A visit to the Hannover Commercial Truck show in Germany last year showed just how much development has, and still is taking place in the field of braking. If you're not intimately involved, it can get quite confusing so FleetWatch asked WABCO's Mike Raath to outline what the trends in truck braking are. It makes for interesting reading and FleetWatch thanks Raath for providing us with this input.
Just where we are going in the world of braking has to be the most exciting development in the transport industry! Ever since the first application of air brakes to trucks in 1919, the focus of technical development in this field has gone well beyond the brakes.
For WABCO, it is about integrating intelligence into software and electronics that interface directly with mechanical controls and provide millisecond timing for precise vehicle control. It is about understanding the world of vehicle control, developing products that drive vehicle safety and then testing and re-testing these products to match the expectations of the world's finest truck and bus manufacturers and their customers.
In South Africa, we have seen rapid changes in the transport industry over the last year, ever since ABS (Antilock Braking Systems) was legislated in February 2004. This made it mandatory for all new trailers over 3,5t GVM to have ABS systems fitted (along with automatic slack adjusters) and the ABS must be in working order.
ABS was first introduced on heavy commercial vehicles by WABCO in 1981 - in collaboration with Mercedes Benz - and its concept, components and controllability set a worldwide standard and basis for further evolution. Originally offered as an optional fit, ABS has become mandatory standard equipment on heavy goods and passenger transport vehicles in many international markets due to its ability to control the wheel slip under braking thus preventing the wheels from locking. This control in turn has the effect of maximising adhesion, ensuring stable braking on practically all road surfaces while maintaining steerability, avoiding the risk of yaw and jack-knifing of articulated vehicles and reducing tyre flat spots.
The good news is that with trailer ABS now mandatory in South Africa, coupled with the growth in new truck sales, means there are now many new truck trailer combinations on our roads that are operating to high braking safety levels. We also anticipate that ABS will be legislated for new trucks in the near future. How soon, no one yet knows!
Having said that, however, there are still too many incompatible combinations out there due to transporters trying to marry old and new technology, either via new trucks and old trailers or vice versa, often resulting in non-optimal ABS performance.
Permanent versus stoplight power
In addition, one of the key discussions taking place right now is the ABS permanent power versus stoplight power debate. Permanent power is highly recommended over stoplight power for many reasons, most importantly is that the standard stoplight power coupling cannot handle the current and the net result is the occurrence of too many voltage drops as the electrical system deteriorates.
Also, ABS requires permanent power in order to obtain full benefit of all its system functions i.e. for it to continuously monitor the ABS diagnostics. In the case of stoplight power, the system is only powered up when you apply the brakes. Should you have a problem therefore with the ABS and the system fails, it is only at this point that it will first be detected i.e. when needed the most! When ABS is made mandatory on trucks, it is expected that trailers will be linked directly to permanent power and the combination will be more compatible thus giving maximum safety.
Most of the European OEM trucks sold into South Africa are already fitted as per standard with the dedicated 7 pin, ISO ABS permanent power and 15 pin, ISO taillight plugs. One of the alarming practices taking place in our industry is, however, to remove these plugs and the question to be asked - especially if a new trailer with ABS or EBS is matched to one of these trucks - is: "Why do the suppliers want to downgrade the system - and take away the safety feature from the end-user?
EBS - a major trend
The major trend in braking today has to be the advent of EBS (electronically controlled braking system). This is the logical progression from pneumatic control to controlling the brakes electronically and is a major revision of the total brake system. It is also associated with an increase in fitment of air-operated disc brakes with more efficient braking, increased brake torque and better control of engine brakes and retarders.
When the development of EBS started, there were a few clear and common targets. The major focus was that the electronic signal transmission should be utilised to speed up the response of the brakes and to help eliminate uneven wear problems by controlling brake distribution.
The electronic measurement or calculation of key data like the driver's brake demand, load, wheel-speed, brake wear, trailer brake effect etc. and the processing of all this data in the EBS controller provide a quality of brake control far superior to existing pneumatic systems in terms of response, graduation, accuracy of adhesion utilisation and wear distribution.
In addition, on top of the safety gains with respect to shorter stopping distances and less stress for the driver, there was the expectation that with additional sensors and intelligence, the monitoring of a brake system for faults could be much improved.
Systems for trailers
WABCO EBS for trucks has been around for some time and already we are seeing these systems fitted to many European trucks sold into South Africa. The most recent and exciting launch is the Trailer EBS D Generation system, which now comes standard with RSS (Roll Stability Support). With this system now available, WABCO continues to set standards for the development of braking systems for trailers.
Everyone knows the consequences when semi-trailers become uncontrollable; they roll over and the driver no longer has any chance to save the situation. When a driver perceives the roll-over, it is usually too late to take any counter action. Critical in such driving situations are tight bends with an underestimated radius e.g. off-ramps from highways where lateral acceleration coupled with a high centre of gravity affects the trailer and roll-over may occur.
With this latest innovation, however, WABCO has extended the capabilities of its Trailer Electronic Braking system by adding RSS as an option for drawbar trailers. The system is an industry innovation, for the first time incorporating braking application on all trailer axles to reduce the incidence of drawbar trailer rollover.
The RSS for semi-trailers is an autonomous system which uses the active braking capability of trailer EBS. An enhanced algorithm calculates the lateral acceleration from the wheel speed information and determines, using the load information as well, a measured rollover tendency, which will then lead to activation of side-regulated trailer brakes. Stability is ensured by the load proportioning and ABS functions.
A further enhancement to the future of the transport industry is the launch of the WABCO IVTM system (Integrated Vehicle Tyre Monitoring System). This wireless system regularly checks pressure in all tyres and sends information via radio frequency to an ECU (Electronic Control Unit) which in turn shows the values on a screen in the cab. The driver is therefore warned in good time of slow pressure losses and is able to correct the situation before damage to the tyre occurs. Tyre life is therefore extended and contributes to the overall safety effort.
In summary, we have seen an evolution in braking; from basic air brakes to ABS, EBS, Electronic Stability Control, RSS and already available, Adaptive Cruise Control and Electronically Controlled Air Suspension.
These are just a few examples of how the basic control functions of a vehicle have been developed from simple mechanics to air operated, electronically controlled systems which all serve the same purpose, namely, to increase the active and passive safety of medium and heavy commercial vehicles; to operate them in total compatibility with the environment and other traffic users; and to increase their overall economy in terms of the total cost of ownership. It's all good stuff.