Actuator retraction circuit

A method for retracting an actuator comprising the steps of:

• determining back emf voltage generated by an actuator;
• scaling said determined voltage;
• charging a capacitor in a capacitor resistor network by applying said scaled voltage and a holding voltage to said capacitor-resistor network to develop a charged capacitor voltage;
• discharging said charged capacitor voltage through said capacitor-resistor network;
• combining said discharging charged capacitor voltage with said holding voltage to provide a forcing voltage that decays with time to a predetermined fixed voltage, said predetermined fixed voltage being a function of said holding voltage;
• and
• applying said forcing voltage to said actuator to generate a high initial deceleration current in said actuator and to controllably retract said actuator.

A method for the open loop retraction of an actuator upon power loss, spindown, or upon system request comprising the steps of:

• allowing actuator coil current to decay to zero through inductive flyback;
• measuring actuator back emf voltage;
• inverting and scaling said measured voltage;
• applying a holding voltage to said capacitor-resistor network;
• charging a capacitor in a resistor-capacitor network to develop a charged capacitor voltage by applying said inverted and scaled voltage to said resistor-capacitor network;
• discharging said charged capacitor voltage through said capacitor-resistor network;
• combining said discharging charged capacitor voltage with said holding voltage to provide a forcing voltage that decays with time to a predetermined fixed voltage, said predetermined fixed voltage being a function of said holding voltage;
• and
• applying said forcing voltage to said actuator to generate a high initial deceleration current in said actuator and to controllably retract said actuator.

A circuit for retracting an actuator comprising:

• a resistor-capacitor network;
• a differential amplifier for determining back emf voltage generated by the actuator motor;
• said amplifier applying said determined voltage to a capacitor-resistor network;
• a holding voltage generator for applying a holding voltage to said capacitor-resistor network, application of said determined voltage and said holding voltage together charging a capacitor in said capacitor-resistor network to develop a charged capacitor voltage and said capacitor discharging said charged capacitor voltage through said capacitor-resistor network to provide a forcing voltage to said actuator for retract operation and said forcing voltage initially generating a high deceleration current in said actuator and said forcing voltage decaying with time to a predetermined fixed voltage to complete said retract operation.

A circuit for retracting an actuator comprising:

• a resistor-capacitor network;
• a differential amplifier for determining back emf voltage generated by the actuator motor;
• said amplifier applying said determined voltage to a capacitor-resistor network;
• a holding voltage generator for applying a holding voltage to said capacitor-resistor network, application of said determined voltage and said holding voltage together charging a capacitor in said capacitor-resistor network to develop a charged capacitor voltage and said capacitor discharging said charged capacitor voltage through said capacitor-resistor network;
• a power amplifier connected to said resistor capacitor network to receive said discharging charged capacitor voltage and to provide a forcing voltage to said actuator for retract operation, said forcing voltage initially generating a high deceleration current in said actuator and said forcing voltage decaying with time to a predetermined fixed voltage to complete said retract operation.