Servo Controller Ball Screw Expansion Compensation
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Solution Overview
Problem
Existing servo controllers for ball screw systems face challenges in maintaining high positional accuracy due to expansion/contraction of the ball screw, which varies with distance from the servomotor, leading to reduced precision when the moving direction of the movable body is reversed.
Innovation Solution
A servo controller that calculates position compensation based on the distance from the servomotor to the movable body and the torque command value, using a position command generating part, position detecting part, velocity command generating part, torque command generating part, and position compensation calculating part to account for the expansion/contraction of the ball screw, ensuring accurate positioning regardless of the movable body's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position compensation is calculated using a reference position near the servomotor, then control accuracy is high near the reference position, but control accuracy decreases at positions away from the servomotor
Solution Approach 1:
The patent applies local quality by making the position compensation calculation adapt to different locations along the ball screw. Instead of using a single reference position compensation value, the system calculates compensation specific to each position of the movable body, ensuring high accuracy locally at every position rather than only near a reference point.
Solution Approach 2:
The patent implements dynamics by making the position compensation value dynamic and position-dependent. The compensation value changes continuously based on the real-time position of the movable body along the ball screw, allowing the system to adapt to varying expansion/contraction characteristics at different locations rather than using a static reference-based compensation.
2Measurement precision
If position compensation is calculated using a reference position away from the servomotor, then control accuracy is high away from the servomotor, but control accuracy decreases near the servomotor
Solution Approach 1:
The patent applies local quality by making the position compensation calculation adapt to different locations along the ball screw. Instead of using a single reference position compensation value, the system calculates compensation specific to each position of the movable body, ensuring high accuracy locally at every position rather than only near a reference point.
Solution Approach 2:
The patent implements dynamics by making the position compensation value dynamic and position-dependent. The compensation value changes continuously based on the real-time position of the movable body along the ball screw, allowing the system to adapt to varying expansion/contraction characteristics at different locations rather than using a static reference-based compensation.
3Ease of manufacture
If torque is multiplied by a constant value for position correction, then the correction process is simple, but the correction does not account for the position of the movable body on the ball screw
Solution Approach 1:
The patent transforms the static constant multiplication approach into a dynamic position-dependent calculation. The position compensation calculating part uses the current position of the movable body to determine the appropriate compensation value, making the correction adaptive to the specific location on the ball screw while maintaining computational efficiency.
Solution Approach 2:
The patent applies parameter changes by making the compensation factor variable based on position rather than a fixed constant. The system adjusts the compensation parameter according to the movable body's position along the ball screw, accounting for varying expansion/contraction characteristics at different locations without overly complicating the correction process.
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 solution enables high-accuracy motion control of the movable body by accurately calculating and compensating for the expansion/contraction of the ball screw, improving positional accuracy even when the movable body is positioned away from the servomotor, thereby reducing errors and maintaining precision across different operational positions.
Implementation Method 1
The ball screw expands or contracts in the axial direction thereof by reactive force from a movable body, such as a nut, which is threadably engaged with the ball screw
Data Source
AI summary
A servo controller, capable of controlling the motion of a movable body with high accuracy, without depending on the position of the movable body which is moved on a ball screw. The servo controller has a position command generating part which generates a position command value; a velocity command generating part which generates a velocity command value based on the position command value and a position detection value; a torque command generating part which generates a torque command value based on the velocity command value and a velocity detection value; and a position compensation calculating part which calculates an amount of expansion/contraction of the ball screw based on a distance from the servomotor to a nut threadably engaged with the ball screw and the torque command value, and calculates a position compensation based on the amount of expansion/contraction.