Stepper Motor Gripping System Using CEMF Monitoring
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Solution Overview
Problem
Conventional electric gripper control methods face challenges in stabilizing gripping force due to rapid rotation speed changes, leading to out-of-step issues and increased structural complexity, which complicates the mechanical design and increases manufacturing costs.
Innovation Solution
A gripping system monitored based on counter electromotive force (CEMF) using a stepper motor connected to a controller with a drive unit, control unit, and access unit, where a 3-D control parameter matrix defines CEMF thresholds for gripping status, speed, and force, allowing real-time monitoring and control to prevent out-of-step occurrences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the rotation speed of the stepper motor is controlled to adjust gripping force, then the gripping force can be regulated, but rapid rotation speed changes cause torque decrease and out of step occurrences
Solution Approach 1:
The patent employs feedback control by monitoring the actual counter electromotive force (CEMF) of the stepper motor and comparing it with threshold values from a pre-stored CEMF map. This feedback mechanism enables real-time detection of out-of-step conditions and allows the system to adjust rotation speed dynamically, preventing torque loss and maintaining grip stability while regulating gripping force.
Solution Approach 2:
The patent pre-calculates and stores the counter electromotive force values at different rotation speeds in a CEMF map during the design phase. This preliminary action enables the control system to quickly reference appropriate CEMF thresholds during operation, allowing proactive prevention of out-of-step conditions before they occur, thereby maintaining reliable gripping force control.
2Reliability
If an additional sensor and retaining mechanism are added to detect and maintain gripping force during out of step, then the gripping force can be maintained, but the mechanical structure becomes complicated and manufacturing cost increases
Solution Approach 1:
The patent replaces the mechanical retaining mechanism and additional sensors with an electrical control solution based on CEMF monitoring. By detecting out-of-step conditions through electrical signals (CEMF changes) and responding through motor control, the system achieves the same gripping force maintenance function without adding mechanical complexity, reducing device complexity while maintaining reliability.
Solution Approach 2:
The patent enables the stepper motor to self-diagnose out-of-step conditions by monitoring its own CEMF output. The motor's electrical characteristics provide inherent feedback about its operational state, eliminating the need for external sensors to detect problems. This self-service approach maintains gripping force reliability without adding external monitoring components.
3Force
If the motor power is cut off immediately when out of step occurs, then the gripping force can be preserved, but the occurrence of out of step becomes unavoidable and grip stability is affected
Solution Approach 1:
The patent pre-establishes a CEMF map with threshold values for different operating conditions before actual use. This preliminary preparation enables the control system to proactively adjust motor parameters before out-of-step conditions develop, preventing torque loss rather than merely responding after the fact. This approach maintains both gripping force and grip stability by avoiding out-of-step occurrences entirely.
Solution Approach 2:
The patent implements continuous feedback monitoring of the stepper motor's CEMF during operation, comparing real-time values against pre-stored thresholds. This feedback enables dynamic adjustment of rotation speed to prevent out-of-step conditions, allowing the system to maintain stable gripping force without needing to cut power abruptly, thereby preserving both force and stability.
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
The system stabilizes gripping forces by preventing out-of-step conditions, simplifying the mechanical structure, reducing manufacturing costs, and improving yield rates by using real-time CEMF monitoring and control, ensuring consistent gripping performance.
Implementation Method 1
a feedback actual counter electromotive force of the stepper motor
Data Source
AI summary
A gripping system which is monitored based on CEMF and a method for controlling the same includes: using a controller to instruct a drive unit to rotate a stepper motor; using the controller to compare the control instruction with a control parameter matrix stored in an access unit; obtaining a CEMF threshold by checking the position of the actual CEMF in the control parameter matrix; using the controller to continuously monitor the actual CEMF; and using the controller to compare the actual counter electromotive force with the obtained corresponding counter electromotive force threshold, stopping the stepper motor and letting the gripper maintain the gripping status when the actual counter electromotive force is smaller than or equal to the counter electromotive force threshold, and maintaining driving of the stepper motor when the actual counter electromotive force is larger than the counter electromotive force threshold.