Terminology
- Bus System – Communication System between a controller and several attached devices e.g. Can
- Load – a load connected to the actual actuator [Watt]
- Piston – an pneumatic or hydraulic actuator for linear movements • Position control – moving an actuator by position informations
- Rotor – moving part of an electric motor (anchor)
- Rpm – revolutions per minute
- Speed control – moving an actuator by actual speed values
- Stator – Static part of an electric motor (coil)
- Shaft – connection of a rotating or a linear actuator to their environment
- Torque – M = r * F / torque = position vector x force vector [kg m^2 s
Motor
Example
Direct current motors (DC-motors)
- Up to 98% efficiency
- Power cord or battery
Brush motor:
- cheap
- Mature technology
- Sparking / high-frequency interferences
- Life limit – carbon brushes
Brushless motor:
- More efficient / less heat
- Less wear
- More power per weight
- Requires a controller
Stepper Motors
Revolutions will be made in an amount of steps (degree), not as a constant movement, exact positions can be achieved
Bipolar: 2 coils 4 connections (more power per motor-volume)
Unipolar: at least 5 connections, simpler control
Reluctance motor
- toothed soft iron structured rotor
- No permanent magnets
- Free magnetic flow, no magnetic field after switched off
Permanentmagnet motor
- Permanentmagnet on the shaft / Stator made of soft iron
- Moment of rest
- Lower resolution in comparison to ther reluktance motor
Hybridmotor
- Permanentmagnet and toothed soft iron core on the shaft
Servos
Analog servos
- Low power consumption
- Low price
Digital servos
- Faster positioning time
- Higher resolution
- Partly programmable
PWM-control
- Common for hobby servos
- Servo elektronics regulate the actor (potentiometer) against the motor position
- The pulse width of the control signal regulates the target position
- Various variations on pulse widths and travel ranges
Link to original
Hydraulics
Energy density:
210 bar (Industry standard)
500 barAdvantages
- High power density
- Good controllability
- Good timing behaviour due to low inertia
- Simple and reliable protection against overload
- Good energy transmition over medium distances
- Good lubrication and dissipation of the heat loss through the pressure transmission medium
Disadvantages
- High energy consumption
- High weight of drive and control elements
- Losses from friction and internal leakage
- Sensitive to dirt
- Fire hazard
Motor
Link to original
Pneumatics
Advantages
- The forces and speeds of the cylinders are infinitely variable.
- High achievable working speeds (standard cylinder 1500 mm / s; high-performance cylinder 3000 mm / s, engines up to 100.000 min-1)
- Compressed air devices can be overloaded to a standstill without damage.
- Compressed air can be stored in pressure tanks.
- With pneumatics, waste heat is only generated centrally at the compressor, not at decentralized electric drive units.
- Air is free of charge and always available (however, energy consumption at the compressor is required to compress the air; the efficiency is comparatively low).
- Clean, environmentally friendly medium.
- The exhaust air can escape directly into the environment, return lines can be omitted.
- Explosion safety of the medium is guaranteed.
- Compressed air is insensitive to magnetic impulses.
- Sealing and throttling technology possible (sine cylinder).
Disadvantages
Link to original
- Without fixed stops, precise positions are not possible due to the compressibility of the air.
- Compressed air escapes causing noise. Countermeasures are silencers.
- Compressed air treatment is required to remove dirt and moisture.
- Gases are compressible. Bursting pneumatic accumulators release large gas volumes. This can have a devastating effect, especially in closed rooms. For this reason, pneumatic containers are subject to regular inspection (costs) from a certain size.
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