Hydrabot the modular electro hydraulic robot arm
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Hydrabot The Modular Electro-Hydraulic Robot Arm. Abed Alnaif Group 3 4A Mechatronics Engineering University of Waterloo. November 17, 2008. Introduction. Modular Robot Arms Flexibility in length and shape of robot arm Currently use electrical actuators

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Hydrabot The Modular Electro-Hydraulic Robot Arm

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Hydrabot the modular electro hydraulic robot arm

HydrabotThe Modular Electro-Hydraulic Robot Arm

Abed Alnaif

Group 3

4A Mechatronics Engineering

University of Waterloo

November 17, 2008


Introduction

Introduction

  • Modular Robot Arms

    • Flexibility in length and shape of robot arm

    • Currently use electrical actuators

      • Limitations on number of modules and payload

  • Needs Assessment:

    • Modular robot with greater payload and lesser limitations on number of modules

Modular Electro-Hydraulic Robot Arm


Goals objectives

Goals & Objectives

  • Goals:

    • 2 modules built

    • Simple control algorithm developed

  • Objectives:

    • Should perform better than currently available modular robots in at least one of these categories:

      • Cost

      • Size

      • Payload

Modular Electro-Hydraulic Robot Arm


Constraints criteria

Constraints & Criteria

  • Constraints:

    • $1500 / module

    • Should support at least 15 modules

  • Criteria:

    • Size

    • Load Capabilities

    • Controllability (ease and accuracy of control)

Modular Electro-Hydraulic Robot Arm


Idea use hydraulic actuators

Idea: Use Hydraulic Actuators

  • Advantages of hydraulics:

    • High power-to-weight ratio

      • Powerpack can be located on the ground

    • Actuator stiffness due to incompressible oil

  • Disadvantages of hydraulics:

    • Need to use valves

    • Oil leaks

    • Nonlinear control

    • Noisy

Modular Electro-Hydraulic Robot Arm


Design overview design methodology

Design Overview: Design Methodology

  • Design methodology, in chronological order:

    • Choose type of actuator

    • Choose sensor

    • Choose valve

    • Design structure

Modular Electro-Hydraulic Robot Arm


Design overview actuator selection

Design Overview: Actuator Selection

  • Hydrostatic (no actuators)

    • Very cheap

    • Difficult to control (no stiffness)

Modular Electro-Hydraulic Robot Arm


Design overview actuator selection 2

Design Overview: Actuator Selection (2)

  • Hydraulic Rotary Actuators

    • ~ $800 (outside constraints)

    • Direct rotary output

  • Hydraulic Cylinders

    • ~ $150

    • Need to convert linear to rotary motion

Modular Electro-Hydraulic Robot Arm


Design overview sensor selection

Design Overview: Sensor Selection

  • Two ways of sensing module positions

    • Measure piston position

      • Off-the shelf

      • Very expensive ( ~ $700 )

    • Rotary potentiometer

      • Cheap

Modular Electro-Hydraulic Robot Arm


Design overview valve selection

Design Overview: Valve Selection

  • Directional valve

    • Controls direction of flow only (not magnitude of flow)

Modular Electro-Hydraulic Robot Arm


Design overview valve selection 2

Design Overview: Valve Selection (2)

  • Servo valve

    • Controls both direction and magnitude of flow

    • Very good, fast performance

    • Linear flow vs. command signal

    • Very, very expensive (beyond budget constraints)

Modular Electro-Hydraulic Robot Arm


Design overview valve selection 3

Design Overview: Valve Selection (3)

  • Proportional Valve

    • Similar to directional valve, except it accepts an analog command signal to solenoids

      • Allows valve to throttle flow according to command signal

    • Worse performance than servo valve (slower and nonlinear)

    • ~ $400


Design overview structure design

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

Modular Electro-Hydraulic Robot Arm


Design overview structure design 2

Design Overview: Structure Design (2)

Isometric View

Side View

Modular Electro-Hydraulic Robot Arm


Design overview structure design 3

Design Overview: Structure Design (3)

Internal Oil Routing

Red = Pressure (from pump)

Blue = Return (to reservoir)

Orange and Green = Actuators

Modular Electro-Hydraulic Robot Arm


Design specifications

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

206 mm

386 mm

Modular Electro-Hydraulic Robot Arm


Design feature reconfigurable

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

Modular Electro-Hydraulic Robot Arm


Design assessment

Design Assessment

Amtec PowerCube servo-motor and gear box:

Modular Electro-Hydraulic Robot Arm


Manufacturing and testing plan

Manufacturing and Testing Plan

Begin manufacturing and development of control algorithm

Connect to powerpack and continue testing

Feb. 20, 2009

Mar. 31, 2009

Jan. 5, 2009

Mar. 5, 2009

Design symposium

Complete manufacturing. Begin dry testing with LabVIEW (check if all signals are as expected)


The possibilities

The Possibilities…

Questions?

Modular Electro-Hydraulic Robot Arm


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