A consortium of manufacturers and academics is planning to create safer, more efficient and environmentally-friendly heavy goods vehicles. Its next target is to make sophisticated improvements to HGV steering systems.
CVDC includes Arvin Meritor, Bridgestone, Camcon, Denby Transport, Firestone, Fluid Power Design, FM Engineering, Fruehauf, Haldex, Mekatronika Systems, MIRA, Qinetiq, Shell UK, Tinsley Bridge and Volvo Trucks. ‘The members of the consortium influence the aims and directions of research in vehicle dynamics, and obtain the benefits, including exploitation of intellectual property, for relatively low cost,’ said Dr David Cebon of the engineering department at
A problem on
Some solutions — such as ‘passive steering’ at low speeds — have been suggested to make long vehicles better able to navigate without requiring more road space.
Passive steering comprises mechanical or hydraulic links from the articulation to steer the rear wheels and give a better turning path. But it has drawbacks. Initially it can swing the rear end of the trailer wider than expected, creating a hazard for other road users, pedestrians and street furniture.
And, more importantly, it can reduce stability at high speeds, so it has to be locked off automatically as the truck accelerates. Even the locking off can change the vehicle dynamics suddenly at crucial moments.
So the CVDC is throwing its weight behind active multi-axle steering.’We have devised a strategy for a system that delivers perfect tracking at all speeds, so that the back of the trailer tracks the front of the tractor unit,’ said Cebon. ‘It will have a reduced swept path, tail swing, and tyre scrubbing.’
The researchers have already designed and constructed a demonstrator trailer to test active steering. This was a collaborative effort, with several consortium members supplying components. Features of the system include three electronically controlled, hydraulically actuated and independently steered axles.
There is automatic self-centring and locking of the axles in the event of an emergency, hydraulic failure or system shut-down, and improved axle steering geometry through ‘rack and pinion’-style linkages. It has a DC hydraulic power pack, powered by the tractor unit, with articulation and steering angle sensors and wheel speed transducers on all wheels.
The disc brakes, on all axles, offer the ability to apply different braking forces to each wheel. A distributed control system has also been included.
More work needs to be done to both the hardware and software before it can be commercialised. ‘It is a safety-critical issue,’ said Cebon. ‘It must be safe, perform well and be reliable — all at a reasonable price.’
Safety-critical testing has been boosted by the use of a steering robot from Anthony Best Dynamics to reduce the risks for human drivers during early tests at speed. A motion pack from Oxford Technical Solutions provides position feedback accurate to 20mm.
One element of the project is to apply the technology to long combination vehicles (LCVs), which have more than one articulation. It is known from experiences with Australian road trains and transport elsewhere that some steering movements can become exaggerated as they pass down the trailers, until the final unit snaps round like the flick at the end of a whip. This is an instability that active multi-axle steering could eliminate.
The haulage industry is keen to reduce its impact on the environment and believes the use of fewer, longer, multi-axle trucks will help it achieve its aims.