Motor Rotor Position Control With Adaptive Torque Mapping
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Solution Overview
Problem
Conventional techniques for controlling the position of a rotor in motors, especially when subjected to external forces like gravity, result in oscillations due to motor inertia, making it difficult to maintain the rotor at or near the zero reference position.
Innovation Solution
A novel angle-to-torque function is implemented in a motor controller, which produces an error value indicating the difference between the current and reference rotor positions. Based on this error, the controller selects an appropriate angle-to-torque converter function to derive a torque value that reduces the positional difference, thereby minimizing oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional angle-to-torque control function is applied to counteract external forces on the rotor, then the rotor position can be maintained against gravity, but oscillations occur due to motor inertia
Solution Approach 1:
The control system dynamically selects from multiple angle-to-torque converter functions based on the current error magnitude. When error is large, a stiffer spring constant provides strong restoring force; when error is small, a softer spring constant prevents oscillations. This dynamic adaptation resolves the contradiction between maintaining position against external forces and preventing oscillations.
Solution Approach 2:
The system changes the parameter (spring constant) of the angle-to-torque converter function based on operating conditions. By selecting different functions with different spring constants according to error magnitude, the system optimizes both position maintenance and oscillation suppression, resolving the technical contradiction.
2Reliability
If a stiff spring constant is used in the angle-to-torque function to strongly counteract external forces, then rotor position maintenance improves, but oscillations increase due to motor inertia
Solution Approach 1:
The system transitions from a static spring constant to a dynamic selection mechanism that adapts the spring constant based on error magnitude. This resolves the contradiction by applying stiff control only when necessary (large errors) and soft control when approaching the target (small errors), eliminating oscillations while maintaining position accuracy.
Solution Approach 2:
The control function is segmented into multiple discrete angle-to-torque converter functions, each with different spring constants. This segmentation allows the system to choose the appropriate level of stiffness for each operating condition, preventing the oscillations that would result from uniformly stiff control.
3Measurement precision
If multiple angle-to-torque converter functions are implemented to reduce oscillations, then rotor position accuracy improves, but device complexity increases
Solution Approach 1:
The control system is segmented into multiple discrete angle-to-torque converter functions that can be selectively applied. This segmentation achieves high position accuracy through adaptive control while keeping each individual function simple, resolving the contradiction between precision and complexity.
Solution Approach 2:
The system uses feedback from the error magnitude to select the appropriate converter function. This feedback mechanism enables accurate rotor position control through adaptive function selection while maintaining relatively simple control logic, resolving the contradiction between measurement precision and device complexity.
Data Source
AI summary
An apparatus includes a controller that controls a motor including multiple motor windings. During operation, the motor controller receives an error value indicating a difference between a current angular position of a rotor in the motor with respect to a reference angular position of the rotor. Based on the error value, the controller selects a first angle-to-torque converter function amongst multiple angle-to-torque converter functions in a piecewise angle-to-torque converter function. Via the first angle-to-torque converter function, the controller derives a torque value indicating a magnitude of torque to apply to the rotor. The controller applies the torque as indicated by the torque value to the rotor.