Monitoring & Controlling a Linear Motor - Isis Project No 917
A University of Oxford researcher has developed new and improved software for controlling and operating a linear motor or compressor.
Background
Monitoring the state of mechanical, electrical or electronic systems is normally achieved by including sensors that are designed to measure specific operating parameters. Direct measurement by sensors can on occasion be detrimental especially where the sensor changes the system being monitored, for example, by requiring power itself.
The linear electric motor is a linear transducer which combined with non-contacting bearings and seals offers a number advantages, such as oil free operation, over conventional rotary motors. Of particular importance in operating a linear motor is the measurement and control of the stroke and the offset, where the offset is the mean position of the moving part of the transducer. Such mean position is not easily measured when the transducer is in sinusoidal motion, unlike in a rotary machine where such parameters are fixed by geometrical restraints.
Problem
If the stroke and the offset are not controlled, damage can occur if the axial movement exceeds the design range resulting in inadvertent contact between different parts of the system. Close control is necessary to optimise machine efficiency. Currently these parameters are controlled by attaching a displacement transducer to the moving part of the linear transducer; this together with the associated electronics adds significantly both to cost and weight. The additional complexity also reduces reliability.
The Oxford Invention
A linear motor model having a high level of correlation with a working system has been developed. By matching the actual voltage and current inputs with those in the model, values of parameters corresponding closely to real values can be found, and these can then be used to monitor and control the motor's operation. The process has the major advantages of being simple to operate, no additional hardware is necessary, therefore no additional weight, and the degree of complexity is much reduced.
Commercialisation Opportunity
This patent application is available for licensing, and companies interested in developing and using this technology are invited to contact Isis Innovation for further discussion.