Hydraulic Actuator Jerk Reduction via Valve Control
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Solution Overview
Problem
Hydraulic actuators experience jerky motion due to sudden pressure equalization when the load holding valve opens, leading to inefficient energy use and operator-perceived sluggishness, as existing solutions require back-driving the motor in the 'wrong direction and rely on complex sensor feedback for pressure or position control.
Innovation Solution
A method involving proportional control of load holding valves to gradually open and equalize pressure, using a sensor to monitor pump pressure and generate a control signal to fully open the valve only when a predetermined pressure is met, thereby minimizing jerky motion and energy inefficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the load holding valve opens suddenly to allow hydraulic fluid to flow, then the actuator responds quickly to operator input, but the actuator produces jerky motion due to pressure equalization
Solution Approach 1:
The system pre-pressurizes the hydraulic line by back-driving the pump in reverse before the actual actuation command is executed. This preliminary action ensures that when the load holding valve opens, there is no sudden pressure differential to cause jerky motion, while still maintaining quick response to operator input.
Solution Approach 2:
The system dynamically controls the load holding valve opening process rather than using a simple on/off mechanism. By progressively opening the valve and controlling the rate of pressure equalization, the system maintains smooth actuator motion while preserving responsive behavior to operator commands.
2Stress or pressure
If the pump is back-driven in the wrong direction to pressurize the hydraulic line, then pressure is built up quickly, but energy is wasted overcoming inertia and compressing fluid
Solution Approach 1:
The system converts the normally wasted energy from back-driving the pump into a useful function. The reverse rotation of the pump, which would normally just compress fluid and waste energy, is instead used to pre-pressurize the hydraulic line, eliminating the need for separate pressurization cycles and reducing overall energy consumption.
Solution Approach 2:
The system uses periodic reverse rotation of the pump at scheduled intervals to maintain hydraulic line pressure. Instead of continuous pressurization, the pump alternates between forward and reverse rotation, building pressure during reverse cycles and maintaining it during forward operation, thereby reducing total energy consumption.
3Manufacturing precision
If pressure or position sensors are used to control the pressurization duration, then the system can precisely control actuator motion, but the system complexity and cost increase
Solution Approach 1:
The system uses the pump's own motor current signature to determine when pressurization is complete and when to switch to normal operation. Instead of requiring external sensors to monitor pressure or position, the control system analyzes the electrical characteristics of the motor-driven pump, allowing the system to self-regulate based on its own operational state.
Solution Approach 2:
The system replaces mechanical pressure sensors and position sensors with electrical current sensing and analysis. By monitoring the motor current drawn by the pump during reverse rotation, the system infers pressure buildup and actuator position without requiring additional mechanical sensing components, thereby reducing system complexity.
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 ensures smooth actuator motion without jerks or shocks, reducing energy consumption and system complexity by eliminating the need for back-driving and simplifying sensor-based control decisions.
Implementation Method 1
an electrically-driven hydraulic pump
Implementation Method 2
a load holding valve in lieu of continuous operation of a hydraulic pump
Implementation Method 3
the electric machine, the inverter and the hydraulic pump
Data Source
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AI summary
A method and system is provided for controlling a hydraulic actuator in a work machine by opening a load holding valve in a measured fashion in order to leak hydraulic pressure back into a depressurized portion of the hydraulic circuit, thereby minimizing or eliminating jerkiness in the actuator when the actuator is under an external load.