A numerical control device comprising an acceleration/deceleration characteristic acquisition part which acquires predetermined acceleration/deceleration characteristic information showing a correspondence between a command speed and a maximum acceleration of a spindle, a rotation amount acquisition part which acquires predetermined rotation amount information showing the rotation amount of the spindle for a period from when feed operation of the spindle is started to when a tapping tool reaches a bottom of the hole of a workpiece, a machining time calculation part which calculates a correspondence between the command speed and a machining time required to reach the rotation amount, based on the acceleration/deceleration characteristic information and the rotation amount information, and a speed determination part which determines an optimum value of the command speed for minimizing the machining time, based on the correspondence calculated by the machining time calculation part.

A motor controller executes an axis module for each of multiple motors coupled to a shared load. A first control module passes at least one state variable to a second control module without experiencing communication delays between the axis modules. In order to decouple interaction between axes, the first control module determines the desired state variable at a periodic update rate and stores the desired state variable in memory. The first control module provides an indication to the second control module that the desired state variable is available. Within the same period at which the desired state variable is determined, the second control module receives the indication that the desired state variable is available and reads the state variable from the memory of the controller. The second control module executes using the desired state variable to reduce coupling between the two control modules.

A control device (1) of a gear processing machine has a bus (51) that communicates by directly connecting between a tool axis controller (22) and a workpiece axis controller (12), and, in this control device, the position of a tool axis (40) that is detected by a tool axis position detection sensor (25) is supplied to a workpiece axis controller via a bus, an upper controller (10) supplies a predetermined synchronization ratio and a superimposition command for applying a twisting operation to a workpiece axis controller, and the workpiece axis controller adds a value that is generated by multiplying the position of the tool axis that is supplied via the bus, by the synchronization ratio, and the superimposition command, and generates a motion command for a workpiece axis (30).