Model predictive obstacle avoidance control with passage width constraints for leg/wheel robots

In this paper, we propose a model predictive obstacle avoidance control method for leg/wheel robots with 3 DOF SCARA legs. This robot is able to pass through a narrow space because it can extend and shrink the size between the wheels by changing the configuration of the legs. In this study, obstacle avoidance is achieved by two passage width constraints. Obstacle size and wheel positions are considered in those constraints. A distance between the robot and an obstacle is kept larger than a value specified by those constraints. Comparing with conventional artificial potential methods, the proposed method does not require tuning of obstacle parameters. We utilize two kinds of linear constraints. In the first constraint, we use the internal common tangent between the robot and the obstacle nearest to the robot. In the other constraint, we use the external common tangent to reduce getting stuck into the narrow space between obstacles. The optimal tracking control is realized using those constraints for the model predictive control. The efficacy of this method is verified via the numerical simulations.