Design Challenge - June 2013

Dassault Systèmes - Adjustable Legs

Lumede/Oliver Becker DesignThe DSExcavator (Dassault Systèmes Excavator) was designed for medium to large job sites, for use by general construction and civil engineering companies in sand and gravel quarries. It should therefore be able to safely and easily move on soft and uneven terrain.
Most serious excavator accidents arise when they climb a hill, when mishandling can cause the reversal of the machine. So the DSExcavator features intelligent systems to help maintain stability. Firstly, it can move its centre of gravity throughout the working activity. During travel mode, stability is ensured by the frame’s four independent legs, which are supported by an active hydraulic suspension. The frame is also provided with a central articulation shaft to simplify driving operations by improving the steering angle.

At the heart of this system, an ECU (ESC) constantly monitors the height of each leg to manage the levelling of the main body. The theory of this operation is simple: each leg can move up and down via a couple of dual-effect actuators. When a gyroscopic sensor fixed on the upper frame detects a significant tilt, the ESC software will modify the necessary hydraulic pressure in each circuit, actuating the height of the legs. The actuators that provide the suspension are not in direct contact with the legs, but are connected to a triangular structure that enables both a better course (coef. x2) and a more compact system. This triangle can slide on one of its three corners to enhance the suspension efficiency. This system is highly secure – in the event of a hydraulic failure, the cylinders expand under the excavator’s weight and the vehicle slides smoothly down. Ground clearance ranges from 680mm in its lowest position, to 1,120mm at its maximum height.

During work mode, the four crawlers provide good support on the ground, but the excavator could still be unbalanced by the bucket’s weight and movements. A moving counterweight to the rear therefore provides extra counterbalancing for greater safety. The movement of the counterweight is controlled in real time by the ESC.

To decrease CO2 emissions, the DSExcavator is a hybrid vehicle, with a diesel engine feeding the hydraulic pumps during work modes, and the electric motors inside the crawler hubs when in travel mode.

All mechanical parts, kinematic movement and mechatronic systems of this project have been designed and validated using Dassault Systèmes’ 3DExperience solutions.

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Julien Treillard (M. Eng) is solution technical manager in the DS Industrial Equipment dept, which he joined in 2000. Alexandre Pichkurenko is a solution technical apprentice engineer



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