Stepper Motor Chopper Control Adaptation
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Solution Overview
Problem
Stepping motors, particularly those with compact high-power density designs, face inefficiencies and potential stalling due to fixed step frequency controls, which lead to suboptimal torque usage and increased temperature, causing internal resistance changes that affect chopper pulse widths and motor performance.
Innovation Solution
Adapting the reference time period for chopper control based on real-time measurements of chopper pulse widths during energization and rest phases, using a look-up table to correlate these measurements with rotating conditions, allowing for dynamic adjustment of the reference time duration to match current working conditions, thereby optimizing motor operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed step frequency control is used, then the control is simple, but the motor operates inefficiently and may stall under high load
Solution Approach 1:
The patent applies dynamics by making the step frequency adaptive rather than fixed. The control system continuously monitors the chopper pulse width and adjusts the step frequency dynamically based on the motor's actual operating conditions, allowing the motor to operate at optimal speed under varying loads while maintaining simple control architecture.
Solution Approach 2:
The patent implements feedback by monitoring the chopper pulse width, which reflects the motor's current drawing characteristics and load conditions. This feedback signal is used to adjust the step frequency, creating a closed-loop control system that optimizes motor performance without requiring complex additional sensors.
2Productivity
If the step frequency is increased to improve productivity, then the motor may stall or lose steps under high load
Solution Approach 1:
The control system uses feedback from the chopper pulse width measurement to adjust the step frequency. When the pulse width indicates high current draw (suggesting high load), the system automatically reduces the step frequency to prevent stalling, while allowing higher frequencies when the load is lighter, thus maintaining both productivity and reliability.
Solution Approach 2:
The patent changes the operating parameter (step frequency) based on the motor's actual state as indicated by the chopper pulse width. This dynamic parameter adjustment allows the system to optimize between speed and reliability depending on the instantaneous load conditions.
3Force
If a higher current setpoint is used to increase torque, then the chopper pulse width increases, reducing the accuracy of step position detection
Solution Approach 1:
The system dynamically adjusts the current setpoint based on the measured chopper pulse width. When the pulse width deviates from the expected range, the system modifies the current setpoint to bring the pulse width back into the optimal detection range, thereby maintaining both torque and position detection accuracy.
Solution Approach 2:
The patent changes the electrical parameter (current setpoint) in response to deviations in the chopper pulse width. This parameter adjustment ensures that the pulse width remains within the optimal range for accurate step position detection while still delivering sufficient torque for the application.
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 method ensures the stepper motor operates closer to its optimal point, improving efficiency and allowing higher stepping frequencies by compensating for static and dynamic resistance changes, including temperature effects, and reducing the risk of stalling and inefficiency.
Implementation Method 1
In a stepper motor, the energization of the stator coils is controlled by control electronics in such a way that an electromagnetic field rotates step by step, which the rotor follows
Implementation Method 2
the inductance of a given stator coil is in turn dependent on the relative position of the rotor and stator coil to one another, which is highest when there is maximum stator-rotor overlap, i.e. when the stator and rotor are positioned directly in front of each other. As a result, the inductance of the stator coil is modulated as the rotor rotates
Implementation Method 3
the resistance of the windings of a copper coil increases by around 23% when the temperature rises by 60°C, for example. At constant voltage, the higher resistance of the windings leads to an increase in the width of the chopper pulses
Data Source
Figure 1~2
Figure 3~4
AI summary
The method involves energizing stator coils of a stepping motor by an electronic control system to generate rotating electromagnetic field. The current through the windings to a power set point is increased by the control electronics. The chopper pulse is enabled during current flow until the desired current value is reached. The period of time is required to compare the defined width of each chopper pulse with a predetermined reference time period. The reference time period is adapted to the working conditions of the stepping motor during the driving of the stepping motor.