back-to-back, in which the only elements of the pneumatic circuit changed were the ABS valve blocks.
In fact the U-ABS valve internals are very similar to that of previous systems; the only physical change from Modular to U-ABS within the air circuit is a different surrounding casting. That means that a retrofit may only require swapping in a new control unit and reconnecting the existing valve block with new cables to a new ECU, electronic control unit, as an absolute minimum. (However, Haldex also recommends replacing ABS valve blocks more than 10 years old, as solenoid designs have evolved in that time). The essential features of the traditional anti-lock braking set-up with air brake circuit – in which wheel brake actuators are applied through air pressure – remain unchanged in U-ABS. Like its predecessors, wheel speed sensors mounted in brake assemblies monitor for wheel lock-up by comparing the vehicle speed with wheel speed. When a mismatch is detected, the system ECU releases air pressure to reduce the braking force as necessary.
Senior commercial product manager Alexander Kraus observes: “The valve technology is where the energy is coming through compressed air, and enhanced by relay valves. It’s about energy and flow; the physics hasn’t changed. You need a certain amount of air pressure applied to an area to produce a required amount of braking force. Improvements in response time and the performance of the brake come from the intelligence of electronics and software.” In other words, the innovation is on the outside. With U-ABS, Haldex has taken a tried-and-tested pneumatic mechanism and wrapped state-of-the-art electronic control around it. That helps the system communicate with the external world and support innovative auxiliaries.
For example, U-ABS is compatible with Haldex’s latest DIAG+ diagnostic tool that is used for the company’s latest range of EBS (electronic braking systems) required for trailers in Europe. This can track diagnostic trouble codes and read general vehicle information, such as odometer and vehicle ID. In addition, U-ABS offers a ‘reset-to-ride’ automatic levelling function. When the suspension’s pre-set driving position differs from the height of a loading dock, users can manually raise and lower the air suspension for loading. Leaving the suspension in the adjusted position risks damaging the axle and its air suspension mechanism, particularly if lowered to minimum stroke. Reset-to-ride prevents that from happening; even if the driver forgets to reset the ride height and drives off, reset-to-ride monitors wheel speeds; if they exceed a minimum threshold, it automatically resets the suspension.
U-ABS can also connect to a tyre pressure monitoring system, TPMS, to alert the driver and operator of slow punctures and tyre emergencies. As an option, U-ABS can even include trailer stability technology usually only offered with EBS. The so-called Safety Module uses an additional valve to actively apply the brakes on particular wheels to help prevent trailer rollover.