EDH0387En1020 — 09/18
6
BG Series Goniometric Cradles
Mini-Step Drive
Is used for stepper motors, when 1 pulse emitted by electronic
corresponds to theoretical physical motion of a fraction of a full step of
the motor.
For these goniometric cradles a mini-step equals 1/10 of a full step.
Full-Step Drive
Is used for stepper motors, when 1 pulse emitted by electronic
corresponds to theoretical physical motion of 1 full step of the motor.
Stepper Motor Performance Specifications and Characteristics
Command Signals for the Stepper Motors
4.2
DC-Servo Drive Versions
DC motor-driven stages use 3 different motors and encoders depending on
the size of the cradle:
•
The BGS50CC uses a miniature DC servo motor with a motor mounted
rotary encoder, a reduction gear and a belt drive in order to fold the
motor. The result is a very small and lightweight package providing very
high resolution output and great minimum incremental motion capabili-
ty. However, reversibility is compromised due to some backlash and
hysteresis in the reduction gear and belt drive system.
•
The BGS80CC features a high resolution 4,000 cts/rev rotary encoder
with index pulse for precision homing and is the recommended choice
for applications requiring accurate bi-directional positioning. For tight-
est position control, the rotary encoder is directly mounted on the
worm screw. This avoids the majority of drive train error sources that
affect other stages with indirect position read-out.
•
The BGM120CC to BGM200CC use higher-torque DC servo motors. The
motor also features a built-in tachometer to provide superior speed sta-
bility.
Resolution Speed Angle by Step RMS Current Resistance Inductance
(°) (°/s) (°) per Phase (A) (
Ω
) (mH)
BGS50PP
0.0000969 4 0.23 0.25 12.5 5.5
BGS80PP
0.001 20 1.8 0.71 1.7 2.8
BGM120BPP
0.001 20 1.8 1.0 1.13 3.6
BGM160 & 200BPP
0.001 20 1.8 1.77 0.85 3.0
BGM120 to 200PE
0.001 2 1.8 0.71 1.65 3.2
Dir
Dir
0
2
-1
1
1
0.5
1.5
Step
1
2
3
4
5
8
7
8
+ Phase 1
+
+
–
–
+
+
–
–
– Phase 1
–
–
+
+
–
–
+
+
+ Phase 2
–
+
+
–
–
+
+
–
– Phase 2
+
–
–
+
+
–
–
+
Direction
–
MOTION
+
+ Phase 1
– Phase 1
+ Phase 2
– Phase 2
