Electrical motors

Types of electrical motors

Brushed motor classification (a.k.a. Universal motor)

For brushed motor, the windings can be on rotor or stator or both (avoiding magnets). Usually it is composed of stationary magnets and rotor coils.

• rotor with armature
• ironless rotor (for better acceleration)

Brushless motor classifications

A brushless motor is composed of stationary windings and magnetic rotor.

Magnetic forces

• Permanent Magnet Synchronous Motor (PMSM)
  • Surface Mounted (SM) (27.2 Nm/Kg)
  • Internal Permanent Magnet (IPM) (56.6 Nm/Kg)
• Switched Reluctance Motor (SRM) (8400 Nm/m3)

IPM can be considered as hybrid as it takes advantage of magnet and reluctance.

Magnetic field orientation

• radial (traditional)
• axial (smaller diameter, higher torque)

Switched Reluctance Motor

• Pros
  • Good at high speed
  • No rare earth
• Cons
  • Torque ripple
  • Lower torque in quasi-static mode
  • Less efficient than Permanent Magnet Motor

Controller of brushless electrical motors

For generating the turning field, the driver could be either:

• 3 half H-bridge (i.e. three phases)
• 2 full H-bridge

An optimal BLDC motor control enables:

• better dynamics
• no missing steps
• energy efficient
• backdrivable
• enable motor synchronization (CNC or multi-motor-joint)

The project SimpleFOC (Field Orientation Control) provides a solution for this problematic.

Embedded electronics

Embedded key technologies:

• Powerful microcontroller like STM32
• ROS2 maturity
• mROS: micro-ROS without agent
• Zephyr-OS, Tock-OS
• Ethernet 10BASE-T1S and 100BASE-T1
• SimpleFOC (Field Orientation Control)

Enable motor synchronization for:

• CNC
• robot
• mechanical joint with multi-motors

multi-motor joint

advantages of mechanical join with multi-motors

• [+] distributed efforts
• [+] spread thermic, better cooling
• [+] scalable
• [+] use standard high-tech/mid-range components
• [+] easier maintenance
• [+] easier manufacturing standardization
• [+] smoother control
• [+] no backlash
• [-] complex motor driver
• [+] distributed power
• [+] improve split between small standard high-tech and large low cost

Gimbal

Gimbal is a two axis mechanism for controlling pan and tilt orientation. It is used to stabilize and orientate camera (100g), as articulation of arm-bot (5kg) or to orientate solar panel (2000kg).