BLDC Motor Control Circuit Gain Adjustment for Hold State Stability
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Solution Overview
Problem
Brushless direct-current (BLDC) motor systems in image forming apparatuses face challenges in stabilizing motor operation during the hold state, leading to oscillations and accelerated wear due to the difficulty in adjusting controller gains effectively to reduce positional errors.
Innovation Solution
The implementation of a control circuit with a gain adjuster that adjusts the proportional and integral gains of the control actions based on the operational state of the motor, switching to a second value during the hold state to minimize oscillations and stabilize the motor at zero rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the feedback controller performs corrective action to reduce positional error in hold state, then the motor position accuracy is improved, but motor oscillations occur causing accelerated wear and coordination issues
Solution Approach 1:
The control circuit dynamically switches between two operational modes: PID control mode for reducing positional error and oscillation suppression mode for stabilizing motor operation. This dynamic adaptation allows the system to optimize performance for different operational requirements, resolving the contradiction between position accuracy and operational stability
Solution Approach 2:
The system changes control parameters by switching between different control modes. In PID mode, proportional, integral, and derivative gains are applied for position correction. In oscillation suppression mode, the control parameters are adjusted to prioritize stability over position correction, thereby eliminating oscillations while maintaining acceptable position accuracy
2Measurement precision
If the PID controller adjusts gain to optimize steady operational state control, then the motor control precision is improved, but the motor cannot be stabilized in hold state
Solution Approach 1:
The control strategy is segmented into two distinct modes: PID control for steady operational state optimization and oscillation suppression control for hold state stabilization. Each mode is optimized for its specific function, allowing the system to achieve both high control precision during operation and stability during holding without compromise
3Adaptability or versatility
If the dual control system reduces PID gain progressively toward zero, then the transition to sliding-mode control is achieved, but oscillations cannot be immediately stopped in hold state
Solution Approach 1:
The control system proactively detects when the motor enters hold state and immediately switches to oscillation suppression mode before oscillations can develop. This preliminary action prevents the oscillation problem rather than attempting to correct it after occurrence, ensuring immediate stabilization while maintaining adaptability across different operational states
Data Source
AI summary
An electric motor system includes a brushless direct-current motor, a driver circuit, a position sensor, and a control circuit. The motor has an output shaft for transmitting torque. The driver circuit supplies power to the motor according to a control signal input thereto. The position sensor measures an angular, rotational position of the motor shaft. The control circuit controls operation of the motor. The control circuit includes a position sensor terminal, a reference terminal, a differential calculator, a controller, and a gain adjuster. The position sensor terminal receives a feedback signal. The reference terminal receives a reference signal. The differential calculator generates an error signal representing a difference between the measured and targeted rotational positions. The controller generates the control signal based on the error signal through a combination of control actions. The gain adjuster is connected to the controller to adjust a gain of each control action.