Multi-Motor PWM Switching Control With Delayed Current Feedback
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Solution Overview
Problem
Existing motor systems struggle to individually control the rotation speed and direction of multiple motors driven simultaneously, leading to potential unintended outputs near switching timing.
Innovation Solution
A motor system comprising a motor driver, a current detector, and a switcher, where the motor driver outputs power based on a PWM duty ratio computed from detected current, and the switcher cyclically switches the target motor among multiple motors, ensuring correct control timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single motor driver is used to drive multiple motors simultaneously via switching circuitry, then device complexity is reduced, but control precision deteriorates due to unintended outputs near switching timing
Solution Approach 1:
The patent segments the control process into distinct phases: detection phase (detecting current when motor A is target), computation phase (computing PWM duty ratio), and application phase (applying control in next cycle when motor A is target again). This temporal segmentation prevents interference between multiple motors and ensures precise control application to the correct motor.
Solution Approach 2:
The patent performs preliminary detection of current in one cycle, then uses this detected current to compute PWM duty ratio that is applied in the next cycle when the same motor becomes target again. This preliminary action allows accurate control based on actual motor state while avoiding unintended outputs during switching transitions.
2Ease of operation
If switching circuitry is used to distribute power to multiple motors, then ease of operation is improved by enabling individual motor control, but reliability deteriorates due to risk of unintended outputs
Solution Approach 1:
The patent implements feedback by detecting the actual current flowing through the motor in one cycle, computing the PWM duty ratio based on this detected current, and applying the control in the next cycle. This closed-loop feedback ensures that control is based on actual motor state, improving both individual control capability and reliability by preventing unintended outputs.
Solution Approach 2:
The patent introduces a control cycle intermediary mechanism where the detected current from one cycle serves as the basis for computing PWM duty ratio that is applied in the next cycle. This intermediary approach decouples the detection and application moments, ensuring that control is applied to the correct motor at the correct time, thus improving reliability.
Data Source
AI summary
In a motor system, a switcher selectively switches a target motor, which is a target to be supplied with electric power output by a motor driver and a target to be detected for a current by a current sensor, among a plurality of motors. The switcher cyclically switches the target motor among the plurality of motors. When the current of the target motor is detected by the current sensor, the motor driver is controlled to output the electric power based on a PWM duty ratio computed based on the current, at a timing when the motor in which the current is detected is again the target motor, in a cycle after the cycle in which the current is detected.