Actuators -perform work made of: signal amplifier and the transducer uses power source (electrical, hydraulic) converts it into mechanical work

Electric Motors: AC, DC, Stepper motors Structure of a DC motor: How it works: S N + DC -- DC S N + DC -- DC S N + DC -- DC (a)(b)(c) S N rotor coil commutator (split ring) + DC -- DC field magnet (fixed on stator) axle conducting brushes

DC motor properties, applications Motor typeSpeed regulationStarting torqueApplications DC seriesvery high Hoists, Gates, Trams, Trains, Bridges DC shuntlowmediumPrinting press, Machine tools, Conveyors DC compoundmediumhighPunch press, Shears, Crushers Speed regulation = (no load speed – full load speed)/no load speed

AC motors How it works: - current passed through stator coils - current creates an alternating electromagnetic field - induces an alternating current in the rotor coils - interaction of the two electromagnetic fields  driving torque Motor typeSpeedPowerApplications 1-phase AC induction ~ constant in operational range, slightly less than synchronous speed ~ 3 KW or lessAlmost all medium power pumps, fans, blowers, machines 3-phase AC induction Nearly constant over large range of loads High, > 1.5 KWHigh power pumps, machinery Electronically controlled, position feedback AC motors Servo motors

Stepper motors Rotate in discrete steps (e.g. 2  for each “step”) electronic control

Stepper motors: micro-stepping Variable strength of magnetic field for more resolution

Hydraulic actuators - Use high pressure oil - high power and forces - linear or rotary motors possible Example ? Hydraulic motor drive schematic

Pneumatic actuators A Simple Discrete Control Example (pneumatic actuation)

Actuator Characteristics accuracy: [statistical]:(mean value – actual value) precision: [statistical]:standard deviation reliability: [time-dependent, statistical]:mean failure rate

Switches and Relays Switches Relay

Encoders: measuring rotational position Incremental encoder Absolute position encoder (coded pattern) Common use: position feedback for servo-control directional incremental encoder