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DRIVING/TOWING - TOWING

CARAVAN ABS BRAKING AND STABILITY CONTROL
Advanced electronics can help stabilise a swaying combination.

 

In mid-2021 AL-KO upgraded its electronic stability control program to match the advanced safety electronics on towing vehicles in the Australian market – including ABS. The new caravan fitment is known as Tow Assist.

 

 

Outback Travel Australia has been covering the electronic stability control (ESC) systems From AL-KO and US-based Dexter for the past eight years, and we tested two Dexter installations back in 2015 (see reports below).

In the meantime, AL-KO took over Dexter and then Bosch took over AL-KO, making AL-KO and Dexter subsidiaries of Bosch.

The three companies had been collaborating since 2016 on what was originally 2018’s Bosch ABS-enabled TSC and then 2021’s AL-KO Tow Assist, so we’ll take you through the entire development process.

 

 

Trailer stability control

Typical tow vehicles in Australia have had ESC as standard for many years. In general, tow-vehicle stability control monitors the side-to-side motion of the tow vehicle to determine if the trailer is swaying. If the sensor detects yaw that isn’t caused by the driver’s steering inputs, it begins working to control the unwanted motion.

Moderate brake pressure is applied to a single front wheel in an alternating fashion dictated by the severity and direction of the sway. Light brake pressure is applied to the other three wheels, helping reduce vehicle speed in a controlled manner,

Trailer sway can be caused by crosswinds, improper loading of the trailer, incorrect tyre pressure, road conditions or even the ‘wind wave’ from a passing heavy vehicle.

 

However, there was no system that could help stabilise a wayward caravan until 2012, when AL-KO launched its Trailer Control (ATC) system. This consisted of an axle-mounted sensor connected to an electro-mechanical actuator.

Complicating its development was the fact that only in Australia and the USA are caravans equipped with driver-controlled electric brakes. European caravan braking systems rely on overrun input and so trailer stability control that been available over there since the early 2000s wouldn’t work here and in the USA.

ATC monitored trailer stability in a similar manner to tow-vehicle ESC and, if a snaking motion started, the ATC sensor activated the trailer brakes, to slow the combination and eliminate the yawing action of the trailer.

By taking advantage of the ESC system’s ability to manipulate engine output and apply wheel-specific braking, ATC sought to extend the control-enhancing abilities of ESC to the vehicle’s trailer.

AL-KO’s ATC was initially offered in 2012 through new caravan outlets. in January 2013 AL-KO  announced the release of  Electronic Stability Control (ESC) technology as a retrofit product for older caravans.

From February 2013, AL-KO began a progressive rollout of its AL-KO ESC Certified Installer Network, with technicians trained  in the installation of the product. AL-KO ESC was available for existing caravans with AL-KO running gear and brakes on approved suspensions. AL-KO claimed the cost of retrofitting ESC to an existing caravan was $1200 – $1500.

The AL-KO system differed from the tow vehicle’s ESC in that it applied equal brake pressure to all trailer wheels – no trailer ABS.

 

Dexter sway control

 

In the meantime, in mid-2014 Dexter Axle Co, a then subsidiary of AL-KO, launched the Dexter Sway Control system (DSC).

This electronic system used a yaw sensor, similar to the one fitted to the towing vehicle’s ESC. In the event of trailer sway the system applied the brakes on only one side of the trailer, independent of driver action, to correct the sway action.

“This next-generation technology detects trailer sway and applies either the left or right brakes dampening the sway much quicker than other systems that apply brakes on both sides at the same time,” explained Bryan Thursby, Dexter’s vice-president of sales and marketing. We tested the Dexter system in 2015 (see below).

 

AL-KO’s disc brake ATC

The next ATC development came in 2017. While electric brakes are still fitted to the majority of caravans in the market, the growing popularity of caravans with hydraulic disc brakes led to calls for AL-KO to develop ATC to suit this segment.

In response, AL-KO engineers produced an ATC model, combined with an AL-KO IQ7 electro-hydraulic brake actuator, providing smooth braking and a fast response time.

AL-KO ATC became available for caravan manufacturers to fit to new caravans fitted with AL-KO Hydraulic Disc Brakes and AL-KO IQ7 with an ATM of 1250-2000kg for single axle and an ATM of 2000-4000kg for tandem axles.

While all that was going on, Bosch took over both AL-KO and Dexter.

 

Bosch TSC and AL-KO Tow Assist

 

 

In 2018, Bosch Australia launched an innovative trailer safety system featuring trailer-ABS and sway-mitigation technology. It was the first TSC system to combine these two features.

This Trailer Safety Control (TSC) system was for fitment to caravans and trailers equipped with electric brakes and towed by passenger and light commercial vehicles.

“Despite the end of volume passenger car production in Australia in 2017, Bosch Australia’s 200-strong automotive engineering team is busier than ever,” said Gavin Smith, President of Bosch Australia, in 2018.

“Trailer Safety is a great example of how to apply existing capability to an adjacent niche and with global potential.”

Bosch said that in 2016, loss of control accounted for 30 percent of caravan accident claims, with oversteering and fishtailing among the main causes.

The need for a solution to this problem was identified by the Australian Vehicle Safety Systems engineering team, resulting in an R&D project in 2014.

The parent company acknowledged Bosch Australia’s local engineering capability and that led to the establishment of a Bosch Global Centre of Competence for Trailer Safety in Australia in 2015.

The 2018 Bosch TSC system was the first to incorporate trailer ABS and sway mitigation for new caravans and trailers with electric brakes.

Mounted on the trailer, the system comprised an Electronic Control Unit (ECU) with integrated motion sensor and wheel speed sensors. These sensors determined the movement of the trailer and the speed of each individual wheel, respectively.

The ECU was manufactured at Bosch’s production facility in Clayton, Victoria, with the support of DexKo Global, Inc, a global leader in trailer running gear, chassis assemblies and related components,

Although the system was to be offered initially in Australia and the USA, it seems that the USA release came first and the latest iteration of Bosch TSC was launched in Australia as AL-KO Tow Assist.

JB Caravans was the first company to make Tow Assist standard on all its caravans, from August 2021.

How Tow Assist differs from Bosch TSC we’re not sure, but we’ve asked AL-KO for clarification.

 

 

 

Dexter DSC tests

 

dexter sway contorl -dean rOne of the OTA Team members, Dean Reynolds, fitted the Dexter Sway Control system to his 20ft Opal 186 caravan in 2015.

This van had a tandem heavy duty axles and suspension and tares at 2200kg. His towing vehicle was a 2014 Jeep Grand Cherokee Laredo diesel, with eight-speed auto gearbox and air suspension.

Although Dean had a set of weight-distribution bars he didn’t fit them for this extended test.

The route was a three-month journey to the Northern Territory and WA Kimberly area: a 14,000-km round trip from Melbourne.

Dean chose the Dexter system because it worked like his towing vehicle’s electronic stability control, providing automatically-applied, selective braking to both sides – or one side only – of the trailer axles, to control sway.

“I saw the Dexter system first on the Outback Travel Australia website and then checked it out at the 2015 Melbourne Caravan Show,” said Dean Reynolds.

“I liked the fact that it worked like the Jeep’s ESC and that it was the latest in technology: designed, built and backed by one of the biggest axle companies in the world.

“Retro-fitting it to the Opal van was easy enough for the MT&CS crew and it’s been a great investment.”

Like all visitors to the remote northwest area, Dean and wife Anita encountered strong cross-winds at times, along with the wind-rush of oncoming triple- and quad-trailer road trains. The inevitable swaying movement of the van was quickly brought into line, Dean said.

“We didn’t ever need the full capability of the Dexter Sway Control system, but it was very reassuring to know that it was there for us in the event of an emergency,” Dean Reynolds concluded.

In conjunction with this on-road appraisal Allan Whiting caught up with then Dexter dealer, MT&CS during their testing program in Melbourne. It was a very, very interesting morning.

The test rig that MC&CS has been using wasn’t suitable for filming, being a skeletal rig, with a 1.5-tonne block and wires and data sensors all over the place. (Also, I suspect, Dexter didn’t want people to see what’s possible and ‘try this at home’!)

I couldn’t believe the stable behaviour of the non-ESC tow vehicle and DSC-equipped trailer, through what were tight S-bends among trees, on a mixture of surfaces at relatively high speed.

I could have managed this test course at that speed in the solo vehicle, but could not believe it possible with the two-tonne trailer behind. However, it was a doddle.

At one point, during a tight gravel section, I felt the rear end of the tow vehicle break away in a power slide and anticipated a power jack-knife to follow instantly, but the trailer braked left side and right side and pulled the tow vehicle straight.

A typical lane-change manoeuvre at 80km/h was as stable as it would have been without the trailer behind, thanks to the Dexter DSC system. I was convinced.

 

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