Hydrabot The Modular Electro-Hydraulic Robot Arm Abed Alnaif Group 3 4A Mechatronics Engineering...

HydrabotThe Modular

Electro-Hydraulic Robot Arm

Abed AlnaifGroup 3

4A Mechatronics EngineeringUniversity of WaterlooNovember 17, 2008

Introduction• Modular Robot Arms

o Flexibility in length and shape of robot arm

o Currently use electrical actuators• Limitations on number of modules and

payload

• Needs Assessment:oModular robot with greater payload

and lesser limitations on number of modules

2Modular Electro-Hydraulic Robot Arm

Goals & Objectives

• Goals:o 2 modules builto Simple control algorithm developed

• Objectives:o Should perform better than currently available

modular robots in at least one of these categories:oCosto SizeoPayload


Constraints & Criteria

• Constraints:o $1500 / moduleo Should support at least 15 modules

• Criteria:o Sizeo Load Capabilitieso Controllability (ease and accuracy of control)


Idea: Use Hydraulic Actuators• Advantages of hydraulics:

o High power-to-weight ratio• Powerpack can be located on the ground

o Actuator stiffness due to incompressible oil

• Disadvantages of hydraulics:o Need to use valveso Oil leakso Nonlinear controlo Noisy


Design Overview: Design Methodology

• Design methodology, in chronological order:1. Choose type of actuator2. Choose sensor3. Choose valve4. Design structure


Design Overview: Actuator Selection

• Hydrostatic (no actuators)o Very cheapo Difficult to control (no stiffness)


Design Overview: Actuator Selection (2)

• Hydraulic Rotary Actuatorso ~ $800 (outside constraints)o Direct rotary output

• Hydraulic Cylinderso ~ $150o Need to convert linear to rotary motion


Design Overview: Sensor Selection

• Two ways of sensing module positionsoMeasure piston position• Off-the shelf• Very expensive ( ~ $700 )

o Rotary potentiometer• Cheap


Design Overview: Valve Selection

• Directional valveo Controls direction of flow only (not magnitude of

flow)


Design Overview: Valve Selection (2)

• Servo valveo Controls both direction and

magnitude of flowo Very good, fast performanceo Linear flow vs. command

signalo Very, very expensive (beyond

budget constraints)


Design Overview: Valve Selection (3)

• Proportional Valveo Similar to directional valve, except it accepts an

analog command signal to solenoids• Allows valve to throttle flow according to command

signaloWorse performance than servo valve (slower and

nonlinear)o ~ $400

Design Overview: Structure Design

• Have hydraulic cylinders acting on torque arm

• Balance loading by having 2 hydraulic cylinders apply force in opposite directions

• Only 1 valve required to control both cylinders


Design Overview: Structure Design (2)

Isometric View Side View


Design Overview: Structure Design (3)

Internal Oil Routing

Red = Pressure (from pump)

Blue = Return (to reservoir)

Orange and Green = Actuators


Design Specifications

• Dimensions: 206x386 mm

• Weight: 6.6 kg

• Torque (at 45° rotation and with cylinders pulling): 1657 N-m

• Max number of modules: 11.4

386 mm

206 mm


Design Feature: Reconfigurable• Each module adds 1 degree of freedom• Modules are reconfigurable to allow flexibility in shape of

robot arm

Parallel Axes Perpendicular Axes


Design AssessmentCategory Hydrabot Amtec

PowerCubeMeets Project

Constraints?Cost $1500 Much less YesSize 206 x 386 mm 90 x 220 mm Yes

Weight 6.6 kg 5.6 kg YesTorque 1657 N-m 142 N-m Yes

Max # of modules

11.4 4.8 Yes

Amtec PowerCube

servo-motor and gear box: 18Modular Electro-Hydraulic Robot Arm

Manufacturing and Testing Plan

Jan. 5, 2009

Begin manufacturing

and development of

control algorithm Feb. 20, 2009

Complete manufacturing.

Begin dry testing with LabVIEW

(check if all signals are as expected)

Mar. 5, 2009

Connect to powerpack and continue testing Mar. 31, 2009

Design symposium

19

The Possibilities…

Questions?


Hydrabot The Modular Electro-Hydraulic Robot Arm Abed Alnaif Group 3 4A Mechatronics Engineering...

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