To improve the adaptability of the multi-legged robot in rough terrain, a robotic foot capable of 3-axis force sensing is designed. The designed robotic foot is composed of five components, namely, a sensing ball, a fixed plate, 4 1-D force sensors, a base and a preloading bolt. The 4 force sensors are mounted symmetrically with 45° inclination angle in the base slots. According to the component forces detected by the force sensors in horizontal and vertical directions, the contacting force between the robotic foot and the environment can be calculated. The 3-axis force sensing principles of the robotic foot are analyzed. Based on that, an ADAMS model is established to verify the theoretical analysis. Through the sensor calibration experiment, it is found that the force exerted by preloading bolt and the material of the sensing ball have a great influence on the the 3-axis force sensing characteristics of the designed robotic foot. Finally, calibration tests of an optimized robotic foot are conducted with the selected preload and material, and the transformation matrix between voltage and force is obtained by using least square optimization method. The calibration results show that the robotic foot achieves an force sensing accuracy of ± 11.3% in X and Y directions, and ± 9.4% in Z direction.
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