Actuator Limit Controller for Hydraulic End-Stop Shock Prevention
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Solution Overview
Problem
Hydraulic actuators face issues with sudden stops and high forces when reaching end-stops, leading to stress and potential failure in mechanical components due to inadequate control over speed and force during motion.
Innovation Solution
A method and system for position-force control of hydraulic actuators, which includes a controller that adjusts the valve assembly to reduce piston speed and apply a force away from the end-stop as the piston approaches, using a combination of position feedback and signal modifications to prevent shock and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the valve assembly maintains constant flow control, then the actuator operates efficiently at given speed, but the piston causes sudden stops and high forces at end-stops leading to stress and potential failure
Solution Approach 1:
The control system dynamically adjusts the valve assembly operation based on real-time position feedback. As the piston approaches the end-stop, the controller modifies the signal to gradually reduce flow, transitioning from constant speed operation to deceleration mode. This dynamic adaptation prevents sudden stops and reduces shock forces while maintaining efficient operation during normal travel.
Solution Approach 2:
The system employs position feedback from sensors that continuously monitor piston location. The controller receives this feedback and automatically modifies valve assembly operation when the piston enters a predetermined deceleration zone near the end-stop. This closed-loop feedback mechanism ensures reliable operation by preventing excessive forces without requiring manual intervention or complex mechanical cushioning.
2Productivity
If the piston moves at given speed throughout the stroke, then productivity is maintained, but stress on mechanical components increases due to inadequate speed control near end-stops
Solution Approach 1:
The controller is programmed to initiate deceleration before the piston reaches the end-stop by detecting position feedback from the deceleration zone threshold. This preliminary action of reducing speed in advance prevents high-impact stops and reduces stress on mechanical components while minimizing the impact on overall productivity through optimized control timing.
3Device complexity
If simple valve control is used, then device complexity is low, but the system cannot prevent sudden stops and shock forces at end-stops
Solution Approach 1:
The patent replaces complex mechanical cushioning devices, springs, or dampers with an electronically controlled valve assembly and position feedback system. This substitution maintains relatively simple device architecture while achieving superior reliability by using electronic control to prevent shock forces and sudden stops throughout the actuator stroke.
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 solution effectively reduces stress and prevents shock forces by gradually slowing down the piston and applying a force to prevent sudden stops, thereby enhancing the reliability and longevity of hydraulic systems.
Implementation Method 1
cause the hydraulic fluid within the second chamber to apply a force on the piston in a direction away from the end-stop
Implementation Method 2
provide the pressurized hydraulic fluid to the first chamber and allow hydraulic fluid in the second chamber to flow from the second chamber to the return line
Data Source
AI summary
In some applications, a piston of a hydraulic actuator may move at high speeds, and large undesired forces may be generated if the piston reaches an end-stop of the hydraulic actuator at a high speed. The undesired forces may, for example, cause mechanical damage in the hydraulic actuator. A controller may receive information indicative of the piston reaching a first position at a first threshold distance from the end-stop, and, in response, may modify a signal to a valve assembly controlling flow of hydraulic fluid to and from the hydraulic actuator. Further, the controller may receive information indicative of the piston reaching a second position at a second threshold distance closer to the end-stop of the hydraulic actuator, and, in response, the controller may further modify the signal to the valve assembly so as to apply a force on the piston in a away from the end-stop.