Lubricant Life Estimation in Robot Transmissions Using Heat Modeling
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Solution Overview
Problem
Existing life evaluating devices for lubricants in machines with motors and transmission mechanisms fail to accurately estimate the life of lubricants due to incomplete consideration of motor heat values and frictional heat values, leading to inaccurate temperature and life assessments.
Innovation Solution
A life evaluating device that calculates motor heat values based on motor current and speed, frictional heat values based on rotating speed and friction coefficients, and estimates lubricant temperature by combining these values, along with air cooling heat dissipation, to accurately evaluate lubricant life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If motor heat value and frictional heat value are not fully considered, then the evaluation device is simpler, but the temperature estimation accuracy deteriorates
Solution Approach 1:
The heat generation sources are segmented into distinct components: motor heat value (calculated from motor current and speed) and frictional heat value (calculated from rotating speed and friction coefficients). This segmentation allows each heat source to be calculated and considered separately, improving temperature estimation accuracy without creating an overly complex integrated system.
Solution Approach 2:
The evaluation device uses readily available operational parameters (motor current, rotating speed, friction coefficients) to calculate heat values, rather than requiring additional sensors or complex measurements. This self-service approach obtains necessary data from existing system operations, improving accuracy without proportionally increasing device complexity.
2Measurement precision
If only frictional heat value is considered, then the calculation is simpler, but the life evaluation accuracy deteriorates
Solution Approach 1:
The total heat generation is segmented into motor heat value and frictional heat value components. By calculating both segments and combining them for temperature estimation, the system achieves more accurate life evaluation than considering friction alone, while keeping each segment's calculation relatively simple.
Solution Approach 2:
The motor heat value and frictional heat value are merged into a combined temperature estimation model. This combination integrates multiple heat generation sources to provide a more comprehensive and accurate basis for lubricant life evaluation, outweighing the increased calculation complexity.
3Measurement precision
If comprehensive heat values are calculated, then temperature estimation accuracy improves, but processing time increases
Solution Approach 1:
The system uses operational parameters (motor current, rotating speed) that are already being measured and processed for robot control. By leveraging these existing data streams to calculate heat values, the system improves temperature estimation accuracy without adding significant processing time, as the data is already available from normal operation.
Solution Approach 2:
The calculation uses direct relationships between operational parameters and heat generation (current² for motor heat, speed×friction for frictional heat). These parameter changes follow straightforward mathematical relationships that can be computed rapidly, maintaining low processing time while achieving comprehensive heat value calculation.
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
This approach allows for precise estimation of lubricant temperature and life, enabling timely replacement and reducing maintenance costs by accounting for motor heat generation and frictional losses.
Implementation Method 1
a motor heat value calculating unit (14) that calculates a motor heat value on the basis of a current value of the at least one motor
Implementation Method 2
a frictional heat value calculating unit (15) that calculates a frictional heat value in the transmission mechanism on the basis of rotating speed of the at least one motor and a coefficient of friction of the transmission mechanism
Data Source
AI summary
Provided is a life evaluating device that evaluates the life of a lubricant in a machine including a motor and a transmission mechanism that is lubricated by the lubricant and transmits power of the motor to a movable unit. The life evaluating device includes a motor-heat-value calculating unit that calculates a motor heat value on the basis of a current value of the motor, a frictional-heat-value calculating unit that calculates a frictional heat value in the transmission mechanism on the basis of rotating speed of the motor and a coefficient of friction of the transmission mechanism, a lubricant-temperature estimating unit that estimates temperature of the lubricant on the basis of the calculated frictional heat value and the calculated motor heat value, and a life estimating unit that estimates the life of the lubricant on the basis of the estimated temperature of the lubricant.