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LinX Series Linear Motor - User Guide
14 D-000168 Rev 02 ANCA Motion
Linear Encoder
4.5
The linear encoder is used to provide position feedback to the servo drive to allow for accurate control of the LinX
motor. The type of encoder used depends greatly on the application; factors such as the required precision,
operating environment and servo drive signaling requirements need to be taken into account. As the LinX motor
does not have any backlash, it is recommended that any position feedback system chosen also does not contain
backlash. The most commonly used encoders consist of an encoded surface, either solid rail or adhesive strip,
mounted parallel to the shaft and a sensor read head mounted to the forcer.
NOTE: To maximise performance, the encoder should be placed as close as possible to the motor. If there
must be separation, maximising the stiffness to minimise deflection is desired.
Resolution 4.5.1
Encoder resolution has a large impact on the precision, accuracy and smoothness of the LinX cylindrical motor
system. The positional accuracy of the system can never be greater than the position feedback supplied by the
encoder. Additionally, the response speed of the encoder must be taken into account when operating at the
applications top speed. Finally
, the servo drive’s maximum encoder bandwidth must also be considered. Consult
your servo drive manual on supported encoder signal types and bandwidths.
Magnetic Encoders 4.5.2
Due to the highly magnetic nature of the shaft, care must be taken when installing a magnetic encoder. It is
possible that the shaft will affect the strip or read head resulting in inaccuracies or damage. Therefore, it is
necessary to ensure the encoder components are a sufficient distance away from the shaft. Installing the encoder
at a minimum distance of 150mm from the surface of the shaft is recommended.
Sensors
4.6
End Stop Sensors 4.6.1
End stop sensors, also known as limit switches, are used to prevent motor travel in the case of incorrect
behaviour. In the event that the motor passes a defined maximum physical position, the end stop sensors will be
triggered which can stop and/or disable the motor, minimizing potential damage. In addition to end stop sensors,
it is recommended to incorporate end stop bumpers to absorb and stop the movement in the case of over travel.
Home Sensor 4.6.2
When an incremental encoder is used, the servo drive will not know the absolute position of the motor relative to
the machine. To establish the absolute position, it is necessary to move
the motor to a known ‘home’ location,
often referred to as ‘homing’. The servo drive can be informed that it has reached the ‘home’ location in many
ways, the most common being via a proximity switch at one end of travel and/or an index (marker) pulse.
Temperature Sensor 4.6.3
The LinX cylindrical linear motor contains a KTY84/130 temperature sensor. The sensor increases in resistance
as the motor winding temperature increases. When this temperature sensor is employed, the trip temperature
should be set no higher than 120°C, and the accuracy of the circuitry involved should be no worse than +/-8°C
including the sensor accuracy.
Note that, although the sensor is located in the center of the motor, it is possible in certain use cases for an
uneven temperature distribution within the forcer to result in the sensor reporting a lower value than the maximum
temperature within the motor. Therefore, it is recommended that the current limits in
section 5.1 are obeyed
through use of I2R overload protection within the servo drive. Both the AMD2000 and AMD5x servo drive series
offer I2R overload protection functionality.