MOTION PLANNING

A computer-implemented method of planning ego actions for a mobile robot in the presence of at least one agent, comprising: searching for an optimal ego action in multiple search steps, each comprising: selecting an ego action from a set of possible ego actions, selecting an agent behaviour from a set of possible agent behaviours, running a simulation based on the selected ego action and agent behaviour, determining a possible outcome, and assigning a reward to the selected ego action, based on a reward metric, wherein selection of the ego action in later search steps is biased towards higher reward ego action(s) but selection of the agent behaviour in later search steps is biased towards riskier agent behaviour(s), a risky agent behaviour being, according to earlier search steps, more likely to result in a lower reward outcome and choosing an ego action based on the rewards computed in the search steps.