Control method of the position of a solenoid valve using dithering

Apparatus, comprising an automatic manual transmission for a vehicle, comprising:

• a driving hydraulic circuit having at least one solenoid valve;
• and
• a control unit of the transmission configured to control the position of the solenoid valve, the control unit comprising:
• a target current circuit configured to determine a target current (IOBJ), through the solenoid valve, expressed in digital form with a given minimum quantization interval (Δmin);
• an adding circuit configured to add to the target current (IOBJ) a dithering square wave (IDITH) that has a high frequency of oscillation;
• a voltage control circuit configured to control a voltage (V) applied to the solenoid valve to make a current (I) through the solenoid follow the target current (IOBJ) added to the dithering square wave (IDITH);
• a jiggling circuit configured to jiggle the dithering square wave (IDITH) with a frequency that is a sub-multiple of the maximum frequency of variation of the current (I) through the solenoid valve;
• and
• an amplitude varying circuit configured to vary the amplitude of the dithering square wave (IDITH) for a fraction of the period (TDITH) of the dithering square wave (IDITH) and by an amount equal to the minimum quantization interval (Δmin) of the target current (IOBJ) to temporarily determine a deviation of a mean value of dithering square wave (IDITH) compared to zero and to provide a corresponding variation of the mean value of the target current (IOBJ) by an amount equal to a fraction of the minimum quantization interval (Δmin).

Control method to control a position of a solenoid valve using dithering, the control method comprising:

• determining a target current (IOBJ) through the solenoid valve that is expressed in digital form with a given minimum quantization interval (Δmin);
• adding to the target current (IOBJ) a dithering square wave (IDITH) which has a high frequency of oscillation;
• controlling a voltage (V) applied to the solenoid valve to make a current (I) through the solenoid follow the target current (IOBJ) added to the dithering square wave (IDITH);
• jiggling the dithering square wave (IDITH) with a frequency that is a sub-multiple of the maximum frequency of variation of the current (I) through the solenoid valve;
• and
• varying the amplitude of the dithering square wave (IDITH) for a fraction of the period (TDITH) of the dithering square wave (IDITH) and by an amount equal to the minimum quantization interval (Δmin) of the target current (IOBJ) to temporarily determine a deviation of the mean value of dithering square wave (IDITH) compared to zero and therefore get a corresponding variation of the mean value of the target current (IOBJ) by an amount equal to a fraction of the minimum quantization interval (Δmin).