Philip Webb

Automated assembly of fuselage skin panels

Purpose – This paper aims to describe the development and testing of a system for the automated assembly of aircraft fuselage panels.Design/methodology/approach – The system described in this paper uses a low‐cost industrial robot and laser stripe sensor to assemble stringers on to a fuselage panel prior to riveting. The method uses a combination of measurement and best fit placement algorithms to optimally locate parts relative to existing features.Findings – The paper demonstrates that with a combination of metrology and mathematical processing standard industrial robots can be used to assemble aero‐structure subassemblies. The paper also demonstrates that the system can work within the tolerances required within the aerospace industry.Originality/value – The paper introduces techniques for compensating for the inherent distortion that occurs in airframe components during manufacture. This is an enabling technology that will significantly increase the number of possible applications for industrial robot...

Automated aerostructure assembly

Purpose – Describes the application of standard industrial robots to the assembly and riveting of aerostructure sub‐assemblies.Design/methodology/approach – Describes the design and operation of special purpose end‐effectors for assembly and solid riveting and their integration in an aerostructure sub‐assembly fabrication cell. The robots are controlled by a novel control system which allows the cell to compensate for distortion and misalignment of the components.Findings – Demonstrates that with advanced control standard industrial robots can be used to assemble aerostructure sub‐assemblies.Originality/value – Introduces techniques for compensating for the inherent distortion that occurs in airframe components during manufacture. This is an enabling technology that will significantly increase the number of possible applications for robots in the assembly of aerostructures.

High-resolution beam forming for ultrasonic arrays

Array processing techniques are common in radar, sonar, and medical ultrasound. However, little work has been reported on the use of array processing with airborne ultrasound. This paper describes the application of array beam forming to airborne ultrasound. It also introduces a processing method which allows the separation between receiving elements to he increased above the traditional /spl lambda//2 limitation. This has the effect of increasing the resolution significantly above that normally expected from traditional array processing methods. A full evaluation of the method is given, a full error analysis of the resulting system is provided, and a comprehensive set of results are presented. The angular and longitudinal resolution of the improved beam former are also derived.

Error reduction for an inertial-sensor-based dynamic parallel kinematic machine positioning system

This paper addresses the development of an error reduction strategy for an inertial-sensor-based system for measuring the displacement of parallel kinematic machine (PKM) struts and hence the tool centre point pose. The error reduction strategy can significantly improve the performance of low-cost accelerometers and has many potential generic inertial measurement applications. Inertial measurement systems are prone to errors introduced by manufacturing error, system set-up error and environmental factors. To accurately measure displacement the errors and noise contaminating the inertial data must be removed. Based on data analysis, methods are developed in this paper to remove bias error, and correct integration error through band limitation, error modelling and velocity reconstruction. The velocity reconstruction algorithm described significantly improves the performance of the system and is novel in its use of the bounded nature of the strut displacement. The inertial measurement system described is evaluated using a single PKM-Strut test bed for linear movement and the experimental results are presented and analysed.

The use of the TI2 manufacturing system on a double-curvature aerospace panel

Abstract The aircraft manufacturing industry is continually seeking new techniques for the automation of manufacturing and assembly tasks. The application of automation is limited by the size and compliance of the structures, the low manufacturing volumes and the inherent dimensional variability between assemblies. In addition, a further requirement is to reduce the reliance on complex fixturing systems through the adoption of techniques enabling a ‘jigless assembly’ philosophy. The University of Nottingham recently completed a study as part of the Engineering and Physical Science Research Council (EPSRC)-funded Jigless Aerospace Manufacturing (JAM) Project into the use of the TI2 system to meet the objectives outlined above. The paper presents the practical work completed and the results obtained from the machining of a double curvature aircraft panel.

Robot guidance using ultrasonic arrays

The flexibility of robots can be considerably increased by having sensors that can detect the location and orientation of the components that are being manipulated by the robots. Vision systems have been widely applied to this problem, but there has been very little reported work on the use of ultrasonic sensors. This article reports the use of novel ultrasonic sensors that have been manufactured in-house to measure the range and bearing of a target and guide the robot in a pick and place operation. The configuration of the transducer is described as well as the signal processing method employed. Experimental results are given and future developments and applications of the system are described.

The Development of a Scale to Evaluate Trust in Industrial Human-robot Collaboration

Trust has been identified as a key element for the successful cooperation between humans and robots. However, little research has been directed at understanding trust development in industrial human-robot collaboration (HRC). With industrial robots becoming increasingly integrated into production lines as a means for enhancing productivity and quality, it will not be long before close proximity industrial HRC becomes a viable concept. Since trust is a multidimensional construct and heavily dependent on the context, it is vital to understand how trust develops when shop floor workers interact with industrial robots. To this end, in this study a trust measurement scale suitable for industrial HRC was developed in two phases. In phase one, an exploratory study was conducted to collect participants’ opinions qualitatively. This led to the identification of trust related themes relevant to the industrial context and a related pool of questionnaire items was generated. In the second phase, three human-robot trials were carried out in which the questionnaire items were applied to participants using three different types of industrial robots. The results were statistically analysed to identify the key factors impacting trust and from these generate a trust measurement scale for industrial HRC.

Error significance analysis and compensation for HPKMs

Purpose – The purpose of this paper is to describe a novel error‐ranking methodology and two compensation strategies for hybrid parallel kinematic machines (HPKMs).Design/methodology/approach – The paper outlines an error analysis methodology developed for HPKMs and applies the technique to a typical industrial HPKM. Based on the results of this, two compensation strategies are developed and implemented, for both mass‐induced and thermal errors.Findings – The paper demonstrates and quantifies the performance improvements possible with appropriate error compensation strategies.Originality/value – The paper introduces a novel and generic methodology for error source analysis and describes two fully implemented compensation strategies which result in a significantly improved level of system performance.

The Design and Realisation of a Flexible Rapid Assembly Aero-Structure Manufacturing Cell – A Simulation Driven Approach

The use of simulation is a recognised part of the design process for automated systems and this has been particularly so in the development of the very large machines used in aero-structure manufacture. As part of an ongoing research project at the University of Nottingham a flexible rapid assembly cell is currently being developed that will be capable of manufacturing a number of different aero-structure sub-assemblies. The individual technologies required such as riveting, drilling and assembly have been developed and the complete cell is now being realised. A key enabler for the realisation of the cell has been the use of simulation, both in the development stage and as a central component of the operating and programming systems. This paper will describe the application of simulation techniques within the cell and during its design.

The development and application of a multiple wavelength illumination technique for the vision-based process monitoring of aero-structure riveting

Airframe riveting is a critical process that requires high levels of process monitoring and quality assurance due to the very high risk associated with the failure of such joints. This paper describes the development of the enabling technology developed for a machine vision-based process monitoring system. One of the key factors affecting the performance of a machine vision system is the quality of the lighting. In the application described in this paper the available lighting was severely limited by the confined space in which the system had to operate. The problem was also compounded by the reflective nature of the objects to be examined. The initial images obtained were not suitable for further processing due to the presence of significant shadows and specular reflections. A novel solution to this problem based on multiple wavelength illumination and signal processing is presented along with results from experimental trials of the approach.