Marcin SZAREK, Gözde ÖZCAN [Biped Robot]

8/11/2019 Marcin SZAREK, Gzde ZCAN [Biped Robot]

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Summer Research ProgramBiped Robot, development ofan autonomous walking robotMentor/Instructor: Prof. Ismail Lazoglu

Marcin Szarek

Mechanical Engineering and Robotics,

AGH University of Science andTechnology, POLAND

[email protected]

Gzde zcan

Electrical and Electronics Engineering,

Bilkent University, [email protected]

Abstract In this project, the robot uses motors to make its walking motion. The project control aspect is done by microcontrollercontroller type. Aided engineering tools was used for complex calculations. Test of dynamic gait, as motion of robot, is taken underresearch. The calculations and the experimental data is visualized.

Content

I.

Introduction .....................................................................................................................................................................1

II.

Main Body ..................................................................................................................................................................1

A. CAD model .............................................................................................................................................................1

B.

SIMULINK model ...................................................................................................................................................1

C. Servomotor ..............................................................................................................................................................2

III.

Software Solution ........................................................................................................................................................4

D.

Arduino simulation board ........................................................................................................................................4

E.

PWM generation system ..........................................................................................................................................5

F.

Gait pattern ..................................................................................................................................................................6

G. Velocity servo control ..............................................................................................................................................8

H.

Virtual Reality Toolbox model ............................................................................................................................... 10

IV. Conclusions ............................................................................................................................................................... 11

V.

References ................................................................................................................................................................. 11

I. Webinars ................................................................ ................................................................................................... 11

J.

Programs ................................................................ ................................................................................................... 11

VI.

Photos at MARC........................................................................................................................................................ 12


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I.

INTRODUCTION

Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs. An animal ormachine that usually moves in a bipedal manner is known as a biped meaning "two feet" (Latin: bi = two + ped = foot). Typesof bipedal movement include walking, running, or hopping, on two appendages (typically legs).

The project is about construction of bipedal walking robot which consists of two parts; electrical and mechanical. Inelectrical part, 8 RC servo motors located hip, knee and ankle of robot are controlled with a PC and Proteus. In addition,MATLAB controlled user interface is prepared for this purpose. In mechanical part, simulation of robot structure are modeled3D in SolidWorks and motion of bipedal walking are analyzed by modeling RC servo motor in Matlab SIMULINK. This reportwill explain what electrical, mechanical aspects and software solution of this project.

II.

MAIN BODY

A.

CAD model

Every model of legs is comprised of fives parts (Fig.1.), PELVIC is connection between its. An eight RC servomotors areused in a project. Each leg contains four of them. First motor is located on THINGH, second one is intended for motion ofKNEE, third & fourth ones are used for given ANKLE/FOOT mobility. Model basically is rest upon humanoid construction ofleg, but with many simplifications, like a reduce DOM. All parts is designed, and its CAD files is enclose to report.

Fig.1. Model of Biped. Locationof servomotors: hip, knee andankle (2 DOM) of each robot leg

B.

SIMULINK model

Conversion from SolidWorks assembly CAD model into a SimMechanics model is done. Unity coordinate system, bodysensor block is already added, it is shown in Fig.2. Through trial and error method there steps was taken to find appropriateconstrain for issue of wall-grounding construction for simulate constantly motion of walking. Unfortunately it is failure - havenot found a proper one. The idea of research was to put floor below a robot, and located biped into it.

Fig.2. SIM-model of BODY with left foot grounded.

After model initialization - to do it run initialize.m - machine for model (Fig.3) is going to reach standing position, everyeach of motor is working in design point, it means 90 degree angle (Fig.4).


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Fig.3. SIMULINK model of Biped, gravity forces on Fig.4. Servos on design point, respond

Used solution is left leg grounded, so we are able to do onefull step by opposite leg.

Feedback from sensors in model is absolute value, and it isdisplayed in Fig.4.

C. Servomotor

HS5645 High Torque servomotors are chosen to be located in hip, knee and ankle of each robot leg as it is shown in Fig.5a.The HS-5645MG is servomotor, featuring a programmable digital circuit with custom metal gear train technology. The servodelivers high resolution and torque. Specification is shown below, in Fig.5b.

Fig.5a. Digital sport servomotor: HS-5645MG High Torque Fig.5b. HS-5645MG specification. Manufacture by

Hitec RCD, USA, Inc.

In Fig.6 we can see issue of servo working pattern, and idea is present. Electrical model of servo is created in SIMULINK.Model, shown in Fig.7, include most aspects of real servo-model, like a DC motor delay. Fidelity of model is acceptable.Input of model is PWM control signal, output is stabile torque.

Fig.6. Schematic model of servomotor

0 500 1000 1500

0

20

40

60

80

100

120

140

160

180

time [ms]

degree

[o]

desired angle

R thigh

R knee

R ankleR foot

L thigh

L knee

L ankle

L foot (grounded)


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Fig.7. Electrical SIMULINK model of servo

The servo expect a pulse every 20 milliseconds (50 Hz). The length of the pulse will determine how far the motor turns.Operating angle is 45 degrees per one side pulse travelling 400 sec. A 1.5 millisecond pulse, will turn the motor to the90 degree angle, to neutral position.


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III.

SOFTWARE SOLUTION

D.

Arduino simulation board

Arduino is open source microcontroller, board photograph is shown in Fig.8. It is used in project for controlling each of eightRC servomotor.

Fig.8. Arduino Duemilanove board

Fig.9. Arduino Integrated Development Environment

The code for loading input/output board is written in C programming language by using Arduino Integrated DevelopmentEnvironment (Fig.9). RC servomotors are controlled via serial communication between PC and Arduino. Atmega 328 AVR isused and eight servomotors connections are made at a simulation. The Arduino Duemilanove board is simulated in ISISProteus 7.6 (Fig.10). In order to make serial communication in Proteus; Virtual Serial Port Driver is used for creating virtualserial ports between PC (Tera term 3.1.3) and Proteus serial ports, for example: COM3 and COM2 connection.

Fig.10. Arduino Duemilanove with Atmega 328 AVR Simulation in Proteus 7.6


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E.

PWM generation system

After connecting serial ports and opening Tera Term which is terminal emulator program, the user first enters which motorwill turn, and then direction, degree data are declared. The degree data is indicated within quotation marks(example: 2L453R30) as is shown in Fig.11. Each motor current position is kept stabile - with tolerance +/-0.5 - whilemoves. When user enters another degree in the program, motors current position is being updated according to coming degreedata. An main idea is generate proper PWM control signal according to command definition.

Fig.11. Eight RC Servo motor control by serial communication from Hyper Terminal in Proteus 7.6 Arduino Board Simulation.In Tera Term window (terminal) we can see line of commands, its results we can observe in the background (ISIS program)

The user interface (Fig.12) is made by using Matlab GUI Toolbox. This program lets the user open/close serial port ofArduino by press lefts side buttons. It also provides the user selects each motor with desired turning degree, remember that itsdesign position is 90 degree angle. The user can use the edit box to enter degree number or use slider for degree within borderof 0 to 180. After pressing send button, this data is transmitted from PC to Arduino via serial communication.

Fig.12. GUI (user interface) designed in Matlab for control eight of RC servomotorsby serial communication between PC and Arduino Duemilanove

There is an idea for further development to connect GUI and rearranged SEND button as automatic sender option withconstant frequency to transfer commands for Arduino.


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F.

Gait pattern

In the Fig.13a main SIMULINK system/file is presented. Model is comprised of electrical (Fig.7) and mechanical (Fig.2)Sim-model files (subsystems). Every motor receive each control signal, then generated Torque_Output, like a input formechanical part, set proper join into rotation motion, what is display as a animation in Virtual World. So movements of modelare simulated in real time control.

How to do a step

Fig.13b. Gait signal

For moving legs, of robot from back toforward location you have to use switchersTo perform step of biped you have toswitch both switchers in Gait signalsubsystem.

Fig.13a. Main SIMULINK file, legs control system

Gait pattern has been trialing to develop.

In Fig.14 prototype range of degrees angle areshown. The main point, to perform motion ofBiped correctly, is develop a control system ofservos velocity.

As we can notice in Fig.14. only foot join hasto follow nonlinear path of degrees anglechanging range, rest of joints has linear courseof graph.

Fig. 14. prototype range of degrees angle of step (+ 90 )

step back

step front


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In a present simulation left leg is grounded and a step by right legs is being performed. In Fig.15 we can see step back, andstep forward in Fig.16 is shown. Results of joint localization are displayed in Fig.17.

Fig.15. Right leg, step back Fig.16. Right leg, step forward

Fig.17. Location of joints of model during step performance (tree times)

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

0

20

40

60

80

100

120

140

160

180

time [ms]

degree

[o]

desired angle

R thigh

R knee

R ankle

R foot

L thigh

L knee

L ankle

L foot (grounded)


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G.

Velocity servo control

To performance step correctly we have to find out how to control a speed of servomotor. This issue is quite easy withhardware solution, if you want use specialist board for it. Here we have put effort to implement a software solution. Controlsystem velocity of servo was developing on DC motor model (Fig.20). Main system (Fig.18) lets us to doing research of findout solution for velocity control system.

Fig.18. System of servo velocity developing

Fig.19. PWM subsystem Fig.20. DC motor subsystem

In this subsystem comparison of sawtooths andsinusoide signals is being done. Model of DC motor is presented in Fig.20 which is let us find outclue of reseach of servomotors velocity Constant of DC motor, andsimulation:

R = 1.5 Ohm L = 2.16 mH J = 0.000035 kg step time = 1 kHz Max power Amplifier = 5V

Fig. 21. PWM, Delta-sigma solutionPrinciple of the delta PWM (Fig.21). The output signal (blue) is compared with the limits (green). These limits correspond to

the reference signal (red), offset by a given value. Every time the output signal reaches one of the limits, the PWM signalchanges state.


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Velocity[deg/sec]

Trajectories[degr

Trajectoryerror

Time [s]

Fig.22. Servo speed control graphs

As is shown in first graph in Fig.22 velocity has stabile with fluctuant trend. The next step of research is compile that resultwith a gait pattern system.


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H.

Virtual Reality Toolbox model

There is another solution to create settings of simulation, where an Virtual Reality Toolbox is used. In that model PELVIC isgrounded, so robots legs has no extra-loads.

SIMULINK model was exported like a XML file from SolidWorks program, after that has been updating - last version isshown in Fig.25. VR subsystem include feedback from block sensor; rotation matrixes was convert to degree angle.This implementation we can see in Fig.24. There is a VR Sink block, where Virtual World is connected. Virtual World wascreated in V-Realm Builder; Virtual Scene has been prepared, transform nodes are created. In spite of well done transformnodes, problems with connection beetwen join appears. It is easy to find that problems are connected with constrains of joints.Model include gravity forces, there is no control signal implemented into it.

Fig.23. Biped model into VRML (Virtual Reality) world

Fig.24. VR subsystem

Fig.25. Virtual World implementation prototype


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IV.

CONCLUSIONS

Table, which we can see below, show us summary of work done of this project.

REALM

ODEL

SOLUTION

DESTINATION

Gait research,Control panel

PWM generator SIMULINK Model Visualization

SOFTWAREFORSIMULATION

REALMODEL(equivalents)

NAMEOF

PROGRAMS Matlab,

GUI ToolboxArduino,

Proteus, ISIS,

Tera Term,

Virtual Serial Port Driver

Matlab,

SIMULINK,

SimElectronics Toolbox,

SimMechanics Toolbox,

SolidWorks

SolidWorks,

V-Realm Builder

V.

REFERENCES

I.

Webinars

[1]

From SolidWorks Assemblies to SimMechanics Models and Animations from Simulink 3D Animation[2] Introduction to Electromechanical Modeling in Simulink[3] Building Virtual Worlds for use with Simulink 3D Animation[4] Advanced Modeling Techniques with SimEvents[5] Introduction to Electromechanical Modeling in Simulink[6] Introduction to Simulink 3D Animation[7] Learning Basic Mechatronics Concepts Using the Arduino Board and MATLAB[8] Optimizing Mechatronic Systems Using Simulation

J. Programs

[1] Matbal 2009b[2] V-Realm Builder Version 2.0 (in Virtual Reality Toolbox included)[3] SolidWorks 2009[4] Arduino alpha, version 0017[5] Proteus 7.6 SP0, build 8304 with Advanced Simulation (ISIS Professional)

[6]

Tera Term Web Pro, version 3.1.3[7] Virtual Serial Port Driver, version 7.0, build 7.0.1.263


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VI.

PHOTOS AT MARC

(Manufacturing& Automation Research Center)

Photo no.1. Gzde zcan (team member), Professor smail Lazolu andMarcin Szarek (team member)

Photo no.3. Marcin Szarek and Gzde zcan (team members)

Photo no.2. MARC Mechanical Technician Muzaffer Btn, Gzde zcanand Marcin Szarek(team members)

Photo no.4. Gzde zcan and Marcin Szarek (team members)

Marcin SZAREK, Gözde ÖZCAN [Biped Robot]

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Transcript of Marcin SZAREK, Gözde ÖZCAN [Biped Robot]