Linear Actuator Force Matching via Back EMF Feedback
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Solution Overview
Problem
In systems utilizing multiple linear actuators, unbalanced forces can degrade performance and reduce linearity, particularly in applications like scanning mirrors, where precise control and feedback are critical to maintain the integrity of the reflected surface figure.
Innovation Solution
A controller is used to identify and match the back electromotive force (BEMF) of each actuator, ensuring that forces provided during actuation and retrace modes are substantially equal, thereby balancing the forces and maintaining linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple linear actuators are used to provide controlled force to an actuatable member, then the system can achieve precise positioning and force control, but unbalanced forces from the actuators can reduce linearity and degrade performance
Solution Approach 1:
The system measures the back EMF of each actuator during retrace mode and uses this feedback information to adjust the control signals during actuation mode. The controller continuously monitors actuator performance and dynamically adjusts drive signals to balance forces, ensuring that faster actuators are driven more aggressively while slower actuators are driven more conservatively to achieve substantially equal force output from all actuators.
Solution Approach 2:
The system changes the control parameters (drive signals) based on measured back EMF values. By adjusting the magnitude and timing of drive signals to each actuator according to its specific back EMF characteristics, the system compensates for variations in actuator performance and achieves force balancing across all actuators, thereby maintaining linearity and reducing distortion.
2Measurement precision
If feedback control is implemented to maintain actuator performance, then positioning accuracy is improved, but system complexity increases
Solution Approach 1:
The system implements feedback control by measuring back EMF during retrace mode and using this information to adjust actuation. The controller receives feedback signals from back EMF sensors, processes this information to determine force imbalances, and generates corrected drive signals to balance actuator forces, thereby maintaining positioning accuracy while managing control complexity through efficient feedback utilization.
Solution Approach 2:
The actuators themselves provide the feedback signal through their back EMF, eliminating the need for separate sensors on each actuator. The back EMF naturally reflects the actuator's performance characteristics and force output, allowing the system to self-diagnose and self-correct force imbalances without requiring complex external measurement systems.
3Ease of manufacture
If actuator performance variations due to temperature and age are accommodated through tolerances, then integration is simplified, but performance precision is reduced
Solution Approach 1:
The system dynamically adjusts control parameters to compensate for actuator variations caused by temperature and age. By measuring back EMF under actual operating conditions and adjusting drive signals in real-time, the system maintains precise force control despite environmental changes and component aging, eliminating the need for conservative tolerances that would otherwise be required to ensure consistent performance.
Solution Approach 2:
The control system transitions from static tolerance-based design to dynamic compensation. The controller continuously adapts its control strategy based on real-time back EMF measurements, allowing the system to maintain high precision across varying operating conditions and component lifetimes without requiring complex mechanical adjustments or replacement schedules.
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 effectively balances actuator forces, reducing distortion and maintaining the linearity of the system, even in the presence of temperature and age-related variations, thereby enhancing the integrity of the reflected surface figure and image quality.
Implementation Method 1
identify a parameter of each of the actuators during a retrace mode of the member returning from a second position to a first position; wherein the parameter comprises a back electromotive force 'BEMF' of each of the actuators
Data Source
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AI summary
A system includes a plurality of actuators configured to provide forces to an actuatable member to actuate the member between a first position and a second position during an actuation mode. The actuators are also configured to return the member from the second position to the first position during a retrace mode. The system also includes a controller configured to control the actuators. The controller is configured to identify a back electromotive force (BEMF) of each of the actuators during the retrace mode. The controller is also configured to responsively provide control signals to drive the actuators such that the forces provided by the actuators to the member during the actuation mode are substantially equal.