Re: Orocos program

On Monday 03 May 2004 12:09, Andrea Consonni wrote:
> Hi,
> we have some questions about the command dataobject and orocos program.
>
> We are trying to understand how to give a command in an orocos program.
> We have had a look at your example "program-state" and, if we have
> understood right, you want that we create a real trajectory in the
> oro_main, write it in the command dataobject and, in the orocos program
> "program.ops", load the trajectory through the command "do
> CartesianGenerator.loadTrajectory()". Our question is: if we  want to write
> in the command dataobject from an orocos program, how can we do?

This is a good question again :-). There were some unclear semantics about the 
command dataobject in the past. The problem is that discrete commands like 
'moveto', 'wait' etc are not suited for data objects. These should be 
commands from the programscript (or HMI) and not passed through a dataobject. 
DataObjects are only for data flow, for example if the generator must 
interpolate between points given in the command DataObject, which were 
calculated in a higher level control loop. In this way, the 
CartesianComponent's examples violate this 'protocol' since it gives a 
trajectory command through the dataobject and not through a method call. 
Another conclusion is that the Command Dataobject is only usefull for 
cascaded control kernels.

>
> As test, we have written an our component "MyComponent" which has a method
> "MoveTo" which writes an double parameter in the command dataobject.
> Besides, we have exported this method to the Orocos Parser. In our orocos
> program we have written:

We were working on such a component too for moveTo(frame, time)
(CartesianNSGenerator).

>
> program {
>    var double par = XX
>    do MyComponent.MoveTo(par)
> }

Is this double the setpoint ?

>
> and everything is all right.
>
> However, we have two problems:
> 1) We have to pass to the component "MyComponent" a kernel* parameter so
> we can give the instruction "kernel->getCommand()->Set(command)", but we
> think this is not good. How can we do in other way?

What we do is :

program  {
	var frame endpos = frame( vector(x,y,z), rotation(x,y,z) )
	var double time = 10.0;
	do CartesianGenerator.moveTo( endpos, time )
}

Where the moveTo method of the generator prepares a new trajectory and the 
generator starts interpolating from the current position to the endpos and 
writes the result in the setpoints dataobject.

>
> 2) We want to pass to the method "MoveTo" more than one parameter, but,
> if we export this, we have some compile errors. Why?

We support up to three parameters. It is possible that in 0.12, there was 
still a bug in the parser framework which did not allow this. The next 
release guarantees 1,2 and 3 parameters to work. If you are familiar with the 
subversion tree, you can just check out the execution directory again. If you 
use the packages, I have added a package (labeled 0.13.99) which contains the 
upgraded parser on 
<http://people.mech.kuleuven.ac.be/~psoetens/orocos-packages/execution-0.13.99.epk>

Points I want to solve before the next release :
* selectComponent() semantics (discussion on orocos-dev)
* axis_control example must work, which demonstrates a control kernel for axis 
position control.

with kind regards,
Peter

-- 
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Peter Soetens, Research Assistent                  http://www.orocos.org
Katholieke Universiteit Leuven
Division Production Engineering,                      tel. +32 16 322773
Machine Design and Automation                         fax. +32 16 322987
Celestijnenlaan 300B                   [email protected]
B-3001 Leuven Belgium                 http://www.mech.kuleuven.ac.be/pma
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