Online maintaining behavior of high-load and unstable postures based on whole-body load balancing strategy with thermal prediction

Whole-body motions involving contacts in some complex terrains may become sometimes high-load and unstable ones. These kinds of motions have a novel problem not considered in the previous studies: integration of load. For example, in the situation of a electric motor subjected to some high loads, motor temperature will increase as integrating loads, and finally, fatal accident such as melting of motor coils would happen. In this study, we introduce a novel behavior control strategy for load balancing that the robot moves whole body during execution time in order to balance whole-body load while keeping contacts with environment. It is a well-known strategy for behavior control and motion generation to control the center of gravity position of robots for balancing. Besides, in the recent studies, optimization methods are also used for the purpose of satisfying constraints for posture maintenance and achieving more complex contact states. The important point of these optimization strategies is how to design the objective function. We designed the objective function as a barrier function of physical constraints and a function which is more larger with more higher motor temperature. By controlling the center of gravity according to this objective function, it is possible to achieve both load balancing and keeping complex contact states such as balancing on a ladder. At last, we confirm the effectiveness of our strategy for the long-sustained maintenance of high-load and unstable postures through three experiments of posture maintenance: crouching posture on a flat ground, balancing posture on a ladder and crawling posture on a flat ground.