Snow removal on airfields, autonomously
On the site of the former Pferdsfeld airbase, Daimler AG is showing the practical application of automated snow removal operations at airports based on a specific customer requirement.
Under the project name "Automated Airfield Ground Maintenance“ (AAGM), four Mercedes-Benz Arocs tractor units are demonstrating automated airfield clearing in a remote-controlled convoy. The automated technology is particularly beneficial because airfield clearances are difficult to predict and thus tough to plan, especially in winter.
The project was established in close cooperation between Lab1886, the Daimler innovation incubator, Daimler Trucks, and Fraport AG.
Based in Frankfurt/Main, Fraport AG operates one of the world's largest air traffic hubs. The objective of the joint testing activities is the implementation of advanced telematics-based vehicle control technology in areas not accessible to the public. In addition to a comprehensive set of requirements on automated operating machines, Fraport also supplies the snow removal equipment for the test. Among the equipment are four sweeper blowers of the kind already in operation today as semitrailers towed by still conventional Mercedes-Benz tractor units.
The four Arocs test vehicles are equipped with a Remote Truck Interface (RTI) for remotely controlling vehicle functions and exchanging data. All vehicles are fully interlinked via the RTI via telematic systems, all are automated, and all can lead or follow in the vehicle convoy. Specifically, this means that a convoy leader chooses a random unit from a fleet of available semitrailer combinations and defines this as the "lead truck." The leader then uses a control panel to define the number and sequence of the other convoy vehicles, and conducts a pre-operation inspection of the lead vehicle and all other semitrailer combinations. All vehicles are equipped with dual GPS tracking (DGPS) and vehicle-to-vehicle communication (V2V communication) technology.
In addition, the interplay of the RTI and the remote control unit provides a fast and secure data exchange among vehicles. To make this work in real time, a full data exchange between the vehicles and the main control unit of the RTI takes place every 0.1 seconds. The transmissions in the area of V2V communication are based on digital short-range communication (DSRC) technology.
The automated snow removal convoy comprises four vehicles during the test phase and can be expanded to up to 14 units. In addition to other airports that have already signaled interest in such precision work machines for automated runway maintenance, solutions for a wide variety of applications are feasible via the Mercedes-Benz Remote Truck Interface.
"This opens up new possibilities for our customers: high-precision maneuvering procedures of conventional trucks, remotely controlled by the driver outside the cab—for example, positioned at the rear of the vehicle with a perfect view of the maneuvers—are possible, as is unmanned driving in mines, at container terminals, or other closed-off sites," said Martin Zeilinger, Head of Advanced Engineering at Daimler Trucks.
In the case of the demonstration of the Arocs tractor units, the Remote Truck Interface connects the vehicle with the outside world. The control functions for track guidance and operation of the convoy are housed in additional external control units such as the track computer, the operating panel, and the wireless interface. Specifically, the automated Arocs trucks can perform the following functions:
- Control: engine start/stop
- Control: parking brake
- Vehicle lateral control: steering
- Vehicle longitudinal control: engine control (throttling up and down)
- Vehicle longitudinal control: service brake
- Powertrain management: transmission (engage start-off gear, all gear changes, engage neutral)
- Powertrain management: activation and deactivation of the differential locks
- Peripherals: lights including turn indicators, rotating beacons
- Special functions: body control; here: control of the mounted sweeper blower
The RTI control unit allows actuation of all connected vehicle functions via an interface (CAN). Remote control is possible by integrating a wireless interface into the CAN.
"An important component of the RTI control unit is the integrated safety concept. This means that all vehicle functions are monitored. The safety routine is executed as soon as an error occurs. In this way we can ensure that the vehicles can be stopped safely and quickly if needed, and can then simply be operated manually," Zeilinger added.
On the runway, the snow must be cleared to one side over a width of up to 60 m (197 ft) in a single pass. In the case of the Frankfurt Airport, up to 14 vehicles drive in a convoy with the appropriate overlap. This means the snow is "passed on" from the front to the rear from one vehicle to the next. As a result, the snow load increases from vehicle to vehicle, and the performance requirement for the individual snow removal units rises sharply from front to rear. Furthermore, the staggered driving also makes high-precision guidance crucial for the quality of the clearing pattern. All this necessitates highly dissimilar requirements on the performance of each snow removal vehicle.
In the test of the autonomously operating snow removal trucks of Daimler, a predefined snow removal program—under the constant control of a convoy leader—specifies the routes, direction, and speed. The person in the lead vehicle of the removal convoy in charge of the task enjoys relatively good visibility of the swaths to be cleared ahead of the lead and the trailing vehicles.
The swaths to be cleared are predefined with the goal of a high-precision clearing trajectory. This means the routes to be driven are always specified cartographically and are followed with pinpoint precision via a differential GPS system, with accuracy of 3 cm (1.2 in), by the lead vehicle as well as the other convoy vehicles thanks to constant target/actual comparisons.
A high level of flexibility is also needed for snow clearance operations on airfields. For this reason, the convoy leader can take over the routing personally at any time. The convoy leader has the classic controls of steering wheel, accelerator, and brake pedal in each Arocs, and thereby full control over the vehicle. The trailing vehicles then immediately and fully automatically adopt the target paths resulting for them from the change of the route of "vehicle 1."
The prototype convoy from Advance Engineering initially consists of four individual vehicles. The basis is provided by all-wheel-drive Mercedes-Benz Arocs 2045 AS production tractor units from the Grounder product range, equipped with the latest OM 470 LA engine generation certified to Euro VI standards with an output of 315 kW (428 hp) and producing 2100 N·m (1549 lb·ft) of torque. At a brisk speed, most of the mass of snow is thrown to the side by a fully hydraulic, three-section snow plow measuring 8 m (26 ft) in width.
The finishing surface clearing touches are performed by a sweeper, known as a sweeper blower. It is towed as a semitrailer and powered independently of the tractor unit by a six-cylinder engine from Mercedes-Benz installed at the rear of the semitrailer.