Siemens S7-200 “Servo Control” with Mitsubishi MR-J4-A: A Comprehensive Tutorial

Introduction

The Mitsubishi MR-J4-A Servo Motor is renowned globally for its superior quality and durability, making it one of the most widely used servo motors in industrial automation. This tutorial, written by FAIZAL AFZAL, will guide you through the process of controlling the Mitsubishi MR-J4-A Servo Motor using the Siemens S7-200 PLC. This step-by-step guide aims to make the process straightforward, even for those who are new to servo motor control.

Step 1: Wiring Diagram for Siemens S7-200 & Mitsubishi MR-J4-A Servo

1.1 Overview of the Wiring

To control the Mitsubishi MR-J4-A Servo Motor with a Siemens S7-200 PLC, you must first establish the correct wiring connections. The Siemens S7-200 PLC model used in this tutorial is the DC/DC/DC type, which supports high-speed pulse generation necessary for servo control.

The wiring diagram between the Siemens S7-200 PLC and the Mitsubishi MR-J4-A Servo Motor. This diagram clearly illustrate the connections for power supply, pulse signals, direction signals, and any additional control lines.

1.2 Detailed Wiring Instructions

• Power Supply Connections: Ensure that both the Siemens S7-200 PLC and the Mitsubishi MR-J4-A Servo Motor are connected to their respective power supplies. The PLC typically operates on a 24V DC supply, while the servo motor might require a different voltage depending on your setup.
• Pulse and Direction Signals: Connect the output terminals of the PLC to the servo motor’s input terminals for pulse and direction signals. Note that the pulse and direction pins on the MR-J4-A typically require a 5V DC signal, so you must use resistors to step down the 24V DC from the PLC to 5V DC.Note: Use appropriate resistors to reduce the voltage from 24V DC to 5V DC for the pulse and direction control pins. This is crucial to prevent damage to the servo motor’s input circuitry.
• Grounding and Shielding: Properly ground all components to reduce electrical noise and ensure stable operation. If available, use shielded cables for signal connections to further minimize interference.

Step 2: Configuring Siemens S7-200 Pulse Train Output (PTO)

2.1 Overview of PTO Configuration

The Pulse Train Output (PTO) function in the Siemens S7-200 PLC allows for precise control of the servo motor by generating high-speed pulses. Configuring the PTO settings is crucial for achieving accurate servo motor movement.

2.2 PTO Control Registers

The S7-200 PLC uses specific registers to control the PWM/PTO functions. These registers must be configured to match the operational requirements of the Mitsubishi MR-J4-A Servo Motor.

The relevant control registers for PTO in the Siemens S7-200 PLC.

2.3 PTO Configuration Settings

• Pulse Frequency: Set the pulse frequency according to the desired speed of the servo motor. This frequency determines how fast the pulses are sent to the servo motor, directly affecting its speed.
• Duty Cycle: Adjust the duty cycle as needed. The duty cycle controls the proportion of time the pulse is high versus low, which can influence the motor’s responsiveness and power.
• Direction Control: Configure the direction control settings to ensure the servo motor moves in the correct direction based on the command inputs.

The PTO configuration screen in the Siemens STEP 7 Micro/WIN software.

Step 3: Mitsubishi MR-J4-A Parameters Setting

3.1 Overview of Servo Configuration

Configuring the Mitsubishi MR-J4-A Servo Motor correctly is essential to ensure it responds accurately to the commands issued by the Siemens S7-200 PLC. This step involves setting key parameters that dictate the motor’s behavior during operation.

3.2 Key Parameters to Configure

Using the MR-Configurator2 software, the following parameters should be configured:

• PA1: Servo Control Mode Selection
  • Value: Set to 1000.
  • Purpose: This parameter selects the position control mode, which is necessary for precise servo positioning based on pulse commands from the PLC.
• PA6/PA7: CMX/CDV (Input Pulse Gain Ratio)
  • Default Value: 1/1.
  • Purpose: These parameters adjust the pulse-to-revolution ratio, ensuring that the servo motor interprets the pulses from the PLC correctly. The default setting corresponds to 131072 pulses/rev.
• PA13: PLSS (Selection of Control Pulse Types)
  • Default Value: 0100.
  • Purpose: Configures the type of pulse input that the servo motor will accept. This setting must be correct to ensure compatibility with the PLC’s pulse output method.

Table here that lists the various pulse input types and their corresponding settings

3.3 Recommended Settings for Your Project

For this project, use the following configuration settings as recommended by FAIZAL AFZAL:

• PA1: Set to 1000 for position control mode.
• PA6/PA7: Maintain at default 1/1 for correct pulse gain ratio.
• PA13: Set according to the pulse type used in your PLC configuration.

These settings ensure that your servo motor will operate efficiently and respond accurately to the control commands issued by the PLC.

The key parameter values and their corresponding settings.

Step 4: Siemens S7-200 PLC Programming

4.1 Overview of PLC Programming

Programming the Siemens S7-200 PLC involves writing a control program that manages the servo motor’s ON/OFF states, position control, and direction control. This program also needs to handle any input signals from sensors or external devices.

4.2 Servo Motor ON/OFF Control

The first part of the program should include logic to turn the servo motor on and off. This can be done using simple ladder logic that activates the motor when a certain condition is met (e.g., a start button is pressed) and deactivates it when another condition occurs (e.g., a stop button is pressed or a limit switch is triggered).

The control logic code used in the Siemens STEP 7 Micro/WIN software to control the servo motor ON/OFF state.

4.3 Servo Motor Position Control

The core of the control program will involve sending pulse commands to move the servo motor to specific positions. This is achieved by configuring the PTO to generate the correct number of pulses, which corresponds to the desired position of the servo motor.

• Positioning Logic: Implement logic that calculates the number of pulses required to move the servo motor to a specified position.
• Direction Control: Ensure that the program correctly handles direction changes, sending the appropriate signals to the motor based on the target position relative to the current position.

The control logic code used to manage the servo motor’s positioning.

4.4 Advanced Features (Optional)

For more advanced control, consider adding the following features:

• Speed Adjustment: Implement a variable speed control based on process requirements or external inputs.
• Error Handling: Add error detection and handling logic to respond to faults such as overcurrent, overheating, or encoder errors in the servo motor.

Conclusion

This tutorial provided a comprehensive guide on how to control a Mitsubishi MR-J4-A Servo Motor using a Siemens S7-200 PLC. By following these steps, you can achieve precise and reliable control over your servo motor, enhancing the performance and flexibility of your industrial automation systems.

For further exploration, consider experimenting with more advanced PLC programming techniques and integrating additional sensors or control devices to expand the capabilities of your system.

For further assistance or more detailed information, please refer to the Mitsubishi manuals or contact a Mitsubishi Electric support representative.