scholarly journals Continuous Static Gait with Twisting Trunk of a Metamorphic Quadruped Robot

2018 ◽  
Vol 9 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Chunsong Zhang ◽  
Jian S. Dai
Keyword(s):  
Rigid Body ◽  
Stride Length ◽  
Quadruped Robot ◽  
Quadruped Robots ◽  
Upper Limit ◽  
Locomotion Speed

Abstract. The natural quadrupeds, such as geckos and lizards, often twist their trunks when moving. Conventional quadruped robots cannot perform the same motion due to equipping with a trunk which is a rigid body or at most consists of two blocks connected by passive joints. This paper proposes a metamorphic quadruped robot with a reconfigurable trunk which can implement active trunk motions, called MetaRobot I. The robot can imitate the natural quadrupeds to execute motion of trunk twisting. Benefiting from the twisting trunk, the stride length of this quadruped is increased comparing to that of conventional quadruped robots. In this paper a continuous static gait benefited from the twisting trunk performing the increased stride length is introduced. After that, the increased stride length relative to the trunk twisting will be analysed mathematically. Other points impacting the implementation of the increased stride length in the gait are investigated such as the upper limit of the stride length and the kinematic margin. The increased stride length in the gait will lead the increase of locomotion speed comparing with conventional quadruped robots, giving the extent that natural quadrupeds twisting their trunks when moving. The simulation and an experiment on the prototype are then carried out to illustrate the benefits on the stride length and locomotion speed brought by the twisting trunk to the quadruped robot.

scholarly journals Multi-Phase Joint-Angle Trajectory Generation Inspired by Dog Motion for Control of Quadruped Robot

Sensors ◽  
2021 ◽  
Vol 21 (19) ◽  
pp. 6366
Author(s):  
Jungsu Choi
Keyword(s):  
Basis Function ◽  
Joint Angle ◽  
Trajectory Generation ◽  
Humanoid Robots ◽  
Quadruped Robot ◽  
Continuous Transition ◽  
Quadruped Robots ◽  
Gait Phase ◽  
Locomotion Speed ◽  
Multi Phase

Quadruped robots are receiving great attention as a new means of transportation for various purposes, such as military, welfare, and rehabilitation systems. The use of four legs enables a robustly stable gait; compared to the humanoid robots, the quadruped robots are particularly advantageous in improving the locomotion speed, the maximum payload, and the robustness toward disturbances. However, the more demanding conditions robots are exposed to, the more challenging the trajectory generation of robotic legs becomes. Although various trajectory generation methods (e.x., central pattern generator, finite states machine) have been developed for this purpose, these methods have limited degrees of freedom with respect to the gait transition. The conventional methods do not consider the transition of the gait phase (i.e., walk, amble, trot, canter, and gallop) or use a pre-determined fixed gait phase. Additionally, some research teams have developed locomotion algorithms that take into account the transition of the gait phase. Still, the transition of the gait phase is limited (mostly from walking to trot), and the transition according to gait speed is not considered. In this paper, a multi-phase joint-angle trajectory generation algorithm is proposed for the quadruped robot. The joint-angles of an animal are expressed as a cyclic basis function, and an input to the basis function is manipulated to realize the joint-angle trajectories in multiple gait phases as desired. To control the desired input of a cyclic basis function, a synchronization function is formulated, by which the motions of legs are designed to have proper ground contact sequences with each other. In the gait of animals, each gait phase is optimal for a certain speed, and thus transition of the gait phases is necessary for effective increase or decrease in the locomotion speed. The classification of the gait phases, however, is discrete, and thus the resultant joint-angle trajectories may be discontinuous due to the transition. For the smooth and continuous transition of gait phases, fuzzy logic is utilized in the proposed algorithm. The proposed methods are verified by simulation studies.

scholarly journals The Complex Dynamic Locomotive Control and Experimental Research of a Quadruped-Robot Based on the Robot Trunk

2019 ◽  
Vol 9 (18) ◽  
pp. 3911 ◽  
Author(s):  
Dongyi Ren ◽  
Junpeng Shao ◽  
Guitao Sun ◽  
Xuan Shao
Keyword(s):  
Control Strategy ◽  
Kinematic Model ◽  
Quadruped Robot ◽  
Contact Forces ◽  
Small Magnitude ◽  
Feedback Information ◽  
Joint Torques ◽  
Trunk Motion ◽  
Quadruped Robots ◽  
Leg Motion

The research of quadruped robots is fundamentally motivated by their excellent performance in complex terrain. Maintaining the trunk moving smoothly is the basis of assuring the stable locomotion of the robot. In this paper we propose a planning and control strategy for the pacing gait of hydraulic quadruped robots based on the centroid. Initially, the kinematic model between the single leg and the robot trunk was established. The coupling of trunk motion and leg motion was elaborated on in detail. Then, the real-time attitude feedback information of the trunk was considered, the motion trajectory of the trunk centroid was planned, and the foot trajectory of the robot was carried out. Further, the joint torques were calculated that fulfillment minimization of the contact forces. The position and attitude of the robot trunk were adjusted by the presented controller. Finally, the performance of the proposed control framework was tested in simulations and on a robot platform. By comparing the attitude of the robot trunk, the experimental results show that the trunk moved smoothly with small-magnitude by the proposed controller. The stable dynamic motion of the hydraulic quadruped robot was accomplished, which verified the effectiveness and feasibility of the proposed control strategy.

scholarly journals Gait Tracking Control of Quadruped Robot Using Differential Evolution Based Structure Specified Mixed SensitivityH∞Robust Control

2016 ◽  
Vol 2016 ◽  
pp. 1-18 ◽  
Author(s):  
Petrus Sutyasadi ◽  
Manukid Parnichkun
Keyword(s):  
Tracking Control ◽  
Control Algorithm ◽  
Joint Angle ◽  
Gait Pattern ◽  
Quadruped Robot ◽  
Robust Controller ◽  
Quadruped Robots ◽  
Parameter Variations ◽  
Real Hardware ◽  
Dynamic Gait

This paper proposed a control algorithm that guarantees gait tracking performance for quadruped robots. During dynamic gait motion, such as trotting, the quadruped robot is unstable. In addition to uncertainties of parameters and unmodeled dynamics, the quadruped robot always faces some disturbances. The uncertainties and disturbances contribute significant perturbation to the dynamic gait motion control of the quadruped robot. Failing to track the gait pattern properly propagates instability to the whole system and can cause the robot to fall. To overcome the uncertainties and disturbances, structured specified mixed sensitivityH∞robust controller was proposed to control the quadruped robot legs’ joint angle positions. Before application to the real hardware, the proposed controller was tested on the quadruped robot’s leg planar dynamic model using MATLAB. The proposed controller can control the robot’s legs efficiently even under uncertainties from a set of model parameter variations. The robot was also able to maintain its stability even when it was tested under several terrain disturbances.

Stability Margin of a Metamorphic Quadruped Robot With a Twisting Trunk

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Chunsong Zhang ◽  
Chi Zhang ◽  
Jian S. Dai ◽  
Peng Qi
Keyword(s):  
Closed Loop ◽  
Stability Margin ◽  
Rigid Bodies ◽  
Quadruped Robot ◽  
Quadruped Robots ◽  
Kinematic Performance ◽  
The Stability ◽  
Twisting Angle

Abstract To date, most quadruped robots are either equipped with trunks that are rigid bodies or consist of blocks connected by passive joints. The kinematic performance of these quadruped robots is only determined by their legs. To release the mobility of trunks and enhance the performance of quadruped robots, this paper proposes a metamorphic quadruped robot with a moveable trunk (a planar six-bar closed-loop linkage), called MetaRobot I, which can implement active trunk motions. The robot can twist its trunk like natural quadrupeds. Through trunk twisting, the stability margin of the quadruped robot can be increased compared with that of a quadruped robot with a rigid trunk. The inner relationship between the stability margin and the twisting angle is analyzed in this paper. Finally, simulations are carried out to show the benefits facilitated by the twisting trunk to the quadruped robot.

Full Leg Control of a Quadruped Robot Using Linear Visual Servoing with a Stereo Omnidirectional Camera

2011 ◽  
Vol 5 (2) ◽  
pp. 241-246
Author(s):  
Yukinari Inoue ◽  
◽  
Noriaki Maru ◽  
Keyword(s):  
Visual Servoing ◽  
Visual Space ◽  
Quadruped Robot ◽  
The Body ◽  
Field Of View ◽  
Transformation Equation ◽  
Stereo Camera ◽  
Omnidirectional Camera ◽  
Quadruped Robots ◽  
Omnidirectional Image

The authors have previously proposed foot tip control for quadruped robots using linear visual servoing (LVS) with a normal stereo camera. However, a normal stereo camera has a narrow field of view and is incapable of seeing all four legs simultaneously. Consequently, it has been a problem that the control of all the legs have required that the rotatation of the camera be controlled. This article proposes a method by which a stereo omnidirectional camera is provided at a position low on the body to control all four legs through LVS. In this article, we at first present a transformation equation from an omnidirectional image to a binocular visual space, and we develop a servo equation of LVS in which an omnidirectional image is used. Then, through simulation, we confirm trajectories with the LVS applied to foot tip control. We also conduct an experiment using TITAN-VIII to demonstrate the efficacy of the proposed method.

Topology Configuration of Actuator Failure Mode of a Novel Quadruped Robot

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Jing Wang ◽  
Feng Gao ◽  
Yong Zhang
Keyword(s):  
Fault Tolerance ◽  
Motion Planning ◽  
Failure Mode ◽  
Quadruped Robot ◽  
Actuator Failure ◽  
End Effector ◽  
Actuator Failures ◽  
Quadruped Robots ◽  
Intersection Operation ◽  
Sets Theory

Fault tolerance is an important characteristic of quadruped robots. Actuator failure mode is the basis for research of fault tolerance and motion planning of quadruped robots. In this paper, the combination of actuator failures and the remained end-effector characteristics are investigated based on “GF sets” theory. With intersection operation property in “GF sets,” the remained motion ability can be easily judged. The combination of one and two actuator failures is analyzed in detail and some examples are used to illustrate the method of motion ability analysis. Experiments are carried out on the prototype of a novel quadruped robot and the results show that this method is effective for analysis of fault tolerance of quadruped robots.

scholarly journals Self-Stabilising Quadrupedal Running by Mechanical Design

2009 ◽  
Vol 6 (1) ◽  
pp. 73-85 ◽  
Author(s):  
Panagiotis Chatzakos ◽  
Evangelos Papadopoulos
Keyword(s):  
Mechanical System ◽  
Mechanical Design ◽  
Quadruped Robot ◽  
The Self ◽  
Rough Terrain ◽  
Stable Regime ◽  
Quadruped Robots ◽  
The Stability ◽  
Running Robots ◽  
Body Inertia

Dynamic stability allows running animals to maintain preferred speed during locomotion over rough terrain. It appears that rapid disturbance rejection is an emergent property of the mechanical system. In running robots, simple motor control seems to be effective in the negotiation of rough terrain when used in concert with a mechanical system that stabilises passively. Spring-like legs are a means for providing self-stabilising characteristics against external perturbations. In this paper, we show that a quadruped robot could be able to perform self-stable running behaviour in significantly broader ranges of forward speed and pitch rate with a suitable mechanical design, which is not limited to choosing legs spring stiffness only. The results presented here are derived by studying the stability of the passive dynamics of a quadruped robot running in the sagittal plane in a dimensionless context and might explain the success of simple, open loop running controllers on existing experimental quadruped robots. These can be summarised in (a) the self-stabilised behaviour of a quadruped robot for a particular gait is greatly related to the magnitude of its dimensionless body inertia, (b) the values of hip separation, normalised to rest leg length, and leg relative stiffness of a quadruped robot affect the stability of its motion and should be in inverse proportion to its dimensionless body inertia, and (c) the self-stable regime of quadruped running robots is enlarged at relatively high forward speeds. We anticipate the proposed guidelines to assist in the design of new, and modifications of existing, quadruped robots. As an example, specific design changes for the Scout II quadruped robot that might improve its performance are proposed.

scholarly journals Behavior Selection Based Navigation and Obstacle Avoidance Approach Using Visual and Ultrasonic Sensory Information for Quadruped Robots

10.5772/6234 ◽  
2008 ◽  
Vol 5 (4) ◽  
pp. 41 ◽  
Author(s):  
Kiyotaka Izumi ◽  
Maki K. Habib ◽  
Keigo Watanabe ◽  
Ryoichi Sato
Keyword(s):  
Real Time ◽  
Obstacle Avoidance ◽  
Sensory Information ◽  
Quadruped Robot ◽  
Fine Tuning ◽  
Ultrasonic Sensors ◽  
Quadruped Robots ◽  
Step Over ◽  
Over Time ◽  
Behavior Selection

A robot functioning in an environment may exhibit various forms of behavior emerge from the interaction with its environment through sense, control and plan activities. Hence, this paper introduces a behaviour selection based navigation and obstacle avoidance algorithm with effective method for adapting robotic behavior according to the environment conditions and the navigated terrain. The developed algorithm enable the robot to select the suitable behavior in real-time to avoid obstacles based on sensory information through visual and ultrasonic sensors utilizing the robot's ability to step over obstacles, and move between surfaces of different heights. In addition, it allows the robot to react in appropriate manner to the changing conditions either by fine-tuning of behaviors or by selecting different set of behaviors to increase the efficiency of the robot over time. The presented approach has been demonstrated on quadruped robot in several different experimental environments and the paper provides an analysis of its performance.

Design of Vertebrae-Inspired Trunk Mechanism for Robust and Directive Quadruped Locomotion on Rough Terrain Without Requiring Sensing and Actuation

2017 ◽  
Vol 29 (3) ◽  
pp. 546-555 ◽  
Author(s):  
Takashi Takuma ◽  
◽  
Yoshiki Murata ◽  
Wataru Kase
Keyword(s):  
Rigid Body ◽  
Success Rate ◽  
Design Principle ◽  
Quadruped Robot ◽  
Rough Terrain ◽  
Elastic Coefficient ◽  
Sensors And Actuators ◽  
Quadruped Locomotion ◽  
Trunk Posture ◽  
Simulation Results

[abstFig src='/00290003/10.jpg' width='300' text='Quadruped robot equipping a vertebrae-inspired trunk mechanism' ] Quadrupedal animals adaptively change their trunk posture in order to avoid falling down and to facilitate directive locomotion even on rough terrain. This paper focuses on an animal-like trunk mechanism which has passive viscoelastic joints. The effect of the trunk mechanism is observed by changing the elasticity and configuration of joints. Simulation results showed that the locomotion success rate of a robot equipped with the trunk mechanism on rough terrain is higher than the locomotion success rate of a robot equipped with a rigid body. In addition, the distribution of the success rate changes according to the elastic coefficient, number, configuration, and type of joints. These results suggest a design principle for the trunk mechanism of a quadruped robot in order to obtain robust and directive locomotion without requiring sensors and actuators.

Turning strategies for the bounding quadruped robot with an active spine

2018 ◽  
Vol 45 (5) ◽  
pp. 657-668 ◽  
Author(s):  
Zhong Wei ◽  
Guangming Song ◽  
Huiyu Sun ◽  
Qien Qi ◽  
Yuan Gao ◽  
...  
Keyword(s):  
Oscillation Amplitude ◽  
Initial Position ◽  
Quadruped Robot ◽  
Content Type ◽  
Quadruped Robots ◽  
Spine Motion ◽  
Real Robot ◽  
Turning Radius ◽  
Bounding Gait ◽  
Bounding Locomotion

Purpose This paper aims to study the turning strategies for the bounding quadruped robot with an active spine and explore the significant role of the spine in the turning locomotion. Design/methodology/approach Firstly, the bounding gait combining the pitch motion of the spine with the leg motion is presented. In this gait, the spine moves in phase with the front legs. All the joints of the legs and spine are controlled by cosine signals to simplify the control, and the initial position and oscillation amplitude of the joints can be tuned. To verify the effectiveness of the proposed gait, the spine joints are set with different initial positions and oscillation amplitudes, and the initial position and oscillation amplitude of the leg joints are tuned to make the virtual model do the best locomotion in terms of the speed and stability in the simulation. The control signals are also used to control a real robot called Transleg. Then, three different turning strategies are proposed, including driving the left and right legs with different strides, swaying the spine in the yaw direction and combining the above two methods. Finally, these strategies are tested on the real robot. Findings The stable bounding locomotion can be achieved using the proposed gait. With the spine motion, the speed of the bounding locomotion is increased; the turning radius is reduced; and the angular velocity is increased. Originality/value A simple and flexible planning of the bounding gait and three turning strategies for the bounding quadruped robot are proposed. The effectiveness of the proposed bounding gait, along with the beneficial effect of the spine motion in the yaw direction on the turning locomotion is demonstrated with the computer simulations and robot experiments. This will be instructive for the designing and actuating of the other quadruped robots.

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