Method for and control system with piston amplitude recovery for free-piston machines
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Solution Overview
Problem
Existing methods for controlling the displacement amplitude of linear motors and alternators connected to free piston Stirling machines are inefficient, requiring additional sensors and computational power, and are prone to errors due to changing load conditions and machine wear, which can lead to collisions and reduced performance in applications like deep temperature freezers.
Innovation Solution
A method and apparatus that detect displacement amplitude using readily accessible electrical parameters such as RMS or peak voltage, current, and power factor at the motor or alternator terminals, allowing for continuous monitoring and control without the need for additional sensors, using simplified equivalent circuits to compute the displacement amplitude within practical computational limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional sensors are used to directly sense displacement amplitude, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces mechanical displacement sensors with an electrical parameter-based computation system. By measuring voltage, current, and power factor at the motor terminals and computing displacement amplitude through mathematical relationships, the invention eliminates the need for direct mechanical sensing devices while achieving accurate displacement measurement.
Solution Approach 2:
The patent introduces electrical parameters (voltage, current, power factor) as intermediary measurements that can be easily obtained at the motor terminals. These electrical measurements serve as mediators to infer the mechanical displacement amplitude without requiring direct mechanical contact or additional sensors on the moving parts.
2Measurement precision
If complex computational methods are used to recover displacement amplitude, then measurement precision is improved, but productivity decreases due to longer computation time
Solution Approach 1:
The patent transforms the displacement measurement problem from direct mechanical sensing to electrical parameter computation. By changing the measurement domain from mechanical to electrical parameters and using simplified computational relationships based on motor equations, the system achieves both accuracy and real-time performance suitable for control applications.
3Reliability
If control systems are made more sophisticated to handle changing load conditions and machine wear, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements a feedback control mechanism where the computed displacement amplitude is continuously monitored and used to adjust the motor control. This feedback loop automatically compensates for changing load conditions and machine wear, maintaining reliable operation without requiring complex predictive models or additional sensing infrastructure.
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
Enables continuous detection and control of displacement amplitude, preventing collisions and optimizing power delivery, thereby improving the efficiency and reliability of free-piston machines by accurately determining the maximum allowable piston amplitude under varying conditions.
Implementation Method 1
Electrical linear motors and linear alternators are commonly known devices for driving a diverse variety of mechanical loads in reciprocation or for converting the linear reciprocation of another type of prime mover into alternating electric current
Data Source
AI summary
A method and apparatus for detecting the displacement amplitude of an armature of a linear motor or alternator that is drivingly coupled to a load or prime mover. The method and apparatus require only three inputs all derived from the input terminals of the linear motor or alternator: (1) the voltage measured across the linear motor terminals; (2) the current consumed by the linear motor; and (3) the phase between the voltage and current. The three inputs are sensed at the terminals of the linear motor or alternator and used to perform mathematical calculations in the microcomputer of a control system or controller. The mathematical calculations are based on equivalent circuits that are modifications of the equivalent circuit for the linear motor or alternator. The detected displacement amplitude can be used by a controller to limit the displacement amplitude of the armature to prevent collisions.