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The lift-and-carry of non-rigid objects is challenging for both people and bipedal robots. Examples include lifting and carrying jugs, jerry cans or bags that are respectively filled with water, gasoline or sand. Carrying such objects often makes it difficult to walk due to the shifting center-of-mass. As such, tripping and falling are risks. Such lift-and-carry is a common material handling task...
This paper introduces a novel control system of bipedal robots on uneven terrain. Since this method does not require to measure Zero Moment Point (ZMP), the tracking performance of the controller is not deteriorated by the noise on a measured ZMP. Moreover, the robot withstands frequent perturbations because of its two-degree-of-freedom structure. The robot is stabilized by Center of Mass (COM) regulation...
The zero moment point (ZMP) control method is usually used in stable biped walking. A novel preview control of ZMP is proposed in the paper. First, the dynamics of a biped robot is modeled as a running cart on the table which gives a convenient representation to treat ZMP. Second, the walking pattern generation process is describes in details and a presented preview controller is introduced to reduce...
In this paper, we propose a gait transition strategy for a quadruped robot using the Hopf Oscillator model and trajectory planning. The Hopf Oscillator model is used to generate rhythmic moving pattern during trot gait, and trajectory planning based on the Stability Margin (SM) is employed to implement walk gait as well as the transition between walk gait and trot gait. Especially, we develop a moving...
The balance has been widely studied over the last decades due to its importance in people independence. This allowed formulating models of human balance strategies. They are mainly based on inverted pendulum dynamical model stabilized with a feedback controller that keeps the Centre of Mass (CoM) within a stable trajectory within the Base of Stability (BoS). When a perturbation is applied the controller...
One of the primary advantage of walking machines is their inherent capacity to operate in different terrains. However, it is necessary a locomotion system for planning in advance future footholds, and to modify the robot gait in order to maintain the platform stability. Several locomotion systems have been developed for rectangular hexapod robots, in this work a system for radially a symmetric hexapod...
For an underactuated biped on a constant-slope terrain, the hybrid zero dynamics (HZD) controller framework provides exponentially stable walking motions. In this paper, we quantify the stability of such a control system on rough terrain by estimating the expected number of steps before failure. In addition, we show how to switch between multiple HZD controllers (optionally using terrain look-ahead)...
An optimal trajectory generation method named the double generating functions method is proposed, recently. Since the on-demand computation for different step lengths and different step periods is almost zero, it would be very useful to the real robot walking control. However, the stability of the generated trajectory is not considered. This paper proposes a cost function containing the term of Zero-Moment...
A second order sliding mode controller is modified to form a continuous homogeneous controller. Uniform finite time stability is proved by extending the homogeneity principle of discontinuous systems to the continuous case with uniformly decaying piece-wise continuous nonhomogeneous disturbances. The modified controller is then utilised to track reference trajectories for all the joints of a fully...
In this paper, we present a system that enables humanoid robots to imitate complex whole-body motions of humans in real time. In our approach, we use a compact human model and consider the positions of the endeffectors as well as the center of mass as the most important aspects to imitate. Our system actively balances the center of mass over the support polygon to avoid falls of the robot, which would...
In the present paper, a control method of speed regulation in dynamic walking for biped robots is proposed. First, principle of speed control by regulation of input energy is studied based on simplified model. The advantage is able to regulate the speed and the step length synchronically, which is inspired by the way of human walking. Second, a practical control method for a 13-link bipedal robot...
The design of a controller which can achieve a steady and stable walk is crucial in bipedal humanoid robotics. Reference trajectory generation is central in the walking control. The Zero Moment Point (ZMP) criterion is the most widely used stability criterion for trajectory generation. It is most successfully used when the ZMP equations are coupled with the dynamics equations of a simple mechanism,...
This paper proposes a method to change the speed of gallop for a quadruped robot by controlling the vertical ground reaction forces. For easy and stable galloping of a quadruped robot, the basic motion of each foot with respect to its main body is expressed by an elliptic path. The elliptic footpath is simple, efficient and quite similar to that of a four-legged animal. The desired GRF is computed...
To achieve a balanced walking for a humanoid, it is necessary to estimate the dynamic stability of the system. However, in a small size humanoid with restricted system resource, it is hard to satisfy the performance level desired by dynamics analysis. Therefore, in this paper, we propose the feasible methods to generate gait pattern and stabilize walking based on coupled oscillators which have a clear...
This paper proposes a balance control method for a biped based on passivity. In this method, we design a controller to stabilize the position of the center of mass (COM), the orientation of the upper body and the motion of the swing leg using the kinematic model of a biped. The proposed method is not hindered by complexity of the computation because the proposed controller executes no contact force...
An improved ZMP (Zero Moment Point) trajectory for a biped robot is designed in this paper, which imitates a human's actual ZMP trajectory in the walking process. A new method of walking pattern generation based on forward moving ZMP in SSP (Single Support Phase) is also provided. It can keep the ZMP moving forward instead of staying in the center of supporting region during SSP, which is helpful...
The purpose of this paper is to have a better understanding of the function of human flat foot. To analyze its dynamics, we propose a passive rimless wheel with asymmetric flat feet. The model has a point mass in center and massless spokes. The rigid asymmetric flat feet were equipped at the end of spokes. The walking process of this model which has “heel-strike” and “toe-strike” is similar to human...
The aim of this study is to develop a system for extracting information during postural stability tests, using a new capacitive force sensor conceived and made by us. Based on the capacitive force sensor, we developed a pedometric force plate (PFP) for use in human postural and gait analysis. We present the method of data acquisition, the signal processing and the results obtained. For determining...
When a humanoid robot moves in an actual working environment, it is necessary for the robot to generate appropriate locomotion trajectory in real-time to ensure its stability. But it is difficult to solve nonlinear differential equations of stability constraints in real-time to get stable locomotion trajectory. This paper proposed a method to generate stable and smooth locomotion trajectory through...
Existing lower extremity exoskeletons lack sufficient foot support area to guarantee safe operation for rehabilitation of patients, and normal posture/gait for users carrying heavy loads on backpack. In order to enhance the stability of lower extremity exoskeletons, an adaptive foot system is presented. It consists of two foot extensions, one extending behind the toe and another on the heel side that...
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