Research On Optimal Adhesion Control Of Heavy-haul Locomotives Based On Extreme Value Search

In transportation,the heavy-haul locomotive is an important part of the freight transportation in China.The traction force of the locomotive is realized through the adhesion of the contact surface between the locomotive wheel pair and the rail.If he adhesive force is reduced because of the change of the external environment,the traction power of the locomotive will also be reduced,which will directly affect the actual performance of the locomotive.The experiment shows that the actual adhesive force of the locomotive has a certain function relationship with the speed of the locomotive creep.The optimal creep speed can be searched by using the extremum search algorithm to control the locomotive traction and improve the adhesion utilization rate effectively.The modern adhesion control method is to continuously search the optimal adhesion point under the current rail surface in real time and control the motor torque to control the locomotive running near the optimal adhesion point.This control method has great practical significance for improving the adhesion between locomotive wheelset and car body,preventing locomotive idling,improving locomotive traction and searching extremum.This paper introduces the basic theory of adhesion,defines the basic concept of adhesion coefficient.Based on the analysis of locomotive traction system,a simplified model of locomotive dynamics is built,and the main control methods of the existing adhesive are briefly described.Aiming at the problem of optimal adhesion control for heavy-haul locomotives,an optimal adhesion control based on sliding-mode extremum search algorithm is proposed.First,the sliding-mode extremum search algorithm is used to search for the optimal creep speed of the track surface in real time,and the differential tracker is designed to track the derivative of the creep speed.Then,super-twisting sliding-mode control is designed to control the heavy-haul locomotive running near the optimum adhesion coefficient point.The simulation results show that the sliding-mode extremum search algorithm has real-time and self-adaptive ability to the changes of the external environment.Aiming at the steady-state oscillation problem of optimal adhesion control for heavy-duty locomotives based on sliding mode extremum search algorithm,a super-twistng sliding-mode control method based on extremum search algorithm without steady-state oscillation is proposed.First,apply the basic mathematical theory to prove the stability of the method.Secondly,combined with the control object,a super-sliding sliding mode controller is designed,and the stability proof analysis is given using the Lyapunov function method.Finally,combining the sliding mode extremum search method for comparison simulation,it is verified that the extremum search algorithm without steady-state oscillation can effectively reduce the flutter of the locomotive control system,eliminate the shortcomings of the sliding mode extremum search algorithm,improve the search speed,and finally eliminate steady-state oscillation.