5.2 Flexible Gantry Robot
5.2.5 Some Final Thoughts
Active and robust position control of a fl exible gantry robot arm was performed using bidirectional-type ER clutch actuators and piezoceramic actuators. The bidi- rectional ER clutch is designed and manufactured on the basis of the fi eld-dependent
Moving part
X Y
High-voltage amplifier
D/A converter A/D converter
ER clutch LVDT
Housing Ball screw
Piezofilm sensor
Flexible arm Tip mass
Piezoceramic
actuator DC motor
D/A converter Voltage amplifier
Analog filter (a)
ER clutch
LVDT
LVDT
DC motor
Flexible arm DC motor
(b)
Moving part A/D converter
Diode
FIGURE 5.13 Experimental apparatus for position tracking control. (a) Schematic diagram and (b) photograph.
Bingham model of the ER fl uid. The torque transmission performance of the ER clutch was experimentally evaluated with respect to the electric fi eld. The ER clutch actuator model was then formulated, and its transfer function model was derived. In addition, the dynamic model of fl exible robot arm was formulated with consideration of the actuator characteristics, and it was represented by the transfer function. Following the establishment of the control system models as left coprime factorizations, robust LSDP H∞ controllers for the ER clutch and piezoceramic actuator have been designed. The control system takes account for parameter vari- ations such as natural frequency and damping ratio deviations due to the tip mass
0.00 0.03 0.06 0.09 0.12 0.15
–6 –3 0 3 6
–4 –2 0 2 4
–100 –50 0 50 100
0.00 0.03 0.06 0.09 0.12 0.15
–6 –3 0 3 6
–4 –2 0 2 4
0 8 10 –1000 8 10
–50 0 50 100 Desired
Actual
Displacement (m)Electric field (kV/mm)
W/O feedback voltage With feedback voltage
Tip deflection (mm)Feedback voltage (V)
Time (s)
Desired Actual
Displacement (m)Electric field (kV/mm)
W/O feedback voltage With feedback voltage
Tip deflection (mm)Feedback voltage (V)
Time (s) (a)
6 4
2 2 4 6
(b)
FIGURE 5.14 Measured regulating control responses. (a) Without tip mass and (b) with 10 g tip mass. (From Han, S.S. et al., J. Robot. Syst., 16, 581, 1999. With permission.)
as payload, and uncertainties such as the viscous coeffi cient of the ER clutch and the total moving mass of table system. It has been shown through experimental realization that the smart actuator control system is very effective for robust and accurate position tracking control of the fl exible gantry robot arm without exhibiting the undesirable oscillation.
–6 –3 0 3 6
–0.10 –0.05 0.00 0.05 0.10
–6 –3 0 3 6
–6 –4 –2 0 2 4 6
–60 –30 0 30 60
–0.10 –0.05 0.00 0.05 0.10
0 5 10 15 20 25 0 5 10 15 20 25
–0.10 –0.05 0.00 0.05 0.10 –0.10–0.10 –0.05 0.00 0.05 0.10 –0.05
0.00 0.05 0.10 –0.10
–0.05 0.00 0.05 0.10
Electric field (kV/mm)
Desired Actual Error
Y axis displacement (m) Electric field (kV/mm)
W/O feedback voltage With feedback voltage
Tip displacement (mm)
Time (s)
Feedback voltage (V)
Time (s)
Desired W/O voltage
Y axis displacement (m)
X axis displacement (m)
With voltage
Y axis displacement (m)
X axis displacement (m)
Start point Start point
Desired Desired Actual
Error
X axis displacement (m)
FIGURE 5.15 Measured tracking control responses (without tip mass). (From Han, S.S.
et al., J. Robot. Syst., 16, 581, 1999. With permission.)
–0.10 –0.05 0.00 0.05 0.10
–6 –3 0 3 6
–0.10 –0.05 0.00 0.05 0.10
–6 –3 0 3 6
–6 –4 –2 0 2 4 6
–100 –50 0 50 100
–0.10 –0.05 0.00 0.05 0.10
0 5 10 15 20 25 0 5 10 15 20 25
–0.10 –0.05 0.00 0.05 0.10 –0.10 –0.05 0.00 0.05 0.10
–0.10 –0.05 0.00 0.05 0.10
Desired Actual Error
X axis displacement (m) Electric field (kV/mm)
Desired Actual Error
Y axis displacement (m) Electric field (kV/mm)
W/O feedback voltage With feedback voltage
Tip displacement (mm)
Time (s)
Feedback voltage (V)
Time (s)
With voltage
Y axis displacement (m)
X axis displacement (m) Start point
Desired Desired
Start point
W/O voltage
Y axis displacement (m)
X axis displacement (m)
FIGURE 5.16 Measured tracking control responses (with 10 g tip mass). (From Han, S.S.
et al., J. Robot. Syst., 16, 581, 1999. With permission.)
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6 Application to Fine
Motion Control System
6.1 OPTICAL PICKUP DEVICE