Self-sensing active-damping voice coil

A control circuit for a voice coil, comprising:

• means for sensing current through the voice coil;
• means for filtering the sensed current to create an error voltage proportional to the integral of an external acceleration applied to the voice coil;
• and
• means for filtering the error voltage with a response proportional to a ratio of the electrical to mechanical impedances of the voice coil and the product of a lead-lag circuit to create a voltage applied to the voice coil that substantially cancels the external acceleration below a pole defined by the lead-lag circuit.

A voice coil actuator, comprising:

• an electromagnet;
• and
• a control circuit including,
• a current sensor coupled to the electromagnet;
• a first filter coupled to the current sensor to create an error voltage proportional to the integral of an external acceleration applied to the electromagnet;
• and
• a second filter with a lead-lag component coupled to the error voltage to create a voltage applied to the electromagnet that substantially cancels the external acceleration below a pole defined by a lead-lag component.

A voice coil actuator, comprising:

• an electromagnet;
• and
• a control circuit including,
• means for sensing current through the electromagnet;
• means for filtering the sensed current to create an error voltage proportional to the integral of an external acceleration applied to the electromagnet;
• and
• means for filtering the error voltage with a response proportional to a ratio of the electrical to mechanical impedances of the electro-magnet and the product of a lead-lag circuit to create a voltage applied to the electromagnet that substantially cancels the external acceleration below a pole defined by the lead-lag circuit.

A method for reducing external accelerations from a voice coil actuator, comprising:

• sensing current through the voice coil;
• filtering the sensed current to create an error voltage proportional to the integral of an external acceleration applied to the voice coil;
• and
• filtering the error voltage with a response proportional to a ratio of the electrical to mechanical impedances of the voice coil and the product of a lead-lag circuit to create a voltage applied to the voice coil that substantially cancels the external acceleration below a pole defined by the lead-lag circuit.

A memory drive, comprising:

• a disc;
• a motor coupled to the disc;
• an actuator;
• a head attached to the actuator, the head positioned to couple to the disc;
• and
• a controller for controlling the motor, the actuator and interfacing to the head, the controller having at least one servo system for controlling the actuator, the servo system including,
• a current sensor coupled to the actuator;
• a first filter coupled to the current sensor to create an error voltage proportional to the integral of an external acceleration applied to the actuator;
• and
• a second filter with a lead-lag component coupled to the error voltage to create a voltage applied to the actuator that substantially cancels the external acceleration below a pole defined by a lead-lag component.

A drive, comprising:

• a disc;
• a motor coupled to the disc;
• an actuator;
• a head attached to the actuator, the head positioned to couple to the disc;
• and
• a controller for controlling the motor, the actuator and interfacing to the head, the controller having at least one servo system for controlling the actuator, the servo system including,
• means for sensing current through the actuator;
• means for filtering the sensed current to create an error voltage proportional to the integral of an external acceleration applied to the actuator;
• and
• means for filtering the error voltage with a response proportional to a ratio of the electrical to mechanical impedances of the actuator and the product of a lead-lag circuit to create a voltage applied to the actuator that substantially cancels the external acceleration below a pole defamed by the lead-lag circuit.

A method of using a voice coil as a self-sensing detector for active-damping of external accelerations, comprising:

• applying a voltage to the voice coil;
• sensing the current in the voice coil;
• filtering the sensed current and subtracting the filtered value from the applied voltage to create an error signal proportional to the integral of the external acceleration;
• filtering the error signal to create an output signal proportional to the ratio of the electrical impedance to the mechanical impedance of the voice coil and the product of an lead-lag filter having a pole chosen to attenuate the noise and shock of the external accelerations.

A method of characterizing the mechanical impedance of a drive actuator on a drive having a data surface and a head for reading the data surface, comprising the steps of:

• applying a current to the drive actuator to move the head with respect to the data surface;
• reading the location of the head with respect to a data surface from the data surface;
• choosing a desired seek time;
• calculating mechanical impedance based on the read location, the desired seek time and the applied current.

A control circuit for compensating for back-emf in a solenoid, comprising:

• a sensor configured to detect current in the solenoid when subjected to accelerations;
• a first filter to convert the detected current to an error signal;
• and
• a second filter to accept the error signal and to apply energy to the solenoid to substantially cancel the back-emf caused by the acceleration within a limited frequency range.