Camilla Guerrieri’s Portrait of Guidobaldo II della Rovere:Symbols of Honor and Power

The Altomani&Sons Collection owns a remarkable newly discovered portrait of Guidobaldo II della Rovere,Duke of Urbino(1514-1574),a historical military figure who was a condottiere,ruler of Urbino,Commander-in-chief of the Papal Estate,and Perfect of Rome,as well as a collector and patron of the Fine Arts.Camilla Guerrieri Nati(1628-1694),a seventeenth-century Italian painter from Fossombrone(in the province of Pesaro and Urbino),portrayed this heroic personage surrounded by emblems associated with his military courage and leadership,including his plumed burgonet helmet,metal gilded armor,a necklace with the golden fleece,and batons of secular and religious dominions.This oil painting on copper-considered a precious metal at the time-emphasizes the importance of the commission.The material and technique also reveals a unique artistic achievement in that it provides the painting with a smooth,reflective surface and vibrant coloration,symbolizing precious imagery.

Kinematic modeling and analysis of novel eight-wheel lunar rover

A new kind of eight-wheel lunar rover is developed, which is a complex closed-chain system and has good capabilities of climbing slope, surmounting obstacles and adapting to uneven terrain. In this paper, the mechanical structure of the novel eight-wheel lunar rover is introduced, forward and inverse kinematic models of the rover are established according to the closed-chain coordinate transformation and instantaneous coincidence coordinate. Based on structural characteristics, its kinetic characteristics are analyzed. Wheel slippages are separated and calculated, and a method for closed-loop control modification using wheel slip estimation during the model establishment is proposed. The results can be applied to the motion control of lunar rover.

Virtual Simulation System with Path-following Control for Lunar Rovers Moving on Rough Terrain

Virtual simulation technology is of great importance for the teleoperation of lunar rovers during the exploration phase, as well as the design of locomotion systems, performance evaluation, and control strategy verification during the R&D phase. The currently used simulation methods for lunar rovers have several disadvantages such as poor fidelity for wheel-soil interaction mechanics, difficulty in simulating rough terrains, and high complexity making it difficult to realize mobility control in simulation systems. This paper presents an approach for the construction of a virtual simulation system that integrates the features of 3D modeling, wheel-soil interaction mechanics, dynamics analysis, mobility control, and visualization for lunar rovers. Wheel-soil interaction experiments are carried out to test the forces and moments acted on a lunar rover’s wheel by the soil with a vertical load of 80 N and slip ratios of 0, 0.03, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.6. The experimental results are referenced in order to set the parameters’ values for the PAC2002 tire model of the ADAMS/Tire module. In addition, the rough lunar terrain is simulated with 3DS Max software after analyzing its characteristics, and a data-transfer program is developed with Matlab to simulate the 3D reappearance of a lunar environment in ADAMS. The 3D model of a lunar rover is developed by using Pro/E software and is then imported into ADAMS. Finally, a virtual simulation system for lunar rovers is developed. A path-following control strategy based on slip compensation for a six-wheeled lunar rover prototype is researched. The controller is implemented by using Matlab/Simulink to carry out joint simulations with ADAMS. The designed virtual lunar rover could follow the planned path on a rough terrain. This paper can also provide a reference scheme for virtual simulation and performance analysis of rovers moving on rough lunar terrains.

Wheel slip-sinkage and its prediction model of lunar rover

In order to investigate wheel slip-sinkage problem, which is important for the design, control and simulation of lunar rovers, experiments were carried out with a wheel-soil interaction test system to measure the sinkage of three types of wheels in dimension with wheel lugs of different heights and numbers under a series of slip ratios (0-0.6). The curves of wheel sinkage versus slip ratio were obtained and it was found that the sinkage with slip ratio of 0.6 is 3-7 times of the static sinkage. Based on the experimental results, the slip-sinkage principle of lunar's rover lugged wheels (including the sinkage caused by longitudinal flow and side flow of soil, and soil digging of wheel lugs) was analyzed, and corresponding calculation equations were derived. All the factors that can cause slip sinkage were considered to improve the conventional wheel-soil interaction model, and a formula of changing the sinkage exponent with the slip ratio was established. Mathematical model for calculating the sinkage of wheel according to vertical load and slip ratio was developed. Calculation results show that this model can predict the slip-sinkage of wheel with high precision, making up the deficiency of Wong-Reece model that mainly reflects longitudinal slip-sinkage.

The Mars rover subsurface penetrating radar onboard China's Mars 2020 mission

China's Mars probe,named Tianwen-1,including an orbiter and a landing rover,will be launched during the July-August 2020 Mars launch windows.Selected to be among the rover payloads is a Subsurface Penetrating Radar module(RoSPR).The main scientific objective of the RoSPR is to characterize the thickness and sub-layer distribution of the Martian soil.The RoSPR consists of two channels.The low frequency channel of the RoSPR will penetrate the Martian soil to depths of 10 to 100 m with a resolution of a few meters.The higher frequency channel will penetrate to a depth of 3 to 10 m with a resolution of a few centimeters.This paper describes the design of the instrument and some results of field experiments.

MOBILITY EVALUATION AND INNOVATION OF WHEELED SPACE ROVER

The mission and function requirements of lunar rover are analyzed, based on virtual prototype technology, the mobility evaluation theory and method for wheeled space rover are proposed, which provide a new way to study the innovative design of lunar rover. Based on the above theoretical system, an innovative lunar rover suspension system, which adopts a two-crank-slider mechanism, is proposed, and its dynamics model is created. Adopting virtual prototype technology, the ground adaptability, over-obstacle ability and driving placidity of the rover are evaluated in the virtual prototype software ADAMS. The analysis results show that the rover provides a high degree of mobility.

The penetrating depth analysis of Lunar Penetrating Radar onboard Chang＇e-3 rover

Lunar Penetrating Radar（LPR） has successfully been used to acquire a large amount of scientific data during its in-situ detection. The analysis of penetrating depth can help to determine whether the target is within the effective detection range and contribute to distinguishing useful echoes from noise.First, this study introduces two traditional methods, both based on a radar transmission equation, to calculate the penetrating depth. The only difference between the two methods is that the first method adopts system calibration parameters given in the calibration report and the second one uses high-voltage-off radar data. However, some prior knowledge and assumptions are needed in the radar equation and the accuracy of assumptions will directly influence the final results. Therefore, a new method termed the Correlation Coefficient Method（CCM） is provided in this study, which is only based on radar data without any a priori assumptions. The CCM can obtain the penetrating depth according to the different correlation between reflected echoes and noise. To be exact, there is a strong correlation in the useful reflected echoes and a random correlation in the noise between adjacent data traces. In addition, this method can acquire a variable penetrating depth along the profile of the rover, but only one single depth value can be obtained from traditional methods. Through a simulation, the CCM has been verified as an effective method to obtain penetration depth. The comparisons and analysis of the calculation results of these three methods are also implemented in this study. Finally, results show that the ultimate penetrating depth of Channel 1 and the estimated penetrating depth of Channel 2 range from 136.9 m to 165.5 m（ε_r = 6.6） and from 13.0 m to 17.5 m（ε_r = 2.3）, respectively.

Attitude Control Experiments of Cubic Rover on Low-Gravity Testbed

In-situ exploration of asteroid surfaces is of great scientific significance.Internally actuated rovers have been released to asteroid surfaces but without enough controllability.To investigate the attitude control characteristics of the cubic rover for asteroid surface exploration,a series of experiments are carried out using the self-designed rover and the low-gravity testbed.The experiments focus on two major themes:The minimum flywheel speed for cubic rover to produce a walking motion in different conditions,and the relationship between the rover’s rotation angle and the flywheel speed in twisting motion.The rover’s dynamical descriptions of the walking and twisting motions are first derived.The features and design of the low-gravity testbed are then summarized,including its dynamics,setup,and validation.A detailed comparison between the dynamic model and the experimental results is presented,which provides a basic reference of the cubic rover’s attitude control in low-gravity environments.

Design and Trafficability Study of Flexible Wheel for Planetary Exploration Rover

To reduce sending costs, a flexible wheel configuration is proposed. The wheel is made of titanium alloy （Ti-6Al-4V） in consideration of the planetary environment factors （i. e. strong radiation, big temperature differences, high vacuum）, and mass constraint of launch vehicle. The advantages of the proposed wheel involves the potential for： ① small sending volume and mass, ② large deployed area and volume to reduce wheel loading, ③ a damping effect to smooth motion on rough terrain. To study the trafficability and tractive performance of the wheel concept, the drawbar pull and driven torque were calculated based on simplified model of terramechanics formulations. The results show that the wheel possesses sufficient drawbar pull to negotiate all types of soil stratums listed in this contribution.

Configuration Synthesis and Performance Evaluation Metrics of Lunar Rover Locomotion Systems

A method of topology synthesis based on graph theory and mechanism combination theory was applied to the configuration design of locomotion systems of lunar exploration rovers(LER).Through topology combination of wheel structural unit,suspension unit,and connecting device unit between suspension and load platform,some new locomotion system configurations were proposed and the metrics and indexes to evaluate the performance of the new locomotion system were analyzed.Performance evaluation and comparison between two LER with locomotion systems of different configurations were analyzed.The analysis results indicate that the new locomotion system configuration has good trafficability performance.

Mechanical Analysis and Performance Optimization for the Lunar Rover’s Vane-Telescopic Walking Wheel

It is well-known that optimizing the wheel system of lunar rovers is essential.However,this is a difficult task due to the complex terrain of the moon and limited resources onboard lunar rovers.In this study,an experimental prototype was set up to analyze the existing mechanical design of a lunar rover and improve its performance.First,a new vane-telescopic walking wheel was proposed for the lunar rover with a positive and negative quadrangle suspension,considering the complex terrain of the moon.Next,the performance was optimized under the limitations of preserving the slope passage and minimizing power consumption.This was achieved via analysis of the wheel force during movement.Finally,the effectiveness of the proposed method was demonstrated by several simulation experiments.The newly designed wheel can protrude on demand and reduce energy consumption;it can be used as a reference for lunar rover development engineering in China.

Configuration and kinematics analysis of locking-releasing mechanism for side-loaded lunar rover

In order to save space for storing precision equipments,lower the center of mass of Lander and reduce lunar rover's dimension constraint limited by mechanism of Lander,the locking-releasing mechanism of side-loaded lunar rover loaded outside Lander is presented,which is a kind of metamorphic mechanism.To ensure the working of this mechanism as the metamorphic process designed,configuration analysis of the locking-releasing mechanism is carried out,and topological structures are described by Huston lower numbered arrays.A kinematic mathematical model of the mechanism is established through homogeneous transformation matrix.The kinematic simulation validates the feasibility of the locking-releasing mechanism when the configurations are shifted from one to the other.

Numerical method for estimation of kinematical parameters for articulated rovers on loose rough terrain

Based on the study of passive articulated rover,a complete suspension kinematics model from wheel to inertial reference frame is presented,which uses D-H method of manipulator and presentation with Euler angle of pitch,roll and yaw.An improved contact model is adopted aimed at the loose and rough lunar terrain.Using this kinematics model and numerical continuous and discrete Newton's method with iterative factor,the numerical method for estimation of kinematical parameters of articulated rovers on loose and rough terrain is constructed.To demonstrate this numerical method,an example of two torsion bar rocker-bogie lunar rover with eight wheels is presented.Simulation results show that the numerical method for estimation of kinematical parameters of articulated rovers based on improved contact model can improve the precision of kinematical estimation on loose and rough terrain and decrease errors caused by contact models established based on general hypothesis.

Preface: The Chang'e-3 lander and rover mission to the Moon

The Chang＇e-3 （CE-3） lander and rover mission to the Moon was an in- termediate step in China＇s lunar exploration program, which will be followed by a sample return mission. The lander was equipped with a number of remote-sensing instruments including a pair of cameras （Landing Camera and Terrain Camera） for recording the landing process and surveying terrain, an extreme ultraviolet camera for monitoring activities in the Earth＇s plasmasphere, and a first-ever Moon-based ultravi- olet telescope for astronomical observations. The Yutu rover successfully carried out close-up observations with the Panoramic Camera, mineralogical investigations with the VIS-NIR Imaging Spectrometer, study of elemental abundances with the Active Particle-induced X-ray Spectrometer, and pioneering measurements of the lunar sub- surface with Lunar Penetrating Radar. This special issue provides a collection of key information on the instrumental designs, calibration methods and data processing pro- cedures used by these experiments with a perspective of facilitating further analyses of scientific data from CE-3 in preparation for future missions.

Experimental analysis on effect of grouser circumferential angle on motion performance of lunar rover wheel

To guide the design of grouser parameters for lunar rover wheel,the effect analysis of circumferential angle of grousers on motion performance of a rigid wheel was conducted in a laboratory single-wheel test bed with loose sand bin.All tests had been done at a free wheel sinkage.The circumferential angle was varied from 0°,5°,10°,15° to 20°.By the analysis and comparisons of tractive and steering performance between smooth wheels and wheels with different circumferential angle grousers,the results show that the drawbar pull(DP),driving torque(DT) and steering resistance moment(SRM) decrease slightly with the increasing circumferential angle.And chevron grousers are more beneficial to improve the tractive performance than herringbone grousers.In order to evaluate motion performance of wheels with grousers,the evaluation indexes of motion performance are introduced into the experimental results.The results reveal that the optimal circumferential angle is 0°,and the optimum value of wheel slip is 13% from the perspective of saving energy to the similar loose sand in the experiments.

Calculation on the pitch angle of rocker of a rocker lunar rover in uneven terrain and path planning

For the concerted motion of rocker lunar rover, the pitch angle of rocker of a rocker lunar rover in uneven terrain must be calculated. According to the character of passive shape-shifting adaptive suspension of rocker lunar rover, the model of rocker lunar rover and the model of terrain were both simplified. The pitch angle of rocker was calculated using forward solving, reverse solving and the method of offsetting the curve of terrain respectively. Because of the banishment of the nonlinearity of equation sets of calculation by reverse solving, the calculation of the pitch angle based on reverse solving was programmed by means of MATLAB. Simulations were carried out by means of ADAMS. The result verified the validity of the calculation based on reverse solving. It provides the theoretical foundation for motion planning and path planning of rocker lunar rover. As applications of the calculation of pitch angle of rocker, the multi-attribute decision making of path based on the concerted motion planning and the predictive control on lunar rover based on the Markov prediction model were introduced.

Steering mechanical analysis for lunar rover wheel

Facing the requirement of establishing a steering mechanical model for the wheel configuration design,selection of steering motors, dynamic analysis and simulation of the lunar rover, shear force beneaththe steering wheel, bulldozing resistance acting on steering wheel rims and side surfaces respectively areconducted on the basis of the wheel-loose soil interaction. The quantitative relation between steering resistancemoment (SRM) and steering radius, dimension of the wheel, soil parameters is established. Tovalidate the model, a single-wheel test bed is employed to test the steering performance of a wheel with0.15735m radius and 0.165m width when the steering radius is 0.00m, 0.04m, 0.08m, 0.12m and0.16m, respectively. The SRM is approached asymptotically with the increasing steering angle and almostproportional to the steering radius. The theoretical results of SRM are compact with the experimental results,which shows that the steering model can predict the experimental results well.

Panoramic camera on the Yutu lunar rover of the Chang'e-3 mission

The Chang＇e-3 panoramic camera, which is composed of two cameras with identical functions, performances and interfaces, is installed on the lunar rover mast. It can acquire 3D images of the lunar surface based on the principle of binocular stereo vision. By rotating and pitching the mast, it can take several photographs of the patrol area. After stitching these images, panoramic images of the scenes will be obtained.Thus the topography and geomorphology of the patrol area and the impact crater, as well as the geological structure of the lunar surface, will be analyzed and studied.In addition, it can take color photographs of the lander using the Bayer color coding principle. It can observe the working status of the lander by switching between static image mode and dynamic video mode with automatic exposure time. The focal length of the lens on the panoramic camera is 50 mm and the field of view is 19.7？umination and viewing conditions, the largest signal-to-no×14.5？.Under the best illise ratio of the panoramic camera is 44 d B. Its static modulation transfer function is 0.33. A large number of ground testing experiments and on-orbit imaging results show that the functional interface of the panoramic camera works normally. The image quality of the panoramic camera is satisfactory. All the performance parameters of the panoramic camera satisfy the design requirements.

“关公”战“秦琼”AUDI A8 3.7 VS. LAND ROVER Range Rover

这场奇特的厮杀,多少有些"关公战秦琼"的味道。在中国几千年古代征战史中,有着"一寸长、一寸强;一寸短、一寸险"的说法。事实上,短兵器也确实不及长枪大刀妙趣横生威风八面、声名赫赫。然而尺有所知寸有所长,AUDIA83.7与RANGE ROVER V84.4,如同关云长的青龙偃月刀遇到了秦叔宝的瓦面金装镜,孰强孰弱?一试便知!

From the Rover Incident to the Nanjia Treaty―Whose Conflict? Whose Treaty?

This paper will focus on the Rover Incident of 1867 and the subsequent Nanjia Treaty;the main protagonists of the incident were the Kuraluts indigenous people;and different perspectives will be explored by integrating archaeological and historical data.The Rover Incident,a conflict between the Kuraluts and the United States,led to the Nanjia Treaty(Treaty of the Southern Headland),a reconciliation between the US and Tauketok,pre-eminent leader of 18 indigenous communities inhabiting this region.From the geographic location of the Kuraluts Village(Sheding Site),however,as well as from foreign coins and blue-and-white ceramics found as funerary objects inside stone coffins,it would seem that such contacts with the outside world were relatively frequent.Moreover,due to the aborigines’ability to make use of knowledge of the local geography and their military skills to defeat forces from the US’s naval fleet―which also indicates they were familiar with weaknesses in the military operations of foreign vessels―as a result,neither the US side nor Tauketok seemed to have any need to resort to the use of military force.