Harmonic Drive Servomotor Feedback for Backlash Accuracy
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Solution Overview
Problem
Existing servomotor speed reduction gear sets face efficiency and size challenges due to high backlash and low precision, with conventional harmonic drives having uncontrollable backlash errors and angular transmission inaccuracies.
Innovation Solution
A servomotor design incorporating a harmonic drive with a flex spline and circular spline mechanism, coupled with a sensor for precise angular displacement detection, which allows for real-time correction of motor output errors and transmission inaccuracies, enhancing angular transmission accuracy and reducing size and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional harmonic drives are used for speed reduction, then transmission ratio and compactness are improved, but backlash error becomes uncontrollable and angular transmission accuracy deteriorates
Solution Approach 1:
The patent employs a sensor to detect the actual output angle of the harmonic drive and feeds this information back to the control circuit. The control circuit calculates the deviation between the theoretical output angle and actual output angle, then generates correction signals to compensate for backlash errors and transmission inaccuracies, thereby maintaining high angular transmission accuracy while using compact harmonic drives.
Solution Approach 2:
The patent replaces mechanical error compensation methods (such as high-precision mechanical components) with an electronic control system consisting of sensors and control circuits. This substitution allows for dynamic compensation of backlash and transmission errors through software algorithms, achieving high precision without requiring expensive high-precision harmonic drives.
2Power
If multi-stage speed reduction is implemented to achieve high reduction ratio, then transmission ratio is improved, but total efficiency deteriorates due to cumulative gear losses
Solution Approach 1:
The patent extracts the speed reduction function from multi-stage mechanical gear systems and implements it through a single-stage harmonic drive. This eliminates the need for multiple gear stages and their associated losses, achieving high reduction ratios (up to 1/300) in a single stage with higher efficiency.
Solution Approach 2:
The patent changes the fundamental parameter of speed reduction from mechanical gear multiplication to harmonic wave-based single-stage reduction. By utilizing the elastic deformation and wave propagation characteristics of the harmonic drive, the system achieves high reduction ratios without the cumulative efficiency losses of multi-stage mechanical gearing.
3Ease of operation
If gear gaps are introduced for smooth transmission, then transmission smoothness is improved, but backlash increases and precision deteriorates
Solution Approach 1:
The patent replaces mechanical gap-based smooth transmission with electronic control-based smooth transmission. The sensor and control circuit dynamically adjust motor output to compensate for any transmission irregularities, eliminating the need for physical gear gaps while maintaining both smooth operation and high precision.
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 solution achieves high efficiency and precision with reduced size and weight, maintaining angular transmission accuracy and reducing backlash errors, while being cost-effective compared to high-precision harmonic drives.
Implementation Method 1
The harmonic gear transmissions are a type of planetary gear transmission that transmits power and motion through the mechanical wave generated by flexible components
Data Source
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AI summary
A servomotor includes a control circuit 1, an electric motor 2, a harmonic drive 3 and a sensor. The control circuit is connected to the electric motor and used to control the electric motor. The harmonic drive includes an outer casing 5, a wave generator 32, a flex spline 34 and a circular spline 33. The wave generator is driven by the electric motor. The flex spline is sleeved on an exterior of the wave generator and located within the circular spline and engages with the circular spline. The flex spline is connected with an output member 37 that is used to output power, and a post 6 is arranged along a rotation axis of the output member. The sensor is arranged within the outer casing and used to detect an angular displacement of the post. A method for controlling the servomotor is also provided.