Motor Rotor Position Compensation for Sensor Latency Noise
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Solution Overview
Problem
Existing motor control systems using low-cost position sensors often suffer from noise and inaccuracies due to latency and variable latency in rotor position measurements, particularly at low motor speeds or torque levels, which can lead to unwanted vibrations and noise in applications like automotive systems.
Innovation Solution
A method and motor circuit configuration that involves a microcontroller, a position sensor, and a communication network to periodically request rotor position and velocity estimates from the sensor. The method modifies the received rotor position value using an ageing signal and velocity to generate a modified angular position signal, which is then used to generate control signals for the motor, thereby compensating for latency and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a low-cost position sensor is used to reduce cost, then cost is reduced, but measurement precision and reliability deteriorate due to latency and variable latency in rotor position measurements
Solution Approach 1:
The system performs preliminary actions by requesting rotor position data at optimized intervals and using predictive algorithms to estimate current position based on previous measurements and motor velocity. This compensates for the inherent latency in low-cost sensors by proactively preparing position estimates before they are needed for control decisions.
Solution Approach 2:
The system implements feedback mechanisms where the microcontroller continuously monitors the age of position data and adjusts control strategies based on latency conditions. Velocity feedback is also used to predict position changes and compensate for measurement delays, maintaining control accuracy despite using lower-cost sensing components.
2Measurement precision
If PID control is used to achieve precise motor control, then control precision is improved, but noise and vibrations increase due to feedback errors and harmonics
Solution Approach 1:
The system applies preliminary anti-action by detecting potential noise and vibration issues before they occur. By monitoring position measurement quality and predicting when feedback errors might generate harmful harmonics, the system proactively adjusts control parameters or reduces feedback gain to prevent noise and vibrations before they affect motor operation.
3Speed
If high-frequency PWM signals are used to improve control response, then control speed is improved, but noise and vibrations increase due to audible harmonics
Solution Approach 1:
The system dynamically changes PWM parameters based on operating conditions. When noise becomes problematic, the microcontroller adjusts PWM frequency or duty cycle patterns to move harmonics outside the audible range or reduces PWM switching activity. This allows maintaining fast control response when needed while minimizing audible noise during normal operation.
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 proposed solution effectively reduces noise and improves the accuracy of motor control by compensating for latency in position measurements, allowing for more precise control of motor torque and speed, even with relatively low-cost sensors, thus enhancing the performance of automotive systems like brake by wire and electric power steering.
Implementation Method 1
Motor rotor position can be measured relatively easily using a sensor such as a Hall effect type sensor that detects the relative position of a target magnet fixed to the motor rotor and a sensing head of the Hall effect sensor.
Data Source
AI summary
A method of controlling an electric motor in an apparatus is disclosed. The apparatus comprises a motor having a rotor, a sensor which periodically generates estimates of the angular position of the rotor and an estimate of the velocity of the motor rotor, a microcontroller, and a communication network which connects the microcontroller and the position sensor. The method comprises the steps of periodically sending a request for rotor angular position across the communication network from the microcontroller to the sensor, receiving from the sensor across the communication network a response indicating the rotor angular position and the velocity of the rotor together with an ageing value indicative of the age of the rotor angular position value sent across the communication network, modifying at the microprocessor the received rotor angular position value using the ageing signal and the velocity signal to generate a modified angular position signal that is an estimate of the current rotor position; and generating, by the microcontroller, a set of control signals for the motor using the modified angular position signal.