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Motori Lineari. Linear Motors. video. Disadvantages : Limited stroke Space occupancy Cost Complex to build/assemble (basically new know-how needed). Advantages : Precise High forces Few parts. Types of linear actuators: Electrical Linear Motors Pneumatic Cylinders Solenoids.

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linear motors

Motori Lineari

Linear Motors


  • Disadvantages:
    • Limited stroke
    • Space occupancy
    • Cost
    • Complex to build/assemble
    • (basically new know-how needed)
  • Advantages:
    • Precise
    • High forces
    • Few parts
  • Types of linear actuators:
    • Electrical Linear Motors
    • Pneumatic Cylinders
    • Solenoids
linear electric motors

Motori Lineari

Linear Electric Motors
  • Advantages:
    • Performances
    • Compact
    • IP65-67 animazione1animazione2
  • Disadvantages:
    • Cost
    • Limited Stroke
    • Complex Assembly

and New Know How

pneumatic cylinders

Motori Lineari

Pneumatic Cylinders
  • Advantages:
    • Force
    • Cost
  • Disadvantages:
    • Low Accuracy, Repeatability
    • Limited Stroke
    • “Air supply” issue

Motori Lineari

  • Advantages:
    • Cost
    • Compact
    • High Speed
  • Disadvantages:
    • Very low accuracy,

repeatability (bang-bang)

linear motors performances costs

Motori Lineari

Linear Motors: Performances & Costs

Cost, Performance





The best when concerning kinematics


The best when concerning force

The best when concerning cost,

The worst when concerning accuracy

differences with respect to rotary motors 1

Motori Lineari

Differences with respect to rotary motors (1)
  • Suppliers of linear motors
  • sell force [N].
  • Suppliers of linear encoders
  • sell accuracy [mm and bandwidth: Hz].
  • Then it’s necessary to assemble it,
  • put a case, maybe a brake, etc..
differences with respect to rotary motors 2

Motori Lineari

Differences with respect to rotary motors (2)
  • In a linear motor only the windings that are close to the slider works, then, with respect to a rotary motor, with the same weight, the avilable force is lower.
  • In other words, while in a rotary motor all the windings and permanent magnets work, in the linear one is not the case.
  • The rod-like motors reduce the problem, but they don’t eliminate it.
  • Avilable forces: 5-8N/cm2 of gap.
which applications do fail

Motori Lineari

Which applications do fail?
  • If the machine is limited by mechanical resonances, insufficient stiffness, the linear motor will not provide any improvement.
  • If the control system is not fast enough, it will be the bottle neck and the full machine will not have desired performences.
  • If the deisred stiffness is high and the bandwidth limited, the gearbox is the only solution.
  • If the accuracy offered by the position sensor is not needed, then the linear motor is an expensive solution.

Motori Lineari

The competitive solution: positioningX cartesian axis L=2000 mm, 50 kg load, pinion/rack or linear motor?
  • Motor cost 5 Nm = 100
  • Gearbox cost = 150
  • Encoder in the motor =30
  • Rack and pinion =120
  • Alignments, mounting procedure =100
  • Result: 2 m/sec, 1g,
  • settling time ~ 100 msec, accuracy ~0.1 mm
  • Total cost = 500
  • Motor cost 400/1000 N = 300
  • Magnetic encoder cost = 50
  • Alignments,
  • mounting procedure = 50
  • Result : 4 m/sec, 2g,
  • settling time=20 msec,
  • accuracy 0.02 mm
  • Total cost = 400
  • And each year the linear motors cost decrease…
tubolar linear motors
Tubolar Linear Motors:
  • Symmetrical Design
  • Compact cross section, similar to ball screw
  • 1mm nominal anular airgap (Non-critical gap for easy installation)
  • Enclosed Magnets & Coils
  • Not easily damaged
  • Force transferred directly to load
  • High mechanical stiffness
  • Integral Heat Sink Fins (No added cooling required)

Copley (PullTab)

Thrust Tube

sensor less linear motors
Sensor-less linear motors
  • They replace the normal external position encoder (normally up to half the total cost of the complete motor) with integral Hall position sensing
  • Accuracy is, of course, worse tha encoder-equipped motors: 0.1 - 0.25mm typical


Rod-like motor


linmot sw tool
LinMot SW Tool

C=ki; I=(V-kw)/R

torque motors

Motori Coppia

Torque Motors
  • Torque Motors (Motori Coppia) are just motors providing huge torques, generally with a very high pole pairs number and in direct-drive application with very low speed
  • How to go beyond the torque/dimensions limit today reached by the permanent magnets brushless motors?
  • Conventional Motor: windings on several slots, inserted in the slot in chaotic way.
  • Epicyclical Motor: each teeth has one-and-only-one winding around it, very short motor length

Motori Coppia

Epicyclical Motors (Motori Epiciclici)


Motori Coppia

Existing Technologies

  • Single teeths, micro-impressed,
  • wind-up and laser soldered
    • Layered winding on the teeth
    • Wounded teeths are joined and re-soldered
    • All connections are done outside
    • Complex process.

High cogging. Low teeth number.

  • Star-shaped stator (open toward the external side) done with metal sheets, cut and pasted
    • Complex process.

Low cogging.

  • Conventional Stator, windings inserted in the slot
    • Complex (often manual) operation
    • Not efficient slot filling
    • Used in big-diamater motors.

High cogging.


Direct-Drive Torque Motors

Motori Coppia

  • With brushless PM technology, high number of poles, low speed, they provide high performances if integrated in the machine
  • From 10 to 37000 Nm
  • From 85 to 570 mm diameter