Sensorless Motor Startup Mode Switching for Fluctuating Loads
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Solution Overview
Problem
Sensorless motor control systems face activation failures due to fluctuating loads, particularly in image forming apparatuses, where the load torque can exceed the output torque during forced commutation control, leading to step-outs.
Innovation Solution
A motor control apparatus that determines the activation mode based on load conditions, switching to a high torque mode when the load is heavy and a normal mode otherwise, with the high torque mode featuring a gentler increase in rotation speed to prevent activation failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If forced commutation control is used with predetermined current value, then motor activation is simple and fast, but activation failure occurs when load torque exceeds output torque
Solution Approach 1:
The patent applies dynamics by making the acceleration torque variable rather than fixed. The control unit dynamically adjusts the acceleration torque based on detected load torque magnitude, switching between first acceleration torque (for light loads) and second acceleration torque (for heavy loads). This dynamic adaptation resolves the contradiction by enabling fast activation when possible while ensuring reliability when load is heavy.
Solution Approach 2:
The patent changes the parameter of acceleration torque based on load conditions. By detecting load torque and selecting different acceleration torque values accordingly, the system adapts the motor control parameters to match actual operating conditions, thereby preventing activation failure under heavy load while maintaining efficiency under light load.
2Reliability
If acceleration torque is increased to prevent step-out under heavy load, then activation reliability improves, but time to reach target speed increases
Solution Approach 1:
The patent changes acceleration torque parameter based on load torque detection. When load torque exceeds a threshold, the system switches to second acceleration torque (higher value) to ensure reliable activation. When load is light, it uses first acceleration torque (lower value) to minimize activation time. This conditional parameter adjustment resolves the time-reliability contradiction.
Solution Approach 2:
The system dynamically selects acceleration torque based on real-time load detection. This dynamic adaptation allows the motor to use optimal acceleration values for each load condition, achieving both fast activation when possible and reliable activation when necessary, thereby resolving the contradiction between speed and reliability.
3Device complexity
If sensorless control is used without position sensor, then device complexity is reduced, but activation control precision deteriorates under fluctuating loads
Solution Approach 1:
The patent implements feedback by detecting load torque during activation and using this information to adjust acceleration torque. The control unit continuously monitors load conditions and adapts control parameters accordingly, compensating for the lack of position sensor feedback and maintaining control precision under fluctuating loads.
Solution Approach 2:
The system performs preliminary detection of load torque before executing the activation sequence. By knowing the load condition in advance, the control unit can pre-select the appropriate acceleration torque value, ensuring precise control from the start of activation without requiring complex sensor feedback during the critical acceleration phase.
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
The solution effectively suppresses activation failures by adjusting the acceleration torque according to load conditions, ensuring stable motor activation even under varying loads, although it may prolong the time to reach the target speed.
Implementation Method 1
a configuration for detecting a stop position of a rotor by using a characteristic that an inductance value of a coil of a motor changes according to the stop position of the rotor
Implementation Method 2
the motor control apparatus can detect the rotation position and the rotation speed of the rotor by an induced voltage generated in a coil
Data Source
AI summary
A motor control apparatus includes: a motor configured to drive a load; and a control unit configured to control the motor. The control unit is configured to, when activating the motor, determine whether a predetermined condition for determining that fluctuation in magnitude of the load occurs is satisfied, activate the motor in a first mode when the predetermined condition is satisfied, and activate the motor in a second mode when the predetermined condition is not satisfied, and the first mode is a mode in which an increase in rotation speed of the motor is gentler than an increase in rotation speed of the motor in the second mode.