Centre for Mechanical Technology and Automation

Institute of Electronics Engineering and Telematics

TEMA

IEETA http://www.mec.ua.pt/robotics

Simulation Tools for a Real Humanoid Robot

Pedro Ferreira1

Filipe M. T. Silva1

Vítor M. F. Santos2

1 Department of Electronics and Telecommunications2 Department of Mechanical Engineering

University of Aveiro, PORTUGALUniversity of Aveiro, PORTUGAL

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Overview Humanoid overview Inclinometers

From measure to control

High-level motion algorithms Bipedal locomotion Rotation Kick

Simulation Platform Why Matlab? Specification and functionalities Limitations About Future

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Humanoid Structure Complete humanoid model

22 degrees of freedom Weight - 5 kg Height - 60 cm Max. width - 25 cm Foot print - 20 8 (cm2)

Actuation Servomotors with transmission ratio

Sensors A vision Camera (CCD) Servos’ position (through its internal

potentiometers) Sensitive foot to applied forces Accelerometers/Inclinometers Gyroscopes

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Local Control

Power resistor (0.47)

16:1 multiplexer

CAN connector

Piggy-back socket

PIC Cristal oscillator

CAN driver

PIC

Unit CAN Address

PWM plugs

Servo fuse

Fuse status LED

Piggy-back board 2

Piggy-back board 1

Connector to sensor

CAN bus Power plug

Power regulator Reset button

RS232 plug

Connector to sensor

Each slave controller is made of a PIC 18F258 device with I/O interfacing

All slave units: Connect up to 3 servomotors Have a common base (a piggy-

back unit can add I/O sensors)

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Distributed Control System A Main Control Unit (PC):

Exchanges high-level orders and interacts with the camera.

RS-232 communication with the Distributor unit.

Distributor Unit (Master): Interface between the Main and

the Local control units. Adapts the RS-232 to CAN

commands (and vice-versa). 8 Local Control Units (Slaves):

Control the low-level features of the several devices.

CAN bus to connect them.

Main ControlMain Control

RS23RS2322MasteMaste

rr

CAN CAN BUSBUS

1

23 1

2

3

1

2

31

2 1

2

3

1

2

3

1

2

3

1

2

SlaveSlavess

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Accelerometer/Inclinometer The Accelerometer/Inclinometer used is ADXL202E

(Analog Devices). It can measure accelerations with a full-scale range of ±2G. It can measure both dynamic acceleration (e.g., vibration)

and static acceleration (e.g., gravity).

)1/(

)1/(

gAyASINRoll

gAxASINPitch

When the accelerometer is oriented so both its X and Y axes are parallel to the earth’s surface it can be used as a two axis tilt sensor with a roll and a pitch axis.

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

From Measure to Control Proportional Control

Delta = error*2.5*K*1e-2;• Delta is the increment applied to servo• Error is the difference between the wanted and

the measure inclination • 2.5 is the transmission ratio of servo• K*1e-2 is the real gain of controller

K vary between 10 and 50• Higher values give rise to

oscillations• Lower values has a very slow

effect

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Inclinometers Experiment Experiment condition

Varying reference CoP, so the leg perform a square trajectory

Square with ~15cm width 2 seconds to perform a edge Controller gain was 30

Response of inclinometer controller Max delay = 0.797 seconds Max error = ~9 degrees

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

High-level Motion Algorithms Quasi-static Motion

All the movements are planned at a low velocity and with the CoP always on the support foot.

Locomotion Essential algorithm based on a quasi-static walking

motion which assure that the CoP is always on the support foot.

Rotation Very important movement with tricky aspects.

Kick Simple movement

Stair Walking Not yet developed!

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Bipedal locomotion1

Cartesian space Specification Parameters

Step Length Hip height Hip y-coordinate center position Foot max elevation

Divided in 4 phases Prepare Start Step

• Middle point End of step Prepare Next Step

1 Developed by Professor Filipe Silva

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Bipedal Locomotion Multiple Steps

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Rotation1

Cartesian and joint space motion plan Specification Parameters

Inclination angle Rotation angle Hip height Foot max elevation

Divided in 10 phases Prepare Rise free foot Rotate Align CoP with new support foot Finish movement

1 Developed by Professor Filipe Silva

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Rotation Tricky aspect

Rotation axis isn't align with the foot

Final foot position isn’t align with the hit

Need adjust booth hit rotation joint to change the CoP to the new support foot

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Kick Specification Parameters

Inclination angle Hip height Foot max elevation

Divided in 4 phases Prepare Align CoP with new support foot Rise free foot Kick

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Simulator TwoLegs_22dof

Motivations Turn the interaction with the robot

more easy Need to assemble multiple work

already developed like high-level movements, control adjust, communication interface…

Create an interface that allow a new user start playing with the robot in a more intuitive way

Developed on Matlab tool GUIDE

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Why Matlab? Disadvantages

Not the most flexible Poor GUI development objects Often must use tricks and unfriendly techniques Slow performance

Advantages Communications protocol already developed Mathematical solutions (inverse and direct kinematics

among others mathematical operations) Easy integration of new work developed on Matlab Easy and intuitive development environment Do you speak Matlab?

• A little bit!• No need to learn object oriented languages like Visual

Basic, C++, C#, …

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Specifications and Functionalities Joint space motion plan Integrate high-level movements Plot adjusts like

Change ground dimensions and position Put in Ball Put in Stairs Show CoG and CoP

Communication interface Allow send and receive joint position for/from

Humanoid robot Trajectory plane visualization

Plot all the trajectory that the SCU will build up, with all the phases of the entire movement

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Limitations Besides the Matlab limitations already

pointed…

Isn’t modeled dynamic forces

Do not detect components collision

Has no physical joint limitations

Need to know the implementation to include new high-level movements

Don’t allow to change the slaves local control

Only joint movements are allowed on the main windows

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

Future work Modeling dynamic forces Include different terrain topologies Highlight active joint when performing a

move Develop different ways of doing the same

movement Allow dynamic adjust of PID parameters Include a virtual image of the real Humanoid

Robot Modeling all the sensor which take in

redundancy and better control (…)

UNIVERSITY OF AVEIRO, PORTUGALCentre for Mechanical Technology and AutomationInstitute of Electronics Engineering and Telematics

The End