Servo Ball Screw Position Estimation Without Linear Scales
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Solution Overview
Problem
Existing movement systems for factory production lines are costly due to the use of large linear scales and multiple sensors for accurate position detection of movable objects, which increases the overall cost and complexity.
Innovation Solution
A movement system that includes drive means, detection means, and a controller to estimate the position of a movable object using reference state information and state detection, eliminating the need for extensive linear scales and sensors by synchronizing an encoder and a sensor to accurately determine the position based on the rotation amount of the servomotor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear scale is placed along the overall movement path of the machine to detect position accurately, then position detection accuracy is improved, but system cost and device complexity increase
Solution Approach 1:
The patent extracts the position detection function from the complex linear scale system and implements it using a simple sensor combined with drive means state detection. Instead of using an extensive linear scale along the entire movement path, the system uses a single sensor at a reference position combined with encoder feedback from the drive means to calculate position, thereby achieving accurate position detection with minimal hardware complexity
Solution Approach 2:
The patent introduces the drive means state information as an intermediary to bridge the gap between the simple sensor detection and accurate position measurement. By detecting the state (position, speed, acceleration) of the drive means and combining it with the sensor signal at the reference position, the system can accurately determine the moving object's position without requiring complex detection hardware along the entire path
2Measurement precision
If multiple sensors are distributed uniformly along the movement path to achieve accurate position detection, then position detection accuracy is improved, but system cost increases
Solution Approach 1:
The patent segments the position detection function into two parts: (1) a single sensor detecting presence at a reference position, and (2) drive means state detection providing motion information. This segmentation allows the system to achieve continuous position monitoring without distributing multiple sensors along the movement path, thereby reducing the number of sensors from many to just one
Solution Approach 2:
The patent implements feedback by continuously monitoring the drive means state (through encoders or other state detectors) and using this information to update position calculations in real-time. The controller receives feedback from both the sensor at the reference position and the drive means state detection, combining these signals to accurately track position throughout the movement path without requiring multiple sensors
3Measurement precision
If a linear scale is used for position detection, then position detection accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces the expensive linear scale with a combination of inexpensive components: a simple sensor and standard drive means with state detection capability. These components are much cheaper than a linear scale system, and while they may have shorter lifetimes individually, their low cost and ease of replacement make the overall system more economical and easier to manufacture
Data Source
AI summary
A servomotor (20) is driven to move a machine (10) with a ball screw (30). A first sensor (50) detects presence of the machine (10) at a first reference position (P) being predefined. A controller (60) stores a state of the servomotor (20) detected by an encoder (40) as reference state information upon detection of the machine (10) by the first sensor (50). The controller (60) estimates a position of the machine (10) based on the state of the servomotor (20) detected by the encoder (40) and the reference state information.