The sensation of the contact is indispensable for the contact task. In this chapter, the instantaneous value of the force/tactile sensation is defined and quantified as the ratio of the force and the velocity. The absolute value is also defined by the rms value with the definition of the time window. This value is extended to the frequency domain with the four parameters, which are also the admittance of the contact object. The operating point of the contact task in the force–velocity plane should be the crossing point of the characteristics of the actuation and the mechanical load. This is the same as the coincidence of the force/tactile sensation with the admittance of the contact object. Since the admittance of the contact object is varied according to the motion, such a coincidence should be maintained by the feedback mechanism. As a result, the feedforward system to define the mission of the contact and the feedback system for the matching the admittance is the essential structure of the contact task. That is shown by the figures and the experimental  results.