Solenoid Valve Control Device Using Estimated Current Feedback
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Solution Overview
Problem
Accurately controlling a linear solenoid valve without feedback-controlling a target current command value is challenging due to phase lag in the actual current value, leading to difficulties in achieving target dither amplitude, which hinders hydraulic responsiveness and increases calculation load, requiring larger chips and higher costs.
Innovation Solution
A control device that detects the actual current value, generates a primary command voltage value by feeding back the current command value, calculates a dither command voltage value to cause periodic voltage oscillation, filters the actual current value to remove dither frequency, and superimposes it on the primary command voltage to generate a PWM signal, reducing calculation load and chip size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control is performed using the actual current value with phase lag, then the target dither amplitude cannot be achieved, but if no feedback control is performed, then accurate control of the linear solenoid valve is compromised
Solution Approach 1:
The patent introduces an intermediary variable (estimated current value) that mediates between the actual current value with phase lag and the control requirements. This estimated value is derived from the PWM duty cycle and circuit parameters, serving as a phase-compensated representation of the current that enables accurate dither amplitude control without being affected by the 90-degree phase lag of the actual current measurement
Solution Approach 2:
The patent performs preliminary calculation of the estimated current value based on the PWM duty cycle before feedback control is applied. By pre-computing the current estimate from the control signal itself (rather than from the lagged actual current measurement), the system establishes an accurate reference for dither amplitude control in advance, eliminating the need to compensate for phase lag during the feedback loop
2Measurement precision
If complicated calculation of dither amplitude considering phase lag is performed, then target dither amplitude can be achieved, but calculation load increases and chip size must be increased
Solution Approach 1:
The patent replaces complex real-time calculation mechanisms with a simplified computational approach. Instead of performing complicated calculations to compensate for phase lag in the actual current feedback, the system substitutes this with a direct calculation of estimated current from the PWM duty cycle using simple algebraic relationships (I_est = V_supply × PWM_duty / R_coil), dramatically reducing calculation load and eliminating the need for large chips while maintaining dither amplitude accuracy
3Productivity
If actual current value with phase lag is used for feedback control, then control is performed, but hydraulic responsiveness is degraded due to inability to achieve target dither amplitude
Solution Approach 1:
The patent implements a feedback mechanism using the estimated current value (而非 the lagged actual current). The estimated current, derived from PWM duty cycle and circuit parameters, provides accurate feedback about the solenoid valve's actual state without suffering from phase lag. This enables the controller to maintain target dither amplitude accurately, thereby preserving hydraulic responsiveness while achieving precise control
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 approach allows accurate control of the linear solenoid valve while reducing calculation load and eliminating the need for larger chips, achieving cost reduction and improved hydraulic responsiveness.
Implementation Method 1
The linear solenoid valve has a coil, and a current supplied to the coil drives a plunger (a movable iron piece) to control the position of a spool
Implementation Method 2
generates a PWM signal by PWM modulation of the current value, and controls an application voltage by driving switching elements with the PWM signal
Data Source
AI summary
A control device that includes an electronic control unit that is configured to: detect an actual current value flowing through the solenoid valve; receive a current command value and the actual current value detected and generate a primary command voltage value while feeding back the current command value on the basis of the actual current value; calculate a dither command voltage value to cause a periodic voltage oscillation; filter the actual current value detected to remove a frequency corresponding to a period of the dither command voltage value and output the filtered actual current value; generate a secondary command voltage value by superimposing the dither command voltage value generated on the primary command voltage value generated; convert the secondary command voltage value generated into a PWM signal; and generate, on the basis of the PWM signal generated, an application voltage to be applied to the solenoid valve.