A method for controlling a stepper motor includes calculating a duty cycle of a current provided to the stepper motor and comparing a difference, between the calculated duty cycle and a base duty cycle of current provided to the stepper motor under a base load condition, to a reference duty cycle value. The method also includes adjusting a peak current level of the current provided to the stepper motor responsive to the comparison.

A method for controlling a stepper motor includes calculating a duty cycle of a current provided to the stepper motor and comparing a difference, between the calculated duty cycle and a base duty cycle of current provided to the stepper motor under a base load condition, to a reference duty cycle value. The method also includes adjusting a peak current level of the current provided to the stepper motor responsive to the comparison.

An air manifold system for supplying an agricultural product to a plurality of metering devices comprises a product hopper having a product flow cavity, the product cavity separated from a first plenum by an air agitator sandwiched between the first plenum and the product flow cavity. The hopper comprises a plurality of nozzles extending through a wall of the hopper. A venturi assembly is in fluid communication with at least one nozzle. A first forced air stream flows through the first plenum and the air agitator into the product flow cavity to agitate and entrain agricultural product in the first air stream, and the first air stream carries the entrained agricultural product into the nozzles. A second forced air stream flows through the venturi assembly to accelerate the first air stream and the entrained product towards and through the supply hoses connected to the nozzles.

An air manifold system for supplying an agricultural product to a plurality of metering devices comprises a product hopper having a product flow cavity, the product cavity separated from a first plenum by an air agitator sandwiched between the first plenum and the product flow cavity. The hopper comprises a plurality of nozzles extending through a wall of the hopper. A venturi assembly is in fluid communication with at least one nozzle. A first forced air stream flows through the first plenum and the air agitator into the product flow cavity to agitate and entrain agricultural product in the first air stream, and the first air stream carries the entrained agricultural product into the nozzles. A second forced air stream flows through the venturi assembly to accelerate the first air stream and the entrained product towards and through the supply hoses connected to the nozzles.

A stepper motor controller includes a first error amplifier, a second error amplifier, and a comparator. The first error amplifier has a first input adapted to be coupled to a current sensor to receive a sensed drive current, a second input adapted to receive an expected drive current and an output to provide a first error signal based on a comparison of the sensed drive current and the expected drive current. The second error amplifier has a first input adapted to be coupled to a voltage sensor to receive a sensed drive voltage, a second input coupled to the output of the first error amplifier and an output to provide a second error signal based on a comparison of the sensed drive voltage and the first error signal. The comparator has a first input adapted to receive a reference signal, a second input coupled to the output of the second error amplifier and an output to provide a stepper motor control signal based on a comparison of the reference signal and the error signal.

A stepper motor controller includes a first error amplifier, a second error amplifier, and a comparator. The first error amplifier has a first input adapted to be coupled to a current sensor to receive a sensed drive current, a second input adapted to receive an expected drive current and an output to provide a first error signal based on a comparison of the sensed drive current and the expected drive current. The second error amplifier has a first input adapted to be coupled to a voltage sensor to receive a sensed drive voltage, a second input coupled to the output of the first error amplifier and an output to provide a second error signal based on a comparison of the sensed drive voltage and the first error signal. The comparator has a first input adapted to receive a reference signal, a second input coupled to the output of the second error amplifier and an output to provide a stepper motor control signal based on a comparison of the reference signal and the error signal.

In at least one general aspect, an inductive sensor can include a shaft having an axis of rotation, and a rotor physically coupled to the shaft and including a rotor coil. The rotor and the rotor coil can be aligned along a plane orthogonal to the axis of rotation. The inductive sensor can include a stator including a stator layer, an excitation coil, and an eccentricity receiver coil where the excitation coil and the eccentricity receiver coil are physically coupled to the stator layer.

In at least one general aspect, an inductive sensor can include a shaft having an axis of rotation, and a rotor physically coupled to the shaft and including a rotor coil. The rotor and the rotor coil can be aligned along a plane orthogonal to the axis of rotation. The inductive sensor can include a stator including a stator layer, an excitation coil, and an eccentricity receiver coil where the excitation coil and the eccentricity receiver coil are physically coupled to the stator layer.

A fast calibration method for slide-screw impedance tuners employs a new tuner control board and routine with independent direct triggering and data sampling by the VNA; a new vertical scaling algorithm bypasses the traditional iterative approach and uses numerical curve-fitting and ISO circle definition. Full tuner calibration executes without motor stopping, yielding time reduction typically by a factor of 8.

A driver device supplies an output current to each coil in a stepping motor to rotate a rotor. After the polarity and magnitude of the output current for each coil have reached the target polarity and magnitude, during control for keeping the polarity and magnitude of the output current for each coil at the target polarity and magnitude, occurrence of a particular current waveform in the output current due to a back-electromotive force resulting from the rotation of the rotor is detected so that, if a particular current waveform is detected, a predetermined detection signal is transmitted to an external device.