Inertia Estimation for Restricted Motor Travel
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Solution Overview
Problem
Traditional methods for estimating motor system inertia fail when motor rotations and load movement are restricted, preventing the motor from reaching a high test velocity, leading to potential damage and requiring manual measurement for inertia calculation.
Innovation Solution
A method that accelerates the motor to an intermediate position along the load travel range and decelerates to zero velocity, sampling torque during both phases to calculate inertia using the sum of average torque magnitudes divided by the sum of acceleration and deceleration rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional acceleration/deceleration inertia estimating technique is used, then inertia estimation accuracy is improved, but motor rotation limitations cause inability to reach test velocity
Solution Approach 1:
The patent changes the velocity parameters from traditional high test velocity to intermediate velocities that are achievable within rotation limits. The system accelerates to an intermediate velocity and decelerates to zero within the restricted rotation range, allowing inertia estimation without requiring high speeds that exceed motor rotation capabilities.
Solution Approach 2:
Instead of performing a complete acceleration to high test velocity and deceleration cycle, the patent uses a partial action approach by accelerating only to an intermediate velocity and decelerating to zero within the restricted rotation range. This partial cycle is sufficient to obtain accurate inertia measurements without exceeding rotation limits.
2Measurement precision
If motor is accelerated to high test velocity, then inertia measurement capability is improved, but motor or load damage risk increases due to restricted movement
Solution Approach 1:
The patent applies beforehand cushioning by pre-planning the acceleration and deceleration profiles to operate within safe rotation limits. The system identifies intermediate velocities and positions that ensure the motor and load remain within their safe operating ranges throughout the inertia measurement process, preventing damage before it can occur.
Solution Approach 2:
The patent changes the velocity parameter from high test velocity to intermediate velocity that is safe for the restricted motor-load system. This parameter change allows inertia measurement to proceed without subjecting the motor or load to harmful high-speed conditions that could cause damage.
3Reliability
If manual measurement is used instead of automated acceleration/deceleration technique, then motor rotation limitations are avoided, but commissioning complexity increases
Solution Approach 1:
The patent implements self-service by enabling the motor drive system to automatically perform inertia estimation using its own controllers and sensors. The system autonomously executes the acceleration to intermediate velocity and deceleration to zero, calculates inertia from the measured data, and programs the value without requiring external manual measurement or intervention, thereby reducing commissioning complexity.
Solution Approach 2:
The patent applies universality by making the motor drive controller perform multiple functions: it controls the acceleration and deceleration profiles, measures the velocity and torque, calculates the inertia value, and programs the result back into the system. This multi-functionality eliminates the need for separate manual measurement devices and procedures.
Data Source
AI summary
A method and apparatus for estimating inertia wherein a load has a limited range of load travel, the method comprising the steps of identifying an intermediate position along the range of load travel that is separated from a first end of the range of load travel, with the load separated from a first end of the range of load travel, increasing a velocity of the electric motor from a first velocity, identifying when the load has reached the intermediate position, identifying the motor velocity at the intermediate position as a second velocity, detecting a first rate of velocity change from the first velocity to the second velocity and deriving an inertia value as a function of the first rate of velocity change.