Modular joint advances robotics
The need for UK industry to increase the number and dispersal of its automation and robotics systems is well-documented. For some years, voices from government and industry have called for greater adoption of automation equipment with a view to improving productivity.
However, such calls also require simple, lightweight and cost-effective robotic systems to be available. This is a need igus believes it may have helped to meet with its development of strong, lightweight robotic joints integrated these with a central drive system.
Called robolink, the system is a multi-axis joint for humanoid robots and lightweight automation applications. A completely modular system, robolink combines enormous design freedom with simplicity and is particularly well-suited where mass, cost and complexity are to be kept as low as possible.
The initial concept came about during the company's involvement as sponsor to teams competing in the Robot football World Cup (RoboCup) from 2006-2008. RoboCup attracts teams of engineers and computer scientists from around the globe, where they pit their wits against each other on the football-field of robotics and artificial intelligence. igus' team of engineers set about creating a robotic joint design with good transferable torque characteristics between the articulated joint and rod, low cable friction and optional integrated magnetic sensors to measure and transfer the position of the articulated joints.
Prior to launch, several igus beta-testers were provided with robolink prototypes for use in trial applications ranging from maritime robots for use with underwater vehicles to mobile robots on the ground, used for handling contaminated or explosive materials. Other examples include humanoid robots, camera guidance equipment and systems for facilitating interaction between man and machine. Further trials were carried out in the medical industry, as well as in the field of animatronics.
At the heart of the robolink modular system are the lightweight, maintenance and corrosion-free joints with tribologically optimised plastic bearings that are driven via cables and can rotate and swivel freely. To articulate the multi-axis joints, igus has developed flexible Bowden cables with high-performance polymer jackets that combine low friction values with a long service life. The cables have extremely small bending radii, making highly flexible movements possible and are suitable wherever frequent relative movements take place.
The robolink's core consists of lightweight plastic joints that are controlled via cable pulls that transfer tensile forces — similar to how tendons function in human muscle actuation. At the same time, cable sheaths hold steady while the inner cables move — similar to the way a bicycle's brake cable operates. Cable pulls run through the joints and arm tubes, from one joint to the next, with just two cable loops necessary to enable each joint to rotate and swivel freely.
The robolink accessories also include mounting plates, angular encoders, various drive wheels and pulleys. Also, the supplied arm tubes can be made of aluminium (the standard), glass fibre or carbon fibre reinforced plastics to save weight and decrease operating power consumption.
Electro-mechanically, igus has developed space-saving drive units, available in different performance classes, with four or five drive motors provided in a housing. In addition, the drive wheel can be attached to a wide range of different motor or gear shafts and then connected quickly and easily to the wear-resistant cables. Tensioning of the cables can also be achieved simply using a split drive wheel with a torsioning tool. Simple control software to programme and store all the movements of a four-axis jointed arm intuitively is in early development.
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