Servotronix CDHD2S - Error Correction; Overview of Error Correction; Error Correction Table - Example

Application Setup
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THERMTRIPLEVELTHE
RMCLEARLEVEL
The detection and removal mechanism of motor over-temperature fault is
subject to hysteresis mechanism. When the resistance exceeds a certain
value, it will trip and the fault can only be cleared when the resistance
drops below a different value.
⚫ For PTC thermistors, when the resistance is equal to or greater
than THERMTRIPLEVEL, the motor over-temperature fault will lead
to tripping. When the resistance is equal to or less than
THERMTRIPLEVEL, the fault can be cleared.
⚫ For NTC thermistors, when the resistance is equal to or less
than THERMTRIPLEVEL, the motor over-temperature fault will lead
to tripping. When the resistance is equal to or greater than
THERMTRIPLEVEL, the fault can be cleared.
⚫ If the motor temperature sensor is a thermostat, the resistance is
zero in normal state and infinite in fault state.
When the drive detects a motor over-temperature condition, it will block the motor over-
temperature fault and the digital display will display H|FH
.
6.17 Error Correction
6.17.1 Overview of error correction
The CDHD2S drive has an error correction function that can cancel repeatable positioning
errors.
An error map is generated using an external measurement device such as a laser interferometer.
The error map is stored in the non-volatile drive memory. The drive retrieves the correction value
in real time based on the actual position and performs dynamic (on-the-fly) correction. After the
correction, the error is negligible. Therefore, no additional position feedback device is required.
6.17.2 Error correction table - example
In this example, the load position on the linear axis is measured with a laser interferometer.
The axis travel distance is one meter. The drive software commands the motor to rotate every
100mm so that the motor moves through 10 position ranges. As the motor moves the load, the
laser system measures the distance traveled by the load, comparing it to the motor encoder
position at each point. The difference between the two values is the error correction value.
To ensure smooth movement, the drive performs linear interpolation between the points of
the error table. In this example, to move the platform to 275 mm from the origin, the controller
selects the two data points closest to the error map (200 and 300 mm) and calculates the correction
value for the 275 mm point.
Table 6-23