Home oxygen therapy(HOT) is a medical treatment for patients suffering from severe lung deseases.〓Although walking outdoors is recommended for patients to maintain physical strength, patients always have to carry a portable oxygen supplier which is not sufficiently light weight for this purpose.〓Our ultimate goal is to develope a mobile robot to carry an oxygen tank and follow a patient in an urban outdoor environment.〓We have proposed a mobile robot with mechanisms with considering the usability.〓The leader following control algorithm is also improved and its effectiveness is demonstrated in an outodoor and indoor experiment.〓