Micro Vision system closes loop on Motion Control. Pelican’s Mike Sharp explains how the integration of several products help solve a welding problem.
This type of digital input/output solution is fine for many applications, however, there are more and more scenarios where actual data values are required, in order to interface with other control devices. Hence, methods of communication have to be utilised that are able to convey the available complex output from the vision system to the required control equipment.
The Task and Issues:
To accurately weld two components together to form one precise assembly.
Under normal circumstances it is necessary to datum all components mechanically, prior to any weld cycle being attempted. This has required the design and manufacture of complicated and expensive tooling. Such tooling often limits the flexibility of each machine, making that machine dedicated to a small range of components.
Both components to be welded can move in the X-axis only, causing the welding process to be inaccurate and the welding torch arm having to be set by an operator for every cycle. In order to automate the process the torch is required to modify its position according to each specific weld cycle. Moving the torch a short distance accurately can easily be done by utilising a cost effective, pulse train Servo system. However, this system requires positional feedback in order to close the loop between the components to be welded and the servo controlled torch arm.
The above application was solved by integrating Omron’s F150-2 Machine Vision System with a Pulse Train Servo System. The Vision System is used to measure the distance between the two components, within three selected search regions (as shown in the diagram), this task is made simple with the use of the Grey edge detection function and easy set-up programming. Once the function has been initiated, many different conclusion values can be obtained. This particular application requires the two components to be identified and located accurately. A maximum/minimum distance between the two for OK (pass) and NG (fail) was programmed. This can be set-up as a digital output, within the user set measurement area position can be calculated with relation to the fixed camera, which is transmitted serially. Once the data has been received by the PLC it is necessary to change the values into a format that can be loaded into a position control unit. This gives a modified, precise position for the welding torch arm, achieved by the servo-controlled motor before the weld cycle commences, thus creating a fully automated machine cycle with a high accuracy weld.
This opens up a host of other such applications that can be resolved quite easily given the flexibility and serial communication to other control equipment.
Our extensive experience has allowed us to create a fully configurable servo control system and control profile with a multi axis motion controller, replacing an original mechanical CAM system. This has greatly enhanced setup time and cycle time nearly threefold.
Programming creates a sequence of instructions which are able to carry out tasks and calculations which were once worked out manually. Pelican’s industrial involvement with programming predominately sees us program with a state of the art Ladder based software, such as Omron’s SYSMAC Studio. However Pelican’s wealth of programming experience has seen our employees program in a variety of languages.
Pelican are experienced with Omrons latest control software Sysmac studio, which is software used for programming NJ-series controllers. Omron’s NJ-series controllers mark the integration of programmable logic controllers and motion controllers -with Sysmac Studio at at the heart of their operation. Pelican are always proud to stay up to date with the latest technology, and already have a firm grasp of Sysmac Studio – in fact it has already been implemented in a number of our systems. Sysmac studio has enabled complex motion control to be written in a ladder based language as opposed to traditional structured text.
Pelican have also gained a wealth of experience with structured text through their use of Trio’s Motion Perfect software. Trio are renowned for their motion controllers, for which Pelican have twenty years of experience programming. Pelican are specialists in motion control with projects spanning from simple point to point applications to complex interpolated motion control. Our motion control programmes have tackled difficult problems regarding CAM profile generation and flying shears – which have been primarily developed using structured text.