A self-propelled type of wheelchair with hand-rims has both advantages and disadvantages of operators. The former is to offer the convenience of mobility and the later is operator's fatigue. As a solution of this problem, wheelchairs, which are equipped with a power assist control system, are needed. In this research, the model based on the quantitative human-wheelchair system was proposed. In this paper, we considered about the coasting ability of this system and the braking performance with the use of hand-rims. The subject participated in a brake test in order to reduce braking distance by using the test machine that can provide an adjustment of inertia. The human characteristics in braking a wheelchair were described the influence of inertia to the braking performance.