Gait Generation Method Research Articles

Gait Generation of a 10-DOF Humanoid Robot on Deformable Terrain Based on Spherical Inverted Pendulum Model

Abstract Gait generation of a humanoid robot on deformable terrain is a complex problem as the foot and terrain interaction and terrain deformation has to be included in the dynamics. In order to simplify the dynamics of walk on deformable terrain, we used a spherical inverted pendulum (SIP) to represent the single support phase, in which the effect of terrain deformation is represented by a spring and damper contact model. The impact model for leg transition is derived from angular momentum conservation. In order to minimize the energy loss due to impact, the double support phase is modeled as a suspended pendulum. Based on the motion of the SIP model, the hip and leg trajectories of a 10 DOF humanoid robot are generated. The joint angles of the humanoid are obtained from inverse kinematics. The motion of the center of mass is analyzed by inverse dynamics of a floating-base robot. The proposed gait generation method has been experimentally validated using a Kondo KHR-3HV humanoid robot on deformable terrain. The results show that the humanoid can effectively track the trajectories of the SIP model.

Optimal reorientation of planar floating snake robots with collision avoidance

In this paper, a motion planning algorithm for floating planar under-actuated hyper-redundant snake robots is proposed. The presented algorithm generates locally optimal shape trajectories, i.e., continuous trajectories in the base space of the robot. Such shape trajectories produce a desired rotation of the snake robot, i.e., change in the uncontrolled orientation fiber variable. The proposed method formulates the motion planning problem as an optimization problem where the objective function could be defined to minimize various metrics, such as energy-based cost functions. Additionally, the proposed motion planning algorithm uses a heuristic to generate shape trajectories that avoid self-intersections and obstacle collision. Hence, the motion planning method generates shape trajectories that locally minimize user-defined cost functions and eliminate self-intersections or obstacle collision. The proposed gait generation method is validated using numerical simulations of five-link and seven-link snake robots.

Stable gait generation method for lower-limb exoskeleton based on instrumented crutches

Lower-limb exoskeletons have attracted considerable interest because they can provide impaired individuals with the ability to walk upright. Trajectory generation of walking gait is a crucial issue for lower-limb exoskeletons that has not yet been satisfactorily solved. The purpose of this article is to study a stable gait generation method considering the subjective walking intention. Inspired by the motion synergy between crutches and lower limbs, a stable gait generation method for flat-ground walking was proposed for a lower-limb exoskeleton. The motion synergy in the sagittal plane between the crutch-pitch-angle and step length was validated using theoretical and experimental methods. The synergistic relationship between the maximum crutch-pitch-angle and step-length coefficient was established and optimized. Based on the synergistic relationship, the gait trajectory of the exoskeleton with variable step length can be instinctively generated with a crutch swing. The gait stability of the human-exoskeleton system was modeled and analyzed. Consecutive walking experiments were conducted on flat ground in which a compact lower-limb exoskeleton and pair of instrumented crutches were employed. The results demonstrate that gait based on the synergistic relationship is effective and stable, thereby verifying the feasibility of this human-in-the-loop gait generation method.

Gait Generation Method of Snake Robot Based on Main Characteristic Curve Fitting.

Gait generation method is one of the important contents of snake robot motion control. Different gait generation methods produce completely different forms of control functions, so snake robots need more complicated programming logic and processes to realize various gaits and their transformation. Therefore, we propose a new unified expression of gait method, The MCC (main characteristics control) method simplifies and unifies the control functions of different snake robots gaits by extracting the main features of the backbone curves of snake robots gaits. Since all periodic curves that meet the Dirichlet conditions can be formed by superposition of sinusoidal curves, taking the "lowest frequency" part that reflects the main characteristics of the curve as the target configuration can simplify the motion control function of snake robots' gaits. Based on the MCC method, some snake robot gaits are reconstructed, including serpentine gait, rolling gait, helix rolling gait, and crawler gait. In addition, based on MCC method, an AEH-sidewinding gait control method is proposed. The backbone of the AEH-sidewinding gait is closer to the ideal elliptic helix, thus improving the accuracy of its kinematics modeling of snake robot sidewinding gait. Finally, the validity of this gait is verified by experiments. This unified gait expression of snake robots will be helpful to realize smooth gait switching between different gaits of snake robots.

Online gait generator for lower limb exoskeleton robots: Suitable for level ground, slopes, stairs, and obstacle avoidance

The development of lower limb exoskeletons has seen significant interest in recent times. Two types of them are more used that cover two types of needs: gait rehabilitation and human locomotion assistance. An essential subject in controlling the latter kind is trajectory generation, in which there are still challenges. For online controlling of the exoskeleton, gait parameters must have the ability to change at any moment during walking, taking into account human intention and particular conditions. In this paper, an online gait generation method is provided that is suitable for different walking modes. For this purpose, three trajectory generator blocks are proposed. The first block is for the center of mass (CoM) in the double support phase, where the trajectory is generated to make the patient feel more comfortable. The second block is for the support leg in the single support phase. The trajectory is generated using the center of pressure (CoP) criterion to secure backward balance and reduce the forces applied to the arms. The last block is for the swing leg in the single support phase, where a cost function is proposed to minimize the torques of the motors. The performance analysis of the proposed trajectory generator blocks was evaluated, and walking patterns were examined via simulations. Finally, three experimental tests were implemented with a healthy subject wearing Exoped® exoskeleton on level-ground with an obstacle, and stairs.

Gait Design and Analysis of Quadruped Crawling Robot Climbing Over the Raised Terrain of Slope

Background: Quadruped crawling robots face challenges when working in the raised terrain of a slope. The robot is affected by gravity and gait under this terrain. The ground reaction force on its hind legs is relatively large. This has strict requirements for the structure and gait planning of the quadruped crawling robot. Objective: Aimed at the problem of a large ground reaction force on the rear legs of the quadruped crawling robot when crawling on the raised terrain of a slope, a slope-triangular gait walking strategy for quadruped robots based on a layered CGP gait generation method is proposed. Methods: Three-dimensional model of the quadruped crawling robot is created in SOLIDWORKS. The kinematic model is established, and the foot position vector is obtained. Considering the characteristics of the raised terrain of a slope, slope tripod gait and hierarchical CPG slope tripod gait generator are proposed. Comparative simulation of sloped tripod gait and flat tripod gait, the slope tripod gait with and without the gait generator is carried out by Adams programming. Results: When the quadruped crawling robot adopts slope tripod gait and flat tripod gait respectively, the centroid displacement curve, foot speed curve and foot contact force curve are compared. When the quadruped crawling robot adopts the slope tripod gait and does not adopt the slope tripod gait, the body posture curves of the two are compared. The result proves that the tripod gait walking strategy is feasible. Conclusion: The slope tripod gait walking strategy can improve the impact resistance of the quadruped crawling robot on sloped high ground. The gait design and motion analysis process of the robot can provide a reference for other quadruped crawling robot devices.

Research on obstacle climbing gait of snake‐like robot on high‐voltage cables cables

Aiming at the gait control problem of a snake-like inspection robot performing variable-diameter spiral motion on high-voltage cables, a gait generation method is proposed here, the snake-like robot can adapt to the change in diameter when it is winding around the obstacles of high-voltage cables. The piecewise helix is fitted with the Bezier curve of degree 3, which solves the problem of discontinuous speed and abrupt change of joint angle when the snake-like robot moves with variable diameter, and avoids periodic motion impact. The new idea provides for the application of a snake-like robot on high-voltage cables.

Walking motion measurement using IMU and assist control of powered wear with wire-driven assist

This study proposes a target energy trajectory generation method that incorporates virtual passive dynamic walking, which is known as a gait generation method for biped robots, as a control method for a wire-driven powered wear for walking aid. In addition, we developed a gait motion measurement system using IMU to realize the proposed method in real time. By using the proposed method, we expect to realize a gait assist system that provides assistive forces based on the wearer’s current motion.

Non-programmed gait generation of quadruped robot using pulse-type hardware neuron models

In this paper, the authors will propose the active gait generation of a quadruped robot. The theory that quadruped animals unconsciously generate gaits by some system based on neural networks in the spinal cord is widely accepted. However, how biological neurons or neural networks can generate gaits is not clear. To clarify the gait generation method, one of the solutions is using the neuron model similar to the biological neuron. We developed the quadruped robot system using self-inhibited pulse-type hardware neuron models (P-HNMs), which can output the electrical activity similar to those of biological neurons. The P-HNMs consist of the cell body model and the inhibitory synaptic model. The cell body model periodically outputs pulsed voltages; the inhibitory synaptic model inhibits the pulsed voltages. The pulse period can change by varying the synaptic weight control voltage applied to the P-HNMs. We varied the synaptic weight control voltage according to the pressure on the robot’s toes. Also, we changed the angle of the robot’s joints by a constant angle each time the P-HNMs output a pulse. As a result of the walking experiment, we confirmed that the robot generates walk gait and trot gait according to the moving speed. Also, we clarified the process by which the robot actively generates gaits from the upright state. These results show that animals may not use many biological neurons to generate gaits. Furthermore, the results suggest the possibility of realizing simple and bio-inspired robot control.

Dynamic running hexapod robot based on high-performance computing

Advanced high-performance computing (HPC) plays an important role in solving complex and large problems in robot simulation, parameter identification, and control. This article introduces a flexible hexapod robot with arc-shaped legs that has the ability to move fast and agilely based on HPC. Its mechanical structure design follows the principle of miniaturization and lightweight. While the robot uses drive devices with high power density, power supply, and drive, systems with high performance are designed for it to meet the requirements of high bursting capabilities and rapid movement capabilities. Meanwhile, this article proposes a gait generation and control method for the hexapod robot based on max-plus algebra. This method regards the movement of touching and leaving the ground during robot’s walking as discrete events and uses a set of max-plus algebraic linear equations to describe the sequence of each discrete event in different locomotion gaits. By using this method, control laws for various gaits can be generated easily, switch of different gaits in real time can be achieved by switching the control matrix of these gaits, while the stability of the switching process and the synchronism of the locomotion of each leg before and after switching are also ensured. The virtual prototype simulation and physical prototype experiments were exerted to verify the effectiveness of the structure design and control method. Moreover, the simulation analysis and prototype experiment of Trotting diagonal gait and Pronking jumping gait were carried out in which the Pronking gait had a maximum traveling speed of 1.2 m/s.

Personalized gait trajectory generation based on anthropometric features using Random Forest

Using lower limb rehabilitation robots (LLRRs) to help stroke patients recover their walking ability is attracting more and more attention presently. Previous studies have shown that gait rehabilitation training with natural gait pattern can improve the therapeutic outputs. However, how to generate the personalized gait trajectory has not been well researched. In this paper, a personalized gait generation method based anthropometric features is proposed. Firstly, gait trajectories are fitted and simplified into Fourier coefficient vectors, which are used to represent gait trajectories. Secondly, fourteen body features are used to generate the personalized gait trajectories and the feature set is further optimized based on the minimal redundancy maximal relevance criterion for easy application on the LLRR. Then, the relationship between the optimized feature set and gait trajectories is modeled by using the RF algorithm. Finally, the performance of the proposed method is demonstrated by several comparison experiments.

Knee and torso kinematics in generation of optimum gait pattern based on human-like motion for a seven-link biped robot

Gait pattern affects the quality of a walking robot. In this paper, an optimum human-like gait generation method is proposed for a seven-link biped robot. This method utilizes kinematic constraints based on human-like motion. At first, the constraints are parameterized with unknown parameters. Then, an optimization problem is defined with an objective function and the kinematic constraints. The objective function includes the energy consumption and walking stability. Unknown parameters appearing in the constraints are determined by solving the optimization problem. Joint variables are obtained by integrating a velocity form of the kinematic constraints. This approach is carried out for gait planning of the seven-link biped robot and its results are presented. This method allows studying some effective parameters on the gait such as constant knee angle duration, and torso inclination is optimized for different speeds. Our studies indicate that as walking speed increases the knee should extend and the torso should lean forward further in order to maintain better stability. Moreover, energy consumption increases as the torso leans forward.

Generation of a continuous free gait for quadruped robot over rough terrains

ABSTRACTGenerating a robust gait is one of the most important factors to improve the adaptability of quadruped robots on rough terrains. This paper presents a new continuous free gait generation method for quadruped robots capable of walking on the rough terrain characterized by the uneven ground and forbidden areas. When walking with the proposed gait, the robot can effectively maintain its stability by using the Center of Gravity (COG) trajectory planning method. After analyzing the point cloud of rough terrain, the forbidden areas of the terrain can be obtained. Based on this analysis, an optimal foothold search strategy is presented to help quadruped robot to determine the optimum foothold for the swing foot automatically. In addition, the foot sequence determining method is proposed to improve the performance of robot. With the free gait proposed in this paper, quadruped robot can walk through the rough terrains automatically and successfully. The correctness and effectiveness of the proposed method is verified via simulations.

Static Gait Planning Method for Quadruped Robot Walking on Unknown Rough Terrain

To enable quadruped robot to walk through unknown rough terrains without any machine vision system, a continuous static gait planning method is proposed in this paper. A algorithm for on-line terrain complexity evaluation according to touchdown times of swing feet is presented to make quadruped robot obtain the information of terrain without relying on machine vision system. Quadruped robot can obtain enough stability margin during walking process by using the proposed body trajectory planning method, and motion continuity of body can be guaranteed. In order to improve the terrain adaptability of quadruped robot, a tunable parameter is set in the body planning method, and the relationship between value of the tunable parameter and terrain complexity estimation is given to further improve terrain adaptability and energy utilization rate. With the proposed static gait generation method, quadruped robot can autonomous plan its static gait in real-time and travel over unknown rough terrains with enough stability margin. The simulation results show the correctness and effectiveness of the proposed method.

A Novel Serpentine Gait Generation Method for Snakelike Robots Based on Geometry Mechanics

In this paper, a novel serpentine gait generation method is proposed based on geometry mechanics. From the view of differential geometry, the configuration of snake-like robots can be described by a fiber bundle, in which the net locomotion corresponds to the fiber space and the gait corresponds to the bases space. The serpentine gait can be generated by calculating the connection of the fiber bundle. Compared with the traditional gait generation method, such as the curve-based method and the central pattern generator-based method, the proposed method does not assume that the serpentine gait is a standard sinusoidal signal. Models have been developed based on geometric mechanics, which build the relation between the net locomotion and the serpentine gaits analytically. Based on these models, the serpentine gaits for snakelike robots with passive wheels can be generated by planning the quasi-velocity and the serpentine gaits for underwater snakelike robots can be generated by analyzing the integral of the height function. The serpentine gaits generated by the proposed method directly couple with the locomotion of the snakelike robot, which enables the desired locomotion to be realized efficiently. To validate the proposed method, both the snakelike robot with passive wheels and the underwater snakelike robot are taken to perform the experiments. Additionally the recursive Newton–Euler method with the model of hydrodynamic forces is also taken to test the underwater serpentine gaits. Experiments and simulation have validated our proposed method.

Design and Implementation of Stable Gait for Bipedal Robot

This paper presents an optimized method of gait planning for a small biped humanoid robot which developed independently. The method is based on the research of the gait generation patterns for biped robot and analyses the gait generation method which based on three dimensional linear inverted pendulum and the relationship between the COG height, initial velocity, step length and the walk cycle. We carry on the design of bipedal robot gait and realize the stable walking of robot. The simulation and experimental results have confirmed the feasibility of this method.

The Effect of Foot Structure on Locomotion of a Small Biped Robot

This paper is a presentation of a work that consists of considering a novel foot structure for biped robot inspired by human foot. The specific objective is to develop a foot mechanism with human-like toes for a small biped robot. The chosen architecture to present the biped includes ten degrees of freedom (DoF) on ten articulations between eleven links. Our study considers the effect of varying foot structure on a walking process of the robot in simulation by ADAMS (MSC software, USA) through gait generation method. In toe mechanism, aiming to reduce the energy consumption, the passive joint was selected as the toe joint. The center of gravity (CoG) point trajectories of the robot with varying toe is compared with each other in normal motion on flat terrain to determine the most consistent toe mechanism. The result shows that the selected foot structure enables the robot to walk stably and naturally.

柔軟半球足を持つ二足歩行ロボットのバランス制御と歩容生成

In this paper, a new type bipedal robot which has soft hemispheric feet is proposed. It is able to realize an efficient bipedal locomotion by utilizing a rolling motion of hemispheric feet effectively. Furthermore, each hemispheric foot has an active torsional joint. Thus it is able to move as a wheeled vehicle using an infinite rolling motion by the torsional joint. It, however, is difficult to keep its balance more proper than a humanoid robot having normal flat feet. Therefore, firstly a balance control and gait generation method which consider the rolling effect of feet are proposed. After that, several numerical simulations are conducted to demonstrate the effectiveness of the proposed balance control and gait generation method.

A novel gait generation method independent of target settling-time adjustment for underactuated limit cycle walking

This paper proposes a novel gait generation method for surely achieving constraint on impact posture in limit cycle walking. First, we introduce an underactuated rimless wheel model without ankle-joint actuation and formulate a state-space realization of the control output using the stance-leg angle as a time parameter through an input–output linearization. Second, we determine a control input that moves the control output to a terminal value at a target stance-leg angle during the single-support phase. Third, we conduct numerical simulations to observe the fundamental gait properties and discuss the relationship between the gait symmetry and mechanical energy restoration. Furthermore, we mathematically prove the asymptotic stability of the generated walking gait by analytically deriving the restored mechanical energy.

A free gait generation method for quadruped robots over rough terrains containing forbidden areas

Planning a robust gait is one of the most basic aspects to enable a quadruped robot to walk stably on rough terrains. In this paper, we focus on the scenario where a quadruped robot travelling on the rough terrains containing forbidden areas, and a free gait generation method for quadruped robot is proposed. Under the assumption that a set of the positions which can be selected as the foothold is given, the quadruped robot can select the swing foot sequence and choose the best foothold for the swing foot automatically. A body sway motion is included into the motion planning of the free gait to enlarge the stability margin of the robot. With the aid of the sway motion, the stability margin of the robot is no less than the minimum stability margin during the whole walking process. In order to guarantee the locomotion continuity of the quadruped robot, a COG trajectory which has continuous velocity and acceleration profiles is automatically generated. Moreover, the locomotion speed of the robot is improved by ensuring the kinematic margin of the selected swing foot to be zero just before this foot lift-off the ground. With the free gait generation method proposed in this paper, the robot can autonomously navigate through rough terrains as soon as possible on the condition that the robot has enough stability margin. The simulation results show the correctness and effectiveness of the proposed method.