Abstract: A power supply (20) for providing a desired current to an electric load (23) broadly comprises: a current limiter (21) for providing a desired current; a current sensor (28) for determining the actual current supplied by the current limiter and providing a feedback signal (30, 31) to the current limiter for causing the current limiter to reduce the error between the desired and the actual currents; and a test circuit (24) for temporarily changing the actual current sensed by the current sensor to a level different from the desired current for causing the current limiter to adjust the magnitude of the current provided thereby; whereby the operation of the power supply may be tested. The invention also provides an improved method of operating such a power supply.

Abstract: A power supply (20) for providing a desired current to an electric load (23) broadly comprises: a current limiter (21) for providing a desired current; a current sensor (28) for determining the actual current supplied by the current limiter and providing a feedback signal (30, 31) to the current limiter for causing the current limiter to adjust to reduce the error between the desired and the actual currents; and a test circuit (24) for temporarily changing the actual current sensed by the current sensor to a level different from the desired current for causing the current limiter to adjust the magnitude of the current provided thereby; whereby the operation of the power supply may be tested. The invention also provides an improved method of operating such a power supply.

Abstract: A system and method is provided for positioning a take-up reel in a tape drive unit so that a leader block can be inserted therein. The take-up reel is driven by a motor having a rotatable shaft and a motor controller. A position encoder, mounted on the shaft of the motor, uses a Hall-effect device to generate a Hall voltage signal in response to rotational motion of the motor shaft. The Hall voltage signal is amplified to provide a motor phase signal which is then compared to a reference level (usually zero volts) to generate encoder pulses. The encoder pulses are counted using a counter/state machine to determine a position and direction of rotation of the take-up reel. A feature of this system is that it is calibrated using a processor that determines the DC level of the motor phase signal and subsequently adjusts the motor phase signal so that it is substantially symmetrical about the reference level to which it is compared.

Abstract: An apparatus and method for profiling the velocity of a leader block to optimize thread time in a helical scan transport uses a substantially triangular velocity profile. Local changes in acceleration and tape back tension are used to dynamically control the position of the leader block to avoid collisions with guide posts and other transport components adjacent the tape path.

Abstract: This improved signal discontinuity compensation method compensates for discontinuity in the relationship between motor position commands received by a motor driver, and motor current signals sent to a motor by the motor driver. A best fit approximation of the signal discontinuity is generated based on median data points which provides resistance to anomalous data points. The compensation is accomplished by adding an offset to specific motor position commands sent to the motor driver based on the best fit approximation. The offset command maximizes accuracy and control over motor motion by avoiding the motor driver's motor current signal discontinuity.

Abstract: A system and method for controlling an amount of force supplied by a motor to move an object from an at-rest position is presented. The system comprises a motor controller configured to provide a motor control signal to control the amount of force supplied by the motor, and a position sensor configured to detect an actual position of the object being moved by the motor and to send an actual position signal to the motor controller. The motor control signal supplied by the motor controller controls the motor such that the motor supplies a cubic increase in force on the object to move the object from its at-rest position. The motor controller comprises a profile generator, configured to provide an acceleration profile, a velocity profile and a position profile, and to output a drive signal in response to the position profile, wherein the position profile represents a desired position of the object as a function of time. The position profile is a cubic profile as a function of time.

Abstract: An apparatus and method for use in appending data to data that has been previously established on a tape in a helical scan tape recorder that results in the spacing between the appended data and the previously established data being within a defined range. The present invention provides a method for measuring the total delay associated with the write and read circuitry within the recorder and a method and apparatus for using the total delay to initiate the writing of the data to be appended to the previously established data on the tape at the appropriate instant to achieve the desired spacing. An apparatus and method for compensating for inaccuracies in the measured total delay to prevent "creep", i.e.

Abstract: A driver circuit for a DC brushless motor of unknown characteristics operable to start and test to determine the desired characteristics and therefore to accurately and reliably run the motor.