Path finding and tracking of clutch brake track chassis based on virtual searchlight

Chassis assembly is one of the core components in mobile agricultural power machinery. A universal chassis can carry the functional tools to realize the various activities in agricultural production. Among them, the oil-operated track chassis are widely used in recent years, due to their low cost, mature technology, sufficient power, high range, and easy maintenance. But their low handling accuracy and severe vibration have posed great challenges to the application of automatic navigation. In this study, the concept of clutch-braked track chassis was proposed as a low-cost agricultural oil-operated track chassis platform. Stronger traction was achieved during steering, compared with differential track chassis vehicles. The RTK-GNSS-based automatic navigation system was built with the STM32F303 as the main controller. The working path of agricultural machines generally consisted of a straight line in the actual operation. The process of tracking was divided into the desired path of the track chassis platform online and the straight line tracking, according to the online point (the online point referred to the sampling point with a lateral deviation less than 3.0 cm, heading deviation less than 2.0°, and the closest distance to the starting position). The kinematics model was established using the transmission and motion of the platform vehicle. A virtual search light pathfinding tracking (VSPT) was proposed to represent the pseudo-code of the VSPT. The fuzzy pre-scanning control was enhanced to search for the target points within the searchlight's field of view in real time. The steering of the track vehicle was controlled to expose the target points within the field of view at all times. In addition, the field of view angle was dynamically adjusted for the tracking oscillation caused by the lateral deviation and speed change. The lateral deviation index and a virtual target point judgment were utilized with a positive proportional relationship of speed. The logical process was designed for the data flow diagram. Direct memory access (DMA) data transfer was used with the idle interrupt and cyclic mode to complete the reception of variable-length byte data. The operation efficiency of the single-chip computer was improved to design the logic flow for the data flow diagram. The improved model was verified to calibrate the relevant parameters by simulation tests. The better navigation was achieved at the chassis forward speed of 0.4 m/s, where the parameters lateral deviation index λ, field-of-view gain k₁, and target gain k₂ were taken as 1/4, 0.005 rad∙m and 6.0 s⁻¹, respectively. Subsequently, the calibrated parameters after simulation were used for the field tests. The results showed that: the average online distance was 1.64 m, while the average lateral and heading deviations were 0.44 cm and 1.57°, respectively, for 6 different initial positions under concrete road conditions. The navigation tests showed that the increasing speed led to a decrease in the navigation accuracy. The appropriate correction of parameters was conducted to maintain better navigation. The average lateral and heading deviations were 0.75 cm and 1.05°, respectively, under 3 speeds, where the average number of corrected deviations was 4.7 times. The number of corrected and heading deviations were reduced under the field dirt road conditions, due to the increasing adhesion coefficient of the dirt road and relatively smooth steering. But the navigation effect was similar under the same parameters in both road conditions. Therefore, the VSPT performed better tracking and adaptability for the control of the clutch-braked track platform. This finding can provide an efficient and stable control scheme for the clutch-braked crawler platforms with navigation algorithms