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Jussi Suomela HUT/Automation 1
Actuators for Mobile RobotsActuators for Mobile Robots
Actuators are used in order to produce mechanical movement in mobile robot.
Jussi Suomela HUT/Automation 2
Servo SystemServo System
Servo is mechanism based on feedback control. The controlled quantity is mechanical.
Jussi Suomela HUT/Automation 3
Properties of Servo Properties of Servo
high maximum torque/force allows high (de)accelerationhigh zero speed torque/forcehigh bandwidth provides accurate and fast controlworks in all four quadrantsrobustness
Jussi Suomela HUT/Automation 4
Actuator TypesActuator Types
ElectricalHydraulicPneumaticOthers
Jussi Suomela HUT/Automation 5
Electrical ActuatorsElectrical Actuators
easy to controlfrom mW to MWnormally high velocities 1000 - 10000 rpmseveral typesaccurate servo controlideal torque for drivingexcellent efficiencyautonomous power system difficult
ElectricElectric actuatorsactuators
Mainly rotating but alsolinear ones are availablelinear movement with gearor with real linear motor
Jussi Suomela HUT/Automation 7
Electrical Actuator TypesElectrical Actuator Types
DC-motorsbrushless DC-motorsasynchronous motorssynchronous motorsreluctance motors (stepper motors)
Jussi Suomela HUT/Automation 8
DCDC--MotorsMotors
simple, cheapeasy to control (I = T)1W - 1kW can be overloadedbrushes wearlimited overloadingon high speeds
DCDC--motormotor controlcontrol
Controller + H-bridgePWM-controlSpeed control bycontrolling motorcurrent=torqueEfficient smallcomponentsPID control
Jussi Suomela HUT/Automation 10
Brushless DCBrushless DC--Motors Motors (pm synchronous motor) (pm synchronous motor)
no brushes no wearing parts high speedscoils on cover => better coolingexcellent power/weight ratiosimpleController needs both speed and angle feedbackmore complicated controller From small to medium power (10W – 50kW)In hub-motors
PM PM BrushlessBrushless HubHub motormotorCharacteristics:Outer rotor with permanent magnets Inner stator with fluid-cooled single coils Simple mechanical and electrical design
– no rotating electrical parts (no brushes or sliding contacts) – no complicated windings – large air gap
Power supply by current inverters using most recent IGBT technology Microprocessor control with diagnostics of all propulsion data Advantages:Extremely high torque and power ratings: 4 to 10 times better torque and power values compared to conventional electrical machines Easy to integrate due to the small volume Highest efficiency values under all operating conditions Maintenance-free Simple and accurate control of all operational conditions Typical Applications:Road vehiclesRail vehicles Industrial drives which require maximum torque with lowest possible dimensions
Adopted from: http://www.magnetmotor.de/
Jussi Suomela HUT/Automation 12
Asynchronous MotorsAsynchronous Motors
very simple, very popular in industry0,5kW - 500kWMore difficult to control (frequency)nowadays as accurate control as DC-motorsIn mobile machines also (5kW )
Jussi Suomela HUT/Automation 13
Structure of an AsStructure of an As--motormotor
Jussi Suomela HUT/Automation 14
SyncSynchhronousronous MotorsMotors
usually big 100 kW -XXMWalso small ones ~ brushless DC-motors from 50W to 100 kWcontrolled like as-motors (frequency)shipsindustry Mobile machines
ABB synchronous motor1-60 MW
Jussi Suomela HUT/Automation 15
Reluctance (Stepper) MotorsReluctance (Stepper) Motors
angle controlslowusually no feedback usedaccurate positioningwith out feedback not servoseasy to control
Jussi Suomela HUT/Automation 16
Principle of Stepper MotorPrinciple of Stepper Motor
Jussi Suomela HUT/Automation 17
Servo Control of an Electrical Servo Control of an Electrical MotorMotor
Jussi Suomela HUT/Automation 18
Hydraulic ActuatorsHydraulic Actuators
linear movementbig forces without gearsactuators are simplein mobile machinesBad efficiencymotor, pump, actuator combination is lighter than motor, generator, battery, motor & gear combination
HydraulicHydraulic actuatorsactuators
Jussi Suomela HUT/Automation 20
Hydraulic motorHydraulic motor
Jussi Suomela HUT/Automation 21
Hydraulic ValvesHydraulic Valvesservo valves– complicated structure, expensive– good control
proportional valves– simple, cheap– robust– more difficult to control
Digital hydraulics, new!– several fast on/off valves (2n)– digital control of the flow
Jussi Suomela HUT/Automation 22
Servo ValveServo Valve
Jussi Suomela HUT/Automation 23
Proportional ValveProportional Valve
Jussi Suomela HUT/Automation 24
Pneumatic ActuatorsPneumatic Actuators
like hydraulic except power from compressed airfast on/off type tasks big forces with elasticityno leak problems
Jussi Suomela HUT/Automation 25
Other ActuatorsOther Actuators
piezoelectricmagneticultra soundSMAinertial
ExamplesExamples
ArskaArska
WorkpartnerWorkpartner
Shape Memory Alloy Robot Shape Memory Alloy Robot