The load estimation function of Fanuc robot is a useful feature. It allows the robot to accurately calculate the load it is handling. When in operation, the robot’s sensors and algorithms work together. By analyzing parameters like joint torques, accelerations, and velocities during movement, the system can estimate the mass, center of gravity, and inertia of the load.
This function is crucial as it helps optimize the robot’s performance. It enables the robot to adjust its movements and power output according to the actual load, reducing the risk of damage to the robot or the load itself. Additionally, it can enhance the precision of operations, especially in tasks that require high accuracy with varying loads. In summary, the load estimation function boosts the efficiency and reliability of Fanuc robots.
1 Overview
The load estimation function is used to estimate the load size of tools, workpieces, etc. installed at the front end of the robot. By properly setting the load information at the front end of the robot, the robot’s motion performance can be improved, such as reducing vibration, improving motion rhythm, etc., while more effectively exerting dynamics-related performance, such as gravity compensation function and collision protection function.
2 Operation steps
2.1 Confirmation of load estimation accuracy
1) If the robot is not calibrated after replacing the motor and other parts, the estimation accuracy will be very poor. Therefore, the accuracy of the load estimation must be confirmed before performing the load estimation. The accuracy is confirmed by comparing the value of the system variable $PLCL_GRP[group].$TRQ_MGN[axis] with the “Torque Margin Data” table in the inspection results book in the teach pendant paper box. Find “$PLCL_GRP” in the system variable and click F2 “Details”, then select “$TRQ_MGN” and click F2 “Details”.
2.2 Load number and estimation condition setting
1) Load number and estimation condition setting need to be entered from the action screen. Press the “MENU” key to select “System” on the next page, and then click “Action” to enter the action performance screen.
2) Press “NEXT” and then press F2 “Estimation” to display the load estimation screen. Press F3 to select the number for which you want to set the estimation condition. At the same time, specifying the load mass before estimation can improve the estimation accuracy. In the load estimation screen, select “Yes” for the mass known and enter the mass value.
2.3 Estimated position setting
1) Before setting the estimated position, teach the robot to the appropriate position to avoid interference between the robot and other equipment when performing the estimation. Click the details on the next page of the estimation screen to enter the estimated position setting interface as shown in the figure below. Estimated position 1 and position 2 can use the default values, or set them by direct input, or teach the robot to the desired position and press SHIFT+F5 “Record”. Make sure that the robot does not interfere with peripheral equipment when it moves between position 1 and position 2.
2) When the robot performs load estimation, only J5 and J6 axes move, and other axes remain in the same position. The movement range of J5 and J6 is between estimated position 1 and position 2. Therefore, the following principles should be met for the setting of estimated position 1 and position 2:
When in the estimated position, the center of gravity of the load should be located on the rotary axis plane containing the J5 and J6 axes.
The rotary axis of the J5 axis is placed horizontally, and the interval angle between the J5 and J6 axes at position 1 and position 2 is as close to 180° as possible.
2.4 Load Estimation Execution
After the estimated position is set, press the “PREV” key to return to the load estimation screen, then turn the teach pendant knob OFF, press F4 “Execute”, and select “Yes” when the prompt “Start execution?” appears. The robot will complete the low-speed mode action and high-speed mode action. It is forbidden to approach the robot during the action.
2.5 Estimation result confirmation
1) After the robot’s estimated action is completed, “1 Load estimation” in the load estimation screen will change to “Complete”, and if it stops suddenly during the action, it will be “Interrupted”. After the estimated action is completed, press F5 “Apply”. When the prompt “The path and cycle time will change, set?” appears, press F4 “Yes” to set the estimated value to the corresponding condition number, and press F5 “No” to stop setting. After setting, you can enter the detailed screen of the corresponding condition number for confirmation. If the correct calculation is not performed, any or all of the estimated results (mass, load center, load inertia) will be 0.
- Notes
1) If the load mass is very small, load estimation cannot be performed. The load mass is required to be more than 5% of the maximum transportable mass.
2) After replacing the motor and other mechanical parts, calibration is required first, otherwise the accuracy of load estimation will be very low.
3) Some models do not support the load estimation function, such as M140iB/160, CR-35iA Green Robot, etc.