MAN and its partners have developed a slow-moving driverless truck to protect the rear of mobile road works under the umbrella of the aFAS research project. The German government has sponsored it.
Motorway maintenance and road workers are sometimes exposed to high-risk working conditions. Safety vehicles with highly visible warning equipment are designed to minimize these risks. However, these vehicles are still often involved in serious rear-end collisions in motorway bottlenecks. MAN has therefore developed jointly with seven partners a prototype driverless safety truck that follows the machinery used in mobile road works, protecting them from moving traffic.
Two years ago the German Federal Ministry for Economic Affairs and Energy (BMWi) has launched the aFAS project. The aim of the project was to design an automated truck carrying appropriate warning signs that can be operated without a driver. The prototype has been tested in Hessen (Germany), on motorway hard shoulders. The truck is not allowed two run driverless on the road.
The driverless operation component of this initiative presents a significant challenge for the project partners, with particularly high demands being made with respect to the functional safety of the vehicle and the quality of the vehicle technology. The steering and braking systems, sensors, environment detection, and control software must meet strict criteria for safety-related systems in motor vehicles. As far as it’s possible, series components have been used in the project for both the standard control system and the implementation of functional safety features. The environment is surveyed using close-to-production cameras and radar systems, including devices for detecting objects, lanes, and open spaces.
The MAN truck is equipped with an electro-hydraulic steering system from Bosch and an electronic braking system by Wabco. Both systems feature CAN connectivity to communicate with the engine and the automatic transmission system. The required sensors for surveying the environment by ZF/TRW are connected wireless by means of gateways to the in-vehicle networks. Redundant sensors include LGS (lane guard system) camera and sensors of the AEBS (Advanced Emergency Braking System).
The off-the-shelf EBS (Electronic Braking System) by Wabco has been modified. It provides and additional ABS (Anti-lock Braking System), TCS (Traction Control System), and ESC (Electronic Stability Control) functionality. This keeps the truck stable in transversal and longitudinal direction. To monitor and adjust speed the braking system receives via CAN data from other ECUs (electronic control unit). Since its introduction, Wabco’s autonomous emergency braking system features an external braking request (EBR) functionality. Via this interface the braking requests are received and the electronic decides to decelerate the vehicle considering the impacts on the truck’s stability.
The Servotwin electro-hydraulic steering system by Bosch uses also CAN communication – for example, to monitor and control the steering angle of the wheels. All the electronic functions and the control algorithms have been developed in accordance with the ISO 26262 safety standard for road vehicles.
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