GAC 3.0
Tuning and Adjustment Manual
1-2-3500-951-00
REV B
15 August 2014
Please check with the factory for the latest version of this Manual,
*Subject to change without notice*
Table of Contents
1. Guide to Adjustment - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3
1.1 Equipment and Tools Required - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3
1.2 Mirror Attachment- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3
1.3 Scan Angle Adjustment - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3
1.4 Cautions - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4
2. Description and Location of Potentiometers, Jumper Configuration - - - - - - - - - - - - - - - - - - 5
2.1 Potentiometer Description - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5
2.2 Jumper Configuration - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5
3. Initial Setting of Potentiometers - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 6
4. Fine Tuning- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -12
4.1 Example of Adjusted Waveforms - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 12
4.1.1 Small Angle Step Response - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -12
4.1.2 Full Field Large Angle Step Response - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -13
4.2 Waveform change for each Potentiometer adjustment - - - - - - - - - - - - - - - - - - - - - - - - 13
4.2.1 SRL - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 13
4.2.2 EG - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 14
4.2.3 SG - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - 16
4.2.4 EL - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 17
4.2.5 LFD - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 19
4.2.6 HFZ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -20
4.2.7 HFD - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 21
4.2.8 NF - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 23
5. Adjustment of Input Position Command Scan Angle Scale - - - - - - - - - - - - - - - - - - - - - - - - 24
2
1. Guide to Adjustment
Every Galvo/Controller pair is tuned at Lincoln Laser to provide reasonable, stable
performance. While faster performance may be obtained it may come at the cost of
stability.
Lincoln Laser strongly recommends only those familiar with galvanometer tuning
attempt the steps in this manual.
Caution: Galvanometers and Controllers MUST be operated at the same voltage used to
perform the factory tuning or damage may result to the Motor and/or the Controller.
Galvanometers and Controllers are tuned as a matched pair, failure to operate as a pair may
result in damage to the Motor and/or Controller. Tuning voltage and paired serial numbers can
be found on the Galvanometer Final Inspection Data Sheet
1.1 Equipment and Tools Required: For purposes of this manual a ± 24 VDC linear power
supply rated at 6 amps (rms) was used
a. Power Supply: Tuning should be performed with the ± voltage rating with which the system
is intended to operate.

Lincoln Laser recommends the use of linear power supplies where possible
due to their typically large output capacitance and lack of switching noise.

Minimum current rating of 3 amps (rms), capable of supplying short term
(mSec) peaks up to 8 amps.

A power supply of insufficient current capacity will inhibit system performance
b. Oscilloscope: 3 channels minimum
It will be necessary during the tuning of the system to observe:
1. Commanded Position (Input Signal)
2. Motor Response (PSD Signal)
3. Motor Current
c. Function Generator: to supply Position Command Input for Amplitude, Notch Filter and Step
Response adjustments.
d. Flat blade screwdriver for potentiometer adjustment.
1.2 Mirror Attachment:
CAUTION
Prior to attaching, removing or adjusting the mirror, verify the Power Supply is switched OFF.
1. Fully seat the mirror onto the shaft
2. Tighten the clamping screws such that the gap on each side of the clamp is equal.
3. A loose mirror will result in system instability which could result in mirror, galvo or
controller damage.
1.3 Scan Angle Adjustment: Section 5 describes one method to perform the Scan Angle
Adjustment to the Position Command Voltage using a PSD (Position Sensitive Detector) and
+θ table (please refer to p. 24). The adjustment can be made using other methods; however
the method in Section 5 offers very high accuracy.
3
1.4 Cautions:
1. When an oscillation or an audible resonance sound is perceived during operation, an imbalance
between the center frequency of the notch filter and resonance frequency may be the cause. Please
refer to the adjustment of NF in section 4 to reduce or eliminate the oscillation

The scanner motor must be securely mounted for operation as well as adjustment – ideally
the scanner is adjusted in the mount in which it will be used for normal operation.

The scanner mount and servo heat sink should supply sufficient heat sinking for both pieces
to adequately dissipate enough heat to ensure operation within their thermal limits.

The scanner housing temperature should never exceed 50° C even for short durations or
there is the possibility of permanent damage to the galvanometer motor.
2. Avoid any external vibration or impact to the scanner.
3. If the Gain setting is too high during adjustment, uncontrolled oscillations may occur. In such a
condition, immediately reduce Gain (SG) to eliminate the condition.

The scanner and driver will overheat if extended operation during an uncontrolled oscillation is
permitted. Although the thermal protection circuit of the servo driver will attempt to protect the
galvanometer scanner, a prolonged uncontrolled oscillation condition may overheat the servo
and scanner causing permanent damage to both.

If the uncontrolled oscillation condition can not be immediately corrected then turn off the
power supply, restore all adjustments to their previous states and carefully attempt the tuning
again.

When the thermal protection function is activated, the driver disables supply power and the
output to the motor internally. Turn off the power supply, make the required adjustments to
eliminate or reduce the uncontrolled oscillations, then wait until the heat sink temperature
drops sufficiently (cool to the touch) before turning on the power again.
4
2. Description and Location of Potentiometers, Jumper Configuration
2.1 Potentiometer Description
Potentiometer
PS
SRL
EG
SG
EL
LFD
HFZ
HFD
NF
PF
LIN
Description
Position Command Input Scale
Position Command Slew Rate Limiter
Position Deviation Amplifier Gain (Error)
Position Signal Proportional Gain
Error Limiter
Position Signal Derivative Gain
Frequency Band of the Current Integral Feedback Signal
Current Integral Gain
Notch Filter Center Frequency
Position Signal Scale
Linearity Compensation
2.2 Jumper Configuration.
Control
P control
P I control
J1
2-3
1-2
J2
open
short
J3
open
open
J4
1-2
2-3
J5
open
short
J6
open
open
J7
short
short
CN5
J7
１２３４
４
３
２
１
CN4
CN1
J2
５
４
３
２
１
CN3
CN6
J1
２
１
CN7
J3
３２１
J4
２
１
CN2
１２３
J8
J6
J5
PS SRL EG SG EL LFD HFZ HFD NF PF
LIN
Fig. 1 Potentiometer and Jumper Location
5
J8
short
short
3. Initial Setting of Potentiometers
Perform this step when other attempts to correct an uncontrolled oscillation condition
have failed.
*Refer To Figure 1 for Potentiometer Locations*
a. Verify power supply is switched off and scanner is disabled (CN3-4 Open)
b. Set Function Generator to provide a 10HZ, 100mVP-P, Square Wave output.
c.
Monitor the following signals on an oscilloscope. CN3-3 may be used as GND reference
1. Position Command Input
CN3-1
2. Motor Position Output
CN5-1
3. Motor Current
CN5-2
4. Refer to Figure 2 for other circuit connections.
d. Initial Potentiometer Settings: These are 12 turn potentiometers.
These settings are initial reference settings, actual settings may vary depending on
scanner model, load and application.
SRL
EG
SG
EL
LFD
HFZ
HFD
NF
*PF
*LIN
:
:
:
:
:
:
:
:
:
:
4 turns in CCW direction from full CW
Full CCW
7 turns in CW direction from full CCW
5 turns in CW direction from full CCW
7 turns in CW direction from full CCW
7 turns in CW direction from full CCW
7 turns in CW direction from full CCW
7 turns in CW direction from full CCW
---------------------------------
(Used only when PI control is used)
(Used only when PI control is used)
(Used only when P control is used)
* For PF and LIN, adjustment should be performed per Section 5 (or equivalent) otherwise we
recommend not re-adjusting the potentiometers from the original factory adjustment.
6
Power input
Galvanometers
－
GVD‐Series
＋
ＧＮＤ
*
CN4
For Motor Drive
CN5
１２３４
N.C.
After connecting,
Servo ON
Position Command Input
４
３
２ CN1
１
CN6
CN7
２
１
５
４
３ CN3
２
１
２
１
CN2
For Position Sensor
ＧＮＤ
* CN4 is not used for PHX 030,050,075
Position Signal Output
Scanner Current Output
Fig. 2
Position Signal Output (CN5-1) is ½ the voltage scale of Position Command Input
(CN3-1). If you need to have the same voltage scale, prepare a circuit per Fig.3.
Position Signal Output waveforms shown in this manual are from the circuit shown in Fig.3.
10kΩ
20kΩ
CN7 -1
Position Input
10kΩ
CN5 -1
CN6 -2
GND
CH2 Position Output
GND
CN7 -2
Fig. 3: Example of Differential Amplification Circuit
3.1 Tuning
3.1.1 Verify CN3-4 is OPEN
3.1.2 Potentiometers set per Step d.
3.1.3 Turn on Power Supply
7
3.1.4 After confirming the amplitude and frequency of the Position Input Command from the
Function Generator, enable the servo loop by connecting CN3-4 to GND.
3.1.5 Proceed to tune the system for Small Angle Step Response per the following steps
EG should be full CCW so scanner does not move
at all. If a malfunction such as an abnormal
oscillation is observed, please turn off the power
supply and verify the Potentiometers are at their
initial settings.
If the oscillation is still present adjust the Notch
Filter per Section 4.2.8
Fig. 4
8
Slowly turn EG in the CW direction, the rotor
shaft should begin to follow the Input
Command Waveform. This will be indicated
by the Output Position and Motor Current
Waveforms. Fig.5
Continue to slowly turn EG in the CW
direction. Overshoot (under damping) of
scan position may be observed when EG is
turned in CW direction. A small amount of
overshoot is desired at this point in the
tuning process.
Fig.6
9
To reduce the overshoot observed in Fig. 6,
adjust SG, LFD, HFD and HFZ either CW
or CCW to obtain desired result
Fig.7
Fig. 7
10
3.1.6 After adjusting Small Angle Step response to resemble the waveform as shown in Fig. 7, slowly
increase the Input Command Waveform square wave to an amplitude of ±10VP-P at 10 HZ .
SRL (Slew Rate Limit) when turned in the
CCW Direction will increase the response
speed. Slew Rate should be adjusted for the
fastest speed possible consistent with stable
operation. Adjust EG, SG, LFD, HFD and HFZ
either CW or CCW to obtain desired result.
Fig. 8
Rough Tuning is completed when the
waveforms are as shown in Fig. 9.
Fig. 9
11
4. Fine Tuning
Slowly adjust each potentiometer as desired while monitoring the Output Position and
Motor Current Waveforms to match the waveforms shown in this manual
4.1 Example of Adjusted Waveforms:
* The following waveform examples are for a specific motor/load combination. Your
results may vary slightly, but should still closely resemble the depicted
waveforms.
4.1.1 Small Angle Step Response:
Input Position Command of ±100 mVP-P, 10Hz square wave with Position Output Signal
Small Angle Step Response and Motor Current.
Sample waveform：
Fig. 10
12
4.1.2 Full Field Large Angle Step Response:
Input Position command of ±10 VP-P, 10Hz square wave with Position Output Signal,
Large Angle Step Response and Motor Current.
Fig.11
4.2 Waveform change for each potentiometer adjustment
Based on the waveform examples when adjusted to the Initial Potentiometer Settings, the
charts below represent the waveform changes of each potentiometer when the
potentiometers are turned in CW and CCW directions.
4.2.1 SRL
Input Position Command of ±10 VP-P, 10Hz square wave
Turning in CCW direction
SRL is used to reduce the large angle speed.
Fig. 12
13
Turning in CW direction
SRL is used to increase the large angle
speed.
Fig. 13
4.2.2 EG
Input Position Command of ±100 mVP-P, 10Hz square wave
Fig. 14
14
Turning in CCW direction
Rising edge and scanning speed are slow. (Over
damped)
Fig. 15
Turning in CW direction
Rising and scanning speed are fast. (Under
damped resulting in Overshoot)
Fig. 16
.
15
4.2.3 SG
Input Position Command of ±100 mVP-P, 10Hz square wave
Fig. 17
Turning in CCW direction
Fig. 18
16
Turning in CW direction
Fig. 19
4.2.4 EL
Input Position Command of ± 1.0 VP-P, 10Hz square wave
Fig. 20
17
Turning in CCW direction
SRL is used to reduce the large angle speed.
Fig. 21
Turning in CW direction
SRL is used to increase the large angle speed.
Fig. 22
18
4.2.5 LFD
Input Position Command of ±100 mVP-P, 10Hz square wave
Fig. 23
Turning in CCW direction
The damping of scan position signal is reduced.
Oscillation occurs easily if it is turned excessively
in CCW direction
Fig. 24
Turning in CW direction
The damping of scan position signal is increased.
Fig. 25
19
4.2.6 HFZ
Input Position Command of ±100m VP-P, 10Hz square wave
Fig. 26
Turning in CCW direction
Over damped.
Fig. 27
20
Turning in CW direction
Under damped.
Fig. 28
4.2.7 HFD
Input Position Command of ±100 mVP-P, 10Hz square wave
Fig.29
21
Turning in CCW direction
The damping of scan position signal is reduced.
Oscillation occurs easily if it is turned excessively
in CCW direction.
Fig. 30
Turning in CW direction
The damping of scan position signal is increased.
Fig. 31
22
4.2.8 NF
Input Position Command ±50 mVP-P, sine wave 5kHZ to 30kHz
NF adjusts the center frequency of the Notch Filter circuit to reduce the effects of shaft/load
resonance frequencies. Slight oscillations may appear over the entire waveform if the
adjustment is not performed properly.
Fig.32
4.2.8.1 Set the Input Position Command of the function generator to a sine wave of ± 50
mVP-P and Target frequency (the first torsional resonant frequency of the galvanometer
scanner and mirror).
4.2.8.2 Adjust the function generator in 100 Hz increments; tune NF to obtain the least
visible p-p voltage on the Position Output and Motor Current waveforms. This should also
correspond to a decrease in the audible noise from the scanner. Resonant frequency will
depend on the scanner type and mirror size. When NF is adjusted properly, the p-p voltage
near the resonant frequency as shown on channel 2 shall be less than 10mV.
23
5. Adjustment of Input Position Command Scan Angle Scale
1) Adjustment preparation
Adjustment of the Scan Angle scale is performed optically by using the adjustment
tools as shown in Fig. 33.
Fig. 33 Fixture for Scan Angle Adjustment
2) Position Command Input
Input 0 VDC as the Position Command signal and then turn on power to the driver. Enable
the servo by connecting CN3-4 to GND.
3) Initial Positioning
Set the angle of θ table to be 0°.
Mechanically adjust the scanner so that the light of the laser hits at the center of PSD
(Position Sensitive Detector) and for the Position Output Voltage to indicate zero.
4) Input of Position Command (Full Scale)
Input +10 VDC as Position Command Signal. The mirror moves in accordance with the
change of voltage and the reflected beam will move off the active area of the PSD.
24
5) θ Table Angle Adjustment
Rotate the scanner by turning the θ table to the desired full scale scanning angle. (The
direction of rotation of the θ table is opposite to the moving direction of mirror.
6) Angle Adjustment
After the θ table is set to the target angle the laser should fall onto the PSD. Adjust
PF so that the position output voltage of the PSD is zero degrees.
25