Abstract: A multi-operation control system is made up of a plurality of slave computers at least some of which are axis computers each monitoring its respective operation and receiving instructions broken down into plurality of discreet actions. The current state S.sub.c,N of each slave is determined and is compared with preset absolute maximum status for that slave S.sub.ab,N(max) and the maximum acceptable change in status .delta.S.sub.a,N(max) of each respective slave is determined and the corresponding appropriate state signal based on the maximum acceptable change to that slave is sent to all of the slaves in the system. Each axis slave then reads all state signals and determines the highest state signal acceptable to all slaves and each axis slave then carries out its correspond increment(s) of change in status .delta. S.sub.N based on the highest S.sub.a,N(max) acceptable to all slaves.

Abstract: The desired path for each axis is predefined and converted to a first series of coarse position increments at time intervals. The coarse position increments are converted to a second series of spaced, (in time), fine position increments and expected values of velocity v. The latter parameters requiring splining and interpolation of values. The actual position of each axis is measured and compared with that required (by the fine series of position increments) to determine the resulting error E which is then compared with a calculated allowable error, e.sub.allowable calculated as a function of the then current planned velocity value v i.e. the planned value of velocity v corresponding to the current fine position increment and a signal is triggered when the actual error E exceeds the allowable error e.sub.allowable to prevent processing of the next increment in the second series of increments.

Abstract: A multi-operation control system includes a plurality of slave computers each controlling its respective operation and forming at least one operating system. Each slave computer has a memory for storing a plurality of sequential movement instructions to be carried out by the slave and the micro-controller. Each slave computer monitors the operation it controls, compares the monitored operation with the current movement instruction and generates a flag signal if the monitored operation and current movement instruction differ by more than a preselected amount. This flag signal is transmitted to all of the slave computers of the operating system of which the slave computer is a part. The slave computers carry out their movement instructions in steps in working time increments. The step of movement to be carried out in a time increment is updated only when no flag signal is received by the slave computers, i.e.

Abstract: A propeller system is formed on a shaft by at least one pair of axially spaced propeller blades each having a first and a second blade section extending at a selected acute (or obtuse) angle to the axis of the shaft, the first sections and second sections respectively of the pair of propeller blades are substantially parallel to each other and the tips of the first sections of each of the blades are connected to the tips of the second section of each of the blades respectively to form a box shape. The shaft is connected to the propeller system in a manner so that the axis of the shaft extends substantially diagonally of the box shape whereby the parallel sections of the blades move in opposite directions relative to the fluid in which they are contained when the shaft is rotated to facilitate improvement of the efficiency of the propeller system.

Abstract: A tool wear detector is formed by applying a resistor, the resistance of which is permanently altered in accordance with a time/temperature relationship (and by change in size e.g. as a result of wear), to a tool in a manner so that the resistor and the portion of the tool to be monitored are subjected to corresponding temperature cycles. Measuring the resistance of the resistor at any time provides an indication of the cutting conditions to which the monitored portion of the tool has been subjected and thereby an indication of the remaining life of the portion of the cutting edge of the tool being monitored.