Dynamic Motor Resistance Compensation for Mobility Vehicles
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Solution Overview
Problem
Existing motor drive systems in mobility vehicles, particularly those with permanent magnet or shunt wound motors, face challenges in accurately compensating for armature resistance changes, leading to unstable speed regulation and potential safety issues due to variable motor resistance influenced by current, temperature, and time, which traditional methods like IXR load compensation and back EMF measurement fail to address effectively.
Innovation Solution
A method and control system that dynamically updates a motor performance profile to develop a compensation term for controlling DC brush motors, using a stored profile of resistance-based variables associated with motor performance parameters, allowing real-time compensation and monitoring of motor resistance, temperature, and predicting operational scenarios to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional IXR load compensation or back EMF measurement methods are used to compensate for armature resistance, then speed regulation is improved, but the compensation accuracy deteriorates because motor resistance is a variable that is a complex function of current, temperature, speed and time
Solution Approach 1:
The patent applies dynamics by transitioning from static resistance measurement (at motor rest) to dynamic resistance measurement (during motor operation). The system continuously measures armature resistance while the motor is running, capturing the complex variations caused by current, temperature, speed and time. This dynamic approach allows the compensation system to adapt to changing motor conditions in real-time, resolving the contradiction between reliability and measurement precision.
Solution Approach 2:
The patent implements feedback by using the dynamically measured armature resistance values to continuously update the compensation calculations. The measured resistance feeds back into the control system, which adjusts the voltage compensation in real-time based on the actual motor conditions. This closed-loop feedback mechanism ensures accurate speed regulation despite the complex variable nature of motor resistance.
2Measurement precision
If motor resistance is measured at stall position, then a resistance value can be obtained, but the measurement becomes inaccurate and varying due to the large number of different positions in which the brush within the motor may stop
Solution Approach 1:
The patent resolves this contradiction by measuring resistance dynamically during motor operation rather than statically at stall position. By taking measurements while the motor is running and the brush is in motion, the system avoids the variability caused by different brush stop positions. The dynamic measurement approach maintains both measurement precision and operational simplicity.
Solution Approach 2:
The system performs resistance measurement during normal motor operation, utilizing the motor's own operational conditions (current flow, rotation) to enable accurate measurement. The motor's normal operation provides the necessary conditions for measurement, eliminating the need for separate stall-position measurement procedures.
3Reliability
If under-compensation is performed to avoid harsh and unstable driving characteristics, then safety is improved, but driving precision is compromised
Solution Approach 1:
The patent uses real-time feedback from dynamic resistance measurement to optimize the compensation level. Instead of using fixed under-compensation, the system continuously adjusts the compensation amount based on actual measured resistance values. This allows the system to achieve both stability and precision by adapting the compensation to current operating conditions.
Solution Approach 2:
The system transitions from static under-compensation to dynamic compensation adjustment. By continuously measuring resistance during operation and adjusting compensation in real-time, the system can optimize the balance between stability and precision for each operating condition, rather than relying on conservative fixed under-compensation.
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
This approach ensures stable and accurate speed regulation, reduces the risk of motor damage, and provides timely maintenance alerts, enhancing the safety and reliability of mobility vehicles by continuously adapting to motor performance changes and monitoring potential issues.
Implementation Method 1
Another known method of compensating for motor resistance is described in US patent US 4,266,168. This describes a method of measuring the back EMF of a motor during use of the motor to generate a feedback signal that accounts for the motor's resistance.
Data Source
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AI summary
A method of controlling at least one motor in a motorised mobility vehicle, wherein the motor is part of a drive circuit for mobilising the mobility vehicle, the method comprising the steps of: utilising a stored profile of a motor performance parameter to develop a compensation term for controlling the motor, wherein the stored profile is of a resistance based variable associated with the motor as a function of a further variable and dynamically updating the compensation term when the mobility vehicle is in use.