Readjusting friction
To obtain even more accurate values for the configuration, the parameterization can be readjusted during operation (with an installed robot arm).
- Move the robot at the slowest speed possible. Increase or decrease the static friction ratio (constant friction) using the SEW_GVL_Internal.Robot_Axis[i]_PhysicalGearMotor.fbGear.stConfigActive.stFriction.lrOffset variable until the discrepancy between the current and calculated motor torque is as low as possible. The trace from chapter "Systematically measuring friction" can be used for this purpose.
- Move the robot on a typical application path with varying speed. Increase or decrease the dynamic friction ratio (rotational speed/speed-dependent friction) using the SEW_GVL_Internal.Robot_Axis[i]_PhysicalGearMotor.fbGear.stConfigActive.stFriction.lrGradient variable until the discrepancy between the current and calculated motor torque is as low as possible.
- Perform step 1 again to correct the effect of step 2 for a static friction ratio (constant friction) (generally reduce the value slightly).
- Perform step 2 again and check whether good results can continue to be obtained.
- With the robot, drive off paths where the motors have a direction of rotation reversal. A surge in the simulated torque can be smoothed using the smoothing factor of the frictional curve for direction of rotation reversal. Increase or decrease the smoothing factor SEW_GVL_Internal.Robot_Axis[i]_PhysicalGearMotor.fbGear.stConfigActive.stFriction.lrDirectionThreshold until the discrepancy in the zero crossing between the current and calculated motor torque is as low as possible.
- Multiply the values by "π/180" and transfer the determined friction parameters to the MOVISUITE® configuration (internally calculated in radians instead of degrees). Load the new configuration in MOVISUITE® in "Startup" mode onto the MOVI-C® CONTROLLER.
- Ensure that the torque discrepancy in actual operation is as low as possible (orientation value: Very good modeling: < 10%, good < 25%, adequate < 50%). To do so, create a trace using the SEW_GVL_Internal.Robot_Axis[i]_PhysicalGearMotor.fbMotor.fbDeviationCalculator.stOut.lrCalculatedDeviation_Torque variable (unit: % nominal motor torque in relation to the motor shaft). For more accurate analyses, the following two variables can also be added: SEW_GVL_Internal.Robot_Axis[i]_PhysicalGearMotor.fbMotor.fbDeviationCalculator.stIn.lrActualTorque (unit: % nominal motor torque in relation to the motor shaft), SEW_GVL_Internal.Robot_Axis[i]_PhysicalGearMotor.fbMotor.fbDeviationCalculator.stOut.lrSetpointTorque_DeadtimeDelayed (unit: °/s in relation to the motor shaft). Contact SEW‑EURODRIVE if you are unable to achieve good modeling.
INFORMATION
