Brushless DC Valve Control with Virtual Current Feedback
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Solution Overview
Problem
Existing valve control systems using brushed DC motors face issues with maintainability due to brush wear, and voltage control methods result in oscillatory responses and torque tracking defects, especially at high speeds, while systems with coarse resolution sensors struggle to accurately estimate counter electromotive forces and currents, leading to valve collisions and instability.
Innovation Solution
A valve control device utilizing a brushless DC motor with a pulse output sensor and a current control system that calculates phase current commands and induced voltages, applying phase corrections to suppress sampling period influences, enabling virtual current feedback and direct torque control to enhance response speed and prevent valve collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If voltage control method is used for motor control, then device complexity is reduced, but torque tracking characteristic deteriorates and oscillatory response occurs
Solution Approach 1:
The patent implements a current feedback mechanism where the actual current flowing through the motor winding is measured and fed back to the control system. This allows the controller to adjust the voltage command in real-time to compensate for current lag caused by inductance, thereby maintaining accurate torque tracking without requiring complex predictive algorithms.
Solution Approach 2:
The patent replaces the mechanical brush-commutator system of traditional DC motors with an electronic commutation system using Hall effect sensors and power electronics. This substitution eliminates brush wear and sparks while enabling precise control of phase currents through electronic switching, thereby improving reliability without significantly increasing system complexity.
2Reliability
If current control method is used to overcome inductance component, then torque control stability improves, but device complexity increases due to current feedback requirements
Solution Approach 1:
The patent implements a current feedback mechanism where the actual current flowing through the motor winding is measured and fed back to the control system. This allows the controller to adjust the voltage command in real-time to compensate for current lag caused by inductance, thereby maintaining accurate torque tracking without requiring complex predictive algorithms.
3Reliability
If brushless DC motor is used to eliminate brush wear, then reliability improves, but manufacturing precision requirements increase for rotor positioning
Solution Approach 1:
The patent replaces the mechanical brush-commutator system of traditional DC motors with an electronic commutation system using Hall effect sensors and power electronics. This substitution eliminates brush wear and sparks while enabling precise control of phase currents through electronic switching, thereby improving reliability without significantly increasing system complexity.
Solution Approach 2:
The patent implements a sensorless control mechanism where the controller monitors the back-EMF and current characteristics of the motor phases to automatically determine rotor position and adjust commutation timing. This self-adjusting capability compensates for manufacturing tolerances in rotor positioning, maintaining reliable operation without requiring ultra-precise mechanical alignment.
4Device complexity
If coarse resolution sensor is used for position detection, then device complexity is reduced, but current and counter electromotive force estimation accuracy deteriorates
Solution Approach 1:
The patent introduces an intermediary estimation algorithm that uses readily measurable quantities (terminal voltage, phase resistance, inductance, and coarse position data) to calculate phase currents and back-EMF. This software-based intermediary layer compensates for the limited resolution of the position sensor, providing accurate current estimates without requiring high-precision hardware sensors.
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 allows for accurate estimation of phase currents and induced voltages, reducing the risk of valve collisions and maintaining stability across varying environmental temperatures, while eliminating the need for current sensors and improving torque control at low speeds.
Implementation Method 1
a valve control device for a valve mechanism to which a return torque is applied in an opening direction or a closing direction of a valve, the valve control device controlling opening and closing of the valve in a balance between the return torque and a motor torque provided by control of a motor for applying a torque in a direction opposite to a direction of the return torque
Implementation Method 2
generating a phase voltage command of the each of the phases based on a current deviation between the phase current command and a fed-back estimated current of the each of the phases
Implementation Method 3
obtaining an estimated induced voltage of the each of the phases based on the electrical angle detection position and an induced voltage actually measured in advance
Data Source
AI summary
In opening/closing control for the valve mechanism to which the return torque is applied in an opening direction or a closing direction of the valve, provided are a position control system for outputting a q-axis current command based on a position deviation between a target position command directed to the brushless DC motor and the coarse present position of the motor obtained by using the position detection sensor of a pulse output type, and a current control system in which a virtual current feedback is built for outputting a phase voltage command without a current sensor based on the q-axis current command and the coarse present position of the motor obtained by using the position detection sensor of the pulse output type.