5 basic things robotics engineer should know about industrial robots
From this article you will find out:
1.??????Industrial robot - what is it and what does it consist of?
2.??????A robotic workstation with an industrial robot - what is it and how is it built?
3.??????Robotized workstation
4.??????Robotized workstation - how to control the application?
5.??????How is an industrial robot programmed?
1. Industrial robot - what is it and what does it consist of?
1.1. Industrial robot - definition
The PN-EN ISO 8373: 20011 standard presents the following definition of an industrial robot:
"... A manipulating industrial robot is an automatically controlled, programmed, multi-tasking machine with many degrees of freedom, which can handle and transport workpieces, it can be stationary or mobile for important industrial applications."
The standard also presents the basic parameters of industrial robots:
·???????the number of controlled axes, usually, depending on the robot, from 2 to 7; this parameter determines the degrees of freedom, which translate into the degree of complexity of the activities that the robot is able to perform; each axis has a specific range of angular movements,
·???????payload, i.e. the maximum weight that can be lifted or moved by an industrial robot to another place,
·???????range, defined as the radius of the area within which the robot is able to operate,
·???????speed of movement, which determines the maximum speed at which the robot can move each axis; this parameter is defined in rad / s for rotational axes or in mm / s for linear axes,
·???????accuracy and repeatability which determine the precision of the robot's movement.
1.2 Industrial robot - what does it consist of?
Industrial robots consist of 3 basic elements:
??manipulator - the executive part of an industrial robot
Depending on the version, the manipulators have a different number of movable axes (2-7) and different payloads (up to 2300 kg).
There are different types of manipulators depending on the application: conventional manipulators and manipulators with hollow gears - often, welding robot manipulators have a type of structure that allows cables to be put inside the robot arm, e.g. welding cables or additional pneumatic or electric bundles.
??controller - the control unit of an industrial robot
The robot manipulator is the executive part, and the controller is the control unit. The industrial robot controller
In addition - from the point of view of automation and robotics - the communication capabilities of the controller are important - these units usually support most protocols such as Ethernet IP, Profinet, Profibus, etc.
Interesting fact: electronic systems are getting smaller and smaller, so if we compare decades-old controllers with current solutions, it turns out that they are several times smaller. Sometimes the controllers are placed in the manipulator arms.
??Teach pendant
Teach pendant allows you to implement the robot’s movements in individual axes or systems, but also to view the robot’s working status – communication status, inputs / outputs.
A teach pendant usually has safety buttons, i.e. "deadmen" with which the robot can be started in manual mode. It allows you to program the robot in the selected language and control the program being executed - stopping, starting, etc.
Industrial robots do not have to have and sometimes do not use a teach pendant - the same functions can be performed by robot software.
The robot software has a wide variety of uses. Thanks to the robot software, the user communicates with the controller, reads its parameters, saves programs, functions or points. It allows you to change the configuration and programming of the robot in the language text. Additional robot software options allow you to control and view the real-time status of the signals.
2. A robotic station with an industrial robot - what is it and how is it built?
A robotic station is a much broader concept, because in addition to the industrial robot, it also includes other accessories and elements - the so-called peripherals. On the example of a palletizing station, let’s have a look into its components.
2.1. Gripper for an industrial robot
In this case, the robot part that allows you to manipulate the workpiece - to move, hold and put it away - is the pneumatic-mechanical gripper, which with the help of clamps is able to pick up boxes and put them on a pallet in a selected place.
The robot gripper carries out the transfer and transport of carton spacers, which can be placed between the layers of boxes. Additionally, it is equipped with mechanical clamps that grab the pallet and move it to the selected point of the station.
The robot arm also often contains pneumatic lines and digital signals that are put out at the height of 3/4 of the axis - which allows the robot's internal wire harness to be used to control it.
2.2. Safety system
Each robotic workstation has various parts of a safety system. When delivering workstations within the European Union, the manufacturer should attach a document confirming compliance with generally applicable standards. These requirements strictly define the rules that should be met by the parts of the safety system used.
The examples of elements of the safety system:
-????????safety fence - the robot's work area is separated by full or mesh panels, which are selected on the basis of a previously conducted risk assessment,
-????????light curtains mounted on the columns, which in case of human interruption into the workstation during the robot cycle, will stop the robot's movement in an emergency mode.
-????????the main entrance to the industrial robot station is monitored with a scanner, which has appropriately separated zones, allowing, for example, the passage of a mobile robot while the station is working.
-????????robot axis monitoring system - during the work of the station, such a system can independently control and check in what space the robot is working at a given moment.
-????????E-STOP safety buttons - such buttons are inside and outside the station, on the teach pendant and the robot controller - they allow for an emergency stop of the station.
-????????safety systems communicate with each other through the safety controller, which supports superior control over the safety elements built into the station.
Thanks to these features, you can dynamically control and monitor the zones in which the robot moves. In a situation when the industrial robot crosses the safety zone, the station will be stopped in an emergency mode - then it will be necessary to manually move the robot from outside of the safety zone.
2.3. Intralogistics systems and robotic station control system
In order to properly implement the palletization process, light and heavy transporters are used. They are responsible for transporting boxes and pallets in the presented application. They are controlled by inverters.
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The control over the entire application is supported by the PLC controller which communicates with the robot, industrial computer, mobile robot and inverters. All drive and control components are built into the electrical cabinet.
The HMI application is displayed on an industrial computer. Communication between the PLC controller and the MiR mobile robot takes place wirelessly using modern 5G technology.
3. Robotized workstation - how such a system is programmed?
Each part of the robotic station should be programmed separately and each of them has its own dedicated software that enables the implementation of selected functions.
This is done via driver specific utility software. The logic of the program itself is implemented with the help of structured text - this allows you to run individual sequences that perform palletization application.
At the given moment, inverters are started, a mobile robot with spacers is called and you can start the robot program. Additionally, the PLC reads data from sensors that control the proper operation of the application.
3.2. Programming of an industrial robot
The configuration and programming of an industrial robot can be done in several ways - the logical part itself was programmed using the robot software, while the motion programs were created partly on a teach pendant and partly in software that allows you to generate a diagram of the pattern of cartons on a pallet, which is installed on the industrial computer.
The program itself is sent to the industrial robot along with the point cloud - the robot knows precisely when it should reach which point and under which conditions. -> Read more in point 5.
3.3. Programming of a mobile robot
The mobile robot is programmed in a web browser that can be run on smartphones, tablets or computers.
We teach the mobile robot the path to be followed, saving it as a mission and in the next stage, thanks to communication, we can call the robot at the right moment thanks to the PLC program.
The most important aspect is the communication of the entire system - in this case it is implemented in several protocols: Ethernet IP, EtherCAT and TCP IP. It is set up between the PLC controller and individual devices, communicating in their own protocols.
The future of Industry 4.0 will allow for the standardization of communication and programming.
4. Robotized station - how to control the application?
The robotic station is equipped in an HMI panel. The screens used for control are displayed via a web browser - thanks to this feature, you can run this application on mobile devices.
By adding 5G wireless communication, we can access it from basically any device.
The operator starts the application by the Start button. If the workstation is stopped in the middle of operation, its work may be resumed.
In addition, you can also view the status of individual devices, where the information collected from robots and sensors is displayed - it also allows for precise diagnostics in the event of a failure of the station.
Screen for diagnostics of the status of devices included in the robotic station, Source: ASTOR
In the case of the industrial robot itself, in emergency situations, after switching to the learning mode, it is possible to move the robot manually with a teach pendant, by activating the drives and moving the robot using the appropriate buttons.
When an error occurs, the PLC will inform the user about the error code via HMI and suggest what could help to solve the problem.
5. How is an industrial robot programmed?
There are several options for programming industrial robots.
5.1. Programming of an industrial robot - block language
The first and the most widely used is block language. The idea is to reach a selected point in space, for which number of parameters are defined, e.g. waiting for selected inputs or switching on selected outputs.
For example, in the case of a welding robot, we provide the job number that the source should load before starting the whole process. After these parameters are defined, the path is saved. Of course, you can redefine individual steps at any time by overfitting positions or motion parameters such as speed or accuracy.
5.2. Programming of an industrial robot - text language
The second form of programming an industrial robot is text language, which allows you to prepare a logic or motion program on a computer and then upload it to the robot and teach the position.
This form can be applied to motion programs, but also to parallel threads that perform logical operations. We can create extensive functions using popular commands and structures, such as: IF ELSE, FOR, WHILE loops or GOTO jump instructions.
In the robot motion program, you can also use conditional statements, loops to optimize the code.
In addition, both languages can be used interchangeably when programming the RPM (Robot Program Motion) - partly in block language, partly in text language.
When it comes to teaching points, you can do it by approaching the selected position and saving it, or perform a previously written program with a teach pendant and save the positions for individual steps.
Another popular form of programming the robot is the dedicated CAD / CAM software, where a digital twin is created that can map the actual robotic station.
Movement trajectories are prepared in a computer program, which is later generated as a ready program that can be downloaded directly to the robot controller.
If the robotic station is well calibrated, such a program can be run without position corrections. In other cases, solutions that will support real-time trajectory correction can be used.
Would you like to know more? Ask the author in a comment and make an appointment at the ASTOR Robotics Center.
Sources:
Author:
Kamil Majcher
Robotic solutions development leader
ASTOR Robotics Center
Kawasaki robots welding equipment and Astorino robot Product Manager
2 年Kamil Majcher thank you for this article ?? we are waiting for next ones!