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Biologically Inspired Robotics
Permanent
magnet
Permanent magnet
Permanent
magnet
Rotor
Rotor
Rotor
Stator
Stator
Interior Rotor
Exterior Rotor
Axial Rotor
Stator
FIGURE 13.4
Three basic BLPM DC motor configurations.
To design a motor that produces sufficient torque while having good
performance, several design factors should be considered. The number of
stator slots and magnet poles is one of the considerations in motor design.
The number of poles is inversely proportional to the maximum speed of
rotation. By increasing the number of poles, the overall diameter can be
reduced.
Cogging force is a kind of magnetic force between the stator and permanent
magnets, which usually causes oscillation during rotation. For conventional
motor design, many efforts have been made to reduce the cogging force.
However, in this design, the magnetic force between the stator and permanent magnets has a special function. When there is no current applied on the
stator coils, this magnetic interaction force holds the rotor still and plays an
important role in the operation as a brake.
Increasing the cogging force improves the brake function but impairs the
dynamic performance of motor function. Hence it is a trade-off to determine
the suitable magnetic force between the stator and permanent magnets. In
this design, fractional slots/poles were adopted to minimize the cogging
force while maintaining an appropriate magnetic force between stator and
permanent magnets.
In order to provide sufficient active torque, the motor needs to produce an
electromagnetic torque as large as possible. There are some factors affecting
the value of the torque, such as grade of the permanent magnet, permeability of the magnetic material, windings of the coil, and air gap. In the motor,
magnetic flux passes between the stator and permanent magnets through
the air gap. The output torque or the electromagnetic torque is proportional
to the flux in it. The electromagnetic torque provided by the motor is calculated with the following equation:
T M = C T Φ 0 I M
(13.1)
Biologically Inspired Robotics
Permanent
magnet
Permanent magnet
Permanent
magnet
Rotor
Rotor
Rotor
Stator
Stator
Interior Rotor
Exterior Rotor
Axial Rotor
Stator
FIGURE 13.4
Three basic BLPM DC motor configurations.
To design a motor that produces sufficient torque while having good
performance, several design factors should be considered. The number of
stator slots and magnet poles is one of the considerations in motor design.
The number of poles is inversely proportional to the maximum speed of
rotation. By increasing the number of poles, the overall diameter can be
reduced.
Cogging force is a kind of magnetic force between the stator and permanent
magnets, which usually causes oscillation during rotation. For conventional
motor design, many efforts have been made to reduce the cogging force.
However, in this design, the magnetic force between the stator and permanent magnets has a special function. When there is no current applied on the
stator coils, this magnetic interaction force holds the rotor still and plays an
important role in the operation as a brake.
Increasing the cogging force improves the brake function but impairs the
dynamic performance of motor function. Hence it is a trade-off to determine
the suitable magnetic force between the stator and permanent magnets. In
this design, fractional slots/poles were adopted to minimize the cogging
force while maintaining an appropriate magnetic force between stator and
permanent magnets.
In order to provide sufficient active torque, the motor needs to produce an
electromagnetic torque as large as possible. There are some factors affecting
the value of the torque, such as grade of the permanent magnet, permeability of the magnetic material, windings of the coil, and air gap. In the motor,
magnetic flux passes between the stator and permanent magnets through
the air gap. The output torque or the electromagnetic torque is proportional
to the flux in it. The electromagnetic torque provided by the motor is calculated with the following equation:
T M = C T Φ 0 I M
(13.1)