Mitsubishi Electric MELDAS MDS-B-SVJ2 Series, Технические характеристики и инструкция по эксплуатации

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Chapter 11 Selection
11-5
11-2-2 Servomotor precision
The control precision of the servomotor is determined by the detector resolution, motor characteristics
and parameter adjustment. This section examines the following four types of servomotor control
precision when the servo parameters are adjusted. When selecting a servo, confirm that these types
of precision satisfy the machine specifications before determining the servomotor series.
(1) Theoretic precision:
Δε
This value is determined by the motor detector precision, and is the value obtained by dividing the
movement amount (
Δ
S) per motor rotation by the detector resolution (RNG).
(2) Positioning precision :
Δε
p
This is the precision outline that affects the machine targeted for positioning, and expresses the
machine's positioning precision.
When the motor is a single unit, this is determined by the detector resolution and matches with
the theoretic precision
Δε
p. When the motor is actually installed on a machine, the positioning
precision
Δε
p becomes 1 to 2 times the theoretic precision
Δε
. This is due to the effect on the
motor control by the machine rigidity, etc. Furthermore, the value to which the error from the
motor shaft to the machine end is added becomes the actual machine end positioning precision.
For machines requiring accurate positioning precision at the machine end, use the
MDS-C1-V1/V2 Series servo amplifier capable of scale feedback input.
(3) Surface precision during machining :
Δε
v
This is the precision outline that affects the machine tools, etc., which are important factors in the
machine operation path and interpolation functions. It also affects the surface roughness of the
machining surface. The machining surface roughness is affected by elements caused by the
motor's electrical characteristics (torque ripple, etc.) and mechanical characteristics (cogging
torque, etc.). In the NC unit feed axis motor (HC
†
, HA
†
N) those torque characteristics are
excellent, and higher precision machining is possible than that of other motors. Because the
effects of torque ripple and cogging torque are relatively smaller in motors with large amounts of
inertia, the motor with the larger inertia of two identical capacity motors will be more
advantageous for surface precision. Due to the effects of differences in characteristics of the
motor itself, the surface precision during machining will differ greatly according to the motor
series.
(4) Absolute position repeatability :
Δε
a
This is the precision outline that affects the absolute position system machine, and expresses the
repeatability of the position before the power was shut off and the position when the power is
turned on again.
With the single motor unit, the precision is 1 to 2 times the theoretic precision
Δε
. Note that the
absolute position repeatability
Δε
a is the difference from when the power was turned off last and
returned on. This error is not cumulated.