Oral Presentation File - Servo Research

Hap$c
Device
for
Telepresence
 Robo$c
Arm
Mo$on
Tracking
with
Hap$c
Sense
 Servo
Research
 By:
Vipul
Potluri
(052443942)


Selec$on
Criteria
 •  Stepper
Motor
–
Magne$c
field
 •  No
posi$onal
feedback
 •  Cheap


•  Servo
–
Pulse
width
varia$on 

 •  Posi$onal
feedback
 •  Accurate


Servo
Motor
Block
Diagram


Control
Pulse
 •  The
signal
controlling
a
servo
(20
msecs)
can
be
supplied
by
 the
microcontroller
in
two
ways:
 –  Pulse
Width
Modula$on
(PWM)

 •  Less
soRware
complexity
 •  Increased
hardware
complexity
for
mul$
servo
usage
 •  Designed
to
generate
an
accurate
pulse
between
0%
‐
100%


–  Timers

 •  No
hardware
complexity
 •  Intelligent
soRware
using
interrupts


Preferred
method:
Usage
of
simple
3mers
and
so5ware
3mers



Output
ShaR
Movement
 •  Angle
determined
by
the
dura$on
of
the
pulse


Pulse
width
to
Voltage
Conversion
 •  When
the
pulse
goes
high
 –  A
capacitor
is
charged
at
a
constant
rate


•  When
the
pulse
goes
low
 –  Capacitor
charge
fed
to
a
buffer
amplifier
 –  Tuned
to
produce
a
useful
voltage
over
a
1ms
to
 2ms
period


Servo
Wires


Torque
Calcula$on
 •  Sta$c
Torque

 –  Easy
to
calculate
 –  Force
x
Distance


•  Dynamic
Torque
 –  Complex
calcula$on
 –  Moment
of
Iner$a
x
Angular
Accelera$on


Rough
Sketch
of
the
Arm


Proposed
Servos
 •  Gripper



Hitec
HS‐422HD
Standard
Heavy
Duty
Servo
 –  Torque:
4.1
kg/cm
–
57
oz/in


•  Wrist



Hitec
HS‐422HD
Standard
Heavy
Duty
Servo
 –  Torque:
4.1
kg/cm
–
57
oz/in


•  Elbow
 
Hitec
HS‐755HB
Giant
Scale
Servo
 –  
Torque
(Kg‐cm/Oz‐in):
13.2/183


•  Base



Hitec
HS‐805HB
Giant
Scale
Servo
 –  Torque
(Kg‐cm/Oz‐in):
24.7/343


•  Base
(rota2ng)



Hitec
HS‐805HB
Giant
Scale
Servo
 –  Torque
(Kg‐cm/Oz‐in):
24.7/343