Development of a Blade Lifting Control Assist System for a Motor Grader

Precise blade control is a central task when automating the operation of motor graders. This paper focuses on the parallel lifting movement using a combination of feedforward and feedback control for controlling the respective lifting cylinders. To this end, the paper first examines the blade mechanism of a motor grader and defines its blade movements. Specifically, the mathematical relationship between the edge points of the blade and the lifting cylinders were obtained using 3D CAD data. Then, the hydraulic behavior of the system was analysed in a test environment with wire encoders that are embedded in the lifting cylinders of the real mechanism. Using the input/output relationship between the 'Desired Stroke' and the 'Actual Stroke' values in different experiments, system identification was applied and the system transfer functions were obtained. Then, a combination of feedforward and feedback control enables moving to desired positions fast while applying precise blade control.