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Precise, Reliable and Robust Free Piston Engine with Virtual Crankshaft

Technology #20120205-20130254

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Fluid Power HydraulicsPiston MotionFree Piston Engine with Virtual Crankshaft
Zongxuan Sun, PhD
Department of Mechanical Engineering, School of Science and Engineering
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Managed By
Kevin Nickels
Technology Licensing Officer 612-625-7289
Patent Protection

US Patent Pending 2013-0298874

US Patent Pending 2016-0032820

PCT Patent Application Filed

Free Piston Engine Provides Precise Piston Motion Control

A real-time active piston motion control acts as the virtual crankshaft in a free piston engine to coordinate the combustion and the load. The control system forces the piston to follow a pre-determined trajectory by sensing the combustion event and the load in real-time. This allows the piston motion to be precisely controlled in real-time, which is difficult with the current free piston engine technologies.

MN-IP Try and Buy
  • Trial period is up to 24 months
  • Trial fee is $20,000 for a 24 month license
  • Trial fee is waived for MN companies or if sponsoring $50,000+ research with the University
  • No US patent fees during Try period
  • $30,000 conversion fee (TRY to BUY)
  • Royalty rate of 3% (2% for MN company)
  • Royalty free for first $1M in sales

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** Contact Kevin Nickels for specific details. **

Efficient Free Piston Engine and Fluid Power Package

The design offers increased fuel efficiency by adjusting the engine compression ratio in real time. Potential applications of the free piston engine and high pressure fluid power package include off road machinery, agricultural equipment, on-highway vehicles and smaller mobile applications (5-10 kW). The proposed method is also applicable to free piston engine linear alternator.


  • Higher fuel efficiency by adjusting the engine in real time.
  • The invention offers precise control of piston motion and robust engine operation.
  • Increased power density.