Solenoid Valve Control for Return-to-Dig Precision
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Solution Overview
Problem
Existing control systems for work vehicles, such as compact wheel loaders, face challenges in achieving precise return-to-dig movements of implements like buckets due to varying motor rotational speeds, leading to residual tilt errors from 3° to 8°, as they rely on expensive continuous position sensors or separate control means.
Innovation Solution
A control method that modulates the driving current of the open centre directional solenoid valve based on motor rotational speed, using a predetermined reference model to maintain a constant hydraulic flow rate and achieve precise bucket alignment, by varying the amplitude of the driving current inversely proportional to motor speed and setting it to zero when the bucket reaches the desired tilt position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a continuous position sensor is used to achieve precise return-to-dig movement, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses an intermediary approach by introducing a calculation unit that computes the tilting speed based on existing sensor data (angular signals from sensors detecting boom and bucket positions) and pump flow rate information, rather than directly measuring tilting speed with a dedicated continuous position sensor. This intermediary calculation achieves precise control without the complexity and cost of expensive continuous position sensors.
Solution Approach 2:
The patent replaces the mechanical/sensor-based continuous position sensing system with a computational approach. Instead of using expensive continuous position sensors to directly measure bucket position, the system substitutes a calculation unit that computes tilting speed from existing sensor readings and flow rate data, achieving the same control precision through mathematical computation rather than direct physical measurement.
2Productivity
If the motor rotational speed varies, then productivity is improved, but manufacturing precision deteriorates due to residual tilt errors
Solution Approach 1:
The patent applies dynamics by making the solenoid valve opening degree adaptive to varying motor rotational speeds. The control unit dynamically adjusts the opening degree based on real-time speed feedback, creating a dynamic control system that maintains precise bucket alignment across all operating speeds. This dynamic adjustment eliminates the residual tilt errors that occur with fixed control parameters.
Solution Approach 2:
The patent changes the control parameter (solenoid valve opening degree) as a function of motor rotational speed. By establishing a relationship where the opening degree varies with speed, the system compensates for speed-induced variations in hydraulic flow rate, maintaining consistent bucket tilting speed and precise alignment regardless of motor speed fluctuations.
3Device complexity
If the solenoid valve opening degree is fixed, then device complexity is reduced, but speed adaptability deteriorates
Solution Approach 1:
The patent transforms the static solenoid valve opening degree into a dynamic parameter that automatically adapts to motor rotational speed. The control unit continuously adjusts the opening degree based on speed feedback, enabling the system to maintain precise return-to-dig functionality across all operating speeds without adding significant complexity to the control architecture.
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 improves the precision of return-to-dig functionality across all motor rotational speeds, reducing residual tilt errors and eliminating the need for expensive continuous position sensors, while maintaining hydraulic flow rate consistency.
Implementation Method 1
the hydraulic actuator comprises an hydraulic cylinder operatively connected to the bucket, that uses hydraulic power of a working fluid to facilitate mechanical operation
Implementation Method 2
the rate of actuation of the bucket is controlled by the opening degree of the open centre directional solenoid valve 18 by means of a driving current thereof
Data Source
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AI summary
A control method for actuating a return-to-dig movement of an implement in a work vehicle powered by a motor is disclosed. Actuating 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 preset direction causing the actuation of the implement by an hydraulic actuator. The hydraulic actuator includes an open centre directional solenoid valve whose opening degree is controlled by means of a driving current. The control method comprises determining that a return-to-dig manoeuvre is requested, acquiring a rotational speed of the motor, applying a modulated driving current of the open centre directional solenoid valve, based on a predetermined reference model, indicative of a nominal relation between the driving current of the open centre directional solenoid valve and the rotational speed of the motor, and setting the modulated driving current to zero when a predetermined reference tilt position of the implement is reached.