Bespoke Instrumentation - Case Studies

Aircraft Wing Brake Test Rig

JK Controls have designed, developed and built bespoke instrumentation and controls for a test stand for a prototype aerolon brake.
The aerolon drive shaft is held by an electrically operated brake when not required to rotate. The brake has to bring the shaft to a halt within 40mS of being de-energised. For testing purposes the shaft is rotated by a motor at up to 1500 rpm. The motor is driven by a variable speed inverter at a preset speed. On de-energising the motor, the shaft free-wheels for a few msecs and the speed is measured. The brake is then de-energised and the shaft monitored until it ceases to rotate. Timers automatically start and stop during the braking event.

This project required several custom designed components where there were no suitable proprietary products available. As the shaft stops within 40 msec. it only turns about one quarter of a turn from running to stopped. Therefore the speed was measured using a very fine resolution printed slotted wheel and a suitable optical detector. Physical constraints prevented access to either end of the shaft, the slotted disk was therefore custom made, together with the high speed optical detector by JK Controls Ltd. Using fast hardware processing the shaft was determined as stopped when the pulse repetition rate dropped below a threshold. The timing and measurement logic was designed and built on to custom printed circuits. During the braking period the brake torque is measured by a strain gauge and the peak braking torque, in both directions, is stored. Analogue hardwired circuits were built to sample-hold for peak torque and initial speed stores. The stored values are displayed on suitably scaled digital indicators.

The sequence of running up the motor, priming the data collection and timers, initiating the test and monitoring the results was handled by a small PLC. Various safety interlocks are built in to prevent operation under unsafe conditions. Great care was taken to minimise sensitivity to, and radiation of, electro-magnetic interference.

Brake Test Rig
Occulting Disk

Control Panel
Peak Torque Detector
Optical Detector

Remote camera controls

Typical console opened up
A power plant company use many specialist techniques for plant inspections during overhaul periods. One need was for an operator console to house the controls and monitors. JK Controls Ltd built a pair of custom consoles that could vary the lighting and monitor the temperatures of the cameras and their inclination from normal within the plant. The horizontal shift of one camera could also be altered remotely to adjust the stereoscopic imaging.
JK Controls have also built bespoke control consoles for video display, recording and camera monitoring.

Cable wrapper speed analysis

A specialty cable manufacturing company required a measurement of deceleration of cable insulation winding heads with a time resolution of a few milliseconds. Access to the plant was extremely restricted. JK Controls designed and manufactured signal conditioning equipment and a small custom transducer to run on the surface of the winding head. The measured speed was recorded on a high speed recorder which could indicate any non-linearity in the deceleration and any over-run of the drive mechanism.

Generator loading monitor

Power station operators have to supply power to the National Grid within very tight margins. If they run below target they suffer penalties, but if they supply above target they do not get paid for the excess energy. To walk this tightrope during steady running is sometimes difficult, but to follow the moving target load after synchronizing and whilst raising load is much more difficult.
JK Controls have built a PC based monitoring system that enables the operator to input the type of run up and the target load and time. This will then draw the load trajectory on the screen with tramlines to indicate the tolerance allowed. Once synchronized, the generator load will be plotted on this screen in real time and the operator will endeavor to drive the plant to maintain the generator output within the tramlines.

Contact Information: e-mail to info@jkcontrols.co.uk, or telephone +44 2380 892021

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