Post on 30-Mar-2015
Round-a-Bot
Jeff Fletcher Sung-Tu Ho
Jason Kloess Ranjit Raj
Steve Vozar
ME552 Design Review 3
23 November 2010
roundabot.wordpress.com[BallP Robot, ieeespectrum.org]
Holonomic Inverted Pendulum Robot
La Formule
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Project Summary Technical SpecificationsPhysical DesignMathematical ModelMajor ModulesComponent VerificationBill of MaterialsEngineering Drawings
Project SummaryRound-a-Bot: Holonomic Inverted Pendulum Mobile Robot
Project Objective:Design and build an inverted pendulum robot riding on a single ball capable of transporting a person safely in an indoor environment.
Technical SpecificationsBall size: 8.5 - 10" diameter (soccer - basket ball sized)Robot Height: 2.5 - 3 ft (table-top height)Cost: $1500 Human transport onlyOperational Environment: Indoors
Temperature: 15 - 25 ºCSurfaces: Tile, Carpet, Concrete, Brick, etc.Able to traverse slopes up to 10ºReject disturbances caused by small (~1cm) bumpsOperational Range: ~1 hr continuous battery life with ability to easily recharge (AC outlet)
Operational Speed: 2-3 mph translational (safe walking speed)Safety Features: Thermal/Over-current protection, training wheels, foot support, etc.
Physical Design (3D CAD)
Total height = 31in Transparent Items:
Shielding panels Base plate, Top PlateTop and Bottom Ring
Physical Design (3D CAD)OMNIWHEEL-to-SHAFT CONNECTION (ADAPTER HUB)
�Stock omniwheelDinner = 22.225mm
Wkey = 6.6mmSkey = 2.75mm
Shaft sizeDinner = 1/2" -0.0005 -0.0025Wkey = 1/8" +0.002"Skey = 1/16" +0.002"
Physical Design (3D CAD)MOTOR SHAFT STACK
Overall 3D model Shaft section
Physical Design (3D CAD)LOWER HALF ASSEMBLY (BASE PLATE)
Physical Design (3D CAD)FRAME STRUCTURE (CHICAGO BAR STOOL)
Base plate mountingTop plate mountingProtective sidingTraining Casters Swivel Seat
Physical Design (3D CAD)ELECTRONICS MOUNTING PLATE (TOP PLATE)
IMU mountingcRIO, H-Bridge servos, and PCB mountingWire pass through slot
Mathematical Modeling
Mathematical Modeling
Taking the Lagrangian yields:
LinearizationWe then Linearize the model around (0,0,0,0) to obtain the state-space equations for creating a state feedback controller. (Mi is from corresponding entry of the Mass Matrix)
Comparison for a step response to ball torque:
Mathematical Modeling - Controller
Controller Design LQR controller High emphasis on cylinder position Low emphasis on ball position
3000 0 0 0
0 0.003 0 0
0 0 300 0
0 0 0 300
cylinder angle
ball angle
cylinder velocity
ball velocity
Mathematical Modeling - Controller
DisturbancesPassenger movements modeled as disturbanceConstant lean: step disturbance in torqueSine or ramp function initially to better represent human motion
Mathematical Modeling - Controller
IssuesSize of motor deadband has substantial impact on controller performanceSensor noise does not affect ability to balance much but does increase control effortControl effort is related to frequency of disturbance
Future workActual controller will be designed once we have run system ID on the motorsIf needed, an inner loop will be added to control motor speed
Simulink Model
Nonlinear Dynamic System
Actuator Model
Sensor Model
Controller Simulations
Step ResponseOffset Response
DisturbancesPushGrade
Controller SimulationStep Response to 10° user lean
9 rad/s = 5.1 mph
Controller SimulationInitial 10° Cylinder offset
Controller SimulationDisturbance Response to 7.5° floor slope
Controller SimulationResponse to small bump disturbance on ground while moving
Controller SimulationResponse to 200N shove at CoM from rest
Major Modules
Overview: ChassisDrivetrainPower SupplySensorsMicroprocessor
Chassis
Stool Requirements Comfortable height to sit (2.5-3 feet, ball+robot) Not too heavy, can support 200lb person
Chicago Bar Stool
Height: 30", Base: 16x16"Weight:16 lbs Additional Features:
Two support rings lower ring: base plate upper ring: electronics plate
Swivel Seat
Electronics Plate
Supports the cRIO, IMU, H-bridge controller and the PCB voltage converter
Rectangular PVC plate selected:
Light weight(4 lbs, size:24x12x.25") Cheaper compared to a square plate Bolted to the upper ring
Components:
The cRIO, PCB mounted voltage controller and the H-bridge controller bolted to the top surface of the plate.The IMU bolted to the bottom surface exactly at the center
Lower base plateSquare Aluminum Plate (18x18x0.25")
supports batteries
Net weight of the batteries:15.7 lbs drive-train
Motors, omni-wheels and gearboxes Requirements:
capable of supporting the high loadsSufficiently strong and light
Mounting:Aluminum plate bolted to the lower ringMotors, Omniwheels bolted to bottom of the base plateBatteries bolted to the top part
Drive-trainBearing: Flanged open ball bearing(Material:Steel)
ID: 0.5", OD: 1.375",width:0.5"Dynamic radial load = 450 lbs number of bearings = 6 Total load on the bearing= 58.68 lbs Bearing load rating C = 1437.25lbf Number of cycles = 441134
Omni-Wheels:RotacasterNumber of omni-wheels = 6Diameter = 4.92 "Width = 1.06"Bore = 0.875"Load Capacity =110 lbs
Power SupplyMotor Battery Selection:
PowerStar 12V 15 A-hr battery:Type : Sealed Lead Acid BatteryCurrent: 210 A(peak)Weight: 9.26 lbsSize: 5.95x3.86x3.98"
Aux Battery Selection:PowerStar 12V 3.5 A-hr battery(2 Nos):
Type: Sealed Lead Acid BatteryCurrent:52.5 A(peak)Weight: 2.98 lbsSize: 5.28x2.64x2.62"
Wiring PracticesTwisted pair, shielded cables
Signal wires from controller to motor controllerSensor wires
Motor cable is separated from controller wiring and signal wiring Single ground to eliminate ground loops
Wire gaugeAWG gauge Max amps for chasis
wiringMax amps for power
transmission6 101 377 89 308 73 24
Table come from Handbook of Electronic Tables and Formulas for American Wire Gauge
Choice:8-Gauge Stranded THHN Cable Cost is:$0.31/ft
Sensors(IMU) 5 Degrees of Freedom IDG500/ADXL335
Cost: $44.95Output type: Analog Dimension: 20*23(mm)Sensitivity: 300mV/g and 2mV/degree/secBias voltage: 1.5V and 1.35V
Sensors(Encoder)US Digital: E7P
Cost: $57.42CPR: 180 to 720Number of channel: 2(A,B)Fits shaft diameter: 3 to 10mm
Emergency stopCost:$29.56Dimension Of Button: 22mm
Voltage RegulatorType:
78L05(5V) LP2950(3.3V)
Max output current:100mA
Input voltage range:0 to 30VPurpose:
Transform 24V battery voltage to 5 and 3.3V
Printed Circuit BoardMatching Printed Circuit Borad with 550 Connect PointsCost:$2.99
Circuit diagram
Battery Capacity Measuring Circuit
The voltage for turn on the led will be 24V and 12V
Circuit on PCB
Sensor Filter
To be implemented in Labview Based on previous M-Way team's experiences Will adjust values once we have confirmed our sensor's performance
Microprocessor - cRIO
Power Consumption: 24 V recommended power supply 2 A continuous Dimensions: 7 in x 3.5 in x 3.5 in
Microprocessor - cRIO
Main TasksControl algorithmSensor feedback PWM generatorAccelerometer / gyro filter
Microprocessor - cRIO
Modules:NI cRIO 9004: ControllerNI 9401: Digital I/ONI 9201: Analog Input NI 9401 NI 9201
Motor Controllers
Simple H H bridge circuit for 1 - 2 motor control 5 to 25 V range 1.3 oz 2.5 in x 2.25 in x .75 in (with fan) Current Sense: Vc = I*0.075
Motor Controllers
Full Bridge Half Bridge, 2 Motors Ganged Half Bridge
Continuous Current 25 A 25 A 48 A
Peak Current 45 A 45 A 70 A
Voltage Range 5 - 24 V 5 - 24 V 5 - 24 V
Component Verification: IMUAccelerometer test
Gyroscope test
Component Verification: IMU
Component Verification: Microprocessor
Getting started tutorials performed with cRIOPlan for Thanksgiving Break:
Create controller VIInterface with Simulink modelTest controller performance w/ Simulink
Engineering Drawings
Round-a-Bot Drawings
Conclusions
All major and minor component and material selections have been made
Bill of Materials completed Fabricated parts have been designed
Engineering Drawings completedMathematical model and controller confirm feasability of proposed systemPreliminary component verification and testing underway and will continue through the next weekReady to place orders pending feedback from this review