Research On Time Optimal Control Strategy Of Aerial Fire Fighting Vehicle

In recent years,with the rapid development of urbanization,urban environment is increasingly complicated and there are more and more high-rise buildings.Therefore,traditional fire vehicles could not satisfy our need facing this kind of fire danger.High-rise aerial fire fighting vehicle makes it convenient for rapid fire rescue of high-rise buildings.However,due to the lack of good control strategy,its performance has not been fully exploited.Problems such as slow operation,low reliability and low safety are still the key technical issues to be broken.To improve the operation performance of aerial fire fighting vehicle,this paper selects a 100 m aerial fire fighting vehicle as the research object and sets optimal control as the research purpose.Based on kinematics,dynamics and optimization theory,time optimal objective function is determined,and constraints such as speed,acceleration,driving force,as well as driving torque are added,thus optimization model is established.Then time optimal control strategy are obtained by solving the optimization model.Main research and accomplishments are as follows:(1)An algorithm of kinematic and dynamic modeling is presented for a high aerial fire fighting vehicle with complex structures.Firstly,based on the Denavit-Hartenberg algorithm,the mapping relationship between the joint vector and the arm position is deduced,and the Jacobi matrix is obtained.Secondly,based on the kinematic model,the Lagrange function is built,and the dynamic equations are obtained.Lastly,ADAMS is used to get simulation results which are compared with the theoretical results,and the effectiveness of the modeling algorithm is proved.Synchronized telescopic booms have been taken into consideration in the proposed algorithm,which has high efficiency as well as versatility and can be applied to the precise control of high aerial fire fighting vehicles.(2)In order to improve the timeliness,reliability and security of aerial fire fighting vehicle,a time optimal trajectory planning algorithm is proposed,under the consideration of the stability and non-impact of motions.Firstly,pseudo-displacement s is introduced to fit discrete points of joints motion and construct continuous geometric path with B-spline.Secondly,a convex optimization model is established,based on the continuous path,time optimal objective function that is formulated with s and its derivatives of time,velocity,acceleration,driving force and driving torque constraints.Lastly,B-spline is utilized to parameterize trajectories with finite-dimensional vector x,and interior point method is used to solve the convex optimization model to get optimal solution and time optimal trajectories of joints.(3)The proposed algorithm is used to simulate the trajectory planning of a high altitude aerial fire fighting vehicle to verify the feasibility of the algorithm.According to different conditions of constraints,three working conditions are designed and optimal trajectories are planned respectively under the three conditions.The results of trajectories show that time optimal trajectory planning can be achieved through the proposed algorithm with high feasibility and strong applicability under the circumstance of satisfying various constraints of kinematics and dynamics.