Fault-tolerant crab gaits and turning gaits for a hexapod robot

Robotica ◽  
2005 ◽  
Vol 24 (2) ◽  
pp. 269-270 ◽  
Author(s):  
Jung-Min Yang
Keyword(s):  
Stride Length ◽  
Fault Tolerant ◽  
Stability Margin ◽  
Hexapod Robot ◽  
Joint Failure ◽  
Gait Planning

This paper studies crab gaits and turning gaits of a hexapod robot with a locked joint failure. Due to the reduced workspace of a failed leg, fault-tolerant gaits have limitations in their mobility. Based on the principles of fault-tolerant gait planning, periodic crab gaits and turning gaits are proposed in which a hexapod robot carries out tripod walking after a locked joint failure, having a reasonable stride length and stability margin.

scholarly journals Fault-Tolerant Tripod Gait Planning and Verification of a Hexapod Robot

2020 ◽  
Vol 10 (8) ◽  
pp. 2959
Author(s):  
Yiqun Liu ◽  
Xuanxia Fan ◽  
Liang Ding ◽  
Jianfeng Wang ◽  
Tao Liu ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Fault Tolerant ◽  
Kinematic Model ◽  
Stability Margin ◽  
The Body ◽  
Hexapod Robot ◽  
Gait Planning ◽  
Phase Sequence ◽  
Gait Phase ◽  
Tripod Gait

In some hazardous or inaccessible applications, such as earthquake rescue, as a substitute for mankind, robots are expected to perform missions reliably. Unfortunately, the failure of components is difficult to avoid due to the complexity of robot composition and the interference of the environment. Thus, improving the reliability of robots is a crucial problem. The hexapod robot has redundant degrees of freedom due to its multiple joints, making it possible to tolerate the failure of one leg. In this paper, the Fault-Tolerant Tripod (F-TT) gait dealing with the failure of one leg is researched. The Denavit–Hartenberg (D-H) method is exploited to establish a kinematic model for the hexapod robot, the Jacobian matrix is analyzed, and it is proved that the body can be controlled when three legs are supported. Then, an F-TT gait phase sequence planning method based on a stability margin is established, and a method to improve stability is proposed. The trajectory for the center of gravity (COG) and foot is studied. Finally, a simulation model and prototype robot experiments are developed, and the effectiveness of the proposed method is verified.

Gait synthesis for hexapod robots with a locked joint failure

Robotica ◽  
2005 ◽  
Vol 23 (6) ◽  
pp. 701-708 ◽  
Author(s):  
Jung-Min Yang
Keyword(s):  
Fault Tolerant ◽  
Static Stability ◽  
Walking Robots ◽  
Robot Kinematics ◽  
Hexapod Robot ◽  
Joint Failure ◽  
Straight Line ◽  
Gait Synthesis ◽  
Gait Study

This paper presents a strategy for generating fault-tolerant gaits of hexapod walking robots. A multi-legged robot is considered to be fault-tolerant with respect to a given failure if it is capable of continuing its walking after the occurrence of a failure, maintaining its static stability. The failure concerned in this paper is a locked joint failure for which a joint in a leg cannot move and is locked in place. The kinematic condition for the existence of fault-tolerant gaits is derived for straight-line walking of a hexapod robot on even terrain. An algorithm for generating fault-tolerant gaits is described and, especially, periodic gaits are presented for forward walking of a hexapod robot with a locked joint failure. The leg sequence and the stride length formula are analytically driven based on gait study and robot kinematics. A case study on post-failure walking of a hexapod robot with the wave gait is shown to demonstrate the applicability of the proposed method.

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

Sensors ◽  
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.

scholarly journals Planning Fail-Safe Trajectories for Space Robotic Arms

2021 ◽  
Vol 8 ◽  
Author(s):  
Oliver Porges ◽  
Daniel Leidner ◽  
Máximo A. Roa
Keyword(s):  
Degrees Of Freedom ◽  
Fault Tolerant ◽  
Robotic Manipulators ◽  
Task Completion ◽  
Joint Failure ◽  
Space Applications ◽  
Robotic Arms ◽  
Hazardous Environments ◽  
Potential Risks ◽  
Fail Safe

A frequent concern for robot manipulators deployed in dangerous and hazardous environments for humans is the reliability of task executions in the event of a joint failure. A redundant robotic manipulator can be used to mitigate the risk and guarantee a post-failure task completion, which is critical for instance for space applications. This paper describes methods to analyze potential risks due to a joint failure, and introduces tools for fault-tolerant task design and path planning for robotic manipulators. The presented methods are based on off-line precomputed workspace models. The methods are general enough to cope with robots with any type of joint (revolute or prismatic) and any number of degrees of freedom, and might include arbitrarily shaped obstacles in the process, without resorting to simplified models. Application examples illustrate the potential of the approach.

Gait Planning and Control of Hexapod Robot Based on Velocity Vector

2021 ◽  
Author(s):  
Junfeng Xue ◽  
Jiehao Li ◽  
Zhihua Chen ◽  
Shoukun Wang ◽  
Junzheng Wang ◽  
...  
Keyword(s):  
Velocity Vector ◽  
Hexapod Robot ◽  
Gait Planning ◽  
Planning And Control ◽  
And Control

Deviation from the direction of motion across gaits in a hexapodal robot

2020 ◽  
Vol 47 (3) ◽  
pp. 325-333
Author(s):  
Zijie Niu ◽  
Aiwen Zhan ◽  
Yongjie Cui
Keyword(s):  
Design Methodology ◽  
Planning Method ◽  
Hexapod Robot ◽  
Acceleration Sensor ◽  
Forward Motion ◽  
Gait Planning ◽  
Content Type ◽  
Cargo Handling ◽  
Subsequent Research ◽  
Experimental Errors

Purpose The purpose of this study is to test a chassis robot on rugged road cargo handling. Design/methodology/approach Attitude solution of D-H series robot gyroscope speed and acceleration sensor. Findings In identical experimental environments, hexapodal robots experience smaller deviations when using a four-footed propulsive gait from a typical three-footed gait for forward motion; for the same distance but at different speeds, the deviation basically keeps itself within the same range when the robot advances forward with four-foot propulsive gait; because the foot slide in the three-footed gait sometimes experiences frictions, the robot exhibits a large gap in directional deviations in different courses during motion; for motion using a four-footed propulsive gait, there are minor directional deviations of hexapodal robots resulting from experimental errors, which can be reduced through optimizing mechanical structures. Originality/value Planning different gaits can solve problems existing in some typical gaits. This article has put forward a gait planning method for hexapodal robots moving forward with diverse gaits as a redundant multifreedom structure. Subsequent research can combine a multiparallel-legged structure to analyze kinematics, optimize the robot’s mechanical structure and carry out in-depth research of hexapod robot gaits.

scholarly journals Lower Limb Exoskeleton Gait Planning Based on Crutch and Human-Machine Foot Combined Center of Pressure

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7216
Author(s):  
Wei Yang ◽  
Jiyu Zhang ◽  
Sheng Zhang ◽  
Canjun Yang
Keyword(s):  
Lower Limb ◽  
Stride Length ◽  
Center Of Pressure ◽  
Balance Control ◽  
Effective Means ◽  
Stability Control ◽  
Planning Method ◽  
Gait Planning ◽  
Lower Limb Exoskeleton ◽  
Cord Injury

With the help of wearable robotics, the lower limb exoskeleton becomes a promising solution for spinal cord injury (SCI) patients to recover lower body locomotion ability. However, fewer exoskeleton gait planning methods can meet the needs of patient in real time, e.g., stride length or step width, etc., which may lead to human-machine incoordination, limit comfort, and increase the risk of falling. This work presents a human-exoskeleton-crutch system with the center of pressure (CoP)-based gait planning method to enable the balance control during the exoskeleton-assisted walking with crutches. The CoP generated by crutches and human-machine feet makes it possible to obtain the overall stability conditions of the system in the process of exoskeleton-assisted quasi-static walking, and therefore, to determine the next stride length and ensure the balance of the next step. Thus, the exoskeleton gait is planned with the guidance of stride length. It is worth emphasizing that the nominal reference gait is adopted as a reference to ensure that the trajectory of the swing ankle mimics the reference one well. This gait planning method enables the patient to adaptively interact with the exoskeleton gait. The online gait planning walking tests with five healthy volunteers proved the method’s feasibility. Experimental results indicate that the algorithm can deal with the sensed signals and plan the landing point of the swing leg to ensure balanced and smooth walking. The results suggest that the method is an effective means to improve human–machine interaction. Additionally, it is meaningful for the further training of independent walking stability control in exoskeletons for SCI patients with less assistance of crutches.

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