Setting up the new IO Link Communication Protocol in Industrial Applications

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Introduction

Future industrial automation will be scalable, integrated, and unrestricted.  The Industrial Internet of Things (IIoT) enables a new way to target and reduce variability, with smart factories using an increasing number of sensors, analytics, and networks to predict equipment performance and maintenance. Processes distinguished by variable elements (temperature, viscosity, and pressure) benefit from a larger population of deployed sensors and the insights synthesized from produced data. The ruggedly designed Brad IO-Link HarshIO modules are fit for smart connected sensors in an industrial manufacturing ecosystem. We will discuss how these modules help us to implement smart sensor solutions by considering their features, modular connectivity, hardware interface, IO-Link protocol, advantages, and finally practical usage scenarios in industrial applications.

Industrial Protocols

A few examples of industrial communication protocols are BACNet, CAN, CANopen, J1939, Modbus TCP, Modbus, EtherNet/IP, IO-Link DeviceNet, Ethernet, Profinet, Profibus, SNMP, and S7comm. The Ethernet offers a high-speed, deterministic, and low jitter solution easily implementable on existing Ethernet hardware. PROFINET with EtherCAT Ethernet/IP is also a trending Ethernet-based networking panacea. We will discuss a few Molex supported protocols in the following sections.

What is IO-Link ?

IO-Link is a new digital communication protocol defined in the international standard IEC 61131-9. It is used in automation technology. IO-Link is a serial, bi-directional, point-to-point connection for signal transmission and energy supply under any network, field, or backplane buses. The power supply range of an IO-Link system is 20V to 30V for a master and 18V to 30V for the device (sensor or actuator). The system supports three baud rates: 4,800, 38.4k, and 230.4k bauds over two communication modes, a standard I/O (SIO) and Single-Drop Communication Interface (SDCI).

The IO-Link specification distinguishes two types of ports for the IO-Link master: Port Class A (Type A) and Port Class B (Type B), as shown in the following pin configuration figure. In Type-A, IO-Link modules use an unshielded three-core cable (L+, C/Q, and L-) interface. The functions of pins 2 and 5 are not specified, but Pin 2 is usually assigned with an additional digital channel.

Figure 1: Pin assignment for Port Class A (left) and Port Class B (right). Image Source: io-link.com

In Type-B, the modules are connected using a shielded five-core cable. Type-B provides additional supply voltage and is suitable for connecting devices that have an increased power demand. One conductor is used for power supply to the actuators, and another is used as a separated, galvanically isolated reference potential.

a. IO-Link Protocol Operating Modes

The IO-Link communication protocol excludes definitions regarding the higher-level communication protocol. It is a robust communication system. The IO-Link ports of the master can be operated in the following modes:

• IO-Link: the port is used for IO-Link communication.

• DI: the port behaves like a digital input.

• DQ: the port acts like a digital output.

• Deactivated: this mode can be used for unused ports.

b. Data Types

Four basic data types are used in IO-Link communication:  Process data, Device Data, Value status, and Events. The process data type is cyclically transmitted. Value status data types are PortQualifier, which indicate whether the process data are valid or invalid. The device data type can be parameters, identification data, and diagnostic information. These can be written to the device (Write) and read from the device (Read). The events data type indicate error messages and warnings/maintenance data. When an event occurs, the device signals the presence of the event to the master.

c. Profiles Used for IO-Link

Device profiles are defined for IO-Link to standardize how the user program on the controller accesses the devices. They specify the data structure, data contents, and basic functionality. Device profiles are currently defined as below:

• Binary switching sensors

• Digital measuring sensors

• Devices with uniform system behavior

Typical Setup of IO-Link System

As shown in the figure, IO-Link sensors and actuators are connected to the IO-Link master or through an IO-Link Hub. These units are linked to the control unit / PLC via the communication bus. The protocol used here can be either EtherNet/IP, Profinet, Modbus, or any other industry-standard communication protocol. The IO-Link master will act like a gateway and collect the IO-Link sensor signals, then converting them into PLC compact protocol.

Figure 2: Integrated Smart Sensor Solution using IO-Link.  Image Source: Author

Advantages of IO-Link

The use of IO-Link sensors and actuators offers multiple benefits over digitally switching or analog sensors and actuators. The IO-Link technology uses serial communication, which allows for the transmission of parameterization and diagnostic data to and from the sensor or actuator. Digital communication leads to a reduction in system downtimes through predictive maintenance, and the parameters can be modified while the system is in operation. The usage of IO-Link decreases the number of different interfaces or connector plugs in the system. Modularity offers the scalability and flexibility to configure, modify, or expand machines and lines quickly. These connectors are designed and constructed to provide secure connections and protect against ingress and harsh environments.

Brad IO-Link Connectors

Figure 3: The Brad M12 cord setBrad M12 cord set for connecting with sensors

HarshIO modules accept standard threaded M8, M12, or Ultra-Lock M12 Connectors. Brad M12 connectors are designed to withstand harsh industrial and weather environments, with satisfactory quality that assures highly reliable connections for control elements in automated equipment. The Brad Ultra-Lock system is designed to ease a push-pull connector to IP67/IP68/IP69K rated sealed connections in industrial environments. The patented "push-to-lock" technology of this Push-Pull connector provides a safe, reliable connection for sensors, actuators, and other control devices.

Molex Offerings

Brad IO-Link solutions from Molex enable new generation industrial machine design that requires high availability, scalability, and the extensive use of diagnostics for preventive and corrective maintenance. Machine-mountable Brad HarshIO Modules support all significant industrial communications network PLC connections and protocols, including PROFIBUS-DP, DeviceNet, CANopen, Modbus TCP, EtherNet/IP, and PROFINET IO. These can be used in harsh environments where liquids, dust, or vibration may be present. Such robustness makes them equipped for multiple applications, including material handling and automated assembly. Molex supports Fieldbus and Ethernet network developments with products developed specifically for Ethernet, Ethernet IP, Profinet, and CIP Safety. We will discuss these Molex offering IO-Link modules.

a. Brad HarshIO ePN (PROFINET IO)

The PROFINET master module features eight M12 ports on each IO-Link master channel port and a configurable digital I/O channel. These modules provide a reliable solution for connecting industrial controllers to I/O devices in demanding duty environments in an IP67 rated housing. The integrated unmanaged 2-port Ethernet switch allows flexibility in the network topology to meet application needs. Brad HarshIO 600 modules are available in various combinations with 16x Inputs, 12x Inputs + 4x Outputs, 8x Inputs + 8x Outputs or 16x User Configurable I/O. It has an integrated web server and password-protected for IP configuration and module diagnostics.

Figure 4: Brad® PROFINET* IO-Link* HarshIO ModulesBrad® PROFINET* IO-Link* HarshIO Modules

b. IO-Link M12 Digital Hubs

Digital hubs are an attested solution for linking any compliant IO-Link master and digital sensors or actuators in harsh duty environments enclosed in an IP67 rated housing. IO-Link digital hubs include appropriate diagnostic features. The Digital hub is housed in an IP67-rated enclosure and offers protection against the ingress of dust and temporary water immersion. The digital hubs support up to 8 I/O, ports supporting three different types of fixed I/O configuration. The IO-Link digital hubs come in 3 versions, with 16x inputs, 12x inputs + 4x outputs and 12x inputs + 4x outputs grounded. Their Digital input and output are short circuit secured. The digital hubs comprise an IO-Link connector, which provides the IO-Link communication and the digital sensors' and actuators' power. IO-Link connector can be connected for PROFINET, and EtherNet/IP can be linked to the IO-Link master via 3, 4, or 5-wire cables.

Figure 5: IO-Link M12 Digital HubIO-Link M12 Digital Hub

c. HarshIO 600 eIP IP67 IO-Link Modules for EtherNet/IP 

Brad HarshIO Ethernet features a Built-in 2-port Ethernet switch, web-server capabilities, and a flexible IP address setup method allowing simple configuration and operation. The standard M12 connectors, from sensing devices or actuators, follow traditional industrial Fieldbus practices and plug directly into the I/O module. An environmentally sealed IP67 connection between the I/O module and the Ethernet network is created using the Brad Ultra-Lock connection system built into the Brad HarshIO module.

Figure 6: HarshIO Digital ModuleHarshIO Digital Module for EtherNet/IP, Classic 60mm

d. EtherNet/IP CIP Safety IP67 HarshIO 600

EtherNet/IP CIP Safety Brad HarshIO modules provide a reliable solution for monitoring safety input devices (interlock switches, emergency stops, light curtains, laser scanners) and control of safety output devices (relays, muting lamps, fail-safe motor starters) with industrial safety controllers in harsh duty environments enclosed in an IP67 rated housing. CIP (Common Industrial Protocol) defines objects and messages common to all protocols supported by ODVA. The EtherNet/IP CIP Safety HarshIO module mainly serves automotive manufacturers and machine builders looking for on-machine safety I/O connections to reduce cabinet space.

e. Brad HarshIO Digital Module for CANopen

IP67 Compact Block modules are robust CANopen stations for harsh environments, providing connectivity to sensors/actuators through a CANopen network. The compact design, with M8 connectors, allows space-saving for direct machine mount application. Multiple combinations are possible with such a format: - 8 Inputs - 8 Outputs - 4 Inputs / 4 Outputs - 6 Inputs / 2 Outputs. - 8 Universal and user-configurable Input/output channels.  For each combination, the input format can be specified as NPN or PNP.

Figure 7: Brad IO-Link CANopen module Image Source: Molex

Application Information

a. Robotics Application Using Profinet Module

The HarshIO ePN modules, designed to bolster the new Fast Start-Up (FSU) feature, permit the power-up, connect to PROFINET IO-Controller, and begin I/O cyclic data exchange under 500 msec. This FSU feature generally finds robotics applications where a few I/O devices are mounted on a tool changer. This robot disconnects and reconnects on the fly with a new tool without pausing the manufacturing process. The FSU device Ethernet switch ports are configured with fixed speed up to 100Mbps and full-duplex enabled. The following diagram illustrates a typical robotics application using an in-cabinet PLC controlling HarshIO ePN modules mounted all over this industrial system.

Figure 8: Robotics application using Profinet module. Image Source: Molex

b. Distinct Grounding Wiring for Safety Relays

The HarshIO power connector incorporates a distinct grounding galvanic isolation between the Output and Input/logic ground. This detail allows the module to be powered with two separate power supplies generally used in safety applications. A system designer, in a typical automation application, uses safety relays.  These relays periodically conduct the pulse test to detect a short circuit, earth fault, or a ground fault. The safety function triggers if an error is detected, thereby avoiding unwanted and dangerous plant condition scenarios.

Figure 9: Architecture using two distinct grounds with safety relay Image Source: Molex