High Speed Turbine Controller

Also:
Image Acquisition and Archiving
300mm Semiconductor Defect Review
300mm Semiconductor Factory Automation

Technologies, Tools and Standards Employed:
In-house PC board design, embedded Z80, MAGIC/L based interpretive debugger, Visual Basic, CP/M assembler, RS-232

Problem:
Design and develop a high speed closed loop system capable of running any size turbine at speeds between 60 and 100,000 rpm, using current loop controlled high-pressure air valves. The controller must be capable of ramping turbines up and down to user selected target rpm's quickly and without overshoot. The unit is to be remotely controlled via serial connection as well as locally operable through its front panel.
The system was required to be fault tolerant, such that a power loss or voltage spike would not send a turbine into a dangerous rate of rpm.

Solution:
The problem is made very difficult by the requirement that all turbine sizes be controlled for all rpm's.
Acorn designed an embedded processor system with output relays and a controllable current source to actuate high pressure air valves for break, acceleration and main control. A closed loop algorithm was employed using rpm, sampled 60 times a second, as feedback, and current (4-20 ma) as output. A proportional output algorithm with adjustable offset and gain were decided upon as the simplest solution. The gain is set to match the turbine size and the offset is adjusted automatically by the software as current rpm is compared against target rpm. The controller memorizes a turbine's output requirements as it ramps up to the target rpm. As a result of this memorization, in subsequent runs the controller can ramp the turbine up to its rpm target rapidly. This rapid cycling saves the customer valuable time in their turbine tests.

The design continues to perform on all sizes of turbines providing safe, reliable control in various sorts of noisy manufacturing environments.

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