How to Enable and Disable a Drive

In order to enable a drive the Function Block MC_Power has to be used within the applicational layer. The kernel Function Block will then, if possible, output a rising edge on the output DRIVE_RELEASE which can be connected to the drive-control Function Block which performs the needed actions on the drives control word to enable the drive. As soon the drive states enabled, this signal can be connected to the input DRIVE_IN_OPERATION of the kernel Function Block. The axis state according to the single axis state diagram of PLCopen will then switch from Disabled to Standstill.

Enabling sequence of a drive

As long as the drive is in state Disabled or ErrorStop the input DRIVE_ACTUAL_POSITION will be copied to the output POSITION_REFERENCE of the kernel Function Block. The output SPEED_REFERENCE will be zero.

When the axis is in operation which means it is not in state Disabled or ErrorStop then the output POSITION_REFERENCE will be calculated by the kernel Function Block. And the position control loop will be closed which outputs non zero value for the output SPEED_REFERENCE in case of a following error. The input ACTUAL_POSITION should then follow the position reference. The difference of both values is the following error and will be supervised by the kernel Function Block.

In case of drive problem, DRIVE_INOPERATION should be reset. The Function Block will open the positon control loop and SPEED_REFERENCE will be set to zero.

For the most drives the status is control by the drives control word whereas the drives status word repesents its actual status. In order to enable the drive it might be necessary to pass through several drives states according a defined sceme which depends on the used drive. Therefore the library ECAT_AC500_APPL_V21.lib is added to PS552-MC which contains Function Blocks to operate with different drives on an ETHERCAT network. There is also the PS553-DRIVES software which can be used to control the state of a drive.