Bi-Stable Motor Drive Mechanism for Soft Stop Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Bi-stable actuators in unstable systems, such as rotary solenoids, experience high terminal velocities and kinetic energy at the end of travel due to continuous acceleration, which is challenging to manage without position feedback sensors, especially when detent forces hold the actuator in place, leading to incomplete movement and high impact velocities.
Innovation Solution
A bi-stable motor drive mechanism with regulated velocity control is implemented, using sensed motor resistance and inductance to maintain accurate control, allowing the motor to be driven into a stop and calculating resistance and inductance values for precise velocity management, thereby reducing terminal velocity and kinetic energy at the end of travel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If timing control is used to limit actuator duration, then energy consumption is reduced, but velocity control precision deteriorates
Solution Approach 1:
The patent implements a feedback control system that continuously monitors the bi-stable actuator's position and velocity, using sensor data to adjust control signals in real-time. This closed-loop approach enables precise velocity control while optimizing energy consumption by adjusting current magnitude and duration based on actual actuator state rather than fixed timing parameters.
Solution Approach 2:
The control system dynamically adjusts electrical parameters (current magnitude, pulse duration) based on the actuator's real-time state and required velocity profile. This dynamic control replaces static timing methods, allowing the system to optimize energy consumption at each moment while maintaining precise velocity control throughout the actuator's travel range.
2Speed
If position feedback sensors are added, then velocity control is improved, but device complexity increases
Solution Approach 1:
The patent utilizes the bi-stable actuator's own electrical characteristics (back-EMF, current consumption, position-dependent electrical properties) as feedback signals for velocity control. This self-service approach eliminates the need for external position feedback sensors, as the actuator's inherent electrical behavior provides the necessary control information, thereby maintaining velocity control precision without increasing device complexity.
Solution Approach 2:
The control system uses the actuator's electrical parameters (current, voltage, back-EMF) for multiple purposes: both for driving the actuator and for sensing its position and velocity. This multi-functionality eliminates the need for separate sensing components, achieving precise velocity control without adding device complexity.
3Stability of the object's composition
If detent forces are increased to hold actuator position, then positioning stability is improved, but starting torque requirement increases
Solution Approach 1:
The control system applies preliminary action by building up current and velocity gradually before the actuator encounters the detent force. The feedback controller anticipates the detent event and adjusts the velocity profile in advance, allowing the actuator to approach the detent position at an optimized speed that minimizes the required starting torque while ensuring stable positioning upon engagement.
Solution Approach 2:
The system dynamically changes electrical parameters (current magnitude, voltage level) based on the actuator's proximity to detent positions, as detected through feedback signals. By adjusting these parameters in real-time, the controller optimizes the balance between overcoming detent forces and maintaining positioning stability, reducing peak torque requirements compared to static high-torque designs.
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 maintains high torque margins at low velocities, reduces kinetic energy, and establishes a softer stop, effectively controlling the actuator's movement without the need for position feedback transducers, significantly reducing impact velocity and energy.
Implementation Method 1
A bi-stable motor provides a high starting torque, but a slower, regulated velocity as it moves through its range of travel
Implementation Method 2
Back-emf is sensed through a sense resistor, and an estimated motor rotation rate is sent to a feedback loop to maintain the desired rate
Data Source
AI summary
A drive mechanism having a bi-stable motor driving an actuator with a high starting torque, and a slower, regulated velocity as the actuator moves through its range of travel. This advantageously maintains high torque margins at low velocity, and lowers the kinetic energy of the bi-stable actuator at end of travel by limiting the terminal velocity and establishing a softer stop. A solenoid may be used in one embodiment. Actual bi-stable motor values are obtained immediately before the move to maintain accurate control of the motor, such as the resistance and inductance of the motor coil. For instance, the bi-stable motor may be driven into a stop, and the coil resistance may be calculated by sensing current associated with the calibration voltage. Inductance may be measured similarly by applying low level AC currents. Back-emf is sensed through the coil resistance, and an estimated motor rotation rate is sent to a feedback loop to maintain the desired rate.