Simplifying robot and machine interaction
10 October 2016
Efficient industrial manufacturing relies on the interaction between machines and robots. Programming, control and error elimination for the two systems has, traditionally, been carried out separately. A situation which is changing.
Traditionally, robots and machines have been programmed and operated separately from one another via a PLC or robot control. While it is technically possible for them to interact it does involve a number of issues. The development of an established software interface for controlling robots by PLC – MotoLogix from Yaskawa – is said to have changed this, enabling direct integration without the need for specialised knowledge of the robot.
When using conventional methods operators have to be trained not just in international PLC standards but also need to possess skills in robot programming and control. Further, redundant programming procedures means that the source of failure is not always evident, making it difficult to eliminate errors quickly and easily. Traditional solutions usually attempt to integrate machine control systems into robot control.
Given that modern high capacity PLCs can be expanded on a modular basis, the approach is now the direct opposite – the robot is integrated directly into the machine via the PLC as one of many elements. Yaskawa, for example, offers a solution that sees its MotoLogix interface, developed in association with Rockwell, allowing Motoman robots to be programmed and controlled via the PLC.
Coordination of all axes
The MotoLogix interface allows coordination of all the axes of a production facility with the robot motion. It comprises a hardware unit and software for programming the robot via a Rockwell PLC. Platforms currently supported include Ethernet/IP, Powerlink and Profinet.
MotoLogix has a library of function blocks prepared in all language options, so operators are able to work directly via the library. Integration of robot control in the PLC means that bit sequences for servos are not needed and the robot control calculates motion kinematics to ensure high motion quality. Normally, the robot is incorporated into the production facility as a slave and integrated as an additional axis, so conveyor belt synchronisation is also possible.
The conveyor belt tracking system enables the manipulator to find objects on the conveyor belt even if they have shifted during conveyance, while sensors and cameras allow synchronised motions to be effected as part of complex procedure systems. Currently, this solution can be used to synchronise up to eight robots.
According to the conventional method of having robots and machines interact with each other, machines were programmed and controlled via the PLC and robot programming was carried out using a teach pendant. Here, the job structure and motion points are saved in the robot control system while a parallel operating structure and component administration has to be undertaken in the PLC. The jobs are then called up via the PLC by means of a bus with job creation and maintenance requiring expertise in operating robots, so special training had to be provided.
The solution results in full and direct robot control through the PLC, where movements are initiated and tracked, so there is no need for knowledge of robot operation. Path control itself is via the robot controller, ensuring that the benefits are retained, particular for motion precision and speed stability. Nothing else is required for the initial start-up.
The robot is connected and directly embedded in the PLC and the HM) via MotoLogix so all data is saved in the PLC without storage limit. Data can also easily be displayed graphically on the HMI. It is possible to have individual items displayed such as a company logo or application-specific processes.
MotoLogix allows all Yaskawa robots with a DX200 controller to be integrated into complex production systems in a simple, straightforward way. The robot is programmed and operated directly via the PLC. This also eliminates error sources, which have posed challenges in the past simply in terms of identification.
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