Real-Time FPGA-Based Balance Control Method for a Humanoid Robot Pushed by External Forces

Abstract

In this paper, a real-time balance control method is designed and implemented on a field-programmable gate array (FPGA) chip for a small-sized humanoid robot. In the proposed balance control structure, there are four modules: (1) external force detection, (2) push recovery balance control, (3) trajectory planning, and (4) inverse kinematics. The proposed method is implemented on the FPGA chip so that it can quickly respond to keep the small-sized humanoid robot balanced when it is pushed by external forces. A gyroscope and an accelerometer are used to detect the inclination angle of the robot. When the robot is under the action of an external force, an excessively large inclination angle may be produced, causing it to lose its balance. A linear inverted pendulum with a flywheel model is employed to estimate a capture point where the robot should step to maintain its balance. In addition, the central pattern generators (CPGs) with a sinusoidal function are adopted to plan the stepping trajectories. Some experimental results are presented to illustrate that the proposed real-time balance control method can effectively enable the robot to keep its balance to avoid falling down.