Road Surface Detection using an Optical Sensor for Semi-active Control of Tractor front Axle Suspension = Road Surface Detection using an Optical Sensor for Semi-active Control of Tractor front Axle Suspension

다국어 초록 (Multilingual Abstract)

Research on various suspension systems for agricultural tractor has been carried out for decades. Front axle suspension plays a major role in both increasing the traction force of the tractor and reducing the front vibration of the tractor. In our previous study, a test-rig consisting of a hydraulic-pneumatic front axle suspension system was built to investigate the effect of damping force and flow rate used in the suspension system on the attenuation of the vibration resulting from varying road conditions. This paper reports on the development of a method to identify the bumped road surface using an optical sensor(LiDAR) in advance to control the damping characteristics of the hydraulic front axle suspension system in a more efficient manner. The optical sensor was mounted at the front of the tractor with its angle tilted toward the ground. The roughness of the road surface was quantified by calculating the difference of distance average between each sample. Experimental tests were conducted under two different road conditions (even and bumped roads). The results of bump detection processing methods used in the study showed that the level of roughness and the presence of bump were detectable in a typical range of travelling speeds of tractors when setting the suitable threshold value for the difference of average distance obtained in region of interest (ROI). It was found that the developed road roughness detection system could be used as a look-ahead method to predict a change in the ground condition due to the ability to characterize the ground surface, which could be employed in a semi-active control system that can vary the damping characteristics of the front axle suspension according to varying road conditions. As a result of the control performance experiments using the bump detection system, the vertical acceleration of the vehicle body was reduced when passing the bump, and the steering performance was improved by reducing the axle movement when traveling on even roads, which means that the trade-off problem in passive system is improved in terms of suspension performance.