Hydraulic Pump Speed Control for Pressure Stability
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Solution Overview
Problem
The controller in existing hydraulic systems generates unstable rotational frequency commands for variable speed motors due to pressure sensor offset, hysteresis, and harmonic noise, leading to unstable motor operation and energy inefficiency.
Innovation Solution
A hydraulic pump operating device that uses a pressure variation range detector and speed controller to manage the speed of the variable speed motor based on the range of discharge pressure variation, rather than absolute pressure, and includes features like two-stage rotational frequency switching and high-pass filtering to stabilize control and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the controller generates rotational frequency commands directly based on pressure sensor detection values, then the control responds quickly to pressure changes, but the control becomes unstable due to sensor offset, hysteresis, and noise
Solution Approach 1:
The patent introduces an intermediary processing mechanism between the pressure sensor and the rotational frequency command generation. Instead of directly using the raw pressure detection value, the system uses the rate of change (derivative) of the pressure detection value as an intermediary parameter to generate the rotational frequency command. This intermediary approach filters out sensor noise and hysteresis effects while preserving the essential pressure change information, thereby stabilizing the control without sacrificing response speed.
2Measurement precision
If the rotational frequency is continuously adjusted according to pressure detection values, then the discharge pressure is controlled precisely, but energy is wasted due to unnecessary motor operation during pressure maintained states
Solution Approach 1:
The patent implements a dynamic control strategy that adapts the motor operation mode based on the system state. By detecting whether the hydraulic pump is in a pressure maintained state (where pressure fluctuations are within a predetermined range), the system dynamically switches between precise pressure control mode and energy-saving idle mode. This dynamic adjustment allows the motor to maintain low-speed rotation during pressure maintained states, significantly reducing energy consumption while preserving the ability to quickly resume precise control when pressure deviations occur.
3Reliability
If the pressure adjustment mechanism mechanically controls discharge pressure, then the pressure control is reliable, but the system complexity increases and energy efficiency decreases
Solution Approach 1:
The patent replaces the traditional mechanical pressure adjustment mechanism with an electronically controlled system. Instead of using mechanical components like pressure relief valves or adjustable restrictors, the system uses a sensor to detect pressure and an inverter to control the motor speed, thereby controlling the pump's discharge pressure. This substitution eliminates complex mechanical adjustment mechanisms while maintaining reliable pressure control through electronic feedback and control algorithms.
Data Source
AI summary
The rotational frequency of a variable speed motor is set to a normal rotational frequency setting value (N1). A pressure variation range (&Dgr;P) is detected based on a pressure detection value P, of a variable displacement pump, detected by a pressure detector. It is determined whether a determination that the detected pressure variation range (&Dgr;P) is less than or equal to a pressure maintained state detection level (L1) has been continuously given for a period indicated by a timer setting value (T1). If the determination that the detected pressure variation range (&Dgr;P) is less than or equal to the pressure maintained state detection level (L1) has been continuously given for the predetermined period, then it is detected that the current state is a pressure maintained state, and the rotational frequency of the variable speed motor is switched from the normal rotational frequency setting value N1 to a pressure maintaining rotational frequency setting value (N2(<N1)).