Handling Multiturn Overflow in KAS for Non Modulo Axis

A multiturn encoder delivers feedback position in 32 bits format. The lower 20 bits provides single turn information and the higher 12 bits provides the multiturn information.

The 12th bit from multiturn is the sign bit. Hence the complete range of the encoder is from –ve 211 multiturn bits to +ve 211 multiturn bits. Fig. shows an application example where the bit overflow problem occurs on machine power on.

IIn the above example, the axis is limited to run from 0 UU to 600 UU. If the zero position of axis is set at pt.A as shown in green color, then there’s no problem of overflow during power on. However, if the zero position is at pt.A, as shown in blue color, then the bit overflow problem occurs, when the axis stays in between Pt. C and pt.B in blue color, during power on. If the axis is powered on between pt. C and pt.B in blue color, then we
have a bit overflow problem. The axis actual value would be out of the axis limits.

To overcome this problem, the value UUperTurn*4096 must either be subtracted or added once during the power on. The feedback position is stored as offset, when the axis zero position is set to zero.

A sample KAS code is in the attachment.