Vibration attenuation of robot hands using an inertial measurement unit during a humanoid robot walking

Abstract

When a humanoid robot is walking, it is common that movement of the upper body is interrupted by motion of the waist or vibration which occurs at the sole of the robot when it collide with the ground, For carrying stuff stably, the level control is needed for the hands of the robot to compensate those interrupts conveyed to the hands. IMU(Inertial Measurement Unit) was used to feedback the height level information. Double integration of the acceleration signal is subject to bias or drift. In this research, the analog integrator with high pass filter was introduced to have less quantization error than the digital integration filter. And also, for compensating the height level, extra joint angles are added to input reference angles using a numerical iteration method as an inverse kinematics. For proper coordinate transformation of the detected signal, tilt information was used along experiments. The frequency experiments with given sine pulse input were performed for system modeling to analyze the system or design the compensator instead of analytical system modeling. Using 5Hz spill-over filter in front of the system, the test result can be convincible even in the high frequency. Using system modeling, optimal controller with observer was designed and parameters were selected for better response in the simulation. And also after several experiments, the $5^{th}$ order pole placement was conducted based on the poles’ location from the optimal controller. Finally, the specific range compensator and the broad range compensator were designed and results of those compensators were explained by sensitivity functions in which smaller value in magnitude means better performance of against disturbance.