OpenSML

Open Sources SoftMotion Light For CiA402 Servo Drivers

Tips:
Library file should worked on CODESYS and TwinCAT3, Quadratic velocity ramp calc we used Struckig Library.

There is suggest to read keba servoone usermanual to get more information about cia402.
Also i suggest that use Absolute Encoder, You don't need do reference travel at every start.
And if you have any questions please feel free to push your issues.

Why

Codesys is the best PLC programming platform. With the Raspberry Pi, you can get an advanced plc programming environment at a very low price. However, the softmotion license was canceled in the latest version of codesys for raspberry pi. (> 3.5.14.40, which means Raspberry Pi 4 must pay to get a softmotion license)

The motion control used by most customers is very simple and does not involve interpolation motion.

This project aims to provide the open source cia402 motion library for codesys or twincat users.

Target

In theory, an interpolation procedure can be made, similar to CNC. I am still working hard for this, but time is not guaranteed.

How

I only use ST (Struct text language) programming and add as many comments as possible.

Example for MC_Power:

Power_X(Axis:=Axis_X,xEnable:=Enable);

Example for Home And Absolute Position Move:

CASE iState OF
	0:
		Power_X(Axis:=Axis_X,xEnable:=xStart);
		IF Power_X.xDone THEN
			iState:=10;
		END_IF;
	10:
		Home_X(Axis:=Axis_X , xEnable:=xHomeEnable);
		IF Home_X.xDone THEN
			iState:=20;
		END_IF
	20:
		ProfilePosition_X(
			Axis:=Axis_X , 
			xEnable:=xMoveEnable , 
			xExecute:=xMoveExecute , 
			xContinueMove:=FALSE , 
			xRelativeMode:=FALSE , 
			diTargetPosition:=diTarget , 
			udiProfileVelocity:=udiVel);
END_CASE

Example for Cyclic Synchronous Position Mode:

Power_X(Axis:=Axis_X,xEnable:=Enable);
SyncPosition_X(
	Axis:=Axis_X , 
	MaxVelocity:=2000 , 
	MaxAcceleration:=20000 , 
	MaxJerk:=200000 , 
	CycleTime:=0.001 , 
	TargetPosition:=rTarget , 
	xEnable:=TRUE , 
	lrScale:=1.0 , 
	xSimulation:=TRUE,
	xError=> );

TODO

FuncBlock	Status	Name
Struct	✅	OpenSML_Axis
Power	✅	OpenSML_Power
Reset	✅	(use OpenSML_Power)
Home	✅	OpenSML_Home
Halt	✅	OpenSML_Stop
MoveAbsolute	✅	OpenSML_ProfilePosition
MoveVelocity	✅	OpenSML_ProfileVelocity
MoveRelative	✅	OpenSML_ProfilePosition
Stop	✅	OpenSML_Stop
Jog	🚧	-
TouchProbe	🚧	-
Cyclic Synchronous Velocity Mode	✅	OpenSML_SyncVelocity
Cyclic Synchronous Position Mode	✅	OpenSML_SyncPosition

Velocity Ramp

Quadratic velocity ramp calculate is very, very, very difficulty. Its simple when calc a curve, but its complexable when break a move without speed jitter.

I had create a 6th velocity ramp base g2 at #4 (comment) , But it cannot break a move. This is unacceptable for most applications.

Struckig and Ruckig is for multi dof robot calc, Ruckig calculates a trajectory to a target waypoint (with position, velocity, and acceleration) starting from any initial state limited by velocity, acceleration, and jerk constraints. It already finish mostily job in CSP moveabsolute. Also..it have a little bug, when i use Struckig, sometime it get non-zero acceleration when finished, it wll cause exception move. I had remove some funcition, reduce program size and make it work with OpenSML. For now its still in test, If you found some bug please push your issues. Thanks.

At this trace,

1. POU.otg.CurrentPosition from struckig.
2. POU.Axis1.fSetPosition from SM3_Basic.
3. POU.csp.otg.CurrentPosition from OpenSML_SyncPosition.

They overlap perfectly, diff < 1e-8.

Overflow

PDO use DINT as TargetPosition, Range is -2147483648 ~ 2147483647. It could overflow. For Example:
A Servo Driver use 24bit encoder, its 16777216 pulse/rev(16#1000000). Normally Driver parameter will to be divided by 16(16#10), So its 1048576 pulse/rev(16#100000) for EtherCAT PDO(TargetPosition). If we use pitch=5mm ball screw, its 209715.2 pulse/mm.

So, if we dont want overflow, The position range is -10240 ~ 10239mm.
Overflow will automatic sum at some servo driver. so driver can accept overflow. But, if overflow happend, and OpenSML_SyncPosition FunctionBlock xEnable drop down, we cannot know how many overflow happend. When xEnable up, Actual position not equal OpenSML_SyncPosition feedback. It could make some exception move.

If you need a large move range, make sure not overflow. Also, Some servo driver cannot accept overflow.