Interruptive Language Control of Bipedal Locomotion

We study the problem of natural language-based control of dynamic bipedal locomotion from the perspective of operational robustness and hardware safety. Existing work on natural language-based robot control has focused on episodic command execution for stable robot platforms, such as fixed- based manipulators in table-top scenarios. These scenarios feature non-overlapping phases of instruction and execution, with execution mishaps usually posing no threat to the robot safety. This allows for non-trivial failure rates to be acceptable. In contrast, our work involves indistinguishable instruction and execution stages for a dynamically unstable robot where execution failures can harm the robot. For example, interrupting a bipedal robot with a new instruction in certain states may cause it to fall. Our first contribution is to design and train a natural language-based controller for the bipedal robot Cassie that can take in new language commands at any time. Our second contribution is to introduce a protocol for evaluating the robustness to interruptions of such controllers and evaluating the learned controller in simulation under different interruption distributions. Our third contribution is to learn a detector for interruptions that are likely to lead to failure and to integrate that detector into a failure mitigation strategy. Overall, our results show that interruptions can lead to non-trivial failure rates for the original controller and that the proposed mitigation strategy can help to significantly reduce that rate.