Controlling wheel loader motion along a desired trajectory

Abstract

Problem. Rigid-frame skid steer front loaders are popular material-handling machines widely used in various industries. However, such loaders experience frequent breakdowns due to high dynamic loads; they are often subjected to intensive tyre wear and excessive fuel consumption. Frequently, these issues arise from the improper actions of an operator. Given the labour intensity of the workflow, an operator, regardless of qualification, cannot ensure optimal loader control at an acceptable speed for a long time. In addition, an operator usually works in harsh environments with a high risk of injury, e.g. due to loss of stability. Manual control of loaders also limits the use of these machines in places that are dangerous for humans, for example, during the response to disasters. The solution to these issues is to automate the loader and exclude the operator from the machine work. One of the tasks of loaders automation is to ensure their movement along a given trajectory from the face to the place of unloading the material and back in the opposite direction. Goal. This work aims to increase the productivity and energy efficiency of a rigid-frame skid steer loader by ensuring its following along a given trajectory. Methodology. Based on the kinematics model of the loader, a two-loop control system for motion along a desired trajectory is designed. The control system combines feedforward and feedback loops. The feed-forward control is based on the desired speeds and accelerations. The closed loop is a state controller that uses the loader distance from the desired trajectory at a given time and the course angle as the state variables. Results. According to the simulation results, the proposed two-loop control system ensures the movement of the loader along a desired trajectory with an accuracy of up to 0.3 m. Originality. Further development of the up-to-date control theory was achieved by applying it to a new object, namely a skid steer front loader with a rigid frame. Practical value. The implementation of the proposed control system will increase the productivity of the loader, as well as reduce the number of accidents at construction sites.