Motor Control Device for Cycloidal Speed Reducer Angular Error
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Solution Overview
Problem
Existing control techniques for reducing angular transmission errors in speed reducers, such as those used in industrial robots, require multiple encoders and error correction data preparation, which are costly and labor-intensive, and may not adequately address errors under load conditions.
Innovation Solution
A control device that includes an angle acquirer, an estimator to calculate angular errors based on the number of holes in the oscillatory gear portion, and a corrector to determine a compensation current value, which is used to correct the command current and reduce angular transmission errors without the need for additional encoders or extensive data preparation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple encoders are used to reduce angular transmission error, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent extracts only the essential information needed for error correction by using a single encoder on the input side and calculating output position through mathematical relationships, rather than using multiple encoders. This reduces hardware complexity while maintaining measurement precision for angular transmission error correction.
Solution Approach 2:
The patent creates a virtual model of the speed reducer's error characteristics through mathematical modeling and uses this model to predict and correct output position errors, replacing the need for physical output-side encoders with a computational copy of the error behavior.
2Measurement precision
If encoder is arranged on output side of speed reducer, then angular transmission error is reduced, but versatility deteriorates
Solution Approach 1:
Instead of placing the encoder on the output side to directly measure output position, the patent inverts the approach by placing the encoder on the input side and using mathematical relationships to infer output position, thereby achieving the same error correction goal without restricting application versatility.
3Measurement precision
If error correction data is prepared in advance, then angular transmission error is reduced, but labor intensity increases
Solution Approach 1:
The patent enables the system to automatically generate and update error correction data through real-time measurement and calculation, eliminating the need for manual data preparation and management. The system serves itself by continuously learning and correcting its own errors without external intervention.
Solution Approach 2:
The patent performs preliminary error characterization through mathematical modeling during the design phase, creating a foundation for real-time correction that reduces the need for extensive field data collection and preparation.
4Ease of manufacture
If error correction data is prepared without considering load changes, then data preparation is simplified, but angular transmission error reduction becomes insufficient
Solution Approach 1:
The patent transitions from static error correction data to dynamic correction that adapts to changing load conditions. The system continuously updates error compensation based on real-time input-output relationships, enabling accurate correction across varying operational conditions without requiring separate data sets for each load level.
Data Source
AI summary
This application discloses a control device for controlling a motor configured to drive an oscillatory cyclo-speed reducer including an oscillatory gear portion formed with at least one hole at an eccentric position. The control device includes an angle acquirer for acquiring input information about an input rotational angle indicating a rotational angle of the motor, an estimator for estimating an angular error between the input rotational angle and an output rotational angle indicating a rotational angle of the oscillatory cyclo-speed reducer based on a quantity of the hole(s) and a corrector for determining a compensation current value in correspondence to the angular error and setting a magnitude of a current to be supplied to the motor by correcting a command current value using the compensation current value.