Cable-Driven Actuation for Highly Dynamic Robotic Systems

This paper presents design and experimental evaluations of an articulated robotic limb called Capler-Leg. The key element of Capler-Leg is its single-stage cable-pulley transmission combined with a high-gap radius motor. Our cable-pulley system is designed to be as light-weight as possible and to additionally serve as the primary cooling element, thus significantly increasing the power density and efficiency of the overall system. The total weight of active elements on the leg, i.e. the stators and the rotors, contribute more than 60% of the total leg weight, which is an order of magnitude higher than most existing robots. The resulting robotic leg has low inertia, high torque transparency, low manufacturing cost, no backlash, and a low number of parts. Capler-Leg system itself, serves as an experimental setup for evaluating the proposed cable- pulley design in terms of robustness and efficiency. A continuous jump experiment shows a remarkable 96.5 % recuperation rate, measured at the battery output. This means that almost all the mechanical energy output used during push-off returned back to the battery during touch-down

Body Design Of Tendon-Driven Jumping Robot Using Single Actuator And Wire Set

Although a mechanism in which a single actuator and a wire passing through pulleys drive the joints is a strong candidate for realizing the dynamic behavior because of its appropriate weight and simple mechanism, the problem arises that the position of the pulley influences the dynamic behavior. This paper is focused on vertical jumping. In our research, we searched an appropriate set of positions of a pulley considering the practical development of the robot and derived the relationship between the position of the pulley and the force on the tips of the robot’s foot for jumping. Simulation results suggest the possibility that some sets of positions allow an error in the attachment of the pulley, and the derived relationship indicates that the ratio of the pulling force of wire and vertical force on the ground strongly constrain the position of the pulley

Development of Belt Harmonic Reducer for Reducing Link Moment of Inertia

학위논문(석사) -- 서울대학교대학원 : 융합과학기술대학원 지능정보융합학과, 2021.8. 박재흥.전기 모터는 빠른 제어 반응성과 상대적으로 용이한 에너지원 관리로 인해 현대 로봇 분야에서 가장 범용적으로 사용되는 액추에이터 중 하나이다. 그러나 높은 회전 속도 대비 부족한 가용 토크 범위 때문에, 대부분의 로봇 설계에서 토크를 증가시키는 감속기와 함께 적용된다. 특히, 큰 감속비와 높은 정밀도라는 장점으로 인해 파동 조화 감속기 일명 하모닉 기어는 여러 가지 로봇 설계에서 자주 사용된다. 그러나 하모닉 기어는 어려운 제조 공정 및 탄성체로 만들어진 동력 전달원 등으로 인하여 두께 제한 등 여러 가지 한계가 존재한다. 한편, 족형 로봇의 경우, 다리의 관성 모멘트가 제어 반응성에 영향을 줄 수 있으므로 각 관절에 모터와 감속기를 포함한 액추에이터를 직접 배치하기 어렵다. 또한, 감속기와 동시에 동력 전달 장치나 4절 링크를 사용하면 전체적인 부피가 커지고 무게가 무거워지는 단점이 존재한다. 본 논문에서는 체인, 타이밍 벨트 등의 동력 전달 장치로 탄성체를 모사하여 플렉스 스플라인을 대체하는 새로운 감속기를 제안한다. 특히, 벨트 하모닉 감속기의 원리를 사용하여, 동력 축과 관절 축을 분리함과 동시에 고감속비의 액추에이터를 적용할 수 있는 HABA-T(HArmonic Belt Applied Transmission)를 제시하였으며, 위치 추종 성능을 분석하여 관성 모멘트 감소가 필요한 링크에 설계 적용 가능성을 제시하였다.Electric motors are one of the most universally used actuators in the field of modern robots due to their rapid control responsivity and easy energy source management. However, they are applied with a speed reducer that increases the torque in most robot designs due to the insufficient torque range. In particular, harmonic gears are used in various robots due to the advantages of a large reduction ratio and high accuracy. However, there are various difficulties in manufacturing and the power transmission source as an elastic body such as thickness limitation. On the other hand, in a legged robot, in which the moment of inertia of the leg can affect control responsivity, it is difficult to directly place an actuator including a motor and a reducer in each joint. Also, using a power transmission device or a four-link with the reducer has the disadvantage that the overall volume is increased and the weight is heavier. In this paper, a novel reducer that replaces the flex spline with power transmission devices such as chains and timing belts by imitating an elastic body is proposed. In particular, HABA-T (HArmonic Belt Applied Transmission) using a belt harmonic reducing mechanism that can apply an actuator with a high reduction ratio while separating the actuator axis and the joint axis is proposed. And, the feasibility of the novel mechanism for applications that require reducing the moment of inertia was demonstrated by analyzing the position tracking performance.제 1 장 서 론 1 제 1 절 연구의 배경 및 동기 1 제 2 절 연구 동향 5 제 3 절 연구 목표 및 방법 9 제 2 장 체인을 활용한 하모닉 감속기 설계 11 제 1 절 기존 하모닉 감속기의 감속 원리 11 제 2 절 끈 형태의 동력 전달 장치의 감속 원리 12 제 3 절 체인을 활용한 하모닉 감속기 설계 13 제 3 장 관성모멘트 감소를 위한 감속 장치 설계 19 제 1 절 벨트 하모닉 감속기 작동 원리 19 제 2 절 벨트 하모닉 감속기 적용 분야 23 제 3 절 벨트 하모닉 감속기 이론적 한계점 26 제 4 절 한계 극복 방법 28 제 5 절 설계 31 제 4 장 위치 추종 성능 실험 33 제 1 절 실험 개요 및 구성 33 제 2 절 실험 결과 33 제 3 절 고찰 36 제 5 장 결론 39 참고문헌 41 Abstract 46석

Energetics and Passive Dynamics of Quadruped Robot Planar Running Gaits

Quadruped robots find application in military for load carrying over uneven terrain, humanitarian de-mining, and search and rescue missions. The energy required for quadruped robot locomotion needs to be supplied from on-board energy source which can be either electrical batteries or fuels such as gasolene/diesel. The range and duration of missions very much depend on the amount of energy carried, which is highly limited. Hence, energy efficiency is of paramount importance in building quadruped robots. Study of energy efficiency in quadruped robots not only helps in efficient design of quadruped robots, but also helps understand the biomechanics of quadrupedal animals. This thesis focuses on the energy efficiency of planar running gaits and presents: (a) derivation of cost of transport expressions for trot and bounding gaits, (b) advantages of articulated torso over rigid torso for quadruped robot, (c) symmetry based control laws for passive dynamic bounding and design for inherent stability, and (d) effect of asymmetry in zero-energy bounding gaits

Control of Bio-Inspired Sprawling Posture Quadruped Robots with an Actuated Spine

Sprawling posture robots are characterized by upper limb segments protruding horizontally from the body, resulting in lower body height and wider support on the ground. Combined with an actuated segmented spine and tail, such morphology resembles that of salamanders or crocodiles. Although bio-inspired salamander-like robots with simple rotational limbs have been created, not much research has been done on kinematically redundant bio-mimetic robots that can closely replicate kinematics of sprawling animal gaits. Being bio-mimetic could allow a robot to have some of the locomotion skills observed in those animals, expanding its potential applications in challenging scenarios. At the same time, the robot could be used to answer questions about the animal's locomotion. This thesis is focused on developing locomotion controllers for such robots. Due to their high number of degrees of freedom (DoF), the control is based on solving the limb and spine inverse kinematics to properly coordinate different body parts. It is demonstrated how active use of a spine improves the robot's walking and turning performance. Further performance improvement across a variety of gaits is achieved by using model predictive control (MPC) methods to dictate the motion of the robot's center of mass (CoM). The locomotion controller is reused on an another robot (OroBOT) with similar morphology, designed to mimic the kinematics of a fossil belonging to Orobates, an extinct early tetrapod. Being capable of generating different gaits and quantitatively measuring their characteristics, OroBOT was used to find the most probable way the animal moved. This is useful because understanding locomotion of extinct vertebrates helps to conceptualize major transitions in their evolution. To tackle field applications, e.g. in disaster response missions, a new generation of field-oriented sprawling posture robots was built. The robustness of their initial crocodile-inspired design was tested in the animal's natural habitat (Uganda, Africa) and subsequently enhanced with additional sensors, cameras and computer. The improvements to the software framework involved a smartphone user interface visualizing the robot's state and camera feed to improve the ease of use for the operator. Using force sensors, the locomotion controller is expanded with a set of reflex control modules. It is demonstrated how these modules improve the robot's performance on rough and unstructured terrain. The robot's design and its low profile allow it to traverse low passages. To also tackle narrow passages like pipes, an unconventional crawling gait is explored. While using it, the robot lies on the ground and pushes against the pipe walls to move the body. To achieve such a task, several new control and estimation modules were developed. By exploring these problems, this thesis illustrates fruitful interactions that can take place between robotics, biology and paleontology