Stepper Motor Actuator Play Compensation Using Back-EMF
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Solution Overview
Problem
Hydraulic drive systems face challenges in maintaining accurate positioning and repeatability due to mechanical play, temperature effects, and component wear, which increases manufacturing costs and complexity, and existing measurement methods are often complex and unreliable.
Innovation Solution
A method involving limited phase currents to detect mechanical play positions in stepper motors, allowing for compensation and initialization of position sensors using back EMF voltage measurements, enabling accurate positioning and reduced mechanical tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tight manufacturing and assembly tolerances are used to minimize mechanical play, then positioning accuracy is improved, but manufacturing costs increase
Solution Approach 1:
The patent changes the parameter of mechanical play from a fixed physical constraint to a variable that can be dynamically measured and compensated. By using a sensor to detect the actual mechanical play and software to compensate for it, the system achieves high positioning accuracy without requiring tight manufacturing tolerances, thereby reducing manufacturing costs.
Solution Approach 2:
The patent replaces the mechanical solution (tight tolerances) with a sensor-based measurement and software compensation system. Instead of physically minimizing play through precision manufacturing, the system electronically detects and compensates for play, substituting mechanical precision requirements with computational correction.
2Measurement precision
If complex mechanical play measurement methods are used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent implements a self-service measurement approach where the system uses its own operational characteristics (motor current, position feedback) to automatically detect mechanical play without requiring external measurement equipment or complex test procedures. The control system itself performs the measurement function, eliminating the need for separate measurement devices.
Solution Approach 2:
The patent makes the control system multi-functional by enabling it to both control the motor and measure mechanical play using the same sensors and processing unit. The position sensor and current controller serve dual purposes: normal operation control and mechanical play detection, eliminating the need for dedicated measurement hardware.
3Productivity
If fast initialization and control are implemented, then productivity is improved, but positioning accuracy under load and vibration may worsen
Solution Approach 1:
The patent performs preliminary detection of mechanical play during the initialization phase before full load operation begins. By measuring and compensating for play early in the startup sequence, the system prepares the accurate positioning model in advance, enabling fast initialization while maintaining accuracy during subsequent loaded operation.
Solution Approach 2:
The patent implements continuous feedback from position sensors and current controllers that monitor system behavior under load and vibration conditions. This feedback enables real-time adjustment of compensation parameters, maintaining positioning accuracy even during fast operation and under varying load conditions.
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 approach provides a reliable, compact, and cost-effective actuation system with improved accuracy and robustness to parameter variations, maintaining precision throughout the lifespan of components and reducing manufacturing costs by moving complexity to software.
Implementation Method 1
an actuator with a stepper motor having at least one electrical phase
Implementation Method 2
an actuated system comprising an elastic element
Implementation Method 3
measuring a back EMF voltage in said at least one electrical phase with the supply current switched off and determining a mechanical position of the rotor
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Methods of compensating for play and for initializing a position encoder in an actuation system (2) including an actuated system (8) comprising an elastic element, and an actuator (4) with a stepper motor (12) having at least one electrical phase.