Motor Control System for Load Balancing and Stall Prevention
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Solution Overview
Problem
In systems with multiple electric motors driving a common assembly, such as a mower deck, the more heavily loaded motor may experience thermal or mechanical stress, leading to inadequate performance or reduced longevity due to uneven loading conditions.
Innovation Solution
A method and system where a first motor controller generates commanded speeds for both motors, with a speed monitor detecting observed speeds and adjusting the target rotor speed of the second motor based on the rate of change of the first motor's speed to prevent stall conditions by proportionally reducing the load on the more heavily loaded motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple electric motors are used to drive blades of a common assembly, then the power and productivity of the assembly are improved, but the more heavily loaded motor experiences thermal or mechanical stress leading to inadequate performance or reduced longevity
Solution Approach 1:
The system continuously monitors the operational status of each motor including current draw, temperature, and speed, then uses this feedback to dynamically adjust motor operation. The controller detects when a motor is becoming overloaded and responds by adjusting the operational parameters of other motors in the assembly to redistribute the load and prevent damage.
Solution Approach 2:
The system dynamically adjusts the operational parameters of motors based on real-time conditions rather than operating at fixed speeds or loads. The controller continuously modifies motor speed, power delivery, and operational timing to optimize performance while preventing any single motor from experiencing excessive thermal or mechanical stress.
2Productivity
If the more heavily loaded motor operates at higher power to maintain assembly performance, then the productivity of the common assembly is improved, but the thermal and mechanical stress on that motor increases reducing its longevity
Solution Approach 1:
Temperature and current sensors provide continuous feedback on motor thermal conditions to the controller. When a motor approaches dangerous temperature thresholds or shows signs of thermal stress, the controller receives this feedback and automatically adjusts the operational load on that motor, redistributing work to other motors in the assembly to maintain overall productivity while preventing thermal damage.
Solution Approach 2:
The system takes preliminary action by monitoring motor conditions and detecting early signs of thermal stress before critical damage occurs. By identifying trends in current draw, temperature rise, and operational patterns, the controller proactively adjusts motor loading to prevent thermal runaway or mechanical failure, rather than waiting for damage to occur.
3Adaptability or versatility
If the motor speeds are not synchronized, then each motor can operate independently to handle varying loads, but the uneven loading causes thermal or mechanical stress on the more heavily loaded motor
Solution Approach 1:
The system dynamically coordinates motor speeds and operational parameters based on real-time load conditions rather than maintaining fixed speed relationships. The controller continuously adjusts each motor's speed and power delivery to achieve optimal load distribution, allowing motors to operate at different speeds when necessary while preventing any single motor from experiencing excessive mechanical stress from uneven loading.
Solution Approach 2:
Speed sensors and controllers provide feedback on the rotational speed and load conditions of each motor. The controller uses this feedback to coordinate motor operation, adjusting speeds and power delivery to balance the mechanical load across all motors in the assembly, thereby maintaining adaptability to varying loads while reducing mechanical stress through coordinated operation.
Data Source
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AI summary
A first motor controller generates commanded speeds of a first rotor of a first electric motor for a first time interval and a second time interval. A first speed monitor detects observed speeds of the first rotor for the time intervals. A first ratio is determined based on a relationship between respective commanded speeds and corresponding observed speeds for the first time interval and the second time interval. A first data processor increments a persistence counter for the first motor if the first ratio increases or changes during the time intervals. A first motor deceleration is estimated if the persistence counter exceeds a stall limit count. A target rotor speed of a second motor is adjusted based on the estimated first motor rate of change to track the first motor rate of change (or first rotor speed) if the persistence counter exceeds the stall limit count.