Graduate School of Engineering, Hiroshima University, Higashihiroshima, Hiroshima 739-8527, Japan.
HiSIM Research Center, Hiroshima University, Higashihiroshima, Hiroshima 739-8530, Japan.
Sensors (Basel). 2020 Dec 12;20(24):7139. doi: 10.3390/s20247139.
An efficient motor-control system for stable walking of the lightweight humanoid robot KONDO KHR-3HV on inclined surfaces is investigated. The motor-control system is based on the angular velocity of the pitch motion of the robot, which is detected by a gyro sensor attached to the robot torso and referred to as the angular-pitch velocity. The robot gait is analyzed for different downslopes with and without the motor-feedback control. A novel method of frequency-domain analysis of the angular-pitch velocity is proposed for explaining the reasons behind the instabilities of dynamic humanoid-robot walking on inclined surfaces. The results show, that a nonlinear nature of the motor torque, due to a force induced by the slope, gives rise to harmonics of the fundamental walking frequency of 1.73 Hz. These harmonics are the origin of the unstable robot walking. Additionally, the feedback-gain parameters and affect the amplitudes of the harmonics, which give rise to vibrations at a higher surface inclination. Increased surface friction allows a reduction of the feedback gain, which reduces this specific contribution to the harmonics and thus stabilizes the robot. To improve the walking stability on inclined surfaces, it is found that the damped natural frequency of the motor-control system must be kept lower than the fundamental walking frequency.
研究了一种用于轻型人形机器人 KONDO KHR-3HV 在倾斜表面上稳定行走的高效电机控制系统。电机控制系统基于机器人俯仰运动的角速度，通过安装在机器人躯干上的陀螺仪传感器检测到，称为角俯仰速度。分析了机器人在有和没有电机反馈控制的不同下坡时的步态。提出了一种角俯仰速度的频域分析新方法，用于解释动态人形机器人在倾斜表面上行走不稳定的原因。结果表明，由于坡度引起的力，电机扭矩的非线性性质会产生基本行走频率为 1.73 Hz 的谐波。这些谐波是机器人不稳定行走的根源。此外，反馈增益参数 和 会影响谐波的幅度，这会导致在更高的表面倾斜度下产生振动。增加表面摩擦可以降低反馈增益，从而减少谐波的这种特定贡献，从而稳定机器人。为了提高在倾斜表面上的行走稳定性，发现电机控制系统的阻尼自然频率必须保持低于基本行走频率。
