Single-Resistor Motor Current Feedback Beyond the Sampling Dead Zone
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Solution Overview
Problem
Existing motor control systems using a single resistor for current sampling face a current sampling dead zone, leading to motor noise and increased cost when using PWM phase shift, and additional power consumption with multiple resistors.
Innovation Solution
A single-resistor measurement method that restores three-phase feedback current by obtaining currents outside and inside the dead zone using on-tube voltage drop and switch-on resistance, without requiring PWM phase shift, thus avoiding noise and cost issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PWM phase shift is used to measure current in the dead zone, then current measurement accuracy is improved, but motor noise increases due to asymmetry of three-phase PWM
Solution Approach 1:
The patent changes the measurement parameter from direct current sampling to on-tube voltage drop sampling. By measuring the voltage drop across the lower tube during switching and using the switch-on resistance to calculate current, the system obtains accurate current data without introducing PWM asymmetry, thus eliminating motor noise while maintaining measurement precision.
2Object-affected harmful factors
If three resistors or two resistors on lower bridge arm are used for current sampling, then current sampling dead zone is avoided and motor noise is reduced, but current sampling cost increases
Solution Approach 1:
The patent makes the lower tube serve multiple functions: it acts as both a switching device and a current sensing element. By measuring the on-tube voltage drop and using the known switch-on resistance to calculate current, the system eliminates the need for separate current sampling resistors, reducing component count and cost while maintaining low noise performance.
3Measurement precision
If three resistors or two resistors on lower bridge arm are used for current sampling, then current sampling dead zone is avoided, but additional power consumption is introduced
Solution Approach 1:
The patent eliminates dedicated current sampling resistors by using the lower tube's inherent on-tube voltage drop for current measurement. This multi-functional approach removes the continuous power consumption associated with resistive sampling while maintaining accurate current measurement coverage, including in the dead zone.
4Device complexity
If single resistor is used for current sampling, then cost is reduced and power consumption is minimized, but current sampling dead zone is introduced
Solution Approach 1:
The patent performs preliminary measurement of the lower tube's switch-on resistance characteristics. By having this resistance data available beforehand, the system can accurately calculate current from the on-tube voltage drop during the dead zone period, extending measurement coverage without requiring additional hardware beyond the single resistor.
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
Effectively restores three-phase feedback current without PWM phase shift, reducing noise, cost, and power consumption, while improving speed control accuracy and range.
Implementation Method 1
obtaining an on-tube voltage drop when the lower tube of the at least one phase bridge arm in the three-phase inverter bridge is switched on; determining, based on the switch-on current and the on-tube voltage drop when the lower tube of the at least one phase bridge arm in the three-phase inverter bridge is switched on, a switch-on resistance
Data Source
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AI summary
Provided are a single-resistor measurement method, a motor control method, a controller, and a control system. The method includes: (S10) obtaining a direct-current bus current flowing through the single sampling resistor, and determining, based on the direct-current bus current, a switch-on current when a lower tube of at least one phase bridge arm is switched on; (S20) obtaining an on-tube voltage drop when the lower tube of the at least one phase bridge arm is switched on; (S30) determining, based on the switch-on current and the on-tube voltage drop when the lower tube of the at least one phase bridge arm is switched on, a switch-on resistance when the lower tube of the at least one phase bridge arm is switched on; and (S40) determining, based on the direct-current bus current, a three-phase current outside a current measurement dead zone; determining, based on the on-tube voltage drop and the switch-on resistance, a three-phase current inside the current measurement dead zone; and determining, based on the three-phase current outside the current measurement dead zone and the three-phase current inside the current measurement dead zone, a three-phase feedback current of the motor.