Goodbye to Complicated Operations: Achieving PLC “Human-Machine Dialogue” with Voice Commands

PLC Voice Application

The PLC voice application combines the real-time control capabilities of PLCs with the convenient interaction capabilities of voice, achieving “human-machine dialogue” for industrial control and information exchange.

The core principle is: through a voice interaction terminal (integrating a microphone, speaker, voice recognition, and synthesis module), personnel’s voice commands are converted into digital signals that the PLC can understand (such as Modbus/TCP, OPC UA, Ethernet/IP, etc.), which the PLC then executes according to the corresponding control logic; at the same time, alarms and status data generated by the PLC can also be converted into voice announcements to alert on-site personnel.

01#

Principle of Operation System

A complete PLC voice application system typically includes the following components:

1. Voice Acquisition Terminal: Microphone, headset, or industrial-grade voice terminal for capturing the operator’s voice commands.

2. Voice Processing Unit:

   Voice Recognition (ASR): Converts the captured voice commands into text information.

   Semantic Understanding (NLU): Understands the intent of the text information, for example, the intent of “start the conveyor belt” is to “execute the start operation,” with the object being “conveyor belt.”

3. Communication Interface: Sends the understood commands to the PLC via protocols (such as Modbus TCP/IP, OPC UA, Ethernet/IP, MQTT, etc.).

4. PLC (Control Core): Receives commands and executes the preset control logic (such as energizing a coil, starting a function block), controlling the actions of on-site equipment.

5. Feedback Loop:

   The PLC sends back device status, alarm information, and other data.

   The Text-to-Speech (TTS) unit converts this data into voice.

   The speaker or headset announces it, completing an interaction loop.

02#

Main Application Areas and Scenarios

Exhibition Operation and Control

• Hands-Free Operation: In scenarios where the presenter’s hands are occupied (such as holding materials) or it is inconvenient to directly operate equipment, voice commands can control exhibition devices and content.

Scenario: A presenter in the exhibition can say “switch to the next screen” or “dim the lights” without interrupting the conversation or putting down items to touch the screen or remote control.

• Device Debugging and Maintenance: Maintenance personnel can query device status and execute test procedures via voice.

Scenario: A maintenance engineer can say “check motor A current,” and the system responds with the current value; or say “execute pump self-test program,” and the PLC immediately starts the preset diagnostic process.

Quality Inspection and Data Entry

• Quickly Record Defects: Quality inspectors can quickly record defect types through voice during visual inspections of products.

Scenario: An inspector finds a scratch and directly says “record, scratch, location B side,” and the system automatically logs the time and defect information into the MES (Manufacturing Execution System) database, associating it with the current production batch controlled by the PLC.

• Paperless Inspection: Inspectors check equipment along a route and report operational status and readings via voice.

Scenario: An inspector approaches a tank and says “Tank T101, level normal, pressure normal,” and all information is automatically recorded and generates an electronic report.

Warehousing and Logistics

• Intelligent Picking and Sorting: This is the classic “voice picking” system. Pickers receive voice commands through headsets and confirm operations via microphone.

Scenario: The system announces: “Please go to shelf 12 in area A, pick 3 pieces of product X.” After completing, the picker says “done” or scans the barcode and says “confirm,” and the PLC immediately updates the inventory information and indicates the next task. This greatly improves efficiency and accuracy.

Safety and Alarms

• Proactive Voice Alarms: When the PLC detects equipment anomalies (such as high temperature, low pressure), in addition to displaying a red alarm on the HMI, it can also broadcast voice announcements through the workshop or specific workstation speakers.

Scenario: The system immediately announces: “Warning! The temperature of the stamping machine on production line one exceeds the limit, please handle it immediately!” This is more attention-grabbing than visual alarms, especially in noisy or visually restricted environments.

• Emergency Shutdown and Safety Confirmation: In specific safety processes, emergency operations or safety confirmations can be executed through predefined voice commands (which may require a password).

Scenario: Before entering a hazardous area, personnel say “safety confirmation, enter area A,” and the PLC must receive this signal before unlocking the safety door or starting specific equipment.

Personnel Training and Guidance

• Interactive Operation Guidance: Provides step-by-step voice guidance for new employees.

Scenario: At a complex equipment workstation, the system can guide newcomers: “Step one, please turn on the main power switch. After completing, please say ‘done.'” After the employee operates and says “done,” the system proceeds to the next step of guidance. This reduces training costs and operational error rates.

03#

Application Advantages

1. Improved Efficiency: Frees hands and eyes, reducing the time operators spend switching between HMIs, paper documents, and tools, significantly improving operational economy.

2. Reduced Error Rate: Voice interaction and confirmation reduce errors that may arise from manual data entry, particularly effective in picking and quality inspection areas.

3. Enhanced Safety: Real-time, proactive voice alarms can respond more quickly to dangerous situations; hands-free operation also allows employees to focus more on current tasks and the environment.

4. Achieving Paperless Operations: All information exchanged through voice interactions is directly entered into the database, facilitating traceability, analysis, and optimization.

5. Improved Human-Machine Interaction: Makes cold, complex industrial control systems more intuitive and user-friendly, lowering the operational threshold.

04#

Challenges and Considerations

1. Environmental Noise: Industrial sites are often very noisy, posing a significant challenge to the accuracy of voice recognition. High-quality noise-canceling microphones and voice recognition algorithms optimized for specific environments are needed.

2. Accents and Dialects: Different operators may have different accents, and the system needs to have good adaptability or targeted training.

3. Security Considerations: It must be ensured that voice commands cannot be accidentally triggered or maliciously mimicked, leading to erroneous device actions. Typically, multiple security mechanisms are required, such as keyword wake-up, specific command sets, and user authentication (voiceprint recognition).

4. System Integration: A stable and reliable communication link must be established between the PLC program, voice interaction terminal, and enterprise information systems (such as MES, ERP).

5. Cost: Deploying a reliable industrial-grade voice system, including hardware, software, and integration services, requires a relatively high initial investment.

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