Showing papers on "Articulated robot published in 2017"

Deep reinforcement learning for high precision assembly tasks

Abstract: The high precision assembly of mechanical parts requires precision that exceeds that of robots. Conventional part-mating methods used in the current manufacturing require numerous parameters to be tediously tuned before deployment. We show how a robot can successfully perform a peg-in-hole task with a tight clearance through training a recurrent neural network with reinforcement learning. In addition to reducing manual effort, the proposed method also shows a better fitting performance with a tighter clearance and robustness against positional and angular errors for the peg-in-hole task. The neural network learns to take the optimal action by observing the sensors of a robot to estimate the system state. The advantages of our proposed method are validated experimentally on a 7-axis articulated robot arm.

Design of the Hydraulically Actuated, Torque-Controlled Quadruped Robot HyQ2Max

Abstract: This paper presents the design of the hydraulically actuated quadruped robot HyQ2Max . HyQ2Max is an evolution of the 80 kg agile and versatile robot HyQ. Compared to HyQ, the new robot needs to be more rugged, more powerful and extend the existing locomotion skills with self-righting capability. Since the robot's actuation system has an impact on many aspects of the overall design/specifications of the robot (e.g., payload, speed, torque, overall mass, and compactness), this paper will pay special attention to the selection and sizing of the joint actuators. To obtain meaningful joint requirements for the new machine, we simulated seven characteristic motions that cover a wide range of required behaviors of an agile rough terrain robot, including trotting on rough terrain, stair climbing, push recovery, self-righting, etc. We will describe how to use the obtained joint requirements for the selection of the hydraulic actuator types, four-bar linkage parameters, and valve size. Poorly sized actuators may lead to limited robot capabilities or higher cost, weight, energy consumption, and cooling requirements. The main contributions of this paper are: 1) a novel design of an agile quadruped robot capable of performing trotting/crawling over flat/uneven terrain, balancing, and self-righting; 2) a detailed method to find suitable hydraulic cylinder/valve properties and linkage parameters with a specific focus on optimizing the actuator areas; and 3) to the best knowledge of the authors, the most complete review of hydraulic quadruped robots.

Deep Reinforcement Learning for High Precision Assembly Tasks

Abstract: High precision assembly of mechanical parts requires accuracy exceeding the robot precision. Conventional part mating methods used in the current manufacturing requires tedious tuning of numerous parameters before deployment. We show how the robot can successfully perform a tight clearance peg-in-hole task through training a recurrent neural network with reinforcement learning. In addition to saving the manual effort, the proposed technique also shows robustness against position and angle errors for the peg-in-hole task. The neural network learns to take the optimal action by observing the robot sensors to estimate the system state. The advantages of our proposed method is validated experimentally on a 7-axis articulated robot arm.

A Human–Robot Co-Manipulation Approach Based on Human Sensorimotor Information

Abstract: This paper aims to improve the interaction and coordination between the human and the robot in cooperative execution of complex, powerful, and dynamic tasks. We propose a novel approach that integrates online information about the human motor function and manipulability properties into the hybrid controller of the assistive robot. Through this human-in-the-loop framework, the robot can adapt to the human motor behavior and provide the appropriate assistive response in different phases of the cooperative task. We experimentally evaluate the proposed approach in two human–robot co-manipulation tasks that require specific complementary behavior from the two agents. Results suggest that the proposed technique, which relies on a minimum degree of task-level pre-programming, can achieve an enhanced physical human–robot interaction performance and deliver appropriate level of assistance to the human operator.

TOMM: Tactile omnidirectional mobile manipulator

Abstract: In this paper, we present the mechatronic design of our Tactile Omnidirectional Robot Manipulator (TOMM), which is a dual arm wheeled humanoid robot with 6DoF on each arm, 4 omnidirectional wheels and 2 switchable end-effectors (1 DoF grippers and 12 DoF Hands). The main feature of TOMM is its arms and hands which are covered with robot skin. We exploit the multi-modal tactile information of our robot skin to provide a rich tactile interaction system for robots. In particular, for the robot TOMM, we provide a general control framework, capable of modifying the dynamic behavior of the entire robot, e.g., producing compliance in a non-compliant system. We present the hardware, software and middleware components of the robot and provide a compendium of the base technologies deployed in it. Furthermore, we show some applications and results that we have obtained using this robot.

Robot-assisted 3D printing of biopolymer thin shells

Abstract: The design, development, and testing of a robot-assisted biopolymer thin shell free-form printing system is presented. This fused-deposition style printing system directly extrudes pellets of biomaterial and is capable of printing directly on organically shaped 3D curved surfaces. The screw extrusion method allows direct printing from pellets. The printed structure is supported by a pre-built base (a mandrel), which is manipulated by a six degree-of-freedom industrial robot arm, an ABB IRB120. This robot is used to manipulate the orientation of the support mandrel surface. The print method works by projecting a desired 2D image onto a mathematical model of the pre-built mandrel surface. This produces a 3D point path for the system to follow. These points are then converted into vectors for the robot’s pose and orientation of the end effector, which ensures that the extrusion remains normal to the mandrel surface. Inverse kinematics is applied to convert the trajectory into joint positions for the robot to follow. This paper demonstrates the utility of the developed system through simulation and printing of concave surface designs.

Shared Control Design of a Walking-Assistant Robot

Abstract: This brief presents a control design for a walking-assistant robot in a complex indoor environment, such that it can assist a walking-impaired person to walk and avoid unexpected obstacles. In this design, the robot motion is a resultant of autonomous navigation and compliant motion control. The compliance motion controller allows the robot to possess passive behavior following the motion intent of the user, while the autonomous guidance gives safe navigation of the robot without colliding with any obstacles. A shared-control approach is suggested to combine the passive compliant behavior and safe guidance of the robot. When a user exerts force to the robot, the mobile platform responds to adjust the speed in compliance with the user movement. On the other hand, the autonomous navigation controller is designed to provide collision-free guidance. Using the developed shared controller, outputs of the compliance motion controller and autonomous navigation controller are fused to generate appropriate motion for the robot. In this manner, passive behavior allows the walking-assistant robot to adapt to a user’s motion intent and move in compliance with user. Meanwhile, the active guidance adjusts the linear velocity and the direction of the robot in real time in response to the environmental data received from the on-board laser scanner. The developed algorithms have been implemented on a self-constructed walking-assistant robot. Experimental results validate the proposed design and demonstrate that the robot can actively avoid unexpected obstacles while move passively following the user to the destination.

An Aquatic Robot Propelled by an Internal Rotor

Abstract: Unmanned aquatic vehicles and robots are of tremendous importance in a variety of applications. In this paper, we present the model of an underactuated aquatic robot that is propelled by an internal rotor. The propulsion of the robot is based on the exchange of momentum between the body and water that is mediated by the creation of vorticity at the trailing edge of the robot. The robot does not have any external fins, propellers, or articulated joints allowing for very easy fabrication. Experimental data on its locomotion and maneuverability are presented.

S-Surge: Novel Portable Surgical Robot with Multiaxis Force-Sensing Capability for Minimally Invasive Surgery

Abstract: To achieve a compact and lightweight surgical robot with force-sensing capability, in this paper, we propose a surgical robot called “S-surge,” which is developed for robot-assisted minimally invasive surgery, focusing mainly on its mechanical design and force-sensing system. The robot consists of a 4-degree-of-freedom (DOF) surgical instrument and a 3-DOF remote center-of-motion manipulator. The manipulator is designed by adopting a double-parallelogram mechanism and spherical parallel mechanism to provide advantages such as compactness, simplicity, improved accuracy, and high stiffness. Kinematic analysis was performed in order to optimize workspace. The surgical instrument enables multiaxis force sensing including a three-axis pulling force and single-axis grasping force. In this study, it will be verified that it is feasible to carry the entire robot around thanks to its light weight (4.7 kg); therefore, allowing the robot to be applicable for telesurgery in remote areas. Finally, it will be explained how we experimented with the performance of the robot and conducted tissue manipulating task using the motion and force sensing capability of the robot in a simulated surgical setting.

An Ultralightweight and Living Legged Robot

Abstract: In this study, we describe the most ultralightweight living legged robot to date that makes it a strong candidate for a search and rescue mission. The robot is a living beetle with a wireless electronic backpack stimulator mounted on its thorax. Inheriting from the living insect, the robot employs a compliant body made of soft actuators, rigid exoskeletons, and flexure hinges. Such structure would allow the robot to easily adapt to any complex terrain due to the benefit of soft interface, self-balance, and self-adaptation of the insect without any complex controller. The antenna stimulation enables the robot to perform not only left/right turning but also backward walking and even cessation of walking. We were also able to grade the turning and backward walking speeds by changing the stimulation frequency. The power required to drive the robot is low as the power consumption of the antenna stimulation is in the order of hundreds of microwatts. In contrast to the traditional legged robots, this ro...

Design and control of an inchworm-inspired soft robot with omega-arching locomotion

Abstract: This paper presents an inchworm inspired soft robot composed of the soft body, the front foot as well as the back foot. Compared to the traditional inchworm-type robot consisting of rigid components, the driven mode for the soft robot is more simple. The soft robot inspired by the inchworm has higher locomotion efficiency than the other bionic soft robot. The main idea of this paper is to imitate the “Ω” motion shape of biology inchworm based on a silicone square tube with strain-limiting layers. Besides, each foot of the robot made through 3D printing technology together with metal sheet can produce different friction coefficients to achieve the anchor-motion movement. Then, the robot realizes an inchworm-like locomotion under certain actuation patterns. Experimental results show that the proposed robot has excellent performance.

Design and characteristic evaluation of a novel amphibious spherical robot

Abstract: This paper presents a new type of amphibious spherical robots. The robot includes four drive units. Each drive unit consists of two servo motors, a water-jet propeller, a DC motor and a wheel. The robot can constitute three movement structure ways according to the environment. When the robot enters water, it adopts water jet propulsion. According to different land conditions, there are two movement patterns to switch. One is a quadruped movement pattern which is available to climb over obstacles; the other is a driving wheel movement pattern which is used to speed up the movement of robot under the flat terrain. Characteristic evaluation experiments on land for a novel amphibious spherical robot were conducted. Underwater motions of the robot mainly rely on the four water-jet propellers, it is necessary to measure relationship between actuating force of the water-jet propeller and the duty ratio. Gambit software is employed to establish and mesh the water-jet propulsion model. Simulation analysis of the models is implemented by FLUENT software. Localization control of the robot and wireless control of the robot were conducted. Finally, experiment results indicated that the developed novel amphibious spherical robot is feasible to develop marine resources and implement marine missions.

Kinematics, Dynamics and Power Consumption Analysis of the Hexapod Robot During Walking with Tripod Gait

Abstract: The paper is focused on the kinematic, dynamic and power consumption analysis of the constructed prototype of the hexapod robot walking with tripod gait on a flat and hard ground. The movements of the robot legs are controlled by different well known oscillators working as central pattern generators (CPGs). The mentioned models, as well as those proposed in our previous paper, are employed and compared from the viewpoint of fluctuations of the robot gravity center both in vertical and movement direction, contact forces between the robot legs and the ground as well as energy demand of the whole robot during walking process. Time histories of the key kinematic and dynamic quantities describing locomotion of the robot are numerically studied and experimentally verified. Power consumption of the whole robot is experimentally investigated based on the current consumption in the applied servo motors which drive the robot legs. We show that the proposed CPG model is more efficient regarding acceleration/decelera...

Trajectory generation for a walking in-pipe robot moving through spatially curved pipes

Abstract: In this paper, a walking in-pipe robot is studied. The robot has six legs, each consisting of 3 links connected via rotary joints. The legs are attached to the robot’s body. The work is focused on the problem of generating desired position and orientation for the robot’s body, using a given footstep sequence. An iterative geometric algorithm for generating orientation sequence is proposed. The problem of finding the desired position of the center of mass of the robot’s body is formulated as a problem of minimizing stretching of the robot’s legs during steps. Also, an analytical solution for inverse kinematics problem has been given. All proposed algorithms do not require extensive calculation and use basic algebraic operations.

Door opening by joining reinforcement learning and intelligent control

Abstract: In this paper we address a problem of how to open the doors with an articulated robot. We propose a novel algorithm, that combines widely used reinforcement learning approach with intelligent control algorithms. In order to speed up learning, we formed more structured search, which exploits physical constraints of the problem to be solved. The underlying controller, which acts as a policy search agent, generates movements along the admissible directions defined by physical constraints of the task. This way we can efficiently solve many practical problems such as door opening without almost any previous knowledge of the environment. The approach was verified in simulation as well as with real robot experiment.

Design of a 6-DOF collaborative robot arm with counterbalance mechanisms

Abstract: Most collaborative robots use high-power motors for a good weight-to-payload ratio, thus leading to not only an increase in manufacturing cost but also possibility of injury at a collision between a human and a robot. To maintain high-performance with low-power driving units, a spring-based counterbalance mechanism (CBM) and a robot arm based on these CBMs were developed in our previous study. In this study, a 6-DOF collaborative robot equipped with a multi-DOF CBM is proposed. A double parallelogram linkage and a slider-crank mechanism are employed for a compact and durable design of a multi-DOF CBM. Unlike the previous prototypes in which some portions of CBMs were protruded out of the robot body due to their large volume, the proposed CBMs can be embedded inside the robot links. The performance of the developed CBM and collaborative robot were verified based on simulations using dynamic simulation software. Simulation results show that the proposed CBMs can effectively reduce the joint torques required to operate the robot. This reduction in the torque enables low-power motors to be used in a collaborative robot, thus significantly improving collision safety and energy efficiency.

A cable-driven robot for architectural constructions: a visual-guided approach for motion control and path-planning

Abstract: Cable-driven robots have received some attention by the scientific community and, recently, by the industry because they can transport hazardous materials with a high level of safeness which is often required by construction sites In this context, this research presents an extension of a cable-driven robot called SPIDERobot, that was developed for automated construction of architectural projects The proposed robot is formed by a rotating claw and a set of four cables, enabling four degrees of freedom In addition, this paper proposes a new Vision-Guided Path-Planning System (V-GPP) that provides a visual interpretation of the scene: the position of the robot, the target and obstacles location; and optimizes the trajectory of the robot Moreover, it determines a collision-free trajectory in 3D that takes into account the obstacles and the interaction of the cables with the scene A set of experiments make possible to validate the contribution of V-GPP to the SPIDERobot while operating in realistic working conditions, as well as, to evaluate the interaction between the V-GPP and the motion controlling system The results demonstrated that the proposed robot is able to construct architectural structures and to avoid collisions with obstacles in their working environment The V-GPP system localizes the robot with a precision of 0006 m, detects the targets and successfully generates a path that takes into account the displacement of cables Therefore, the results demonstrate that the SPIDERobot can be scaled up to real working conditions

Calibration of a flexible measurement system based on industrial articulated robot and structured light sensor

Abstract: To realize online rapid measurement for complex workpieces, a flexible measurement system based on an articulated industrial robot with a structured light sensor mounted on the end-effector is developed. A method for calibrating the system parameters is proposed in which the hand-eye transformation parameters and the robot kinematic parameters are synthesized in the calibration process. An initial hand-eye calibration is first performed using a standard sphere as the calibration target. By applying the modified complete and parametrically continuous method, we establish a synthesized kinematic model that combines the initial hand-eye transformation and distal link parameters as a whole with the sensor coordinate system as the tool frame. According to the synthesized kinematic model, an error model is constructed based on spheres’ center-to-center distance errors. Consequently, the error model parameters can be identified in a calibration experiment using a three-standard-sphere target. Furthermore, the redundancy of error model parameters is eliminated to ensure the accuracy and robustness of the parameter identification. Calibration and measurement experiments are carried out based on an ER3A-C60 robot. The experimental results show that the proposed calibration method enjoys high measurement accuracy, and this efficient and flexible system is suitable for online measurement in industrial scenes.

Functional Co-Optimization of Articulated Robots

Abstract: We present parametric trajectory optimization, a method for simultaneously computing physical parameters, actuation requirements, and robot motions for more efficient robot designs. In this scheme, robot dimensions, masses, and other physical parameters are solved for concurrently with traditional motion planning variables, including dynamically consistent robot states, actuation inputs, and contact forces. Our method requires minimal user domain knowledge, requiring only a coarse guess of the target robot configuration sequence and a parameterized robot topology as input. We demonstrate our results on four simulated robots, one of which we physically fabricated in order to demonstrate physical consistency. We demonstrate that by optimizing robot body parameters alongside robot trajectories, motion planning problems which would otherwise be infeasible can be made feasible, and actuation requirements can be significantly reduced.

Energy-Efficient Robot Configuration for Assembly

Abstract: Optimizing the energy consumption of robot movements has been one of the main focuses for most of today's robotic simulation software. This optimization is based on minimizing a robot's joint movem ...

A review on passive gravity compensation

Abstract: An articulated robot arm with multiple links will spend most of its energy on carrying its own weight when it works against gravity. A gravitational torque occurs due to the mass of the robot links and the payload, but most of the gravitational torque is caused by the mass of the robot links. This degrades the dynamic performance and ability to withstand external forces. In the presented review work, attention is mainly focused on various passive gravity compensation methods with the help of which desired performance is achieved.

Multi-robot and task-space force control with quadratic programming

Abstract: We extend the task-space multi-objective controllers that write as quadratic programs (QP) to handle multi-robot systems as a single centralized control. The idea is to assemble all the 'robots' models and their interaction task constraints into a single QP formulation. By multi-robot we mean that whatever entities a given robot will interact with (solid or articulated systems, actuated or not or partially, fixed-base or floating-base), we model them as robots and the controller computes the state of the overall system and their interaction forces in a physically consistent way. By doing so, the tasks specification simplifies substantially. At the heart of the interactions between the systems is the contact forces: we provide methodologies to achieve reliable force tracking with our multi-robot QP controller. The approach is assessed with a large panel of experiments on real complex robotic platforms (full-size humanoid, dexterous robotic hand, fixed-base anthropomorphic arm), performing whole-body manipulation, dexterous manipulation and robot-robot co-manipulation of rigid floating objects and articulated mechanisms such as doors, drawers, boxes, or even smaller mechanisms such as a spring-loaded click pen. The implementation code of the controller is made available in open source .

Constraint finite‐time control of redundant manipulators

Abstract: Summary This work addresses the problem of the accurate task-space control subject to finite-time convergence. Dynamic equations of a redundant manipulator are assumed to be uncertain. Moreover, globally unbounded disturbances are allowed to act on the manipulator when tracking the trajectory by the end effector. Furthermore, the movement is to be accomplished in such a way as to optimize some performance index. Based on suitably defined task-space non-singular terminal sliding vector variable and the Lyapunov stability theory, we derive a class of inverse-free robust controllers consisting of a Jacobian transpose component plus a compensating term, which seem to be effective in counteracting uncertain dynamics, unbounded disturbances and (possible) kinematic singularities met on the robot trajectory. The numerical simulations carried out for a redundant manipulator of a Selective Compliant Articulated Robot for Assembly (SCARA) type consisting of three revolute kinematic pairs and operating in a two-dimensional task space illustrate performance of the proposed controllers. Copyright © 2016 John Wiley & Sons, Ltd.

Predictive control of 5 DOF robot arm of autonomous mobile robotic system motion control employing mathematical model of the robot arm dynamics

Abstract: The paper deals with a design of model predictive control (MPC) as an example of the advanced local motion control of articulated robot arms in the scope of manipulation operations within the intradepartmental transportation among workplaces. Initially, the use of articulated robotic arms as a part of mobile robotic systems is discussed. Then, the convenient composition of mathematical models of kinematics and dynamics of the aforementioned robot arms is introduced. Thereafter, MPC design is explained. The proposed theoretical methods of the mathematical modeling and control design are demonstrated by the simulation of the 5 degrees of freedom robot arm composed of drive, joint and arm modules of the Schunk Co.

Development of articulated robot trajectory planning

Abstract: Articulated robot is now widely employed in manufacture, such as, welding, painting, and assembly, with high precision and endurance. It plays an important role in scientific and technological innovation. Trajectory planning of articulated robot is one of the key researches in industrial robot. The commonly used trajectory planning algorithm of articulated robot, such as, polynomial interpolation algorithm in joint space and linear interpolation in Cartesian space are introduced. Researches on articulated robot trajectory planning are surveyed. Meanwhile these articulated robot trajectory planning algorithms are analysed. Some further researches and developing trend of articulated robot trajectory planning are indicated.