Electric Motor Controller Simultaneous Inertia Friction Spring Estimation
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Solution Overview
Problem
Existing electric motor controllers cannot accurately estimate inertia, nonlinear friction, and spring characteristics of driven bodies in machine tools and industrial machinery, limiting their ability to optimize machining conditions and control responsiveness.
Innovation Solution
An electric motor controller that simultaneously estimates inertia, nonlinear friction, and spring constants in real-time by using a coupling shaft with resonance characteristics, incorporating a command unit, current acquiring unit, velocity acquiring unit, and correcting unit to calculate and correct estimated values based on velocity and torque data, with an accommodation coefficient to minimize torque errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a rigid body model is used for estimation, then the estimation process is simple, but the estimation accuracy deteriorates when the controlled object is not a rigid body
Solution Approach 1:
The patent changes the model parameters from a simple rigid body model to a resonance model that includes spring characteristics. The controlled object is modeled as having resonance characteristics with natural frequency and damping ratio, allowing accurate representation of flexible bodies while maintaining tractable estimation through iterative least squares methodology.
2Device complexity
If only linear friction is estimated, then the estimation algorithm is simple, but nonlinear friction characteristics are not captured
Solution Approach 1:
The patent changes the friction model from purely linear to a combined linear and nonlinear friction model. By introducing Coulomb friction coefficient as an additional parameter alongside viscous friction coefficient, the model accurately represents nonlinear friction characteristics while the iterative least squares algorithm efficiently handles the increased complexity of estimating multiple parameters simultaneously.
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
Enables precise real-time estimation of inertia, friction, and spring constants, enhancing the accuracy of drive control and robustness of servo systems, even in non-rigid bodies, by correcting estimated values to minimize torque errors.
Implementation Method 1
a coupling shaft having resonance characteristics including a spring
Implementation Method 2
a coupling shaft having resonance characteristics including a spring
Implementation Method 3
an electric motor, which is a controlled object, drives a driven body
Data Source
AI summary
A sinusoidal command is added to a torque command of a controller to acquire a velocity and a current value of an electric motor. An estimated coupling torque value is calculated by calculating an input torque value from the current value and a torque constant of the electric motor and further calculating a coupling torque value from a velocity difference, motor inertia, and the input torque. An estimated torque error is then calculated from the estimated coupling torque value and the coupling torque value, and inertia, friction, and a spring constant are estimated from the estimated torque error, the velocity, and the coupling torque value.