Control system for a valveless wheel loader

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Energy-efficient drive technology reduces fuel consumption, cutting costs for users. To ensure user acceptance, these drive technologies must maintain the same standards of operability and machine performance.

As part of the joint project run by the German Federal Ministry of Education and Research entitled TEAM (developing energy-efficient drive technologies for mobile machines),various innovative drive technologies were combined in a 24 t wheel loader in the Grüner Radlader (green wheel loader) subproject. These technologies include a hydrostatic, power-split drive as well as a hydraulic hybrid module consisting of a piston-type accumulator and a variable-delivery pump. The bucket drive in the prototype machine was designed as a displacement control system in order to recover energy when the bucket is lowered. Implemented by Hydrive, the control software for the bucket drives activates the hydraulic pumps as well as the necessary command valves at the right time.

Different methods were used to develop the control system. The control system was tested using an in-house software test rig, for example, which involved physical hydraulic and kinematic models of the mast as well as a 3D visualisation of the mast. Measurements were carried out on the real machine and the results used to fine-tune and develop the control system. The machine is currently located at a testing facility in Hirschstein, Germany, where it is being given the final touches before it will undergo intensive testing by different project partners.

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