Optimum Walking Design for Biped Robots Based on the Improved Inverted Pendulum Model

Document Type : Research Article

Authors

Department of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran.

Abstract

The Spring-Loaded Inverted Pendulum (SLIP) model limits the controllability and mobility of biped robots in walking due to its omission of the ankle joint. This paper proposes a new walking pattern, titled "Optimized Step Design for Biped Robots Based on an Improved Inverted Pendulum Model," known as the Variable Spring-Loaded Inverted Pendulum with Finite-sized Foot (VSLIP-FF) model. Inspired by human walking characteristics, an adaptive strategy for leg extension and contraction is proposed for step planning, effectively emulating the role of the ankle joint. Finally, we examine the position and velocity of the robot’s center of mass with the VSLIP-FF model during walking on surfaces with varying friction. This stability and adaptability are crucial for the practical use of biped robots on diverse terrains. Simulation results for the model in the stated conditions show that it maintained stability on both flat and inclined surfaces with an 8% slope, exhibiting human-like behavior and achieving longer strides in a shorter time compared to the SLIP model. Friction conditions for the model on flat surfaces were also evaluated; based on this model’s parameters, if the friction coefficient is greater than or equal to 0.047, the friction between the robot's foot contact surface and the ground is static. Otherwise, it is classified as kinetic (sliding) friction.

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Main Subjects

References

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Amirkabir Journal of Mechanical Engineering
Volume 57, Issue 4
July 2025
Pages 417-452

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