Field testing of a rover guidance, navigation, and control architecture to support a ground-ice prospecting mission to Mars

This paper provides an overview of a rover guidance, navigation, and control (GN&C) architecture being developed to support a ground-ice prospecting mission to Mars. The main contribution of this paper is to detail an integrated field campaign that demonstrates the viability of the key rover GN&C techniques needed to carry out this mission. Tests were conducted on Devon Island in the Canadian High Arctic during the summer of 2009, wherein a large field robot was driven on real polygonal terrain (a landform of interest on Mars). Lessons learned and recommendations for future work are provided.     

火星车沉陷机理与脱困策略研究

以“祝融号”火星车为研究对象,基于车辆地面力学理论分析了火星车发生沉陷的机理,基于滑转率、电流、沉陷深度等给出沉陷判别方法,制定了不同条件下“祝融号”火星车的沉陷判别准则及脱困策略。验证试验结果表明：临界沉陷时滑转率为61.25%、驱动电流为1.90 A,达到沉陷临界值后“祝融号”火星车将无法直接驶离,而“祝融号”火星车主动悬架的蠕动是实现脱困的有效方法。研究成果可为“祝融号”火星车在轨使用策略提供试验数据和参考。     

基于群体爬山策略的混合粒子群优化算法

针对粒子群优化算法（PSO）在求解高维复杂优化问题时存在搜索精度不高和易陷入局部最优解的缺陷,借鉴混合蛙跳算法（SFLA）的群体爬山思想,提出一种基于群体爬山策略的混合粒子群优化算法（CMCPSO）,并证明了CMCPSO算法的全局收敛性。对四个典型高维连续优化函数的求解表明,该算法不仅保持了PSO算法的快速收敛能力,而且吸收了SFLA算法局部精细搜索和保持种群多样性的优点,具有良好的全局收敛性。     

Design and field testing of a rover with an actively articulated suspension system in a Mars analog terrain

This study presents the electromechanical design, the control approach, and the results of a field test campaign with the hybrid wheeled‐leg rover SherpaTT. The rover ranges in the 150 kg class and features an actively articulated suspension system comprising four legs with actively driven and steered wheels at each leg’s end. Five active degrees of freedom are present in each of the legs, resulting in 20 active degrees of freedom for the complete locomotion system. The control approach is based on force measurements at each wheel mounting point and roll–pitch measurements of the rover’s main body, allowing active adaption to sloping terrain, active shifting of the center of gravity within the rover’s support polygon, active roll–pitch influencing, and body‐ground clearance control. Exteroceptive sensors such as camera or laser range finder are not required for ground adaption. A purely reactive approach is used, rendering a planning algorithm for stability control or force distribution unnecessary and thus simplifying the control efforts. The control approach was tested within a 4‐week field deployment in the desert of Utah. The results presented in this paper substantiate the feasibility of the chosen approach: The main power requirement for locomotion is from the drive system, active adaption only plays a minor role in power consumption. Active force distribution between the wheels is successful in different footprints and terrain types and is not influenced by controlling the body’s roll–pitch angle in parallel to the force control. Slope‐climbing capabilities of the system were successfully tested in slopes of up to 28° inclination, covered with loose soil and duricrust. The main contribution of this study is the experimental validation of the actively articulated suspension of SherpaTT in conjunction with a reactive control approach. Consequently, hardware and software design as well as experimentation are part of this study.     

Effects of foot placement,hand positioning,age and climbing biodynamics on ladder slip outcomes

Ladder falls frequently cause severe injuries; yet the factors that influence ladder slips/falls are not well understood. This study aimed to quantify (1) the effects of restricted foot placement, hand positioning, climbing direction and age on slip outcomes, and (2) differences in climbing styles leading to slips versus styles leading to non-slips. Thirty-two occupational ladder users from three age groups (18–24, 25–44 and 45–64 years) were unexpectedly slipped climbing a vertical ladder, while being assigned to different foot placement conditions (unrestricted vs. restricted toe clearance) and different hand positions (rails vs. rungs). Constraining foot placement increased the climber's likelihood of slipping (p < 0.01), while younger and older participants slipped more than the middle-aged group (p < 0.01). Longer double stance time, dissimilar and more variable foot and body positioning were found in styles leading to a slip. Maintaining sufficient toe clearance and targeting ladder safety training to younger and older workers may reduce ladder falls.

Practitioner Summary: Ladder falls frequently cause severe occupational fall injuries. This study aims to identify safer ladder climbing techniques and individuals at risk of falling. The results suggest that ladders with unrestricted toe clearance and ladder climbing training programmes, particularly for younger and older workers, may reduce ladder slipping risk.     

Modeling of flexible metal wheel for pressurized lunar rover and traction performance prediction

The pressurized lunar rover has become one of the most important equipment in lunar exploration and resource utilization missions. On the terrain of soft lunar regolith, the rover wheels are easy to slip, sink, or even fail to move. To improve the traction performance of the rover on soft lunar soil, it is necessary to study the interaction between the wheels and the lunar soil. The deformation of the flexible wheel provides a larger contact area, which results in greater tractive force. Moreover, flexible wheels have better comfort and stability than rigid wheels, which are needed for manned rovers. However, there are few studies on the wheel soil interaction model of the heavy flexible wheel for the pressurized lunar rover. In this paper, a metal flexible wheel soil interaction model for pressurized lunar rovers was established, and the traction performance of the flexible wheel was predicted by using this model. Then, the accuracy of the wheel soil interaction model was verified by the soil bin test. The experimental results showed that the average error between the theoretical value of sinkage and the experimental value was 13.9%, and the average error between the theoretical and experimental value of drawbar pull was 11.5%, indicating that the model has high prediction accuracy. The new model can be used to predict the traction performance of flexible wheels and the experimental results can provide a reference for the flexible wheel design lunar rovers.     

分层卫星网络中的接入策略研究

研究了在分层分域卫星网络结构下的用户接入问题,包括网络节点编址、用户位置信息注册和更新、多星接入策略等,通过比较几种单层卫星网络常用的多星接入策略,提出了多层卫星网络的多星接入策略,最后对提出的接入策略在双层卫星网络上进行了仿真分析,得出了接入策略适用于分层卫星网络的结论。     

The effects of container design and stair climbing on maximal acceptable lift weight, wrist posture, psychophysical, and physiological responses in wafer-handling tasks

Despite the high level of automation in semiconductor manufacturing processes, many manual operations are still involved in the workplace. Due to inadequate human–machine interface design, stairs are frequently used to help operators perform wafer-handling tasks. This study was designed to evaluate the effects of climbing stairs and carrying wafer containers (pods) on psychophysical responses (maximal acceptable weight of lift—MAWL, and ratings of perceived exertion—RPE), physiological responses (oxygen consumption—VO₂, and heart rate—HR), and wrist posture (ulnar and radial deviations). Each of 12 subjects (six males and six females) performed six sessions (3 climbing stairs×2 pods types). The results indicate that climbing stairs had a significant influence on MAWL and VO₂ (p<0.01). The type of pod effect on wrist posture was significant (p<0.01). Gender effect differences on MAWL, VO₂ and wrist posture were also significant (p<0.05). Job design implications are discussed.     

Terrain‐adaptive wheel speed control on the Curiosity Mars rover: Algorithm and flight results

NASA's Mars Science Laboratory Curiosity rover landed in August 2012 and began experiencing higher rates of wheel damage beginning in October 2013. While the wheels were designed to accumulate considerable damage, the unexpected damage rate raised concerns regarding wheel lifetime. In response, the Jet Propulsion Laboratory developed and deployed mobility flight software on Curiosity that reduces the forces on the wheels. The new algorithm adapts each wheel's speed to fit the terrain topography in real time, by leveraging the rover's measured attitude rates and rocker/bogie suspension angles and rates. Together with a rigid‐body kinematics model, it estimates the real‐time wheel‐terrain contact angles and commands idealized, no‐slip wheel angular rates. In addition, free‐floating “wheelies” are detected and autonomously corrected. Ground test data indicate that the forces on the wheels are reduced by 19% for leading wheels and 11% for middle leading wheels. On the ground, the required data volume increased by up to 129%, and drive duration increased by up to 25%. In flight, data collected over 3.6 km and 149 drives confirmed a reduction in wheel current, correlated with wheel torque, of 18.7%. The new algorithm proved to use fewer resources in flight than ground estimates suggested, as only a 10% increase in drive duration and double the drive data volume were experienced. These data indicate the promise of the new algorithm to extend the life of the wheels for the Curiosity rover. This paper describes the algorithm, its ground testing campaign and associated challenges, and its validation, implementation, and performance in flight.     

基于滑转率的六轮纵列式月球车驱动控制研究

基于车轮滑转率和车轮地面力学,研究了月球车在松软月面行驶时的车轮过度下陷问题.将 月球车车轮下陷和车轮—土壤作用力表达为车轮滑转率的函数,结合车辆地面力学理论并考 虑纵列式车轮多通过性土壤参数的修正,建立了月球车的动力学模型.判断车轮是否发生过 度下陷的标准为土壤所提供给驱动轮的土壤推力能否克服土壤对车轮的阻力.利用建立的动 力学模型,计算出能够保证车轮不会过度下陷的期望滑转率.考虑到月球车动力学系统的非 线性和不确定性,设计了以车轮滑转率为状态变量的滑模驱动控制器.仿真结果表明,采用 该控制器可以较快地跟踪期望滑转率,避免车轮的过度滑转下陷,保证月球车能够在软质路 面上正常行驶.     

Equilibrium analysis of multi-limbs walking and climbing robots

The paper discusses the complex problem of assessing online the static equilibrium of statically-indeterminate climbing and walking robots (CLAWARs) with quasi-static locomotion. The method proposed is general and works for whatever number of legs and ropes operated by actuated winches connecting the robot to the environment. The configuration of the robot is assigned. First, the compliance of the robot body, of the legs and the compliances of the ground and the ropes are modeled as localized elasticities. The static equilibrium problem of the resulting model is statically-determinate under the hypothesis that the foot and rope points (where the ropes are fixed to the robot body) are joined to the ground by bilateral constraints. Since these constraints are unilateral (the feet are contact points and can detach from the ground, and the ropes can become slack), it is necessary to apply an iterative solving procedure in order to solve the static equilibrium problem. The method presented in the paper is a fast and effective alternative to nonlinear analysis of a finite element model of the robot at any assigned configuration. As an example, we consider the case of the heavy-duty CLAWAR Roboclimber.     

N人合作博弈的Nash及演化均衡稳定策略分析

在有限理性的基础上,对N人合作博弈的对称Nash均衡进行了分析,并引入演化博弈理论分析了参与人的演化均衡稳定策略,得到了不同策略选择下的均衡点。进而应用生物复制动态理论对离散时间及连续时间下的复制动态稳定集进行了研究。最后通过实例说明了该方法在博弈均衡选择上的有效性。     

复杂网络环境下的路由方法研究

与规则网和随机网相比,复杂网络能更好地刻画和描述网络的特征,而路由策略是信息网络信息分发和交换最重要的手段之一。近年来,复杂网络中的路由受到研究人员的高度关注。通过深入研究和讨论现有复杂网络中的路由策略,包括基于传统路由方法的复杂网络路由、基于生物学行为的复杂网络路由以及基于社会学行为的复杂网络路由,提出了进一步研究的方向。     

蠕虫智能扩散形式化分析及权策略算法实现

抽象蠕虫扩散的一般过程,采用确定的有限自动机理论,对蠕虫扩散行为进行形式化描述。建立智能扩散自动机模型,为研究蠕虫扩散过程提供了一种直观的形式化手段。提出加权树策略,基于该策略设计智能扩散模型并详细阐述权策略的核心算法,描述蠕虫智能扩散的本质特征和执行过程。形式论证结果表明,该模型能够有效地刻画智能扩散的特征,实现基于堆遍历加权策略的扩散仿真。     

Slippage estimation and compensation for planetary exploration rovers. State of the art and future challenges

Future lunar/planetary exploration missions will demand mobile robots with the capability of reaching more challenging science targets and driving farther per day than the current Mars rovers. Among other improvements, reliable slippage estimation and compensation strategies will play a key role in enabling a safer and more efficient navigation. This paper reviews and discusses this body of research in the context of planetary exploration rovers. Previously published state‐of‐the‐art methods that have been validated through field testing are included as exemplary results. Limitations of the current techniques and recommendations for future developments and planetary missions close the survey.     

校园网络的性能监视与安全对策分析

随着校园计算机网络通讯的飞速发展和应用的不断普及,网络安全越来越受到人们的重视。本文主要分析了如何对校园网络性能进行监视与优化,并从密码安全、系统安全、共享目录安全和木马防范方面,对校园网络安全进行了初步探索。     

校园网络的性能监视与安全对策分析

随着校园计算机网络通讯的飞速发展和应用的不断普及,网络安全越来越受到人们的重视。本文主要分析了如何对校园网络性能进行监视与优化,并从密码安全、系统安全、共享目录安全和木马防范方面,对校园网络安全进行了初步探索。     

基于滚动窗策略的岸桥集卡联合调度问题研究*

为应对集装箱码头突发事件的发生,采用滚动窗策略研究岸桥集卡的联合调度问题,在每个窗口内建立以最小化最大完工时间为目标的数学模型,并用遗传算法进行求解。在此基础上,讨论了以固定任务数量及固定时间长度为滚动窗口的情况,对比发现以时间为窗口的滚动窗策略更为适用。并分析了系统发生岸桥故障时滚动窗策略的性能,结果表明滚动窗策略能很好地应对突发事件。最后并将其与已有的动态调度研究成果作比较分析。     

分合粒子群优化算法*

基于社会系统中普遍存在“分久必合,合久必分”的现象,提出了基于分合思想的粒子群优化算法。分策略提高了演化群体的多样性,克服了粒子群优化算法局部收敛的缺陷。合策略吸取了不同群体的优良特性,提高了算法的全局搜索能力。函数优化的仿真结果证明了算法的有效性。     

State estimation and traversability map construction method of a quadruped robot on soft uneven terrain

Quadruped robots show excellent application prospects in complex environment detection and rescue. At present, scholars mainly focus on quadruped walking in rigid environments. However, quadruped robots often need to pass through uneven and soft unconstructed terrains, prone to slip and impact. The mismatch between the planned foothold position and the real one resulting from environmental uncertainties makes the robot unstable. In this paper, the state estimation and traversability map construction methods are proposed for quadruped robots to achieve stable walking in an unstructured environment, especially on soft terrains. First, the Error-state Kalman Filter (ErKF) is extended by optimizing the leg odometry information to get an accurate robot state, especially in soft, uneven terrain. The ErKF method fuses the sensor data from the inertial measurement unit, laser, camera, and leg odometry. The leg odometry is optimized by considering the foot slippage, which easily occurs in soft uneven terrains. Then, the unstructured environment is parameterized and modeled by the terrain inclination, roughness, height, and stiffness. A traversability map, which is essential for robot path and foothold planning in autonomous movement, is constructed with the above parameters. Finally, the proposed method is verified by simulation and experiments. The results show that the quadruped robot can walk stably on different soft and uneven terrains.