Circuit for estimating the speed of an electromagnetic actuator

A circuit for estimating speed of an electromagnetic actuator associated with a reading head of a disk storage unit and a digital controller, the circuit comprising:

• first and second supply terminals and an output terminal, with the first supply terminal being connected to the electromagnetic actuator;
• a measuring resistor connected to the second supply terminal, and connected in series with the electromagnetic actuator for measuring a current which passes therethrough when a supply voltage is applied between the first and second supply terminals;
• an adder having an output connected to the output terminal for providing an output voltage corresponding to an estimated speed of the electromagnetic actuator, a first input connected to the first supply terminal, and a second input connected to the second supply terminal;
• and
• a transfer circuit connected between the first and second supply terminals and the first and second inputs of said adder for transferring to said adder the supply voltage and a voltage across said measuring resistor, said transfer circuit comprising
• an adjustable-gain amplifier connected between said measuring resistor and the second input of said adder, and
• a determination circuit connected to said adjustable-gain amplifier for determining a gain U thereof, said determination circuit comprising a coarse setting circuit and a fine calibration circuit controlled by the digital controller.

A circuit for estimating speed of an electromagnetic actuator, the circuit comprising:

• first and second supply terminals and an output terminal, with the first supply terminal being connected to the electromagnetic actuator;
• a measuring resistor connected to the second supply terminal, and connected in series with the electromagnetic actuator for measuring a current which passes therethrough when a supply voltage is applied between the first and second supply terminals;
• an adder having an output connected to the output terminal for providing an output voltage corresponding to an estimated speed of the electromagnetic actuator;
• a first input connected to the first supply terminal, and a second input connected to the second supply terminal;
• a transfer circuit connected between the first and second supply terminals and the first and second inputs of said adder for transferring to said adder the supply voltage and a voltage across said measuring resistor, said transfer circuit comprising
• an adjustable-gain amplifier connected between said measuring resistor and the second input of said adder, and
• a determination circuit connected to said adjustable-gain amplifier for determining a gain thereof, said determination circuit comprising
• a coarse setting circuit comprising a resistive voltage divider connected between a first voltage reference and a second voltage reference for deriving a coarse voltage setting,
• a fine calibration circuit connected to said coarse setting circuit and comprising a plurality of resistors connected in series between a third voltage reference and the second voltage reference, and
• a multiplexer connected to said plurality of resistors and having an input for receiving a digital control signal for adjusting the coarse voltage setting, and an output connected to said adjustable-gain amplifier providing an adjustment control signal thereto for adjusting the gain thereof.

A method for estimating speed of an electromagnetic actuator comprising:

• connecting a measuring resistor in series with the electromagnetic actuator, and connecting the measuring resistor and the electromagnetic actuator between first and second supply terminals;
• applying a supply voltage across the first and second supply terminals;
• measuring a current passing through the electromagnetic actuator using the measuring resistor;
• and
• transferring the supply voltage and a voltage across the measuring resistor to an adder for providing an output voltage corresponding to an estimated speed of the electromagnetic actuator, the transferring comprising adjusting a gain of an adjustable-gain amplifier connected between the measuring resistor and the adder, the adjusting comprising
• deriving a coarse voltage setting, and
• adjusting the coarse voltage setting based upon a digital control signal for generating an adjustment control signal for adjusting the gain of the adjustable-gain amplifier.