This presentation is on my Graduate Thesis.

1. Two-Legged Robot
Design, Simulation and Realization
(Sep-2006 to May 2007)
Guided By: Prepared By:
Dr. S N. Pradhan Nirav A. Patel
Prof. K D. Shah ( 05mce011)

2. Architecture of two-legged robot
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3. Subsystems of the robot
• Mechanical subsystem
• Electronics subsystem
• Software subsystem
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4. Mechanical subsystem
• This subsystem focuses on
• Actuators
• CAD drawing of robot
• Torque and speed calculation
• Dimensional specification of the robot
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5. Mechanical Subsystem
• Consists of
• Stepper motor for open loop control of different
joints
• Gearbox for increasing torque
• CAD model showing placement of different
components
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6. Stepper Motors
• Provides good open loop control by means of
rotating one step per signal applied
• Types
• Unipolar
• Less torque
• Easy to control
• Bipolar
• Greater torque
• Harder to control compared to Unipolar motors
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7. Stepper motors from precision
motors
Specifications D-48-42-B20 D-48-42-B25 D-48-42-B28
Units Bipolar Bipolar Bipolar
Medium Torque High Torque High Torque
Operating Voltage V 6 12 24
Resistance per phase ohms 2.7 6 15
Inductance per phase mH 3 6 12
Holding Torque mNm(oz-in) 94.9 (13.47) 148 (21.1) 164 (23.3)
Detent Torque mNm(oz-in) 18.5 (2.67) 18.5 (2.67) 18.5 (2.67)
Rotor Inertia g-m2 25.6 x 10-4 25.6 x 10-4 25.6 x 10-4
Weight gms (oz) 185 (6.52) 185 (6.52) 185 (6.52)
Step Angle degrees 7.5 7.5 7.5
Step angle accuracy o +/- 0.5o +/- 0.5o +/- 0.5o
Max. operating oC 100 100 100
temperature
Dielectric strength - 1000 VAC for 1 min. 1000 VAC for 1 min. 1000 VAC for 1 min.
End play mm (in) 0.2 (0.008) 0.2 (0.008) 0.2 (0.008)
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8. Torque characteristics
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9. Locations of Degrees of Freedom
• figure shows position of all
motors
• ML1:Clock-AnticlockRotation of
Ankle joint.
• ML2:Up-Down movement of
Ankle joint.
• ML3: Movement of Knee joint.
• ML4:Up-Down movement of
Pelvis joint.
• ML5: Clock-Anticlock rotation
of pelvis joint
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10. Values for torque calculations
• Motor Weight = 185 gram
• Gearbox Weight = 350 gram
• Controller Weight = 50 gram
• Other material weight = 1 kg
• We also assume that total height will be 60
cm so distance of CG from any motor will
not be more than 30 cm.
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11. Torque required by ML1
Since this is the motor requiring maximum torque when it has to
lift rest of the body to maintain CG.So weight required to
be lifted by this motor is
W = No of Motors *(Motor Weight + Controller Weight
Gearbox weight) + Other Material Weight. (in gram)
= 9 * (185 + 50 + 350) + 1000
=6265 gram
=6.265 Kg
Now maximum torque required by this motor is
T = W * 30
= 6.265 * 30
=187.95 Kg-cm
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12. Torque required by ML5
Weight required to be lifted by this motor is
W = No of Motors *(Motor Weight + Controller Weight
Gearbox weight) + Other Material Weight. (in gram)
= 5 * (185 + 50 + 350) + 1000
= 3925 gram
= 3.925 Kg
Now maximum torque required by this motor is
T = W * 30
= 3.925 * 30
= 117.75 Kg-cm
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13. Motor and gearbox specifications
• Stepper Motor
• Motor Model : D-48-42-B28
• Weight = 185 gram
• Holding Torque = 1.24 Kg-cm
• Operating Voltage = 24V
• Step Angle = 7.5 degree
• Gearbox
• Gearbox Model:GB4
• Maximum torque = 200 Kg-cm
• Gear efficiency = 0.6
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14. Available torque calculation…
• Suppose we assume that
• N is Gear Ratio
• To is Output torque at gearbox shaft
• Ti is input torque to gearbox
• Tm is torque produced by motor
• Ge is gearbox efficiency
• Then,
• To = Ti * Ge * N or To = Tm * Ge * N
because Tm=Ti
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15. Available torque calculation
• Here,
• Tm = Ti = 1.24 Kg-cm
• Ge = 0.6
• To = 187.95 Kg-cm
• So,
• 1.87.95 = 1.24 * 0.6 * N
• =>N = 252.62
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16. Dimensional specifications of robot
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17. Mechanical CAD drawing
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18. Factors affecting the design
• Weight of motors.
• Should be less enough so that it meets torque
requirements
• Weight of Gearbox
• Should be less enough compared to maximum
torque at output shaft
• Torque of Motors
• Should be high enough to lift the whole body
when combined with gearbox
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19. Electronics subsystem
• This subsystem focuses on
• Microcontroller development board and its
connection with stepper motor controllers
• Microcontroller and its interfacing with
computer
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20. Electronics subsystem
• Consists of
• Microcontroller development board
• Atmel 89S52 In system programmable
Microcontroller
• Stepper motor controllers
• A3982 from Allegro Microsystems
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21. Microcontroller
• Used to control movements of stepper
motors and to communicate with PC
• Easy to program with the help of
development boards available in the market
• 89S52 is one of the most popular 8-bit
Microcontroller which have 4 output ports
so provides enough no of pins to control
more no of motors
• 89S52 can easily interfaced with PC
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22. AT89S52 PCB layout
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23. AT89S52 development board
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24. Stepper Motor Controller
• Controlling stepper motor just by 2 signals instead
of one for each coil which ranges from 4 to 8
• Reduced programming complexity
• Two signals per motor
• Step
• Direction (CW/ACW)
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25. Functional block diagram of A3982
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26. Block diagram representation of
A3982
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27. Microcontroller Development board
and stepper motor controllers
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28. Software subsystem
• This subsystem focuses on
• Controlling stepper motors to establish stable
walking
• Generating stable walking pattern
• It consists of
• Two-legged robot simulator
• Application Specific Compiler
• Torque Analyzer
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29. Two-Legged Robot simulator
• Simulates movements of different parts of
body
• Can be used to analyze movements and
their effects on centre of gravity
• Shows 3D model on computer screen
• Provides GUI with buttons for applying
movements to different parts.
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30. Need for Two-Legged Robot
Simulator.
• Development of humanoid costs a lot so its
better to use computer for simulation at low
cost.
• It can simulate almost all possibilities.
• Can go for applying different algorithms
without applying much more changes in
design.
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31. Snapshots of the simulator
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32. Isometric view of robot
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33. Front view of robot
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34. Side view of the robot
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35. Top view of the robot
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36. Application specific compiler(ASC)
• Special type of compiler having application
specific instruction set
• Developed compiler is for two-legged robot
which have instructions like
• MOVE LEFT LEG UP BY 5
• ROTATE LEFT ANKLE CLOCKWISE BY 34
• Generates assembly language code for 8051
family of microcontrollers
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37. Flowchart of ASC
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38. Instructions supported by ASC
Instruction Joint Actuated
ROTATE LEFT ANKLE CLOCKWISE BY Left Ankle(Rotate)
ROTATE LEFT ANKLE ANTI-CLOCKWISE BY Left Ankle(Rotate)
MOVE LEFT ANKLE UP BY Left Ankle(Move)
MOVE LEFT ANKLE DOWN BY Left Ankle(Move)
MOVE LEFT KNEE UP BY Left Knee
MOVE LEFT KNEE DOWN BY Left Knee
ROTATE LEFT LEG CLOCKWISE BY Left Leg(Rotate)
ROTATE LEFT LEG ANTI-CLOCKWISE BY Left Leg(Rotate)
MOVE LEFT LEG UP BY Left Leg(Move)
MOVE LEFT LEG DOWN BY Left Leg(Move)
ROTATE RIGHT ANKLE CLOCKWISE BY Right Ankle(Rotate)
ROTATE RIGHT ANKLE ANTI-CLOCKWISE BY Right Ankle(Rotate)
MOVE RIGHT ANKLE UP BY Right Ankle(Move)
MOVE RIGHT ANKLE DOWN BY Right Ankle(Move)
MOVE RIGHT KNEE UP BY Right Knee
MOVE RIGHT KNEE DOWN BY Right Knee
ROTATE RIGHT LEG CLOCKWISE BY Right Leg(Rotate)
ROTATE RIGHT LEG ANTI-CLOCKWISE BY Right Leg(Rotate)
MOVE RIGHT LEG UP BY Right Leg(Move)
MOVE RIGHT LEG DOWN BY Right Leg(Move)
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39. Snapshot of ASC
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40. Complete flow of Simulator and
Compiler
• 1: Write high level code in ASC
• 2: Verify the code using simulator for desired
functionality
• 3: Compile the verified code to generate Assembly
language code for specific Microcontroller
• 4: Compile Assembly code using Assembler to
generate Hex file
• 5: Load the Hex file in the Microcontroller
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41. High Level Language Program
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42. Verify the program
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43. Compile the verified program
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44. Load in the Keil
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45. Logic Analyzer
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46. Torque Analyzer
• Torque analyzer
• Records torque required by each joint of robot while
program is being executed by ASC.
• Shows recorded data in form of graphs.
• Program to take first step from start position
rotate left ankle anti-clockwise by 35 , rotate left leg
clockwise by 35 , rotate right leg anti-clockwise by 35 ,
rotate right ankle clockwise by 35;
move right leg up by 60 , move right knee down by
30;move right leg up by 32 , move left leg down by 32 ,
move right knee down by 32 , move left ankle down by 40;
move right knee up by 32 , move right ankle down by 40;
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47. Torque required at right knee joint
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48. Torque required by all the joints
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49. Conclusion
• For two-legged robots torque requirements are
very high compared to multi legged robots and
wheeled robots.
• Balancing is one of the most difficult tasks for
two-legged robots.
• In the Table 1 maximum torque required by robot
without including dynamics of the robot are given
for taking one step forward from rest condition.
• From the table we can conclude that knee joint
requires highest torque.
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50. Table 1. Maximum torque required
by joints of robot
Joint Name Maximum Torque
Kg-cm
Left Ankle(Up/Down) 145
Left Ankle(Clock/Anti-clock) 43
Left Knee 0
Left Pelvis(Up/Down) 70
Left Pelvis(Clock/Anti-clock) 53
Right Ankle(Up/Down) 2
Right Ankle(Clock/Anti-clock) 43
Right Knee 34
Right Pelvis(Up/Down) 77
Right Pelvis(Clock/Anti-clock) 46
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51. References
• Satoru Shirata, Atsushi Konno, and Masaru Uchiyama,
“Design and Development of a Light-Weight Biped
Humanoid Robot Saika-4”, Proceedings of IEEE/RSJ
International Conference on Intelligent Robots and
Systems, Sendai, Japan, September 28 - October 2, 2004,
pp. 148-153.
• Rainer Bischoff and Tamhant Jain,”Natural
Communication and Interaction with Humanoid
Robots”, Second International Symposium on Humanoid
Robots, Tokyo, Japan, October 1999.
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52. References…
• Qiang Huang, Yoshihiko Nakamura, Hirohiko Arai, and Kazuo
Tanie, “Development of a Biped Humanoid Simulator”,
Proceedings of the lEEE/RSJ International Conference on
intelligent Robots and Systems , Takamatsu, Japan, Vol. 3, 2000, pp.
1936-1942.
• Riadh Zaier, “Motion Generation of Humanoid Robot based on
Polynomials Generated by Recurrent Neural Network”,
Proceedings of the First Asia International Symposium on
Mechatronics, Xi’an, China, September 27-30, 2004.
• Tetsuro Kitazoe, “Unsupervised Learning of Two Legged Robot”,
IEEE International Workshop on Robot and Human
Communication, Nagoya, Japan , 18-20 Jul, 1994, pp. 351-355.
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53. References…
• Andre Senior, and Sabri Tosunoglu, “Design of a Biped Robot”,
Florida Conference on Recent Advances in Robotics, Miami,
Florida, May 25-26, 2006.
• Kazuo Tanie, “Humanoid Robot and its Application Possibility”,
IEEE Conference on Multisensor Fusion and Integration for
Intelligent Systems, 30 July-1 Aug, 2003, pp. 213 – 214.
• “ASIMO Technical Information”, American Honda Motor Co. Inc.
Corporate Affairs and Communications, January 2003.
,http://asimo.honda.com/downloads/pdf/asimo-technical-
information.pdf
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54. References
• “History of ASIMO”
http://asimo.honda.com/AsimoHistory.aspx
• “Stepper Motor Specifications”, Precision Motors,
http://www.pmpl.co.in/d4842bi.pdf
• “Gearbox Specifications”, Mech-Tex Manufacturing
Co., http://www.mechtex.com/PDF/gb4.pdf
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