The difficulty of a physical foundation model is no less than that of an LLM. Take clearing a table as an example: the robot must first recognize objects, then determine the grasping order, plan movement paths, and continuously adjust strategy based on environmental changes after each action. If there are b choices at each moment and completing the task requires H consecutive decision steps, the possible paths grow to b^H; if there are 10 choices per step and 20 consecutive decision steps, the theoretical number of paths explodes to an unimaginable order of magnitude. This is the combinatorial explosion in long-horizon decision-making.
Zhang Hanwang's research is directly related to this problem. In the physical world, statistical correlation alone is insufficient to support stable action: an object's movement may come from robot action, or from gravity, collision, or external disturbance; only by understanding the causal relationship between actions and outcomes can the model make more reliable judgments; the same applies to generalization—if it only memorizes object appearances and robot poses in training data, capabilities may fail when materials, lighting, or embodiments change. His research on causal learning and debiasing can precisely reduce the model's reliance on surface correlations.
Based on this framework, Xirang splits LPM into six mutually cooperating underlying capability foundations: Unified Token is responsible for converting heterogeneous information such as vision, action, touch, and force into representations that can be processed together; Unified Architecture is responsible for organizing state understanding, reasoning, action, and future prediction within the same model; reinforcement learning allows the model to update strategies from action outcomes; the data system provides learning materials; the evaluation system tests whether the model has learned true physical laws or false surface relationships; the engineering foundation determines whether this approach can run at sufficiently large data and compute scales. This forms a closed loop: data is converted into unified representations, the model generates actions and predicts consequences, actions enter simulation or the real environment for testing, rewards and evaluations turn results into feedback, and the experience of success and failure re-enters training.