Energy storage and conversion in free-piston combustion engines

A method of controlling a free-piston assembly in a reciprocating device during a piston cycle comprising at least a first stroke of the free-piston assembly from a first top dead center (TDC) position to a bottom dead center (BDC) position and a second stroke of the free-piston assembly from the BDC position to a second TDC position, the method comprising:

• monitoring, using processing circuitry, at least one operating characteristic of the reciprocating device;
• determining, using the processing circuitry, information indicative of an amount of energy required for the second stroke of the piston cycle based on the at least one operating characteristic;
• causing, using the processing circuitry, the driver section to convert kinetic energy of the free-piston assembly to stored energy during the first stroke based on the amount of energy;
• and
• causing at least some of the kinetic energy of the free-piston assembly to be converted to electrical energy during the first stroke and during the second stroke while causing the second stroke to be performed with no net electrical input.

A system for controlling a free-piston assembly in a reciprocating device during a piston cycle comprising at least a first stroke of the free-piston assembly from a first top dead center (TDC) position to a bottom dead center (BDC) position and a second stroke of the free-piston assembly from the BDC position to a second TDC position, the control system comprising processing circuitry configured to:

• monitor at least one operating characteristic of the reciprocating device;
• determine information indicative of an amount of energy required for the second stroke of the piston cycle based on the at least one operating characteristic;
• cause the driver section to convert kinetic energy of the free-piston assembly to stored energy during the first stroke based on the amount of energy;
• and
• cause at least some of the kinetic energy of the free-piston assembly to be converted to electrical energy during the first stroke and during the second stroke while causing the second stroke to be performed with no net electrical input.

A reciprocating device comprising:

• a free-piston assembly configured to translate during a piston cycle comprising at least a first stroke of the free-piston assembly from a first top dead center (TDC) position to a bottom dead center (BDC) position and a second stroke of the free-piston assembly from the BDC position to a second TDC position;
• a driver section configured to store energy from the free-piston assembly;
• and
• processing circuitry configured to:
• monitor at least one operating characteristic of the system;
• determine information indicative of an amount of energy required for the second stroke of the piston cycle based on the at least one operating characteristic;
• cause the driver section to convert kinetic energy of the free-piston assembly to stored energy during the first stroke based on the amount of energy;
• and
• cause at least some of the kinetic energy of the free-piston assembly to be converted to electrical energy during the first stroke and during the second stroke while causing the second stroke to be performed with no net electrical input.