Robotic Arm Joint Control for Gear Torque Ripple Compensation
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Solution Overview
Problem
Robot arm joints with gears experience torque ripples due to transmission design, leading to unsmooth running and increased wear, which existing methods struggle to fully compensate for without costly precision manufacturing or continuous sensor-based compensation.
Innovation Solution
A method that automatically controls robot arm joints by detecting motor positions, speeds, and accelerations, calculating model-based joint torques, and adapting target values using an optimization method to minimize torque ripples, effectively compensating for periodic fluctuations without additional sensors or extensive commissioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional gear transmissions are used in robot arm joints, then mechanical advantage and speed reduction are achieved, but torque ripples occur causing unsmooth running and increased wear
Solution Approach 1:
The control system performs preliminary identification of torque ripple characteristics during a commissioning phase, storing the identified parameters for subsequent compensation. This preliminary characterization enables the system to predict and counteract torque ripples before they affect operation quality.
Solution Approach 2:
The system uses measured torque ripple data to continuously adjust and optimize compensation parameters. By monitoring actual torque fluctuations and comparing them with model predictions, the control system refines its compensation strategy to minimize torque ripples while maintaining efficient power transmission.
2Object-generated harmful factors
If precision manufacturing is used to reduce torque ripples, then transmission smoothness improves, but manufacturing costs increase significantly
Solution Approach 1:
The patent replaces mechanical precision manufacturing solutions with a control-based compensation system. Instead of manufacturing gears with ultra-precise tolerances to eliminate torque ripples, the system uses software algorithms to identify and compensate for ripple effects, achieving smooth transmission at standard manufacturing quality levels.
Solution Approach 2:
The system changes operational parameters dynamically by adjusting motor command values based on identified torque ripple characteristics. This allows the system to compensate for transmission imperfections through parameter optimization rather than requiring perfect mechanical parameters from manufacturing.
3Object-generated harmful factors
If sensor-based compensation methods are used to reduce torque ripples, then running quality improves, but system complexity and commissioning effort increase
Solution Approach 1:
The system performs self-identification of torque ripple characteristics during an automated commissioning process. The robot arm executes predefined movement patterns while the control system measures and identifies ripple parameters without requiring external sensors or manual intervention, enabling the system to self-characterize its transmission imperfections.
Solution Approach 2:
The system creates a digital model or copy of the torque ripple characteristics through identification measurements. This virtual representation of the transmission imperfections is stored and used for compensation, replacing the need for physical modifications or additional sensing hardware.
4Manufacturing precision
If torque ripple compensation is implemented, then path accuracy and dynamics improve, but control algorithm complexity increases
Solution Approach 1:
The control algorithm uses pre-identified torque ripple parameters to calculate compensation values before executing movement commands. By performing the identification phase separately during commissioning, the runtime control algorithm only needs to apply pre-computed compensation based on current operating conditions, reducing its real-time complexity.
Solution Approach 2:
The compensation algorithm exploits the periodic nature of torque ripples in gear transmissions. By characterizing the ripple as a periodic function with specific frequency components, the control system can use efficient periodic compensation strategies rather than requiring complex continuous optimization during operation.
Data Source
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AI summary
The invention relates to a method for automatically controlling the movement of at least one joint (L1-L6) of a robotic arm (9), wherein the robotic arm (9) has multiple elements (G1-G7), which can be adjusted relative to one another by the movements of the joints (L1-L6) of the robotic arm (9), and the at least one joint (L1-L6) comprises a transmission which is designed to adjust the at least one joint (L1-L6), namely by automatically controlling an electric motor (M1-M6) of the robotic arm (9) connected to the transmission. The invention also relates to a an associated robot (8) and an associated computer program product.