Abstract: An aggregate transferring apparatus for elevating aggregate may include a base assembly with a base frame, an unloader structure on the base frame, and a base conveyor on the base frame positioned to receive aggregate from a vehicle positioned on the unloader structure. The apparatus may also include an aggregate elevating assembly with a deployable frame mounted on the base frame and being movable between storage and deploy positions, and an elevating conveyor for receiving aggregate from the base conveyor and conveying the aggregate upwardly on the deployable frame. The apparatus may further include a conveyor extension assembly for conveying aggregate horizontally outward from the elevating assembly. The extension assembly may include an extension conveyor movable between lowered and raised positions and being articulated with an inboard and outboard segments.

Abstract: Various systems and methods for implementing feedback in a switching regulator are disclosed. For example, various current feedback circuits are disclosed that include a current feedback node and a sense node. In addition, the current feedback circuits include an operational amplifier with two inputs. One of the inputs is electrically coupled to a power source via a first resistor, and may further be electrically coupled to a ground by closing a first switch or to the sense node by closing a second switch. The other input is electrically coupled to the ground via a second resistor, and may further be electrically coupled to the sense node by closing a third switch or to the power source by closing a fourth switch. The operational amplifier drives the current feedback node.

Abstract: Various systems and methods for implementing feedback in a switching regulator are disclosed. For example, various current feedback circuits are disclosed that include a current feedback node and a sense node. In addition, the current feedback circuits include an operational amplifier with two inputs. One of the inputs is electrically coupled to a power source via a first resistor, and may further be electrically coupled to a ground by closing a first switch or to the sense node by closing a second switch. The other input is electrically coupled to the ground via a second resistor, and may further be electrically coupled to the sense node by closing a third switch or to the power source by closing a fourth switch. The operational amplifier drives the current feedback node.

Abstract: A control apparatus controls retraction of a device carried on a moveable member actuated by an electric motor after a sudden power loss. The control apparatus includes a measuring circuit for measuring a back electromotive force (back EMF) from the electric motor during a measuring phase. The control apparatus also includes a controller which receives the actual velocity and provides a command signal for controlling a magnitude of the drive current based on a commanded velocity and the actual velocity of the moveable member. The control apparatus further comprises a current control loop for providing a command current signal based on the current provided to the electric motor and the command signal, and for providing the electric motor with the drive current during a driving phase based on the command current signal.

Abstract: A control apparatus controls retraction of a device carried on a moveable member actuated by an electric motor. The control apparatus includes a measuring circuit with an output during a measuring phase including a back electromotive force (back EMF) from the electric motor plus a measuring circuit offset voltage. The control apparatus also includes an offset removing circuit connected to the output of the measuring circuit. The back EMF from the electric motor is provided at the output of the offset removing circuit. A driver circuit is connected to terminals of the electric motor for providing the electric motor with a drive current during a driving phase with a magnitude based on the back EMF from the electric motor.

Abstract: A motor controller provides pulse width modulated drive signals to a motor. A digital demand code for controlling motor speed is input to the motor controller. A dither generator generates a digital dither value, which an adder adds to the demand code to generate a dithered demand code. A position determining circuit determines a rotational position of the motor. A pulse width modulation controller generates pulse width modulated drive signals with duty cycles controlled as a function of a stored set of waveform coefficients, the dithered demand code, and the rotational position of the motor.

Abstract: A control circuit controls current through a voice coil motor (VCM) during retraction of a transducing head from the surface of a recordable medium. The transducing head is carried on movable member actuated by the VCM. The control circuit includes a measuring circuit for measuring a back electromotive force (back EMF) from the VCM. The control circuit also includes a driver circuit connected to terminals of the VCM for providing the VCM with a drive current having a magnitude based on the back EMF from the VCM. The control circuit further includes a chop clock to alternate between measuring the back EMF from the VCM and providing the VCM with the drive current at a random frequency within a range of frequencies around a median frequency.

Abstract: A three-phase spindle motor has three terminals each driven with pulse width modulated signals. Rotation of the motor is controlled by iteratively measuring an electrical period of the motor, determining a rotational position of the motor, and synchronizing the sinusoidal pulse width modulation of the spindle motor with the measured electrical period. The electrical period of the motor is measured by detecting zero crossings in the a back electromotive force induced at a first terminal of the motor and determining the time between successive zero crossings. The rotation position of the motor is determined based upon the last measured electrical period and a location of last detected zero crossing. The zero crossings are detected by selecting a time window during which the back electromotive force signal is sensed for zero crossings. The time window is selected as a function of the last measured electrical period and the rotational position of the motor.

Abstract: A disk drive emergency retract architecture for providing power to a voice coil motor (VCM) to retract a transducing head from a surface of a recordable medium during loss of power from an external power supply. The disk drive emergency retract architecture comprises a spindle motor, having an internal inductance and an internal resistance, for spinning the recordable medium. The spinning recordable medium creates a back electromotive force (BEMF) in the spindle motor. A boost circuit transfers the back electromotive force located in the spindle motor to a capacitor which stores and supplies power to the VCM. The capacitor is connected to a power switch circuit, which supplies power from the capacitor to the VCM when the power switch circuit is in a conducting state and prevents power from being supplied to by the capacitor to the VCM when the power switch circuit is in a non-conducting state.

Abstract: An operational amplifier connected to first and second transistors of an H-bridge for sinking and sourcing current, the operational amplifier having a differential input and an output and comprising a transconductance circuit, a gain circuit, a buffer circuit, and first and second feedback networks. The transconductance circuit is connected to receive the differential input and provide an output, wherein the output is connected to the second transistor of the H-bridge. The gain circuit is connected to receive the output from the transconductance circuit, wherein the gain circuit includes a transistor that is matched to the second transistor of the H-bridge. The buffer circuit is connected between the gain circuit and the first transistor of the H-bridge. The first feedback network comprises a level shift circuit connected to the output of the operational amplifier and a clamping circuit connected between the level shift circuit and an input of the buffer circuit.

Abstract: A motor controller for an electric motor having a plurality of motor terminals is connected to a power supply and comprises a commutation control, a current sensor, a peak target circuit, a pulse width control and a reverse current control. The commutation control is connected to the motor terminals for causing current pulses to flow through selected terminals during each commutation state. The current sensor provides a sense signal representative of the current pulses, and the peak current target circuit provides a target signal. The pulse width control controls pulse width of the current pulses as a function of the sense signal and the target signal. The reverse current control prevents reverse current from flowing into the power supply during change of commutation state.