Time-delay command shaping filters for re-ducing the vibrational response of flexible systems are introduced and discussed. Special attention is given to the role played by robustness and adaptation in producing effective filters even when system parameters change. Results from several authors are used to compare and contrast these approaches.
In this paper, we prove that a 4-D.O.F planar manipulator which consists of two actuated joints and two unactuated joints is completely controllable, namely, there exists an input to drive the system from any given initial state to any state in finite time. The proof exploits the mechanical properties of the planar systems.
This paper describes a novel action selection method for multiple mobile robots boxpushing in a dynamic environment. The robots are designed to need no explicit communication, and be adaptive to a dynamic environments by changing modules of behaviors. Though it is a significant problem to deal with adaptive action selection for multiple mobile-robots in a dynamic environment, few studies have been done. Decentralized control of robots without explicit communication is also practical and important for robustness. Thus we propose adaptive action selection without explicit communication for multi-robot box-pushing, which changes an available behavior set depending on a situation. First four situations are defined with two parameters: existence of other robots and task difficulty. Next we design a set of behaviors for each situations, and mobile robots are programmed to act with behaviorbased approach. We fully implement our method on four real mobile robots, and make experiments in dynamic environments.
We describe in this paper a ground based hardware simulation system for emulating a space robot under microgravity condition. The manipulator of the robot is suspended by wires which are kept in vertical direction by suspension arms that follow the motion of the manipulator in real-time.The base of the robot is supported by a six-DOF (degree-of-freedom) mechanism. Free floating emulation is achieved by using a real-time numerical integration of the dynamic and kinematic equations of the manipulator. The gravitational force on the manipulator is compensated by a combination of the force on the base as applied by the six-DOF mechanism and the upward tensile force which is exerted through the wires. By optimizing the manipulator suspension method, the individual wire tensions are kept constant, independent of the manipulator attitude. Experiments show that the Micro-G emulation system is precise enough to emulate three-dimensional motion of a space robot, in a microgravity environment under condition of only 0.28 × 10-2 [G] .
A wheeled mobile robot with trailers has been studied as a class of nonholonomic systems. It is proved that a tractor and all trailers can be stabilized to desired positions via nonholonomic motion control. On the other hand, trailers have been developed and widely used in the industry. The main focus of such designs is on reducing tracking error from reference trajectory. In this paper, we try to bridge between these two approaches. We develop a design theory of trailer systems with passive steering. These systems possess a good performance in practical path following, and accept proved and established various control strategies for nonholonomic systems.
This paper describes the use of the newly developed system named“Intelligent Data Carrier System: IDC System”to execute several tasks by a multirobot system in a so-called“emergent”manner. In order to realize the function emergence in real systems, it is important to consider how to design and embed the system into a real form, rather than theoretical or numerical researches on an emergent behavior itself. Based on the discussion on the design frameworks of an“emergent system”, we try to implement the IDC system along with an actual multirobot system which consists of omnidirectional mobile robots equipped with folk lifts for handling of the IDC units. The applicability of the IDC system is demonstrated through the experiments for two kinds of tasks; 1) object transportation, and 2) patrolling. It can be concluded that the IDC system is effectively used in the tasks appearing in the practical missions of multirobot systems which can be regarded as one of the physical (real) systems that could realize“function emergence”.
In this paper, we describe development of a mobile robot which does unsupervised learning for recognizing environments from action sequences. Most studies on recognizing an environment have tried to build precise geometric maps with high sensitive and global sensors. However such precise and global information may not be obtained in real environments. Furthermore unsupervised-learning is necessary for recognition in unknown environments without help of a teacher. Thus we attempt to build a mobile robot which does unsupervised learning to recognize environments with low sensitive and local sensors. The mobile robot is behavior based and does wall following in enclosures. Then the sequences of actions executed in each enclosure are transformed into input vectors for a selforganizing map. Learning without a teacher is done, and the robot becomes able to identify enclosures. Moreover we developed a method to identify environments independent of a start point using a partial sequence. We have fully implemented the system with a real mobile robot, and made experiments for evaluating the ability. As a result, we found out that the environment recognition was done well and our method was adaptive to noisy environments.
This paper reports the implementation of an intelligent motion for autonomous mobile manipulator. We determined our research task as“Autonomous Navigation including Door Open Motion”, in indoor environment. This task is one of basic skills for mobile manipulator, however the cooperation of several theories and techniques is necessary for this research task. To realize the task, we developed both hardware and software of one robot system, executed in real environment, and feedbacked the experimental results to both hardware design and motion algorithm. In this paper, we describe a detail design of the mobile robot motion (which is divided into several stages), hardware and software to realize the research task. Also, we report experimental results, and discuss about knowledge and problems for controlling autonomous mobile manipulator.
To manipulate an object by a multifingered hand stably, frictions at the contact point should be large enough. Although a soft-finger type contact provides high friction contacts, its frictional moment around the contact normal makes the manipulation control difficult. In this paper, we propose a control scheme to manipulate an object by a multifingered hand with soft fingertips. The proposed scheme cancels the frictional moment around the contact normal according to the direction of the relative rotation between the fingertip and the object. A necessary and sufficient condition of the frictional moment compensation is derived. Simulation results show the effectiveness of the proposed control scheme.
This paper is concerned with avoidance manipulability of redundant manipulators for trajectory tracking and obstacle avoidance. Possibility of avoiding a collision with obstacles during tracking a desired hand trajectory is discussed with proposed avoidance matrix, avoidance manipulability ellipsoid and avoidance manipulability measure which are defined on each link constructing the manipulator except top link. A necessary and sufficient condition that the intermediate links can avoid obstacles in a work space is indicated that a dimension of range space of the avoidance matrix coincides with the one of the work space of the manipulator. That means the avoidance manipulability ellipsoid is expanded in the whole work space. Relations of the ellipsoids and factors which influence the shape, namely, a posture of the manipulator, redundant degree, a serial position of the intermediate link from base, and priorities of the avoiding tasks, are also analyzed. Finally we show analyzed results of avoidance possibility with the proposed avoidance manipulability by numerical examples.
A mobile robot is one of the most suitable tools for the research of the artificial intelligence. Though an actual mobile robot and simulator are often used, each of them has merits and demerits in the research of the mobile robot. In this paper, we propose Multilevel Environment for Mobile Robotics Capability Experiments (MEMORABLE) which is a research environment that is consisted of a mobile robot simulator, a real world sensor database and actual mobile robot. These elemental facilities are connected through the internet, and a user can freely combine and use it depending on his/her research aim. We applied the MEMORABLE to a navigation learning task of the mobile robot. The experimental results show that the robot learned robuster behavior on actual robot by the batabase than by the simulator.
Skid wheels have good effects on locating a vehicle at an appropriate position in pipe since they operate to make the vehicle move freely toward swelling direction under the pressing force against the pipe wall. Several types of skid wheels are classified in their mechanisms and evaluated in their motional characteristics by using the simulator which provides us a locomotional environment without using the pipe. First type is a wheel having free rollers partially on its rim. Second is a wheel having pendulums capable of rotating around the rim in limited ranges. Third is a wheel replacing the roller with a linear slider, which consists of a wheel base, sliding pieces, spring, side plates of a circular form, and clamp screws. Fourth is a segmented ring-type wheel which seems to be good for climbing a step. The last is a sandwich-type wheel proposed in this paper. In the measurement of the motional characteristics of each wheel, an appropriate set for mocking the wheel on the pipe wall is introduced. Counter balances for assigning the load of the vehicle to the wheel are discussed in the kinematical analysis. Utilizing the set, sideways motions of the wheels are monitored. As a result, the sandwich type wheel is shown to be the best for producing the skid function.