Planning on Bionic Walking Gait of Quadruped Robot over Rough Terrain

A quadruped robot is more adjustable to a complex terrain than a wheeled or caterpillar robot to realize the continuous adjustable motions characterized by submissiveness and low energy consumption in basic control of the quadruped robot over rough terrain. This paper presents a static walking mode of ＂altitude hold＂, which means to keep absolute altitude by controlling limbs adjustably on the basis of which biokinetics studies have shown that quadrupeds can move with almost the same body altitude over rough terrains characterized by a nearly horizontal relief. The gait design specifies several characteristic states of stance phase and swing phase for a quadruped robot and controls the phase sequence and phase of four legs through change of characteristic states. Furthermore, we design a robot control system to generate adjustable gaits and control the coordinative movement of robot joints. This planning method is tested through ADAMS and MATLAB interactive co-simulation; the quadruped robot which has 8 degrees of freedom （8-DOF） is used to simulate the motion over a terrain character- ized by randomly arranged humps. The results show that this method can make the quadruped robot capable to walk over certain rough terrain.

A 3-DOF piezoelectric robot with continuous walking gait aiming at cross-scale smooth motion

Piezoelectric robots play important roles in the field of micromanipulation, but it is difficult for them to generate steady precision motion at any moment. In order to eliminate the changing inertial force and improve the motion smoothness, this work proposes a piezoelectric robot with continuous walking gait inspired by ants. The idea is verified with theoretical models and numerical simulation, and the performances are evaluated with experiments. The robot is proven to have the ability to generate 3-DOF(dgeree of freedom) continuous smooth motions with constant speeds. The maximum and minimum smooth velocities have a difference of six orders of magnitude, realizing cross-scale velocity control. Besides, the motion resolution reaches several nanometers with the unlimited workspace, so the cross-scale displacement control can be also obtained. Furthermore, with great robustness against varying loads, the stable actuation capability of the robot is more than 22 times of the self-weight. To sum up,the proposed robot generates cross-scale smooth motion in both aspects of displacement and velocity, so it has good prospects in the applications requiring steady precision motion. The design philosophy and research methods in this work can be valuable references for further advances of micromanipulation robots.

Stable walking of quadruped robot on unknown rough terrain

Quadruped robot is considered to be the most practical locomotion machine to negotiate uneven terrain, and shows superb stability during static walking. To improve the ability to go over rough terrain, this paper is focused on the stable walking and balance control of quadruped robots. 24 kinds of walking gaits are analyzed in order to derive the most stable and smoothest walking gait. Considering the inefficiency to model a terrain by its specified appearance, a uniform terrain model is established and by means of kinematic analysis, a method to adjust the body posture and center of gravity （COG） height is presented. Simulations demonstrate the effectiveness of the proposed meth- od and the improvement of the adaptation of quadruped robots on rough terrain.

Extended Evolutionary Fast Learn-to-Walk Approach for Four-Legged Robots

Robot locomotion is an active research area. In this paper we focus on the locomotion of quadruped robots. An effective walking gait of quadruped robots is mainly concerned with two key aspects, namely speed and stability. The large search space of potential parameter settings for leg joints means that hand tuning is not feasible in general. As a result walking parameters are typically determined using machine learning techniques. A major shortcoming of using machine learning techniques is the significant wear and tear of robots since many parameter combinations need to be evaluated before an optimal solution is found. This paper proposes a direct walking gait learning approach, which is specifically designed to reduce wear and tear of robot motors, joints and other hardware. In essence we provide an effective learning mechanism that leads to a solution in a faster convergence time than previous algorithms. The results demonstrate that the new learning algorithm obtains a faster convergence to the best solutions in a short run. This approach is significant in obtaining faster walking gaits which will be useful for a wide range of applications where speed and stability are important. Future work will extend our methods so that the faster convergence algorithm can be applied to a two legged humanoid and lead to less wear and tear whilst still developing a fast and stable gait.

Association between improved trunk stability and walking capacity using ankle-foot orthosis in hemiparetic patients with stroke： evidence from three-dimensional gait analysis

Background Restoration of both normal movement of the pelvis and centre of mass is a primary goal of walking rehabilitation in post-stroke patients because these movements are essential components of effective gait. The aim of this study is to quantitatively analyze the effect of ankle-foot orthosis on walking ability, and to investigate the correlation between improvements in trunk motion and walking capacity.

The biomechanical study of lower limb during human walking

The coordinates of the marked points of joints and the changes of foot force in the human walk motion are obtained with systems of motion image acquisition and force measuring.The effects of kinematics and dynamics on the human lower limb in different loads(0,10,20,30 kg) and walking speeds(0.8,1.3,1.7 m/s) have been investigated using the human dynamics model,.The results were as follows.First,with the increasing load,the dorsiflexion angle of ankle joint increased during the procedure of toe-off,the range of motion of the knee joint decreased,the flexion angle of the hip joint increased,and oppositely,the extension angle of the hip joint decreased.Second,with the increasing speed,the range of motion of the ankle joint,the maximum flexion angle of the knee joint,the flexion angle,extension angle of the hip joint and the range of motion of hip joint increased.Finally,the torque and power of the ankle joint,the knee joint and the hip joint increased with the increasing speed and load.The results can provide an important basis for the mechanism design of lower limb power-assisted exoskeleton.

An Experimental Analysis of Overcoming Obstacle in Human Walking

In this paper, an experimental analysis of overcoming obstacle in human walking is carried out by means of a motion capture system. In the experiment, the lower body of an adult human is divided into seven segments, and three markers are pasted to each segment with the aim to obtain moving trajectory and to calculate joint variation during walking. Moreover, kinematic data in terms of displacement, velocity and acceleration are acquired as well. In addition, ground reaction forces are measured using force sensors. Based on the experimental results, features of overcoming obstacle in human walking are ana- lyzed. Experimental results show that the reason which leads to smooth walking can be identified as that the human has slight movement in the vertical direction during walking; the reason that human locomotion uses gravity effectively can be identified as that feet rotate around the toe joints during toe-off phase aiming at using gravitational potential energy to provide propulsion for swing phase. Furthermore, both normal walking gait and obstacle overcoming gait are characterized in a form that can provide necessary knowledge and useful databases for the implementation of motion planning and gait planning towards overcoming obstacle for humanoid robots.

An Experimental Analysis of Stability in Human Walking

Biped locomotion has excellent environment adaptability due to natural selection and evolution over hundreds of millions years. However, the biped walking stability mechanism is still not clear. In this paper, an experimental analysis of walking stability in human walking is carried out by using a motion capture system. A new stability analysis method is proposed based on Zero Moment Point （ZMP） and Sliding Time Window （STW）. The influences of ground friction coefficient, ground slope angle and contact area of support polygon on human walking stability are investigated. The experiment is carried out with 12 healthy subjects, and 53 passive reflective markers are pasted to each subject to obtain moving trajectory and to calculate lower limb joint variation during walking. Experimental results show that ground friction coefficient, ground slope angle and contact area have significant effects on the stride length, step height, gait cycle and lower limb joint angles. When walking with small stability margin, subjects modulate gait to improve the stability, such as shortening stride length, reducing step height, and increasing the gait cycle. These results provide insights into the stability mechanism of human walking, which is beneficial for locomotion control of biped robots.

Modeling and simulation of normal and hemiparetic gait

Gait is the collective term for the two types of bipedal locomotion, walking and running. This paper is focused on walking. The analysis of human gait is of interest to many different disciplines, including biomecha- nics, human-movement science, rehabilitation and medicine in general. Here we present a new model that is capable of reproducing the properties of walking, normal and pathological. The aim of this paper is to establish the biomechanical principles that underlie human walking by using Lagrange method. The constraint forces of Rayleigh dissipation function, through which to consider the effect on the tissues in the gait, are included. Depending on the value of the factor present in the Rayleigh dissipation function, both normal and pathological gait can be simulated. First of all, we apply it in the normal gait and then in the permanent hemiparetic gait. Anthropometric data of adult person are used by simulation, and it is possible to use anthropometric data for children but is necessary to consider existing table ofanthropometric data. Validation of these models includes simulations of passive dynamic gait that walk on level ground. The dynamic walking approach provides a new perspective of gait analysis, focusing on the kinematics and kinetics of gait. There have been studies and simulations to show normal human gait, but few of them have focused on abnormal, especially hemiparetie gait. Quantitative comparisons of the model predictions with gait measurements show that the model can reproduce the significant characteristics of normal gait.