Electromagnetic Actuator Position Sensing Under Stray Field Compensation
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Solution Overview
Problem
Linear actuators face interference from stray magnetic fields, which affect the accuracy of position control due to unwanted superposition with the magnetic field used for position sensing, leading to incorrect information about the tappet's position.
Innovation Solution
An actuator device with a compensating device that determines a variable related to the stray magnetic field, such as the actuator current, and adapts the measurement signal to account for this interference, ensuring accurate position control by compensating for the stray field's influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position sensor using a magnetic field is used to determine the tappet position, then position information can be obtained, but the magnetic field of the position sensor interferes with the electromagnetic field of the actuator coil and vice versa
Solution Approach 1:
The patent extracts the harmful stray magnetic field effect from the measurement system by introducing a separate compensating device that generates a counteracting magnetic field. This compensating field is specifically designed to cancel out the interference from the actuator coil, thereby removing the harmful interaction while preserving the position measurement function
Solution Approach 2:
The control unit acts as an intermediary that processes information from both the position sensor and the actuator coil, and coordinates the compensating device to generate an opposing magnetic field. This intermediary control mechanism mediates between the conflicting magnetic fields, allowing both the actuator and sensor to function simultaneously without direct interference
2Force
If the actuator coil generates an electromagnetic field to move the tappet, then linear movement is achieved, but a stray magnetic field is generated that influences the position sensor measurement signal
Solution Approach 1:
The patent converts the harmful stray magnetic field into a beneficial compensating field by using the control unit to calculate the required compensation and activate the compensating device. The same electromagnetic principles that create the harmful field are harnessed to generate an opposing field that cancels the interference, turning the problem into a solution
Solution Approach 2:
The patent changes the magnetic field parameters by introducing a compensating field with specific strength and direction that opposes the stray field. The control unit dynamically adjusts the compensation parameters based on the actuator coil current and position sensor readings, thereby maintaining measurement accuracy across different operating conditions
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 solution effectively compensates for the interfering effects of stray magnetic fields, enabling precise control of the tappet's position by adapting the measurement signal based on the determined variable, thereby improving positional accuracy.
Implementation Method 1
a control voltage is in this case applied to the actuator coil and an electrical actuator current flowing within the actuator coil as a result of the control voltage generates an electromagnetic field in the vicinity of the actuator coil. The electromagnetic field generated exerts a force on the tappet
Implementation Method 2
The electromagnetic field generated exerts a force on the tappet, which as a result of the force moves in or against the longitudinal direction
Implementation Method 3
The sensor element is designed in such a way as to generate a measurement signal in dependence on a magnetic field generated by the transmitter element, which is detected by the sensor element during operation
Implementation Method 4
The control unit includes a compensating device, which is set up so as to determine a variable correlated with the stray magnetic field and to adapt the measurement signal in dependence on this variable... the measurement signal is adapted on the basis of the determined variable so as to take into account the influence caused by the stray field, so that it is compensated for
Data Source
AI summary
An electromagnetic actuator device includes an actuator having an actuator coil and a tappet that can be moved in and against a longitudinal direction. The actuator device includes a sensor device having a transmitter element arranged on the tappet and a sensor element for generating a measurement signal, containing information about a current actual position of the tappet, depending on a magnetic field generated by the transmitter element. The actuator device includes a control unit with a controller, which applies a control voltage to the actuator coil for generating an electromagnetic field during operation in dependence on a position signal based on the measurement signal, so that the tappet moves into a target position. During operation, a stray magnetic field is generated by the at actuator coil, an adaptation of the measurement signal is performed to compensate for the influence on the measurement signal caused by the stray field.