A simple control algorithm for controlling biped dynamic walking with stopping ability based on the footed inverted pendulum model

Pengfei Wang,Fusheng Zha,Guocai Liu,Wei Guo,Mantian Li,Hegao Cai

doi:10.1177/1687814016670283

Pengfei Wang, Fusheng Zha + Show 4 more

Open Access

https://doi.org/10.1177/1687814016670283

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Abstract

In biped walking, dynamic balance ability is an important evaluation index. Zero-moment-point-based trajectory control is a common method for biped dynamic walking, but it requires complex control mechanisms that limit its applications. With the help of passive dynamics, the biped walking based on the inverted pendulum model can achieve dynamic walking in a simple way; however, it has no stopping ability, which is necessary for practical use. To solve this problem, this article proposes a footed inverted pendulum model and develops a simple three-part decomposition control algorithm for controlling biped dynamic walking based on the model. In the control algorithm, the biped walking is decomposed into three separate control parts: body posture, body height, and body velocity. Body posture is controlled by the stance hip, body height is controlled by the stance knee, and body velocity is controlled by the stance ankle and swing foot placement simultaneously. A simulation is presented to analyze the foot’s effect on the inverted pendulum model. Two hardware experiments exploring velocity control and balance are described, with the results showing that the biped can achieve dynamic walking with stopping ability by using the simple control algorithm based on the footed inverted pendulum model.

Highlights

Robots that move on two legs are called biped robots
Biped robots fall down compared to the wheeled robots, four- or more- legged robots, such that the dynamic balance ability is an important evaluation index for biped walking
According to the published paper, humanoid robots such as those created by the Humanoid Robotics Project,[5] Honda,[6] and the Korea Advanced Institute of Science and Technology[7] utilize zero moment point (ZMP)-based trajectory control

Summary

Introduction

Robots that move on two legs are called biped robots. Biped robots fall down compared to the wheeled robots, four- or more- legged robots, such that the dynamic balance ability is an important evaluation index for biped walking. The body height zst is controlled by the stance leg length lst, the body pitch angle ub is controlled by the stance hip torque thst, and the body velocity x_st is controlled by the stance ankle torque tast and the swing foot placement xsw for touchdown. If the body height maintains a constant value z0, substituting zst = z0 and €zst = z_st = 0 into equations (5) and (12) yields the new dynamic equations for the FIPM as follows mg z0 xst

Results

Conclusion