The application of rehabilitation robotics within manufacturing industry

John L Dallaway, Richard M Mahoney and Robin D Jackson
Department of Engineering
University of Cambridge, UK

1 Abstract

This paper describes the procedures adopted in the installation and evaluation of a prototype robotic manipulator within a manufacturing environment. The requirements and issues associated with the installation are contrasted with those evident within an office environment. The operation of the robotic system and its component parts are described. The recruitment of operators and the employment mechanisms involved are also discussed. An evaluation procedure has been developed to assess the performance of the robotic equipment with respect to existing practices.

2 Introduction

The application of robotic assistive devices within the manufacturing industry is a relatively underdeveloped area of research within the Rehabilitation Robotics community. With few exceptions, previous vocational applications have been office-based. Many of the issues involved in the implementation of assistive technology within typical manufacturing environments are similar to those in office-based situations. However, there are specific factors which must be addressed if the introduction of such technology is to be successful.

A recent project within the Department of Engineering, University of Cambridge has explored the potential of Rehabilitation Robotics within the manufacturing industry. A survey directed at the production managers of local companies was used to identify guiding criteria for evaluating the suitability of specific manufacturing tasks for people with manipulative disabilities using assistive technology [1]. Using these criteria, the task of visual inspection was selected for more detailed examination. A potential host company using non-automated visual inspection procedures was identified and key company personnel were involved in the specification of a demonstrator known as the Interactive Robotic Visual Inspection System (IRVIS). The demonstrator was installed within the company for a trial period and a disabled individual was employed as a trainee inspector to facilitate evaluation of the system.

The major goals of the IRVIS evaluation were to demonstrate that the appropriate application of robotic technology can expand employment opportunities for physically disabled individuals and that the employment of such individuals need not compromise overall productivity. A secondary goal was to demonstrate that the use of interactive robotic technology can also lead to improvements in the production process.

3 Personnel recruitment and employment

3.1 Recruitment

In recruiting a trainee inspector for evaluation of IRVIS, the interests of potential employees were given high priority. The project included an initial evaluation phase of six months. No guarantee of further employment could be made due to the experimental nature of the project. In this context, previously unemployed individuals were considered more suitable than those who would leave other, possibly more secure, employment. However, the psychological effect of providing employment to an individual and later withdrawing that employment through no fault of the employee's should not be underestimated. Within the UK, the Employment Service provides a mechanism known as the Sheltered Placement Scheme (SPS) through which individuals whose disability affects their productivity may gain employment. The term 'sheltered' is misleading in that participants may benefit from the scheme in a variety of work environments. The SPS was used as a form of recruitment bureau for the trainee inspector.

A 24 year old male was appointed under the SPS for the evaluation of IRVIS. He is local to the host company and had been unemployed for several years prior to the appointment. The trainee inspector uses a wheelchair due to Spina Bifida. He has reasonable manipulation ability, but is unable to lean forward or maintain certain other body positions without discomfort.

3.2 Employment

The SPS represented the most cost effective route to employment in this situation. Workers are strictly employed by the organisation administering the SPS. However, the employee adopts the employment conditions of the company at which he works. An SPS Placement Officer is responsible for assessing the productivity of each employee with respect to an able-bodied worker. The employment costs met by the host company are based on this assessment. In addition, the Placement Officer monitors the progress of employees and has some responsibility for their welfare.

4 Robot installation

4.1 Workplace adaptation

Issues of accessibility had to be resolved before the evaluation of IRVIS could commence. These issues were complicated by the fact that the trials were undertaken in a clean room environment. An accessibility audit was conducted at the site of the host company and recommendations for workplace adaptations were formulated. The SPS Placement Officer was able to recommend funding sources for the necessary workplace adaptations. Within the UK, the Special Aids for Employment Scheme will fund equipment to facilitate the employment of disabled individuals up to a maximum of £6,000. The most significant adaptation necessary was the provision of an additional wheelchair for exclusive use in the clean room.

4.2 Equipment integration

The installation of IRVIS within the host company demonstrated the complexity of the relationship between technologists and industrial management in collaborative ventures. The location of the equipment within the production area was influenced by the following factors: Office workers usually receive a formal education which is not specific to a particular company. Manufacturing work differs in that training is normally provided on site and is more company-specific. Visual inspection workers also benefit from the experience of their colleagues who are frequently able to offer advice on marginal and novel fault conditions. The physical dimensions of IRVIS made it necessary to position the equipment at some distance from the other inspectors. This reduced the potential for more informal types of training. The fact that the IRVIS operator used significantly different inspection equipment to the other inspectors also reduced the level of co-operation.

The importance of maintaining close links with the host company during the evaluation period was emphasised by the iterative process of system enhancement. Regular visits to the company provided a forum for the exchange of ideas both in the use of the existing equipment and in the ways in which it might be modified. It was also important to respond quickly to system malfunctions. However, it is not usually possible to guarantee a certain level of service support in the context of a research programme.

5 Operation

5.1 IRVIS

The Interactive Robotic Visual Inspection System (IRVIS) features a 5 degree of freedom manipulator designed and constructed within the Department of Engineering, University of Cambridge. The manipulator was constructed from standard ranges of linear aluminium extrusions and joints (figure 1). The mechanical structure is driven by DC servo motors using an OxIM Transputer-based control board. The control board communicates with a PC using an RS422 serial link. The translational and rotational axes of the circuit tray are driven by motors operating in a differential pair to reduce cable management requirements.

Figure 1. The IRVIS mechanical system

The manipulator holds a high quality video camera which is located and oriented with respect to a tray containing hybrid microcircuits. The tray size is dictated by the dimensions of the palettes used to transport circuits. The 5 degrees of freedom of the manipulator provide image translation in a plane, azimuth, elevation and focus. The camera and zoom lens provide object to monitor magnifications of approximately x30 to x200 using a high resolution 10" video monitor.

The manipulator is instructed using the Cambridge University Robot Language (CURL). CURL has been developed over a number of years within the rehabilitation engineering research programme at Cambridge. It has recently been re-structured to separate the device-specific code from the human-computer interface and interpreter [2]. Device independence is achieved by rigidly specifying the messages passed across a software interface between the CURL interpreter and the device-level control software. A CURL device driver incorporating the kinematics of the IRVIS manipulator was coded to facilitate the use of CURL within the prototype system [3].

CURL has also been ported to run under the Microsoft Windows operating environment which has now succeeded MS-DOS as the environment of choice for most PC users. The Windows-based interface offers considerable advantages to users both in terms of application integration and support for software-based access products [4]. The nature of the Windows environment enables the CURL user interface to be customised for specific applications. The interface used within the IRVIS system is shown in figure 2. CURL procedures allow the operator to move from one circuit to the next and to scan the surface of a particular circuit. When a potential fault is identified, the scanning may be interrupted and a number of direct control modes allow the operator to inspect the circuit more closely. In this application, the CURL command line interface is not required and is therefore hidden to avoid confusion.

Figure 2. The CURL user interface for IRVIS

The implementation of the user interface under Microsoft Windows allows the operator to log circuit faults using other applications running concurrently with CURL. The CURL device driver for IRVIS provides a continuous display of the camera location for this purpose. For example, a terminal window could allow defects to be recorded in a corporate database management system running on a remote computer.

5.2 Work patterns

The trainee operator did not use IRVIS exclusively. The concentration of the employee was most effectively maintained by varying his activities. He also received training in other aspects of the company's production process. It was intended that experience gained in other areas would enhance his employment prospects following the trials. The employee's use of the IRVIS manipulator was recorded using the log facility provided within CURL. The log file provided information concerning the duration and frequency of use. It also facilitated an analysis of each command and the sequences in which commands were invoked.

5.3 Employee integration

As previously mentioned, the siting of IRVIS at some distance from the main inspection areas reduced the ease with which the operator was able to establish a rapport with other workers. However, there is clear evidence that both the operator and the equipment were accepted within the work environment. The manipulator was not seen as a threat to existing inspection procedures. In fact, several workers have suggested other possible uses of the equipment within the area of Quality Assurance.

It was the intention of the IRVIS development team that the operator be included in any discussion concerning system behaviour and modification. This user-led approach provided benefits for both the operator and the technical evaluators. The operator initiated many minor improvements in the operation of the manipulator. These improvements resulted in a superior prototype which eased the task of visual inspection.

6 Evaluation

A quantitative evaluation of IRVIS was difficult due both to the nature of the work and also to the fact that the operator had no experience with conventional microscope-based inspection techniques. Initial training of the operator was achieved by providing a layout sheet of the circuit under inspection. The operator would highlight any circuit areas which appeared to be defective. An experienced inspector would then highlight in another colour any defective elements which the operator had missed. In initial trials, the operator recognised 63% of the circuit faults. The unrecognised faults were clearly visible using IRVIS and reflected the inexperience of the operator rather than any limitation in the equipment. Toward the end of the trials, the operator's recognition rate was approaching 100%.

It has become evident that certain faults on hybrid microcircuits are less readily detected using IRVIS than under a microscope. For example, scratches are more noticeable when there is some vibration in the system. The vibration causes light reflected by the scratch to flicker and thus attract the inspector's attention. Further comparisons between the two methods of inspection are planned. These comparisons will be performed by an experienced inspector.

The current user interface for the direct control of IRVIS has proved to be tedious for certain inspection operations. The operator expressed frustration at the delays incurred when zooming in on a potential fault and examining it from several angles. The major advantage of IRVIS over conventional inspection methods lies in the rigour with which the video camera scans each circuit. Inspectors using microscopes may accidentally skip the inspection of certain circuit areas if they are interrupted. IRVIS enforces a more rigid work pattern which is beneficial to workers in the area of Quality Assurance. A further benefit of IRVIS lies in the reduced handling of circuits. Circuit handling increases the possibility of damage to vulnerable components.

7 Conclusions

The installation of IRVIS within a manufacturing environment has provided employment for a physically disabled individual in the area of Quality Assurance which would not otherwise have been available. The operator was able to take full control of his work environment using a task-specific manipulator in conjunction with a highly configurable user interface. Evaluation of the IRVIS installation has demonstrated that the productivity of the operator is comparable with that of able-bodied colleagues.

Use of IRVIS by experienced inspectors has confirmed that the systematic work pattern enforced by the system provides substantial benefits in the context of Quality Assurance. Operators are less likely to omit circuit areas due to interruption or mental fatigue. The benefits of task pacing observed in other projects are also evident [5]. Within the manufacturing industry, the implementation of interactive robotic systems for use by able-bodied workers is clearly attractive to production managers. These considerations highlight the importance of universal design within the field of Rehabilitation Engineering.

Other benefits of the IRVIS installation have arisen from the incorporation of video technology within the system. IRVIS includes functions to capture images and store them in an image database. It is also possible to record circuit inspections using a VCR. These functions are useful both for training purposes and for illustration to clients.

The reliability of the prototype system and the duration of any down time clearly affected trust and confidence in the system, both on the part of the operator and the management personnel. It is important that support issues are given detailed consideration in any further application of the technology. The evaluation of IRVIS has also provided valuable information concerning future system enhancements. In particular, the time delays apparent in the direct control of IRVIS should be addressed. A number of pre-programmed routines could be incorporated to reduce operator effort during more precise inspection activities.

8 Acknowlegements

This project has been funded through the ACME directorate of the UK Science and Engineering Research Council and the Papworth Group. The authors acknowledge the assistance and support provided by Graham Barrett and Philip Nunn of Graseby Microsystems and by Graeme Dargie and Doug Scott of the Papworth Group.

9 References

  1. Gosine RG, Mahoney RM, Gatiss J, Jackson RD, Dargie G, Gibson J, Scott GD, Jones T (1991) Interactive robotics to aid physically disabled people in manufacturing tasks. IMechE Journal of Engineering Manufacture. 205. 241-245
  2. Dallaway JL, Mahoney RM, Jackson RD, Gosine RG (1993) An interactive robot control environment for rehabilitation applications. Robotica. 11. 541-551
  3. Mahoney RM, Dallaway JL, Jackson RD, Gosine RG (1992) Development of the robot control language CURL. ICORR 92 - Conference Papers.
  4. Dallaway JL, Mahoney RM, Jackson RD (1993) CURL - A robot control environment for Microsoft Windows. RESNA 93 - Proceedings. 510-511
  5. Anderson L, Dewees J, Ingalls R, Anderson M, Mallernee S (1993) Investigation of the utilization of a robotic arm by disabled persons in the workplace. Wichita Rehabilitation Engineering Center - Final report. 68-80
This paper may be referenced as follows:

Dallaway JL, Mahoney RM, Jackson RD (1994) The application of rehabilitation robotics within manufacturing industry. Proceedings of the fourth International Conference on Rehabilitation Robotics. 145-149.