Tandem Motor Controller Dynamics for Position Error Reduction
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Solution Overview
Problem
In tandem motor control systems, increased position errors occur when one motor is predominantly driven, leading to adverse effects on control stability and accuracy due to differences in speed detection timing and motor overheating.
Innovation Solution
A motor controller that includes position and speed control units, integrators for error calculation, and an integrated value selector to adjust torque command values based on motor acceleration status, minimizing position errors by selecting appropriate integrated values and generating preload torque values to counteract forces between motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If tandem control is used to drive large driven objects, then the driven object can be accelerated and decelerated effectively, but position errors increase when one motor is mainly driven
Solution Approach 1:
The patent dynamically switches between using the first integrated value (when first motor acceleration ≥ 0) and the second integrated value (when first motor acceleration < 0) based on the real-time acceleration state of the first motor. This dynamic adaptation ensures that the appropriate integrated value is used during different phases of motor operation, resolving the position error issue while maintaining acceleration capability
Solution Approach 2:
The patent changes the parameter used for torque command generation based on motor acceleration state. By switching between different integrated values (parameters) according to the acceleration condition, the system optimizes control accuracy during both acceleration and deceleration phases without sacrificing the ability to drive large driven objects
2Stability of the object's composition
If integrated value of speed error is used to generate torque command values, then control stability is improved, but position error increases when sub motor is mainly driven
Solution Approach 1:
The system dynamically selects which integrated value to use based on the acceleration state of the first motor. When acceleration is non-negative, the first integrated value is used; when acceleration is negative, the second integrated value is used. This dynamic selection maintains control stability while preventing position error accumulation during sub-motor-dominated operation
Solution Approach 2:
The patent uses feedback from the motor acceleration state to determine which integrated value should be applied. By continuously monitoring the acceleration condition and adjusting the selected integrated value accordingly, the system maintains both stability and positioning accuracy under varying operational conditions
Data Source
AI summary
In a motor controller according to the present invention, a speed control unit 24m includes an integrator calculating an integrated value Sm of a speed error ωm-ωm′ between a speed command value ωm and a rotation speed ωm′ and generates a torque command value Tm based on ωm-ωm′, a predetermined value, a proportional gain and an integration gain. A speed control unit 24s includes an integrator calculating an integrated value Ss of a speed error ωs-ωs′ between a speed command value ωs and a rotation speed ωs′ and generates a torque command value Ts based on ωs-ωs′, the predetermined value, a proportional gain and an integration gain. An integrated value selecting unit 28 selects any one of Sm and Ss as the predetermined value, depending on a drive status of a main motor 6m and a sub motor 6s.