Cambridge University's Speech, Vision & Robotics group choose Mitsubishi robots

Citation

(1999), "Cambridge University's Speech, Vision & Robotics group choose Mitsubishi robots", Industrial Robot, Vol. 26 No. 6. https://doi.org/10.1108/ir.1999.04926faf.007

Cambridge University's Speech, Vision & Robotics group choose Mitsubishi robots

Cambridge University's Speech, Vision & Robotics group choose Mitsubishi robots

Keywords: Robotics, Mitsubishi

A world leading project to expand the horizons of robot use in conjunction with vision systems is being developed by Cambridge University's Speech, Vision & Robotics group (SVR), part of the university's Information Engineering Department. Research Associate Dr Tom Drummond is leading the field of telerobotics with a system built around a standard Mitsubishi RV-E2 six-axis robot, a miniature CCD video camera and a UNIX computer workstation. This enables a teaching process whereby an industrial robot can attain accurate positioning relative to a target workpiece or operating environment regardless of the orientation of the workpiece, or indeed the start position of the robot.

As part of the multinational EC-funded ESPRIT IV Reactive LTR programme, the University is an academic partner in a three-year technology transfer project together with end user partner, the Danish shipbuilder OSS, based in Odense.

The future of shipbuilding in Europe hinges on the realisation of substantial productivity improvements, which can be achieved by a relative doubling of the number of metres welded per year. Robot-controlled welding is currently used to fabricate interior steelwork and a ship's superstructure on a massive scale, often in areas with difficult access and unpleasant environments. A typical rig involves several gantries used for positioning multiple robots in a workspace measuring perhaps 30 x 20 x 10 metres. Achieving the target accuracy of 1mm with parts that may be inaccurately positioned has traditionally been a time-consuming problem. The introduction of telerobotics brings state-of-the-art technology to bear on the problem robots have working with complex geometries, randomly orientated in a large workspace.

The Cambridge University system enables robot positioning to an accuracy of 0.1mm, close to the 0.04mm best achievable by the Mitsubishi RV-E2 robot (see Plate 7). According to Dr Drummond, "Nothing else in the price range comes close to this kind of performance. We have purchased the Mitsubishi robot for a five-year programme to develop robot technology and vision systems". It is no surprise, therefore, that its sister product, the Mitsubishi RV-M1, is the bestselling robot in the European education sector. The accuracy required by leading European developers of in-car ergonomics is already being evaluated and implemented using Mitsubishi robots to test fascia switchgear for "touch and feel".

Plate 7Cambridge University's Speech, Vision & Robotics group have chosen a Mitsubishi RV-E2 six-axis robot for a research project into robot controlled welding in the shipbuilding industry

The system uses specially written software which maps edge recognition from a video image of the workpiece to a geometric model of the workpiece held in the computer. This is achieved without any special lighting conditions and does not require the robot to be calibrated.

Earlier work by the SVR group used a stereo pair of video cameras to provide spatial coordinates from which a robot could be "taught" its position relative to its surroundings, effectively becoming self-calibrating. The vision system has been further developed using a stereo pair of cameras so that complex shapes can be evaluated on-line to determine automatically the optimum geometric grasping point for the robot. Here, image recognition was used to enable the human hand to be used to literally point to the position needing to be addressed by the robot. This technology gives a coarse positioning accuracy of about 1cm over 1m.

Dr Drummond's work continues this programme of human/robot interactive research, focusing particularly on hand/eye coordination systems for robot positioning. Pioneering work started in 1993 by Dr Roberto Cipolla, Reader in Information Engineering at Cambridge, resulted in his department winning a prize in the annual competition run by the British Robot Association, as it then was, for the first uncalibrated robot/vision system in Europe. The project also featured on BBC TV's Newsround programme.

The SVR group now has commercial applications clearly in its sights, aiming for robust, fast, accurate solutions which can operate from simple human teaching inputs. The robustness of the system makes it ideal for dynamic manufacturing environments with multiple handling and frequent line changes. Decalibration is not a problem if the robot arm is knocked, and the camera lens can be changed online without affecting system operation or accuracy. For hazardous areas such as nuclear or chemical plants, the concept of "augmented reality" using the vision system has great potential. The accuracy required by leading European developers of in-car ergonomics is already being evaluated and implemented using Mitsubishi robots to test fascia switchgear for "touch and feel".

The Cambridge team is also working to improve the speed and reaction times of the communications link between the robot and the computer which "models" the workpiece. This will enable the robot to track more quickly to its handling or operating position. The power of the vision system is already proved, and off-the-shelf software tools are available to speed up recognition of, say, a variety of components appearing on a production line, or plates and beams in a metal fabrication. An example would be through optical character recognition (OCR) of a part number by computer warping the image of a randomly orientated tag or label on the part.

Mitsubishi has provided the SVR group with an ARCnet card to speed up the number of robot commands from four per second to around 35 per second. Further developments will deliver a higher command frequency to enable the robot to address moving targets.

The vision system is capable of providing games quality image rendering on a standard UNIX workstation, with a communications speed of 200Mb/s asynchronously read by the CPU. This translates to about 300,000 pixels per second.

Mitsubishi Electric Europe, through its Automation Systems business, provides automation and information systems to manufacturing and process industries. A part of the $36 billion Mitsubishi Electric Corporation, and one of the largest players in the industrial automation market, the business unit has European sales of $200M.

In the UK, automation systems solutions are delivered through a network of key distributors and Systems Integration Partners, selected, trained and closely monitored by Mitsubishi. Market leading products include FX small PLCs, A Series modular PLCs, AC Drives, Servo Positioning Systems and Q Series Process Control Systems. A comprehensive array of supervisory and control software, industrial Human Machine Interfaces and fast mini industrial robots completes the range.

Contact Mitsubishi Electric Ltd, Industrial Automation Systems Division UK, Travellers Lane, Hatfield, Herts AL10 8XB. Tel: +44 (0)1707 276100; Fax: +44 (0)1707 278555.