Motion Simulation Of Flexible Chassis Based On ADAMS And Steering Characteristics Study

The flexible chassis based on four wheel independent drive,independent steering and independent suspension drives by electric power,which has the advantages of reducing emissions and protecting environment.In this paper,the flexible chassis is driven by a bias shaft steering mechanism which can simpify structure,make steering flexible and reduce its turning radius.Flexible chassis has oblique line,in situ U-turn and 90 degrees,such as the existing chassis system can not be achieved in the form of movement,so it has a very important practical significance for the development of greenhouse operation or the automobile chassis.However,the combination of four independent driving and independent steering improves the control difficulty of flexible chassis.This paper with engine speed,load and rotation as test factors,with the stable output time of flexible chassis,the size of the traction force and steering response as the evaluation index,with comprehensive application of model analysis and experimental verification including the establishment of the flexible chassis model which based on ADAMS multi-body dynamics analysis software,the load test and steering test,study on the motion and dynamic characteristics of flexible chassis to provide the basic data for the control of flexible chassis and provide support for the improvement of control strategy and controller.The main contents and conclusions of this paper are as follows:(1)The flexible chassis system multi-body dynamics model which based on the ADAMS prototype technology considering the influence of gravity is established.Add kinematic pair and virtual constraint to model system,add load to frame,add contact for chassis and test table,add drive for electric wheel to simulate.A virtual analysis model for dynamic characteristics of flexible chassis under different loads is presented.(2)The load characteristics of flexible chassis were studied on the test bench to study the dynamic characteristics of flexible chassis and verify the model which studies on the flexible chassis motion.The dynamic characteristics of the flexible chassis are studied with speed and load as independent variables under the conditions of straight line,45 degree oblique line,in situ steering and under lateral posture.Concluding: the traction force of the chassis increases with the load and varies with the posture of the chassis.When the load is 2000 N,the traction force is 1545.55 N under straight line,the traction force is 1471.92 N under 45 degree obliqueline,and the tractive force is 1518.14 N under lateral posture.The electric wheel of the steady time differences,mainly related to the structure of hub motor characteristics and bias load difference,in the development of controller,should minimize the time difference of each wheel,ensure the motion stability of flexible chassis.The dynamic model of flexible chassis is simulated by using ADAMS software,and the error is less than 10%.(3)Steering test of flexible chassis on ordinary cement pavement are carried out to study the motion characteristics of flexible chassis.With the rotation angle as experiment factors,flexible chassis in parking straight posture were switched to the 45 degree oblique posture,in situ steering and the transverse posture response test and accuracy test of steering angle to evaluate response time and accuracy of the angle of each wheel.The test results which provided guidance for control of data show that the flexible chassis in the start of the steering command,from the straight line to switch respectively to 45 degree oblique line,in situ steering and transverse posture can be completed in 1s,1.5s,2s;the error of the steering angle of the flexible chassis is controlled in the range of 1 degrees with the rotation speed of10r/min.The above conclusions can provide basic data for flexible chassis control.