The SM3_Basic library contains superordinate function blocks that do not interact with the drive over the standard set/actual value interface. These function blocks provide commands or change the settings of the drive by reading or writing the parameters of the instance of AXIS_REF_SM3.
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If you have changed the drive parameters at runtime, then you must reinitialize the drive. Example: Change the scaling factor or the position cycles of rotary drives. By calling the SMC3_ReinitDrive function block with a rising edge at the Execute input, the wCommuncationState parameter of the drive is reset and the complete start process of the drive is repeated.
Notice
Wait with the reinitialization until the axis reaches the required state SMC_COMSTATE_BASE_COM_INITIALIZATION or higher. Otherwise the error will print SMC_RAG_ERROR_AXIS_NOT_INITIALIZED.
If the communication of a subordinate fieldbus is interrupted, then reinitialization is required as well. If this kind of error occurs with SMC_DI_GENERAL_COMMUNICATION_ERROR, then the following error handling is required.
Error handling
Restart the fieldbus
Note
You can configure some fieldbuses so that they restart automatically. It is often necessary for you to add a special error handling of the fieldbus by means of IEC code.
⇒ Fieldbus communication starts
Restart the drive/axis with SMC3_ReinitDrive.
⇒ Drive/axis starts.
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The bRegulatorOn and bDriveStart parameters of the AXIS_REF_SM3 function block control the performance level and deceleration of a drive. Access is made by means of the MC_Power function block.
To release the output stage, you must set the bRegulatorOn parameter of the MC_Power function block. The drive reports the current status of this process via the bRegulatorRealState output. If the drive supports it, then a bRegulatorOn reset deactivates the torque immediately during the movement. In this case, the function block reports an error and sets the axes to the errorstop state.
The bDriveStart variable determines whether or not the drive can move. The current state of this parameters is found in bDriveStartRealState.
If the drive supports it, then a bDriveStart parameter reset decelerates the drive with the configured ramp (QuickStop) during the motion. Then the drive halts at the reached position as set in bRegulatorOn. The axis remains in the stopping state until the QuickStop mechanism is active (bDriveStart input = FALSE). if the drive has been moved previously by a function block, then it displays CommandAborted. This does not apply to the MC_Stop function block which reports an error and sets the axes to the errorstop state.
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If the drive supports it, then the variable eBrakeControl can be set or reset by means of the SMC3_BrakeControl function block. Three different modes are possible.
SMC3_BrakeSetState
SMC_BRAKE_AUTO: The state of the brake is controlled by the drive.
SMC_BRAKE_OPEN: The brake is open.
SMC_BRAKE_CLOSE: The brake is closed.
The variable bBrakeClosedRealState reports the current status of the brake.
From the point of view of SoftMotion, the control, as well as the state of the mechanical brake, does not depend on the state of the drive or the running motion.
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With the SMC_SetControllerMode function block, you can switch between the different control modes. The parameters byControllerMode and byRealControllerMode from AXIS_REF_SM3 represent the necessary and the current state of the controller.
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SMC_nocontrol |
Not a valid controller mode |
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SMC_torque |
Torque/force control |
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SMC_velocity |
Velocity control |
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SMC_position, |
Position control |
After writing the byControllerMode variables, the current state is checked until it agrees with the necessary control mode.
In the meantime, the POU calculates the specified value for the axis for example when changing the control mode. Then it sets its output bDone to TRUE. As of this time, it does not prepare any more specified values for the axis. This has to be done by other function blocks. Example: The output bDone triggers a function block MC_MoveVelocity, MC_MoveAbsolute, or MC_Halt. Otherwise the axis stops immediately after changing the control mode.
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In SoftMotion, you can reference a drive in two ways:
Referencing by a controller in the PLC: This referencing is performed by calling the SMC_Homing function block. The reference signal must be part of the I/O mapping of the controller. At the time of referencing, the drive remains in control mode "position control". In general, this method is not particularly accurate because detecting the position (when the reference switch is activated) is based on the current positions obtained by the drive. As a result, the accuracy is limited by the communication cycle.
Referencing by a controller in the drive: The reference switch is wired to the drive. Its position is detected faster and with higher accuracy. During the drive-controlled reference path, the drive is in another control mode, in which the drive is controlled by internal processes and does not follow the set values of the controller. When the reference path ends, the drive is reset to its original control mode.
The MC_Home function block starts the drive-controlled reference path by setting fReference and bStartReference. In addition, the state of AXIS_REF_SM3 (wState) is set to homing. When the drive passes to the reference path (meaning that it no longer follows the values specified by the controller), the drive sets the parameter to TRUE. To display the end of the reference path, the driver sets the values of bStartReference and bStartReferenceRealState to FALSE.
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You can detect the position of an axis in many ways, depending on the drive functions that the drive supports:
The drive detects the axis position itself (integrated or by switching on an external sensor). Because the actual position is transferred by the drive itself, the transfer time of the signal is minimal and precise.
The current position of the axis is determined independent of the drive and transferred to the controller via an input. Occurring latency of the controller input and the application cycle make this method less precise. When the position of the drive itself is transferred, it is processed directly in the application typically by the respective driver depending on the manufacturer. To determine the position of this kind of axis, you can use the MC_TouchProbe function block. It allows for the recording of the axis position to a configurable trigger and within a position window. If the position is not transferred by the drive, then it has to be passed to the drive driver, for example for control. Refer to the section "Position control on the PLC SM_Drive_PosControl".
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