Solenoid driving device

A device for driving an electromagnetic actuator including a ringlike core member having an annular groove, an annular solenoid accommodated in said annular groove of said core member, and a ringlike armature member opposed to said core member with a given gap defined therebetween, said device comprising:

• a power supply;
• a switching element connected between said power supply and said solenoid in series therewith;
• a current circulating diode connected in parallel to a series circuit comprising said solenoid so that the cathode of said current circulating diode is connected between said switching element and said solenoid;
• a current detecting circuit for detecting an actual current flowing through said solenoid;
• PID computing means for computing an on-duty value and an off-duty value according to a difference between a target current and said actual current detected by said current detecting circuit, and outputting said on-duty value and said off-duty value;
• PWM duty driving means for generating a PWM duty signal according to inputting of said on-duty value and supplying said PWM duty signal to said switching element to on/off control said switching element;
• and
• a reverse voltage applying means comprising:
• a second switching element connected between the negative electrode of said power supply and said solenoid in series therewith;
• a second current circulating diode connected in parallel to a series circuit composed of said switching element and said solenoid so that the cathode of said second current circulating diode is connected between said power supply and said switching element;
• absolute value calculating means for calculating the absolute values of said on-duty value and said off-duty value;
• an inverter for inverting the signs of said on-duty value and said off-duty value;
• a NAND circuit adapted to input an output from said absolute value calculating means and an output from said inverter;
• and
• a driver circuit for on/off controlling said second switching element according to an output from said NAND circuit, wherein
• said reverse voltage applying means is capable of applying a voltage of said power supply as a reverse voltage to said solenoid according to inputting of said off-duty value when said switching element is off.

A control device for an electromagnetic actuator including a core member having a groove, a solenoid accommodated in said groove of said core member, and an armature member opposed to said core member with a gap defined therebetween, said control device comprising:

• gap detecting means for detecting said gap between said core member and said armature member;
• current detecting means for detecting an actual current flowing through said solenoid;
• a feedback controller for feedback controlling said actual current so that said actual current becomes equal to a target current;
• a feedforward controller for feedforward controlling said target current;
• and
• solenoid drive signal generating means for generating a solenoid drive signal according to outputs from said feedback controller and said feedforward controller;
• said feedback controller changing an integral term constant according to said gap detected by said gap detecting means;
• said feedback controller selects one of a plurality of predetermined integral term constants according to said gap detected by said gap detecting means;
• whereby said feedback controller selects a larger one of said integral term constants when said gap is large, and selects a smaller one of said integral term constants when said gap becomes smaller.

A control device for an electromagnetic actuator including a core member having a groove, a solenoid accommodated in said groove of said core member, and an armature member opposed to said core member with a gap defined therebetween, said control device comprising:

• gap detecting means for detecting said gap between said core member and said armature member;
• current detecting means for detecting an actual current flowing through said solenoid;
• a feedback controller for feedback controlling said actual current so that said actual current becomes equal to a target current;
• a feedforward controller for feedforward controlling said target current;
• and
• solenoid drive signal generating means for generating a solenoid drive signal according to outputs from said feedback controller and said feedforward controller;
• said feedforward controller changing a transfer function and/or a gain according to said gap detected by said gap detecting means;
• said feedforward controller selects one of a plurality of predetermined transfer functions and/or one of a plurality of predetermined gains according to said gap detected by said gap detecting means, whereby said feedforward controller selects a smaller one of said transfer functions and/or a smaller one of said gains when said gap is large, and selects a larger one of said transfer functions and/or a larger one of said gains when said gap becomes smaller.