Heping Chen

Integrated robotic system for high precision assembly in a semi‐structured environment

Purpose – This paper aims to develop a strategy for high‐precision assembly in a semi‐structured environment based on vision and force control.Design/methodology/approach – The position and orientation of a part are identified using the vision system. The force/torque control algorithm is then applied to perform a tight‐tolerance assembly that is a high‐precision assembly.Findings – The tight tolerance assembly in a semi‐structured environment is successfully implemented using vision guidance and force/torque‐control strategy.Practical implications – The developed methodology can be applied to tight tolerance assembly, such as forward‐clutch assembly, torque‐converter assembly, etc.Originality/value – An industrial assembly methodology has been developed and implemented for high‐precision assembly in a semi‐structured environment. This innovation has many potential applications in automotive manufacturing.

On-Line Path Generation for Robotic Deburring of Cast Aluminum Wheels

Cast aluminum wheels must be deburred and polished before chrome plating operation. Manual deburring and polishing is tedious and monotonous. Industrial robots are attracting more and more attention for the deburring applications. However, Each wheel path program was taking eight to ten weeks to create because the position and orientation of the deburring tool must be accurately identified based on the curvature of the wheel. To solve this problem, we developed a practical 6 DOF robot path generation method using hybrid force and visual servoing methodology. The force servoing keeps the robot tool continuously contacting with the wheel surface and the visual servoing controls the robot tool to follow a marked tool path on the wheel while the position and orientation are controlled and recorded. A robot path is then generated from the recorded data. Experiments are performed and the experimental results demonstrate that the developed algorithm can be used to automatically generate accurate 6 DOF robot paths for deburring aluminum wheels in less than an hour. This significantly reduces the robot programming time. The developed technology can also be used for robot path generation in many other manufacturing applications, such as welding and strip painting

Toward robotizing powertrain assembly

This paper presents the recent progress of using robotics in automotive powertain assembly manufacturing processes. After briefly describing force control and vision-guided robot (VGR), we introduce successful implementation of robotic assembly for transmission torque converters, VGR-based engine head assembly, transmission valve body assembly and engine piston installation. Then we discuss other robotic assembly related technologies such as visual servoing and assembly parameter optimization and followed by discussing assembly production line evolution such as the merging of automated-guided vehicle (AGV). The successful model of collaborative development between Ford Advanced Manufacturing Technology Development (AMTD) and ABB Robotics is also mentioned and reviewed.

Robotic wheel loading process in automotive manufacturing automation

The paper aims to develop an automated wheel loading system in the trim-and-final assembly in automotive manufacturing. Currently most of the trim-and-final assemblies are still done manually since the production lines are typically moving randomly. Industrial robots are hardly used to perform any assembly tasks on the randomly changing environments because it is difficult for conventional industrial robots to adjust to any sort of change. Therefore, more intelligent industrial robotic system has to be developed to adopt the random motion of the moving production line for the wheel loading process. This paper presents an intelligent robotics system that performs the wheel loading process while the car is moving randomly with the production line using a synergic combination of visual servoing and force control technology. The developed intelligent robotic technology has been successfully implemented to assembly the wheel onto the car. This practical solution of performing wheel loading on the moving production line, which is not available on the current industrial robot market, can save a lot of money and increase the assembly quality for automotive manufacturing. Since the developed platform is based on the synergic combination of visual servoing and force control technology, it can be used in other areas, such as seam tracking, battery loading and seat loading etc.

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.

Automated robot programming based on sensor fusion

Purpose – Aims to demonstrate how an automated robot program generation method can be developed and implemented.Design/methodology/approach – A visual and force servoing method to automatically generate robot paths and robot programs, based on position, force and vision sensor fusion, was developed.Findings – By using a hybrid control algorithm the robot is controlled to follow the feature on a surface with position and orientation control.Originality/value – The developed method can be applied to generate tool paths for many manufacturing tasks automatically, which can greatly reduce the robot programming time and decrease the manufacturing cost.

The challenges of integrating an industrial robot on a mobile platform

This paper provides a description of a uniquely mounted industrial robot. The described configuration includes an IRB6620 industrial robot with a tool changer and multiple tools that are installed on a highly customized truck chassis. Industrial robots are typically anchored to a shop floor which would normally limit the operational range of industrial robotics and require that all parts and materials be delivered to the robot. While this is normal and practical in instances where systems are structured to handle high volume part demand, it inherently limits the rapid mobility of a system. Such mobility would also be limited by the typical supply requirements of industrial equipment, such as process data communication, power, fluids, and compressed air or other gasses. However, new market requests have emerged for industrial robotics that prompted this particular in-house development of a mobile and uniquely self sufficient robotic arm platform. This wheeled vehicular platform is able to travel any reasonably navigable terrain, including off road, and is reliant solely on its own generated power or otherwise carried supplies. This paper presents the prototype development of such a platform that is self sufficient for electrical power, as well as compressed air from on board sources. This installation has been successfully developed to carry out various demonstration tasks by use of interchangeable tooling. This solution provides a mobile platform for an industrial robot which could be used in any location as long it is accessible to the mobile platform.

Towards performance analysis of wheel loading process in automotive manufacturing

In our previous work, we developed an automated wheel loading system for the trim-and-final assembly in automotive manufacturing. Since the actual system is difficult to set up to evaluate the performance of a wheel loading system, a simulation package should be available to estimate the performance of the system with a chosen robot. This paper presents a method to analyze the performance of a wheel loading process using an industrial robot. The force control and visual servoing loops are analyzed to estimate the assembly time and tracking errors. The simulation results of the wheel loading system are verified using experimental results. The comparison indicates that the developed method can be used to estimate the performance of the wheel loading process. Our future work will be focused on validating the developed method using different robotic systems.

Real-time 3D shape inspection system for manufacturing parts based on three-step stripe pattern

The objective of this paper is to propose robust, three-step, and spatiotemporal structured light patterns for rapid 3D shape inspection system. To reduce the negative influence of inspected part texture and ambient light, the patterns are constructed by stripe boundary using monochromatic light. The stripe sequence is generated by the Euler Circuit of graph theory under the proposed constraints in space and over time. The location of the boundary stripe is detected by the opposite intensity of the two adjacent stripes instead of the gradient operator so the accuracy is improved. The codeword for each stripe boundary is unique in the projector image plane, depending on the consecutive stripe codes over time. To speed up the corresponding pixel searching between the projector and the camera, the corresponding pixel is formed by the intersection of the epipolar line and the stripe boundary. Last, experiments are conducted to evaluate the robustness and accuracy of the inspection system using the proposed patterns. The results demonstrate that the system has high accuracy performance and high density.