Motor Current Control With Integrator Pause During Detection Gaps
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Solution Overview
Problem
Existing motor control devices experience unstable control when current detection is unavailable, leading to erroneous deviations and instability due to integral control using estimated currents.
Innovation Solution
A motor control device with an inverter, calculation unit, speed estimation unit, and current control unit that performs integral control only when current detection is available, switching to proportional control during undetectable periods, and adjusts control amounts based on current-undetectable-period information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving 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 applies dynamics by making the control method adaptive based on detection availability. The controller dynamically switches between using detected current and estimated current, and adjusts integrator operation based on the detection state. This resolves the contradiction by allowing integral control to continue overall (maintaining continuity) while pausing the integrator during undetected periods (preventing stability deterioration).
Solution Approach 2:
The patent changes the operational parameter of the integrator based on current detection status. When current is undetectable, the integrator is stopped; when current is detectable, the integrator operates normally. This parameter change resolves the contradiction by preventing error accumulation during undetected periods while maintaining control continuity through proportional control and estimated current usage.
2Device complexity
If one-shunt current detection method is used to reduce hardware, then device complexity is reduced, but measurement precision deteriorates during certain control periods when current cannot be detected
Solution Approach 1:
The patent introduces an intermediary approach by using estimated current as a substitute when direct current detection is unavailable. The controller calculates estimated current based on the relationship between phases and uses this estimation during periods when the one-shunt method cannot detect current. This resolves the contradiction by maintaining measurement precision through estimation rather than requiring additional hardware.
Solution Approach 2:
The patent applies partial action by using the one-shunt current detection method only during periods when it can provide accurate measurements, and switching to estimated current during periods when it cannot. This partial usage resolves the contradiction by accepting the limitations of the simplified hardware approach while maintaining overall system performance through selective operation.
3Speed
If proportional control is performed using estimated current during undetectable periods, then control responsiveness is maintained, but control precision deteriorates compared to using detected current
Solution Approach 1:
The patent applies periodic action by alternating between using detected current (when available) and estimated current (when detection is unavailable). The controller periodically switches between these two modes based on detection status, allowing proportional control to remain responsive while accepting reduced precision during estimation periods. This resolves the contradiction by maintaining responsiveness through continuous control action while being honest about precision limitations during undetected periods.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3C
AI summary
[Object] There is provided a motor control device capable of realizing stable control of a motor. [Solving Means] A motor control device according to an embodiment of the present invention 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, stops performing the integral control in a control period in which the detection current could not be detected, and controls the motor current such that the speed estimated by the speed estimation unit is a command speed.