Parker LX80L, Руководство по эксплуатации продукта

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LX80L Series Product Manual
45
Parker Hannifin Corporation
EMN Automation - Parker
Irwin, Pennsylvania
Causes of Temperature Increases
One or more of the following conditions may affect the temperature of the MX80L
carriage:
Ambient Temperature
This is the air temperature that surrounds the LX80L
Application or Environment Sources
These are mounting surfaces or other items which produce a thermal change that affect the tem-
perature of the LX80L base (i.e. X/Y configurations with motors or other heat generating devices
that heat the mounting surface and thus thermally affect the LX80L base).
Motor heating from LX80L
Since the LX80L uses a servo motor as its drive, it produces no heat unless there is motion, or a
force being generated. In low duty cycle applications heat generation is low, however as duty
cycles increase, temperature of the LX80L will increase, causing thermal expansion of the car-
riage. With very high duty cycles these temperatures can reach temperatures as high as 30° C
above ambient.
Compensating for Thermal Effects
If the application requires high accuracy, the thermal effects must either be removed by regulating base
temperature or compensated for with a correction factor added to the commanded position.
Controlling the
base temperature is the best method. However, this means controlling the ambient temperature by remov-
ing all heat/cold generators from the area and operating at very low duty cycles. Compensation is the
other way of achieving accuracy without sacrificing performance. In this case the system must be exer-
cised through its normal operating cycle. The temperature of the base should be measured and recorded
from the beginning (cold) until the base becomes thermally stable. This base temperature should be used
in a compensation equation. Below is the fundamental
thermal compensation equation :
C
d
= (I
d
- ((I
d
) * (T
e
) * DT))
C
d
= Corrected displacement (mm)
I
d
= Incremental displacement (mm)
T
e
= Thermal Expansion (0.000022 mm/mm/° C)
DT = Temperature Differential from 20° C
Example:
base Temperature of 32° C required move of 100mm
Cd = 100mm - (100mm * 0.000022mm/mm/°C * 12° C) =
99.9736mm
In this example the commanded move should be 26.4 microns less (100mm – 99.9736mm) than the de-
sired move. This will compensate for the thermal expansion of the scale. This is a simple linear correction
factor and can be programmed in to most servo controllers using variables for the position commands.