robotic actuators - university of maryland · robotic actuators enae 788x - planetary surface...

Robotic Actuators ENAE 788X - Planetary Surface Robotics

U N I V E R S I T Y O FMARYLAND

Robotic Actuators

• Taxonomy of Prime Movers • Types of Electric Motors • Brakes • Transmissions • Bearings • Seals

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© 2018 David L. Akin - All rights reserved http://spacecraft.ssl.umd.edu

http://spacecraft.ssl.umd.edu



Fundamental Elements of Robotics

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SensingPlanning

and Reasoning

Actuation

Environment



Mechatronics

• “Smart components” • Combination of (or technologies for)

– Sensors – Actuators – Structures and mechanisms – Processors and control systems

• Subsumes microelectromechanical systems (MEMS)

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Prime Mover Taxonomy

• Electrical – Direct Current – Alternating Current

• Non-Electrical – Hydraulics – Pneumatics – Chemical – Thermal – Stored Energy

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Hydraulics and Pneumatics

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Hydraulic Spool Valve Schematic

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Hydraulic System Schematic

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Pneumatic Actuator Cutaway

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Brushed DC Motor Schematic

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DC Brushed Motor Schematic

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Brushed DC Motor Commutator

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DC Brushed vs. Brushless Motors

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Brushless DC Motor

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Brushless Outrunner Motor

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DC Brushless Motor Schematic

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Basic DC Motor Drive Characteristics

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Effects of Temperature on DC Motors

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Effects of Temperature on DC Motors

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Speed as a Function of Torque

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Standard DC Motor Characteristics

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Motor Power

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P = ⌧!

P = ⌧ (!NL + E⌧) = ⌧!NL + E⌧2

! = E⌧ + !NL (E < 0)

dP

d⌧= !NL + 2E⌧ = 0

⌧max power

= �!NL

2E



DC Motor Power and Efficiency

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Standard Motor Specifications

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Typical DC Motor Specification

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Axial Flux Motor

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Stepper Motor Exploded Image

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Stepper Motor Schematic

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Gearhead Motor Cutaway

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Gear Forms

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Gearing Calculations

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Gear ratio ⌘ N

⌧output

= N⌘gear

⌧input

!output

=!input

N

Ioutput

= N2Iinput

⌧ = I!̇ =) I =⌧

!̇

Ioutput

=⌧output

!̇output

Ioutput

=N⌘

gear

⌧input

!̇input

N

Ioutput

= N2⌘gear

Iinput

!̇output

=!̇input

NFor ideal gearing,



Spur Gears

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Spur Gear Parameters

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Helical Gears

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Planetary Gears

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Bevel Gears

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Bevel Gear Kinematics

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Automotive Differential Schematic

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Automotive Differential (more realistic)

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Worm Gear

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Chain Drives

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Chain Drive with Idler

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V-Belt Drive

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Toothed Belt Drive

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Rack and Pinion Gears

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Screw Drive Schematic

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Linear Actuator Cutaway

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Cup-Style Harmonic Drive

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Pancake Harmonic Drive

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Shallow-Cup Harmonic

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Operating Principle of Harmonic Drives

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Actuator Mass Estimating Relations

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mact = 0.6071⌧peak � 0.2796Speak + 2.5067

mact ⌘ Actuator mass <kg>⌧peak ⌘ Peak actuator torque <N-m>

Speak ⌘ Peak actuator speed <kRPM>

Toutput

⌘ Peak output torque<N-m>

Mharmonic

⌘ harmonic drive mass<kg>

Mharmonic

= 0.0078⌧output



Ball Bearings

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Types of Bearings

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Angular Contact Bearing

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Dual-Row Angular Contact Bearing

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Thrust Bearing

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Tapered Roller Bearings

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Wheel Hub Cutaway

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Ideal Bearing Applications

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O-Ring and Groove

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Lip Seals

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Spring Energized Seals

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Labyrinth Seals

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robotic actuators - university of maryland · robotic actuators enae 788x - planetary surface...

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