TeLeMan: Teleoperation for Legged Robot Loco-Manipulation using Wearable IMU-based Motion Capture

Human life is invaluable. When dangerous or life-threatening tasks need to be completed, robotic platforms could be ideal in replacing human operators. Such a task that we focus on in this work is the Explosive Ordnance Disposal. Robot telepresence has the potential to provide safety solutions, given that mobile robots have shown robust capabilities when operating in several environments. However, autonomy may be challenging and risky at this stage, compared to human operation. Teleoperation could be a compromise between full robot autonomy and human presence. In this paper, we present a relatively cheap solution for telepresence and robot teleoperation, to assist with Explosive Ordnance Disposal, using a legged manipulator (i.e., a legged quadruped robot, embedded with a manipulator and RGB-D sensing). We propose a novel system integration for the non-trivial problem of quadruped manipulator whole-body control. Our system is based on a wearable IMU-based motion capture system that is used for teleoperation and a VR headset for visual telepresence. We experimentally validate our method in real-world, for loco-manipulation tasks that require whole-body robot control and visual telepresence

A Novel Design and Evaluation of a Dactylus-Equipped Quadruped Robot for Mobile Manipulation

Quadruped robots are usually equipped with additional arms for manipulation, negatively impacting price and weight. On the other hand, the requirements of legged locomotion mean that the legs of such robots often possess the needed torque and precision to perform manipulation. In this paper, we present a novel design for a small-scale quadruped robot equipped with two leg-mounted manipulators inspired by crustacean chelipeds and knuckle-walker forelimbs. By making use of the actuators already present in the legs, we can achieve manipulation using only 3 additional motors per limb. The design enables the use of small and inexpensive actuators relative to the leg motors, further reducing cost and weight. The moment of inertia impact on the leg is small thanks to an integrated cable/pulley system. As we show in a suite of tele-operation experiments, the robot is capable of performing single- and dual-limb manipulation, as well as transitioning between manipulation modes. The proposed design performs similarly to an additional arm while weighing and costing 5 times less per manipulator and enabling the completion of tasks requiring 2 manipulators.Comment: 6 pages, 10 figures, updated layout to fit in margins and corrected typos, accepted to the 2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2022

로봇 시스템의 설계 및 동작 동시 최적화

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 기계공학부, 2020. 8. 박종우.A robot design has the potential for numerous combinations of the components such as the actuators, links, joints, etc. Therefore, a process of finding a good design is a challenging problem even for the robot experts. To overcome this difficulty, we present an optimization framework for the morphological shape of a robot, considering its motion. Both the design and motion parameters can be simultaneously optimized for specific tasks by our methodology. In the space where the design and motion parameters are combined, our framework seeks the steepest direction that reduces the objective function on the constraint manifold. To overcome the flaws of the previous studies, we utilize the recently discovered recursive differential dynamics, which informs of the analytic relationship between the variation of joint torques and design parameters, thus our framework brings faster and more accurate optimization results. We validate our optimization framework through two numerical experiments: the 2-R planar manipulator with a given end-effector trajectory and the quadruped robot with a locomotion task.로봇 디자인에는 액츄에이터, 링크, 관절 등과 같은 구성요소의 수많은 조합 가능성이 존재한다. 따라서, 좋은 로봇 디자인을 찾는 과정은 전문가에게도 어려운 문제이다. 위 문제점을 극복하기 위해 로봇의 동작을 고려하여 형태를 최적화하는 방법론을 제시한다. 제시된 방법론을 통해 특정 작업을 위한 로봇 형태 및 동작의 동시 최적화가 가능하다. 위 방법론은 형태 및 동작 변수가 결합된 공간 상에서 목적함수를 가장 많이 감소시키는 구속조건 매니폴드 상에서의 방향을 찾아 최적화를 진행한다. 이전 연구들의 결점을 극복하기 위해 우리는 최근 개발된 반복 미분 동역학(recursive differential dynamics) 알고리즘을 사용한다. 이 알고리즘을 통해 관절 토크 변화와 형태 변화 사이의 해석적 관계를 계산할 수 있다. 따라서, 제시된 방법론을 사용하면 더욱 빠르고 정확한 최적화 결과를 도출할 수 있다. 총 두 가지 수치적 실험을 통해 위 최적화 방법론을 검증하였다: 엔드이펙터가 주어진 궤적을 추종하는 2축 평면 매니퓰레이터, 4족로봇의 보행작업.1 Introduction 1 1.1 Design Optimization of Robotic Devices 1 1.2 Limitations of Previous Works 4 1.3 Main Contributions of This Thesis 5 2 Preliminaries 7 2.1 Lie Group Theory 7 2.1.1 SO(3) and SE(3) 8 2.1.2 Twists and Wrenches 10 2.1.3 Adjoint Mappings 10 2.2 Rigid Body Dynamics 11 2.2.1 Dynamics of a Single Rigid Body 11 2.2.2 Dynamics of Open Chains 12 2.2.3 Dynamics of Floating Bodies 14 2.3 Recursive Differential Dynamics 15 3 Simultaneous Design and Motion Optimization 18 3.1 Problem Definition 18 3.2 Optimization Parameters 20 3.2.1 Design Parameters 20 3.2.2 Motion Parameters 23 3.2.3 Constraints 24 3.2.4 Inertial Changes 26 3.3 Optimization Algorithm Description 27 4 Numerical Experiments31 4.1 2-R Planar Manipulator 31 4.1.1Experimental Settings 31 4.1.2Optimization Results 33 4.2 Quadruped Robot 36 4.2.1Experimental Settings 37 4.2.2Optimization Results 39 5 Conclusion 44 A Appendix 46 A.1 Local parametrization of the design 46 A.2 Design rule for the link 48 A.3 Derivative of the constraints 51 A.3.1 End-effector trajectory 51 A.3.2 Equations of motion of the base for quadruped robots 52 A.4 Laikago Specification 53 Bibliography 55 국문초록 60Maste

Kinematically-Decoupled Impedance Control for Fast Object Visual Servoing and Grasping on Quadruped Manipulators

We propose a control pipeline for SAG (Searching, Approaching, and Grasping) of objects, based on a decoupled arm kinematic chain and impedance control, which integrates image-based visual servoing (IBVS). The kinematic decoupling allows for fast end-effector motions and recovery that leads to robust visual servoing. The whole approach and pipeline can be generalized for any mobile platform (wheeled or tracked vehicles), but is most suitable for dynamically moving quadruped manipulators thanks to their reactivity against disturbances. The compliance of the impedance controller makes the robot safer for interactions with humans and the environment. We demonstrate the performance and robustness of the proposed approach with various experiments on our 140 kg HyQReal quadruped robot equipped with a 7-DoF manipulator arm. The experiments consider dynamic locomotion, tracking under external disturbances, and fast motions of the target object.Comment: Accepted as contributed paper at 2023 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2023

Legged Robots for Object Manipulation: A Review

Legged robots can have a unique role in manipulating objects in dynamic, human-centric, or otherwise inaccessible environments. Although most legged robotics research to date typically focuses on traversing these challenging environments, many legged platform demonstrations have also included "moving an object" as a way of doing tangible work. Legged robots can be designed to manipulate a particular type of object (e.g., a cardboard box, a soccer ball, or a larger piece of furniture), by themselves or collaboratively. The objective of this review is to collect and learn from these examples, to both organize the work done so far in the community and highlight interesting open avenues for future work. This review categorizes existing works into four main manipulation methods: object interactions without grasping, manipulation with walking legs, dedicated non-locomotive arms, and legged teams. Each method has different design and autonomy features, which are illustrated by available examples in the literature. Based on a few simplifying assumptions, we further provide quantitative comparisons for the range of possible relative sizes of the manipulated object with respect to the robot. Taken together, these examples suggest new directions for research in legged robot manipulation, such as multifunctional limbs, terrain modeling, or learning-based control, to support a number of new deployments in challenging indoor/outdoor scenarios in warehouses/construction sites, preserved natural areas, and especially for home robotics.Comment: Preprint of the paper submitted to Frontiers in Mechanical Engineerin

Performance and Usability Evaluation Scheme for Mobile Manipulator Teleoperation

This article presents a standardized human–robot teleoperation interface (HRTI) evaluation scheme for mobile manipulators. Teleoperation remains the predominant control type for mobile manipulators in open environments, particularly for quadruped manipulators. However, mobile manipulators, especially quadruped manipulators, are relatively novel systems to be implemented in the industry compared to traditional machinery. Consequently, no standardized interface evaluation method has been established for them. The proposed scheme is the first of its kind in evaluating mobile manipulator teleoperation. It comprises a set of robot motion tests, objective measures, subjective measures, and a prediction model to provide a comprehensive evaluation. The motion tests encompass locomotion, manipulation, and a combined test. The duration for each trial is collected as the response variable in the objective measure. Statistical tools, including mean value, standard deviation, and T-test, are utilized to cross-compare between different predictor variables. Based on an extended Fitts' law, the prediction model employs the time and mission difficulty index to forecast system performance in future missions. The subjective measures utilize the NASA-task load index and the system usability scale to assess workload and usability. Finally, the proposed scheme is implemented on a real-world quadruped manipulator with two widely-used HRTIs, the gamepad and the wearable motion capture system

Modeling and Control of Multi-Arm and Multi-Leg Robots: Compensating for Object Dynamics during Grasping

Dehio N, Smith J, Wigand DL, et al. Modeling & Control of Multi-Arm and Multi-Leg Robots: Compensating for Object Dynamics during Grasping. In: IEEE/RSJ Int. Conf. on Robotics and Automation. 2018