Research On Integrated Control Of Path Tracking And Handling Stability For Articulated Steering Vehicles

With the increasing demand for mineral resources and the development of mining,"Deep Mining" and "Intelligent Mining" have become the themes of underground mine.Articulated steering vehicles have significant advantages in terms of high mobility and efficiency,and they have been widely used in the processes of rock drilling,supporting,shoveling,charging and transportation in underground mines.However,The acquisition of status and road parameters is heavily dependent on external auxiliary facilities during the running process,and the tire slip problem in the process of path tracking and handling stability control cannot be solved effectively.Therefore,the study of model-based state estimation,road parameter estimation and integrated control for articulated vehicle is important for the realization of underground "Deep Mining" and "Intelligent Mining".Firstly,taking a 4 m3 load-haul-dump(LHD)vehicle as the research object,a coupled nonlinear dynamic model of articulated vehicles was established.Considering dynamics of the frames during the driving process,the dynamics model of frames including the swing frame model of the rear axle was established.Based on Magic Formula,the nonlinear lateral and longitudinal tire force models were established.and tire vertical force model was established according to the measured static vertical deformation of tires.Considering the nonlinearity of the electro-proportional hydraulic steering system,the dead zone and the segmented characteristics of the steering control main valve,a dynamic model of hydraulic powered steering system was established.The kinematics characteristics of the articulated steering mechanism were analyzed,and the coupled nonlinear dynamic model of articulated steering vehicle including the frames,tires and hydraulic steering system was obtained.In order to verify the accuracy of the model.a real vehicle test was designed and carried out.Data such as steering control,front and rear frames responses.steering cylinder pressure,steering cylinder displacement,and articulation angle under driving conditions was acquired.A coupled nonlinear dynamics simulation model of articulated vehicle was established.The vehicle body response.articulation angle and steering system data in simulation and filed test were compared and analyzed in the time domain and frequency domain respectively.and the accuracy of the coupled nonlinear dynamic model was verified.For the state estimation problem of articulated vehicles during operation,a model-based state estimation method was studied.The sensors model were established by using the autonomous characteristics of the inertial measurement units and drift characteristics of errors.Based on Kalman filter algorithm,an articulated vehicle state information estimation algorithm with the dynamic model was proposed,and the validity and accuracy of the algorithm were verified through field tests.The research on the road adhesion coefficient estimation of articulated vehicles was carried out based on the car body and tire models.In order to accurately obtain the road adhesion coefficient during the operation of articulated vehicles,an articulated vehicle body dynamics model was used as an auxiliary model,combining with the state information obtained above,and an articulated vehicle tire force estimation algorithm filter was proposed based on Kalman.Combining with the tire force model,a estimation algorithm for road adhesion coefficients of articulated vehicles was proposed based on the least square method,and the recursive models of adhesion coefficient estimation with forgetting factors and no-forgetting factors were obtained.Numerical simulation verified the superiority of the algorithm with forgetting factor,and real vehicle tests on dry concrete roads preliminarily verified the effectiveness of the algorithm.The integrated control of articulated vehicles was studied based on the model predictive control theory.Considering the path tracking,handling stability and tire anti-slip control problems of articulated vehicles during driving condition,a comprehensive time-varying model including the path tracking,handling stability control model and tire dynamics was established based on the state space theory.An integrated controller including path tracking,handling stability and tire anti-skid control targets of articulated vehicles was established based on model predictive control theory,and the reference state variables values of path tracking and handling stability control were analyzed and obtained.Based on the estimation result of road adhesion coefficient,the target tire speed in the stable region was obtained,and the rigid constraints of the articulated vehicle structure were considered,and the constraint interval of the control quantity and the control variable were obtained.The stability of the control system was analyzed and proved based on Lyapunov stability theory.Finally,in order to verify the effectiveness of the integrated control system.numerical simulations under different working conditions were carried out.Based on the numerical simulation platform,the stability results of the integrated control system were analyzed and verified.Considering the operating conditions of articulated vehicles in underground mines,three typical operating conditions were selected during driving condition.And the running pavement was set as a dry concrete pavement during simulation.In order to analyze the control effect of the integrated control system,the conventional separate feedback control was used as the comparing method.The results of the lateral displacement,heading angle,center of mass slip angle and tire slip rate in the steering stability of the path tracking were compared and analyzed.The integrated control system can further improve the handling stability of articulated vehicles and reduce the tire slip rate to a stable interval on the basis of meeting the requirements of path tracking control.The comparison results verified the effectiveness and superiority of the integrated control system.The integrated control system can provide technical and theoretical support for the development of intelligent articulated vehicles and unmanned mines.