Biped Robot Locomotion Research Articles

Hybrid control of biped robots to increase stability in locomotion

This article proposes a new hybrid control method, a combination of impedance control and computed-torque control, to control biped robot locomotion. The former is used for the swinging (or unconstrained) leg and the latter for the supporting (or constrained) leg. This article also suggests that the impedance parameters be changed depending on the gait phase of the biped robot. To reduce the magnitude of the impact and to guarantee a stable footing during foot contact with the ground, the damping of the leg is increased drastically at the moment of contact. Computer simulations of a biped robot, with 3 DOF in each leg and the environment represented by a 3-DOF environment model composed of linear and nonlinear compliant elements, were performed. Simulation results show that the performance of the proposed controller is superior to that of the computed-torque controller, especially in reducing impact and stabilizing the footing. They also show that the proposed controller makes the biped robot more robust to the uncertainties in its own parameters as well as in its environment. © 2000 John Wiley & Sons, Inc.

On control of a base-excited inverted pendulum using neural networks

In this paper a neural-network-based control technique is proposed for stabilizing a base-excited inverted pendulum. The pendulum has two degrees of rotational freedom and the base-point moves freely in the three-dimensional space. The goal is to apply control torques to keep the pendulum in a prescribed position in spite of disturbing base-point movements. First, the problem of modeling such a highly nonlinear, non-autonomous system with neural networks is investigated. The model is then applied within a feedback control loop to keep the pendulum about the upright position. The stability of the control system in the presence of the approximation errors of neural networks is also analyzed. The examination of the proposed controller, through simulations, demonstrates the promise of the methodology and exhibits positive aspects, which cannot be achieved by the previously developed techniques, based on Lyapunov stability analysis. These aspects include fast, yet well-maintained damped responses with smooth control torques. The work presented here, can benefit practical problems such as the study of stable locomotion of human upper body and bipedal robots.

Trajectory generation for biped locomotion robot

The purpose of this research is to generate natural motion for a biped robot. It is difficult to generate stable and natural walking motion in various environments. In this paper, we propose the hierarchical evolutionary algorithm to generate a walking motion through energy optimization and aim to generate a natural motion by considering ZMP. The hierarchical evolutionary algorithm is a co-evolution algorithm of two optimization algorithms, one is the GA that minimizes the total energy of all actuators, and the other is the EP that optimizes interpolated configuration of biped locomotion robot. This hierarchical evolutionary algorithm can find the solution from a large numerical combination area, effectively. We obtain natural walking motions on some slopes using this algorithm, and confirm that the acquired trajectories can be applied successfully to the practical biped locomotion robot.

Kinematic analysis and modelling of biped locomotion systems

This paper presents the kinematic study of robotic biped locomotion systems. The main purpose is to determine the kinematic characteristics and the system performance during walking. For that objective, the prescribed motion of the biped is completely characterised in terms of five locomotion variables: step length, hip height, maximum hip ripple, maximum foot clearance and link lengths. In this work, we propose four methods to quantitatively measure the performance of the walking robot: energy analysis, perturbation analysis, lowpass frequency response and locomobility measure. These performance measures are discussed and compared in determining the robustness and effectiveness of the resulting locomotion.

Natural Motion Generation of Biped Locomotion Robot using Hierarchical Evolutionary Algorithm in the Various Environments

The purpose of this research is to generate natural motion in a biped locomotion robot, like a human walking in various environments. In this paper, we report on biped locomotion robots. We apply a hierarchical evolutionary algorithm in order to generate the trajectory of a biped locomotion robot through energy optimization, and attempt to generate a more natural motion by considering the dynamic effect. The hierarchical evolutionary algorithm consists of two layers: one is the GA layer which minimizes the total energy of all the actuators, and the other is the EP layer which optimizes the interpolated configuration of the biped locomotion robot. Then we formulate a trajectory generation problem as an energy minimization problem and we apply the hierarchical evolutionary algorithm. Furthermore, we build a trial biped locomotion robot which has 13 joints and is made of aluminum. Finally, we confirm that the calculated natural motion trajectory can be applied successfully to practical biped locomotion.

Biped robot locomotion in the sagittal I plane

This paper describes the control system for an eight-degree-of-freedom biped robot built at the University of Salford. The controller enables the robot to walk in the sagittal plane on smooth level terrain and is essentially an observer-based controller utilising state feedback, integral action and feedforward control. The robot posture is controlled by selecting constant reference set points for the control system. Locomotion is achieved by suitably modifying the reference set points. The robot walks with a step length of approximately 0.3 m and a speed of about 0.03 m/s.

Study of lower level adaptive walking in the sagittal plane by a biped locomotion robot

Walking according to changes in the environment is called adaptive walking. We define lower level adaptive walking as a walk consisting only of trajectory control and walk-pattern generation. The purpose of this study was to realize lower level adapting walking in the sagittal plane by a biped locomotion robot in indoor space. In this paper, we propose a simplified procedure of walk-pattern generation, which is that walk patterns for various environments are generated by adjusting and combining the basic walk patterns which have previously been given for typical environments. Based on this idea, walking experiments were carried out for various environments. As a result, dynamic walking in a flat plane (about 1.5 s/step with a 0.3 m step width), changes of the step width in walking, and walking in various environments combined from a flat plane, an obstacle (such as a pipe) and a stair (up and down) were realized.

二足歩行ロボットによるＳａｇｉｔｔａｌ ｐｌａｎｅ内の下位レベル適応歩行に関する研究

Walking according to change of various environments is called an adaptive walking. We define the lower level adaptive walking as a walk consisted of only trajectory control and walk-patern generating. The purpose of this study is to realize the lower level adaptive walking in sagittal plane by a biped locomotion robot in indoor space.In this paper, we propose a simplified procedure of walk-pattern generation as follows that walk-patterns for various environments are generated by adjusting and combining the basic walk-patterns which are previously given for typical environments. Based on this idea, walking experiments are carried out for various environments. As a result, dynamic walking in flat plane (about 1.5 second per a step with 0.3 m), change of step width in walking and walk in various combined environments of flat plane, an obstacle as pipe and a stair (up, down) are realized.

Control of a Dynamical Biped Locomotion System for Steady Walking

A dynamic biped locomotion robot which realizes high speed movement is presented. Its walking cycle is about 0.45 s, its speed is about 0.8m/s, and its appearance resembles a human walking. A hierarchical control structure is adopted at the lower level at which the local feedback is implemented. The reference signal to each local controller is supplied from its higher level. The stability of steady walking is examined by using the reduced order model which has been derived by the authors and it is assured by experiments.

角運動量を考慮した2足歩行ロボットの動的制御

角運動量を考慮した2足歩行ロボットの動的制御

A Hierarchical Forecast Control of a Dynamica Biped Locomotion System

A hierarchical structure for the control of a dynamical biped locomotion robot is presented. High gain local feedbacks at the articular joints for making the biped locomotion robust are implemented as the control in the lower level. In the upper level, the reference signal to the local feedback is generated by using a new low order model which is connected to the actual biped locomotion and which gives a good approximation for almost all walking. The anguler momentum is controlled in the hierarchical control structure, since it must be manipulated in many walking motions such as the start-up motion, the stop motion and the recovery motion from the disturbance. The system in our study can talk dynamically and continuously at the speed of 0.8 m/sec. The experiment which is carried out in real-time control shows satisfactory results.