Switching-Valve Position Detection via Carrier-Wave Solenoid Feedback
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Solution Overview
Problem
Conventional electromagnetic switching-valve position detection systems face challenges in achieving high responsiveness and gain for electric current control while maintaining accurate position detection, often requiring low loop gain or responsiveness, which can degrade the detection signal.
Innovation Solution
An electromagnetic switching-valve position detection system that includes an electric current control circuit with a bridge diode, smoothing capacitors, a switching transformer, and a control unit that superimposes a high-frequency carrier wave on the electric current command, allowing for high-frequency position detection and improved signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If electric current feedback control is implemented with high responsiveness and gain, then the switching speed of the electromagnetic switching-valve is improved, but the detection signal for position detection is attenuated and degraded
Solution Approach 1:
The patent introduces a carrier wave as an intermediary signal that is superimposed on the electric current command signal. This carrier wave serves as a mediator that allows position detection without directly competing with the high-gain feedback control signal. The carrier wave frequency component is modulated by the solenoid impedance changes, enabling position detection to be extracted from the feedback signal without being overwhelmed by the high-gain control action.
Solution Approach 2:
The patent employs periodic carrier wave signals (sine waves or triangular waves) at frequencies between 0.1 to 1 kHz that are superimposed on the electric current command. This periodic action creates a modulated signal that passes through the solenoid, and the impedance variations due to armature position modulate the carrier wave amplitude. This allows position information to be encoded in the periodic signal that can be extracted even in the presence of high-gain feedback control.
2Measurement precision
If position detection is implemented using conventional methods, then the position of the valve spool can be detected, but the electromagnetic switching-valve becomes lengthened or upsized
Solution Approach 1:
The patent makes the solenoid coil serve dual functions: it both drives the armature movement and simultaneously provides the sensing function for position detection. The same solenoid impedance that changes with armature position is used to modulate the carrier wave for detection purposes. This self-service approach eliminates the need for separate detection mechanisms, thereby avoiding any increase in valve size while maintaining position detection capability.
Solution Approach 2:
The patent implements multi-functionality by using the solenoid coil for both actuation and sensing purposes. The solenoid coil generates the magnetic field to drive the armature while simultaneously its impedance changes provide the position detection information through carrier wave modulation. This universal use of the solenoid coil eliminates the need for additional dedicated position detection components, preventing any increase in the overall valve dimensions.
3Measurement precision
If the detection signal is inputted as the disturbance of an electric current loop, then the superimposition signal can be preserved, but the responsiveness of electric current control must be reduced
Solution Approach 1:
The patent separates the detection function from the control function by using different frequency dimensions. The carrier wave for position detection is superimposed on the electric current command signal at a frequency (0.1 to 1 kHz) that is distinct from the control signal frequency. This dimensional separation in the frequency domain allows the detection signal to be extracted from the feedback without interfering with or being degraded by the high-responsiveness control loop, as they operate in different frequency bands.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This system enables accelerated switching speed and accurate position detection of the valve spool, enhancing the responsiveness of electric current control and preventing unintended valve closure due to disturbances, while maintaining a high signal-to-noise ratio.
Implementation Method 1
a moving core that is attracted and moved to a fixed core by an excitation of an energized solenoid
Implementation Method 2
a bridge diode into which an electric current from a power supply flows
Implementation Method 3
a primary smoothing capacitor configured to smooth a direct current from the bridge diode
Implementation Method 4
a switching transformer configured to transform a pulse wave alternating current which being converted from the direct current smoothed at the primary smoothing capacitor
Data Source
AI summary
An electromagnetic switching-valve position detection system includes: an electric current control circuit in which an electric current from a power supply is smoothed to be a direct current, and is turned into a pulse wave alternating current, the pulse wave alternating current being transmitted to the secondary side and outputted as a smoothed direct current; a carrier wave generator configured to superimpose a high frequency carrier wave for position detection on a signal wave of the electric current command; and a detecting unit configured to extract a carrier wave frequency component for the position detection from a voltage feedback signal of the solenoid, detect a voltage amplitude from the frequency component, and obtain an amplitude signal. The control unit has a position determining unit configured to determine a position of the valve spool, and a determination circuit configured to output a valve position signal based on the determination signal.