Servo Control Angular Transmission Error Compensation
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Solution Overview
Problem
Existing servo control methods for wave gear devices struggle to effectively compensate for angular transmission errors without increasing the device's scale or complexity, leading to limited vibration suppression and positioning accuracy in robot arms.
Innovation Solution
A servo control device with a position control system, an inverse control element, and a compensation amount generation unit that applies a compensation amount to the position control system to accurately compensate for angular transmission errors, using a semi-closed loop control configuration and discrete time system with added delay elements for digital control and forward compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a two-inertia system model with an observer is used for compensation, then angular transmission error compensation is achieved, but the controller becomes highly complicated
Solution Approach 1:
The patent extracts only the essential first-order frequency component of the angular transmission error using a simple sinusoidal model, rather than attempting to compensate for all error components through complex observers. This selective extraction achieves effective vibration suppression while maintaining controller simplicity.
Solution Approach 2:
The patent changes the approach from complex system modeling to simple parameter-based compensation. By identifying the dominant first-order frequency component and using a sinusoidal model with adjustable parameters (amplitude and phase), the system achieves effective compensation without the complexity of two-inertia system models.
2Object-affected harmful factors
If a notch filter with variable cycle is used to suppress vibration, then the effect of angular transmission error is reduced, but the device becomes too complicated
Solution Approach 1:
The patent replaces the mechanical approach of using a variable-cycle notch filter with a control-theory-based sinusoidal compensation method. This substitution achieves the same vibration suppression effect through software-based phase and amplitude adjustment rather than complex frequency filtering hardware.
Solution Approach 2:
Instead of filtering out the error components (notch filter approach), the patent inverts the approach by directly generating a compensation signal that counteracts the angular transmission error. This inverse approach simplifies the system by avoiding the need for complex frequency analysis and filtering.
3Measurement precision
If correction tables are used for position feedback compensation, then positioning accuracy is improved, but the influence of system dynamics is not fully addressed
Solution Approach 1:
The patent incorporates dynamic characteristics by modeling the angular transmission error as a sinusoidal function with specific frequency and phase parameters that vary with operating conditions. This dynamic modeling approach allows the compensation to adapt to changing system dynamics rather than relying on static correction tables.
Solution Approach 2:
The patent implements a feedback mechanism where the actual angular transmission error is measured and used to adjust the compensation parameters in real-time. This closed-loop feedback ensures that the compensation remains effective under varying dynamic conditions, addressing the limitation of open-loop correction table methods.
Data Source
AI summary
A servo control device for controlling a motor based on a position command when an operation target is connected to the motor via a wave gear reduction mechanism may include a position control system configured to detect a shaft angular position of the motor to perform a closed-loop control based on the shaft angular position; an inverse control element having an inverse characteristic of dynamics of the position control system; and a compensation amount generation unit configured to generate a compensation amount for compensating for an angular transmission error of the wave gear reduction mechanism. The inverse control element is configured to apply compensation amount to the position control system.