MIRAI Real-Time Data Exchange Registers on Universal Robots / RTDE / OnRobot URcap

Customers using OnRobot Force Torque sensors may encounter unexpected errors from the MIRAI Training App or on Polyscope indicating a lost connection between the controller and the robot:

Possible Error Messages: 

• "MIRAI program node stopped. Please ensure MIRAI controller is reconnected." on Polyscope
• "Failed to connect to 192.168.101.1:6543" on Mirai App

In some cases, users with UR Teach Pendant with the 3-Position Enabling Device will have issues using “Automatic Mode” with the MIRAI URCap installed. Automatic mode is a third operational mode in addition to the standard Remote and Manual options.

Since there is an overlap between the RTDE registers with the MIRAI URCap, the OnRobot registers need to be offset in order to resolve these errors. Note: MIRAI registers are not configurable, however OnRobot registers can be configured as of the latest OnRobot URCap update. 

The input parameters used by MIRAI are:

WRITE	READ
input_float_register_24 input_float_register_25 input_float_register_26 input_float_register_27 input_float_register_28 input_float_register_29 input_float_register_30 Input_int_register_24	actual_TCP_speed actual_q target_q robot_status_bits

Onrobot uses the floating-point data type - MIRAI uses Double while OnRobot uses Float. Be mindful of this when configuring your offsets.

Offset values will vary from system to system depending on what registers have already been assigned and therefore the correct offset values should be configured on a case-by-case basis. Below are suggested offsets to try that have proven successful on new UR setups that are only integrating with MIRAI, possibly a gripper, and the OnRobot Force Torque Sensor. Keep in mind that the offset best for your system is one that does not overlap any currently occupied registers.

Suggested Offset Values
CB3-Series: Boot: 0 Int: 7 Float: 7	E-Series: Boot: 10 Int: 10 Float: 9

Steps:

1. On Polyscope - navigate to the "Installation" tab at the top of the screen
2. Select "system" from the left panel
3. Tap on "URcaps" 
4. Select "OnRobot Setup" 
5. Within the Registers section, update the offset parameters based on the version of Force Torque sensor you have installed (see chart above).
6. A system reboot is not required but we recommend this step if the issue persists after saving changes.

For more details on URCap Basics:

https://www.universal-robots.com/articles/ur/urplus-resources/urcap-basics/