Digital Twin Oriented Parameter Identification Of Wheel-terrain Interaction Model For Planetary Rovers On-orbit Mobility

In recent years,China made great achievements in the planetary exploration field.The Yutu-2 rover achieved the exploration of the far side of the moon,and the Zhurong rover left China’s mark on Mars,demonstrating the technological strength of our country’s aerospace industry.In the future,China will future implement exploration missions of the moon and other planets,deepen basic theoretical research,complete key technological breakthroughs,and explore major scientific discoveries.The digital twin originated in the aerospace field.With the development of data transmission,virtual simulation,and the increasing complexity of exploration missions,the digital twin system for planetary rovers will become the focus.For the digital twin system of the planetary rover on-orbit mobility,this paper establishes a wheel-terrain interaction model that considering load effect,proposes methods for model parameter identification and wheel state estimation,estimates planetary soil dominate parameters,carries out moving ability prediction at the landing zone of the Mars rover by using the virtual planet rover,verifies the control commend and predicts the moving end point of the lunar rover rock detection process based on the research of digital twin.Realizing the digital twin of the lunar rover rock exploration process,verifying the control command and improving the prediction accuracy of mobile performance.Experimental research on planetary rover wheel terrain interaction mechanics under multi-load conditions was carried out.A series of experiments on the interaction between wheels and simulated planetary soil under vertical load conditions were carried out by using a single wheel test bed and a prototype of a planetary rover.In the experiment,the influence law of vertical load on the motion state of the wheel,the subsidence index in the soil bearing characteristics and the shear deformation modulus in the shearing characteristic is obtained.Then a wheel-terrain interaction model considering load effect is established and verified by the experimental data.Provide model basis for the parameter identification.An in-situ parameters identification method is proposed based on the analysis of the typical parameters of planetary soil,and the method is verified by the singlewheel experimental data.Aiming at solving the problem of obtaining the wheelterrain interaction multi-condition data for parameter identification,multi-slip and multi-load working condition generation schemes of the planetary rover based on active control wheel speed and suspension angle is proposed.And the schemes are realized and verified in the simulation platform.Aiming at the problem that the wheel-terrain interaction model has high coupling degree and many parameters,it is difficult to realize the online identification of all parameters,an online identification method for the main parameters of the model is proposed.Using an analytical method to analyze the sensitivity of each parameter in the model,and the dominant parameters of the bearing and shearing characteristic are determined.Then a dominant parameters identification method is proposed and verified by simulation and experiment.Considering that the complex model is difficult to apply online,a simplified wheel-terrain interaction model is further deduced to solve the problem of many parameters and long computation time.In order to estimate the wheel slip ratio,sinkage and force state of the planetary rover,considering the types of sensors that carried by rovers,proposing the wheel running states estimation method.The wheel slip and sinkage are estimated from camera image,and the wheel driving torque is estimated according to motor current,the above data is brought into the simplified wheel-terrain interaction model,and the normal support force and drawbar pull of the wheel are deduced according to the force balance relationship.Thus,the motion and force state of each wheel are obtained.The parameter identification method is verified by the rover prototype and simulation platform.Based On the analysis of the rover data communication and data perception,a design scheme of digital system for rover on-orbit mobility is proposed.And according to the rover on-orbit data,the dominate parameters of planetary soil are estimated.The virtual rover was built to predict the moving waypoints in the landing zone.The virtual rover was used to verify the control commend of the rock exploration mission and predict the moving endpoint position.The research of this paper is aimed at the digital twin of the planetary rover moving in orbit,have theoretical guiding and engineering application value to the wheel-terrain interaction and digital twin system construction of the planetary rover,the control commend verification and moving end point prediction are realized by a virtual Lunar rover.