Showing papers on "Articulated robot published in 2016"

Coordination of Multiple Robotic Fish With Applications to Underwater Robot Competition

Abstract: This paper is concerned with the coordination control of multiple biomimetic robotic fish in highly dynamic aquatic environments by building a hybrid centralized system. With the aid of the results of biorobotics and control techniques, a radio-controlled multijoint robotic fish and its locomotion control are developed. To enable a closed control loop, a visual subsystem that is responsible for tracking of multiple moving objects is constructed and implemented in real time. Furthermore, a behavior-based hierarchical architecture in conjunction with fuzzy reinforcement learning is proposed to accomplish effective coordination among multiple swimming robots. Finally, experiments on 2vs2 water polo game are carried out to verify the proposed coordination control scheme. Over the past eight years, this multirobot platform has been successfully applied to international underwater robot competitions to promote innovative research and education in underwater robotics.

Pipe Network Locomotion with a Snake Robot

Abstract: We present a method of achieving whole-body compliant motions with a snake robot that allows the robot to automatically adapt to the shape of its environment. This feature is important to pipe navigation because it allows the robot to adapt to changes in diameter and junctions, even though the robot lacks mechanical compliance or tactile sensing. Rather than reasoning in the configuration space of robot joint angles, the compliant controller estimates the overall state of the robot in terms of the parameters of a low-dimensional control function, i.e., a gait. The controller then commands new gait parameters relative to that estimated state. Performing closed-loop control in this lower-dimensional parameter space, rather than the robot's full configuration space, exploits the intuitive connection between the gait parameters and higher-level robot behavior. Furthermore, the ability to automatically adjust gait parameters with this controller enables more sophisticated motions that would previously have been too complex to be controlled manually.

Simultaneous position and stiffness control for an inflatable soft robot

Abstract: Soft robot research has led to the development of platforms that should allow for better performance when working in uncertain or dynamic environments. The potential improvement in performance of these platforms ranges from mechanical robustness to high forces, to applying lower incidental contact forces in uncertain situations. However, the promise of these platforms is limited by the difficulty of controlling them. In this paper, we present preliminary results on simultaneously controlling stiffness and position for a pneumatically actuated soft robot. Improving on our prior work, we show that by including the pressure in our soft robot actuation chambers as state variables we can improve our average rise time by up to 137%, settling time by 119%, and overshoot by 853%. In addition to these improvements, we can now control both joint position and stiffness simultaneously. This performance improvement comes from using Model Predictive Control running at 300 Hz with improved dynamic models of the soft robot. High performance control of soft robot joints, such as the joint presented in this paper, will enable a wide range of robot applications that were previously difficult or impossible due to the rigid nature of traditional robot linkages and actuation schemes.

Tendon-driven continuum robot for neuroendoscopy: validation of extended kinematic mapping for hysteresis operation

Abstract: Purpose The hysteresis operation is an outstanding issue in tendon-driven actuation—which is used in robot-assisted surgery—as it is incompatible with kinematic mapping for control and trajectory planning. Here, a new tendon-driven continuum robot, designed to fit existing neuroendoscopes, is presented with kinematic mapping for hysteresis operation.

Finite-time sliding surface constrained control for a robot manipulator with an unknown deadzone and disturbance.

Abstract: This paper presents finite-time sliding mode control (FSMC) with predefined constraints for the tracking error and sliding surface in order to obtain robust positioning of a robot manipulator with input nonlinearity due to an unknown deadzone and external disturbance. An assumed model feedforward FSMC was designed to avoid tedious identification procedures for the manipulator parameters and to obtain a fast response time. Two constraint switching control functions based on the tracking error and finite-time sliding surface were added to the FSMC to guarantee the predefined tracking performance despite the presence of an unknown deadzone and disturbance. The tracking error due to the deadzone and disturbance can be suppressed within the predefined error boundary simply by tuning the gain value of the constraint switching function and without the addition of an extra compensator. Therefore, the designed constraint controller has a simpler structure than conventional transformed error constraint methods and the sliding surface constraint scheme can also indirectly guarantee the tracking error constraint while being more stable than the tracking error constraint control. A simulation and experiment were performed on an articulated robot manipulator to validate the proposed control schemes.

Pheeno, A Versatile Swarm Robotic Research and Education Platform

Abstract: Swarms of low-cost autonomous robots can potentially be used to collectively perform tasks over very large domains and time scales. Novel robots for swarm applications are currently being developed as a result of recent advances in sensing, actuation, processing, power, and manufacturing. These platforms can be used by researchers to conduct experiments with robot collectives and by educators to include robotic hardware in their curricula. However, existing low-cost robots are specialized and can lack desired sensing, navigation, control, and manipulation capabilities. This letter presents a new mobile robot platform, Pheeno, that is affordable, versatile, and suitable for multirobot research, education, and outreach activities. Users can modify Pheeno for their applications by designing custom modules that attach to its core module. We describe the design of the Pheeno core and a three degree-of-freedom gripper module, which enables unprecedented manipulation capabilities for a robot of Pheeno's size and cost. We experimentally demonstrate Pheeno's ability to fuse measurements from its onboard odometry for global position estimation and use its camera for object identification in real time. We also show that groups of two and three Pheenos can act on commands from a central controller and consistently transport a payload in a desired direction.

Laban head-motions convey robot state: A call for robot body language

Abstract: Functional robots are an increasing presence in shared human-machine environments. Humans efficiently parse motion expressions, gaining an immediate impression of an agent's current action and state. Past work has shown that motion can effectively reveal a robot's current task objective to bystanders and collaborators, however, the layering of expression on pre-existing robot task motions has yet to be explored. Rather than showing us what the robot is doing, these layered motion characteristics leverage the how of the task motions to convey additional robot attitudes, e.g., confidence, adherence to deadline or flexibility of attention. To lay the foundations for this objective, we adapt the Laban Efforts, a system from dance and acting training in use for over 50 years. We operationalize features representing the four Laban Efforts (Time, Space, Weight, and Flow) to the movements of a 2-DOF Nao head and a 4-DOF Keepon robot during simple dance and look-for-someone behaviors. Using online survey, we collect 1028 motion ratings for 72 robot motion videos depicting contrasting Effort motion examples. We achieve statistically significant legibility results for all four Effort implementations. Even without human degrees of freedom, we find that robot motion patterns can convey complex expressions to people.

Articulated Robot Motion for Simultaneous Localization and Mapping (ARM-SLAM)

Abstract: A robot with a hand-mounted depth sensor scans a scene. When the robot's joint angles are not known with certainty, how can it best reconstruct the scene? In this work, we simultaneously estimate the joint angles of the robot and reconstruct a dense volumetric model of the scene. In this way, we perform simultaneous localization and mapping in the configuration space of the robot, rather than in the pose space of the camera. We show using simulations and robot experiments that our approach greatly reduces both 3D reconstruction error and joint angle error over simply using the forward kinematics. Unlike other approaches, ours directly reasons about robot joint angles, and can use these to constrain the pose of the sensor. Because of this, it is more robust to missing or ambiguous depth data than approaches that are unconstrained by the robot's kinematics.

Distributed-Torque-Based Independent Joint Tracking Control of a Redundantly Actuated Parallel Robot With Two Higher Kinematic Pairs

Abstract: A redundantly actuated parallel robot of the 6RSS mechanism involving two point-contact higher kinematic pairs (HKPs) has been developed for the evaluation of food texture changes during the process of mastication. To accomplish this, a fundamental capability of reproducing complex mandibular motions of human subjects in a biomimetic manner is required. In this paper, first, the mechanism and experimental setup of the robot are described, followed by five performance criteria proposed for the torque distribution across the robot. Second, the distributed torque is employed as a feedforward to enhance the independent joint control for the tracking of the mandibular movement. The frictional effects are compensated for to further improve the tracking accuracy. Finally, experiments are carried out to evaluate and compare the proposed control algorithms with the robot being commanded to reproduce a real human mandibular motion in free chewing, chewing a silicone gel, and chewing a wooden stick. The results illustrate that the robot is able to emulate complex mandibular motions, the distributed-torque-based joint control significantly enhances the motion tracking accuracy, and the friction compensation can further improve the motion tracking performance.

Robot system and method of operating a robot system

Abstract: A robot system for carrying out a plurality of operations during assembly or maintenance of an aircraft or spacecraft includes a first robot having a base portion, a movable robot arm having a first coupling portion, and a first control means for controlling the robot arm, a plurality of second robots having movement means, a drive portion operable to drive the movement means, a tool portion having a tool for carrying out a specific one of the operations, a second coupling portion adapted to be selectively and releasably coupled with the first coupling portion in a predetermined positional relationship, and a second control means for controlling the respective second robot. The first and second control means are adapted to control the drive portion of one of the second robots and the robot arm to couple the first coupling portion and the respective second coupling portion in the predetermined positional relationship.

Modular robot assembly kit, swarm of modularized robots and method of fulfilling tasks by a swarm of modularized robots

Abstract: The present invention pertains to a modularized robot having a robot platform configured to convey mobility and connectivity to external components to the modularized robot, a robot workhead configured to convey the ability to perform an operational task to the modularized robot, and a robot adapter attached to either the robot platform or the robot workhead and configured to mechanically link the robot platform to the robot workhead Moreover, a swarm of modularized robots and a robot system include such modularized robots

Human-Guided Robotic Comanipulation: Two Illustrative Scenarios

Abstract: Emerging applications of robot systems that involve physical interaction with humans have opened up new challenges in robot control. While various control techniques have been developed for human-robot interaction, existing methods do not take advantages of both human knowledge and the robot’s ability. In this paper, a human-guided manipulation problem is formulated and solved. The workspace is divided into a human region, where the human plays a more active role in the manipulation task, and a robot region, where the robot is more dominant in the manipulation. The proposed formulation allows the human to take control actions to deal with unforeseen changes or uncertainty in the environment, and also allows the robot to take the lead where the environment is exactly known. We mainly consider two basic scenarios, i.e., robot control first and human control later (R-H) or human control first and robot control later (H-R), to illustrate the concept of human-guided comanipulation. Based on a smooth transition between the human region and the robot region, an adaptive tracking controller is developed to take advantages of both human knowledge and the robot’s ability. The experimental results are presented to illustrate the performance of the proposed control method.

Shape-based compliant control with variable coordination centralization on a snake robot

Abstract: For highly articulated robots, there is a tradeoff between the capability to navigate complex unstructured environments and the high computational cost of coordinating many degrees-of-freedom. In this work, an approach that we refer to as shape-based control helps to balance this trade-off using shape functions, geometric abstractions that determine the coupling between multiple degrees-of-freedom during locomotion. This approach provides a way to intuitively adapt the shape of highly articulated robots using joint-level torque feedback control, allowing a robot to compliantly feel its way through unstructured terrain. In this work we specifically focus on compliance in the spatial frequency and temporal phase parameters of a snake-like robot's wave-like periodic wave-like kinematics. We show how varying the spatial frequency within the shape-based control architecture allows a single controller to vary the degree to which different degrees-of-freedom are coupled throughout a mechanism's body, i.e., the controller's degree of centralization. We experimentally find that for a snake-like robot locomoting through an irregularly spaced peg array, shape-based control results in more effective locomotion when compared to a central pattern generator-based approach.

Robot control apparatus, robot, and robot system

Abstract: A robot control apparatus that controls a robot including a manipulator, a force detector provided in the manipulator, and an actuator that drives the manipulator based on a target position, includes a display control unit that displays a motion position of the manipulator derived based on a target force and an output of the force detector and the target position on a screen.

A novel head gesture based interface for hands-free control of a robot

Abstract: Within this work a novel head gesture based interface for hands-free control of a collaborative robot is developed and evaluated. Based on previous work, robot control is divided into several control groups for intuitive head motion based control. The switching commands to select and switch between these robot control groups are given by four gestures performed with head movements. The head movements were measured using a nine-axis inertial measurement unit. The control of a robot with the novel interface was evaluated objectively as well as subjectively. The objective evaluation contains the measurement of time needed for the given control task and the number of trials for switching between the different groups of robot control. The subjective evaluation was carried out with a questionnaire. All subjects were able to perform the given task of controlling a robot arm with the head gesture based interface.

Multibody modelling of N DOF robot arm assigned to milling manufacturing. Dynamic analysis and position errors evaluation

Abstract: Nowadays, with the large use of robot manipulators in the most different fields of industrial production, two main aims must be commonly reached: robot dynamic behavior improvement and end-effector position errors reduction. For a N DOF robot arm, in case of specific applications such as milling manufacturing, one of the main source of end-effector position errors can be identified with joint compliances. This aspect, well known in literature, has been confirmed by experimental tests and measurements carried out on a specific robot assigned to non-standard milling manufacturing of marble objects (sculptures realization). To approach and analyze this issue the authors chose the multibody simulation environment. Hence, the authors developed a parametric modelling procedure that, by determining the robot characteristics through CAD model and technical data sheet investigation, provides reliable multibody dynamic models of generic N DOF robot arms. In this modelling approach the robot geometry construction is based on a standard strategy typical of this research field (i.e. Denavit-Hartenberg, Veitschegger-Wu). The developed procedure enables to obtain robot representation at various complexity levels according to the number of modelled robot components and actuation typology (Motion laws defined both in displacement or applied torque). Eventually, for a specific test case, the authors were able to correctly simulate the robot dynamic behavior, as it was demonstrated by numerical/experimental comparison. In this way the influence of the joint compliance behavior and actuator rotational inertia effects on end-effector position accuracy was analyzed.

Acquiring and Generalizing the Embodiment Mapping From Human Observations to Robot Skills

Abstract: Robot imitation based on observations of the human movement is a challenging problem as the structure of the human demonstrator and the robot learner are usually different. A movement that can be demonstrated well by a human may not be kinematically feasible for robot reproduction. A common approach to solve this kinematic mapping is to retarget predefined corresponding parts of the human and the robot kinematic structure. When such a correspondence is not available, manual scaling of the movement amplitude and the positioning of the demonstration in relation to the reference frame of the robot may be required. This letter's contribution is a method that eliminates both the need of human-robot structural associations-and therefore is less sensitive to the type of robot kinematics-and searches for the optimal location and adaptation of the human demonstration, such that the robot can accurately execute the optimized solution. The method defines a cost that quantifies the quality of the kinematic mapping and decreases it in conjunction with task-specific costs such as via-points and obstacles. We demonstrate the method experimentally where a real golf swing recorded via marker tracking is generalized to different speeds on the embodiment of a 7 degree-of-freedom (DoF) arm. In simulation, we compare solutions of robots with different kinematic structures.

Singularity Analysis of a Snake Robot and an Articulated Mobile Robot With Unconstrained Links

Abstract: In this paper, we analyze the conditions related to singular configurations with unconstrained links and present related theorems and lemmas for a snake robot and an articulated mobile robot. A snake robot and an articulated mobile robot have links that have passive or active wheels and the links are serially connected by active joints. The singular configuration should be avoided if the robots are automatically controlled because they cannot execute intended motion when they are in the singular configuration. We derive a novel necessary and sufficient condition for the singular configurations of the snake robot; this removes some limitations of the traditional condition for a snake robot without unconstrained links. We also derive the necessary and sufficient conditions for the singular configurations of the articulated mobile robot, and the structural conditions under which a real articulated mobile robot does not have a singular configuration. These conditions are proved by analyzing the elements of matrices included in the kinematic model and considering the geometrical meaning of the elements. In addition, we propose evaluation indices representing the distance from the singular configurations of a snake robot. We verify the effectiveness of these indices through simulations.

A hybrid flying and walking robot for steel bridge inspection

Abstract: Inspection and maintenance are extremely important to maintain safety and long-term usability of bridges. This application requires a robot that is able to maneuver in a complex 3D environment and to stabilize on steel surfaces to perform bolts checking. We propose a novel design and concept of hybrid (integrated walkability and flyability) robot for steel bridge inspection and maintenance. Our proposed design allow the robot to access a 3D structure without being time consuming. In order to stabilize our robot in 3D space, we present a vibration control based on a vibrator to compensate vibration generated from joint actuators when the robot is flying. We present a preliminary experiment on how our robot performs obstacle avoidance along with a simulation of flying performance of a hybrid robot when the vibration was compensated based on LQG control.

Quantitative measures of a robot's physical ability to balance

Abstract: This paper presents quantitative measures of a robot's physical ability to balance itself actively on a single point, line or area of support. These measures express the ratio of a change in the state of motion of the robot's center of mass to the amount of action required at the actuated joints in order to produce that change. They therefore represent measures of the gain of the robot mechanism as seen from the point of view of the balance control system. This paper is concerned mainly with ratios of velocities, called velocity gains, and it builds on earlier work by showing how these ratios can be defined and calculated for the case of a general planar or spatial robot balancing on a point, line or general rolling contact, or an area contact with a compliant surface. The paper concludes with three examples of use-design of a triple pendulum, analysis of a hydraulic quadruped, and expressing the physics of planar balancing-followed by a short discussion of gyroscopic balancing.

Design of a transverse flux machine as joint drive for an articulated six-axis robot arm

Abstract: This paper presents requirements on a articulated robot arm in service robotics and the derivation of requirements on a single joint of this arm. A modular concept with joint modules, each one realizing one axis of the robot arm connected by intermediate elements is proposed. Furthermore, the integration of a permanent magnet excited transverse flux machine as joint drive in this application is discussed. Transverse flux machines typically offer a high torque density at low speed. As torque demand increases from wrist to shoulder joint and speed demand decreases at the same time, this paper concentrates on the design of a shoulder joint module, where the integration of a transverse flux machine seems to be most promising. A design of a transverse flux machine as drive of an exemplary shoulder joint is proposed and results from a three dimensional finite element simulation are presented.

Self-Balancing Robot System Comprising Robotic Omniwheel

Abstract: A self-balancing robot system comprising artificial intelligence characterized in that the robot is comprising a humanoid body or comprising a vehicle body. The humanoid body is used for service comprises; an articulated head comprising a voice system for user interaction, and a logic controller for facial imaging via a LED system and LED display monitor. The robot body comprising; a neck, two electromechanical arms with actuating hands used to achieve gripping objects; a pivoting trunk containing a computer operating system, the electrical control system including a batter bank and a battery charger; the lower portion of the body utilizing uni-robotic omniwheel or utilizing legs coupled to the robotic omniwheels or coupled to omnidirectional track wheels which work like skates. The robot system also comprises a computer operating system, a motion control system, an autonomous drive system, a wireless communication system working in combination with an attitude sensing system using state sensors, actuators and accelerometers to control pitch and balance thus allowing the service robot and service vehicle to work indoors and travel on common roadways and on smart highways.

Method, control system and movement setting means for controlling the movements of articulated arms of an industrial robot

Abstract: The invention relates to a method for controlling the movements of articulated arms ( 21, 22, 23 ) of an industrial robot ( 2 ) using a movement setting means ( 3 ) to be guided by hand by an operator, the movements of which are provided for generating at least a portion of the movement control data for the industrial robot ( 2 ) to be controlled. At least one of a plurality of reference marks ( 19, 19′, 19 ″) is arranged or formed at least on individual articulated arms ( 21, 22, 23 ) adjustable by the operator. The movement setting means ( 3 ) comprises at least one imaging and/or at least one distance-sensitive sensor (16, 17) which at least one sensor ( 16, 17 ) can be set with at least one of the plurality of reference marks ( 19, 19′, 19 ″) into a relative spatial position selected by the operator. During a movement of the movement setting means ( 3 ) at least the articulated arm ( 21, 22, 23 ) bearing the respectively selected reference mark ( 19, 19′, 19 ″) follows the movements of the movement setting means by control technology. In addition, a corresponding control system ( 1 ) and movement setting means ( 3 ) are specified.

Design and control of a tracked robot for search and rescue in nuclear power plant

Abstract: Environment in some special areas of nuclear power plant is very bad, and is even worse and inaccessible after a nuclear accident. Therefore, a robot developed for special occasions of nuclear plant operation is urgently needed. Different from ordinary robots, nuclear industry robots face even worse environments, such as high radiation, high temperature, high pressure, narrow space, slopes, stairs, and complicated pipeline. This paper designs a tracked mobile robot for search and rescue in nuclear plant. Stair climbing performance of the robot is analyzed. Hardware and software of the control system are designed, and the human-computer interaction interface is developed. Dynamic model of the robot is established, and the trajectory tracking control algorithm of the robot is presented. Finally, simulation experiments using Octave software are finished. Simulation results show that the proposed control algorithm could enable the tracked robot to achieve excellent trajectory tracking of linear and cambered path, and the effectiveness of the proposed method is verified.

On modeling and position tracking control of the generalized differential driven wheeled mobile robot

Abstract: This paper presents two models for the generalized differential wheeled mobile robot where the origin of the frame of reference of the robot may be placed away from the center of the prolongation of the axes of the actuated wheels of the robot. One model relates the angular speeds of the actuated wheels with the posture of the robot. A position tracking control is exemplified via numerical simulations using this model.