Showing papers on "Articulated robot published in 1995"

Steering mechanism of underwater micro mobile robot

Abstract: This paper deals with a micro mobile robot in water utilizing a PZT(Pb(Zr,Ti)O/sub 3/) as an actuator. A robot driven by a PZT requires a magnification mechanism and the effects of the resonance to enlarge the displacement of the PZT. In this paper, the authors propose a prototype micro mobile robot which has a new steering mechanism. The robot possesses a pair of legs and each leg has a pair of fins with some angle, which is essential to the improvement of the robot performance. A leg generates force both forward and backward according to frequency because the offset angle between a pair of fins works properly. Therefore, the robot can steer efficiently by combination of both modes. The size of the robot is 32 mm in length and 19 mm in width. This robot has many possible applications, such as small pipelines inspection and use in biomedical fields.

Two-armed bipedal robot that can walk, roll over and stand up

Abstract: Focusing attention on flexibility and intelligent reactivity in the real world, it is more important to build, not a robot that won't fall down, but a robot that can get up if it does fall down. This paper presents research on a two-armed bipedal robot, an apelike robot, which can perform biped walking, rolling over and standing up. The robot consists of a head, two arms, and two legs. The control system of the biped robot is designed based on the remote-brained approach in which a robot does not bring its own brain within the body and talks with it by radio links. This remote-brained approach enables a robot to have both a heavy brain with powerful computation and a lightweight body with multiple joints. The robot can keep balance while standing using tracking vision, detect whether it falls down or not by a set of vertical sensors, and perform a getting up motion by coordinating two arms and two legs. The developed system and experimental results are described with illustrated real examples.

Evolving non-Trivial Behaviors on Real Robots: an Autonomous Robot that Picks up Objects

Abstract: Recently, a new approach that involves a form of simulated evolution has been proposed for the building of autonomous robots However, it is still not clear if this approach may be adequate to face real life problems In this paper we will show how control systems that perform a non-trivial sequence of behaviors can be obtained with this methodology by carefully designing the conditions in which the evolutionary process operates In the experiment described in the paper, a mobile robot is trained to locate, recognize, and grasp a target object The controller of the robot has been evolved in simulation and then downloaded and tested on the real robot

A numerical technique for planning motion strategies of a mobile robot in presence of uncertainty

Abstract: This paper addresses the problem of planning the motions of a circular mobile robot moving amidst polygonal obstacles with uncertainty in robot control and sensing. The robot is equipped with sensors which, if properly used, may provide information to overcome the uncertainty accumulated during the motions. The position sensor is based on dead-reckoning, the error then results in a cumulative uncertainty. A proximity sensor may be used to localize the robot with respect to the obstacles of the environment. The robot can also gain information by entering inside landmark areas where the position error is assumed to be bounded. The authors describe a planner which produces robust motion strategies composed of sensor-based motion commands which guarantee that, given an explicit model of the error accumulated by the motion commands, the robot can reach safely its goal with an error lower than a pre-specified value. It is based on a propagation of a numerical potential and on a geometric analysis of the reachability of environmental features. This planner exhibits a set of powerful capabilities: while it allows motion primitives which accumulate uncertainty to be considered, it is able, whenever possible, to navigate without relocalizing the robot when the task does not impose it, and also to make a proper use of the sensors. Several examples run with the planner are presented.

Following a wall by an autonomous mobile robot with a sonar-ring

Abstract: Presents a robust method for an autonomous mobile robot with a sonar-ring to follow walls. The sonar-ring consists of multiple ultrasonic range sensors. The proposed wall-following algorithm makes a robot able to follow a wall in various shapes such as a square wall, a circular wall etc. The autonomous mobile robot "Yamabico" is used for experiments after being equipped with a 12 directional sonar-ring. The on-board controller of the robot decides its motion based on sonar-ring range data every 3 centimeters going forward. The authors carried out many experiments with this autonomous mobile robot, and investigated the validity and the limits of this method.

Parameter identification for industrial robots

Abstract: Models and model parameters form the base of a computer aided planning of robot manipulations. The identification procedure presented determines the independent, dynamic parameters by trajectories of optimal excitation without the need of disassembling the robot. Joint parameters are identified by fixing the arms and performing static and dynamic tests where the actuators represent an excitation source. A comparison of measurement and calculation verifies the results for a PUMA 562 robot.

The Robot Control Strategy in a Domain with Dynamical Obstacles

Abstract: The effectiveness of robot-manipulators is determined to a great extent by the speed of making this or that movement needed for carrying out the task. According to this the problem of optimal robot control is often divided into two subproblems solved separately. In the autonomous regime the trajectory planning is fulfilled for providing the robot movement time close to the minimal.

Nonlinear control of robot manipulators using adaptive fuzzy sliding mode control

Abstract: This paper presents an adaptive robust fuzzy control architecture for robot manipulators. The control objective is to adaptively compensate for the unknown nonlinearity of robot manipulators which is represented as a fuzzy rule-base consisting of a collection of if-then rules. The algorithm embedded in the proposed architecture can automatically update fuzzy rules and, consequently it is guaranteed to be globally stable and to drive the tracking errors to a neighborhood of zero. Focusing on realization, hardware limitations such as traditional long computation time and excessive memory-space usage are also relaxed by incorporating heuristic concepts, which reveals the flexible feature of this architecture. The present work is applied to the control of a five degree-of-freedom (DOF) articulated robot manipulator. Experiment results show that the proposed control architecture features fast convergence.

A mobile robot testbed with manipulator for security guard application

Abstract: A mobile robot with a manipulator was developed for a security guard service application. The application image is that a robot patrols the building autonomously and checks for emergencies like fire, intruder, etc. On detecting an emergency the robot informs a remote operator who deals with the emergency by remotely operating the robot. The developed robot has the following functions to perform such a security service: autonomous navigation, master-slave manipulation system with force feedback, a remotely operated camera vision system with wide and stereoscopic view modes. The experiments conducted with the robot show that the robot can navigate autonomously in simple environments with a maximum speed of 1 m/s. A remote operator can perform door-opening using the master-slave manipulator and stereo viewing vision systems. This paper describes the various subsystems of the robot and some findings of the experiments.

Nonlinear feedback control of a biped walking robot

Abstract: An implementation of a biped robot which is capable of dynamic walking by a simple nonlinear control algorithm is presented. Four DC servo motors actuate the knee and ankle joints of the legs of the robot. The biped is constrained to the sagital plane, and the motion generation is reduced to a problem of controlling the position and velocity of the robot's center of gravity. They are controlled by a nonlinear feedback controller, based on a sample feedback linearization method. Several design issues including mechanical structure, leg actuation, and control system of the robot are discussed. Experimental results demonstrate the effectiveness of the algorithm.

Robot motion planning among moving obstacles

Abstract: This thesis presents a new approach for planning a robot's trajectory that avoids static and moving obstacles and minimizes motion time, subject to robot dynamics and actuator constraints. This approach consists of first computing a coarse trajectory that avoids the obstacles and satisfies an approximation of the actuator constraints. Then this trajectory is used as the initial guess of a dynamic optimization that satisfies obstacle avoidance, robot dynamics and the true actuator limits. The first step of the approach is based on the concept of Velocity Obstacle (VO) that defines, at every instant in time, the set of colliding velocities between the robot and the obstacles. The VO set is computed using the relative velocity between the robot and each obstacle, and is instrumental in determining the set of robot velocities avoiding all obstacles and satisfying approximate system dynamics and actuator limits. Within this set, the best avoidance maneuver is chosen heuristically so that the trajectory resulting from the sequence of maneuvers reaches the goal and minimizes motion time. The second step of the approach consists of refining the trajectory with a dynamic optimization that minimizes motion time, subject to the true robot's dynamics, actuator constraints, and time varying obstacle constraints. The dynamic optimization is based on Pontryagin's Minimum Principle and uses a gradient descent method. These two steps lead to the implementation of a powerful and flexible planner that combines the advantages of heuristics with those of dynamic optimization. Heuristics in fact, captures the non-analytic aspects of motion planning, such as sequence of obstacle avoidance, conservative or aggressive maneuvers, and so on, thus characterizing the global structure of the trajectory. Dynamic optimization on the other hand, ensures feasibility and optimality of the trajectory thus guaranteeing its local correctness. This approach is demonstrated for planning the motions of an automated vehicle in an Intelligent Vehicle Highway System (IVHS) scenario, and of an articulated robot moving in a dynamic environment. This motion planner is suitable to a wide range of applications. The Velocity Obstacle method is very fast and, although approximate, it can be used for real time planning. The Dynamic Optimization is computationally intensive, but yields optimal solutions, which can be used when off-line planning is acceptable.

Design of a high stiffness machining robot arm using double parallel mechanisms

Abstract: Industrial robot has played a central role in the production automation such as welding, assembling, and painting. There has been however, little effort to the application of robots in machining works (grinding, cutting, milling, etc.) which are typical 3D works. The machining automation requires a high stiffness robot arm to reduce deformation and vibration. Conventional articulated robots serially connected links from the base to the gripper. So they have very weak structure for the machining work. Stewart platform is a typical parallel robotic mechanism with a very high stiffness but it has a small work space and a large installation space. This research proposes a new machining robot arm with a double parallel mechanism. It is composed of two platforms and a central axis. The central axis will connect the motions between the fist and the second platforms. Therefore, the robot has a large work space as well as a high stiffness. This paper will introduce the machining automation with a robot and design a machining robot arm using the double parallel mechanism.

A new design of adaptive fuzzy hybrid force/position controller for robot manipulators

Abstract: The major problems of hybrid force/position control arise from uncertainty of the robot manipulators and unknown parameters of the task environment. In this paper, a new design method of the hybrid force/position control of the robot manipulators is proposed to solve these problems. The control objective is to track the desired force and position trajectories simultaneously regardless of the unknown parameters of the task environment and the existence of the manipulator dynamics, represented as a fuzzy rule-base. The algorithm embedded in the proposed architecture can automatically update the fuzzy rules and, consequently, guarantee the global stability and drive the tracking errors to a neighborhood of zero. The present work is applied to the control of a five degree-of-freedom (DOF) articulated robot manipulator. Simulation results show that the proposed control architecture is featured in fast convergence.

A general algorithm for dynamic control of multilink robots

Abstract: One of the major tasks in the development of sophisticated methods for robot control is finding algorithms that are appli cable to a wide range of different robots. Another major task is to find algorithms that can be used for on-line control. Several attempts have been made to solve one or the other of these problems. This article presents a general method for solving both. It can be applied to any redundant or nonredundant robot with rigid subunits connected by revolute joints in a tree-like structure. The number of joints can be chosen arbitrarily large without singularity problems, in contrast to traditional inverse kinematics models. A system based on the presented method needs no modifications when changing from one specifrc robot to another structurally or kinematically completely different robot, only input parameters describing the robot are different. The method is founded on a very general algorithm for finding the Lagrangian equations of motion for a robot subject to a given set of artificial ...

Motion planning of legged robots: the spider robot problem

Abstract: We consider the problem of planning motions of a simple legged robot called the spider robot. The robot is modelled as a point where all its legs are attached, and the footholds where the robot can securely place its feet consist of a set of n points in the plane. We show that the space F of admissible and stable placements of such robots has size Θ(n2) and can be constructed in O(n2 log n) time and O(n2) space. Once F has been constructed, we can efficiently solve several problems related to motion planning.

A generalized formulation for simulation of space robot constrained motion

Abstract: In the past decade, research advances in robot dynamic simulation have included algorithms for space robots operating as open chain mechanisms and earth-bound robot systems operating under constrained motion conditions. Few researchers, however, have investigated a combination of these conditions, i.e. a space robot performing closed chain operations. This paper presents a generalized formulation of the dynamic equations for a space-based robot in both open chain and closed chain configurations. This formulation represents the consolidation of several specialized formulations into a single convenient form.

A new control design methodology for robotic manipulators with flexible joints

Abstract: In this paper, we present a simple controller structure for robotic manipulators which contain flexible joints of arbitrary compliance between the actuating motors and the robot links. The proposed controller structure results in a singularly perturbed system whose boundary layer system is linear, time-invariant and exponentially stable. With the proposed structure, most of the control design effort is based on the reduced order model associated with the singularly perturbed system. This reduced order model has the structure of a rigid robot; hence there are many available design methods for the major portion of the control design. We impose no restrictions on the stiffness of the joints; hence robots with very flexible joints can be successfully treated, Numerical simulation results for a single link manipulator are included.

Robust control of free-floating space robot systems

Abstract: In this paper, we propose a robust control scheme for a free-floating space robot system where a robot arm is mounted on a free-floating base—a satellite, spacecraft or space station. The base is not controlled by external moments or forces. We model the system as an extended robot, including a pseudo-arm representing the base motion produced by six hypothetical passive joints, and a real robot arm. This model allows us to categorize the free-floating space robot system as a specific type of under-actuated system with mixed passive and active joints. We then discuss some fundamental properties of such a system. By means of an input-output linearization technique, we demonstrate that the internal dynamics of the system are nonlinear parametric and therefore, the control of the system using conventional robot control schemes is not feasible. To overcome the difficulty in controlling the internal dynamics subject to parameter uncertainty, and to avoid the measurement of the base acceleration, we develop a ro...

Driving control method for articulated robot

Abstract: PURPOSE:To divide a shock generated at the end of operation of each articulation, reduce residual vibration, and make the robot enter the next operation immediately by generating an operation program so that the operations completion times of respective articulations do not overlap, and driving the respective articulations according to the operation program. CONSTITUTION:A controller 19 has a memory internally and this memory stores the operation program of the articulated robot. The operation times of the respective articulations 12, 14, and 16 are set in the memory of the controller 19, the operation program which is so generated that the operations of the respective articulations 12, 14, and 16 do not end at the same time is stored, and the controller 19 drives servomotors for the articulations 12, 14, and 16 according to the operation program. Consequently, shocks generated when the operations of the articulations 12, 14, and 16 end can be divided to reduce the residual vibration. Consequently, the robot can enter a next operation immediately and the actual operation time of the robot is shortened.

Robot collision preventing method

Abstract: PURPOSE:To provide a robot collision preventing method allowing the collision avoidance of a robot with an obstruction to be carried out by the autonomous action of the robot or even at the time of putting the robot in action by manual operation CONSTITUTION:Plural contactless proximity distance sensors 1-6 are fitted in the center axis direction and in the right-angled direction to the center axis direction of a hand 10 mounted to the tip of an articulated robot When the robot is put in action, the tip shaft of the hand 10 is rotated by the control of a robot controller 30 so that the direction of the proximity distance sensor in the moving direction of the hand 10 is parallel to a path, and the distance between the hand 10 and an obstruction detected by the proximity distance sensor changed in the direction is monitored In the case of getting close to the specified distance or less, the action of the robot is stopped, and an alarm is sounded

Nested Networks for Robot Control

Abstract: Sensor based robot control systems can overcome many of the difficulties which are caused by unknown or uncertain models of the environment. Conventional sensor based control systems require explicit knowledge of the kinematics and dynamics of the robot arm and a careful calibration of the sensor system. In-stead, adaptive neural controllers can be used to build an internal representation of the camera-motor correspondence from exemplar behaviour and adapt where necessary. In that case, static models are not necessary anymore, and the system can cope with changing behaviour of the robot (wear and tear, payload correction) and its sensors (changing lighting conditions, calibration and re-calibration).

Legged robot

Abstract: This paper addresses some of the fundamental problems in getting a legged robot to walk and to navigate autonomously in an unknown environment. To understand the robot walking characteristics, a six legged robot was designed, built and tested in the laboratory. To investigate the navigational capability of the robot, ultrasonic sensors together with a navigational control algorithm were used to detect and avoid obstacles. Results from the experiments performed show that the maximum walking speed of the robot is limited by the period in which stable walk can be achieved. The navigational control algorithm, implemented on the robot, has proven to be intelligent enough to enable the robot to move autonomously through unfamiliar environments.

Small-size articulated robot device

Abstract: PROBLEM TO BE SOLVED: To provide a small-size articulated robot device which is simple in handling and produced at low cost, and which mounted with a small-size articulated robot on a carrier device and has a broad objective area for processing. SOLUTION: A floating arm is supported by a support 1 via a balancer 8 so that the free end of the articulated floating arm 7 is freely raised/lowered and a support bracket 9 is turnably mounted on the free ends of the floating arm horizontally. A small-size articulated robot 11 and a long member 12 having a positioning piece 123, which is engaged with an engagement part of a work positioning jig, in its bottom end are suspendedly provided to the support bracket and at the same time a fixing means 13 for fixing a position of the floating arm is provided in such a state that the positioning piece is engaged with the engagement part of the work positioning jig.

Cleaning equipment of inside of heat exchanger tube

Abstract: PURPOSE:To improve an operating efficiency of an operation for centering the end face of a bundle and a cleaning device by controlling the motion of an articulated robot on the basis of data on position of a heat exchanger tube in relation to reference coordinates and data on disposition of the heat exchanger tube registered beforehand CONSTITUTION:Data to be taught to an articulated robot 4 by teaching are plane coordinates of a tube plate 2 in reference coordinates which the robot has, in other words, two data: a distance from the origin of the reference coordinates of the robot to the plane of the tube plate 2 and arrangement of tubes Teaching is executed with the fore end of a lance support part moved to a position desired to be taught actually The movement is conducted by a remote control by a manual controller which a robot controller 5 has As for the data, on the other hand, it is needed only to teach the position of the tube to be some reference, vertical and horizontal pitches of the tubes, an increase in the number of the tubes between lines, etc

Washing device for track vehicle

Abstract: PURPOSE:To obtain a washing device for a vehicle which can be installed in a region where the space between the contiguous tracks to each other is narrow CONSTITUTION:A shiftable board 3 is placed as a washing device 1 which washes the front and rear surfaces of an orbital vehicle T, in a slidingly shiftable manner for a base member 2 installed in an orbit side part, and a horizontal turnable arm 4 which is turnable around a vertical axis is supported on the shiftable board 3, and an articulated robot 5 is installed at the top end part of the horizontal turnable arm 4 A washing liquid injection nozzle, high pressure water injection nozzle, and a distance sensor 14 for detecting the distance between each nozzle and the vehicle T are installed at the arm top end part of the articulated robot 5 After the front surface of the vehicle is washed by the drive of the shiftable board 3, horizontal turnable arm 4, and the articulated robot 5, the washing device 1 is set at a retreat position, and the vehicle T is travelled, and then, the rear surface of the vehicle is washed by the drive of the shiftable board 3, horizontal turnable arm 4, and the articulated robot 5

Robot Manipulator Control Using Neural Networks

Abstract: The control of a multi-input-multi-output (MIMO) plant is a difficult problem when the plant is nonlinear and time-varying and there are dynamic interactions between the plant variables. A good example of such a plant is an articulated robot with two or more joints handling a changeable load.

Nonlinear feedback control of flexible robot arms

Abstract: Modeling and control of robot arms with non-negligible elastical deformations have invited researches in the recent years, due to the demands on robot arms which are of lighter weight, move faster and consume less energy. In this paper, the authors present a nonlinear, distributed-parameter dynamic model for a two-link robot arm, derived using Hamilton’s principle. The dynamic model is then transformed into state-space expression, which gives an infinite-dimensional dynamic system. Position of the tip of the robot arm is chosen as the output of the dynamic system. A nonlinear feedback law is proposed to achieve input-output linearization and decoupling, which is an extension of input-output linearization and decoupling of finite-dimensional dynamic systems.

Arm action restricting mechanism for horizontal articulated robot

Abstract: PURPOSE:To provide an arm action restricting mechanism for a horizontal articulated robot of high reliability at a low cost wherein action ranges of the first/second arms can be collectively restricted by a simple constitution. CONSTITUTION:A wire 18, extended from a supporter 11 to a prescribed part in a side surface of the second arm 15 through side surfaces of the first rotary shaft 12, first arm 13 and the second rotary shaft 14, is provided, to also provide the first/second guide members 19, 20 for guiding the wire 18 so that it can be slid on the side surfaces of the first/second arms 13, 15, and a condition of fully extending the wire 18 is set to a position of restricting action of the first/second arms 13, 15.