6-DOF Industrial Robot Research Articles

Evaluation of Metallic Mold Surfaces Polished by an Industrial Robot with Stick Whetstones

Our ultimate goal is to develop an automatic polishing system that uses an industrial robot equipped with whetstones. The robot mimics the movements skilled workers make as they polish surfaces manually. This paper, the first step in the development of our system, presents experimental results to prove that our system completely removes the marks, which is the most time-consuming and crucial process for human workers, from the flat surfaces of metallic molds produced through the Electrical Discharge Machining (EDM) process. We build a polishing system that consists of a small 6-DOF industrial robot for material handling. Attached to its wrist is a six-axis force-torque sensor and it employs a whetstone holding mechanism. Before the robot system begins its polishing work, the normal force to be applied to the flat surface can be adjusted to a target value by altering the height of the hand. We adopt two polishing paths for the whetstone, reciprocating and zigzag. We then conduct experiments using the two paths, visually inspect the surface, and measure the surface roughness and shape. Based on the experimental results, we confirm that the system has completely removed the EDM mark layer. Although we find that the zigzag path leaves striped patterns on the polished surface, we are not able to determine their cause. Finally, we test three combinations of the two paths under different conditions to find the most suitable combination.

Feedforward Input Generation Based on Neural Network Prediction in Multi-Joint Robots1

Learning feedforward control based on the available dynamic/kinematic system model and sensor information is generally effective for reducing the tracking error for a learned trajectory. For new trajectories, however, the system cannot benefit from previous learning data and it has to go through the learning process again to regain its performance. In industrial applications, this means production line has to stop for learning, and the overall productivity of the process is compromised. To solve this problem, this paper proposes a feedforward input generation scheme based on neural network (NN) prediction. Learning/training is performed for the NNs for a set of trajectories in advance. Then the feedforward torque input for any trajectory in the predefined workspace can be calculated according to the predicted error from multiple NNs managed with expert logic. Experimental study on a 6-DOF industrial robot has shown the superior performance of the proposed NN based feedforward control scheme in the position tracking as well as the residual vibration reduction, without any further learning or end-effector sensors during operation.

Research on Kinematics and Trajectory Planning for 6-DOF Industrial Robot

The industrial robot is a typical electromechanical integration equipment constituted by operating machine, controller, servo drive system and the detection of sensing device. It is one of the most common industrial robots in the industrial field, which makes it work in almost any track or angle. This paper mainly presents the research on kinematics and trajectory planning for 6-DOF industrial robot. This study has finished the linear interpolation and arc interpolation in the Cartesian space. According to the advantages and disadvantages, this paper proposes the method of quadratic interpolation that meets the demands of 6-DOF industrial robot motion in the joints space and Cartesian space which ensures that the motion of 6-DOF industrial robot is smooth and stable.

Implementation of Dynamic Simulation System on Six DOF Industrial Robot

A dynamic simulation system whose model objects were industrial robot was designed. An advanced and quickly inverse kinematic algorithm was used to solve inverse kinematic equation for 6DOF industrial robot, the time of solve was improved. The method of trajectory planning was developed. The vision simulation for industrial robot was completed by Creator and Vega software. Simulation result shows that the requirement of kinematic control has been achieved and provides an intuitive and convenient tool for research of the kinematic control algorithm for industrial robot.

Motion Characteristics Analysis and Ground Simulation Method of Spin Target in Autonomous Capture

For autonomous capture of non-cooperative spin targets in on-orbit service,a simplified model of the target is built based on the operation characteristics of autonomous capture and the motion characteristics analysis of spin targets.Then,the motion simulation requirements of spin targets are proposed.On this basis,the ground simulation scheme for spin targets and two methods of motion simulation based on 6-DOF(degree of freedom) industrial robot are presented,i.e.the conventional simulation method based on manipulator end motion and the spin simulation method based on manipulator shoulder singularity.Finally,these two methods are introduced and simulated respectively.The simulation results show their feasibility and validity.

A General Framework of Mechatronic Modular Architecture

The independent designs guided by domain technologies of mechatronic system lead to the problem of hard compatibility and the difficulty to reuse resources between the systems. This paper presents an approach based on the reuse for modular mechatronic system, and a general framework for modular mechatronic system is designed. After the analysis of related characteristics of the mechatronic system, the modular principle of mechatronic system is proposed. Secondly, a general framework (F-Model) based on reusability of software and hardware in mechatronic system is developed. Following is to elaborate in details on the parts of software, hardware, and infrastructure of mechatronic system. Finally, 6-DOF industrial robot arm and medical accompany robot are taken as our experiment platform to design system based on F-Model. Results in practical application confirm the value of F-Model for reusing modules in designing mechatronic systems.

MDL-Based Control Method for Tele-robotic Systems

A control method based on motion description language(MDL) is proposed,to reduce requirement for network bandwidth and to distribute reasonably computational and communication resources in tele-robotic systems.The open-loop and closed-loop parameters in motion primitives are derived based on orthogonal decomposition of robot trajectory,by which the expressiveness of MDL is guaranteed,and four kinds of motion primitives are constructed for the tele-grasping task.A network-based tele-robotic system is constructed,in which the Phantom Omni is used as the master device and the Motoman 6-DOF industrial robot as the slave system.Experiments are conducted to compare the direct control method and the MDLbased control method,and experimental results demonstrate the feasibility and efficiency of the proposed method.

Calibration technology in application of robot-laser scanning system

A system composed of laser sensor and 6-DOF industrial robot is proposed to obtain complete three-dimensional (3-D) information of the object surface. Suitable for the different combining ways of laser sensor and robot, a new method to calibrate the position and pose between sensor and robot is presented. By using a standard sphere with known radius as a reference tool, the rotation and translation matrices between the laser sensor and robot are computed, respectively in two steps, so that many unstable factors introduced in conventional optimization methods can be avoided. The experimental results show that the accuracy of the proposed calibration method can be achieved up to 0.062 mm. The calibration method is also implemented into the automated robot scanning system to reconstruct a car door panel.

Kinematic Modeling for a 6-DOF Industrial Robot

The kinematic model of robots is to describe the nonlinear relationship between the displacement of joints and the position and orientation of the end-effector, which is an important part of robotics. Kinematic model has great influence on the robot’s accuracy and motion control. In this paper, we studied the robot’s kinematic modeling methods and analyzed the characteristics and singularity of traditional DH method. By analyzing and comparing the structural characteristics of a 6-DOF industrial robot a MDH method was chosen to establish kinematic model. From the kinematic model the joint coordinate systems, structural parameters and homogeneous transformation matrixes of the robot are obtained. The kinematic model provides a theoretical basis for the robot motion control, calibration and error compensation.

A new hybrid machine design for a 6 DOF industrial robot arm

Industrial robot arms are an essential part of automated manufacturing. They automate tasks such as component assembly, welding, light machining and spray painting due to their repeatability, speed and accuracy. The serial industrial robot arm architecture is the most ubiquitous in modern day manufacturing as its technology is mature; the machine architecture provides extreme dexterity and it has a large useful workspace. This architecture however does have some problems; first the machine mass distribution is not efficient as that mass is spread throughout the arm, and the arm itself contains significant inertia, which also leads to some inaccuracy and dynamic vibration problems. The reason for this lies in the location of the motors. This paper focuses on the conceptual design of a novel robotic arm having a hybrid nature, as its architecture departs from both the classic definitions of Serial Kinematics Machines (SKMs) and Parallel Kinematics Machines (PKMs).

A Comparative Study of Three Inverse Kinematic Methods of Serial Industrial Robot Manipulators in the Screw Theory Framework

In this paper, we compare three inverse kinematic formulation methods for the serial industrial robot manipulators. All formulation methods are based on screw theory. Screw theory is an effective way to establish a global description of rigid body and avoids singularities due to the use of the local coordinates. In these three formulation methods, the first one is based on quaternion algebra, the second one is based on dual-quaternions, and the last one that is called exponential mapping method is based on matrix algebra. Compared with the matrix algebra, quaternion algebra based solutions are more computationally efficient and they need less storage area. The method which is based on dual-quaternion gives the most compact and computationally efficient solution. Paden-Kahan sub-problems are used to derive inverse kinematic solutions. 6-DOF industrial robot manipulator's forward and inverse kinematic equations are derived using these formulation methods. Simulation and experimental results are given.

선재 압연 롤 교체 로봇 시스템

This paper presents the development of roll replacement robot system for wire-rod press rolls. The roll replacement robot system consist of a palletized railway truck, a 6-DOF industrial robot manipulator, a roll changing tool and a hydraulic power system. Results of simulation and pilot experiment show the roll changing task can be successfully automated using proposed robot system.

Direction Kernels: using a simplified 3D model representation for grasping

Humans decide how to carry out a spontaneous interaction with an object by using the whole geometric information obtained from their eyes. The aim of this paper is to present how our object representation model MWS (Adan in Comput Vis Image Underst 79:281–307, 2000) can help a robot manipulator to make a single and reliable interaction. The contribution of this paper is particularly focused on the grasp synthesis stage. The main idea is that the grasping system, through MWS, can use non-strict-local features of the contact points to find a consistent grasping configuration. The Direction Kernels (DK) concept, which is integrated into the MWS model, is used to define a set of candidate contact-points and interaction regions. The set of DK is a global feature which represents the principal normal vectors of the object and their relative weight in a three-connectivity mesh model. Our method calculates the optimal grasp points (which are ordered according to the quality function) for two-finger grippers, whilst maintaining the requirements of force closure and safety of the grasp. Our strategy has been extensively tested on real free-shape objects using a 6 DOF industrial robot.

Dynamic identification of a 6 dof industrial robot with a closed-loop output error method

AbstractOff-line robot dynamic identification methods are mostly based on the use of the inverse dynamic model, which is linear with respect to the dynamic parameters. This model is sampled while the robot is tracking reference trajectories that excite the system dynamics. This allows using linear least-squares techniques to estimate the parameters. This method requires the joint force/torque and position measurements and the estimate of the joint velocity and acceleration, through the bandpass filtering of the joint position at high sampling rates. Recently, the DIDIM method has been proposed and validated on a 2 degree-of-freedom robot. DIDIM method requires only the joint force/torque measurement. It is a closed-loop output error (CLOE) method based on a closed-loop simulation of the robot using the direct dynamic model, the same structure of the control law, and the same reference trajectory for both the actual and the simulated robot. The optimal parameters minimize the 2-norm of the error between the actual force/torque and the simulated force/torque. A validation experiment on a 6 dof Staubli TX40 robot shows that DIDIM method is very efficient on industrial robots.

Optimal Tracking and Identification of Paths for Industrial Robots

AbstractThis paper presents results from time-optimal path tracking for industrial robots. More specifically, three subproblems are studied and experimentally evaluated. The first is a contact-force control approach for determining the geometric robot motion, such that the tool centre point of the robot is moved according to the specification. The second problem is off-line solution of the optimisation problem describing the time-optimal path tracking problem, by using software which allows high-level implementation and solution of optimisation problems. The third problem is robust control of the robot during real-time path tracking based on the optimisation results determined off-line. An earlier developed control structure for robust control is implemented and tested in a robot system. This paper discusses the theory behind time-optimal path tracking and presents experimental results. Both contact-force controlled path identification and real-time path tracking of the identified path are evaluated on a 6-DOF industrial robot of type IRB140 from ABB.

Adaptive robust control for spatial hydraulic parallel industrial robot

This paper proposes an adaptive robust control for spatial hydraulic industrial robot, with a view of improving the performance of trajectory tracking under varying uncertainty. The mathematical models of mechanical system and electro-hydraulic driven system of spatial 6-DOF industrial robot are described, under Kane method and hydromechanics method. The backstepping design methodology is adopted to develop the nonlinear adaptive robust control scheme, which treats the modeling errors and coupling as bounded disturbances, and regards parameters without a priori knowledge as parametric disturbances. The dynamic tracking performances of the closed-loop system with the proposed control for the industrial robot are validated via simulation. The theoretical and simulation results demonstrate that the developed controller can exhibit good tracking performance

Modeling and Identification of Elastic Robot Joints With Hysteresis and Backlash

This paper presents a novel approach to the modeling and identification of elastic robot joints with hysteresis and backlash. The model captures the dynamic behavior of a rigid robotic manipulator with elastic joints. The model includes electromechanical submodels of the motor and gear from which the relationship between the applied torque and the joint torsion is identified. The friction behavior in both presliding and sliding regimes is captured by generalized Maxwell-slip model. The hysteresis is described by a Preisach operator. The distributed model parameters are identified from experimental data obtained from internal system signals and external angular encoder mounted to the second joint of a 6-DOF industrial robot. The validity of the identified model is confirmed by the agreement of its prediction with independent experimental data not previously used for model identification. The obtained models open an avenue for future advanced high-precision control of robotic manipulator dynamics.

On a 3D scanning robot system design problem

Performing the scanning of the human body by means of conventional scanners, we faced the challenge of data insufficiency. In this given paper we present a new solution to this problem, comprising industrial robots application. Our purpose was to develop a fully functional, accurate, cheap and safe 3D scanning system based on a 6DOF industrial robot applications.

Impedance Control for Elastic Joints Industrial Manipulators

An impedance controller for industrial manipulators is presented in this paper. Special attention has been paid to all the aspects that qualify an industrial robot, including decentralized proportional-integral-derivative position control, torsional flexibility, and friction at the joints. A discussion of a single-degree-of-freedom (DOF) case is first presented. The selection of the impedance parameters is based on the behavior in contact and makes reference to a new design parameter, the compliance bandwidth. The single-DOF analysis is then used in the design of the impedance controller for a complete manipulator. A rotational impedance based on a geometrically consistent representation of the orientation is used. Several experimental results obtained on a 6-DOF industrial robot, equipped with a force/torque sensor, are presented. The experiments show the effectiveness of the proposed approach in several conditions, including contact with an extremely stiff surface and noncontact/contact transition.

Time-varying input shaping technique applied to vibration reduction of an industrial robot

It is widely and frequently observed that industrial robots conducting fast motion involve serious residual vibration, the period of which varies with time. To address this time-varying residual vibration problem, this paper presents a practical solution based on a time-varying input shaping technique (TVIST). First, to suppress the time-varying vibration, a guideline for designing a practical TVIST is presented. Following the guideline, a TVIST for a heavy 6 DOF industrial robot is designed. In doing so, a simple yet effective equation is derived from robot dynamic equations to schedule the time-varying period. Furthermore, a simple payload-adaptation scheme is also included. Then, experiments are performed by using the TVIST for the industrial robot under spatial motion and payload variation. The experimental results show that the residual vibration is reduced to less than 14% of the original level in magnitude and the time delay caused by pre-filtering is shortened, demonstrating the efficiency and effectiveness of the proposed TVIST.