| The wheeled rover is the preferred solution for planetary missions.In China's lunar exploration program,the rover yutu is a wheeled mobile robot.China has launched its Mars exploration program,and wheeled mobile robots which is the main alternative,have become a research hotspot.In the process of carrying out the planetary exploration mission,the most important motion state variables are the slip ratio,the side slip angle and the sinkage.Whether these three variables can be perceived effectively will directly affect the performance of the rover and the success or failure of the mission.Two rovers,opportunity and spirit,have had serious crashes in the soft earth.The causes of such accidents is the lack of effective research on the subsidence warning mechanism of planetary vehicle,and the research on the estimation of wheel motion state parameters is the necessary prerequisite.Research on the estimation method of wheel motion state parameters can provide necessary state feedback variables for planetary vehicle,which is an important means to improve the perception ability of planetary vehicle,and also an important research basis for planetary vehicle motion control,trajectory tracking and path planning.However,the perception of wheel state parameters such as slip ratio,sideslip angle and sinkage is always a difficulty.Therefore,it is of great significance to estimate the wheel motion state parameters using the information obtained from the planet vehicle's own sensors.Through the research and analysis of the wheel trace imprint,it is found that the wheel motion state information is contained in the wheel trace imprint.Based on the rutting information,key wheel motion state parameters such as wheel slip ratio,side slip angle and sinkage can be estimated effectively.Traditional ground vehicles and wheeled mobile robots generally work under the condition of soft wheel and hard ground,and less consideration is given to the problem of wheel slip and subsidence.However,compared with the driving surface vehicles,the planet rovers generally use hard metal wheels,working in the soft star soil.Under this condition,the wheel of the plan et car has obvious damage to the soil,which is manifested as longitudinal slip,lateral slip and subsidence.The quantitative expressions used to evaluate the above three phenomena are slip rat io,side slip angle and sinkage,which are the most important motion state variables of planetary rover wheels.The degree of perception of these three variables directly affects the performance of the planet vehicle and the success or failure of the mission.However,slip rate,side deflection and subsidence have always been difficult to perceive in the state of planetary rover wheels.In addition,considering the limitation conditions of load,power and space imposed by the rovers on the perceptive equipment,some larger perceptive equipment cannot effectively adapt to the detection task of the rovers,making it more difficult to solve the perception problem of wheel parameters.Therefore,it is of great significance to estimate the wheel-terrain interaction parameters with the information obtained from the sensor of the planet rovers.Through the research and analysis of the wheel trace,it is found that the wheel trace of the planet rover contain the relevant information of wheel motion.Based on the wheel trace information,the key wheel-terrain interaction parameters such as the wheel slip ratio,side slip Angle and sinkage can be estimated effectively.However,the research on wheel trace formation process and mechanism is the basis of the research on wheel trace based recognition method of wheel slip rate.In this paper,the wheel trace process and forming mechanism of the main wheel with rigid spur on the soft star soil are analyzed.Based on the analysis of the interaction stage between wheel spur and soil,the definition and conceptual boundary conditions of different wheel trace formation stages are given.By analyzing the influence of wheel spur and hub on wheel trace formation,the mechanism of wheel trace formation was revealed.Based on the wheel trace mechanism,the wheel trace process is analyzed by analyzing the track of wheel spur motion.The theoretical system of wheel trace formation mechanism is constructed to lay a foundation for the subsequent research.The research of wheel trace unit morphology based on wheel-ground interaction is helpful to understand the structural causes and optical imaging characteristics of wheel trace.On the basis of wheel trace formation mechanism,a wheel trace element morphological model was established.Furthermore,the wheel trace unit morphological model is expanded and the wheel trace morphological model is established.On this basis,the wheel trace imaging model is established by analyzing the wheel trace imaging characteristics,which provides the necessary theoretical basis for the wheel motion estimation method based on imag e information.A wheel-terrain interaction parameter estimation method based on wheel trace characteristics is proposed.Based on the process and mechanism of wheel trace formation,the skeleton characteristics of wheel trace element,wheel trace time domain characteristics and wheel trace frequency domain characteristics are analyzed.According to the wheel trace characteristics,the wheel-terrain interaction parameter estimation models based on the wheel trace characteristics,such as lateral deflection,slip rate and subsidence,are established.The method of rut feature parameter extraction based on rut imaging model is studied.Combined with machine vision technology,the engineering application of this method is presented.The framework of wheel parameter identification system based on wheel trace image information is established and the identification process is given.Research on image preprocessing of wheel trace complex illumination,feature extraction of wheel trace area and feature classification of wheel trace area was carried out.Combined with wheel-terrain interaction parameter estimation method based on wheel trace feature,engineering application of wheel-terrain interaction parameter identification was made possible.And the whole vehicle test system of star vehicle is used to verify.Finally,this method is used to analyze the wheel trace photos of opportunity rover and obtain the recognition results of wheel slip rate.The research results of this paper can solve the key motion parameter perception problems such as the wheel slip rate,side deflection Angle and subsidence amount of the planet vehicle,and provide a responsive engineering solution. |
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