Hydraulic Valve Vibration for Control Stability
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Solution Overview
Problem
The warm-up operation in low-temperature startups of toroidal continuously variable transmissions is prolonged due to insufficient oil fluidity, leading to instability in closed-loop control when switching to normal operation, as the viscosity resistance in the control valve flow path becomes significant at small opening degrees, causing nonlinearity and instability in the initial stages of normal control.
Innovation Solution
A position controller that applies a vibration wave to the closed-loop control signal of the control valve, allowing the operation command value to oscillate at a predetermined frequency, reducing viscosity resistance and nonlinearity, thereby stabilizing the control loop and shortening the warm-up operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the reference temperature for switching from warm-up operation to normal operation is lowered, then the warm-up operation time is shortened, but the closed-loop control becomes unstable due to high viscosity resistance and nonlinearity in the control valve flow path
Solution Approach 1:
The invention applies a vibration wave to the operation command value signal of the control valve, causing the valve opening to oscillate at a predetermined frequency. This mechanical vibration effect prevents the control valve from operating in the unstable small-opening region where viscosity resistance dominates, thereby maintaining closed-loop control stability even when the warm-up operation is shortened and switching to normal operation at lower temperatures.
Solution Approach 2:
The invention changes the parameter of the operation command value by superimposing a vibration wave with a predetermined frequency and amplitude. This parameter modification transforms the static command signal into a dynamic oscillating signal, enabling the control valve to operate in a stabilized manner that avoids the nonlinear region, thus resolving the contradiction between shortened warm-up time and control stability.
2Reliability
If the warm-up operation is prolonged to ensure stable closed-loop control, then control stability is maintained, but the startup time is extended and productivity is reduced
Solution Approach 1:
By applying a vibration wave to the control valve operation command, the system maintains closed-loop control stability without requiring an extended warm-up period. The vibration prevents the valve from operating in the unstable small-opening region, enabling earlier transition to normal operation and thus improving startup speed and productivity while maintaining control reliability.
Solution Approach 2:
The vibration wave is applied in advance during the transition from warm-up to normal operation, preparing the control valve to operate stably in the potentially unstable small-opening region. This preliminary stabilization action allows the system to bypass the need for prolonged warm-up, thereby improving productivity while maintaining control stability.
3Loss of time
If normal closed-loop control is started earlier at low oil temperature, then warm-up time is reduced, but viscosity resistance causes strong nonlinearity in the relationship between valve opening degree and oil flow rate
Solution Approach 1:
The vibration wave applied to the operation command value causes the control valve opening to oscillate, preventing it from settling in the small-opening region where viscosity resistance creates strong nonlinearity. This mechanical vibration effectively linearizes the valve characteristics by keeping the valve operating in a more stable region, thereby reducing the nonlinearity between valve opening degree and oil flow rate even when normal control starts earlier at low temperatures.
Solution Approach 2:
By changing the operation command value parameter through superimposition of a vibration wave, the system transforms the static valve operation into a dynamic oscillating operation. This parameter change effectively reduces the nonlinearity of the valve characteristics by preventing operation in the highly nonlinear small-opening region, thus simplifying the overall system behavior when early normal control is initiated.
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 effectively stabilizes the closed-loop control and reduces the warm-up time by alleviating viscosity resistance and nonlinearity, enabling early startup and stable power generation in low-temperature conditions.
Implementation Method 1
a vibration wave application unit that applies a vibration wave to a signal of the closed-loop control so that the operation command value vibrates at a predetermined frequency at start of the closed-loop control
Data Source
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AI summary
A position controller that performs position control by outputting a drive signal to a control valve of a hydraulic actuator that changes an operation position of an object, includes: a position acquisition unit that acquires an actual value of an operation position of the object; a position control unit that calculates an operation command value for the control valve by closed-loop control so as to reduce a deviation between a target value of the operation position of the object and the actual value; and a vibration wave application unit that applies a vibration wave to a signal of the closed-loop control so that the operation command value vibrates at a predetermined frequency at start of the closed-loop control.