HYDRO-PNEUMATIC SUSPENSION

A small company known for big innovations, Quebec’s Simard Suspensions now offers the DTS electronically-controlled hydro-pneumatic suspension system already proven on trucks and military vehicles from several European manufacturers.

Made by Vehicle Systems Engineering BV in The Netherlands, VSE for short, the first version of the suspension system was launched in 1986. This original HPVS (hydro-pneumatic vehicle suspension) is still in production today. With the advent of electronic controls, VSE updated the system and called the new generation ‘DTS’, which stands for Dynamic Truck and Trailer Suspension. Simard has adapted it for North American use.

The suspension can be spec’d for one or more fixed or steerable axles, with springs, shock-absorbers, roll stabilizer, and axle lift all combined within the DTS hydraulics. You get, among other things, perfect load distribution over all wheels, fully compensated as required, says Simard.

In the name of safety in a dump application, you can get easy levelling, along or square to the drive direction, by way of optional sensors. Height settings are adjustable by remote control.

Axle-load measuring and monitoring is also featured, with an integrated axle lift if needed. In dynamic terms there’s semi-active roll stabilization built in, with something called "super stabilization" as an option. Manual or automatic control of several level and dampening settings is also part of the package.

The DTS suspension can be operated by the driver with a wireless remote control, making it possible to make adjustments of the suspension without getting out of the cab. All functions can be operated via the remote.

There’s also a display on which all relevant information is displayed related to operation, maintenance, failure analysis, and repair. The display can be mounted fixed in the system locker or as a workshop tool mounted in a case. The system can also run on any laptop computer for calibration, first-line fault diagnosis, and for changing parameters. The level of access can be altered for different users.
Optionally the display can be used for operating the suspension system: changing height, return to ride level, levelling etc.

The suspension’s hydraulic cylinders combine to manage axle travel and axle load, and the latter can range from 2 to 16 tons.

Reaction time in a hydraulic suspension is obviously critical, and Simard says the DTS is a champ in the changing conditions it meets. Common reaction times of the micro-electronics are around 4 milliseconds. After about 60 ms the system has adapted to the conditions and the vehicle’s behavior is changed with it. That’s largely because VSE suspension cylinders are designed for low friction, matching an air suspension in reaction times.

Not incidentally, off-road versions of VSE’s suspension are used in special trucks like the Dodge Combat Ram Van for the American military, and the rally trucks of several teams competing in what is arguably the toughest rally in the world, Le Dakar.

DTS isn’t normally an off-the-shelf product, each new application being treated as a complete project. On the first prototypes an extensive test program is run, testing for durability and fatigue, with burst and surge tests included. In the meantime the software is written.