A grid plate encoder based positioning system (1) for positioning of an element is provided, the positioning system (1) comprises a grid plate (2) with a grid plate surface (21); an encoder unit (3) with one or more optical sensors (31) for sensing a grid plate surface pattern (23) of the grid plate surface (21); an input (7) to receive coordinates (Xd, Yd) specifying a desired position of the element; a mapping unit (8) to compute compensated coordinate data (Xa, Ya) corresponding to estimated position data expected from the encoder unit (3) when the element is positioned at a desired position (Xd, Yd) specified by the setpoint coordinates; a feedback control unit (9) providing the compensated coordinate data (Xa, Ya) as a setpoint (Xs, Ys) to a positioning unit (12), with feedback control based on the estimated position data obtained from the encoder unit.

Additionally, a grid plate encoder based positioning method and a method for computing compensation data are provided.

Provided is a numerical control device capable of positioning a tool tip position in three-dimensional space with high accuracy. A numerical control device (1) includes a position compensator (5) and an error data storage (10). The error data storage (10) stores therein error data relating to angular errors (Eax, Eay, Eaz) around an X-axis, angular errors (Ebx, Eby, Ebz) around a Y-axis, and angular errors (Ecx, Ecy, Ecz) around a Z-axis in the X-, Y-, and Z-axes. The position compensator (5) calculates, based on commanded positions (Ix, Iy, Iz), the error data, and tool length data for a tool to be used, modification amounts (Mx, My, Mz) that vary in accordance with the tool length, modifies compensation amounts (Cx, Cy, Cz) for the commanded positions (Ix, Iy, Iz), and compensates for the commanded positions (Ix, Iy, Iz) with the modified compensation amounts.

A motor control device for controlling driving of a motor based on position commands input from a host control device includes an offset value memory including first circuitry which stores offset values corresponding to predetermined values of position commands, respectively, and a drive controller including second circuitry which acquires, from the offset value memory, one of the offset values corresponding to an input position command among the position commands, and control driving of a motor based on an offset position command obtained by adding the one of the offset values to or subtracting the one of the offset values from the input position command.