CONTROL SYSTEM AND METHOD FOR PREVENTING DESTRUCTIVE COLLISIONS IN FREE PISTON MACHINES
First Claim
1. An improved control system for a free piston machine, having a piston reciprocating in linear oscillation within a cylinder, the cylinder having at least one cylinder end structure, the machine also having a negative feedback control system controlling a piston force, the control system including a summing junction to which a feedback signal and a control input signal are applied for deriving an error signal, wherein the improvement comprises:
- (a) a collision detector for detecting a collision of the piston against the cylinder end structure and generating a signal at an output in response to a detected collision;
(b) a signal generator for generating a perturbation signal and having its input connected to the output of the collision detector and its output connected to the summing junction.
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Accused Products
Abstract
In a free piston machine, initial collisions of the piston with structures at the end of the cylinder are detected and generate a change in the magnitude of a perturbation signal, which is applied to the summing junction of a closed loop feedback control system controlling a piston force. The change is applied in a direction to reduce piston amplitude. In embodiments in which maximization of piston amplitude is desirable, the magnitude of the perturbation signal is also varied in the opposite direction in the absence of collisions to increase piston amplitude of oscillation so that operation then hunts between initial nondestructive collisions and a non-colliding maximum amplitude of piston oscillation.
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Citations
20 Claims
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1. An improved control system for a free piston machine, having a piston reciprocating in linear oscillation within a cylinder, the cylinder having at least one cylinder end structure, the machine also having a negative feedback control system controlling a piston force, the control system including a summing junction to which a feedback signal and a control input signal are applied for deriving an error signal, wherein the improvement comprises:
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(a) a collision detector for detecting a collision of the piston against the cylinder end structure and generating a signal at an output in response to a detected collision;
(b) a signal generator for generating a perturbation signal and having its input connected to the output of the collision detector and its output connected to the summing junction. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for preventing destructive collisions in a free piston machine having a piston reciprocating in linear oscillation within a cylinder, the cylinder having at least one cylinder end structure, the machine also having a negative feedback control system controlling a piston force, the control system summing a feedback signal and a reference input signal and deriving an error difference signal, the method comprising:
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(a) summing a perturbation signal with the feedback signal and the reference input signal;
(b) detecting a collision of the piston against the cylinder end structure and generating a signal at an output in response to a detected collision; and
(c) varying the magnitude of the perturbation signal in a direction which reduces piston amplitude in response to each detection of a collision. - View Dependent Claims (11, 12, 13, 14, 15, 17, 19)
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16. An apparatus for preventing destructive collisions in a free piston machine having a piston reciprocating in linear oscillation within a cylinder, the cylinder having at least one cylinder end structure, the machine also having a negative feedback control system controlling a piston force, the control system summing a feedback signal and a reference input signal and deriving an error difference signal, the apparatus comprising:
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(a) means for summing a perturbation signal with the feedback signal and the reference input signal;
(b) means for detecting a collision of the piston against the cylinder end structure and generating a signal at an output in response to a detected collision; and
(c) means for varying the magnitude of the perturbation signal in a direction which reduces the piston amplitude in response to each detection of a collision.
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18. An apparatus for detecting collisions in a free piston machine, the collisions generating mechanical vibrations in a characteristic frequency range, the apparatus comprising:
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(a) a mechanical vibration detector having an output for an electrical signal representing a detected mechanical vibration;
(b) a filter connected to the output of the vibration detector and having a passband at the characteristic frequency range; and
(c) means for comparing the magnitude of the output from the filter to a reference representing the output of the filter in the absence of collisions and having an output for changing in response to the filter output exceeding the reference and thereby signaling the detection of a collision.
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20. A method for detecting collisions in a free piston machine, the collisions generating mechanical vibrations in a characteristic frequency range, the method comprising:
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(a) detecting mechanical vibrations of the machine by generating an electrical signal representing the detected vibrations;
(b) filtering the detected mechanical vibration signal by passing the characteristic frequency range; and
(c) comparing the magnitude of the filtered signal to a reference representing the filtered signal in the absence of collisions and signaling the detection of a collision in response to a filtered signal exceeding the reference.
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Specification