Robot communication methods.

If robots are to play a valuable role in the manufacturing environment then they must be able to communicate either with:

• Other robots, which may be part of the same system
• Other automation technologies
• Production planning and scheduling systems to receive or transmit data

Robot communication is key for collaboration, where each robot carries out specific tasks based on its programming. Through the co-ordination of activities, robots can work as part of a complete system, with workflows being optimised and efficiencies gained.

What is robot communication?

The level of interaction between the robot and the surrounding environment depends on the complexity of the task and configuration of the automated cell. As an example, an advanced robot might sit in the middle of a system in connection with a variety of simpler robots. The advanced robot might carry out complex tasks and prompt the others to carry out simpler activities at specific times. Such coordination can make for a far greater output than could be achieved by robots working in isolation.

A connected group of robots may be expected to work in the same way as a trained team of people, with tasks being allocated according to knowledge and skill levels. With no need for a robot that can perform every task, costs and complexity can be minimised. Efficiency may also be maintained at the highest level.

How does robot communication work?

Robotic systems might transmit signals and programmed information in the following ways:

Hardwiring

This will involve the connection of two or more robots via hardwired communication cables. It’s a reliable and robust method that has often been used for the connection of industrial devices.

Wi-Fi 

There is no need for hardwiring where robotics systems can communicate via Wi-Fi connections. This also allows for communication with other internet-enabled devices.

Bluetooth

Bluetooth radio waves are increasingly being used for the connection of robots. The robots can be paired for communication where such devices are in range.

5G

5G communication is also becoming an increasingly popular method for the connection of devices. There is the option of directly linking 5G with the Industrial Internet of Things (IIoT), which might also be referred to as Industry 4.0 and connected manufacturing.

Types of robot communication.

Binary or digital signals

Binary or digital signals are effectively simple on/off signals which function as inputs or outputs to either confirm that a part is present or to switch ancillary equipment on or off. These signals can also be sent in a group – as a binary coded decimal that can be exchanged with different machines.

Numerically controlled (CNC) robots have their functions determined and executed by a controller. In an automated manufacturing work cell, a supervisory controller (generally a programmable logic controller or PLC) acts as the cell’s main controller working with the controllers of a robot and a CNC of the cell.

A digital signal is not continuous and is used for a specific, once-only operation, such as a shut-off. Taking the example of rotational speed, voltage and seconds can be produced by an incremental encoder. Slots in the encoder allow light to pass through for the generation of pulses, each of which shows a degree of motor shaft rotation. The speed of rotation is given by the number of shaft rotations divided by elapsed time.

Analogue signals

Analogue inputs and outputs can be used by robots for the identification of value in the form of a voltage, which may then be converted into a number. Alternatively, they may send a voltage which is converted and used by an ancillary piece of equipment to set or change one or more parameters. 

Analogue signals are continuous and can be either an alternating current (AC) or a direct current (DC) signal. Analogue signals are representations of a physical quantity, such as the revolutions per minute of a motor, which can be measured by a tachometer.

Communication between a robot controller and an arc-welding power source is one example of the transfer of analogue signals. In this case, the signals may be used to adjust and set the operating voltage and current at a suitable level for the weld. There are many other uses of analogue signals, where there is a requirement for the robot to react or influence: for example, the operating parameters or speed of ancillary items.

Handshaking

Handshaking refers to the way two robots initiate communication. The messages are formed based on a recognised technical communication protocol for the combined performance of tasks.

For example, two robots can each use digital inputs and outputs to communicate with one another. In such a case the digital output for one robot will be connected to the digital input of the second robot and vice versa. The handshaking is handled as two background tasks in the robots’ main program to keep the two robots from colliding with one another.

Serial or parallel interfaces

Just as personal computers (PCs) can link to peripheral equipment (such as disk drives and printers) via standard parallel or serial ports, so too can robots.  Although often used for program development and storage, such connections can be made within a robot program for producing task reports. There may also be some interfacing with other technologies (such as machine vision systems) so that robots know where specific parts are located.

Networks

Automation became increasingly sophisticated, with a greater number of systems and devices being made available in the 1980s. The MAP (Manufacturing Automation Protocol) was also developed at this time, as a solution for communications that would otherwise have been prevented by incompatible communications standards.

Factors such as complexity and cost have meant that the MAP has fallen out of use. Ethernet connectivity, now a standard element of robotic systems, has become the most widely used communication method. Alternative forms of communication, including Fieldbus and Profibus, also remain in use - particularly for larger industrial automation systems. These enable real-time connection and control of networked field devices – sensors, actuators, motors, switches and drives – to name a few, within a manufacturing plant.

Specialist interfaces

Applications, such as arc welding, require several analogue and digital signals to control the welding power supply and filler wire feed drives.  These are often supplied by the robot vendors, complete with specialist instructions written in the robot programming language for application-specific control.

Advantages of robot communication.

Communication between robot technologies is a means of realising the many advantages of automation. 

Where multiple items of equipment are connected there will be the option of introducing line balancing. This is where the various pieces of equipment communicate and share information, with one part indicating that it’s starved or over-saturated with product due to an unplanned stoppage (this might also be caused by failure to keep up with the flow). The line PLC would either slow or accelerate some elements of the line, for continued work at a reflective rate instead of coming to a complete stop.

The other advantage of Connected Manufacturing is the potential for waste reduction. This may result from the balancing of lines around the slowest part of the process; any time critical parts of the process can be managed more closely. Alternatively, there may be the possibility of selecting a different component to be indexed to a different part of the product flow. 

Such possibilities are dependent on the industry, the process, and most importantly, the budget available for change. Avoid feeling overwhelmed as you enter the world of automation with advice from reputable integrators (such as those who are part of the BARA System Integrators Certification Scheme) to develop your specification. The end result will more closely match that needed for the optimisation of your production process.

Challenges of robot communication.

As with other aspects of robotic working, setting up robot communications requires detailed planning and careful implementation. Companies are best placed for success if they work in partnership with expert suppliers who can support them in the transition to robotic automation.

The choice of robot equipment is becoming larger and more complex, as are the technologies behind them. However, interfaces are generally becoming simpler, allowing operators to carry out programming and control procedures using intuitive systems which require less training.

The caveat is that the fixing of complex robotic system issues requires high levels of expertise, which is usually provided by the robotic equipment supplier. Support and maintenance is a critical consideration in choosing a robotics partner.

The costs of robot implementation can be high. Organisations need to leverage all the benefits available to achieve maximum efficiency. That means ensuring the proper set-up and management of robot communications.

Summing up

There are various ways that organisations embracing robotics and automation can improve their ways of working. Such methods are sure to be of benefit to all stakeholders, including owners, employees and customers. Robot communication is at the heart of successful implementation and needs to be a core consideration for system specifiers.