H2ME

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H2ME
Analog Is Art

• IIT Kharagpur.

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Introduction

• The Human Hand Movement Emulator (H2ME) combines
  concepts of Mechanical and Electronics
  Engineering to form a robotic emulator hand, that
  can grip, move and perform similar tasks as done
  by a human hand at places that are inaccessible
  or not fit for the human hand.

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Topics of Discussion

• The Beginning
• Market Value
• The Basics
• Design Implementation
• - Mechanical Parts
• - Electronic Parts

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The Beginning

• The "Product", to be exhibited should be
• - Innovative
• - Applicable
• - Economical
• - Profitable

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Market Value Application

• A subsitute for human hands in tasks unfit for
  humans
• - Nuclear Plants
• - Deep Sea Exploration
• - Handling dangerous chemicals
• - Space Walks

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Industrial Applications

• With certain modifications, the mechanical hand
  can be programmed to perform a number of
  industrial jobs. It will then work as a "Robotic
  Arm" following a set of instructions.

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The Basics

• For the H2ME, we need to transfer the movement of
  the human arm onto the mechanical arm. This
  movement is in the form of rotation of the
  joints. We need to transfer this rotation, both
  the angle as well as the direction, using
  electronic signals that control the motors
  attached to the mechanical arm.

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Design Implementation

• The Basic Block Diagram of the H2ME is as
  follows

Joints
Potentiometers
Signal Processing
Voltage Controlled Motor
Feedback ( Pots )
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Mechanical Construction

• The Human Side
• The mechanism on the human side has two
  rods, one free to rotate in the vertical and
  other in the horizontal plane. The joints are
  made using Bearings. There are two potentiometers
  attached, one to each joint. As each pair have
  the same axis, the potentiometers rotate the
  same angle and in the same direction as the rod
  to which they are attached.

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Potentiometers

• A potentiometer is basically a variable
  resistance. It consists of two fixed ends and a
  movable third "Lug". As this end rotates over the
  resistnce strip, with a fixed potential
  difference between the two ends, the output of
  this middle end provides voltage that is
  indicative of the direction and angle of
  rotation.Electronic Circuit(Signal Processing
  Block)

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The Circuit
Circuit 1
H-Bridge for Gripper.
Not gate
Inverter
Diodes
Adders
Subtractor
IC 7805
Comparator 2 for Enabling the Bridge
Comparator 1 for Determining polarity
H-Bridge for the two Motors.
Circuit 2
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Signal Processing

• As the shaft of the potentiometers rotate along
  with the axes of the two joints, the signal from
  the variable pin of the pots (with a fixed
  potential difference applied across its two ends,
  here 5V) changes. The magnitude of the change in
  this voltage indicates the angle by which the
  axes rotate while the sign i.e. increment or
  decrement in the voltage, gives the direction of
  rotation. In the circuit this signal is processed
  and then it drives the geared motor on the
  robotic arm. The motor rotates the rods in such a
  way that the output of the variable pin of the
  pots attached to these joints also varies in the
  same manner as their counterpart pots on the
  assembly attached to the human hand.

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Signal Processing (Continued)

• This means that the circuit makes the output of
  the pots on the robotic arm "track" the changes
  in outputs of the pots on the assembly attached
  to the human hand. There is thus a feedback
  circuit involved. To measure the angle of
  rotation we use a subtractor circuit, calculating
  the magnitude of the difference of the outputs of
  the two complementary pots. A comparator circuit
  is used to determine the direction in which the
  motor is to be rotated to copy the rotation of
  the human joints. Thus the basic job of the
  circuit is to continually track the changes in
  the outputs of the two complementary pots by
  rotating the motors in such a way that the
  difference in the outputs is always zero.

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H-Bridge

• The IC L298N (H-Bridge) is used to drive the two
  geared motors. It has two (Dual) H-Bridges in it.
  Each bridge accepts two TTL compatible inputs.
  When both are 1 or both 0 the effective potential
  difference between the two output pins is very
  small, about zero. However when the inputs are 1
  0 or 0 1 there is a potential difference of about
  Vs volts across the two output pins which are
  connected to the motor inputs. Please note that
  the polarities of this potential difference is
  opposite for the two cases 1 0 and 0 1. There is
  an enable pin which allows us to enable or
  disable the circuit irrespective of the inputs.
  This pin is used to stop the motors when the
  difference between the two pot outputs is less
  than 0.2 volt in magnitude. This margin is
  provided to prevent oscillations near the zero
  crossover point for the circuit.

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Geared Motors

• There are two geared motors used to rotate the
  two rods. The advantages of these motors above
  the normal dc motors
• - Due to gearing system the motor is locked
  in the absence of any supply. So the shaft
  doesn't rotate on its own due to gravity.
• - Also due to gearing the speed is reduced
  thus effectively increasing the torque giving
  better control

There are two parts as shown. Lower one (black)
is the motor and the one above is the internal
gearbox.
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L298N ( H-Bridge )
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The Team 'Analog is Art'

• R Yogesh Kumar
• 4th Yr. B.Tech. Electronics EC Engg.
• Abhinav Nigam
• 3rd Yr. B.Tech. Manufacturing Sci. Engg
• Pranay Kishore
• 3rd Yr. B.Tech. Aerospace Engg.
• Siddharth Seth
• 2nd Yr. B.Tech. Electronics EC Engg.
• Amit Gupta
• 2nd Yr. B.Tech. Civil Engg.

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Presentation created by
H2ME

• Siddharth Seth
• IIT Kharagpur