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Hydrabot The Modular Electro-Hydraulic Robot Arm

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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  1. HydrabotThe Modular Electro-Hydraulic Robot Arm Abed Alnaif Group 3 4A Mechatronics Engineering University of Waterloo November 17, 2008

  2. 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

  3. 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

  4. 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

  5. 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

  6. Design Overview: Design Methodology • Design methodology, in chronological order: • Choose type of actuator • Choose sensor • Choose valve • Design structure Modular Electro-Hydraulic Robot Arm

  7. Design Overview: Actuator Selection • Hydrostatic (no actuators) • Very cheap • Difficult to control (no stiffness) Modular Electro-Hydraulic Robot Arm

  8. 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

  9. 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

  10. Design Overview: Valve Selection • Directional valve • Controls direction of flow only (not magnitude of flow) Modular Electro-Hydraulic Robot Arm

  11. 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

  12. 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

  13. 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

  14. Design Overview: Structure Design (2) Isometric View Side View Modular Electro-Hydraulic Robot Arm

  15. 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

  16. 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

  17. 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

  18. Design Assessment Amtec PowerCube servo-motor and gear box: Modular Electro-Hydraulic Robot Arm

  19. 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)

  20. The Possibilities… Questions? Modular Electro-Hydraulic Robot Arm

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