Robots and Automated Manufacture
To serve its purpose, an industrial robot must be harnessed to a manufacturing task, be it welding, assembly, adjustment or the inspection of food products. Complex tasks are likely to require offline programming, both for economy of equipment use and to permit computer simulations for collision avoidance. Vision and other sensory systems are helping to extend the capabilities of robots, while programming techniques are making their use more accessible to the shop floor.
Inspec keywords: flexible manufacturing systems; quality control; CAD; welding; robots; feedback; force sensors; decentralised control; automatic optical inspection
Other keywords: automatic location editing; steering mechanism; legged robot; manufacturing process; visual feedback control; welding robot vision; automatic visual inspection; high-speed pattern recognition; off-line robot programming simulation; flexible automated assembly system; decentralised control; CAD; assembly robot program; automated welding machine; quality control; industrial robot; collision avoidance; robot force sensing; robot kinematics
Subjects: Production engineering computing; Multivariable control systems; Control in industrial production systems; Robotics; Industrial applications of IT; Robot and manipulator mechanics; Control engineering computing; Inspection and quality control; Production technology; Control applications in manufacturing processes
- Book DOI: 10.1049/PBCE028E
- Chapter DOI: 10.1049/PBCE028E
- ISBN: 9780863410536
- e-ISBN: 9781849193351
- Page count: 248
- Format: PDF
-
Front Matter
- + Show details - Hide details
-
p.
(1)
-
1 A novel steering mechanism for legged robots
- + Show details - Hide details
-
p.
1
–10
(10)
Many walking machines have six legs, since this allows an efficient and stable gait in which the machine is supported by two tripods of legs alternately. It is common to give each leg three powered joints so each foot can be moved up and down, backwards and forwards, and from side to side. This requires a total of 18 actuators, each with a driving device such as an amplifier or servovalve, and the associated cables or hoses. The weight, cost and complexity of all this equipment presents an obstacle to the widespread use of legged vehicles. Further, some manoeuvres such as turning, or even straight-line walking in some designs, requires the co ordinated action of several joints, presenting a considerable problem of computing, in real time, the joint angles and velocities needed, and driving the actuators to produce them. For many purposes there is no alternative to the fully servo-controlled 18 degree of freedom vehicle. However, at this early stage in the development of walking robots some investigations can be done with cruder machines. For example, there has been little research on the interaction of legged vehicles with different surfaces such as sand, mud and loose earth. Studies of the interaction of vehicle loading and foot design with surface conditions do not need a high degree of adaptability. Another example is the development of aids to stable locomotion such as balancing devices. This chapter describes such a simple vehicle. The next sections cover the methods used to reduce complexity: of these the most unusual is the steering geometry and mechanism.
-
2 The use of simulation in the off-line programming of robots
- + Show details - Hide details
-
p.
11
–28
(18)
The general requirements of a robot simulation system are discussed and the benefits of integrating such a system with a solid modeller are indicated. The status of a robot simulator integrated with the BUILD solid modelling system is examined. The application example cited is the Condition Number analysis for optimum positioning of a workpiece in a robot's workspace. The robot simulator is used to verify that no interference takes place between the robot and workpiece in the optimum position.
-
3 The practical problems involved in off-line programming a robot from a CAD system
- + Show details - Hide details
-
p.
29
–40
(12)
As part of a joint project between UMIST and Leyland Vehicles Limited under the Teaching Company Scheme, the feasibility of using a robot to automate the asssembly of components for commercial vehicles was investigated. The company were very keen to integrate the C.A.D. and C.A.M. aspects of the project. The envisaged system has many similarities to the system developed elsewhere for the manufacture of electrical looms, described by Gibbons. However, because of the low-volumes and variety of looms the production time lost with conventional teach-and-repeat methods would be significant. The recent availability of an off-line robot programming package for the company's C.A.D. system meant that both of these aspects could be tackled. The use of off-line programming from a C.A.D. system is a relatively new concept with associated high technical risk, and so a development robot-assembly cell was set up to demonstrate that the technique was practicable. Many problems were encountered but were overcome, and the project has been very successful in confirming the viability of automating this assembly process.
-
4 The application of rule based methods to inspection and quality control in a manufacturing process
- + Show details - Hide details
-
p.
41
–54
(14)
The introduction of computer control has made possible the automation of many manufacturing operations. Variation of components from batch to batch causes performance problems in many products. With the energy regulator it is often necessary for the Quality Assurance Department to extract samples from assembled batches before they undergo testing. These are then adjusted, tested and analysed to determine a particular setting angle for that batch. In this way the methods discussed in this chapter are already being applied in a cumbersome manual fashion to achieve the quality of the final product. This chapter therefore describes the automation of this technique to permit continuous adaptation and steady throughput.
-
5 Automatic location editing of assembly robot programs
- + Show details - Hide details
-
p.
55
–72
(18)
This chapter examines the programming task required by a robot workstation within a flexible assembly system. A system is described which optimises programming by use of off-line programming and automatic location editing. The system uses a robot equipped with two simple two state touch sensors which are manipulated to provide redundant data capable of accurately describing various types of 5 or 6 degree of freedom locations. Locations are determined by automatic search routines and edit algorithms, which enables automatic calibration of the sensors. The implications of the results are discussed and it is concluded that automatic location editing can increase both productivity and flexibility of assembly workstation.
-
6 Dynamic analysis of industrial robots using decentralised control via kinematics
- + Show details - Hide details
-
p.
73
–98
(26)
The majority of industrial robots used in most practical applications move at a relatively slow speed. This means that the dynamics involved in the motion are affected dominantly by the gravitational and inertial components, where the centrifugal and Coriolis components are negligible, under such a situation, if the precision of the tracking of any nominal or prescribed trajectory is not of major importance, but the accuracy at the terminal point is essential, the control of such robots may be performed adequately via kinematics, as shown by Vukobratovic and Stokic.with respect to this matter, it is necessary to have an insight on the dynamics of the robot,especially the contribution of gravitational and inertial components towards affecting the performance of the overall system.
-
7 Collision avoidance between robots operating in the same cell
- + Show details - Hide details
-
p.
99
–110
(12)
The article discusses the collision avoidance between robots operating in the same cell. The cell controller operates the cell by sending instructions to the individual (local) hardware and robot controllers, the latter as a sequence of subroutines. For multi-robot cells the Route Consultant is an additional requirement. Its function is to interpret the overall status of the cell and thence to advise the cell controller accordingly.
-
8 Flexible automated assembly systems
- + Show details - Hide details
-
p.
111
–120
(10)
This chapter describes the research work being carried out at Napier College with the aim of creating a pallet based Flexible Automated Assembly System capable of building a range of assemblies on demand without the need for human intervention.
-
9 Autonomous assembly devices and related control strategies
- + Show details - Hide details
-
p.
121
–128
(8)
This chapter will concentrate on the research work being carried out at the University of Wales Institute of Science and Technology (U.W.I.S.T), sponsored by the Science and Engineering Research Council, concerned with the development of intelligent robotic devices to enhance automatic assembly systems. Industrial robots have recently been introduced to the assembly environment with the aims of doing the work of several work stations. This results in a cheaper assembly system that is economically viable at lower production volumes and can be modified as product developments are introduced. The authors work on adaptable handling systems shows that relatively simple devices can be manufactured to accommodate misalignments between parts. By the use of appropriate control strategies chamfered pegs can be assembled whether or not initial contact occurs on the chamfer.
-
10 An aid to effective off-line programming of assembly robots
- + Show details - Hide details
-
p.
129
–138
(10)
A device has been successfully tested which can be used to obtain accurate insertion co-ordinates from off-line programming an assembly robot. In the form outlined it is only suitable for insertion operations and equivalent devices for handling (picking) operations would be more expensive and more difficult to develop. However, since insertion is far more critical than handling it could be expected that, particularly with good design of the picking location, nominal positioning of the gripper will be sufficient.
-
11 Robot force sensing using stochastic monitoring of the actuator torque
- + Show details - Hide details
-
p.
139
–156
(18)
This chapter discusses robot force sensing. The stochastic force sensing can be useful, inexpensive and straightforward technique for integrating force monitoring in a robot. More study is needed to transfer this technique to an efficient and universal force sensing methodology, suitable for all robot control applications.
-
12 Precise measurement of radial dimensions in automatic visual inspection and quality control-a new approach
- + Show details - Hide details
-
p.
157
–172
(16)
Automatic visual inspection of manufactured goods is commonplace in many parts of industry: an important aspect of inspection is checking that the sizes of products lie within predetermined limits. This chapter analyses how circular products may rapidly and conveniently be measured with high precision. A new approach is developed which is valuable when product sizes do not vary by more than a few percent.
-
13 Visual feedback control for orientating parts in an assembly robot cycle
- + Show details - Hide details
-
p.
173
–184
(12)
In order for an industrial robot to handle components correctly during an assembly process, the components are usually presented to the robot in a known orientation using some form of jigging. If the component cannot be orientated using jigging or simple sensory devices then the assembly process is usually performed by a human operator. In order to overcome the problem of component orientation a vision system can be interfaced to an industrial robot which can identify and calculate the position and orientation of the component. This chapter discusses the application and flexibility of such a robot vision system.
-
14 Automation and robotisation in welding-the UK scene
- + Show details - Hide details
-
p.
185
–198
(14)
The development of MIG/MAG processes made possible machine welding. Robots have allowed these machines to become more flexible, firstly because of their freedom to move the welding tool, and secondly because of the robot control system which has permitted interfacing with joint following and peripheral equipment. Although robots were first used with the resistance spot welding process, particularly in the automotive industry, this chapter will concentrate on arc welding developments. Comment will also be made on the application of robots to other welding processes and of related research and development activity. While the rate of application of welding robots within the United Kingdom has been slower than in much of the developed world, their range of application has been wide. There have also been a number of significant and leading innovations.
-
15 Practical industrial low cost vision for welding robots and automated welding machines
- + Show details - Hide details
-
p.
199
–210
(12)
The potential benefits of equipping arc wielding robots with vision to provide adaptive control for seam tracking have been widely accepted. A limited survey of industrial users' requirements suggested a more robust and cost effective solution was needed. This chapter describes continuing work at UMIST to build a practical industrial device to meet this requirement, based on earlier work using a single linescan, and avoiding the use of laser illumination .
-
16 A high-speed pattern recognition system for robotic applications
- + Show details - Hide details
-
p.
211
–220
(10)
With the large increase in small batch production and the need for greater productivity and reduced costs, automation is taking over. Dedicated automation, such as is used on large production lines, is unable to cope with quick product changes hence the use of robots is increasing. At the moment these reprogrammable assembly devices have little intelligence and little or no sensing capabilities. If robots are to expand into other production areas they will require complex and intelligent sensors. It can be seen that there is a very large potential market for vision within current robotic applications, vision would also open new areas for robotics.
-
17 A vision system for the identification of motor car headlamp reflectors for robotic assembly
- + Show details - Hide details
-
p.
221
–230
(10)
Imperial College and Lucas Research Centre have a collaborative research program whose aim is to investigate the feasibility of automating the assembly of motor car headlamps. It was decided that a Flexible Manufacturing System (FMS) is required which would not only identify and assemble various types of headlamps but also be easily reprogrammed to identify and assemble new or modified headlamps. This is an essential requirement since headlamps are cosmetic items with a limited product life cycle. The FMS would include independent Robot Cells executing independent tasks of the headlamp assembly (the insertion of fixing 'tulips' onto reflectors, the insertion of lamps, casing assembly and so on). A cheap, fast and flexible Vision System was required within six months to identify headlamp reflectors prior to assembly. This chapter will describe such a system for the purpose of 'tulip' insertions.
-
Back Matter
- + Show details - Hide details
-
p.
231
(1)