Presentation 131

Low Cost Shadow Function based ArticulatedRobotic Arm

Authored by –Vishwajit Nandi, Pronadeep Bora

June 12, 2015

OutlineIntroduction

Aim of the Project

Factors under Consideration

Material Selection

System Design

The Control System

Conclusion

Low Cost Shadow Function based Articulated Robotic Arm

Introduction• Requirement of Robotic Arm took birth when humans felt the importance of reaching

places where a Human Arm cannot reach without harming itself or to do things beyondits capabilities.

• A Robotic Arm is a robot manipulator, usually programmable, with similar functionsto a human arm.

• Application of Robotic Arms includes Cranes, Excavators etc.

• Principle of Robotic Arm is used in various industries for manufacturing and productionpurposes.

ICEPE 2015 | NIT Meghalaya 3/23


Aim of the Project

• To build an Articulated Robotic Arm.

• To establish a proper way of controlling the Robotic Arm.

• To establish 5 Degree of Freedom within the workspace of the Arm.

• The Robotic Arm should replicate the moment of the Human Arm.

• The final design must be cost effective.



Factors under Consideration

Material Selection1. Cost

2. Weight of robot

3. Ease of manufacturing the parts

4. Ease of assembly

5. Strength and durability of the parts



Requirements for efficient Power transmission

1. Small size

2. Low weight and moment of inertia

3. High effective stiffness

4. Accurate and constant transmission ratio

5. Low energy losses and friction for better responsiveness of the control system



Material Selection

For the frameAvailable options for building the arm frame were –

• Beryllium, Steel – costly

• Ceramics – brittle

• Aluminium(Al), Magnesium(Mg) and Titanium(Ti) – ageing, creep in under constantloads, high thermal expansion coefficient etc.

• Fiber plastics and Glass-reinforced plastics – costly

Considering all the factors and keeping the price low a Al-Li alloy was finally selected for thepurpose.



For the actuators

• Servo motors were used because of its high precision, dynamic performances, reliabilityand stability.

• Servo motor can produce very high torque characteristics.



Torque calculation for the actuators

Wx : Weight of link ‘x’Lx : Length of link ‘x’



The servo motors used in the arm are thus chosen according to this calculation.Torque about Joint 1:

T1 =L1

2× W1 + (L1 +

L2

2) × W2 + (L1 + L2 +

L3

2) × W3

+(L1 + L2 + L3 +L4

2) × W4 + (L1 + L2 + L3 + L4) × W5 (1)

Torque about Joint 2:

T2 =L2

2× W2 + (L2 +

L3

2) × W3 + (L2 + L3 +

L4

2) × W4

+ (L2 + L3 + L4) × W5 (2)

Torque about Joint 3:

T3 =L3

2× W3 + (L3 +

L4

2) × W4 + (L3 + L4) × W5 (3)



System Design

Power Supply Unit• A High Current Step-Down Transformer is used to drop the voltage of the input AC

line.

• The Bridge Rectifier Circuit is made using IN5408 Power Diodes and High StorageCapacitor(3300 F).

• Each motor is given a separate voltage regulator to provide enough power. The voltageregulator used is 7806 which can give a maximum of 1A.



Arduino based PCB

• A Custom-made board based on Arduino Duemilanove has been made, optimized indesign for the purpose of the project.

• A preloaded Arduino Duemilanove Boot-loader, which directly supports Arduino Pro-gramming Language making the programming simpler, is used.



ATMEGA48/88/168-PU

1k

1k1k

10k

1k

100nF

100nF 100nF

100nF

10uF/40V

VC

C

VCC

VC

C

GND

GND GN

D

GND

GND

22pF

22pF

PW

M3

PWM5

PWM6

PWM9

PW

M10

PW

M11

GN

D

GN

D

GND

GND

GND

7805 7806 7806 7806 7806 78067806

GND GNDGND

GND

GNDGND

GNDGND

GND

GND

VC

C

GND

10uF/40V 10uF/40V 10uF/40V

10uF/40V

10uF/40V10uF/40V

VC

C

POWER_JACKSLT

IC1

PB5(SCK/PCINT5) 19

PB7(XTAL2/TOSC2/PCINT7)10

PB6(XTAL1/TOSC1/PCINT6)9

GND8

VCC7

AGND22

AREF21 AVCC20

PB4(MISO/PCINT4) 18PB3(MOSI/OC2A/PCINT3) 17PB2(SS/OC1B/PCINT2) 16PB1(OC1A/PCINT1) 15PB0(ICP1/CLKO/PCINT0) 14

PD7(AIN1/PCINT23) 13PD6(AIN0/OC0A/PCINT22) 12PD5(T1/OC0B/PCINT21) 11PD4(T0/XCK/PCINT20) 6PD3(INT1/OC2B/PCINT19) 5PD2(INT0/PCINT18) 4PD1(TXD/PCINT17) 3PD0(RXD/PCINT16) 2

PC5(ADC5/SCLPCINT13) 28PC4(ADC4/SDA/PCINT12) 27PC3(ADC3/PCINT11) 26PC2(ADC2/PCINT10) 25PC1(ADC1/PCINT9) 24PC0(ADC0/PCINT8) 23PC6(/RESET/PCINT14)1

R1

R2

R3

R4

R5

C10C

2

C11 C6

C8

C7

S1

1 342

Q1

21

C3

C4

LED

1JP

2 1 2 3

JP3 1 2 3

JP4123

JP5123

JP6123

JP7

123

JP8

123

LED

2

IC2GND

IN OUT

IC3GND

IN OUT

IC4GND

IN OUT

IC5GND

IN OUT

IC6GND

IN OUT

IC7GND

IN OUT

IC8GND

IN OUT

JP1123456

JP91 23 45 6

C15 C16 C17

C18

C19C20

J1

RST

RS

T



The Control System

Different Modes of Control

1. Manual Control Mode – Using Position Sensors(Potentiometers)

2. Computer Control Mode – Using a Computer’s Keyboard(via Serial Communication)



Manual Control Mode - The Potentiometer

• We connect three wires of the potentiometer to the Arduino board.–The first goes to ground from one of the outer pins of the potentiometer.– The second goes to 5 volts from the other outer pin of the potentiometer.– The middle pin of the potentiometer is connected to the analog inputs of the ArduinoBoard.

• By turning the shaft of the potentiometer, we change the amount of resistance oneither side of the wiper which is connected to the center pin of the potentiometer.–This changes the relative “closeness”of that pin to 5 volts and ground, giving us adfferent analog input.



Manual Control Mode - PWM Generation

• The 10 bit Successive Approximation ADCs that comes along with the PDIP of AT-Mega328P converts the analog inputs to represent 210 = 1024 digital levels.

• ‘0’ Volt analog input corresponds to 0D; ‘5’ Volt analog input corresponds to 1024D

• These 1024 digital quantized levels are mapped directly to the 180◦ rotation of the ServoMotor by generation of PWM signals in any of the 6 channels as per requirement.



Manual Control Mode - Work flow



Computer Controlled Mode• 2 keys in the keyboard are defined

– one to increase the duty cycle of the PWM Signal– other to decrease the duty cycle of the PWM Signal.

• When a key, assigned for increasing/decreasing the duty cycle, is pressed its ASCIIvalue is transferred to the Controller Board and the Servo Motor rotates CW/CCWaccordingly.

• Programmable Serial USART of ATMega328P is used for communication between thecomputer and the Controller Board.



Computer Controlled Mode - Workflow



Conclusion

The Final Working Model of the Project taken in hand was a–

1. Low Cost 5 DOF Articulated Robotic Arm.

2. Low Cost Potentiometer-based controller.

3. Robotic Arm which can replicate a Human Hand movement.

4. Robotic Arm which can be controlled using a computer keyboard.


References[1] Gillespie, R.B. and Colgate, J. E.; Peshkin, M. A., “A General Framework for Robot Control,” IEEE Transactions on

Robotics and Automation, vol.17, no.4, pp.391-401, Aug 2001.

[2] J. C. Trinkle and R. James Milgram, “Complete Path Planning for Closed Kinematics Chains with Spherical Joints,” SAGEInternational Journal of Robotic Research, vol.21, no.9, pp.773- 789, Sep 2002.

[3] Gemeinder, M. and Gerke, M., “GA-based path planning for mobile robot systems employing an active search algorithm,”Applied Soft Computing, vol.3, no.2, pp.149-158, Sep 2003.

[4] Jegede Olawale; Awodele Oludele; Ajayi Ayodele; Ndong Miko, “Development of a Microcontroller Based Robotic Arm,”in Proceedings of the 2007 Computer Science and IT Education Conference, Mauritius, 2007, pg. 549-557.

[5] Six-servo Robot Arm[online]. Available:http://www.arexx.com

[6] Robotic Arm[online]. Available:http://explorerschools.nasa.gov/

[7] Arduino Duemilanove[online].Available:http://arduino.cc/en/Main/arduinoBoardDuemilanove

Thank You

Presentation 131

Documents

Transcript of Presentation 131