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Contact detection with multi-information fusion for quadruped robot locomotion under unstructured terrain

《机械工程前沿（英文）》 2023年第18卷第3期 doi: 10.1007/s11465-023-0760-4

摘要： Reliable foot-to-ground contact state detection is crucial for the locomotion control of quadruped robots in unstructured environments. To improve the reliability and accuracy of contact detection for quadruped robots, a detection approach based on the probabilistic contact model with multi-information fusion is presented to detect the actual contact states of robotic feet with the ground. Moreover, a relevant control strategy to address unexpected early and delayed contacts is planned. The approach combines the internal state information of the robot with the measurements from external sensors mounted on the legs and feet of the prototype. The overall contact states are obtained by the classification of the model-based predicted probabilities. The control strategy for unexpected foot-to-ground contacts can correct the control actions of each leg of the robot to traverse cluttered environments by changing the contact state. The probabilistic model parameters are determined by testing on the single-leg experimental platform. The experiments are conducted on the experimental prototype, and results validate the contact detection and control strategy for unexpected contacts in unstructured terrains during walking and trotting. Compared with the body orientation under the time-based control method regardless of terrain, the root mean square errors of roll, pitch, and yaw respectively decreased by 60.07%, 54.73%, and 64.50% during walking and 73.40%, 61.49%, and 61.48% during trotting.

关键词： multi-information fusion contact detection quadruped robot probabilistic contact model unstructured terrain

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Transmission probability method based on triangle meshes for solving the unstructured geometry neutron

WU Hongchun, LIU Pingping, ZHOU Yongqiang, CAO Liangzhi

《能源前沿（英文）》 2007年第1卷第2期页码 158-166 doi: 10.1007/s11708-007-0020-z

摘要： The fuel assembly or core with unstructured geometry is frequently used in the advanced reactor. To calculate the fuel assembly, the transmission probability method (TPM) is widely used. However, the rectangular or hexagonal meshes are mainly used in the TPM codes for the normal core structure. The triangle meshes are most useful for expressing the complicated unstructured geometry. Even though the finite element method and Monte-Carlo method are well suited for solving the unstructured geometry problem, they are very time-consuming. Therefore, a TPM code based on the triangle meshes is developed here. This code was applied to the hybrid fuel geometry, and compared with the results of the MCNP code and other codes. The results of the comparison were consistent with each other. The TPM with triangle meshes can thus be applied to the two-dimensional arbitrary fuel assembly.

关键词： unstructured geometry assembly transmission probability TPM rectangular

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Enhancing the terrain adaptability of a multirobot cooperative transportation system via novel connectors

《机械工程前沿（英文）》 2023年第18卷第3期 doi: 10.1007/s11465-023-0754-2

摘要： Given limited terrain adaptability, most existing multirobot cooperative transportation systems (MRCTSs) mainly work on flat pavements, restricting their outdoor applications. The connectors’ finite deformation capability and the control strategies’ limitations are primarily responsible for this phenomenon. This study proposes a novel MRCTS based on tracked mobile robots (TMRs) to improve terrain adaptability and expand the application scenarios of MRCTSs. In structure design, we develop a novel 6-degree-of-freedom passive adaptive connector to link multiple TMRs and the transported object (the communal payload). In addition, the connector is set with sensors to measure the position and orientation of the robot with respect to the object for feedback control. In the control strategy, we present a virtual leader–physical follower collaborative paradigm. The leader robot is imaginary to describe the movement of the entire system and manage the follower robots. All the TMRs in the system act as follower robots to transport the object cooperatively. Having divided the whole control structure into the leader robot level and the follower robot level, we convert the motion control of the two kinds of robots to trajectory tracking control problems and propose a novel double closed-loop kinematics control framework. Furthermore, a control law satisfying saturation constraints is derived to ensure transportation stability. An adaptive control algorithm processes the wheelbase uncertainty of the TMR. Finally, we develop a prototype of the TMR-based MRCTS for experiments. In the trajectory tracking experiment, the developed MRCTS with the proposed control scheme can converge to the reference trajectory in the presence of initial tracking errors in a finite time. In the outdoor experiment, the proposed MRCTS consisting of four TMRs can successfully transport a payload weighing 60 kg on an uneven road with the single TMR’s maximum load limited to 15 kg. The experimental results demonstrate the effectiveness of the structural design and control strategies of the TMR-based MRCTS.

关键词： multirobot system cooperative transportation terrain adaptability trajectory tracking collaborative paradigm uneven road

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Footholds optimization for legged robots walking on complex terrain

《机械工程前沿（英文）》 2023年第18卷第2期 doi: 10.1007/s11465-022-0742-y

摘要： This paper proposes a novel continuous footholds optimization method for legged robots to expand their walking ability on complex terrains. The algorithm can efficiently run onboard and online by using terrain perception information to protect the robot against slipping or tripping on the edge of obstacles, and to improve its stability and safety when walking on complex terrain. By relying on the depth camera installed on the robot and obtaining the terrain heightmap, the algorithm converts the discrete grid heightmap into a continuous costmap. Then, it constructs an optimization function combined with the robot’s state information to select the next footholds and generate the motion trajectory to control the robot’s locomotion. Compared with most existing footholds selection algorithms that rely on discrete enumeration search, as far as we know, the proposed algorithm is the first to use a continuous optimization method. We successfully implemented the algorithm on a hexapod robot, and verified its feasibility in a walking experiment on a complex terrain.

关键词： footholds optimization legged robot complex terrain adapting hexapod robot locomotion control

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Discrete ordinates method for three-dimensional neutron transport equation based on unstructured-meshes

JU Haitao, WU Hongchun, YAO Dong, XIAN Chunyu

《能源前沿（英文）》 2008年第2卷第2期页码 179-182 doi: 10.1007/s11708-008-0024-3

摘要： A discrete ordinates method for a three-dimensional first-order neutron transport equation based on unstructured-meshes that avoids the singularity of the second-order neutron transport equation in void regions was derived. The finite element variation equation was obtained using the least-squares method. A three-dimensional transport calculation code was developed. Both the triangular-z and the tetrahedron elements were included. The numerical results of some benchmark problems demonstrated that this method can solve neutron transport problems in unstructured-meshes very well. For most problems, the error of the eigenvalue and the angular flux is less than 0.3% and 3.0% respectively.

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Terrain classification and adaptive locomotion for a hexapod robot Qingzhui

Yue ZHAO, Feng GAO, Qiao SUN, Yunpeng YIN

《机械工程前沿（英文）》 2021年第16卷第2期页码 271-284 doi: 10.1007/s11465-020-0623-1

摘要： Legged robots have potential advantages in mobility compared with wheeled robots in outdoor environments. The knowledge of various ground properties and adaptive locomotion based on different surface materials plays an important role in improving the stability of legged robots. A terrain classification and adaptive locomotion method for a hexapod robot named Qingzhui is proposed in this paper. First, a force-based terrain classification method is suggested. Ground contact force is calculated by collecting joint torques and inertial measurement unit information. Ground substrates are classified with the feature vector extracted from the collected data using the support vector machine algorithm. Then, an adaptive locomotion on different ground properties is proposed. The dynamic alternating tripod trotting gait is developed to control the robot, and the parameters of active compliance control change with the terrain. Finally, the method is integrated on a hexapod robot and tested by real experiments. Our method is shown effective for the hexapod robot to walk on concrete, wood, grass, and foam. The strategies and experimental results can be a valuable reference for other legged robots applied in outdoor environments.

关键词： terrain classification hexapod robot legged robot adaptive locomotion gait control

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深海钴结壳采集微地形探测技术实验研究

罗柏文,夏毅敏,王韬,白宏峰,王克智

《中国工程科学》 2010年第12卷第9期页码 78-83

摘要：

通过地表高程信息计算最佳采集深度是解决钴结壳开采贫化问题的关键技术之一。根据钴结壳的赋存环境和开采方法，提出了一种摆动式超声单波束微地形探测方法。为了检验该方法的可行性，成功搭建了实验台，并验证了该实验台的垂直探测精度可达到厘米级；提出了一种改进型数据加窗算法，进一步提高了高程异常值被剔除的准确性；提出了采用线性相关系数法解决支持向量线性与非线性回归的选择问题；提出并证明了高斯径向基参数σ可根据测线上的坡度、坡长信息来确定。

关键词：钴结壳超声微地形加窗支持向量

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Stability and agility: biped running over varied and unknown terrain

Yang YI,Zhi-yun LIN

《信息与电子工程前沿（英文）》 2015年第16卷第4期页码 283-292 doi: 10.1631/FITEE.1400284

摘要： We tackle the problem of a biped running over varied and unknown terrain. Running is a necessary skill for a biped moving fast, but it increases the challenge of dynamic balance, especially when a biped is running on varied terrain without terrain information (due to the difficulty and cost of obtaining the terrain information in a timely manner). To address this issue, a new dynamic indicator called the sustainable running criterion is developed. The main idea is to sustain a running motion without falling by maintaining the system states within a running-feasible set, instead of running on a periodic limit cycle gait in the traditional way. To meet the precondition of the criterion, the angular moment about the center of gravity (COG) is restrained close to zero at the end of the stance phase. Then to ensure a small state jump at touchdown on the unknown terrain, the velocity of the swing foot is restrained within a specific range at the end of the flight phase. Finally, the position and velocity of the COG are driven into the running-feasible set. A five-link biped with underactuated point foot is considered in simulations. It is able to run over upward and downward terrain with a height difference of 0.15 m, which shows the effectiveness of our control scheme.

关键词： Underactuated running biped Dynamic balance Varied and unknown terrain

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水利水电工程三维数字地形建模与分析

钟登华,李明超,王刚,郭享,吴康新

《中国工程科学》 2005年第7卷第7期页码 65-70

摘要：

以锦屏一级水电工程为例，分别利用Delaunay算法和多细节层次技术实现了坝区地形TIN模型和施工总布置区域巡航所需的多分辨率地形模型。并根据三维地质建模的特殊需要，引入了NURBS技术对TIN地形模型进行了简化，所获得的NURBS地形模型不仅存储量小，精度损失低，而且易于图形操作运算，便于可视化分析，满足多方面的要求。该模型的实现与成功应用，在很大程度上推动了水利水电工程向着数字化、可视化和智能化的方向发展。

关键词：数字地形模型不规则三角网细节层次 NURBS技术水利水电工程

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美国国防部先进研究项目局举办的机器人大挑战赛的参与和崎岖地面行走的滑雪式步态 Article

王宏飞, 李诗濛, 郑元芳

《工程（英文）》 2015年第1卷第1期页码 36-45 doi: 10.15302/J-ENG-2015006

摘要：

本文简要介绍了美国国防部先进研究项目局举办的机器人大挑战赛的历史，并将关注的焦点放在了2012机器人挑战赛上。作为该挑战赛DRC-HUBO队的成员，我们为完成崎岖地面的任务提出了不同的方法，如增大脚踏板、转换成四足行走等。同时，本文还介绍了一种帮助提高仿人机器人运动稳定性的新步态——滑雪式步态。本文对该步态的稳定性进行了分析，并利用稳定度裕量从两种备选的步进顺序（爬行-1和爬行-2）中进行选择。接下来，本文对滑雪式步态中冗余的闭链系统进行力/力矩分析，通过最小化总耗能量来确定关节力矩。根据稳定性分析和力/力矩分析，我们设计了一种手杖长度，使其可以支撑HUBO2仿人机器人平台稳定地实现爬行-2步态。最后，通过将本文的试验结果和两足步行进行对比，验证了滑雪式步态的可行性。同时，介绍了我队在该机器人挑战赛上的表现。

关键词：仿人机器人美国国防部先进研究项目局举办的机器人大挑战赛（DRC）崎岖地面行走滑雪式步态

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Numerical simulation of air flow field in high-pressure fan with splitter blades

LI Jianfeng, LU Junfu, ZHANG Hai, LIU Qing, YUE Guangxi

《能源前沿（英文）》 2008年第2卷第4期页码 438-442 doi: 10.1007/s11708-008-0085-3

摘要： For a deeper understanding of the flow characteristics in the high-pressure centrifugal blower of a fan of Model 9-26 with splitter blades, a three dimensional (3-D) numerical simulation of air flows in the fan was conducted with FLUENT software. The standard - turbulent model and unstructured grids were used. The computational fluid dynamics (CFD) results showed that the performance of a fan could be improved by adding the splitter blades in the channel among the leaf blades. Under operational conditions, with the presence of splitter blades, the air flow rate of the fan increased about 5% and the total pressure at the outlet of the fan increased about 10% on average. It was also found that the length of the splitter blades affected the air flow and pressure drop. There is an optimal value for the length. The simulation results provide helpful information for improving the fan performance.

关键词： splitter numerical simulation presence unstructured operational

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Wind tunnel test study on the wind pressure coefficient of claddings of high-rise buildings

Yong QUAN, Yi LIANG, Fei WANG, Ming GU

《结构与土木工程前沿（英文）》 2011年第5卷第4期页码 518-524 doi: 10.1007/s11709-011-0128-4

摘要： The area-averaged most unfavorable wind pressure coefficients (MUWPCs) on various regions of building surfaces and the influence of the side ratio and the terrain category were studied based on wind tunnel test data of scale models of typical high-rise buildings with rectangular cross-sections. The negative area-averaged MUWPCs in the middle-height edge areas generally increased with an increasing / side ratio. The area-averaged MUWPCs can be well fitted with a function of the average area reduced by the square of the building depth, . In addition, no unique pattern was found for the effect of the terrain category on the MUWPCs.

关键词： side ratio area-averaged pressure coefficients cladding terrain category

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Sagittal SLIP-anchored task space control for a monopode robot traversing irregular terrain

Haitao YU, Haibo GAO, Liang DING, Zongquan DENG

《机械工程前沿（英文）》 2020年第15卷第2期页码 193-208 doi: 10.1007/s11465-019-0569-3

摘要： As a well-explored template that captures the essential dynamical behaviors of legged locomotion on sagittal plane, the spring-loaded inverted pendulum (SLIP) model has been extensively employed in both biomechanical study and robotics research. Aiming at fully leveraging the merits of the SLIP model to generate the adaptive trajectories of the center of mass (CoM) with maneuverability, this study presents a novel two-layered sagittal SLIP-anchored (SSA) task space control for a monopode robot to deal with terrain irregularity. This work begins with an analytical investigation of sagittal SLIP dynamics by deriving an approximate solution with satisfactory apex prediction accuracy, and a two-layered SSA task space controller is subsequently developed for the monopode robot. The higher layer employs an analytical approximate representation of the sagittal SLIP model to form a deadbeat controller, which generates an adaptive reference trajectory for the CoM. The lower layer enforces the monopode robot to reproduce a generated CoM movement by using a task space controller to transfer the reference CoM commands into joint torques of the multi-degree of freedom monopode robot. Consequently, an adaptive hopping behavior is exhibited by the robot when traversing irregular terrain. Simulation results have demonstrated the effectiveness of the proposed method.

关键词： legged robots spring-loaded inverted pendulum task space control apex return map deadbeat control irregular terrain negotiation