ZF Friedrichshafen AG has designed an Innovation Tractor to demonstrate how safety, comfort and efficiency can be enhanced by applying intelligent systems from the passenger car and commercial vehicle segments to off-highway vehicles: The data from these cameras is the basis for different autonomous driver assist systems (DAS), for example automated maneuvering and hitching. Furthermore the powerful ZF TERRA+ generator module and an electric single-wheel drive for trailers and implements provide optimum off-road maneuverability.
The ZF Innovation Tractor is a perfect example for an intelligent mechanical system. Forming the basis of the Innovation Tractor is a standard tractor, upgraded with groundbreaking ZF components and assistance functions. “Our systems expertise enables us to combine established stand-alone systems to create a network, so we can make vehicles see, think and act,” says Dr. Harald Naunheimer, Head of R&D at ZF Friedrichshafen AG.
Tractor with Eyes and Brain
Six cameras mounted on the driver's cab and the hood act as the vehicle's “senses”. A computer analyzes the images from the camera and generates a surround-view image of the tractor's spatial environment. The driver can view this image on a tablet from various perspectives, including a bird's-eye view. The driver can also see an overview of the tractor's movements.
Additional cameras at the rear of the tractor with a seperate data processing unit reduce the risk of accidents in narrow depots, for instance. They are used during automatic hitching and for pedestrian detection while changing implements. With this technology ZF provides its customers in the off-road segment with unprecedented safety and comfort.
Mechatronic systems in the chassis and driveline
An electric steering system, required for automatic driving functions, has been built into the control network and the driveline includes ZF's TERRAMATIC transmission and TERRA+ generator module. This system generation can provide 60 kW of continuous electrical power and serves as the power source for the electrical consumers in the trailer. The trailer features another key innovation; an electrical wheel head with a 3-phase asynchronous motor developed by ZF specifically for use in agricultural and construction machinery.
Additional electrical power
The all-wheel-drive function of the ZF tractor and the electrical boost function from the single-wheel drive on the trailer interact and complement each other delivering optimum Traction Management. The tractor/trailer combination can negotiate muddy or loose ground, and with electrical assistance from the trailer, the tractor successfully tackles uphill gradients of up to 30 percent; terrain normally off-limits for a conventional tractor/trailer set-up. The additional power from the trailer allows a higher payload to be transported with a downsized tractor, ideal for users who tow a fully laden trailer only occasionally.
Two liquid-cooled, high-power, 3-phase asynchronous motors with a downstream transmission stage drive the trailer axle. The electric motors are integrated into the wheel heads, saving space. The nominal voltage is 400 volts, and the system can also be fitted with a wheel brake. The tailor-made drive concept means that forces are transferred more carefully to the field, and trailers of the future would even be able to move autonomously.
Automated driving functions negate manual operations
The SafeRange function allows the driver to leave the vehicle and remotely control the tractor/trailer combination from a safe distance. The Innovation Tractor and trailer are outlined as a bird's eye view on a tablet display and all the relevant driving and steering commands are managed from here. The vehicle components can be moved intuitively on the screen. Dragging the tractor or trailer to the right or left on the screen with a finger causes the actual tractor/trailer combination to maneuver in the chosen direction. When it comes to complicated reversing, the user simply needs to specify the direction in which to steer the trailer and the system calculates and executes all the necessary steering movements. The speed is set by swiping the screen from the center to the edge, across the tractor model or the trailer. The further toward the edge, the faster the tractor/trailer combination moves. The maximum forward speed is 4 km/h, whereas the top reversing speed is limited to 2 km/h. When contact with the screen is removed, the vehicle stops automatically. The same happens if radio contact is lost between the tablet and the Innovation Tractor. Even without a trailer the tractor can be maneuvered by SafeRange.
Maneuvering using the tablet may become more taxing when hitching implements, however, ZF engineers have addressed this issue by introducing the Hitch Detection function to automate the process. The system uses a camera to detect the exact position and angle of the relevant agricultural implement in relation to the tractor by using special targets installed on the trailer or implement. The position is continuously measured during the hitching process and the angle of the steered wheels corrected. The Innovation Tractor maneuvers automatically until it reaches the optimum position for hitching, which is then done by hand.
The Pedestrian Detection function helps ensure the Innovation Tractor works as safely as possible while using the tablet for maneuvering and hitching. The cameras detect pedestrians located between the vehicle and trailer and this information, along with the individual's location, is displayed on the tablet. If the person controlling the tractor fails to respond, the system stops the vehicle. The interrupted hitching process can only be restarted once there is no one between the tractor and trailer.
“True to the ZF innovation concept, the Innovation Tractor brings together in a test prototype all the new functions we believe are practical for agricultural and construction applications,” says Harald Naunheimer. “The focus was on demonstrating what is already possible and technically feasible today, but sets a benchmark on future innovation.”