Motion control in open environment will be more and more important The recent machines are required to have an ability to contact with unknown environment. The environmental information is a key to be compliant to unknown environment This paper develops a novel viewpoint of motion control based on quarrying of environmental information. The quarry process means to abstract and express the environmental information by its inner variables- A disturbance observer is a basic technology for quarry process and attainment of' robust acceleration control. Since the disturbance observer can observe the external force from the environment without force sensors, adaptive ability to environmental changes is improved. A haptic ability is also important for cooperative motion with a human. It means that a robot should control the interaction. Once such kind of ability is installed, then it becomes cooperative with humans. Since the control stiffness of ideal force control is zero, cooperation of a human and a robot is realized through force control. The proposed method is applied for a power-assist wheelchair. Human operationally and safety at the collision to obstacles are improved. As a result, compliant motion to unknown environment is attained. The experimental results show viability of the proposed method.