Linear motor controller
AssigneeFisher & Paykel Appliances Limited
InventorsIan McGill, Zhuang Tian
Life of this patent
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Abstract
A free piston gas compressor comprising a cylinder, a piston reciprocable within the cylinder and a reciprocating linear electric motor derivably coupled to the piston having at least one excitation winding. A measure of the reciprocation time of the piston is obtained, any change in the reciprocation time is detected and the power input to said excitation winding is adjusted in response to any detected change in reciprocation time.
Claims14
A free piston gas compressor comprising:
- a cylinder,
- a piston,
- said piston reciprocable within said cylinder,
- a reciprocating linear electric motor having at least one excitation winding, said motor drivably coupled to said piston and having a reciprocation period,
- means for obtaining an indicative measure of the reciprocation period of said piston,
- means for detecting any sudden change in said reciprocation period, a reduction indicative of a piston collision with the cylinder head, and
- means for reducing the power input to said excitation winding in response to any sudden change in reciprocation period.
A controller for a linear motor including a reciprocating portion and having a reciprocation period, the improvement comprising said controller being configured to:
- determine the reciprocation period of said reciprocating portion,
- detect any change in said reciprocation period, and
- adjust the power input to said linear motor in response to any detected reduction in reciprocation period.
A controller as claimed in 6 wherein said step of detecting any change in said reciprocation period includes the step of deducting said reciprocation period from a filtered or smoothed value, to provide a difference value and if said difference value is above a predetermined threshold for a predetermined period, reducing the power input to said linear motor.
A controller as claimed in 7 wherein said step of detecting any change in said reciprocation period includes the step of deducting said reciprocation period from a filtered or smoothed value, to provide a difference value and if said difference value is above a predetermined threshold for a predetermined period, reducing the power input to said linear motor.
Dependencies are inferred from the claim text.