Fat-tree-based optical network-on-chip (FONoC) is an emerging architecture that enables next-generation computing platforms to achieve ultimate performance and energy efficiency. However, the architecture suffers from high insertion loss, which degrades energy efficiency and signal reliability severely. Focusing primarily on microring resonator (MR) drops, we analyze the relationship between the insertion loss caused by MR drops and the routing paths in the FONoCs. Our approach involves developing a simplified graph model named a drop-characterized fat-tree graph with vertex indexing. We propose three types of routing algorithms: 1) insertion loss-minimized deterministic routing; 2) minimized loss path-prioritized adaptive routing; and 3) insertion loss-constrained adaptive routing. Furthermore, we present the associated optical router architectures and additional insertion loss optimization by minimizing the number of waveguide crossings. Based on our simulation results for the latency, throughput, energy efficiency, and MR activation power, we discuss the tradeoffs and suggest appropriate optimization techniques to be adopted according to the priorities of the design goals.

This paper presents tracking algorithms of a mobile robot that follows a human body moving at high speed in unstructured outdoor environment. The mobile robot, which is a differential-driven wheel type, is equipped with one laser range finder to perform high-speed human tracking and obstacle avoidance. Initially, the waist part of the human body is found the best part of the human body for robust tracking by a laser range finder. Next an obstacle avoidance algorithm considering the relative velocity between the robot and obstacles is proposed. It is shown that the proposed human tracking algorithms based on the Kalman filter performs well even in the case of the target occlusions and temporary losses. These tracking algorithms have been applied to a marathoner following robot that carries the marathoner's personal belongings in many different outdoor environments.

This work deals with navigation of an omni-directional mobile robot with active caster wheels. Initially, the posture of the omni-directional mobile robot is calculated by using the odometry information. Next, the position accuracy of the mobile robot is measured through comparison of the odometry information and the external sensor measurement. Finally, for successful navigation of the mobile robot, a motion planning algorithm that employs kinematic redundancy resolution method is proposed. Through experiments for multiple obstacles and multiple moving obstacles, the feasibility of the proposed navigation algorithm was verified.

This paper investigates a collision-free navigation algorithm for a mobile robot to work in daily environment which includes multiple walking people. The proposed algorithm consists of two main parts: recognizing walking people and collision-free path planning. For the recognition of randomly changing human walking motion, a people tracking method using laser range finder (LRF) is utilized. Robust people tracking could be achieved by embedding a new biped model with a walking frequency tracker, which can estimate the frequency of human walking motion and generate it continuously even in the case of no measurement owing to occlusion. For the other part, collision-free path planning, an iterative forecast and planning method with the concept of configuration space including space and time is employed. The position and velocity of walking people, given from people tracking algorithm, are exploited in path planning part as the information of obstacles that the robot have to avoid. The proposed method has been implemented on a real robot. It is also demonstrated with some experiments the tracking of multiple walking humans and robot navigation in indoor environment.

This work deals with a motion planning algorithm of an omni-directional mobile robot with active caster wheels. A typical problem occurred in the motion control, which has been identified through experimental experiences, is skidding of the mobile wheel. It sometimes results in uncertain rotation of the steering wheel. This is due to mismatching between the command and the mechanical hardware. To cope with this problem, a motion planning algorithm pursuing the natural configuration of the mobile wheel was mainly investigated, which resolves the skidding problem and uncertain motions of the steering wheel. Through simulations and experimentation, the feasibility of this algorithm was verified.

To monitor multiple moving objects from a robot in motion is an essential technology in robotic application areas including service and security for human daily life. For this, a method to track multiple walking humans using a mobile robot "in motion" with laser range finder (LRF) is investigated in this paper. Geometric characteristics of human legs are considered to detect their position from the LRF data. Frequency and phase of walking motion are extracted using a pendulum model of the angle between two legs and extended Kalman filter. The algorithm with human walking model anticipates the position of moving humans. The effectiveness of the proposed method is also evaluated with some experiments to track multiple walking humans in indoor environment. An experimental testbed which consists of a mobile robot "Yamabico" and a LRF is employed to track people. Resultant experiments and analysis showed that multiple walking people are tracked well from a mobile robot with the proposed method

Despite that omni-directional mobile robots have been investigated and used popularly, there are rarely useful command systems and control methods for practical applications. In this research, a command system to describe the navigation task for an omni-directional mobile robot is developed, and a motion generation method considering the robot geometry and the given trajectory is proposed. Furthermore, a control method to track the given linear and circular trajectories is proposed. A closed form kinematic model was utilized for motion generation and control as well. A redundantly actuated omni-directional mobile robot that consists of three caster-type wheel mechanisms with high performance embedded controller module was developed for the experiments. And some experiments in the real environment were carried out to verify the effectiveness of the proposed command system and the performance of the motion generation and the trajectory control method.

This paper deals with motion generation algorithm considering the external and internal impulses. Initially, we analyze the trend of the impulses with a simple 3-DOF planar robot arm in various contact positions and present a problem that is in discord with the general trend. To cope with this problem, we propose a new motion generation algorithm considering both the external and internal impulse. The gradient projection method is employed to exploit the kinematic redundancy of robot systems. Initially, the effectiveness of the proposed algorithms is verified through simulation of a 3-DOF planar robot arm model, and two application examples considering both the external and internal impulses are investigated. Through simulations for the landing of a 4-DOF planar human-body model and the sawing motion by a dual-arm model, it is shown that the posture is stable and the trend of the impulses calculated by the analytical models is coincident to the human experiences.

Some of manufacturing tasks, such as sawing, often require continuous impulsive motion. In the case of sawing, such impulsive motions can be observed between the teeth of the saw and the object. The amount of the external impulse exerted on the object has been treated as an important control parameter. At the same time, the internal impulses experienced at the joints should be taken into account to avoid serious damage or injury at the joints of robot. The purpose of this paper is to improve the efficacy of sawing by using dual arms. For this, we suggest an external impulse model, and introduce a new concept of effective mass that accounts for the hardness of the object to corroborate the effectiveness of the proposed chip model employed in the derivation of the external impulse model. Closed-form internal impulse models are also proposed for both single and dual arms. Based on these models, the paper proposes a new measure for internal impulse. A normalized impulse ellipsoid reflecting the velocity direction is employed to visualize the impact geometry. Finally, we identify the optimal sawing region, wherein there is a maximum amount of external impulse and a minimal amount of the internal impulse. Simulation and experimentation demonstrate that the dual arm exhibits a better sawing performance than a single arm, in terms of external and internal impulses.

It is known that parallel type mechanisms have many singularities than serial type mechanisms. In haptic application, these singularities deteriorate the force reflecting performance. Moreover, different from general manipulators, haptic systems can't avoid the singular point, because they are operated by the user's random motion command. Although many singularity-free load distribution algorithms for kinematically redundant manipulators have been proposed, singularity-free load distribution algorithms for parallel haptic application have not been deeply discussed. In this work, various singularity-free load distribution algorithms that are appropriate to parallel haptic system are discussed. A new 6 DOF parallel mechanism equipped with four sub-chains is employed as a test device. To cope with singularity problem, four task-priority algorithms and redundant actuation algorithm are discussed and compared through simulation, and also experiments have been performed to show the effectiveness of those algorithms at the presence of singularity.

Some of manufacturing tasks such as sawing task often require continuous impulsive motion. In case of sawing task, such impulsive motions can be observed between the teeth of the saw and the object being sawn. The amount of the external impulse exerted on the object is treated as an important control parameter in the sawing task. The purpose of this work is to show the efficacy of sawing task by using a dual-arm. For this, a new concept of effective mass is introduced to model the impact phenomenon in the sawing task. Using this concept, the external impulse model of sawing tasks is suggested. The optimal sawing region is identified in which the amount of external impulse is maximized. It is demonstrated through simulation and experiment that the dual-arm exhibits better sawing performance over a single arm in aspects of external impulse.

It is known that parallel-type mechanisms have more singularities than serial-type mechanisms. In haptic application, these singularities deteriorate the system performance generating reflecting force. Moreover, different from general manipulators, haptic systems can't avoid the singular point, because they are operated by user random command. Although many singularity-free algorithms for serial mechanisms have been proposed and studied, singularity-free algorithms for parallel haptic application have not been deeply discussed. In this paper various singularity-free algorithms, which are appropriate to parallel haptic system, will be discussed. Furthermore, to overcome singularity problems, a new design including redundant actuation is proposed. The proposed mechanism has fairly large workspace and is relatively light by employing non-floating actuators.

Some of manufacturing tasks such as sawing task often requires continuous impulsive motion. In case of sawing task, such impulsive motions can be observed between the teeth of the saw and the object. The amount of the external impulse exerted on the object has been treated as an important control paramete. Also, the internal impulses experienced at the joints should be simultaneously taken into account to avoid serious damage or injury at the joints. The purpose of this work is to improve the efficacy of sawing task by using dual arm. For this, an external impulse model for sawing task is suggested. Also, the closed-form internal impulse models are proposed for both a single and dual arms. Based on these models, a new measure for internal impulse is proposed. A normalized impulse ellipsoid reflecting the velocity direction is employed to visualize the impact geometry. Finally, the optimal sawing region is identified in which the amount of external impulse is maximized and the amount of the internal impulse is minimized. It is demonstrated through simulation that the dual arm exhibits better sawing performance over a single arm in aspects of external and internal impulses.

Despite that omni-directional mobile robots have been employed popularly in several application areas, effort on optimal design of such mobile robots has been few in literature. Thus, this paper investigates the optimal design of omni-directional mobile robots. Particularly, optimal design parameters such as one or double offset distance of wheel mechanism and the wheel radius are identifed with respect to isotropic characteristic of mobile robots. In addition, the force transmission characteristics and actuator-sizing problem of mobile robots are investigated Analysis has been performed for three actuation sets. It is shown that the redundantly acruated mobile robot with three active caster wheels represents the best performance among them.

It is well-known that bio-systems do not calculate inverse dynamics for trajectory planning, but they move by proper modulation of the system's impedances. Inspired by bio-systems, a biomimetic trajectory planning method is introduced. This scheme is based on employment of redundant actuation which prevails in bio-systems. We explain that in the generation of the biomimetic trajectory, intelligent structure of bio-systems plays an important role to completely modulate the dynamic behaviour of a system, such as natural frequencies and damping ratios. A five-bar mechanism equipped with two redundant actuators is employed to demonstrate the feasibility of the proposed biomimetic trajectory experimentally.

Springs have been employed in a wide range of mechanical systems. This work deals with the design of multi degree-of-freedom spring mechanism. The adaptable spring is desired for enhancing performances of various mechanical systems employing springs. We demonstrate that such adaptable springs can be realized by adopting anthropomorphic musculoskeletal structures of the human upper-extremity, which possesses highly nonlinear kinematic-coupling among redundant muscles existing in its structures. We propose multi-degree-of-freedom spring mechanisms resembling the musculoskeletal structure of the human upper-extremity, and verify the applicability of these mechanisms through simulation.

A new parallel gripping mechanism is proposed in this work. This device has a parallelogramic platform which can be flexibly folded. Therefore, this mechanism not only can be used to grasp an object having irregular shape or large volume, but also can be utilized as micro-positioning device after grasping the object. Forward position analysis and platform kinematics are investigated to deal with motion tracking and force control. Pneumatic rotator is employed for actuation and a compact sized, 4/3 way proportional pressure valve is also developed to deal with feedback-based dynamic control. The pressure valve also allows indirect force control by measuring the offset pressure occurring due to contact between the grasped object and the parallel platform. In experimental work, performances of the motion tracking and indirect force control are shown satisfactory.

In this work, a parallel-type gripping and micro-positioning mechanism is proposed. This device has a parallelogrammatic platform which can be flexibly folded. Therefore, this mechanism not only can be used to grasp an object having irregular shape or large volume, but also can be utilized as a micro-positioning device after grasping the object. Configuration parameter for configuration control of the proposed gripping mechanism is defined. Grasping force and isotropic characteristic of the mechanism are considered as design indices for optimal design of the gripping mechanism. The proposed mechanism is expected to be used as an adaptable gripping and micro-positioning device by attaching it at the end-point of a robot.