Compressor and method for controlling a compressor

A compressor, comprising:

• a piston that performs a reciprocating motion within a cylinder;
• a linear motor that supplies a driving force to the piston;
• a discharge device provided at a first end of the cylinder through which a refrigerant compressed by the reciprocating motion of the piston in the cylinder is discharged;
• a sensor that detects a motor current of the linear motor;
• a controller that calculates a stroke of the piston using the detected motor current, generates a parameter associated with a position of the piston using the motor current and the calculated stroke, and controls the linear motor based on the generated parameter;
• and
• a changing device that changes a variation rate of the generated parameter before the piston reaches a virtual discharge surface (VDS) within the cylinder during the reciprocating motion, wherein the virtual discharge surface is formed by at least a portion of the discharge device facing the cylinder, and wherein the controller detects a time point at which the variation rate of the generated parameter changes, and controls the linear motor to switch a moving direction of the piston after a lapse of a predetermined time interval from the detected time point, to prevent collision between the piston and the discharge device.

A compressor, comprising:

• a piston that performs a reciprocating motion within a cylinder;
• a linear motor that supplies a driving force to the piston;
• a discharge device provided at an end of the cylinder through which a refrigerant compressed in the cylinder by the reciprocating motion of the piston is discharged;
• a sensor that detects a motor current of the linear motor;
• a controller that calculates a stroke of the piston using the detected motor current, calculates a phase difference between the motor current and the calculated stroke, and controls the linear motor based on the calculated phase difference;
• and
• a changing device that changes a variation rate of the calculated phase difference before the piston reaches a virtual discharge surface (VDS) during the reciprocating motion, wherein the virtual discharge surface is formed on at least a portion of the discharge device facing the cylinder, wherein the controller detects a time point at which the variation rate of the calculated phase difference changes, and controls the linear motor to switch a moving direction of the piston after a lapse of a predetermined time interval from the detected time point.