Analysis of Sensor-Based Real-Time Balancing of Humanoid Robots on Inclined Surfaces

An experimental and theoretical study of real-time robot balancing on inclined surfaces with electrical feedback circuitry is presented. Force sensors are experimentally shown to extend the sustainability of a stable robot posture beyond a critical surface inclination. For this purpose, the inclination feedback from the force sensors is used to adjust the robot's ankle-pitch-motor angle above the critical inclination, thus enabling the maintenance of a stable robot posture. Further, the Inverted Pendulum Model (IPM) (Hemami and Golliday, 1977, Hemami et al., 1973, and McGhee and Kuhner, 1969) is extended to the case of inclined surfaces. Through application of this extended IPM it is demonstrated, that simultaneous use of gyro-sensor data can minimize the necessary initial adjustment of the motor angle for controlled robot-body rotation, which additionally has the positive effect of reducing possible overshoots of the motor's rotation angle during feedback. Consequently, the reported feedback control improves the robot-body stability on inclined surfaces. Efficient implementation of the developed control scheme into an existing robot's electrical system is proposed.