Hydrabot The Modular Electro-Hydraulic Robot Arm Abed Alnaif Group 3 4A Mechatronics Engineering University of Waterloo November 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: o Modular robot with greater payload and lesser limitations on number of modules 2 Modular Electro-Hydraulic Robot Arm

Goals & Objectives Goals: o 2 modules built o Simple control algorithm developed Objectives: o Should perform better than currently available modular robots in at least one of these categories: o Cost o Size o Payload 3 Modular Electro-Hydraulic Robot Arm

Constraints & Criteria Constraints: o $1500 / module o Should support at least 15 modules Criteria: o Size o Load Capabilities o Controllability (ease and accuracy of control) 4 Modular Electro-Hydraulic Robot Arm

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 valves o Oil leaks o Nonlinear control o Noisy 5 Modular Electro-Hydraulic Robot Arm

Design Overview: Design Methodology Design methodology, in chronological order: 1.Choose type of actuator 2.Choose sensor 3.Choose valve 4.Design structure 6 Modular Electro-Hydraulic Robot Arm

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

Design Overview: Actuator Selection (2) Hydraulic Rotary Actuators o ~ $800 (outside constraints) o Direct rotary output Hydraulic Cylinders o ~ $150 o Need to convert linear to rotary motion 8 Modular Electro-Hydraulic Robot Arm

Design Overview: Sensor Selection Two ways of sensing module positions o Measure piston position Off-the shelf Very expensive ( ~ $700 ) o Rotary potentiometer Cheap 9 Modular Electro-Hydraulic Robot Arm

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

Design Overview: Valve Selection (2) Servo valve o Controls both direction and magnitude of flow o Very good, fast performance o Linear flow vs. command signal o Very, very expensive (beyond budget constraints) 11 Modular Electro-Hydraulic Robot Arm

Design Overview: Valve Selection (3) Proportional Valve o Similar to directional valve, except it accepts an analog command signal to solenoids Allows valve to throttle flow according to command signal o Worse 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 13 Modular Electro-Hydraulic Robot Arm

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

Design Overview: Structure Design (3) Internal Oil Routing Red = Pressure (from pump) Blue = Return (to reservoir) Orange and Green = Actuators 15 Modular Electro-Hydraulic Robot Arm

Design Specifications Dimensions: 206x386 mm Weight: 6.6 kg Torque (at 45° rotation and with cylinders pulling): 1657 N-m Max number of modules: mm 206 mm 16 Modular Electro-Hydraulic Robot Arm

Design Feature: Reconfigurable Each module adds 1 degree of freedom Modules are reconfigurable to allow flexibility in shape of robot arm Parallel AxesPerpendicular Axes 17 Modular Electro-Hydraulic Robot Arm

Design Assessment CategoryHydrabotAmtec PowerCube Meets Project Constraints? Cost$1500Much lessYes Size206 x 386 mm90 x 220 mmYes Weight6.6 kg5.6 kgYes Torque1657 N-m142 N-mYes Max # of modules Yes Amtec PowerCube servo-motor and gear box: 18 Modular 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? 20 Modular Electro-Hydraulic Robot Arm