| Tracked fire fighting robots can assist or replace rescuers to enter disaster area after fire accident to handle rescue disposition,bring down disaster losses and reduce the risk of rescue.Fire guns will produce recoil in the jet,and the recoil will affect the response of robot dynamics system excitation which will not only increase the driving force and driving torque of the steering wheel,but also cause vertical motion and pitch motion,and the accuracy of artillery fire extinguishing will be affected by robot's vertical displacement and pitch angle.So it is very important to study the dynamic characteristics of the fire fighting robot,especially the impact of the impact load on the dynamic characteristics of the robot.Based on analysis of tracked mobile robots on dynamic characteristics,referencing the current research status at home and abroad,this paper researches on the dynamic characteristics of a tracked firefighting robot by means of theoretical analysis,kinematics modeling,dynamic modeling,virtual prototype simulation and experiments.The main research works in this thesis are as follows.Firstly,The overall design plan of the robot has been put forward,design of the mechanical system is completed,and the framework of the control system composed by the remote control terminal and the noumenon terminal is expounded.The virtual prototype design is completed in SolidWorks,and the 1:1dynamic simulation model is established in RecurDyn which is a multi-body dynamics software.Secondly,the mechanical model of direct pendulum suspension and curved pendulum arm suspension is established,equivalent stiffness of two kinds of suspension is derivated by comprehensive use of geometry and the mathematical theory.Driving resistance and traction have been calculated based on Beck's classic ground mechanics when robot is straight driving,driving conditions and adhesion conditions of the robot are summarized,and the correctness of the type selection of the drive motor with reducer is verified by calculating the driving force and driving torque of the robot.Tertialy,a dynamic model of swerving while walking is built,then steering resistance moment and traction torque caused by load per unit length at both sides of track under barycenter offset are analyzed,it is concluded that the required driving torque is much bigger when the robot is turning in place,and by comparing driving force equations with both sides under the condition of different transverse and longitudinal migration,the change law of driving force in steering is concluded.A dynamic model of swerving under recoil is established,the relationship between the driving force of the two sides and departure angle of the fire gun is studied while the center of gravity has different lateral and longitudinal migration.Conclusion of the dynamic characteristics of the steering dynamics is verified in RecurDyn.Experiments were carried out on the slope with a height of 30 degrees and a ramp spanning a height of 220 mm.Afterwards,the structural features and obstacle parameters of the robot are extracted from the working process of the robot,virtual structured terrain like slope,independent step,successive step,platform,trench and combined terrain are designed in RecurDyn.Trafficability characteristic of crawler-type firefighting robot is studied by dynamic simulation,the dynamic characteristics of robot in complex terrain are summarized by the changing process of the gravity center and driving torque.And obstacle crossing experiment is carried out on step across high 220 mm and slope of 30 degrees to verifying the obstacle performance of the robot.Finally,a mechanical model of the 11 degree of freedom vibration of a robot is established,based on Lagrange equation,a group of differential equations of vibration is derived and expressed in matrix form,the natural frequency and main vibration mode of the system are solved.Vibration differential equations are set up on the basis of the dynamic model of 6 degree of freedom,solving algorithm has been written in MATLAB using the properties of regular modal matrix algorithm,the vertical vibration displacement and pitch angle of vibration curve caused by uneven road surface input are analyzed,after that the results were confirmed in RecurDyn.The 11 degree of freedom vibration mechanics mathematical model is established by Lagrange method,then dynamic equations are decoupled by the regular matrix method in which algorithm is written,displacement,velocity and acceleration curves of the vertical displacement and the pitch angle of vibration are operated in MATLAB,and damping coefficient are changed to analyze the change of amplitude,attenuation time and attenuation velocity.The effect of vertical and pitching motion on the jet trajectory of fire gun is analyzed,then the jet angle of fire gun is changed,in which the vibration response of the robot under different injection angles can been analyzed. |
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