The vehicle body assembly station comprises main transport assembly for conveying a vehicle body along a first direction D1 in which at least one assembly robot is provided to move along a second direction D2, and temporary transport assembly whose operation is more accurate than that of the main transport assembly for moving the vehicle body independently from the main transport assembly while the assembly robot is performing operations on the vehicle body, whereby a new coordinate reference system is created by the temporary transport assembly.

A numerical controller has a first axis (reference axis) and a second axis (superimposed axis), and performs superimposed control which superimposes a movement amount of the reference axis on a movement amount of the superimposed axis, and thereby controls the movement of the superimposed axis. The numerical controller controls an acceleration start time of the axis to be accelerated, in a superimposition interval in which the reference axis is accelerated and the superimposed axis is decelerated (or reference axis is decelerated and superimposed axis is accelerated). After the axis to be decelerated is sufficiently decelerated, the axis to be accelerated is accelerated, and a moving speed of the superimposed axis does not exceed a speed limit of a machine in an acceleration/deceleration interval.

The vehicle body assembly station comprises main transport assembly for conveying a vehicle body along a first direction D1 in which at least one assembly robot is provided to move along a second direction D2, and temporary transport assembly whose operation is more accurate than that of the main transport assembly for moving the vehicle body independently from the main transport assembly while the assembly robot is performing operations on the vehicle body, whereby a new coordinate reference system is created by the temporary transport assembly.

A numerical controller controls a machine tool which carries out machining by moving a workpiece or a tool using a periodic operation cycle for repeatedly executing the same operation. The numerical controller stores command data of each execution period of a superposition cycle superimposed with the periodic operation cycle. Command data sets of the superposition cycle are synthesized every execution cycle in synchronization with execution timing of the periodic operation cycle.