At present, Japan faces the issues of population decrease and a super-aging problem, and it is estimated that the number of persons who are difficult to move by oneself will be increased. Front-wheel-drive wheelchairs have good running characteristics. For example, easy to turn around and getting over bumps. However, it includes a bad characteristic of low straightness behavior called "fishtail". The goal of this study is to explore the mechanisms involved in the "fishtail" and improve operability of front-wheel-drive wheelchairs. In this report, we built a human-wheelchair model and performed simulations to verify how parameters of the human model affect the wheelchair behavior. Based on these results, we devised a control method to improve operability of front-wheel-drive wheelchairs. Finally we confirmed the usefulness of our method by single lane change simulations, automatic driving experiments and also driving experiments controlled by human subjects.