Hydraulic Pump Speed Control via Motor Simulation
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Solution Overview
Problem
Existing control systems for hydraulic actuators in plastic injection molding machines face challenges in precisely and quickly compensating for deviations in pressure or delivery quantity, leading to slow and inefficient energy use due to motor slippage and overrun during acceleration processes.
Innovation Solution
A method and control device that utilize a speed-controlled electric motor driving a variable displacement pump, with a speed profile created to adjust motor speed and volume setting, accounting for speed deviations caused by slippage and overrun, allowing for precise regulation of pressure medium supply without speed sensors, using motor simulation to calculate actual speed and compensate for deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the speed of the electric motor is controlled according to a default speed profile, then energy efficiency is improved, but the control response becomes slow and deviations in pressure or delivery quantity cannot be compensated quickly
Solution Approach 1:
The patent implements feedback control by continuously determining the actual speed of the electric motor and comparing it with the target speed from the speed profile. The speed deviation is calculated and used to adjust the volume setting of the variable displacement pump in real-time, enabling quick compensation of pressure or delivery quantity deviations while maintaining energy efficiency.
Solution Approach 2:
The system dynamically adjusts the volume setting of the variable displacement pump based on the calculated speed deviation. Instead of using a fixed control strategy, the pump volume is continuously adapted to the actual motor speed conditions, allowing the system to respond quickly to deviations while operating along an energy-optimized speed profile.
2Measurement precision
If speed sensors are used to detect motor speed for precise control, then control precision is improved, but device complexity and cost increase
Solution Approach 1:
The system uses the existing control infrastructure to determine motor speed without additional sensors. The speed is calculated based on the relationship between the pump's volume setting, the hydraulic actuator's requirements, and the motor's electrical characteristics already present in the control circuit, making the system self-sufficient.
Solution Approach 2:
The patent uses the variable displacement pump as an intermediary to infer motor speed. By measuring the pump's actual delivery quantity and comparing it with the expected delivery based on motor commands, the system calculates speed deviation indirectly through the pump's performance characteristics rather than directly measuring motor speed.
3Manufacturing precision
If the volume setting of the variable displacement pump is adjusted frequently to compensate for speed deviations, then pressure control precision is improved, but device wear and energy consumption increase
Solution Approach 1:
The system calculates the speed deviation in advance based on the difference between target and actual speeds, and proactively adjusts the pump volume setting before significant pressure deviations occur. This preliminary adjustment prevents larger errors from developing, reducing the need for frequent corrective actions and minimizing wear and energy consumption.
Data Source
AI summary
The method involves supplying a pressurizing medium quantity to an actuator by a variable displacement pump (13). A speed deviation is detected, where the speed deviation results from the deviation of a speed (n) of an electric motor (14) from a target value for a speed (ns). An independent claim is included for a regulating circuit for controlling pressurizing medium supply for hydraulic actuator of a cyclically working machine.