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This paper presents a method to determine contact conditions between a planar end-effector and the environment, i.e., face-to-face, face-to-line, or face-to-point contact. First of all, two kinds of contact motion of a planar end-effector, i.e., passive and active contact motions, are described. A compliance controller is implemented to achieve the passive contact motion, and the 'groping motion' is generated as the active contact motion. Then, novel robot-friendly expressions of the environment are proposed based on the concept of environmental modes. Discrete Fourier transform matrices are utilized as matrices transforming environmental information into environmental modes. In the experiments, a planar end-effector contacts with the environment with the passive and active contact motions, and the environmental data obtained from sensors are transformed into environmental modes. The profiles of the extracted environmental modes are utilized to determine the contact conditions. The validity of the proposed method is confirmed by the experimental results. Index Terms--Compliance control, discrete Fourier transform (DFT), disturbance observer (DOB), environment recognition, environmental mode, haptics.

This paper describes a novel bilateral grasping control system including master-slave robots with different degree of freedom. The master and slave controllers are designed based on a multilateral control scheme. Decoupling design of force and position controllers is realized by mode transformation using the discrete Fourier transform matrices and a disturbance observer. In the proposed system, a human operator manipulates two master robots, and three slave robots grasp an object cooperatively. The proposed system makes it possible to grasp an object tightly in the slave side and to transmit feeling of grasping to a human operator vividly. The validity of the proposed method is shown by numerical and experimental results. Index Terms--Bilateral control, discrete Fourier transform (DFT), disturbance observer (DOB), grasping control, haptics, multilateral control.

Active queue management techniques have been proposed to mitigate serious congestion issues caused by transmission control protocol flows. Active queue management controllers based on control theory are superior in terms of control performance. Such a controller utilizes a target queue length as a control input, and the congestion control system attempts to maintain the actual queue length close to the target value. However, the specific setting of the target queue length has not been discussed sufficiently. For example, raising or lowering the target queue length may increase goodput or reduce queueing delay, respectively. Therefore, the target queue length should be appropriately generated according to the required quality of services and buffer status. This paper proposes a quality of services–aware adaptive target queue length generation algorithm for an active queue management controller based on control theory. The proposed algorithm comprises two modes (loss‐aware and delay‐aware modes) and attempts to raise or lower the target queue length by considering the buffer status to increase the goodput or reduce the queueing delay. Simulation results revealed that the proposed algorithm could increase goodput or reduce queueing delay on each mode by adapting to the buffer status, which is in contrast to conventional methods. [ABSTRACT FROM AUTHOR]