Numerical control device, machine tool, numerical control method, and non-transitory computer readable medium

A numerical control method for controlling, by using a numerical control device, a position and a velocity of a movement part that moves relatively with respect to a target object by reading an NC program formed by a plurality of blocks indicating command points on a movement path of the movement part and processing the blocks sequentially, the numerical control method comprising:

• a reading process of reading a current block, which is a processing target among the blocks, and look-ahead blocks, whose processing order follows the current block among the blocks;
• a decision process of deciding a target block, which is a target among the current block and the look-ahead blocks read in the reading process, and deciding a target velocity which is a velocity as a target the movement part at the command point of the target block that is decided;
• a first calculation process of calculating, on the movement path of the movement part, a first rise velocity based on a maximum jerk as an upper limit of an allowed jerk, a current velocity of the movement part, and a current acceleration of the movement part, wherein the first rise velocity is a velocity of the movement part at a first rise point, the first rise point being a position where an acceleration of the movement part changes to a first predetermined acceleration from the current acceleration of the movement part;
• a reverse interpolation process of performing a reverse interpolation process as a process sequentially calculating reverse interpolation points that are positions where the movement part moves, from the command point of the target block decided in the decision process toward a start point of the current block in the movement path of the movement part, wherein an initial reverse interpolation point as the reverse interpolation point that is initially calculated, the velocity of the movement part at the initial reverse interpolation point, and the acceleration of the movement part at the initial reverse interpolation point are respectively the command point of the target block, the target velocity, and a second predetermined acceleration, and the reverse interpolation point to be calculated next to the current reverse interpolation point is a position where the movement part moves by an amount of movement for a predetermined time based on the velocity of the movement part and the acceleration of the movement part at the current reverse interpolation point, a maximum acceleration as an upper limit of an allowed acceleration, and the maximum jerk;
• and
• a second calculation process of calculating, on the movement path of the movement part, from the reverse interpolation point toward the start point of the current block, a second rise velocity based on the maximum jerk, the velocity of the movement part at the reverse interpolation point as calculated in the reverse interpolation process and the acceleration of the movement part at the reverse interpolation point every time when the reverse interpolation point is calculated in the reverse interpolation process, wherein the second rise velocity is the velocity of the movement part at a second rise point, the second rise point being a position where the acceleration of the movement part changes from the acceleration of the movement part at the reverse interpolation point to a third predetermined acceleration,
• wherein, in the reverse interpolation process, the reverse interpolation point is calculated until the second rise velocity calculated in the second calculation process becomes equal to or greater than the first rise velocity calculated in the first calculation process.

A non-transitory computer readable medium, storing a numerical control program, the numerical control program causing a computer of a numerical control device for controlling a position and a velocity of a movement part that moves relatively with respect to a target object by reading an NC program formed by a plurality of blocks indicating command points on a movement path of the movement part and processing the blocks sequentially to execute:

• a reading process of reading a current block, which is a processing target among the blocks, and look-ahead blocks, whose processing order follows the current block among the blocks;
• a decision process of deciding a target block, which is a target among the current block and the look-ahead blocks read in the reading process, and deciding a target velocity which is a velocity as a target the movement part at the command point of the target block that is decided;
• a first calculation process of calculating, on the movement path of the movement part, a first rise velocity based on a maximum jerk as an upper limit of an allowed jerk, a current velocity of the movement part, and a current acceleration of the movement part, wherein the first rise velocity is a velocity of the movement part at a first rise point, the first rise point being a position where an acceleration of the movement part changes to a first predetermined acceleration from the current acceleration of the movement part;
• a reverse interpolation process of performing a reverse interpolation process as a process sequentially calculating reverse interpolation points that are positions where the movement part moves, from the command point of the target block decided in the decision process toward a start point of the current block in the movement path of the movement part, wherein an initial reverse interpolation point as the reverse interpolation point that is initially calculated, the velocity of the movement part at the initial reverse interpolation point, and the acceleration of the movement part at the initial reverse interpolation point are respectively the command point of the target block, the target velocity, and a second predetermined acceleration, and the reverse interpolation point to be calculated next to the current reverse interpolation point is a position where the movement part moves by an amount of movement for a predetermined time based on the velocity of the movement part and the acceleration of the movement part at the current reverse interpolation point, a maximum acceleration as an upper limit of an allowed acceleration, and the maximum jerk;
• and
• a second calculation process of calculating, on the movement path of the movement part, from the reverse interpolation point toward the start point of the current block, a second rise velocity based on the maximum jerk, the velocity of the movement part at the reverse interpolation point as calculated in the reverse interpolation process and the acceleration of the movement part at the reverse interpolation point every time when the reverse interpolation point is calculated in the reverse interpolation process, wherein the second rise velocity is the velocity of the movement part at a second rise point, the second rise point being a position where the acceleration of the movement part changes from the acceleration of the movement part at the reverse interpolation point to a third predetermined acceleration,
• wherein, in the reverse interpolation process, the reverse interpolation point is calculated until the second rise velocity calculated in the second calculation process becomes equal to or greater than the first rise velocity calculated in the first calculation process.