Load Control of a 300 h.p. Tunnelling Machine: The Addition of Integral Control Action to Prevent Manually Created Overloads

Whereas a proportional-plus-derivative controller (designed in Research Reports 220 and 230)for the Cadley Hill tunnelling machine was shown to produce only small load errors in response to changes in rock hardness, errors resulting from excessive manual rate settings were not investigated. It is here proposed that effective integral action can be incorporated to eliminate such errors, which can be excessive because of the very wide range of rate settings available to the driver. Implementations using a d.c. blocking circuit in the rate feedback channel of ther N.C.B. controller are tested connected to the analogue simulator of the tunnelling machine and shown to be successful. Redesign of the existing printed circuits will, however, be necessary to achieve an overriding controller that is completely error free.