Xiongzi Li

Automated industrial robot path planning for spray painting process: A review

Industrial robots are widely used to paint final products in many industries, such as automotive and furniture etc. Robot path planning based on the CAD models of parts for spray painting is critical for product quality, process cycle time and material waste etc. Currently automated robot path planning has always caused a bottleneck for the spray painting processes because typical manual teaching methods are time consuming, error-prone and skill dependent. Thus, it is essential to develop automated tool path planning methods to replace manual tool path planning ones in order to reduce the cost and improve product quality. This challenging research topic has been receiving more and more attention from both academia and industry. Therefore, a review of automated tool path planning methods is necessary to investigate the advantages and disadvantages of the current techniques.

Practical industrial robot zero offset calibration

Current manufacturing trends require industrial robot to be more and more accurate in order to accomplish more and more complicated manufacturing processes. Robot calibration enables standard robots to achieve higher accuracies. Many complex and/or expensive calibration methodologies have been developed and implemented successfully. However, they are difficult to be used in the manufacturing floor because of the cost and flexibility. Therefore, a calibration method that can be used to calibrate robots easily and economically will have a big market impact. Among all robot kinematics parameters, robot zero offset has a much larger influence on robot positioning accuracy. To accurately calibrate the robot zero offset, we developed a practical industrial robot zero offset calibration method that can be used in the manufacturing floor without high skill requirements of the operators. The method is based on tracking a laser line in the robot workspace. The robot joint angles are recorded during the tracking. Using the joint angle data, the robot zero offset can be estimated. The estimated value is then used to offset the encoder to evaluate the estimated values.

A review of CAD‐based robot path planning for spray painting

Purpose – Paint path planning for industrial robots is critical for uniform paint distribution, process cycle time and material waste, etc. However, paint path planning is still a costly and time‐consuming process. Currently paint path planning has always caused a bottle‐neck for manufacturing automation because typical manual teaching methods are tedious, error‐prone and skill‐dependent. Hence, it is essential to develop automated tool path‐planning methods to replace manual paint path planning. The purpose of this paper is to review the existing automated tool path‐planning methods, and investigate their advantages and disadvantages.Design/methodology/approach – The approach takes the form of a review of automated tool path‐planning methods, to investigate the advantages and disadvantages of the current technologies.Findings – Paint path planning is a very complicated task considering complex parts, paint process requirements and complicated spraying tools. There are some research and development effort...

High-accuracy visual/PSD hybrid servoing of robotic manipulator

This paper presents a new and effective multisensor based control strategy for high-accuracy/precision and high-efficiency automatic robot localization and calibration. The strategy combines both coarsely visual servo and fine position-sensitive detector (PSD) servo control methods. In a large field of view, an image-based visual servo control system is developed to roughly guide the laser beam, which is from a single laser pointer mounted at the end-effector of robot, to project to the high-resolution segmented PSDs. Once the laser spot is projected onto the active area of PSD, the control will be switched to the high-resolution PSD feedback and servoing for fine positioning. The experimental results conducted on an ABB industrial robot IRB1600 verify the effectiveness of the developed visual/PSD hybrid servo controllers as well as demonstrate that the high accuracy 30 mum of robot localization can be approached. The development of the hybrid control system and method will be a major step for achieving high-performance automatic robot calibration.

An automated method to calibrate industrial robot joint offset using virtual line-based single-point constraint approach

This paper describes an industrial robot joint offset calibration method called the virtual line-based single-point constraint approach. Previous methods such as using CMM, laser trackers or cameras are limited by the cost or the resolution. The proposed method relies mainly upon a laser pointer attached on the end-effector and single position-sensitive detector (PSD) arbitrarily located on the workcell. The automated calibration procedure (about three minutes) involves aiming the laser lines loaded by the robot towards the center of the PSD surface from various robot positions and orientations. The intersections of each pair of laser lines eventually should converge to the same point after compensating the joint offsets. An optimization model and algorithm have been formulated to identify the robot offset. For the highly precise feedback, a segmented PSD with a position resolution of better than 0.1 µm is employed. The mean accuracy of robot localization is up to 0.02 mm, and the mean error of the parameter identification is less than 0.08 degrees. Both simulations and experiments implemented on an ABB industrial robot verify the feasibility of the proposed method and demonstrated the effectiveness of the developed calibration system. The goal of fast, automated, low-cost, and high precision offset calibration are achieved.

Position-Sensitive Detector (PSD) Guided Servoing Method for Industrial Robot Calibration

This article presents our recently developed position-sensitive detector (PSD) guided servoing system for precise localization of industrial robots. The system is portable and affordable, and can position robot precisely so as to benefit further research on the calibration applications of industrial robots. To achieve highly precise position feedback, we have employed a high performance lateral-effect PSD with a resolution of 0.5 µ m. Based on the system kinematics and dynamics, a PSD guided servo (PSDGS) control method is then developed and simplified to be a planar motion control approach in which an on-line estimation of the transformation matrix between the PSD object and the robot base is applied. The experiments have been implemented on an ABB industrial robot IRB1600. The achieved results demonstrate that the mean localization precision of the industrial robot using the developed PSDGS method is totally better than 20 µ m.

Laser beam multi-position alignment approach for an automated industrial robot calibration

Robot calibration is widely used in the manufacture industry to enhance the accuracy of industrial robots. There are many reliable calibration systems in the market that are able to calibrate industrial robots. Those systems, however, are far from being a user friendly calibration tool; they are time consuming, very expensive, and usually requires too much human interaction. This paper proposes an innovative calibration approach for industrial robots able to overcome the problems that the current calibration systems are still facing. The proposed approach uses a control system capable of guiding the robots tool center point to an accurate multi-position alignment. Using the data of several positions, we are able to calculate the joint offsets using calibration algorithms. Throughout this paper the overall calibration system is presented and discussed. Finally, preliminary experimental results demonstrated the feasibility of the overall calibration system including device hardware, software and calibration algorithms.

Robotic additive manufacturing along curved surface — A step towards free-form fabrication

This paper presents a method and process to fabricate parts or structures by printing along curved surfaces with use of industrial robots. Software is developed to generate the fabrication path program that can take advantage of the 6-DOF articulated industrial robotics. Unlike the traditional vertically layer-by-layer 3D printing scheme, with the angled printing capability, a robotic fabrication path can be designed along the direction of curved surfaces or the direction of physical property requirements such as higher mechanical strength, specific thermal, electrical and even biomedical characteristics. The fabricating path program such as G-code will be then converted to a robot program such as RAPID. The part building process will be simulated and optimized for given robot specification, mounting configuration and building plate location. Robot dispensing software and hardware interface are employed to coordinate the motion speed and material extrusion rate. Robotic Additive Manufacturing (RAM) testing cells have been built to carry out and verify the printing scheme along curved surface, which is one step further towards free-form fabrication.

Automatic offline program calibration in robotic cells

The latest trends show that industrial robots have been used more and more to increase productivity and quality in general industries other than the traditional automotive industry. Instead of programming the robot by teaching the positions, offline programming has become more popular. User can simulate the programs in the computer first and the productivity can be increased tremendously. One critical step for the offline programming is that the robot cell needs to be calibrated first before the programs can be used in real world. This paper will introduce sensor based calibration methods to automatically calibrate the tool-data and work-object of the robot program.

Robot localization using an uncalibrated PSD servoing approach

In this paper, our recently developed high precision robot localization system employing high resolution (0.5 mum) position sensitive devices (PSD) is presented. The system is comprised of a structured laser pointer system attached to the robot end-effector and a PSD fixture. It is capable of feeding back the movement information of the TCP relative to the PSD frame. This is achieved by detecting the position of the laser beams emitted from the laser pointers onto the PSD surface. The system was well designed, mapped, and constructed and hence allows it to perform precision localization of the robot. Simulations and preliminary experiments demonstrated the effectiveness of the developed PSD guided localization system including the hardware, the software, and the uncalibrated algorithms.