Motor Controller Power Feedback Loop for Constant Torque
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Solution Overview
Problem
Brushless DC (BLDC) motor control systems face challenges in maintaining constant torque output due to varying power supply to the coils over time, leading to non-constant motor performance.
Innovation Solution
A motor control system that includes a motor control circuit coupled with a motor driver circuit, utilizing field effect transistors (FETs) and feedback loops to regulate power distribution across phases, ensuring consistent torque by adjusting pulse-width modulation (PWM) signals based on measured voltage and current, and using PI controllers to match desired speed and power references.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If pulse-width modulation (PWM) drive signals are used to control power to the motor coils, then the motor can be controlled to turn, but the power supplied to the coils rises and falls over time resulting in non-constant torque output
Solution Approach 1:
The patent implements a feedback control mechanism that monitors the actual power supplied to motor coils and adjusts the PWM duty cycle dynamically to maintain constant torque output. The controller measures the instantaneous power and compares it with the desired torque level, then modifies the PWM signal accordingly to compensate for power variations during coil energization phases.
Solution Approach 2:
The system dynamically adjusts the PWM duty cycle in real-time based on the motor's operating conditions and phase position. By making the control parameter (duty cycle) variable rather than fixed, the system adapts to the changing power requirements throughout the motor's rotation cycle, ensuring constant torque despite the periodic nature of coil energization.
2Duration of action of stationary object
If multiple coils are energized in sequence to enable continuous motor rotation, then the motor can spin continuously, but the phase-based energization causes power to rise and fall resulting in variable torque
Solution Approach 1:
The patent merges the control of multiple coils into a unified feedback control system that coordinates the energization of different phase coils. By integrating the power regulation across all phases through a common control algorithm, the system ensures that each coil receives the appropriate power level to maintain overall torque consistency, rather than treating each phase independently.
Solution Approach 2:
The system changes the PWM duty cycle parameter dynamically based on which coil phase is currently being energized and the motor's instantaneous state. Each phase receives a customized duty cycle adjustment to compensate for its specific power characteristics, ensuring that despite the sequential energization of different coils, the overall torque output remains constant.
Data Source
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AI summary
A motor control system includes a motor; a motor and a motor control circuit coupled to the motor to provide power to the motor. The motor control circuit includes a power feedback loop having a power reference circuit to provide a reference power level and a power control circuit configured to provide a constant power level to the motor so that the motor operates with a substantially constant power output. The constant power level is proportional to the reference power level. Thus, the motor also provides substantially constant torque when the motor is at a constant speed.