Motor Current Control Switching for One-Shunt Detection Gaps
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Solution Overview
Problem
Existing motor control devices experience unstable control when integral control is performed using estimated currents, particularly during periods where current detection is not possible, leading to erroneous deviations and instability.
Innovation Solution
A motor control device that includes an inverter, calculation unit, speed estimation unit, and current control unit, which performs integral control only when current detection is possible, and uses proportional control during undetectable periods, with adjustments based on current-undetectable-control-period information to stabilize control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If integral control is performed using estimated current in control periods where current cannot be detected, then control continuity is maintained, but control stability deteriorates and erroneous deviations accumulate
Solution Approach 1:
The patent dynamically adjusts the control strategy based on current detectability. When current can be detected, integral control is performed using detected current; when current cannot be detected, the system switches to using estimated current with proportional control only. This dynamic adaptation resolves the contradiction by maintaining control continuity while preventing stability deterioration through conditional control mode switching.
Solution Approach 2:
The patent changes the control parameters (integral control gain, control mode) based on the detectability of current. By modifying the control algorithm parameters according to the availability of current information, the system maintains stability while ensuring continuous control operation. This parameter adaptation allows the system to handle periods of undetectable current without accumulating erroneous deviations.
2Device complexity
If one-shunt current detection method is used to reduce detection components, then device complexity is reduced, but measurement precision deteriorates during periods when current cannot be detected
Solution Approach 1:
The patent segments the control periods into detectable and undetectable phases. During detectable phases, precise current measurement is performed using the one-shunt method. During undetectable phases, the system switches to estimated current with proportional control, preventing precision deterioration. This temporal segmentation allows the use of simplified hardware while maintaining measurement precision when needed.
Solution Approach 2:
The patent introduces an intermediary approach by using estimated current as a substitute during undetectable periods. Instead of relying solely on the simplified one-shunt detection, the system uses estimation algorithms to provide current information when direct detection is unavailable, thereby maintaining measurement precision without adding complex detection components.
3Reliability
If proportional control is performed using estimated current during undetectable periods, then control stability is maintained, but control precision deteriorates compared to integral control with detected current
Solution Approach 1:
The patent implements periodic switching between integral control (when current is detectable) and proportional control (when current is undetectable). This periodic action ensures that high-precision integral control is applied whenever possible, while proportional control maintains stability during undetectable periods. The alternating control strategies balance stability and precision requirements across different operational phases.
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
Stable motor control is achieved even in periods where current detection is unavailable, ensuring accurate and responsive motor operation by preventing control instability and adjusting control amounts based on detection availability.
Implementation Method 1
The inverter converts a direct current (DC) voltage supplied from a DC power source into an alternating current (AC) voltage and applies the AC voltage to a motor by PWM control
Implementation Method 2
The calculation unit detects a bus current of the inverter using a resistor connected between the DC power source and the inverter
Data Source
AI summary
A motor control device includes: an inverter; a calculation unit; a speed estimation unit; and a current control unit. The inverter converts a direct current (DC) voltage supplied from a DC power source into an alternating current (AC) voltage and applies the AC voltage to a motor by PWM control. The calculation unit detects a bus current of the inverter using a resistor connected between the DC power source and the inverter and calculates, on the basis of the bus current, a motor current flowing through the motor at intervals of a predetermined control period. The speed estimation unit estimates a motor speed on the basis of a detection current that is a motor current detected by being calculated by the calculation unit. The current control unit includes an integrator that performs integral control at intervals of the predetermined control period.