Solenoid Valve Control for Smooth Direction Inversion
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Solution Overview
Problem
Direction inversion maneuvers in work vehicles, such as compact wheel loaders, are typically jerky and sensitive to motor rotational speed due to the dependency of flow rate on the force driving the pump and load, leading to reduced user comfort and increased cycle time.
Innovation Solution
A control method that modulates the driving current of open centre directional solenoid valves based on joystick position and motor rotational speed, using a reference model to adjust the hydraulic flow rate and improve the smoothness of direction inversion maneuvers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If open centre directional solenoid valves are used to control hydraulic actuators, then device complexity is reduced and cost is lowered, but the direction inversion maneuver becomes jerky and sensitive to motor rotational speed
Solution Approach 1:
The control system dynamically adjusts the driving current of the solenoid valve based on motor rotational speed. The electronic control unit modifies the valve opening degree in real-time according to the current motor speed, making the system adaptive rather than static. This dynamic adjustment compensates for the inherent sensitivity to motor speed variations, eliminating the jerky motion during direction inversion while maintaining the simplicity of open centre valves.
Solution Approach 2:
The invention changes the operating parameters of the solenoid valve by modulating the driving current according to motor rotational speed. Instead of using a fixed opening degree, the system varies the valve opening parameter dynamically based on the motor speed state. This parameter adjustment smooths the hydraulic flow rate changes during direction inversion, resolving the jerkiness issue without requiring complex valve hardware.
2Device complexity
If the flow rate depends on the force driving the pump and load, then the hydraulic system is simple, but the rate of actuation becomes dependent on motor rotational speed
Solution Approach 1:
The electronic control unit implements a feedback mechanism by continuously monitoring the motor rotational speed and using this information to adjust the solenoid valve opening degree. The system feeds back the motor speed state to the valve control, creating a closed-loop system that compensates for speed-dependent flow rate variations. This feedback ensures consistent actuation rates regardless of motor speed changes, while maintaining the simplicity of the hydraulic system architecture.
3Device complexity
If a large movement of the joystick is required to start movement at low motor speed, then the system is simple, but the ease of operation is reduced
Solution Approach 1:
The control system dynamically adjusts the relationship between joystick position and valve opening degree based on motor rotational speed. At low motor speeds, the system increases the sensitivity of the control response, allowing smaller joystick movements to produce the necessary valve opening. This dynamic control adaptation improves ease of operation across different motor speed ranges without adding complex hardware.
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
The control method enhances the controllability and comfort of boom and implement movements during direction inversion maneuvers, reducing the sensitivity to motor speed and maintaining cycle time efficiency.
Implementation Method 1
open centre directional solenoid valves 18, 20... modulating the driving current of the open centre directional solenoid valve... according to a predetermined reference model of a modified driving current of each solenoid valve
Implementation Method 2
each hydraulic actuator comprises an hydraulic cylinder operatively connected respectively to the boom and the implement, that uses hydraulic power of a working fluid to facilitate mechanical operation
Data Source
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AI summary
A control method for actuating a movement inversion of at least one of a boom and an implement in a work vehicle powered by a motor is disclosed. Actuating the boom and the implement occurs by means of a joystick controlled by a user, a movement of the joystick in a predetermined control area according to a first preset direction causing the actuation of the boom by a first hydraulic actuator and a movement of the joystick in the control area according to a second preset direction causing the actuation of the implement by a second hydraulic actuator. Each hydraulic actuator includes a respective open centre directional solenoid valve whose opening degree is controlled by means of a driving current as a function of the position of the joystick. The control method comprises acquiring a position of the joystick over time as well as a rotational speed of the motor, determining that a direction inversion manoeuvre is requested when a travel of the joystick from a first operating position to a second operating position includes at least one of the first and the second component of the joystick position being reversed with respect to the neutral position; and - when a direction inversion manoeuvre is requested - applying a modified driving current of at least one of the first and the second open centre directional solenoid valve, respectively, based on a predetermined reference model of the modified driving current, indicative of a nominal relation between between the rotational speed of the motor and the evolution over time of the driving current of the respective first and second open centre directional solenoid valve.