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Inertial Measurement Unit and Diagnostic System

Patent Number: 11,085,793


An inertial measurement unit determines performance degradation of a linear axis and includes: an accelerometer that, when disposed on a motion member of the linear axis including the motion member and a base member: measures acceleration of the motion member; and provides a displacement of the motion member in response to movement of the motion member; and a rate gyroscope that: measures an angular rate of movement of the motion member; and provides a yield angle for the motion member in response to movement of the motion member, wherein the displacement and yield angle determine performance degradation of the linear axis based on an error in linear movement of the motion member along the base member.

Patent Description

As a machine tool is utilized for parts production, emerging faults lead to performance degradation, which lowers control precision and accuracy. Eventually, linear axes of computerized, numerical control machines may undergo significant wear that results in a failure and/or a loss of production quality. Occurrences of faults and failures are becoming more common as higher levels of automation and productivity within manufacturing result in greater wear on machine components. Machine tool faults account for yearly economic losses of tens of billions of US dollars.

Machine tools must be maintained and available for cost-effective production. However, accurately detecting degradation of linear axes is currently a manual, time consuming, and cost­ prohibitive process, hindering widespread commercial adoption. Thus, manufacturers typically do not know the condition of the linear axes of their machine tools, and instead react to problems as they occur. Hence, manufacturers need automated and efficient methods for periodic (e.g., daily or weekly) diagnoses of the condition of machine tool linear axes with minimal disruptions to production. This problem may be posed as a question: "How can you periodically measure linear axis health in about five minutes?"

The invention solves this problem. The invention is a method for sensor data fusion for condition monitoring of linear axes. The method fuses data collected from an inertial measurement unit (IMU) and is mounted to the linear axis to estimate the linear axes errors due to degradation. Data is collected by the IMU (see below) during motion of the linear axis at three different speeds. Data collection for a linear axis may take as little as five minutes. If a sensor box moves with a linear axis, then its degradation can be determined and used for diagnostics and prognostics to help optimize maintenance.

Graphic for how an inertial measurement unit works


This invention is unique in how sensor data is collected at various speeds, processed, and fused to estimate the linear axis errors. It is significantly cheaper than technologies being used in current practices (e.g., 15 minutes versus 8 hours). This method could help reduce yearly costs of machine tools and losses due to machine faults and failures. Additionally, this would allow for periodic (e.g., weekly) diagnoses without significant disruptions to production.

Created May 31, 2022, Updated April 11, 2024