thin wafer handling robot
DESCRIPTION
Thin Wafer Handling Robot. Jordan Hall, Fang Li, Joel Neff, and Alex Podust. Background Handling of thin silicon wafers for solar cells Reducing handling stress and characterizing residual stresses are part of manufacturing research Objective - PowerPoint PPT PresentationTRANSCRIPT
Thin Wafer Handling Robot
Jordan Hall, Fang Li, Joel Neff, and Alex Podust
• Background– Handling of thin silicon wafers for solar cells– Reducing handling stress and characterizing
residual stresses are part of manufacturing research
• Objective– Design a robot to move wafers between
conveyor and inspection station without dropping or imposing large gripping forces
– Minimize energy consumption and handling time
Overall System
Bernoulli Gripper
Bernoulli Gripper Model
• Used an mass flow input to create a vertical “lift” force– Gripper force depends on
distance to wafer– Rubber pads keep wafer from
impacting gripper frame
• The friction of the pads keeps wafer “stuck” to the gripper as the robot accelerates
-1 -0.8 -0.6 -0.4 -0.2 00
0.05
0.1
0.15
0.2
rrel (m)
Forc
e grip
per (N
)
Gripper Force vs. Relative Distance
Gripper Force Balance
Friction force is only active when the wafer is contacting the posts
Gripper – Modelica Code
Gripper - Verification
0.0 2.5 5.00
10
20
30
40
50
60
Mas
s Fl
ow R
ate
(L/m
in)
Time (sec)
gripper_correct_lift.m_dot_in
0.0 2.5 5.0-0.05
0.00
0.05
0.10
0.15
0.20
[N]
Time (sec)
gripper_correct_lift.bernoulliForce
Wafer separates
WaferPick-up
Gripper Model Challenges• Required text-based Modelica
modeling – No MultiBody sliding friction model– Required pneumatic->mechanical
energy conversion– Force balance and direction vectors
defined “from scratch.”
• Interaction between gripper and wafer was highly coupled; required in-depth Dymola experience
Fgripper
Ffriction
Actuator
Electric MechanicalEMFV Torque
DC MOTOR
OutputController(PID) MotorCommand
+ -
AXIS CONTROLLER
Chassis
Base
Rotating Joint
Lin. joint
Axis 1 θ
Rotating Joint
Rotating Joint
Rotating Joint
Arm 1
Arm 2
Arm 3
Axis 2 θ
Axis 3 mm
Axis 4 θ
Axis 5 θ
Gripper position
ROBOT ARM
Model Limitations• Inflexibility - Path hard coded as joint angle
start and end values.• Multiple simplifying assumptions s.a.
– Motor– Gripper– Chassis– Cost of robot components not considered.
• Hard to determine safety factor for wafer flying off gripper.
Results
Energy usage (J) vs time (s)
Gripper friction and lateral force (N) vs time (s)
Lessons learned• Value of using simulation software to solve
engineering design problems• Gained appreciation for information
economics• Do not underestimate complexity of
modeling details of a system• How to make good decisions under
uncertainty