Redundant Actuator Position Control With Fail-Safe Limit Switches
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Solution Overview
Problem
Electrically driven position control devices often fail to prevent actuators from exceeding their position limits due to calibration losses, software errors, or electronic hardware failures, potentially causing damage to the actuator and associated systems.
Innovation Solution
An actuator position control system that includes an electrical drive motor system controlled by an encoder and electronic controller, with limit switches that interrupt power to the motor when limits are reached, providing calibration signals to maintain accurate position monitoring and prevent overextension, and an electromechanical controller for backup operation and user alerts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an electronic control system is used to control actuator position between limits, then position control capability is improved, but reliability deteriorates due to calibration loss and hardware failure
Solution Approach 1:
The patent introduces mechanical limit switches as intermediary devices that physically interrupt power to the actuator when position limits are reached. These switches act as a mediator between the electronic control system and the actuator, providing a fail-safe mechanical barrier that prevents damage even when electronic calibration is lost or hardware fails.
Solution Approach 2:
The system implements beforehand cushioning by using redundant limit switches positioned at both extremes of the actuator's range of motion. These switches are pre-positioned to interrupt power before the actuator can exceed its safe operating limits, cushioning against potential damage from electronic failures, calibration drift, or power surges.
2Reliability
If a simple electromechanical control system with limit switches is used, then reliability is improved, but position control capability deteriorates
Solution Approach 1:
The patent merges two control approaches into a single hybrid system: electronic control for precise position adjustment between limits, and mechanical limit switches for reliable fail-safe protection. This combination allows the system to enjoy both the position control capability of electronic systems and the reliability of electromechanical systems.
Solution Approach 2:
The limit switches provide feedback to the control system when position limits are approached or exceeded. This feedback mechanism allows the electronic controller to monitor the actuator's position and respond appropriately, maintaining control capability while ensuring reliability through the mechanical backup.
3Ease of operation
If electronic control systems are used in environments with power fluctuations, then position control capability is maintained, but reliability deteriorates due to power surges and fluctuations
Solution Approach 1:
The patent applies preliminary anti-action by positioning limit switches that proactively interrupt power to the actuator when limits are reached, counteracting the harmful effects of power surges and fluctuations before they can cause damage. This preemptive measure protects the system even when electronic control becomes unreliable due to power issues.
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 effectively controls actuator positions between limits, preventing damage from calibration or hardware failures, ensuring reliable operation even in environments with power fluctuations, and providing visual and electrical position indicators for added safety.
Implementation Method 1
the sensors are Hall-effect magnetic field sensors
Data Source
AI summary
An actuator position control system includes an electronic controller and encoder that control and monitor an actuator's position between its position limits, while mechanically actuated limit switches prevent attempts to exceed the actuator's position limits, even if there is a loss of calibration, software error, or electronic controller failure. When actuated, the limit switches provide position calibrating information to the electronic controller. Embodiments can control linear and/or rotary actuators. The encoder can include intermeshed gears and magnetic Hall-effect position sensors. A mechanically driven position indicator can visually indicate the actuator's position. An electromechanical control system can be included that can transition the actuator between its limits even in the event of electronic controller failure. Embodiments can alert a user if the electronic controller fails.