System and method of controlling a linear compressor

Method of controlling a linear compressor having a piston (1) driven by a linear motor and displaced inside a cylinder (2), a position-detecting circuit that emits a signal (SD) indicating displacement of the piston inside the cylinder, and an impact-detecting circuit that emits a signal (SI) indicating impact of the piston with a cylinder head,

• the method comprising the steps of:
• (a) carrying out a fine-tuning routine on the linear compressor that comprises:
• detecting an impact of the piston (1) with the cylinder head;
• measuring the drive signal at the moment of impact between the piston and the cylinder head;
• measuring the displacement signal (SD) at the moment of impact between the piston and the cylinder head;
• calculating an impact prevention limit parameter based on the measurements of the drive signal and the displacement signal (SD) upon impact of the piston with the cylinder head, wherein the impact prevention limit parameter is proportional to the variation value or the derivative value of the displacement signal (SD) at the moment of impact, and the impact prevention limit parameter is calculated by the equation
• SLOPEmin=K1×Period+K2×Power−Offset_max
• wherein:
• Slope_min is the variation value or the derivative value from the displacement signal (SD) at the moment of impact;
• K1 and K2 are respectively period and power offset constants of the drive signal;
• Period and Power are the period and power values of the drive signal at the moment of impact;
• and
• Offset_max is the impact prevention limit parameter;
• (b) carrying out a control routine on the linear compressor that comprises the steps of:
• measuring the drive signal and the displacement signal (SD);
• calculating a limit value that a control parameter of the displacement signal (SD) can assume without impact between the piston and the cylinder head, in function of the drive signal measured and of the impact prevention limit parameter calculated in the fine-tuning routine, and determining an anti-impact safety operating area for the control parameter of the displacement signal (SD);
• comparing the value measured of the parameter of the displacement signal (SD) with the limit value calculated of the control parameter of the displacement signal (SD);
• if the value measured of the control parameter of the displacement signal (SD) is within the anti-impact safety operating area, varying the drive signal to increase the efficiency of the linear compressor;
• if the value measured of the control parameter of the displacement signal (SD) is outside the anti-impact safety operating area, varying the drive signal to reduce the efficiency of the linear compressor,
• detecting the occurrence of impact of the piston with the cylinder head by analyzing the impact signal (SI), and if no impact occurred, execute the fine-tuning routine to recalculate the anti-impact fine-tuning variable, and if no impact occurred, execute the control routine.

System for controlling a linear compressor, said system comprising means for controlling the operation of the linear compressor based on a displacement signal (SD) of a piston (1) inside a cylinder (2) of the compressor, and on an impact signal (SI) of the piston (1) with a cylinder head (2), wherein the means for controlling the operation of the linear compressor calculates, based on the displacement (SD) and impact (SI) signals, at least an impact prevention limit parameter for the displacement signal (SD), which is proportional to the variation value or the derivative value of the displacement signal (SD) at the moment of impact, defining an anti-impact safety operating area of the linear compressor based on this parameter, wherein the impact prevention limit parameter is calculated by the equation

• SLOPEmin=K1×Period+K2×Power−Offset_max
• wherein:
• Slope_min is the variation value or the derivative value of the displacement signal (SD) at the moment of impact;
• K1 and K2 are respectively period and power offset constants of the drive signal;
• Period and Power are the period and power values of the drive signal at the moment of impact;
• and
• Offset_max is the impact prevention limit parameter.

Method of controlling a linear compressor, comprising controlling the operation of the linear compressor based on a displacement signal (SD) of a piston (1) inside a cylinder (2) of the compressor, and on an impact signal (SI) of the piston (1) with a cylinder head inside a cylinder (2), and during the operation control of the linear compressor, the method comprises a step of calculating, based on the displacement (SD) and impact (SI) signals, at least an impact prevention limit parameter for the displacement signal (SD), which is proportional to the variation value or the derivative value of the displacement signal (SD) at the moment of impact, and defining an anti-impact safety operating area based on this parameter, wherein the impact prevention limit parameter is calculated by the equation

• SLOPEmin=K1×Period+K2×Power−Offset_max
• wherein:
• Slope_min is the variation value or the derivative value from the displacement signal (SD) at the moment of impact;
• K1 and K2 are respectively period and power offset constants of the drive signal;
• Period and Power are the period and power values of the drive signal at the moment of impact;
• and
• Offset_max is the impact prevention limit parameter.