Wave Gear Angular Transmission Error Compensation
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Solution Overview
Problem
Wave gear devices experience angular transmission errors due to low gear precision, differences in shaft centers, and non-linear elastic deformation, leading to oscillations and positioning inaccuracies, especially in semi-closed loop control systems where the motor shaft synchronous component is difficult to measure and compensate for.
Innovation Solution
A method is proposed to compensate for the motor shaft synchronous component by determining it using a specific formula, applying it as a twisting effect between the motor and load inertia bodies, and correcting the motor current command to cancel out its effect on the load position, thereby improving positioning precision and inhibiting oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If wave gear device is used as speed reducer, then backlash is eliminated and torque capacity is improved, but angular transmission errors occur due to low gear precision and non-linear elastic deformation
Solution Approach 1:
The patent applies parameter changes by modeling the angular transmission error as a function of motor shaft position and using this model to dynamically adjust the position command. The error characteristics (amplitude and phase) are determined through measurement and then used to compensate for positioning inaccuracies, transforming the system from static to dynamic error compensation.
2Measurement precision
If semi-closed loop control is used to control load position based on motor position, then high resolution control is achieved, but angular transmission errors cannot be fully compensated due to unmeasurable motor shaft synchronous component
Solution Approach 1:
The patent implements feedback by measuring the actual load position using a load shaft encoder and comparing it with the theoretical position calculated from motor position. The difference (angular transmission error) is fed back to the compensation calculation, enabling continuous correction of positioning errors during operation.
Solution Approach 2:
The patent replaces direct mechanical measurement of the motor shaft synchronous component with an equivalent approach: measuring the load position error and using mathematical modeling to derive the motor shaft synchronous component effects. This substitution avoids the complexity of directly measuring internal wave gear deformations.
3Manufacturing precision
If motor shaft synchronous component compensation is applied, then positioning precision is improved, but device complexity increases due to additional modeling and calculation requirements
Solution Approach 1:
The patent applies preliminary action by pre-determining the error characteristics (amplitude and phase) through initial measurement and calibration. These pre-determined parameters are then stored and used during operation to calculate compensation amounts, avoiding the need for real-time complex measurements and reducing computational burden during actual positioning operations.
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 method effectively reduces positioning errors and oscillations caused by the dynamic motor shaft synchronous component, enhancing the precision of the output shaft positioning and reducing the impact of angular transmission errors in wave gear devices.
Implementation Method 1
a flexspline (below, 'F/S') that is a flexible, externally toothed gear that deforms elastically
Data Source
AI summary
A positioning system (1) provided with an actuator (2) having a wave gear device (4) is driven and controlled by a semi-closed loop control for controlling the load position of a load device (5) based on the motor position of a motor shaft (31) of a motor (3). In a method for compensating for an angular transmission error by compensating for a motor shaft synchronous component θSync that occurs in synchrony with the motor position and is a relative rotation-synchronous component that includes an angular transmission error component of the wave gear device (4), the positioning system (1) is represented as a two-inertia model, and the motor shaft synchronous component θSync is represented as an oscillation source for producing a twisting action between the two inertia bodies in the two-inertia model. A motor current command iref is corrected by a compensation current command icomp calculated so as to allow the effect of the motor shaft synchronous component θSync on the load position to be compensated in this case, and a motor position command r is corrected by a motor position correction signal θcomp calculated in order to compensate for the effect of the motor shaft synchronous component θSync.