Sensorless Motor Startup Modes for Fluctuating Load Torque
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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 load fluctuation condition and activates the motor in either a normal mode or a high torque mode, where the rotation speed increase is gentler in the high torque mode 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, allowing the system to adapt between fast activation (high acceleration) when load is light and reliable activation (low acceleration) when load is heavy, thus resolving the contradiction between activation speed and reliability
Solution Approach 2:
The patent changes the parameter of acceleration torque from a predetermined fixed value to a variable value that depends on load conditions. By detecting load torque and selecting appropriate acceleration torque values from multiple levels, the system optimizes both activation speed and reliability based on actual operating conditions
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 resolves this contradiction by making acceleration torque a variable parameter based on load detection. When load torque is detected to be heavy, a lower acceleration torque is applied to prevent step-out (maintaining reliability). When load is light, higher acceleration torque is applied to reach target speed faster (reducing time loss). This dynamic parameter adjustment optimizes both reliability and time efficiency
3Device complexity
If load fluctuation is not considered, then control system is simple, but activation failure occurs due to unexpected load torque
Solution Approach 1:
The patent applies feedback by detecting the actual load torque during activation and using this information to adjust the acceleration torque. The control unit continuously monitors load conditions and modifies control parameters in real-time, creating a closed-loop system that ensures reliable activation despite load fluctuations while keeping the overall system structure relatively simple
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 based on load conditions, ensuring stable motor activation even under heavy 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.