This work proposes a force control strategy with prescribed transient performance for the legs of a wheel-legged robotic system to realize the posture adjustment on uneven roads. A dynamic model of the robotic system is established with the body postures as inputs and the leg forces as outputs, such that the desired forces for the wheel-legs are calculated by the posture reference and feedback. Based on the funnel control scheme, the legs realize force tracking with prescribed transient performance. To improve the robustness of the force control system, an event-based mechanism is designed for the online segment of the funnel function. As a result, the force tracking error of the wheel-leg evolves inside the performance funnel with proved convergence. The absence of Zeno behavior for the event-triggering condition is also guaranteed. The proposed control scheme is applied to the wheel-legged physical prototype for the performance of force tracking and posture adjustment. Multiple comparative experimental results are presented to validate the stability and effectiveness of the proposed methodology.
In this paper, we propose a novel approach on controlling wheel-legged quadrupedal robots using pose optimization and force control via quadratic programming (QP). Our method allows the robot to leverage the whole-body motion and the wheel actuation to roll over high obstacles while keeping the wheel torques to navigate the terrain while keeping the wheel traction and balancing the robot body. In detail, we first present a linear rigid body dynamics with wheels that can be used for real-time balancing control of wheel-legged robots. We then introduce an effective pose optimization method for w…
Politecnico di Milano（米兰理工大学）；Istituto Italiano di Tecnologia（意大利技术研究院）
Hybrid wheeled-legged locomotion is a navigation paradigm only recently opened up by novel robotic designs,e.g. the centaur-type humanoid CENTAURO [1] or the quadruped ANYmal [2] in its configuration featuring non-steerable wheels. The term Hybrid Locomotion is hereafter used to indicate a particular type of locomotion, achieved with simultaneous and coordinate use of legs and wheels,see Fig. 1. Such choice stems at the intersection between legged locomotion and the simpler wheeled navigation, in order to get the best from both techniques: agility and ability to traverse uneven terrains from t…
ETH Zürich（苏黎世联邦理工学院）；Delft University of Technology（代尔夫特理工大学）；Boston Dynamics（波士顿动力公司）
Wheeled-legged robots have the potential for highly agile and versatile locomotion. The combination of legs and wheels might be a solution for any real-world application requiring rapid, and long-distance mobility skills on challenging terrain. In this paper, we present an online trajectory optimization framework for wheeled quadrupedal robots capable of executing hybrid walking-driving locomotion strategies. By breaking down the optimization problem into a wheel and base trajectory planning, locomotion planning for high dimensional wheeled-legged robots becomes more tractable, can be solved i…
Our paper proposes a model predictive controller as a single-task formulation that simultaneously optimizes wheel and torso motions. This online joint velocity and ground reaction force optimization integrates a kinodynamic model of a wheeled quadrupedal robot. It defines the single rigid body dynamics along with the robot's kinematics while treating the wheels as moving ground contacts. With this approach, we can accurately capture the robot's rolling constraint and dynamics, enabling automatic discovery of hybrid maneuvers without needless motion heuristics. The formulation's generality thro…
Legged robots have the ability to adapt their walking posture to navigate confined spaces due to their high degrees of freedom. However, this has not been exploited in most common multilegged platforms. This paper presents a deformable bounding box abstraction of the robot model, with accompanying mapping and planning strategies, that enable a legged robot to autonomously change its body shape to navigate confined spaces. The mapping is achieved using robot-centric multi-elevation maps generated with distance sensors carried by the robot. The path planning is based on the trajectory optimisati…
Southern University of Science and Technology（南方科技大学）
This article presents the design, implementation, and performance evaluation of SWheg, a novel modular wheel-leg transformable robot family with minimalist actuator realization. SWheg takes advantage of both wheeled and legged locomotion by seamlessly integrating them on a single platform. In contrast to other designs that use multiple actuators, SWheg uses only one actuator to drive the transformation of all the wheel-leg modules in sync. This means an N-legged SWheg robot requires only N+1 actuators, which can significantly reduce the cost and malfunction rate of the platform. The tendon-dri…
MUJICA: Multi-skill Unified Joint Integration of Control Architecture for Wheeled-Legged Robots
College of Intelligent Robotics and Advanced Manufacturing, Fudan University（智能机器人与先进制造学院，复旦大学）；Power China Huadong Engineering Corporation Limited（中国电力工程顾问集团华东分公司）
X2-N: A Transformable Wheel-legged Humanoid Robot with Dual-mode Locomotion and Manipulation
Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology（香港理工大学电子与计算机工程系）；X-lab Department, Agibot Innovation Company（阿吉博创新公司X实验室）
This paper presents the design, analysis, and performance evaluation of an omnidirectional transformable wheel-leg robot called OmniWheg. We design a novel mechanism consisting of a separable omni-wheel and 4-bar linkages, allowing the robot to transform between omni-wheeled and legged modes smoothly. In wheeled mode, the robot can move in all directions and efficiently adjust the relative position of its wheels, while it can overcome common obstacles in legged mode, such as stairs and steps. Unlike other articles studying whegs, this implementation with omnidirectional wheels allows the corre…
KYON: Semi-Modular Wheel-Legged Quadruped With Agile Bimanual Capability
Humanoids and Human Centered Mechatronics, Fondazione Istituto Italiano di Tecnologia（人机一体化机械系统，意大利理工研究院）；Advanced Robotics Facility, Fondazione Istituto Italiano di Tecnologia（先进机器人设施，意大利理工研究院）
National Institute of Advanced Industrial Science and Technology (AIST)（产业技术综合研究所（AIST））；Macquarie University（麦考瑞大学）
Spotting signal patterns with varying lengths has been still an open problem in the literature. In this study, we describe a signal pattern recognition approach for continuous and simultaneous classification of a tracked hand's posture and gestures and map them to steering commands for control of a robotic wheelchair. The developed methodology not only affords 100\% recognition accuracy on a streaming signal for continuous recognition, but also brings about a new perspective for building a training dictionary which eliminates human intervention to spot the gesture or postures on a training sig…
Arm-Constrained Curriculum Learning for Loco-Manipulation of the Wheel-Legged Robot
The Hong Kong University of Science and Technology (Guangzhou)（香港科技大学（广州））；Institute for AI Industry Research (AIR), Tsinghua University（清华大学人工智能产业研究院）；Tsinghua University（清华大学）；Harbin Institute of Technology（哈尔滨工业大学）；Xi’an Jiaotong-Liverpool University（西交利物浦大学）
Whole-body Motion Control of an Omnidirectional Wheel-Legged Mobile Manipulator via Contact-Aware Dynamic Optimization
State Key Laboratory of Intelligent Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology（智能制造装备与技术国家重点实验室，机械科学与工程学院，华中科技大学）
Mobile robot navigation in complex and dynamic environments is a challenging but important problem. Reinforcement learning approaches fail to solve these tasks efficiently due to reward sparsities, temporal complexities and high-dimensionality of sensorimotor spaces which are inherent in such problems. We present a novel approach to train action policies to acquire navigation skills for wheel-legged robots using deep reinforcement learning. The policy maps height-map image observations to motor commands to navigate to a target position while avoiding obstacles. We propose to acquire the multif…
Terrain-Awared LiDAR-Inertial Odometry for Legged-Wheel Robots Based on Radial Basis Function Approximation
School of Automation and Intelligent Sensing, Institute of Medical Robotics, Shanghai Jiao Tong University, and Key Laboratory of System Control and Information Processing, Ministry of Education（自动化与智能感知学院、医学机器人研究院、上海交通大学，系统控制与信息处理重点实验室）
We show dynamic locomotion strategies for wheeled quadrupedal robots, which combine the advantages of both walking and driving. The developed optimization framework tightly integrates the additional degrees of freedom introduced by the wheels. Our approach relies on a zero-moment point based motion optimization which continuously updates reference trajectories. The reference motions are tracked by a hierarchical whole-body controller which computes optimal generalized accelerations and contact forces by solving a sequence of prioritized tasks including the nonholonomic rolling constraints. Our…
Wheeled-legged robots combine the efficiency of wheeled robots when driving on suitably flat surfaces and versatility of legged robots when stepping over or around obstacles. This paper introduces a planning and control framework to realise dynamic locomotion for wheeled biped robots. We propose the Cart-Linear Inverted Pendulum Model (Cart-LIPM) as a template model for the rolling motion and the under-actuated LIPM for contact changes while walking. The generated motion is then tracked by an inverse dynamic whole-body controller which coordinates all joints, including the wheels. The framewor…
Agriculture is currently undergoing a robotics revolution, but robots using wheeled or treads suffer from known disadvantages: they are unable to move over rubble and steep or loose ground, and they trample continuous strips of land thereby reducing the viable crop area. Legged robots offer an alternative, but existing commercial legged robots are complex, expensive, and hard to maintain. We propose the use of multilegged robots using low-degree-of-freedom (low-DoF) legs and demonstrate our approach with a lawn pest control task: picking dandelions using our inexpensive and easy to fabricate B…
WAVE-Go: World-Model Navigation with Adaptive Execution for Wheel-Legged Robots
Beijing Institute of Technology（北京理工大学）；The University of Hong Kong（香港大学）；GAC R&D Center（广汽研究院）；LimX Dynamics；Beijing Academy of Artificial Intelligence (BAAI)（北京人工智能研究院）
S2M-Trek: From Single to Multi-Sphere Transport via Per-Frame Deep Sets on a Wheel-Legged Robot
School of Mechanical Science and Engineering, Huazhong University of Science and Technology（华中科技大学机械科学与工程学院）；School of Mathematics, Harbin Institute of Technology（哈尔滨工业大学数学学院）
Dynamics, stability, and energy efficiency of an energy-recycling rimless wheel with spring-clutch legs
Department of Mechanical Engineering and Robotics, Guangdong Technion-Israel Institute of Technology（广东以色列理工学院机械工程与机器人系）；Faculty of Mechanical Engineering, Technion-Israel Institute of Technology（以色列理工学院机械工程学院）；Department of Applied Electronics, Faculty of Advanced Engineering, Tokyo University of Science（东京理科大学先进工学部应用电子系）
Autonomous Legged Mobile Manipulation for Lunar Surface Operations via Constrained Reinforcement Learning
Department of Computer Sciences and Artificial Intelligence, University of Alicante（计算机科学与人工智能系，阿利坎特大学）；Department of Physics, Systems Engineering, and Signal Theory, University of Alicante（物理、系统工程与信号理论系，阿利坎特大学）；Department of Systems and Automatics Engineering, University of Málaga（系统与自动工程系，马拉加大学）
An attached arm can significantly increase the applicability of legged robots to several mobile manipulation tasks that are not possible for the wheeled or tracked counterparts. The standard hierarchical control pipeline for such legged manipulators is to decouple the controller into that of manipulation and locomotion. However, this is ineffective. It requires immense engineering to support coordination between the arm and legs, and error can propagate across modules causing non-smooth unnatural motions. It is also biological implausible given evidence for strong motor synergies across limbs.…
Seq-DeepIPC: Sequential Sensing for End-to-End Control in Legged Robot Navigation
Department of Computer Science and Electronics, Universitas Gadjah Mada（计算机科学与电子系，加查马达大学）；Department of Computer Science and Engineering, Toyohashi University of Technology（计算机科学与工程系，东福冈技术大学）
Design and Dimensional Optimization of Legged Structures for Construction Robots
Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences（中国科学院深圳先进技术研究院）；School of Transportation and Logistics Engineering, Wuhan University of Technology（武汉理工大学交通运输与物流工程学院）；University of Chinese Academy of Sciences（中国科学院大学）
Learning to Recover: Dynamic Reward Shaping with Wheel-Leg Coordination for Fallen Robots
Humanoids and Human-Centered Mechatronics (HHCM), Istituto Italiano di Tecnologia（人类oids与人本机电系统（HHCM），意大利技术研究所）；Ph.D. Program of National Interest in Robotics and Intelligent Machines (DRIM), University of Genova（机器人与智能机器国家利益博士项目（DRIM），热那亚大学）；Department of Computer Science, University College London（计算机科学系，伦敦大学学院）
University of Louisiana at Lafayette（路易斯安那大学拉斐特分校）
Legged systems have many advantages when compared to their wheeled counterparts. For example, they can more easily navigate extreme, uneven terrain. However, there are disadvantages as well, particularly the difficulty seen in modeling the nonlinearities of the system. Research has shown that using flexible components within legged locomotive systems improves performance measures such as efficiency and running velocity. Because of the difficulties encountered in modeling flexible systems, control methods such as reinforcement learning can be used to define control strategies. Furthermore, rein…
Autonomous UAV-Quadruped Docking in Complex Terrains via Active Posture Alignment and Constraint-Aware Control
College of Electronics and Information Engineering, Tongji University（同济大学电子与信息工程学院）；Frontiers Science Center for Intelligent Autonomous Systems, Shanghai（上海智能自主系统前沿科学中心）；School of Logistics Engineering, Shanghai Maritime University（上海 Maritime University物流工程学院）；State Key Laboratory of Autonomous Intelligent Unmanned Systems, Shanghai（上海自主智能无人系统国家重点实验室）
Legged Autonomous Surface Science In Analogue Environments (LASSIE): Making Every Robotic Step Count in Planetary Exploration
Collaborative Robotics and Intelligent Systems Institute, Oregon State University（协作机器人与智能系统研究所，俄勒冈州立大学）；Department of Geology and Geophysics, Texas A&M University（地质与地球物理系，德克萨斯大学）；Department of Electrical and Computer Engineering, University of Southern California（电气与计算机工程系，南加州大学）；Department of Earth and Environmental Science, University of Pennsylvania（地球与环境科学系，宾夕法尼亚大学）；Department of Astronomy and Planetary Science, Northern Arizona University（天文学与行星科学系，北方亚利桑那大学）；School of Earth and Atmospheric Sciences, Georgia Institute of Technology（地球与大气科学学院，佐治亚理工学院）；NASA Marshall Space Flight Center（美国国家航空航天局马歇尔航天飞行中心）；NASA Johnson Space Center（美国国家航空航天局约翰逊航天中心）；Department of Electrical and Systems Engineering, University of Pennsylvania（电气与系统工程系，宾夕法尼亚大学）；Department of Psychology, Temple University（心理学系， Temple 大学）
NASA Jet Propulsion Laboratory, California Institute of Technology（美国国家航空航天局喷气推进实验室，加州理工学院）；University of Goettingen, University Medical Center Goettingen（哥廷根大学，哥廷根大学医学中心）；Institute for Robotics and Intelligent Machines, Georgia Institute of Technology（佐治亚理工学院机器人与智能机器研究所）；Swiss Federal Institute of Technology (ETH Zürich)（苏黎世联邦理工学院）；California Institute of Technology（加州理工学院）
Legged robots can traverse a wide variety of terrains, some of which may be challenging for wheeled robots, such as stairs or highly uneven surfaces. However, quadruped robots face stability challenges on slippery surfaces. This can be resolved by adjusting the robot's locomotion by switching to more conservative and stable locomotion modes, such as crawl mode (where three feet are in contact with the ground always) or amble mode (where one foot touches down at a time) to prevent potential falls. To tackle these challenges, we propose an approach to learn a model from past robot experience for…
Dynamically Extensible and Retractable Robotic Leg Linkages for Multi-task Execution in Search and Rescue Scenarios
Mechanical and Aerospace Engineering Department, University of California, San Diego（加州大学圣地亚哥分校机械与航空航天工程系）；Electrical and Computer Engineering Department, University of California, San Diego（加州大学圣地亚哥分校电气与计算机工程系）
