DC Solenoid Plunger Detection via Current Sense Peak Valley Analysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing solenoid movement detection methods are unreliable due to temperature variations and fail to accurately detect slow plunger movements, particularly in safety-critical applications where precise control is necessary.
Innovation Solution
A method involving a current sense amplifier, active peak detector, level shifter, and comparator circuit that detects the difference between peak and valley currents in the solenoid coil to generate a level-shifted signal, allowing for reliable detection of complete plunger movement by comparing these signals, with a predefined threshold that remains constant across temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed reference or algorithmic solutions are used for detecting peak and valley current, then plunger movement detection is achieved, but the detection fails during temperature variation or slow plunger movement
Solution Approach 1:
The patent changes the detection parameter from fixed current thresholds to a dynamic threshold based on the difference between peak and valley currents (ΔI = I_peak - I_valley). This parameter change allows the detection system to adapt to temperature variations and slow plunger movements, as the threshold automatically adjusts according to the actual current waveform characteristics rather than relying on predetermined fixed values
Solution Approach 2:
The patent introduces a dynamic detection threshold that adapts to changing operating conditions. Instead of using static reference values, the system calculates the threshold dynamically based on the measured peak and valley currents, making the detection mechanism responsive to temperature changes and varying plunger movement speeds
2Measurement precision
If hall sensors are used to detect plunger position, then position detection is achieved, but the mechanical mounting becomes complex and performance is affected by ageing and external field
Solution Approach 1:
The patent replaces the mechanical hall sensor mounting system with an electrical measurement system. Instead of physically mounting sensors near the plunger, the invention uses current sensing circuits to detect plunger position indirectly through electromagnetic effects, eliminating the need for complex mechanical sensor mounting while maintaining detection accuracy
Solution Approach 2:
The patent introduces the solenoid coil current as an intermediary parameter to detect plunger position. Rather than directly sensing the plunger's physical position with hall sensors, the system uses the current waveform characteristics (peak and valley currents) as an intermediate indicator that reflects plunger movement, simplifying the detection mechanism
3Strength
If solenoid coil operates continuously at nominal current, then sufficient magnetic field is maintained, but temperature increase occurs due to higher power dissipation
Solution Approach 1:
The patent implements periodic current adjustment based on plunger position detection. The solenoid operates at high current only during the brief period when plunger movement is detected, then switches to hold current. This periodic action pattern ensures sufficient magnetic field strength during activation while minimizing overall power dissipation and temperature increase
Solution Approach 2:
The patent introduces dynamic current control that adjusts the solenoid operating current based on real-time plunger position detection. The system transitions from static continuous nominal current operation to dynamic current adjustment, reducing current to hold level once plunger movement is detected, thereby balancing magnetic field requirements with thermal management
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 solution provides a simple, low-cost, and reliable technique for detecting solenoid plunger movement, immune to temperature changes and capable of identifying slow movements, ensuring accurate operation in safety-critical applications.
Implementation Method 1
Electromechanical solenoids consist of an electromagnetically inductive coil that is wound to encircle a movable steel or iron slug, termed 'the armature' or 'plunger.'
Implementation Method 2
The movement of the plunger induces back EMF in the coil, and hence, the solenoid current starts dropping.
Data Source
AI summary
An apparatus and method of detecting movement of a plunger of the solenoid includes detecting a peak (IPEAK) in a current signal applied to a coil of the solenoid. A predetermined threshold is added to the current signal applied to the coil of the solenoid to generate a level shifted signal. The level shifted signal and the peak signal are compared to detect movement of a plunger of the solenoid.