Motor Selection Apparatus Eccentric Load Torque Calculation
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Solution Overview
Problem
Existing motor selection apparatuses fail to accurately account for eccentric load torque, leading to improper motor selection due to overestimation of required torque when eccentric load torque is assumed constant.
Innovation Solution
A motor selection apparatus that includes units to calculate eccentric load torque, acceleration/deceleration torque, and required torque, determining if the motor can handle the required torque based on instantaneous torque, considering the phase-dependent eccentric load torque and friction torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If eccentric load torque is assumed constant, then calculation is simplified, but motor selection accuracy deteriorates
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a static assumption of constant eccentric load torque to a dynamic calculation that varies the torque according to the rotational phase angle. The eccentric load torque is calculated as Te(θ) = m·g·e·sin(θ), where θ changes with rotation, making the torque calculation dynamic and phase-dependent rather than static and constant.
Solution Approach 2:
The patent applies parameter changes by introducing the rotational phase angle θ as a varying parameter that changes the eccentric load torque value. Instead of using a fixed torque value, the system calculates torque at different phase angles (0°, 90°, 180°, 270°) and uses these varying parameters to determine the maximum required torque for motor selection.
2Measurement precision
If phase-dependent eccentric load torque is calculated, then motor selection accuracy is improved, but calculation complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the rotational cycle into discrete phase angles (0°, 90°, 180°, 270°) and calculating the eccentric load torque at each segment. This segmented approach allows the system to capture the varying torque characteristics without requiring continuous complex integration, simplifying the calculation while maintaining accuracy.
Solution Approach 2:
The patent applies partial action by calculating torque at key phase angles rather than continuously throughout the entire rotation. This partial sampling at critical points (where torque reaches maximum values) is sufficient to determine the peak torque requirements for motor selection, avoiding the need for exhaustive continuous calculation.
3Reliability
If maximum torque is used for motor selection, then safety margin is improved, but motor size and cost increase
Solution Approach 1:
The patent applies parameter changes by using the calculated maximum eccentric load torque (derived from phase-dependent calculations) as the basis for motor selection rather than using arbitrary safety margins or overly conservative estimates. This allows selecting a motor with appropriate size that matches the actual maximum torque requirements, avoiding both undersizing and excessive oversizing.
Data Source
AI summary
A motor selection apparatus includes: a mechanical condition obtainment unit that obtains information pertaining to a distance between a center of mass of a workpiece and a rotation center of a motor; an operating pattern obtainment unit that obtains information pertaining to an operating pattern; a motor information obtainment unit that obtains information pertaining to instantaneous torque; an eccentric load torque calculation unit that calculates eccentric load torque, which is load torque acting on the motor in accordance with the rotation phase of the motor; an acceleration/deceleration torque calculation unit that calculates acceleration/deceleration torque; a required torque calculation unit that calculates a required torque from a sum of the eccentric load torque and the acceleration/deceleration torque; and a motor selection unit that determines whether a motor can be selected, based on whether the required torque is less than or equal to the instantaneous torque of the motor.