| The light and small-type mobile sprinkling machine has the advantages of simple structure,low cost and flexible mobility,which meets the needs of agricultural development.Therefore,it is welcomed by farmers and widely used in China.In recent years,the light and small-type mobile sprinkling machine based on autonomous navigation technology was developed to improve the automation level of sprinkler irrigation.Howerver,the sprinkling machine would deviate from the scheduled route because of the environmental disturbances during working.In order to ensure the irrigation efficiency and quality,the sprinkling machine needs to eliminate the driving error quickly by steering.Therefore,the steering control system is an important prerequisite for automatic irrigation,and the research on it is meaningful.In view of the above background,the research group developed a light and small-type mobile sprinkling machine with solar driven as the research platform,the steering system and steering control strategy were disgussed in this paper.In addition,the related experiments were carried out.The main contents and conclusions of this paper are as follows:(1)Using front-wheel steering,rear-wheel driving and distributed structure,the steering system and component parameters were designed.Further,the mathematical relationships of front-wheel angles and rear-wheel speeds was established based on the Ackermann ideal steering model,and the problem of front-wheel angles’ coordination control and rear-wheel speeds’ differential control were put forward.(2)Based on the cross-coupling algorithm and the mathematical relationship between front-wheel angles,the front-wheel angle synchronization controller was designed,which consists of a cross-coupling module based on the fuzzy-PD control method and two front-wheels angle PID controllers.Further,the feasibility of the controller was tested by MATLAB-simulink simulation and the front-wheel angle experiment.The experiment results show that the controller can basically meet the requirements of the angle follow-up performance and synchronization control precision.When the expected inside front-wheel angle input was 20° or-20°,the rise time was within 4 seconds,the overshoot of front-wheel angle was less than 2°,and the fluctuation range was small,and the contour error could be reduced to a smaller range within 4 seconds,the oscillatinon amplitude was small too.When the expected inside front-wheel angle input was 45° or-45°,the angle rise time was within 6 seconds,the angle overshoot was no greater than 3°,the fluctuation range also was small,and the contour error could get rapid inhibition in less than 7 seconds basically,the shock value is controlled within 1°.(3)According to the working principle of mechanical differential and the driving speed of the sprinkling machine,the rear-wheel electronic differential controller based on PID algorithm was designed,which meets the mathematical relationship between rear-wheel speeds by reducing the speed of the inner rear wheel and increasing the speed of outer rear wheel.The MATLAB-simulink simulation and the rear-wheel speed response experiment results show that when the sprinkling machine was running straight(α=0°),the rise time was about 7 seconds when the expected speed input was 1m/min,and the speed fluctuation was small,the speeds of the rear wheel on both sides were basically equal.After the speed was stable,the speed of the right rear wheel decreased and the left rear wheel increased during the process of turning right(α=45°),the speed of the right rear wheel increased and the left rear wheel decreased during the process of turning right(α=-45°),and the rise time was about 6 seconds,the speed fluctuation range was small.The speed ratio of right rear wheel to left rear wheel was also not much different from the expected one.The controller can basically achieve rear wheels differential control of the sprinkling machine. |
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