Learning Free Gait Transition for Quadruped Robots via Phase-Guided Controller

We propose a method to achieve autonomous gait transition according to speed for a quadruped robot pacing at medium speeds. We verified its effectiveness through experiments with the simulation model and the robot we developed. In our proposed method, a central pattern generator (CPG) is applied to each leg. Each leg is controlled by a PD controller based on output from the CPG. The four CPGs are coupled, and a hard-wired CPG network generates a pace pattern by default. In addition, we feed the body tilt back to the CPGs in order to adapt to the body oscillation that changes according to the speed. As a result, our model and robot achieve stable changes in speed while autonomously generating a walk at low speeds and a rotary gallop at high speeds, despite the fact that the walk and rotary gallop are not preprogramed. The body tilt angle feedback is the only factor involved in the autonomous generation of gaits, so it can be easily used for various quadruped robots. Therefore, it is expected that the proposed method will be an effective control method for quadruped robots.

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A Bio-Inspired Compliance Planning and Implementation Method for Hydraulically Actuated Quadruped Robots with Consideration of Ground Stiffness

Sensors ◽

10.3390/s21082838 ◽

2021 ◽

Vol 21 (8) ◽

pp. 2838

Author(s):

Xiaoxing Zhang ◽

Haoyuan Yi ◽

Junjun Liu ◽

Qi Li ◽

Xin Luo

Keyword(s):

Harmonic Oscillation ◽

Ground Surface ◽

Legged Locomotion ◽

Soft Ground ◽

Quadruped Robots ◽

In Series ◽

Reaction Forces ◽

Implementation Method ◽

The Stability ◽

Natural Dynamics

There has been a rising interest in compliant legged locomotion to improve the adaptability and energy efficiency of robots. However, few approaches can be generalized to soft ground due to the lack of consideration of the ground surface. When a robot locomotes on soft ground, the elastic robot legs and compressible ground surface are connected in series. The combined compliance of the leg and surface determines the natural dynamics of the whole system and affects the stability and efficiency of the robot. This paper proposes a bio-inspired leg compliance planning and implementation method with consideration of the ground surface. The ground stiffness is estimated based on analysis of ground reaction forces in the frequency domain, and the leg compliance is actively regulated during locomotion, adapting them to achieve harmonic oscillation. The leg compliance is planned on the condition of resonant movement which agrees with natural dynamics and facilitates rhythmicity and efficiency. The proposed method has been implemented on a hydraulic quadruped robot. The simulations and experimental results verified the effectiveness of our method.

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Stability-Guaranteed and High Terrain Adaptability Static Gait for Quadruped Robots

Sensors ◽

10.3390/s20174911 ◽

2020 ◽

Vol 20 (17) ◽

pp. 4911

Author(s):

Qian Hao ◽

Zhaoba Wang ◽

Junzheng Wang ◽

Guangrong Chen

Keyword(s):

Impedance Control ◽

Stability Margin ◽

Planning Method ◽

Legged Robots ◽

Gait Planning ◽

Quadruped Locomotion ◽

Quadruped Robots ◽

Adjustment Strategy ◽

Compliant Behavior ◽

The Stability

Stability is a prerequisite for legged robots to execute tasks and traverse rough terrains. To guarantee the stability of quadruped locomotion and improve the terrain adaptability of quadruped robots, a stability-guaranteed and high terrain adaptability static gait for quadruped robots is addressed. Firstly, three chosen stability-guaranteed static gaits: intermittent gait 1&2 and coordinated gait are investigated. In addition, then the static gait: intermittent gait 1, which is with the biggest stability margin, is chosen to do a further research about quadruped robots walking on rough terrains. Secondly, a position/force based impedance control is employed to achieve a compliant behavior of quadruped robots on rough terrains. Thirdly, an exploratory gait planning method on uneven terrains with touch sensing and an attitude-position adjustment strategy with terrain estimation are proposed to improve the terrain adaptability of quadruped robots. Finally, the proposed methods are validated by simulations.

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Mechanism Design and Simulation of the ULTRA Spine: A Tensegrity Robot

Volume 5A: 39th Mechanisms and Robotics Conference ◽

10.1115/detc2015-47583 ◽

2015 ◽

Cited By ~ 10

Author(s):

Andrew P. Sabelhaus ◽

Hao Ji ◽

Patrick Hylton ◽

Yakshu Madaan ◽

ChanWoo Yang ◽

...

Keyword(s):

Mechanism Design ◽

Design Process ◽

Inverse Kinematics ◽

Gear Ratio ◽

Forward Kinematics ◽

Robot Design ◽

Link Structure ◽

Iterative Design ◽

Quadruped Robots ◽

Ongoing Effort

The Underactuated Lightweight Tensegrity Robotic Assistive Spine (ULTRA Spine) project is an ongoing effort to create a compliant, cable-driven, 3-degree-of-freedom, underactuated tensegrity core for quadruped robots. This work presents simulations and preliminary mechanism designs of that robot. Design goals and the iterative design process for an ULTRA Spine prototype are discussed. Inverse kinematics simulations are used to develop engineering characteristics for the robot, and forward kinematics simulations are used to verify these parameters. Then, multiple novel mechanism designs are presented that address challenges for this structure, in the context of design for prototyping and assembly. These include the spine robot’s multiple-gear-ratio actuators, spine link structure, spine link assembly locks, and the multiple-spring cable compliance system.

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Identification of muscle synergies associated with gait transition in humans

Frontiers in Human Neuroscience ◽

10.3389/fnhum.2015.00048 ◽

2015 ◽

Vol 9 ◽

Cited By ~ 34

Author(s):

Shota Hagio ◽

Mizuho Fukuda ◽

Motoki Kouzaki

Keyword(s):

Muscle Synergies ◽

Gait Transition

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Optimized Static Gait for Quadruped Robots Walking on Stairs

10.1109/case49439.2021.9551433 ◽

2021 ◽

Author(s):

Linqi Ye ◽

Yaqi Wang ◽

Xueqian Wang ◽

Houde Liu ◽

Bin Liang

Keyword(s):

Quadruped Robots

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Kinetostatic backflip strategy for self-recovery of quadruped robots with the selected rotation axis

Robotica ◽

10.1017/s0263574721001326 ◽

2021 ◽

pp. 1-19

Author(s):

Shengjie Wang ◽

Kun Wang ◽

Chunsong Zhang ◽

Jian S Dai

Keyword(s):

Optimal Design ◽

Energy Analysis ◽

Rotation Axis ◽

Low Cost ◽

Minimum Energy ◽

Design Parameters ◽

Quadruped Robots ◽

Design Idea ◽

The Relationship

Abstract A kinetostatic approach applied to the design of a backflip strategy for quadruped robots is proposed in this paper. Inspired by legged animals and taking the advantage of the leg workspace, this strategy provides an optimal design idea for the low-cost quadruped robots to achieve self-recovery after overturning. Through kinetostatic and energy analysis, a four-stepped backflip strategy based on the selected rotation axis with minimum energy is proposed, with a process of selection, lifting, rotating, and protection. The kinematic factors that affect the backflip are investigated, along with the relationship between the design parameters of the leg and trunk being analyzed. At the end of this paper, the strategy is validated by a simulation and experiments with a prototype called DRbot, demonstrating that the strategy endows the robot a strong self-recovery ability in various terrains.

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Terrain-Perception-Free Quadrupedal Spinning Locomotion on Versatile Terrains: Modeling, Analysis, and Experimental Validation

Frontiers in Robotics and AI ◽

10.3389/frobt.2021.724138 ◽

2021 ◽

Vol 8 ◽

Author(s):

Hongwu Zhu ◽

Dong Wang ◽

Nathan Boyd ◽

Ziyi Zhou ◽

Lecheng Ruan ◽

...

Keyword(s):

Motion Tracking ◽

Center Of Mass ◽

Kinematic Model ◽

Linear Quadratic Regulator ◽

Small Scale ◽

Small Range ◽

Linear Quadratic ◽

Stability Margins ◽

Uneven Terrain ◽

Quadruped Robots

Dynamic quadrupedal locomotion over rough terrains reveals remarkable progress over the last few decades. Small-scale quadruped robots are adequately flexible and adaptable to traverse uneven terrains along the sagittal direction, such as slopes and stairs. To accomplish autonomous locomotion navigation in complex environments, spinning is a fundamental yet indispensable functionality for legged robots. However, spinning behaviors of quadruped robots on uneven terrain often exhibit position drifts. Motivated by this problem, this study presents an algorithmic method to enable accurate spinning motions over uneven terrain and constrain the spinning radius of the center of mass (CoM) to be bounded within a small range to minimize the drift risks. A modified spherical foot kinematics representation is proposed to improve the foot kinematic model and rolling dynamics of the quadruped during locomotion. A CoM planner is proposed to generate a stable spinning motion based on projected stability margins. Accurate motion tracking is accomplished with linear quadratic regulator (LQR) to bind the position drift during the spinning movement. Experiments are conducted on a small-scale quadruped robot and the effectiveness of the proposed method is verified on versatile terrains including flat ground, stairs, and slopes.

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