Electrohydrostatic Cylinder Pressure Sensing for Safe Setup Speed
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Solution Overview
Problem
The existing electrohydrostatic systems for controlling the setup speed of hydraulic cylinders are cost-intensive and require significant computing power, limiting the functionality of other components, and adapting classic hydraulic systems to electrohydrostatic systems is inefficient and expensive due to the need for large, high-pressure safety valves and orifices.
Innovation Solution
An electrohydrostatic system that utilizes a motor control device with a 'Safe Torque Off' function to prevent energy introduction, eliminating the need for the 'Safe Limited Speed' function, and employs a pressure sensor to detect pressure increases, activating the motor pump unit only when necessary, with safety valves and a fixed orifice designed for the hanging load pressure, ensuring safe setup speeds without overpressuring components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the 'Safe Limited Speed' function is used in the motor control device to control setup speed, then the setup speed can be controlled, but the computing power is significantly consumed and costs increase
Solution Approach 1:
The patent replaces the electronic control system (motor control device with Safe Limited Speed function) with a mechanical flow restriction system (fixed orifice plate). The orifice plate physically limits the hydraulic flow rate, thereby controlling the setup speed mechanically rather than through electronic speed monitoring and control algorithms, eliminating the computational burden while maintaining speed control.
Solution Approach 2:
The patent uses a hydraulic flow restriction approach by installing a fixed orifice plate in the hydraulic circuit. The orifice plate creates a pressure drop that limits the flow rate to the hydraulic cylinder, controlling the setup speed through hydraulic principles rather than electronic control, thus avoiding the need for complex computing resources.
2Reliability
If classic hydraulic system components (safety valves, fixed orifices) are adapted for electrohydrostatic system, then safety can be maintained, but large and costly components are required due to high pressure requirements
Solution Approach 1:
The patent changes the pressure parameter management by using the fixed orifice plate to create a controlled pressure drop only when needed for setup operations. The system operates at lower pressures during normal operation and only generates high pressure transiently when the orifice plate restricts flow during setup, allowing the use of smaller, less expensive components compared to systems that must continuously handle high pressures.
Solution Approach 2:
The fixed orifice plate is designed to provide excessive flow restriction during setup operations, ensuring that even under maximum suspended load conditions, the setup speed remains limited. This partial action (only during setup) allows the use of a simple, small orifice plate rather than requiring large, expensive safety valves that would be needed for continuous high-pressure control.
3Force
If the motor pump unit operates at high pressure for suspended load support, then the load can be held, but excessive energy is lost when throttling through fixed orifice plate
Solution Approach 1:
The patent makes the system dynamic by using the motor control device to adjust the motor pump unit's output pressure and flow rate in real-time. During setup operations, the pump delivers high flow at moderate pressure through the fixed orifice. During normal operation and suspended load support, the pump adjusts to deliver only the minimum required flow at the necessary pressure, minimizing energy loss through the orifice while maintaining load support capability.
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 reduces the computational burden, eliminates the need for costly and complex safety valves, and ensures safe setup speeds by dynamically managing pressure and energy input, preventing excessive speed and energy loss, thus enhancing system efficiency and cost-effectiveness.
Implementation Method 1
employs a pressure sensor to detect pressure increases, activating the motor pump unit only when necessary
Implementation Method 2
with safety valves and a fixed orifice designed for the hanging load pressure, ensuring safe setup speeds
Implementation Method 3
motor pump unit for pressure supply
Data Source
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AI summary
The present invention relates to an electrohydrostatic system having a hydraulic cylinder comprising a first cylinder chamber and a second cylinder chamber. Furthermore, the electrohydrostatic system has a fluid hydraulic supply device for providing a hydraulic fluid, a fluid hydraulic motor pump unit designed to provide a fluid hydraulic volume flow in order to move the hydraulic cylinder. A motor control device is designed to provide a rated current for an electrical drive of the fluid hydraulic motor pump unit. Moreover, the electrohydrostatic system has at least one fluid hydraulic safety valve, which on a first valve side is connected to one of the cylinder chambers of the hydraulic cylinder and on a second valve side is connected to the fluid hydraulic motor pump unit. The fluid hydraulic safety valve can be bridged via a bypass connection with a fixed orifice plate, the bypass connection being connected to the first valve side and to the second valve side of the at least one fluid hydraulic safety valve. Moreover, the electrohydrostatic system has a pressure sensor which is connected to one of the cylinder chambers of the hydraulic cylinder. The pressure sensor is designed to detect a fluid hydraulic pressure on one of the cylinder chambers and, according to the detected fluid hydraulic pressure, to provide an enabling signal for the motor control device to provide the rated current for the electrical drive of the fluid hydraulic motor pump unit.