According to Aristotle’s Politicswritten in 360 BC, a society is worth existing if it provides freedom and prosperity to its people. While engineering is arguably one of the main agents of prosperity, the shortage of energy is a major concern on the path to a better quality of life. Electric energy represents about 40% of all energy used today as it enhances industrial productivity and causes less pollution. Electric motion control in industry is ultimately related to electric energy conversion and its flow control.
Linear electric (electromagnetic) machines (LEMs) realize the conversion of electrical energy to linear motion mechanical energy (or vice versa) directly through electromagnetic forces. Linear motion is very common in industry. LEMs were invented in the nineteenth century; however, they gained prominence at the industrial level only in 1960 due to the necessity of using power electronics for control (in the absence of any mechanical transmission).
Typical LEM applications in industry are as follows:
• Magnetically levitated vehicles (e.g., Shanghai’s “Transrapid”)
• Urban people movers (e.g., Dallas-Forth Worth’s Airline Commuter)
• Linear electric motor–driven refrigeration compressors
• X–Y planar motion industrial platforms
• Espresso coffee steamer drivers
• Microphones and loudspeakers in cellular phones
• Digital camera zoomers
• Linear electric generators for deep space missions
• Hotel locker solenoids
• Electric power switch solenoids LEMs are characterized by
• Low initial cost
• Higher reliability
• Adhesion—less propulsion (lighter vehicles: lower Wh/passenger/km)
• Better position tracking (no backlash).