Special Focus : Robotics
production environments; even during the movement of the robot arm, the robots react to changes in their environment and adapt their trajectory to suit. Cleverly, the self-positioning of the robot and the pinpointing of other moving objects within the workcell are achieved without the use of an image processing system. Moreover, the sensor-guided real-time control does not require elaborate programming. A key element of this flexible handling technology for industrial automation is the VRFloor (Virtual Reality Floor) positioning system developed by Robotics Technology Leaders. This utilises passive markers with a constant identity, sensors for registering the marking points, and a control computer for analysing the information. The markers are fitted beneath the floor, and an air cushion provides for smooth motion of the robot both within the workcell and between production stations. Sensors are fixed on the base of the robot and to other
moving objects in the working area such as workpiece carriers. With this set-up it is no longer necessary to align and position workpieces precisely when they are fed into the workcell. Dr Stefan Riesner, the managing director of Robotics
Technology Leaders in Munich, comments: “To be able to make robots and manufacturing stations so flexible, a real- time controller is indispensable.” The fast interchange of data between sensors and controller puts the robot in a position to react directly to changes in the work area and to determine its trajectory during movement on the basis of current sensor values. A computer calculates the movement information from the signals and transfers the position data to the robot controller, typically within one to ten milliseconds. For a 15 cm curved motion of the robot arm, which takes place in a period of three seconds, for example, 1500 positions must be transferred to the robot controller within a cycle time of two milliseconds.
Riesner concludes: “The reliable self-positioning of the mobile robot dispenses with the need for the often highly time- consuming and expensive programming, which frequently makes it unprofitable to use stationary industrial robots, particularly for small batch sizes, high numbers of variants and quick product changes.”
Biomechatronics
Aside from the developments in industrial robots outlined above, it is worth mentioning the project that Festo unveiled at the 2010 Hanover Fair. The Bionic Handling Assistant is not a saleable product, but Festo’s demonstration of a design concept to stimulate dialogue with customers, suppliers and partners. Inspiration for this concept came from elephants’ trunks, and the result is said to be a flexible and safe means of moving objects from one position to another. As well as a flexible arm, the Bionic Handling Assistant has a ‘wrist’ axis with a ball joint, and a gripper with adaptive fingers (Fig. 4). In the event of a collision with an object - including a
human - the Bionic Handling Assistant yields immediately, without modifying its desired overall dynamic behaviour, and then it resumes its operation when the obstruction is removed. Unlike heavy industrial robots, the Bionic Handling Assistant is said to be characterised by an excellent mass-to-payload ratio, provides smooth operating motion with more degrees of freedom, and makes very efficient use of resources. Nobody would suggest that robots are perfect for every
manufacturing operation, as there will always be some for which dedicated special-purpose automation systems are more appropriate, and others for which manual assembly is better suited. However, having made workers redundant during the recession, and faced with competition from low-wage economies, many manufacturers are taking a fresh look at how robotics might help them to meet rising demand. l
Fig. 4. Festo’s Bionic Handling Assistant is a pneumatically actuated ‘elephants’ trunk’ with sufficient compliance that it can be used safely alongside people.
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