Synchronous control apparatus

A synchronous control apparatus that executes synchronous control of a main shaft and a driven shaft in each control period, comprising:

• a storage that stores a representation of a first cam curve and a representation of a second cam curve;
• and
• a controller that calculates a position command value of the driven shaft to control the driven shaft with the calculated position command value,
• wherein before switch-over of the cam curves, the controller finds the position command value to a driven-side member, based on a value on the first cam curve at each control timing,
• after the switch-over of the cam curves, the controller finds the position command value, based on a value on the second cam curve at each control timing, and
• in a switch-over period of the cam curves, the controller finds the position command value to the driven-side member based on a value obtained by utilizing first data based on one of the first cam curve and a position of the driven shaft and second data based on the second cam curve to provide a weighted average at each control timing,
• wherein in the weighted average, a weight is variable in conjunction with a main shaft position, and at start timing of the switch-over period, a weight of the first data is set larger than a weight of the second data, and at end timing of the switch-over period, the weight of the first data is set smaller than the weight of the second data.